Collimatrix

[title image]
 
Hollow charges and armor protection - their alternating progression
 
The term "hollow charges", which is commonly used in German, is not very accurate for the explosives so called. The somewhat more general American term "shaped charge" is a better description of the measures necessary to achieve the desired effects with these charges. Apart from the explosives used by glider pilots at Fort Emeal, it is of great importance for the vast majority of the extensive and versatile range of applications of shaped charges developed since the Second World War that their suitably shaped surface is covered with a layer of inert materials, preferably metals.  The individual elements of the liner are accelerated to velocities of several km/sec and, through special selection of the initial shape and dimensions, it is possible to transform these liner bodies into projectile-like structures which are best suited to combat the respective target.
This possibility of adapting the effector to the structure of the target to be engaged is very important for the use of hollow charges, but the application potential of these charges, given their early and impulsive nature, is far from exhausted by what has been developed in this field so far. This is particularly true when it comes to combating targets whose design is already tailored to protect against the known hollow charges.
This will be explained in more detail below; in addition, examples will be used to illustrate the many different ways in which explosives can be used to obtain targeted effects and counteractions.
 
The effect of explosive devices attached to armour panels - the "spalling effect"
 
In most cases of using detonating explosives, the energy released by the detonation is transferred to inert materials. In the case of armour plates on which explosives are detonated, the direct effect is relatively small. Although the detonation pressure exceeds the strength of the armour material many times over, the material goes into a state of fluidity and is slightly pressed in at the surface - something similar happens when damp clay is pressed. The depressions that occur are small because the time during which the detonation pressure is sustained and the material is in a flowing state is very short. This only lasts until the relaxation of the highly compressed explosive decomposition products towards the free surface of the detonator has taken place. If, for example, an explosive layer of 2 cm thickness is placed on an armour plate, the impact time on a surface element of the plate during detonation is about 2/800000 sec, i.e. 2.5 µsec. During this time only a slight displacement of the plate material can occur. The example of an explosive layer applied to the surface of an armour plate and detonated there is also suitable for explaining a phenomenon that is very important and is referred to several times in the context of the present comments:
 
[Figure 1]
 
Under certain conditions, material parts detach from the rear side of the armour plate and are propelled at quite high speed into the space behind the plate. This so-called " spalling effect " occurs whenever a limited area in a body, where the material is under very high pressure, reaches a free surface of the body (see figure 1). There, the material parts compressed under high pressure relax and advance perpendicular to the surface. The relaxation is thus associated with acceleration. While the relaxation spreads into the interior of the pressure area, all material parts that have been compressed by it are accelerated. If the relaxation wave reaches the rear end of the pressure area, i.e. the zone in which the material particles are not compressed and therefore remain at rest, the parts that have been set in motion by the relaxation break off at this point and continue their motion only outside, provided that the tensile stress that occurs exceeds the tensile strength of the material.
In the case of the spalling effect, one observes a separation of disc-shaped plate parts on the back of an armour plate exactly opposite the surface covered by the explosive on the upper side (see also Figure 15). This surface must not be less than a certain size, because the accelerated, spalling parts must not only overcome the tensile strength of the detachment from the inner plate parts, which remain at rest, but also the shear stresses at the edge of the spalling plate. In general, this is only then the case when the diameter of the overlying explosive layer exceeds the thickness of the armour plate, otherwise a " bulge" appears on the underside of the plate.
The effect of the " squash head " projectiles is based on this spalling effect. The explosive in the bullet cap is released when the projectiles impact on of the armour plate is spread and then detonated. 1)
 
The effect of unshaped, uncontained explosive charges in the free atmosphere

If an uninsulated explosive device is detonated in the open atmosphere without any special design or arrangement, its effect is relatively small at a distance from the source of detonation. Although the pressure behind the detonation front, which in modern explosives can reach speeds of is advancing at about 8 km/sec, is quite high. It is in the order of several hundred thousand atmospheres, but it rapidly decays as it spreads in all directions, distributing energy and momentum over areas that grow quadratically with distance.
By contrast, special arrangements, which should be mentioned here because they are to a certain extent related to hollow charges, can be used to achieve a sufficient pressure effect even with unshaped, unchecked explosive charges at greater distances, for example against flying targets.  If, for example explosive charges are arranged at the corners of a regular polygon and detonated simultaneously, a very effective superimposition of the pressure occurs on the axis of symmetry of the arrangement at distances of up to several diameters of the polygon - in the so-called Mach area. Towards the end of the Second World War, the possibility of using such charge arrangements from the ground against enemy aircraft flying in pulks had been considered. In model tests with 6 charges of 50 kg trinitrotoluene (TNT) each, regularly distributed on a circle of 100 m diameter, a pressure of about ~15 bar was measured 350 m above the ground in the vicinity of the axis of symmetry.
 
Protective effect of multilayer armour

In order to be protected against the spalling effect of squashing head projectiles and similarly acting warheads, it is advisable to provide armour which consists of at least two layers with a gap between them. For this reason alone, the development of anti-tank ammunition was therefore based on paying special attention to multilayered armour. The requirement for penetration of structured armour with air gaps is also indispensable in other respects. The same conditions apply, for example, when an armour is hit by a plate covering the running gear or by a "skirt" attached to the running gear. In the case of more or less abrupt impact, the point at which the ignition of a shaped charge warhead takes place can then be up to several metres away from the point at which its main effect should begin. In addition to standard single-layer targets, the testing of hollow-charge ammunition therefore includes targets consisting of several plates spaced at certain distances from each other (see Figure 2).
 
[Figure 2]
 
In principle, the mode of action of hollow charges meets the above-mentioned requirements very well, much better than is the case with conventional impact projectiles. When a kinetic projectile hits a armour surface, a high pressure is created in both the armour material and the projectile. Starting at the tip, a pressure condition is built up in the bullet, which leads to the phenomenon described earlier in the treatment of the spalling effect on the free surface of the bullet. Tensile stresses occur which begin to tear the bullet body before it has penetrated the target surface. They can cause the bullet to disintegrate into individual parts after penetrating the first plate, which are then stopped by a second plate of a multilayer target (see Figure 3 a and b).
 
[Figure 3]
 
If, on the other hand, hollow charges with a lined cavity are detonated on the target surface, the so-called hollow charge jet is generated, which is sometimes called a "spike" because it is initially coherent and usually occurs in a solid state. With the hollow charges commonly used today, the jet disintegrates as it advances into a series of small - often spindle-shaped - very fast projectiles, whose frontal velocities can reach about 10 km/sec; the last ones still achieve about 2 km/sec. When the first particle hits the surface of the shell, a pressure in the order of 1 million atmospheres is created there; the shell material begins to flow and an approximately tulip-shaped crater is formed, similar to the penetration of a body of high velocity into water. The volume occupied by the crater is released by displacing the armour material towards the free surface. When the second jet particle hits the bottom of the crater, repeat the process, as well as the impact of the following particles. Each particle continues the displacement of the target material where the previous one stopped until schliefilich creates a channel of penetration through the whole plate.
The flow of the material particles associated with the displacement of the target material ends at the free surface. Partly at the upper side, partly at the lower side of the armour plate and partly also at the already created penetration channel, which is subsequently narrowed again slightly.
 
The following jet particles not consumed during penetration continue their path after passing through the penetration channel and act on obstacles that are on their path. If they hit another armoured plate, they can continue the penetration process there undisturbed.
In contrast to the behaviour of the compact kinetic projectile, the individual elements act on the armour one after the other, independently of each other, and it does not seem so important at first whether the armour is massive or in separate parts, because a disturbance at the tip of the projectile does not affect the following parts.
Nevertheless, the so-called "bulkhead armour", in which a number of thinner armour plates are arranged with air gaps between them, also provides increased protection against hollow charges: The penetration channel created by the impact of the particles of the hollow-charge projectile is relatively narrow and is of the same order of magnitude as the plate thickness when using thinner plates of the bulkhead armour. When the hollow-charge particles strike these thin plates, the hole in the plate is created essentially by the fact that the material elements of the plate which are caught by the high dynamic pressure are forced away from the plate under the influence of the tensile stress acting perpendicularly to the free surface, both on the upper and the lower side of the plate. The penetration channel therefore runs almost perpendicular to the plate surface, regardless of whether the hollow charge particles generating the pressure impact obliquely or vertically. The tensile stresses induced at the plate surface as a result of the dynamic pressure are in any case perpendicular to the plate and also have an effect in this direction (see Figure 4).
 
[Figure 4]
 
If now diagonally incident subsequent particles reach the previously created penetration channel running approximately perpendicular to the surface, they find a much reduced cross-section for their passage compared to the vertical incidence (see Figure 5). There is thus an increased probability that they will come into contact with the wall as a result of path variations, as a result of which their contribution to the penetration performance is lost. The affected particle disintegrates explosively, since - as described above - the high pressure occurring during wall contact induces tensile stresses on the free surface of the particle, causing it to burst. In Figure 6, a TRW image converter camera is used to illustrate how a steel ball of 2 mm diameter is sprayed after it has penetrated a very thin plastic film at very high speed. Figure 7 shows the piece of a hollow charge jet in which a similar burst was triggered on a particle by touching the wall. As can be seen from the figure, the small debris of the disintegrated particle spreads sideways to the direction of the beam, apparently away from the wall that was touched. It is important that the propagation of these fragments into the free space behind the plate is possible. At massive targets this free space is not available, the particle splinters would be held together and their impulse could contribute to the penetration even if the particle had touched the wall before. That's why it's important, armoured plates and air gaps of certain thickness should follow each other.
 
[Figure 5, figure 6 and figure 7]

This leads to bulkhead arrangements which, when hitting the wall at an angle, cancel out the effects of a high portion of the hollow charge jet due to the increased probability of the jet particles touching the wall and their subsequent disintegration into the gap. The weight of the armour required for this, in relation to the unit area, is considerably less than in the case of solid armour. It is essential that this provides increased base protection against both balancing projectiles and shaped-charge ammunition, and it is noteworthy that this effect occurs in both cases by inducing the decay phenomenon on impact at high velocity. However, in the case of a balancing projectile, the entire mass of the energy carrier is captured by the destructive tension waves on first impact, whereas in the case of a hollow-charge jet only the mass portion corresponding to the respective impacting jet particles is captured.
 
Measures to avoid disturbance of the shaped charge jet

However, it is not clear why rear particles of the hollow charge jet must necessarily come into contact with wall elements of the penetration channel created by the previous ones. Should it not be much more possible to ensure that the particles
aligned very cleanly and without "staggering" movement exactly on the cavity axis? However, this means that the slightest deviations from central symmetry must be avoided in the structure of the hollow charge. The whole rigor of this requirement is that it relates not only to the dimensions of the charge, but also includes the homogeneity of the materials used and that - as has already been shown - even differences in the size and orientation of the crystals in the explosive and in the copper of the liner have an influence. This requirement is even more stringent if one takes into account that the properties of the crystals mentioned above change over time, i.e. as they age, and that changes are also triggered during processing. A very sensitive influence can also be expected from the way the detonation is initiated.
With the aforementioned and similar requirements with regard to precision, the production of hollow charges has set goals whose pursuit in the past has already brought about significant progress with regard to the generation of an undisturbed hollow charge jet during detonation, and in the future, through the tireless efforts of research and technology, even further perfection can be expected. In addition to this somewhat utopian-looking reference, however, it must be emphasized that the hollow charge principle is very flexible and includes a wealth of other possibilities for counteracting disturbances which oppose the effective targeted use of the explosive energy released during detonation. For example, it is not necessary for the hollow charge jet to dissolve into a number of particles as it progresses. Some of the irregularities in the behaviour of the particles will only develop during the tear-off process and can be avoided if the hollow charge jet is constructed in such a way that it does not tear.
The reason for the dissolution of the hollow charge jet into a number of particles of different velocities is that the individual jet elements already have a different velocity when they are formed. In the case of the hollow charges currently in use, there is a velocity gradient in the beam from about 8-10 km at the tip to about 2 km at the end.The consequence is that the jet is constantly stretched as it progresses and eventually dissolves into more or less parts according to the strength properties of the material .2)
 
 
The programmed shaped charge jet

By special selection of the parameters of a hollow charge (type and density of the explosive, dimensions and shape of the cavity, wall thickness and material of the cavity lining, shape as well as wall thickness and material of the casing, position and extension of the ignition elements) it can be achieved that differences in the velocity of the individual elements of the jet are prevented at all.
The relationship between the distribution of mass and velocity in the jet and the charge parameters was already known shortly after the discovery of the
the lining of the cavity achievable effect by Thomanek quite detailed results. 3)
This connection is achieved by following each individual sub-process during the detonation of the charge and the deformation of the liner by calculation. When the detonation front reaches the individual zones of the liner body, the material there enters a state of flow under the influence of the detonation pressure and is accelerated inwards. The speed at which the lining elements are accelerated depends on how long the pressure remains at the zone under consideration or, which comes to the same effect as how far the outer surface of the detonator is from this point. Thus, the influence of the width of the explosive coating on the velocity of a panel is obtained.
For example, consider a cylindrical charge with a cone as a cavity and a diameter of 8 cm. The time required for the dilution wave to reach the top of the cone from the outer surface is then 4 cm/approx. 800000 cm/sec, i.e. approx. 5 microseconds; in the central zones of the cone with an explosive coating of 2 cm, this time is only half as long and the impulse transmitted to the lining elements by the detonation pressure in this time is therefore half as large.
Of course, the speed also depends on the wall thickness of the lining body at this point and the density of the lining material.  The initial velocity of the lining elements can be specifically influenced by a suitable choice of the wall thickness and it can change at will between the tip and base of the lining cone. One speaks of "progressive" or "degressive" liners, depending on whether the wall thickness increases or decreases towards the base. The influence of the liner's wall thickness/explosive coverage ratio then has a further effect on the jet elements that are emitted when the liner zone converges on the cavity axis. In addition, the mass and velocity of the jet elements formed depend on the angle at which the convergence takes place, i.e. the opening angle of the cavity. Peak angles result in high velocities for small masses, and the opposite is true for obtuse angles.
The previous remarks should serve to explain, at least by way of indication, how it is possible to determine the dependence of the distribution of mass and velocity in the jet on the charge parameters. With the knowledge of these interrelationships, it now seems possible to create projectile-like structures from the cladding bodies, in which the initial length and the distribution of mass and velocity over this length are predetermined, i.e. the hollow charge jet can be programmed.
 
Up to now, almost all attempts have been made to obtain a jet with the greatest possible penetration capacity. This led to the familiar design forms: cylindrical on the outside, cavity for example 60° cone with copper liner, initiation of the detonation now often by detonation wave deflection at the rear edge of the detonator, whereby better use of the explosive volume and higher beam tip velocities are achieved (compare also Figure 16). The resulting beam is then a constantly stretched structure with a velocity of up to 10 km/sec at the tip and about 2 km/sec at the end, which is followed more slowly by the rest of the cladding mass, the so-called "slug". 4)
As already mentioned several times, the differences in the velocity of the individual beam elements cause the initially coherent structure to be broken up into a sequence of particles. Nevertheless, very good results have been achieved with the described type of charges, especially against massive targets.
Penetration depths of up to 6 charge diameters have been achieved. In contrast, when using targets with air gaps, the distance travelled in the massive parts of the target is greatly reduced. In the future, requirements for the performance of hollow-charge ammunition should be geared to these reduced amounts; this would mean that modern hollow charges should be developed to penetrate structured targets rather than exaggerated penetration performance in massive targets. An attempt should be made to program the hollow-charge jet, i.e. to adapt it to the structure of the target.
In the following we will try to explain by means of examples that there are many possibilities to modify the beam of the currently used hollow charge.

A completely different motion sequence of the particles of the beam from this type of charge can be obtained by replacing the centrally symmetrical ignition by a (one-sided) eccentric one.The individual beam particles then no longer move one behind the other on the cavity axis, their paths point in a fan-like manner in different directions (compare Figures 8a and b) 5) The following example is intended to show how even a slight change in the cavity shape can noticeably influence the beam and its effect.  Figure 9a shows a cladding body whose shape can be roughly described as a cone which ends at the base in a spherical zone. Figure 9b shows the penetration channel of an externally cylindrical charge produced using this liner.
 
[Figure 8 and figure 9]
 
The explanation for the peculiar shape results from the velocity distribution in the hollow jet. The front part of the jet comes from the cone-shaped part of the cavity and corresponds to the jet from a cone, which stretches as it advances. For the subsequent jet elements, which originate from the spherical zones at the base, it is decisive that the tangent at the cavity becomes steeper and steeper towards the base. The consequence is that the successive jet elements become faster and faster towards the rear, thus approaching each other and leading to a thickening of the jet in this rear area. On impact, the effect is increased in the form of a widening of the penetration channel.
While with the hollow charge described above, a concentration of energy occurs in the rear jet section, it is also possible to achieve this in the front jet section. For this purpose, the cavity must be spherical at the apex and end in a cone at the base (see Figures 10a and b). The penetration channel is wide at the top and has the shape of a hemisphere followed by a narrow conical part. 6)
If the cavity, which is essentially delimited by a cone, is spherical at both the apex and the base, the penetration channel will consist of a wide part at the armour surface, followed by a narrow conical part and a further widening at the end. Following these examples, it should be considered possible that the effectiveness of the individual sections of the hollow charge jet can be determined in quite a different way, especially if it is taken into account that other parameters of the hollow charges can also contribute to this by their specific choice.
 
[Figure 10]
 
As explained in the previous section, other velocity distributions are possible in addition to the velocity gradient in the jet of the commonly used hollow charges that leads to rupture. It is also possible to achieve that all beam elements have the same velocity, provided that the relevant charge parameters are adjusted to it in each zone of the cavity. If, for example, the wall thickness of the cladding is selected in such a way that it is in the same ratio to the corresponding width of the explosive coating for all zones, the cladding elements of all zones receive the same initial velocity on detonation and thus also all the beam elements that are separated from them when flowing together on the cavity axis.
As a result, the jet is represented here by an "overlong projectile" with a rather high velocity. A sketch of the principle of such a charge is shown in Figure 11. The nozzle-shaped body attached to the base has the purpose of preventing the decomposition by-products from coming into direct contact with the free atmosphere when the base zone is accelerated, thus avoiding a premature drop in pressure. In a similar way, other causes of disturbance are to be avoided, whereby a number of experiments are always necessary before a principle path can be realized.
 
[Figure 11]

Instead of a single rod-like projectile, a sequence of several such rods can be obtained in which the individual elements have the same velocity, with the velocity of the rods differing from each other.
In addition, from the special solution of the identical velocity of all beam elements, transitions to the common hollow charge with the large velocity gradient in the beam can also be developed. In particular, the case can also be realized in which the difference in the velocity of the following beam elements is so small that the beam is only broken when all obstacles of the target have been overcome. How such a continuous beam reacts to protective measures that disturb a particle-dissolved jet is still to be investigated. In any case, the disturbances caused by the rupture process are avoided here (compare Figure 12).
 
[Figure 12]

Also, the range of possible variations in the structure of the shaped charge jet is so wide that an adaptation to very different target compositions seems possible. Not insignificant is the fact that the energy of the effect carriers from a hollow charge can be distributed in a targeted manner to mass and velocity, i.e. the jet can obtain a greater mass at the expense of the velocity of its elements and vice versa.
As investigations have shown, the protective effect of certain materials depends on the speed of the projectiles. 7) However, such measures need not refer to the entire jet, but can be limited to parts of it, for example to the front or rear parts of the target.
A special group of shaped charges has not been mentioned so far, namely those with a flat, especially blunt conical cavity. ln contrast to the pointed conical cavity, the attainable velocities are lower here. The speed of the structure previously referred to as the jet is no longer very different from that of the so-called following slug. It can be achieved by methods which will not be discussed in detail here, that the jet and slug components - i.e. the entire mass of the liner - merge into an at least temporarily coherent structure. lf the difference in the speeds of the front and rear parts is sufficiently small, it is absorbed by internal expansion work, and a projectile with a uniform speed of about 2000 m/sec is created. Figure 13 shows a series of such projectiles from charges with a flat cavity, using X-ray flash images.
 
Figure 14 shows a section through a captured specimen of cohesive projectiles. Such projectiles are particularly characterized by stable flight at long distances and have already found 'a versatile application today, especially as a replacement for natural fragments (see also cover picture and Figure 15).
 
[Figure 13, figure 14 and figure15]
 
In connection with the efforts to combat future targets, which may be unknown at present, it should be mentioned that it is possible and possibly very useful to arrange projectile-forming hollow charges in a special way one behind the other. If this is done taking into account all the side effects of the detonation, and if such an arrangement is ignited appropriately, one obtains a sequence of projectiles flying one behind the other at fairly high speed, the mass of which is considerably greater than that of particles of the hollow charge jet.
It is also possible to combine a projectile-forming charge with a jet-forming charge with an acute-angled cavity. Figure 16 shows such a charge, also known as "tandem charge".
It was designed to create a strong follow-on effect inside the tank. On detonation, the jet from the rear charge penetrates through an opening in the apex of the front flat-cone charge. Only after this has been done is this charge also detonated; the flat liner body is formed into a projectile which follows the jet from the rear charge through the channel created by it and comes into effect there depending on the intended purpose.
 
[Figure 16]
 
These examples are intended to show that there are almost no limits to the imagination when it comes to exploiting the potential inherent in the principle of forming effective projectiles by transferring explosive energy to inert materials. There are many ways to develop explosive charges that can be effective against complex targets and do not necessarily require a gun to reach the target, but can be used in warheads of missiles. Of course, there will always be possibilities to achieve sufficient protection by suitably constructed armour. What should be particularly emphasized here, however, is the view that there is hardly likely to be a miracle cure for all types of shaped charges and that, apart from a temporary predominance on one side or the other, there will probably continue to be mutual efforts to perfect shaped charges on the one hand and protective armour on the other.
 

https://andrei-bt.livejournal.com/1372167.html
Serbian ERO-19

We discussed this a bit on teamspeak.  Military reformists went from Boyd's theory of specific excess power, which is a simplistic but still fairly sophisticated description of fighter maneuverability, to complete nonsense like saying that wing loading is the only important factor in fighter maneuverability.
 
Which is why the Mirage 3 can stomp an F-16 in DACT.  Oh wait, no, that's completely backwards.  It turns out that things like parasite drag, wingtip vortex losses, non-linear lift interactions and static margin matter.  It's almost like fluid dynamics is complicated, and simplifying your mathematical models of complicated phenomena will make them correspond less to reality.
 
But if influence and fame and a spot on CNN is what you crave, you can't get it by taking something like specific excess power on the road.  You've got to dumb down your message so that the filthy ignorant dirt peasants who watch that crap will understand.
 
So you simplify your original concepts to the point of meaninglessness.  Computer simulations useless for design tradeoffs?  How does this cretin think gas turbine engines are designed?  Oh, that's right; this is the same person who said that increasing turbine inlet temperatures just makes engines more expensive and doesn't improve their performance.  Screw thermodynamics! What has thermodynamics ever done for us?
 
Which is the final point of the descent of the military reformists; when all else fails, just lie.  How many absurd howlers are there in that presentation?  The M1 can't depress its machine guns?  They're coaxial, same as the M48!  The A-10 has a 30mm cannon, but the F-15E is only capable of carrying four maverick missiles?  M48 and M1 have the same battlesight accuracy?  Maybe in terms of mechanical dispersion, but "battlesight accuracy" means firing without the use of rangefinders, and the much greater MV of M829 would be very telling.  M1 more flammable than M48?  Jet fuel is substantially less flammable than gasoline, because it's very nearly the same thing as diesel.

If a small arms range advantage is going to matter, it would matter in defensive engagements.
 
There are a few stories from the Boer War where the Boers knew where the British would attack, and could arrange their defenses accordingly.  They even went so far as to place large, white rocks at 100 yard intervals so range estimation could be done faster and better.
 
Somehow this wasn't a dead giveaway to the British that it was a prepared position they were attacking frontally.  Too many years of fighting people armed with dried grass.

https://warspot.ru/17005-teoriya-bronetankovyh-zabluzhdeniy-tanki-v-chistom-pole-i-amerikanskie-stanki
   Yuri Pasholok's article about some of myths about Soviet armor (1943-1944).
 
   1. Turret ring diamter increase problems
 

    Translation of text:
   Is there an ability to increase turret ring of T-34 tank? Yes, they are. According to preliminary assesment ring can be made wider by 200mm.
   Is it possible for production to make it? Yes, Mariupol factory doesn't have any problems with it, factory N183 also have necessary machinery
 
 
 

   T-34-85 with 1600mm turret ring instead of 1430 during testing.
 
 
 
   2. SU-76M is bad
 

   Manual river crossing of the ZIS-3 cannon. Those wishing to tell that the SU-76M was a bad self-propelled gun can mentally send themselves to the place of one of the numbers of this crew
 
 

 
 
 
   3. About ISU-122 existance: myth and reality.
 

   The main reason for the appearance of the A-19 as a weapon for tanks and self-propelled guns. The demolished Tiger turret is the result of an A-19 armor-piercing shell hit from a 1.5 km
 
 

 
 

   Thanks to the ISU-122s, it was possible to reduce the requirements for the production of A-19 for self-propelled guns to 100 pieces per month. Nevertheless, the cases when the plant No. 172 did not keep up with the orders are not rare.
 
 
 
   4. About IS tanks
 

   To the question of when the D-25 was created. The middle of July 1943, and there is already a project of Object 240. The fighting on the Kursk Bulge is still ongoing
 
 

   Distance - 2000m. R50 (half of shots) - 72sm, R100 - 130 sm. "+" is point of aim, central part of the group is 10 sm above and 100sm to the right from point of aim.
   To the question of the accuracy of the D-25T. And such accuracy was achieved during standard warranty tests.
 
 

   One of the tanks that participated in the battle of Ternopol. The vehicle was hit, but, as you can see, served in the Red and Soviet armies for more than a decade
 
 

   In August 1944, the mass production of the IS-2 began with a straightened frontal part of the hull, which was significantly stronger than the original design
 
 
/..../
   6. Optics
 

   Visibility from T-34-85. During the war years, Soviet observation devices and sights made a big step forward
 
 

   For comparison, the visibility from the Panther. Loader is blind, the gunner looks only forward, only the commander can look on the sides. For this reason, defeats on the sides were a frequent result of the combat use of new generation of German tanks.
 
 

But the Southern USA doesn't have any similar bizarre sexual predilections.  I mean, they obviously have a reputation for being into whips and chains, but that is for entirely different reasons.

US supercarriers have modest point defense systems, but they are going to traveling as part of a strike group that contains at least one aegis cruiser.  Smaller navies which can only deploy smaller strike groups have thicker defenses mounted on the carriers themselves.  INS Vikrant has short and long range SAMs, 76mm autocannons and 30mm CWIS, for example.
 
The tradeoff is that the Nimitz/Gerald R. Ford class carriers utterly dwarf all other carriers in sortie generation rate.  The Nimitz class can surge to 230 sorties per day for four days and sustain 120 sorties per day for extended periods.  The Navy was initially optimistic that the Gerald R Ford class could manage a 33% increase in sortie generation rate, but some newer sources are saying that it will only manage a 25% increase, at least initially.
 
The surge rates for the Queen Elizabeth class and the Charles de Gaulle are something like 120/day and 100/day respectively.  So even going all out, the next biggest non-US carriers can't even match a Nimitz's sustained sortie generation rate, much less a Gerald R Ford's.  Kuznetsov and her kin are lower still.  Not sure about the new Vikrant.
 
There appears to be an economy of scale that heavily favors really big carriers.  The US supercarriers appear to roughly match the best of their smaller peers in terms of maximum sorties per day per tonne of displacement, and appear to pull far ahead in terms of sustainable sorties per day per tonne of displacement (the figures for the CDG's latest cruise in Syria are not flattering, 12/day or something).  On top of that, the US supercarriers are a few knots faster than all the other carriers.
 
In short, giant, nuclear-driven American firepower for the win.
 

Restricted: for Operating Thetan Eyes Only
 
By order of Her Gracious and Serene Majesty Queen Diane Feinstein the VIII
 
The Dianetic People’s Republic of California
 
Anno Domini 2256
 
SUBJ: New tank contract awards
 
OK, praise be to Hubbard the last prophet and Tom Cruise, his true successor and all that shit that the upper party members will want to see in an official document.  You want to know Hubbard's honest truth?  This entire heavy tank development program has been one big conga line of fuckups since day one.  There's a reason that we're still out there tanking with DF-1s, and that reason is the current government of the DPRC.  Their insane commitment to Scientology has made a mockery of every attempt to maintain a stable and sensible war economy.  Until the ruling regime is liquidated and replaced with a government based on the scientific principles of Euphoric Atheism, the disasters will only compound.


The military tribunal for tank procurement has selected Hakika si Kundi la Dudes Nyeupe (HKDN) design bureau's Object 426 "Stumpy" as the basis for the DPRC's next main battle tank.  In order to facilitate crew competence and speed the de-bugging phase on the way to IOC, the first several dozen vehicles will be sent to a special test unit.  This test unit will be kept separated from the rest of the DPRC military's logistical system and chain of command.  In order to prevent sabotage of the program by the circulation of false reports, the entire test unit and its activities will be kept secret, even from the members of the civilian government.  In order to prevent any theft of the technical secrets of the vehicles, the test unit will be given the authority to shut down all communications and transport networks in the DPRC at its sole discretion.
 
Congratulations, @Toxn

Oh, good.  So they were on the same page of arms design as the country that has fought literally nobody since 1847.

Let's all take a trip back to the late 1970s and early 1980s.  This was the time of punk.  This was the time of despair.
 
Punk was all about minimalism; strip everything down to a few chords, wear clothes you fished out of a garbage can or made yourself and infect yourself with parasitic worms so that when you vomited on some other asshole in a fight, they got parasitic worms too.  It wasn't pretty, but it was cheap and it worked.
 
Punk was about to hit pistol design in a big way.  The aglockalypse was just around the corner.  The glock is the practical application of punk to the art of small arms design.  It's reminiscent of John Browning's early striker-fired design prototypes for the hi-power, only made out of plastic and missing half the parts.  Not pretty, but cheap and it sure does work.
 
The world was very different in the punk era.  Remember that in the United States, violent crime increased dramatically in the late 1960s.  In the 1970s they were still figuring out what to do about that.  They hadn't had a few decades for the idea that gunfights were just something that might happen day to day to sink in, so the art of practical handgun usage was in a pretty sorry state.
 
Or rather, practical handgun knowledge was in a hilariously bad state at the time.  I read through a police marksmanship manual from the late 1960s or early 1970s; it's like an infantry tactics manual written pre-WWI.  It's heartbreakingly naive because they hadn't seriously had to seriously think about the problem before then.  They had come from a more peaceful world, and were still getting their bearings in the grimdark of the 20th century.
 
This police marksmanship manual still taught the FBI crouch.  The FBI crouch is a sort of distillation of the WWII-vintage Fairbairn-Sykes theory of gunfighting, which emphasized speed over accuracy.  The idea behind the FBI crouch is that you crouch down so that you're harder to hit, and you sort of get your dominant arm that's holding the weapon into a repeatable, ergonomically neutral alignment with the rest of your body so that you can aim with your entire body.  As you can see, this isn't a shooting stance that allows you to use the pistol's sights.  In some variants of the stance, you cross your left forearm over your torso so that incoming bullets have that much more flesh to go through before they start hitting your vital organs.
 
Basically, it's the sort of theory of how to gunfighting that you might come up with in a society that, until recently, hasn't been doing a whole lot of gunfighting.
 
Everything was in a more primitive state than it is now.  Nowadays you can go into a gunstore and have dozens of brands and styles of pistol ammunition to chose from; hollowpoints of all descriptions line the shelves, each promising to kill people more dead than the next one.  Oh, and you can buy full metal jacket if you need something cheap for practice.  Back then, full metal jacket was the fancy stuff; the most common ammo was cast lead.  Also, cops weren't totally sold on automatic pistols until about halfway through the '70s, they still mostly used revolvers.  Also, almost nobody owned a handgun.  It was considered weird.  Owning a rifle or a shotgun was perfectly normal; what else are you going to go hunting with?  Owning a handgun was weird because handguns are for shooting people, and why are you even thinking about shooting at people you weirdo?  The laws and court precedent for self-defense cases were a lot different then too.  Formerly peaceful society, still coming to grips with the grimdark.
 
So, secret about Beretta; they basically want to make hunting shotguns and make up-scale hunting apparel.  They can't design automatic firearms actions to save their lives.  Whenever they have to make something automatic they rely on Germans to design the things for them.  The AR-70, for instance, was originally a joint design effort with SIG (SIG's evolved into the SIG-540/550 series).  The ARX-160 was designed by Ulrich Zedrosser, who, as you might surmise from his name is not Italian.  The Beretta 92 is the last in a line of Beretta pistols that started off basically as clones of the Walther P-38.
 
You can imagine it; Beretta in the 1970s doesn't really know what makes an automatic pistol a superior combat piece, although they've been making clones of the Walther action long enough that they can make them work very well.  Cops don't know how to gunfight either; all they know is that these automatics seems a whole lot easier to shoot yourself with than revolvers, so they're going to need some sort of super-duper double safety device.  Some want double action with a decocker, some want a safety as well, someone want a combined safety decocker...
 
So Beretta shrugs their shoulders and tries to please all these cop agencies.  Obviously, they're mainly going to be selling these things to cops and military and a very small number of weirdos.
 
Meanwhile, Jeff Cooper, Jack Weaver and a small but growing number of practical pistol competition shooters are figuring out how to actually fight with a handgun.  Meanwhile, in Austria, long-standing armament maker Steyr is about to get a nasty surprise when the Austrian Army holds a competition for their next pistol.

I've been following this for a while:
 
http://www.dtic.mil/ndia/2002gun/kathe.pdf
 
http://www.dtic.mil/ndia/2007gun_missile/GMTueAM2/MinerPresentation.pdf
 
http://www.dtic.mil/ndia/2009gunmissile/katheEmertechtuesday.pdf
 
It's a remarkably good idea.
 
RAVEN a drastically improved design for a recoilless rifle.  In a traditional recoilless rifle, at the moment of ignition gas is free to exit the rear of the gun out of a De Laval nozzle:
 
 

 
 
If the thrust of gas going through the nozzle is close enough to the momentum of the gas and projectile exiting the muzzle, the weapon is recoilless or close enough to.  The problem is that this is hideously inefficient; most of the propellant mass is used to counteract projectile momentum instead of pushing the projectile.
 
In the RAVEN, the breech is closed to gas flow at the moment of firing:
 

 
But it is opened shortly afterward, while the projectile is still in-bore.  The wave cause by the sudden drop in pressure due to the breech vents opening cannot catch up with the projectile in time to affect it, so there is no velocity loss and the recoil reduction is essentially free.
 
Timing of the opening of the breech is most easily achieved by a blowback breech, IMO.  The acceleration of a delay mass should be extremely repeatable, and could easily give consistent timing.  The vent holes and nozzle will likely be consumable items, just as they are in traditional recoilless rifles.
 
Unlike traditional recoilless rifles, which are limited to low-to-medium velocities due to their inefficiency, RAVEN works better with high velocities, since the projectile will be moving a higher percentage of the speed of sound of the propellant gas, and so venting can occur earlier.  Furthermore, in high velocity weapons the momentum of the gas at the muzzle is a higher percentage of total recoil, so the percentage reduction of recoil will be higher.

Usually, reviewers see the movies they are reviewing.  I am too busy.
 
 
Avengers: Age of Ultron
 
This film is a re-imagining of the 1960s British spy-fi TV series.  In this gritty, noir take on the setting, an aged John Steed (Patrick Stewart) and Emma Peel (Judy Dench) have to contend with the looming specter of funding cuts and privatization.  Crass, commercial mega-corporation RonCo, headed by professional wrestler Ultimate Ron, have made a bid to buy up their agency.
 
This is a touching, poignant film with serious reflections on the role of the elderly in society.  In a refreshing departure from contemporary practice, the film had a completely satisfying finale that also completely obviates any speculation of a sequel.

What a Long, Strange Trip it's Been
 
PC gaming has been a hell of a ride.  I say "has been" both in the sense that exciting and dynamic things have happened, but also in the sense that the most exciting and dynamic times are behind us.  No other form of video gaming is as closely tied to the latest developments in personal computing hardware, and current trends do not suggest that anything dramatically new and exciting is immediately around the corner.  Indeed, fundamental aspects of semiconductor physics suggest that chip technology is nearing, or perhaps already on a plateau where only slow, incremental improvement is possible.  This, in turn, will limit the amount of improvement possible for game developers.  Gaming certainly will not disappear, and PC gaming will also not disappear, although the PC gaming share of the market may contract in the future.  But I think it is a reasonable expectation that future PC game titles will not be such dramatic technological improvements over older titles as was the case in the past in the near term.  In the long term, current technology and hardware design will eventually be replaced with something entirely different and disruptive, but as always it is difficult, maybe impossible to predict what that replacement will be.
 
The Good Old Days
 
The start of the modern, hardware-driven PC gaming culture that we all know and love began with Id Software's early first person shooter titles, most importantly 1993's Doom.
 
PC gaming was around before Doom, of course, but Doom's combination of cutting edge graphics technology and massive, massive appeal is what really got the ball rolling.

Doom was phenomenally popular.  There were, at one point, more installs of Doom than there were installs of the Windows operating system.  I don't think there is any subsequent PC title that can claim that.  Furthermore, it was Doom, and its spiritual successor Quake that really defined PC gaming as a genre that pushed the boundaries of what was possible with hardware.
 
Doom convincingly faked 3D graphics on computers that had approximately the same number-crunching might as a potato.  It also demanded radically more computing power than Wolfenstein 3D, but in those days computing hardware was advancing at such a rate that this wasn't really unreasonable.  This was followed by Quake, which was actually 3D, and demanded so much more of the hardware then available that it quickly became one of the first games to support hardware acceleration.
 
Id software disintegrated under the stress of the development of Quake, and while many of the original Id team have gone on to do noteworthy things in PC gaming technology, none of it has been earth-shaking the way their work at Id was.  And so, the next important development occurred not with Id's games, but with their successors.
 
It had become clear, by that point, that there was a strong consumer demand for higher game framerates, but also for better-looking graphics.  In addition to ever-more sophisticated game engines and higher poly-count game models, the next big advance in PC gaming technology was the addition of shaders to the graphics.
 
Shaders could be used to smooth out the low-poly models of the time, apply lighting effects, and generally make the games look less like spiky ass.  But the important caveat about shaders, from a hardware development perspective, was that shader code ran extremely well in parallel while the rest of the game code ran well in series.  The sort of chip that would quickly do the calculations for the main game, and the sort of chip that would do quickly do calculations for the graphics were therefore very different.  Companies devoted exclusively to making graphics-crunching chips emerged (of these, only Nvidia is left standing), and the stage was set for the heyday of PC gaming hardware evolution from the mid 1990s to the early 2000s.  Initially, there were a great number of hardware acceleration options, and getting everything to work was a bit of an inconsistent mess that only enthusiasts really bothered with, but things rapidly settled down to where we are today.  The important rules of thumb which have, hitherto applied are:

-The IBM-compatible personal computer is the chosen mount of the Glorious PC Gaming Master Race™. 
-The two most important pieces of hardware on a gaming PC are the CPU and the GPU, and every year the top of the line CPUs and GPUs will be a little faster than before.
-Even though, as of the mid 2000s, both gaming consoles and Macs were made of predominantly IBM-compatible hardware, they are not suitable devices for the Glorious PC Gaming Master Race™.  This is because they have artificially-imposed software restrictions that keep them from easily being used the same way as a proper gaming PC.
-Even though they did not suffer from the same compatibility issues as consoles or Macs, computers with integrated graphics processors are not suitable devices for the Glorious PC Gaming Master Race™.
-Intel CPUs are the best, and Nvidia GPUs are the best.  AMD is a budget option in both categories.
 
The Victorious March of Moore's Law
 
Moore's Law, which is not an actual physical law, but rather an observation about the shrinkage of the physical size of transistors, has held so true for most of the 21st century that it seemed like it was an actual fundamental law of the universe.
 
The most visible and obvious indication of the continuous improvement in computer hardware was that every year the clock speeds on CPUs got higher.
 

 
Now, clock speed itself isn't actually particularly indicative of overall CPU performance, since that is a complex interplay of clock speed, instructions per cycle and pipe length.  But at the time, CPU architecture was staying more or less the same, so the increase in CPU clock speeds was a reasonable enough, and very marketing-friendly indicator of how swimmingly things were going.  In 2000, Intel was confident that 10 GHZ chips were about a decade away.
 
This reliable increase in computing power corresponded with a reliable improvement in game graphics and design year on year.  You can usually look at a game from the 2000s and guess, to within a few years, when it came out because the graphical improvements were that consistent year after year.
 
The improvement was also rapid.  Compare 2004's Far Cry to 2007's Crysis.
 

 

 
And so, for a time, game designers and hardware designers marched hand in hand towards ever greater performance.
 
The End of the Low-Hanging Fruit
 
But you know how this works, right?  Everyone has seen VH1's Behind the Music.  This next part is where it all comes apart after the explosive success and drugs and groupies, leaving just the drugs.  This next part is where we are right now.
 
If you look again at the chart of CPU clock speeds, you see that improvement flatlines at about 2005.  This is due to the end of Dennard Scaling.  Until about 2006, reductions in the size of transistors allowed chip engineers to increase clock speeds without worrying about thermal issues, but that isn't the case anymore.  Transistors have become so small that significant amounts of current leakage occur, meaning that clock speeds cannot improve without imposing unrealistic thermal loads on the chips.
 
Clock speed isn't everything.  The actual muscle of a CPU is a function of several things; the pipeline, the instructions per clock cycle, clock speed, and, after 2005 with the introduction of the Athlon 64X2, the core count.  And, even as clock speed remained the same, these other important metrics did continue to see improvement:



The catch is that the raw performance of a CPU is, roughly speaking, a multiplicative product of all of these things working together.  If the chip designers can manage a 20% increase in IPC and a 20% increase in clock speed, and some enhancements to pipeline design that amount to a 5% improvement, then they're looking at a 51.2% overall improvement in chip performance.  Roughly.  But if they stop being able to improve one of these factors, then to achieve the same increases in performance, they need to cram in the improvements into just the remaining areas, which is a lot harder than making modest improvements across the board.
 
Multi-core CPUs arrived to market at around the same time that clock speed increases became impossible.  Adding more cores to the CPU did initially allow for some multiplicative improvements in chip performance, which did buy time for the trend of ever-increasing performance.  The theoretical FLOPS (floating point operations per second) of a chip is a function of its IPC, core count and clock speed.  However, the real-world performance increase provided by multi-core processing is highly dependent on the degree to which the task can be paralleled, and is subject to Amdahl's Law:


Most games can be only poorly parallelized.  The parallel portion is probably around the 50% mark for everything except graphics, which has can be parallelized excellently.  This means that as soon as CPUs hit 16 cores, there was basically no additional improvement to be had in games from multi-core technology.  That is, unless game designers start to code games specifically for better multi-core performance, but so far this has not happened.  On top of this, adding more cores to a CPU usually imposes a small reduction to clock speed, so the actual point of diminishing returns may occur at a slightly lower core count.
 
On top of all that, designing new and smaller chip architecture has become harder and harder.  Intel first announced 10nm chip architecture back in September 2017, and showed a timeline with it straddling 2017 and 2018.  2018 has come and gone, and still no 10nm.  Currently Intel is hopeful that they can get 10nm chips to market by the end of 2019.
 
AMD have had a somewhat easier time of it, announcing a radically different mixed 14nm and 7nm "chiplet" architecture at the end of 2018, and actually brought a 7nm discrete graphics card to market at the beginning of 2019.  However, this new graphics card merely matches NVIDIA's top-of-the-line cards, both in terms of performance and in terms of price.  This is a significant development, since AMD's graphics cards have usually been second-best, or cost-effective mid-range models at best, so for them to have a competitive top-of-the-line model is noteworthy.  But, while CPUs and GPUs are different, it certainly doesn't paint a picture of obvious and overwhelming superiority for the new 7nm process.  The release of AMD's "chiplet" Zen 2 CPUs appears to have been delayed to the middle of 2019, so I suppose we'll find out then.  Additionally, it appears that the next-generation of Playstation will use a version of AMD's upcoming "Navi" GPU, as well as a Zen CPU, and AMD hardware will power the next-generation XBOX as well. 
 
So AMD is doing quite well servicing the console gaming peasant crowd, at least.  Time will tell whether the unexpected delays faced by their rivals along with the unexpected boost from crypto miners buying literally every fucking GPU known to man will allow them to dominate the hardware market going forward.  Investors seem optimistic, however:


 
With Intel, they seem less sanguine:



and with NVIDIA, well...
 

 
But the bottom line is don't expect miracles.  While it would be enormously satisfying to see Intel and NVIDIA taken down a peg after years of anti-consumer bullshit, the reality is that hardware improvements have fundamentally become difficult.  For the time being, nobody is going to be throwing out their old computers just because they've gotten slow.  As the rate of improvements dwindles, people will start throwing out their old PCs and replacing them only because they've gotten broken.
 
OK, but What About GPUs?
 
GPU improvements took longer to slow down than CPU improvements, in large part because GPU workloads can be parallel processed well.  But the slowdown has arrived.
 
This hasn't stopped the manufacturers of discrete GPUs from trying to innovate, of course.  Not only that; the market is about to become more competitive with Intel announcing their plans for a discrete GPU in the near future.  NVIDIA has pushed their new ray-tracing optimized graphics cards for the past few months as well.  The cryptomining GPU boom has come and gone; GPUs turn out to be better than CPUs at cryptomining, but ASICs beat out GPUs but a lot, so that market is unlikely to be a factor again.  GPUs are still relatively cost-competitive for a variety of machine learning tasks, although long-term these will probably be displaced by custom designed chips like the ones Google is mass-ordering.
 
Things really do not look rosy for GPU sales.  Every time someone discovers some clever alternative use for GPUs like cryptomining or machine learning, they get displaced after a few years by custom hardware solutions even more fine-tuned to the task.  Highly parallel chips are the future, but there's no reason to think that those highly parallel chips will be traditional GPUs, per se.

And speaking of which, aren't CPUs getting more parallel, with their ever-increasing core count?  And doesn't AMD's "chiplet" architecture allow wildly differently optimized cores to be stitched together?  So, the CPU of a computer could very easily be made to accommodate capable on-board graphics muscle.  So... why do we even need GPUs in the future?  After all, PCs used to have discrete sound cards and networking cards, and the CPU does all of that now.  The GPU has really been the last hold-out, and will likely be swallowed by the CPU, at least on low and mid range machines in the next few years.
 
Where to Next?
 
At the end of 2018, popular YouTube tech channel LinusTechTips released a video about Shadow.  Shadow is a company that is planning to use centrally-located servers to provide cloud-based games streaming.  At the time, the video was received with (understandably) a lot of skepticism, and even Linus doesn't sound all that convinced by Shadow's claims.
 
 
The technical problems with such a system seem daunting, especially with respect to latency.  This really did seem like an idea that would come and go.  This is not its time; the technology simply isn't good enough.

And then, just ten days ago, Google announced that they had exactly the same idea:
 
 
The fact that tech colossus Google is interested changed a lot of people's minds about the idea of cloud gaming.  Is this the way forward?  I am unconvinced.  The latency problems do seem legitimately difficult to overcome, even for Google.  Also, almost everything that Google tries to do that isn't search on Android fails miserably.  Remember Google Glass?  Google Plus?
 
But I do think that games that are partially cloud-based will have some market share.  Actually, they already do.  I spent a hell of a lot of time playing World of Tanks, and that game calculates all line-of-sight checks and all gunfire server-side.  Most online games do have some things that are calculated server-side, but WoT was an extreme example for the time.  I could easily see future games offloading a greater amount of the computational load to centralized servers vis a vis the player's own PC.
 
But there are two far greater harbingers of doom for PC gaming than cloud computing.  The first is smart phones and the second is shitty American corporate culture.  Smart phones are set to saturate the world in a way desktop PCs never did.  American games publishers are currently more interested in the profits from gambling-esque game monetization schemes than they are in making games.  Obviously, I don't mean that in a generic anti-capitalist, corporation-bashing hippie way.  I hate hippies.  I fuck hippies for breakfast.  But if you look at even mainstream news outlets on Electronic Arts, it's pretty obvious that the AAA games industry, which had hitherto been part of the engine driving the games/hardware train forward, is badly sick right now.  The only thing that may stop their current sleaziness is government intervention.
 
So, that brings us to the least important, but most discussion-sparking part of the article; my predictions.  In the next few years, I predict that the most popular game titles will be things like Fortnite or Apex Legends.  They will be monetized on some sort of games-as-service model, and will lean heavily if not entirely on multiplayer modes.  They may incorporate some use of server-side calculation to offload the player PC, but in general they will work on modest PCs because they will only aspire to have decent, readable graphics rather than really pretty ones.  The typical "gaming rig" for this type of game will be a modest and inexpensive desktop or laptop running built-in graphics with no discrete graphics card.  There will continue to be an enthusiast market for games that push the limits, but this market will no longer drive the majority of gaming hardware sales.  If these predictions sound suspiciously similar to those espoused by the Coreteks tech channel, that's because I watched a hell of a lot of his stuff when researching this post, and I find his views generally convincing.
 
Intel's Foveros 3D chip architecture could bring a surge in CPU performance, but I predict that it will be a one-time surge, followed by the return to relatively slow improvement.  The reason why is that the Foveros architecture allows for truly massive CPU caches, and these could be used to create enormous IPC gains.  But after the initial boon caused by the change in architecture, the same problems that are currently slowing down improvement would be back, the same as before.  It definitely wouldn't be a return to the good old days of Moore's Law.  Even further down the road, a switch to a different semiconducting material such as Gallium Nitride (which is already used in some wireless devices and military electronics) could allow further miniaturization and speed ups where silicon has stalled out.  But those sort of predictions stretch my limited prescience and knowledge of semiconductor physics too far.
 
If you are interested in this stuff, I recommend diving into Coretek's channel (linked above) as well as Adored TV.

Judges' remarks:
 
Unfinished Designs:
 
 
Object 138:
 
 
Object 426:
 
 
 
 
Bonus panel of the judges politely discussing the finer points of armored fighting vehicle powertrain design:
 

Restricted: for Operating Thetan Eyes Only
 
By order of Her Gracious and Serene Majesty Queen Diane Feinstein the VIII
 
The Dianetic People’s Republic of California
 
Anno Domini 2256
 
SUBJ: New tank contract awards
 
OK, praise be to Hubbard the last prophet and Tom Cruise, his true successor and all that shit that the upper party members will want to see in an official document.  You want to know Hubbard's honest truth?  This entire heavy tank development program has been one big conga line of fuckups since day one.  There's a reason that we're still out there tanking with DF-1s, and that reason is the current government of the DPRC.  Their insane commitment to Scientology has made a mockery of every attempt to maintain a stable and sensible war economy.  Until the ruling regime is liquidated and replaced with a government based on the scientific principles of Euphoric Atheism, the disasters will only compound.


The military tribunal for tank procurement has selected Hakika si Kundi la Dudes Nyeupe (HKDN) design bureau's Object 426 "Stumpy" as the basis for the DPRC's next main battle tank.  In order to facilitate crew competence and speed the de-bugging phase on the way to IOC, the first several dozen vehicles will be sent to a special test unit.  This test unit will be kept separated from the rest of the DPRC military's logistical system and chain of command.  In order to prevent sabotage of the program by the circulation of false reports, the entire test unit and its activities will be kept secret, even from the members of the civilian government.  In order to prevent any theft of the technical secrets of the vehicles, the test unit will be given the authority to shut down all communications and transport networks in the DPRC at its sole discretion.
 
Congratulations, @Toxn

Restricted: for Operating Thetan Eyes Only
 
By order of Her Gracious and Serene Majesty Queen Diane Feinstein the VIII
 
The Dianetic People’s Republic of California
 
Anno Domini 2256
 
SUBJ: New tank contract awards
 
OK, praise be to Hubbard the last prophet and Tom Cruise, his true successor and all that shit that the upper party members will want to see in an official document.  You want to know Hubbard's honest truth?  This entire heavy tank development program has been one big conga line of fuckups since day one.  There's a reason that we're still out there tanking with DF-1s, and that reason is the current government of the DPRC.  Their insane commitment to Scientology has made a mockery of every attempt to maintain a stable and sensible war economy.  Until the ruling regime is liquidated and replaced with a government based on the scientific principles of Euphoric Atheism, the disasters will only compound.


The military tribunal for tank procurement has selected Hakika si Kundi la Dudes Nyeupe (HKDN) design bureau's Object 426 "Stumpy" as the basis for the DPRC's next main battle tank.  In order to facilitate crew competence and speed the de-bugging phase on the way to IOC, the first several dozen vehicles will be sent to a special test unit.  This test unit will be kept separated from the rest of the DPRC military's logistical system and chain of command.  In order to prevent sabotage of the program by the circulation of false reports, the entire test unit and its activities will be kept secret, even from the members of the civilian government.  In order to prevent any theft of the technical secrets of the vehicles, the test unit will be given the authority to shut down all communications and transport networks in the DPRC at its sole discretion.
 
Congratulations, @Toxn

Judges' remarks:
 
Unfinished Designs:
 
 
Object 138:
 
 
Object 426:
 
 
 
 
Bonus panel of the judges politely discussing the finer points of armored fighting vehicle powertrain design:
 

Judges' remarks:
 
Unfinished Designs:
 
 
Object 138:
 
 
Object 426:
 
 
 
 
Bonus panel of the judges politely discussing the finer points of armored fighting vehicle powertrain design:
 

Judges' remarks:
 
Unfinished Designs:
 
 
Object 138:
 
 
Object 426:
 
 
 
 
Bonus panel of the judges politely discussing the finer points of armored fighting vehicle powertrain design:
 

Restricted: for Operating Thetan Eyes Only
 
By order of Her Gracious and Serene Majesty Queen Diane Feinstein the VIII
 
The Dianetic People’s Republic of California
 
Anno Domini 2256
 
SUBJ: New tank contract awards
 
OK, praise be to Hubbard the last prophet and Tom Cruise, his true successor and all that shit that the upper party members will want to see in an official document.  You want to know Hubbard's honest truth?  This entire heavy tank development program has been one big conga line of fuckups since day one.  There's a reason that we're still out there tanking with DF-1s, and that reason is the current government of the DPRC.  Their insane commitment to Scientology has made a mockery of every attempt to maintain a stable and sensible war economy.  Until the ruling regime is liquidated and replaced with a government based on the scientific principles of Euphoric Atheism, the disasters will only compound.


The military tribunal for tank procurement has selected Hakika si Kundi la Dudes Nyeupe (HKDN) design bureau's Object 426 "Stumpy" as the basis for the DPRC's next main battle tank.  In order to facilitate crew competence and speed the de-bugging phase on the way to IOC, the first several dozen vehicles will be sent to a special test unit.  This test unit will be kept separated from the rest of the DPRC military's logistical system and chain of command.  In order to prevent sabotage of the program by the circulation of false reports, the entire test unit and its activities will be kept secret, even from the members of the civilian government.  In order to prevent any theft of the technical secrets of the vehicles, the test unit will be given the authority to shut down all communications and transport networks in the DPRC at its sole discretion.
 
Congratulations, @Toxn

What happens when Google Fiber gives up and fucks off?

Ghost Recon Future Soldier review

 
   Tom Clancy`stm Ghost Recon Future Soldier tm is a 5th game of Ghost Recon series released in 2012 and it’s not a continuation of Advanced Warfighter series released in 2006 and 2007 in any form – story or gameplay. Future Soldier had strange development and it appears it suffered shift in design somewhere between 2010 and 2011. Originally, it was more sci-fi/futuristic 3rd person shooter, at least in art direction and game world background story.
 
 
 
 
 
 
   At E3 2011 developers showed version of GRFS that saw a release – much less futuristic and more “generic” as a result. Some elements from 2010 concept still exist in this game – active camo, X-ray vision and UGVs.
   GRFS tells story of a bombastic action scenes and basic stealth wrapped in re-purposed plot of Modern Warfare series of  CoDs, with Russian Ultranationalists, Civil War, weapon dealers, ICBM launches and shit like that.
   You take a role of “Kozak”, Russian agent that infiltrated super elite SF unit known as “Tom Clancy`stm Ghoststm” with a task to cash in on Modern Warfare craze.
 
   Visuals
   For 2012, game had not bad visuals but nothing outstanding in terms of technical capabilities of their engine.  In fact I would describe technical level as “bad”. Game received plenty of patches but main problems of their engine were not solved – crap optimization on PC and engine that is incapable of handling more than few square meters of space. Those technical problems affected mission design, map layouts and GRFS Singleplayer – as engine could not load map on the fly, after finishing one section of the level engine must load next section of mission with a loading screen, which developers tried to conceal with infographics MW-style cutscenes or just boring cutscenes long enough for loading screen to end. At times you can see very obvious end of maps even when you are moving through very tight spaces. “Open” spaces in this game are just a bit less tight than normal corridors, which make GRFS feel very linear, but with pretty scenery here and there.
 

 
 
   On positive side, locations are different, they all feel unique and there is much less of copy pasting than in GRAW 1 and 2. Plenty of assets are specific for few maps, enemies models for the most part well modelled (with exceptions). Main characters models have a lot of details and plenty of animations, so they feel quite good to move around and look at.  
 
   Gameplay
   Imagine something like The Division, but with stealth sections and no RPG elements and you will understand basics of GRFS gameplay. Cover based shooter with quick deaths outside of cover and fast dashes between cover on separate button during which you move faster than during sprinting for some reason. Action sequences are broken up with basic stealth sections. Stealth mechanics based on LOS, if adaptive camo is on or off and body stance (standing/prone etc.)… and that’s it. Because of small levels that engine can actually support without breaking apart vision of enemies is as bad as in Freedom Fighters – sometimes you need to be just few meters in front of enemies (in crouch position in the middle of road) for them to spot you quickly. Once you spotted game enter combat mode, from which you can’t get back to stealth gameplay until next sequence (sometimes devs put a script that in case of spotting of a player makes all next section of levels to be “alerted” when activated by player moving into them). 
   Several times you also “breach” a room in MW-style slow-mo, but with added on-rail movement and limited arc in which you can aim your gun. 
   Interesting note - one mission have 2 slightly different endings depending on how you decided to complete last objective on map. All other missions have nothing like this, at least i didn't managed to get different results.
 

 
 
   Shooting is very basic as well, with exception of object penetration mechanics, which was surprising to see here. Enemies are dying from 1 hit in any part of their body when in stealth mode, once combat is triggered they can take 2-3 shots from most of guns (1-2 from sniper rifles). Body armor is not counted for penetration mechanics as far as I can tell, only scenery objects are affected by that mechanics. Combat ranges (thanks to engine and map design) are mostly close range (10-20 meters) with rare medium range firefights (usually snipers, over 50 meters). Player have regenerating health, which also leads to “bland” feeling of combat.
   Majority of bad guys are generic 3rd person shooters “guy with a gun” enemies, they run to nearest cover and shoot from it and that is most of what they can do. Enemies have few different types – generic cannon fodder, shotgunners who usually rush to you mindlessly, MG gunners (they can suppress you and force your camera to shake), shield troopers (very rare), snipers and Spec ops (who just have adaptive camo compared to usual cannon fodder). There are few vehicles in game, but those are mostly scripted sequences and they all act somewhat similar, HE UGL are very effective against them.
 
 
   Majority of guns feel the same, even if game allows you to modify a lot of weapon parts (up to a trigger and gas system). Majority of enemies are easy to kill and hardly memorable. Majority of combat and stealth sequences feel like they were copy-pasted (at least mechanically), there is little difference between fighting PMCs, African militia, Russian Spec ops or Regular army – AI is the same for them, vast majority of enemies are exactly the same cannon fodder and they have exactly the same very basic behavior and selection of similar guns. All that happens on maps with rather generic linear corridor layout, with some small “arena” sections that are also rather generic as they most of the time don’t have interesting power positions or flanking routes (it’s not like you really need them anyway). Majority of firefights happens on a plain field-like area with chest-high walls randomly scattered across it.
   There are positives in gameplay (without them I wouldn’t be bothered to play more than just a singleplayer without bothering to re-play it on higher difficulties or playing survival mode) – shooting and killing bad guys is satisfying, especially through cover with LMGs. On high difficulties and in some areas stealth sections are pretty fun to play (when they are build as some sort of puzzle).
   Overall, general bombastic nature of combat managed to give some faint flavor to very generic combat. It is not really “good” but not completely grey and boring.
 
 
   Pacing of levels on the other hand is terrible (IMO). Because of engine needing time to load next section of level developers are covering loading screens (Anthem, kek) with cutscenes, showing something really boring like team stopping and checking their gear while talking mission objectives at you. There is a lot of waiting for quick action that ends fast and don’t require you to even attempt to use your brains.
   Combat sequences are not properly “directed” by level makers – they just sprinkled levels with spawn points and when combat starts some number of bad guys are spawn and thrown at player without any twist or interesting insertion or rule or anything other than “spawn in and die in 12 nanoseconds while firing from nearest cover”. At times you even can see enemies spawning with “naked” eye…
 
 
   Outside of guns and explosives, GRFS also gives you some gadgets to play around. Some of them are obvious like night vision goggles, some are a bit less standard – X-ray vision that is limited in range but can see through everything, sensors that can spot all enemies in certain range, drone (that now became standard for open-world games) for spotting that also can transform into crawler and stun enemies with sonic attack. In specific mission you can control an UGV with indirect fire weapons, which was fun.
   Problems with those spotting gadgets and visions that they make firefights feel even less interesting – you see all enemies and just fire at red markers until they are white and that is all. At no point developers game you an interesting situation that can be resolved with use of those gadgets or mechanics based on use of those systems. There was IIRC 2 sections with sandstorm/snowstorm, but you can blitz through those without use of x-ray vision just by following markers, HUD markers/muzzle flashes. For example killing one of main bad guys in GRFS was done through slow-mo room breach (MW-style) but set-up was perfect for using both X-ray vision and bullet penetration mechanics to kill all “elite” guards inside of that room without even entering it, or killing main bad guy with just one shot. That would have been cool looking and fitting that “edgy high tech cool badass hardcore military” theme of GRFS. Also those things make friendly AI surprisingly-well developed callout system to be useless as well (friendlies when see enemies call their position or direction, numbers of enemies, weapons they have, but not in Arma 3 robotic-like voice system. GRFS sounds much more human, thanks to a lot of voice lines recorded and AI starting sometimes asking additional questions about enemies and so on). 
 
 
   All this leads to perception of action side of GRFS as mostly bland, generic, basic 3rd person action game with few features that had potential but didn’t build anything on top of it.
 
   On top of that, many levels ends in exactly same way – player-“controlled” either missile attack to kill horde of enemies who boxed you in, or literally on-rail shooting gallery (aka “diamond formation” or turret sections). Ugh, this game is disappointing when you see all potential it had…   
   Ow, i also want to mention that GRFS treats players as idiots, throws stupid hints at you until very end of campaign, sometimes locks you in place and allow to press only certain buttons, without pressing them you will not progress. Great design right here, guys.
 
   
   Plot
   Story in GRFS is CoD MW plots put through “blend”-er. Even some scenes are same in principle – shocking terrorist attack in MW2 and MW3 have their cousin in GRFS, and it is as stupid as in those 2 CoDs.
   I don’t remember names of any bad guys, because main bad guys were shown just in last 2 missions and payer was told about their existence few seconds before player puts bullet through main villains heads.
   All dialogues, cutscenes, intro videos and radio chatter tries so hard to be that “edgy high tech cool badass hardcore military” that is becoming just pure cringe. Especially scenes on aircraft carrier… good they are awful to watch (i didn't made any screenshots of them). Moreover, some of them are unskippable!
 

 
 
 
   Conclusion
   Series that started as action game that tried to be different from what most of shooters on a market were and peeked into realistic representation of combat became generic console cover-based 3rd person shooty-shooty game with explosions, beer, Evil Russians, cardboard badass edgy hardcore Special Forces generic dudes, more explosions, nukes, explosions, turret sections, floating in a pit of grey bland MVP game with “look over substance” written all over it. Regress of this series that started somewhere in GRAW 1 is completed here, in GRFS. In GRAW 1 and 2 attempt was made to distance PC versions from console pukes, but was not made for GRFS… Well, at least shooting through cover is fun in GRFS and explosions sound nice. A lot of missed potential with gadgets and tech-related mechanis, that developers didn't "played" with anywhere enough make me sad.
   You can play it and even have some fun here and there, but Tom Clancy`stm Ghost Recon Future Soldier tm is just a bit above completely generic thanks to fun shooting, few stupid cutscenes and explosions.
   Next game – Wildlands, became a few drops more generic, a nearly standard “Ubisoft open world 3rd person shooter”, but at least with better engine than GRFS. 

Y'all ready for some drugs?
 
 

But if you try sometimes...

Fighter aircraft became much better during the Second World War.  But, apart from the development of engines, it was not a straightforward matter of monotonous improvement.  Aircraft are a series of compromises.  Improving one aspect of performance almost always compromises others.  So, for aircraft designers in World War Two, the question was not so much "what will we do to make this aircraft better?" but "what are we willing to sacrifice?"


 
To explain why, let's look at the forces acting on an aircraft:

Lift
 
Lift is the force that keeps the aircraft from becoming one with the Earth.  It is generally considered a good thing. 
 
The lift equation is L=0.5CLRV2A where L is lift, CL is lift coefficient (which is a measure of the effectiveness of the wing based on its shape and other factors), R is air density, V is airspeed and A is the area of the wing.

Airspeed is very important to an aircraft's ability to make lift, since the force of lift grows with the square of airspeed and in linear relation to all other factors.  This means that aircraft will have trouble producing adequate lift during takeoff and landing, since that's when they slow down the most.
 
Altitude is also a significant factor to an aircraft's ability to make lift.  The density of air decreases at an approximately linear rate with altitude above sea level:



Finally, wings work better the bigger they are.  Wing area directly relates to lift production, provided that wing shape is kept constant.

While coefficient of lift CL contains many complex factors, one important and relatively simple factor is the angle of attack, also called AOA or alpha.  The more tilted an airfoil is relative to the airflow, the more lift it will generate.  The lift coefficient (and thus lift force, all other factors remaining equal) increases more or less linearly until the airfoil stalls:





Essentially what's going on is that the greater the AOA, the more the wing "bends" the air around the wing.  But the airflow can only become so bent before it detaches.  Once the wing is stalled it doesn't stop producing lift entirely, but it does create substantially less lift than it was just before it stalled.  

Drag
 
Drag is the force acting against the movement of any object travelling through a fluid.  Since it slows aircraft down and makes them waste fuel in overcoming it, drag is a total buzzkill and is generally considered a bad thing.

The drag equation is D=0.5CDRV2A where D is drag, CD is drag coefficient (which is a measure of how "draggy" a given aircraft is), R is air density, V is airspeed and A is the frontal area of the aircraft.

This equation is obviously very similar to the lift equation, and this is where designers hit the first big snag.  Lift is good, but drag is bad, but because the factors that cause these forces are so similar, most measures that will increase lift will also increase drag.  Most measures that reduce drag will also reduce lift.

Generally speaking, wing loading (the amount of wing area relative to the plane's weight) increased with newer aircraft models.  The stall speed (the slowest possible speed at which an aircraft can fly without stalling) also increased.  The massive increases in engine power alone were not sufficient to provide the increases in speed that designers wanted.  They had to deliberately sacrifice lift production in order to minimize drag.
 
World War Two saw the introduction of laminar-flow wings.  These were wings that had a cross-section (or airfoil) that generated less turbulent airflow than previous airfoil designs.  However, they also generated much less lift.  Watch a B-17 (which does not have a laminar-flow wing) and a B-24 (which does) take off.  The B-24 eats up a lot more runway before its nose pulls up.


 
There are many causes of aerodynamic drag, but lift on a WWII fighter aircraft can be broken down into two major categories.  There is induced drag, which is caused by wingtip vortices and is a byproduct of lift production, and parasitic drag which is everything else.  Induced drag is interesting in that it actually decreases with airspeed.  So for takeoff and landing it is a major consideration, but for cruising flight it is less important.


However, induced drag is also significant during combat maneuvering.  Wing with a higher aspect ratio, that is, the ratio of the wingspan to the wing chord (which is the distance from the leading edge to the trailing edge of the wing) produce less induced drag.
 


So, for the purposes of producing good cruise efficiency, reducing induced drag was not a major consideration.  For producing the best maneuvering fighter, reducing induced drag was significant.

Weight
 
Weight is the force counteracting lift.  The more weight an aircraft has, the more lift it needs to produce.  The more lift it needs to produce, the larger the wings need to be and the more drag they create.  The more weight an aircraft has, the less it can carry.  The more weight an aircraft has, the more sluggishly it accelerates.  In general, weight is a bad thing for aircraft.  But for fighters in WWII, weight wasn't entirely a bad thing.  The more weight an aircraft has relative to its drag, the faster it can dive.  Diving away to escape enemies if a fight was not going well was a useful tactic.  The P-47, which was extremely heavy, but comparatively well streamlined, could easily out-dive the FW-190A and Bf-109G/K.

In general though, designers tried every possible trick to reduce aircraft weight.  Early in the war, stressed-skin monocoque designs began to take over from the fabric-covered, built-up tube designs.


The old-style construction of the Hawker Hurricane.  It's a shit plane.
 

Stressed-skin construction of the Spitfire, with a much better strength to weight ratio.
 
But as the war dragged on, designers tried even more creative ways to reduce weight.  This went so far as reducing the weight of the rivets holding the aircraft together, stripping the aircraft of any unnecessary paint, and even removing or downgrading some of the guns.


An RAF Brewster Buffalo in the Pacific theater.  The British downgraded the .50 caliber machine guns to .303 weapons in order to reduce weight.
 
In some cases, however, older construction techniques were used at the war's end due to materials shortages or for cost reasons.  The German TA-152, for instance, used a large amount of wooden construction with steel reinforcement in the rear fuselage and tail in order to conserve aluminum.  This was not as light or as strong as aluminum, but beggars can't be choosers.


Extensive use of (now rotten) wood in the rear fuselage of the TA-152
 
Generally speaking, aircraft get heavier with each variant.  The Bf-109C of the late 1930s weighed 1,600 kg, but the Bf-109G of the second half of WWII had ballooned to over 2,200 kg.  One notable exception was the Soviet YAK-3:


 
The YAK-3, which was originally designated YAK-1M, was a demonstration of what designers could accomplish if they had the discipline to keep aircraft weight as low as possible.  Originally, it had been intended that The YAK-1 (which had somewhat mediocre performance vs. German fighters) would be improved by installing a new engine with more power.  But all of the new and more powerful engines proved to be troublesome and unreliable.  Without any immediate prospect of more engine power, the Yakovlev engineers instead improved performance by reducing weight.  The YAK-3 ended up weighing nearly 300 kg less than the YAK-1, and the difference in performance was startling.  At low altitude the YAK-3 had a tighter turn radius than anything the Luftwaffe had.  
 
Thrust
 
Thrust is the force propelling the aircraft forwards.  It is generally considered a good thing.  Thrust was one area where engineers could and did make improvements with very few other compromises.  The art of high-output piston engine design was refined during WWII to a precise science, only to be immediately rendered obsolete by the development of jet engines.
 
Piston engined aircraft convert engine horsepower into thrust airflow via a propeller.  Thrust was increased during WWII primarily by making the engines more powerful, although there were also some improvements in propeller design and efficiency.  A tertiary source of thrust was the addition of jet thrust from the exhaust of the piston engines and from Merideth Effect radiators.
 
The power output of WWII fighter engines was improved in two ways; first by making the engines larger, and second by making the engines more powerful relative to their weight.  Neither process was particularly straightforward or easy, but nonetheless drastic improvements were made from the war's beginning to the war's end.

The Pratt and Whitney Twin Wasp R-1830-1 of the late 1930s could manage about 750-800 horsepower.  By mid-war, the R-1830-43 was putting out 1200 horsepower out of the same displacement.  Careful engineering, gradual improvements, and the use of fuel with a higher and more consistent octane level allowed for this kind of improvement.


The R-1830 Twin Wasp

However, there's no replacement for displacement.  By the beginning of 1943, Japanese aircraft were being massacred with mechanical regularity by a new US Navy fighter, the F6F Hellcat, which was powered by a brand new Pratt and Whitney engine, the R-2800 Double Wasp.


The one true piston engine

As you can see from the cross-section above, the R-2800 has two banks of cylinders.  This is significant to fighter performance because even though it had 53% more engine displacement than the Twin Wasp (For US engines, the numerical designation indicated engine displacement in square inches), the Double Wasp had only about 21% more frontal area.  This meant that a fighter with the R-2800 was enjoying an increase in power that was not proportionate with the increase in drag.  Early R-2800-1 models could produce 1800 horsepower, but by war's end the best models could make 2100 horsepower.  That meant a 45% increase in horsepower relative to the frontal area of the engine.  Power to weight ratios for the latest model R-1830 and R-2800 were similar, while power to displacement improved by about 14%.
 
By war's end Pratt and Whitney had the monstrous R-4360 in production:



This gigantic engine had four rows of radially-arranged pistons.  Compared to the R-2800 it produced about 50% more power for less than 10% more frontal area.  Again, power to weight and power to displacement showed more modest improvements.  The greatest gains were from increasing thrust with very little increase in drag.  All of this was very hard for the engineers, who had to figure out how to make crankshafts and reduction gear that could handle that much power without breaking, and also how to get enough cooling air through a giant stack of cylinders.

Attempts at boosting the thrust of fighters with auxiliary power sources like rockets and ramjets were tried, but were not successful.


Yes, that is a biplane with retractable landing gear and auxiliary ramjets under the wings.  Cocaine is a hell of a drug.

A secondary source of improvement in thrust came from the development of better propellers.  Most of the improvement came just before WWII broke out, and by the time the war broke out, most aircraft had constant-speed propellers.



For optimal performance, the angle of attack of the propeller blades must be matched to the ratio of the forward speed of the aircraft to the circular velocity of the propeller tips.  To cope with the changing requirements, constant speed or variable pitch propellers were invented that could adjust the angle of attack of the propeller blades relative to the hub.



There was also improvement in using exhaust from the engine and the waste heat from the engine to increase thrust.  Fairly early on, designers learned that the enormous amount of exhaust produced by the engine could be directed backwards to generate thrust.  Exhaust stacks were designed to work as nozzles to harvest this small source of additional thrust:


The exhaust stacks of the Merlin engine in a Spitfire act like jet nozzles

A few aircraft also used the waste heat being rejected by the radiator to produce a small amount of additional thrust.  The Meredith Effect radiator on the P-51 is the best-known example:



Excess heat from the engine was radiated into the moving airstream that flowed through the radiator.  The heat would expand the air, and the radiator was designed to use this expansion and turn it into acceleration.  In essence, the radiator of the P-51 worked like a very weak ramjet.  By the most optimistic projections the additional thrust from the radiator would cancel out the drag of the radiator at maximum velocity.  So, it may not have provided net thrust, but it did still provide thrust, and every bit of thrust mattered.
 
 
For the most part, achieving specific design objectives in WWII fighters was a function of minimizing weight, maximizing lift, minimizing drag and maximizing thrust.  But doing this in a satisfactory way usually meant emphasizing certain performance goals at the expense of others.
 
Top Speed, Dive Speed and Acceleration
 
During the 1920s and 1930s, the lack of any serious air to air combat allowed a number of crank theories on fighter design to develop and flourish.  These included the turreted fighter:



The heavy fighter:



And fighters that placed far too much emphasis on turn rate at the expense of everything else:



But it quickly became clear, from combat in the Spanish Civil War, China, and early WWII, that going fast was where it was at.  In a fight between an aircraft that was fast and an aircraft that was maneuverable, the maneuverable aircraft could twist and pirouette in order to force the situation to their advantage, while the fast aircraft could just GTFO the second that the situation started to sour.  In fact, this situation would prevail until the early jet age when the massive increase in drag from supersonic flight made going faster difficult, and the development of heat-seeking missiles made it dangerous to run from a fight with jet nozzles pointed towards the enemy.
 
The top speed of an aircraft is the speed at which drag and thrust balance each other out, and the aircraft stops accelerating.  Maximizing top speed means minimizing drag and maximizing thrust.  The heavy fighters had a major, inherent disadvantage in terms of top speed.  This is because twin engined prop fighters have three big lumps contributing to frontal area; two engines and the fuselage.  A single engine fighter only has the engine, with the rest of the fuselage tucked neatly behind it.  The turret fighter isn't as bad; the turret contributes some additional drag, but not as much as the twin-engine design does.  It does, however, add quite a bit of weight, which cripples acceleration even if it has a smaller effect on top speed.  Early-war Japanese and Italian fighters were designed with dogfight  performance above all other considerations, which meant that they had large wings to generate large turning forces, and often had open cockpits for the best possible visibility.  Both of these features added drag, and left these aircraft too slow to compete against aircraft that sacrificed some maneuverability for pure speed.

Drag force rises roughly as a square function of airspeed (throw this formula out the window when you reach speeds near the speed of sound).  Power is equal to force times distance over time, or force times velocity.  So, power consumed by drag will be equal to drag coefficient times frontal area times airspeed squared times airspeed.  So, the power required for a given maximum airspeed will be a roughly cubic function.  And that is assuming that the efficiency of the propeller remains constant!
 
Acceleration is (thrust-drag)/weight.  It is possible to have an aircraft that has a high maximum speed, but quite poor acceleration and vice versa.  Indeed, the A6M5 zero had a somewhat better power to weight ratio than the F6F5 Hellcat, but a considerably lower top speed.  In a drag race the A6M5 would initially pull ahead, but it would be gradually overtaken by the Hellcat, which would eventually get to speeds that the zero simply could not match.

Maximum dive speed is also a function of drag and thrust, but it's a bit different because the weight of the aircraft times the sine of the dive angle also counts towards thrust.  In general this meant that large fighters dove better.  Drag scales with the frontal area, which is a square function of size.  Weight scales with volume (assuming constant density), which is a cubic function of size.  Big American fighters like the P-47 and F4U dove much faster than their Axis opponents, and could pick up speed that their opponents could not hope to match in a dive.

A number of US fighters dove so quickly that they had problems with localized supersonic airflow.  Supersonic airflow was very poorly understood at the time, and many pilots died before somewhat improvisational solutions like dive brakes were added.


Ranking US ace Richard Bong takes a look at the dive brakes of a P-38

Acceleration, top speed and dive speed are all improved by reducing drag, so every conceivable trick for reducing parasitic drag was tried.


The Lockheed P-38 used flush rivets on most surfaces as well as extensive butt welds to produce the smoothest possible flight surfaces.  This did reduce drag, but it also contributed to the great cost of the P-38.


The Bf 109 was experimentally flown with a V-tail to reduce drag.  V-tails have lower interference drag than conventional tails, but the modification was found to compromise handling during takeoff and landing too much and was not deemed worth the small amount of additional speed.


The YAK-3 was coated with a layer of hard wax to smooth out the wooden surface and reduce drag.  This simple improvement actually increased top speed by a small, but measurable amount!  In addition, the largely wooden structure of the aircraft had few rivets, which meant even less drag.


The Donier DO-335 was a novel approach to solving the problem of drag in twin-engine fighters.  The two engines were placed at the front and rear of the aircraft, driving a pusher and a tractor propeller.  This unconventional configuration led to some interesting problems, and the war ended before these could be solved.


The J2M Raiden had a long engine cowling that extended several feet forward in front of the engine.  This tapered engine cowling housed an engine-driven fan for cooling air as well as a long extension shaft of the engine to drive the propeller.  This did reduce drag, but at the expense of lengthening the nose and so reducing pilot visibility, and also moving the center of gravity rearward relative to the center of lift.
 
Designers were already stuffing the most powerful engines coming out of factories into aircraft, provided that they were reasonably reliable (and sometimes not even then).  After that, the most expedient solution to improve speed was to sacrifice lift to reduce drag and make the wings smaller.  The reduction in agility at low speeds was generally worth it, and at higher speeds relatively small wings could produce satisfactory maneuverability since lift is a square function of velocity.  Alternatively, so-called laminar flow airfoils (they weren't actually laminar flow) were substituted, which produced less drag but also less lift.  
 

The Bell P-63 had very similar aerodynamics to the P-39 and nearly the same engine, but was some 80 KPH faster thanks to the new laminar flow airfoils.  However, the landing speed also increased by about 40 KPH, largely sacrificing the benevolent landing characteristics that P-39 pilots loved.

The biggest problem with reducing the lift of the wings to increase speed was that it made takeoff and landing difficult.  Aircraft with less lift need to get to higher speeds to generate enough lift to take off, and need to land at higher speeds as well.  As the war progressed, fighter aircraft generally became trickier to fly, and the butcher's bill of pilots lost in accidents and training was enormous.
 
Turn Rate
 
Sometimes things didn't go as planned.  A fighter might be ambushed, or an ambush could go wrong, and the fighter would need to turn, turn, turn.  It might need to turn to get into a position to attack, or it might need to turn to evade an attack.



Aircraft in combat turn with their wings, not their rudders.  This is because the wings are way, way bigger, and therefore much more effective at turning the aircraft.  The rudder is just there to make the nose do what the pilot wants it to.  The pilot rolls the aircraft until it's oriented correctly, and then begins the turn by pulling the nose up.  Pulling the nose up increases the angle of attack, which increases the lift produced by the wings.  This produces centripetal force which pulls the plane into the turn.  Since WWII aircraft don't have the benefit of computer-run fly-by-wire flight control systems, the pilot would also make small corrections with rudder and ailerons during the turn.

But, as we saw above, making more lift means making more drag.  Therefore, when aircraft turn they tend to slow down unless the pilot guns the throttle.  Long after WWII, Col. John Boyd (PBUH) codified the relationship between drag, thrust, lift and weight as it relates to aircraft turning performance into an elegant mathematical model called energy-maneuverability theory, which also allowed for charts that depict these relationships.

Normally, I would gush about how wonderful E-M theory is, but as it turns out there's an actual aerospace engineer named John Golan who has already written a much better explanation than I would likely manage, so I'll just link that.  And steal his diagram:


E-M charts are often called "doghouse plots" because of the shape they trace out.  An E-M chart specifies the turning maneuverability of a given aircraft with a given amount of fuel and weapons at a particular altitude.  Turn rate is on the Y axis and airspeed is on the X axis.  The aircraft is capable of flying in any condition within the dotted line, although not necessarily continuously.  The aircraft is capable of flying continuously anywhere within the dotted line and under the solid line until it runs out of fuel.

The aircraft cannot fly to the left of the doghouse because it cannot produce enough lift at such a slow speed to stay in the air.  Eventually it will run out of sky and hit the ground.  The curved, right-side "roof" of the doghouse is actually a continuous quadratic curve that represents centrifugal force.  The aircraft cannot fly outside of this curve or it or the pilot will break from G forces.  Finally, the rightmost, vertical side of the doghouse is the maximum speed that the aircraft can fly at; either it doesn't have the thrust to fly faster, or something breaks if the pilot should try.  The peak of the "roof" of the doghouse represents the aircraft's ideal airspeed for maximum turn rate.  This is usually called the "corner velocity" of the aircraft.

So, let's look at some actual (ish) EM charts:


 
 


Now, these are taken from a flight simulator, but they're accurate enough to illustrate the point.  They're also a little busier than the example above, but still easy enough to understand.  The gray plot overlaid on the chart consists of G-force (the curves) and turn radius (the straight lines radiating from the graph origin).  The green doghouse shows the aircraft's performance with flaps.  The red curve shows the maximum sustained turn rate.  You may notice that the red line terminates on the X axis at a surprisingly low top speed; that's because these charts were made for a very low altitude confrontation, and their maximum level top could only be achieved at higher altitudes.  These aircraft could fly faster than the limits of the red line show, but only if they picked up extra speed from a dive.  These charts could also be overlaid on each other for comparison, but in this case that would be like a graphic designer vomiting all over the screen, or a Studio Killers music video.

From these charts, we can conclude that at low altitude the P-51D enjoys many advantages over the Bf 109G-6.  It has a higher top speed at this altitude, 350-something vs 320-something MPH.  However, the P-51 has a lower corner speed.  In general, the P-51's flight envelope at this altitude is just bigger.  But that doesn't mean that the Bf 109 doesn't have a few tricks.  As you can see, it enjoys a better sustained turn rate from about 175 to 325 MPH.  Between those speed bands, the 109 will be able to hold on to its energy better than the pony provided it uses only moderate turns.

During turning flight, our old problem induced drag comes back to haunt fighter designers.  The induced drag equation is Cdi = (Cl^2) / (pi * AR * e).  Where Cdi is the induced drag coefficient, Cl is the lift coefficient, pi is the irrational constant pi, AR is aspect ratio, or wingspan squared divided by wing area, and e is not the irrational constant e but an efficiency factor.

There are a few things of interest here.  For starters, induced drag increases with the square of the lift coefficient.  Lift coefficient increases more or less linearly (see above) with angle of attack.  There are various tricks for increasing wing lift nonlinearly, as well as various tricks for generating lift with surfaces other than the wings, but in WWII, designers really didn't use these much.  So, for all intents and purposes, the induced drag coefficient will increase with the square of angle of attack, and for a given airspeed, induced drag will increase with the square of the number of Gs the aircraft is pulling.  Since this is a square function, it can outrun other, linear functions easily, so minimizing the effect of induced drag is a major consideration in improving the sustained turn performance of a fighter.

To maximize turn rate in a fighter, designers needed to make the fighter as light as possible, make the engine as powerful as possible, make the wings have as much area as possible, make the wings as long and skinny as possible, and to use the most efficient possible wing shape.

You probably noticed that two of these requirements, make the plane as light as possible and make the wings as large as possible, directly contradict the requirements of good dive performance.  There is simply no way to reconcile them; the designers either needed to choose one, the other, or come to an intermediate compromise.  There was no way to have both great turning performance and great diving performance.

Since the designers could generally be assumed to have reduced weight to the maximum possible extent and put the most powerful engine available into the aircraft, that left the design of the wings.

The larger the wings, the more lift they generate at a given angle of attack.  The lower the angle of attack, the less induced drag.  The bigger wings would add more drag in level flight and reduce top speed, but they would actually reduce drag during maneuvering flight and improve sustained turn rate.  A rough estimate of the turning performance of the aircraft can be made by dividing the weight of the aircraft over its wing area.  This is called wing loading, and people who ought to know better put far too much emphasis on it.  If you have E-M charts, you don't need wing loading.  However, E-M charts require quite a bit of aerodynamic data to calculate, while wing loading is much simpler.
 
Giving the wings a higher aspect ratio would also improve turn performance, but the designers hands were somewhat tied in this respect.  The wings usually stored the landing gear and often the armament of the fighter.  In addition the wings generated the lift, and making the wings too long and skinny would make them too structurally flimsy to support the aircraft in maneuvering flight.  That is, unless they were extensively reinforced, which would add weight and completely defeat the purpose.  So, designers were practically limited in how much they could vary the aspect ratio of fighter wings.

The wing planform has significant effect on the efficiency factor e.  The ideal shape to reduce induced drag is the "elliptical" (actually two half ellipses) wing shape used on the Supermarine spitfire.



This wing shape was, however, difficult to manufacture.  By the end of the war, engineers had come up with several wing planforms that were nearly as efficient as the elliptical wing, but were much easier to manufacture.

Another way to reduce induced drag is to slightly twist the wings of the aircraft so that the wing tips point down.



This is called washout.  The main purpose of washout was to improve the responsiveness of the ailerons during hard maneuvering, but it could give small efficiency improvements as well.  Washout obviously complicates the manufacture of the wing, and thus it wasn't that common in WWII, although the TA-152 notably did have three degrees of tip washout.

The Bf 109 had leading edge slats that would deploy automatically at high angles of attack.  Again, the main intent of these devices was to improve the control of the aircraft during takeoff and landing and hard maneuvering, but they did slightly improve the maximum angle of attack the wing could be flown at, and therefore the maximum instantaneous turn rate of the aircraft.  The downside of the slats was that they weakened the wing structure and precluded the placement of guns inside the wing.


leading edge slats of a Bf 109 in the extended position

One way to attempt to reconcile the conflicting requirements of high speed and good turning capability was the "butterfly" flaps seen on Japanese Nakajima fighters.


This model of a Ki-43 shows the location of the butterfly flaps; on the underside of the wings, near the roots

These flaps would extend during combat, in the case of later Nakajima fighters, automatically, to increase wing area and lift.  During level and high speed flight they would retract to reduce drag.  Again, this would mainly improve handling on the left hand side of the doghouse, and would improve instantaneous turn rate but do very little for sustained turn rate.
 
In general, turn performance was sacrificed in WWII for more speed, as the two were difficult to reconcile.  There were a small number of tricks known to engineers at the time that could improve instantaneous turn rate on fast aircraft with high wing loading, but these tricks were inadequate to the task of designing an aircraft that was very fast and also very maneuverable.  Designers tended to settle for as fast as possible while still possessing decent turning performance.
 
Climb Rate
 
Climb rate was most important for interceptor aircraft tasked with quickly getting to the level of intruding enemy aircraft.  When an aircraft climbs it gains potential energy, which means it needs spare available power.  The specific excess power of an aircraft is equal to V/W(T-D) where V is airspeed, W is weight, T is thrust and D is drag.  Note that lift isn't anywhere in this equation!  Provided that the plane has adequate lift to stay in the air and its wings are reasonably efficient at generating lift so that the D term doesn't get too high, a plane with stubby wings can be quite the climber!

The Mitsubishi J2M Raiden is an excellent example of what a fighter optimized for climb rate looked like.


A captured J2M in the US during testing

The J2M had a very aerodynamically clean design, somewhat at the expense of pilot visibility and decidedly at the expense of turn rate.  The airframe was comparatively light, somewhat at the expense of firepower and at great expense to fuel capacity.  Surprisingly for a Japanese aircraft, there was some pilot armor.  The engine was, naturally, the most powerful available at the time.  The wings, in addition to being somewhat small by Japanese standards, had laminar-flow airfoils that sacrificed maximum lift for lower drag.

The end result was an aircraft that was the polar opposite of the comparatively slow, long-ranged and agile A6M zero-sen fighters that IJN pilots were used to!  But it certainly worked.  The J2M was one of the fastest-climbing piston engine aircraft of the war, comparable to the F8F Bearcat.

The design requirements for climb rate were practically the same as the design requirements for acceleration, and could generally be reconciled with the design requirements for dive performance and top speed.  The design requirements for turn rate were very difficult to reconcile with the design requirements for climb rate.
 
Roll Rate
 
In maneuvering combat aircraft roll to the desired orientation and then pitch.  The ability to roll quickly allows the fighter to transition between turns faster, giving it an edge in maneuvering combat.

Aircraft roll with their ailerons by making one wing generate more lift while the other wing generates less lift.



The physics from there are the same for any other rotating object.  Rolling acceleration is a function of the amount of torque that the ailerons can provide divided by the moment of inertia of the aircraft about the roll axis.  So, to improve roll rate, a fighter needs the lowest possible moment of inertia and the highest possible torque from its ailerons.

The FW-190A was the fighter best optimized for roll rate.  Kurt Tank's design team did everything right when it came to maximizing roll rate.


The FW-190 could out-roll nearly every other piston fighter
 

 
The FW-190 has the majority of its mass near the center of the aircraft.  The fuel is all stored in the fuselage and the guns are located either above the engine or in the roots of the wings.  Later versions added more guns, but these were placed just outside of the propeller arc.

Twin engined fighters suffered badly in roll rate in part because the engines had to be placed far from the centerline of the aircraft.  Fighters with armament far out in the wings also suffered.



The ailerons were very large relative to the size of the wing.  This meant that they could generate a lot of torque.  Normally, large ailerons were a problem for pilots to deflect.  Most World War Two fighters did not have any hydraulic assistance; controls needed to be deflected with muscle power alone, and large controls could encounter too much wind resistance for the pilots to muscle through at high speed.

The FW-190 overcame this in two ways.  The first was that, compared to the Bf 109, the cockpit was decently roomy.  Not as roomy as a P-47, of course, but still a vast improvement.  Cockpit space in World War Two fighters wasn't just a matter of comfort.  The pilots needed elbow room in the cockpit in order to wrestle with the control stick.  The FW-190 also used controls that were actuated by solid rods rather than by cables.  This meant that there was less give in the system, since cables aren't completely rigid.

Additionally, the FW-190 used Frise ailerons, which have a protruding tip that bites into the wind and reduces the necessary control forces:


 
Several US Navy fighters, like later models of F6F and F4U used spring-loaded aileron tabs, which accomplished something similar by different means:



In these designs a spring would assist in pulling the aileron one way, and a small tab on the aileron the opposite way in order to aerodynamically move the aileron.  This helped reduce the force necessary to move the ailerons at high speeds.

Another, somewhat less obvious requirement for good roll rate in fighters was that the wings be as rigid as possible.  At high speeds, the force of the ailerons deflecting would tend to twist the wings of the aircraft in the opposite direction.  Essentially, the ailerons began to act like servo tabs.  This meant that the roll rate would begin to suffer at high speeds, and at very high speeds the aircraft might actually roll in the opposite direction of the pilot's input.



The FW-190s wings were extremely rigid.  Wing rigidity is a function of aspect ratio and construction.
 


The FW-190 had wings that had a fairly low aspect ratio, and were somewhat overbuilt.  Additionally, the wings were built as a single piece, which was a very strong and robust approach.  This had the downside that damaged wings had to be replaced as a unit, however.
 
Some spitfires were modified by changing the wings from the original elliptical shape to a "clipped" planform that ended abruptly at a somewhat shorter span.  This sacrificed some turning performance, but it made the wings much stiffer and therefore improved roll rate.



Finally, most aircraft at the beginning of the war had fabric-skinned ailerons, including many that had metal-skinned wings.  Fabric-skinned ailerons were cheaper and less prone to vibration problems than metal ones, but at high speed the shellacked surface of the fabric just wasn't air-tight enough, and a significant amount of airflow would begin going into and through the aileron.  This degraded their effectiveness greatly, and the substitution of metal surfaces helped greatly.
 
Stability and Safety
 
World War Two fighters were a handful.  The pressures of war meant that planes were often rushed into service without thorough testing, and there were often nasty surprises lurking in unexplored corners of the flight envelope.
 

 
This is the P-51H.  Even though the P-51D had been in mass production for years, it still had some lingering stability issues.  The P-51H solved these by enlarging the tail.  Performance was improved by a comprehensive program of drag reduction and weight reduction through the use of thinner aluminum skin.



The Bf 109 had a poor safety record in large part because of the narrow landing gear.  This design kept the mass well centralized, but it made landing far too difficult for inexpert pilots.



The ammunition for the massive 37mm cannon in the P-39 and P-63 was located in the nose, and located far forward enough that depleting the ammunition significantly affected the aircraft's stability.  Once the ammunition was expended, it was much more likely that the aircraft could enter dangerous spins.
 


The cockpit of the FW-190, while roomier than the Bf 109, had terrible forward visibility.  The pilot could see to the sides and rear well enough, but a combination of a relatively wide radial engine and a hump on top of the engine cowling to house the synchronized machine guns meant that the pilot could see very little.  This could be dangerous while taxiing on the ground.


 

This is an interesting topic.

Modern fighter aircraft have very little free space in them.  Almost every cubic centimeter inside is filled with something:


 


There are gigantic bays crammed full of electronics with just enough space around them to ensure adequate air circulation, and there's fuel stuffed into every available space to feed the thirsty jet engines. 
 

 
Second World War fighters are quite a bit more open inside.  Above is a shot of the inside of the rear fuselage of a Spitfire.  As you can see, there's a whole lot of nothing back there.
 
I'll skip a detailed derivation of it, but the Breuget Range Equation explains that the cruising range of an aircraft is a linear function of cruise airspeed, lift to drag ratio, specific fuel consumption, and the natural log of the fully fueled weight over the empty weight.  This looks sort of like the Tsiolkovsky Rocket Equation, and I suppose it's a distant relative.

So why not just cram every single corner of the fighter full of fuel?  That ought to do the trick!

Very simply, they couldn't.
 
Back in World War Two the designers didn't have the luxury of computer-controlled everything.  That means that, if the aircraft had multiple fuel tanks, the pilot needed to manually select which ones were feeding to the engine.  It meant that flight computers couldn't automatically re-trim the aircraft if the balance shifted in flight.  Also, they didn't have fancy fly-by-wire systems, so the aircraft had to be statically stable with the center of gravity in front of the center of lift:



Moreover, since we're talking about fighters here, the center of lift has to be fairly close to the center of gravity, or the fighter will suffer from pitch stiffness and the pilot will really have to pull hard on the stick to get the nose to move.  Again, the vast majority of WWII fighters relied on the pilot's muscles to actuate the flight controls, so having heavy control forces was out of the question.
 
All this together meant that the fuel tanks in a Second World War fighter could really only be placed close to the center of gravity so that consuming the fuel would affect the stability and trim of the aircraft as little as possible.  Ideally the ammunition for the guns would be near the center of gravity as well for the same reason.

On a typical WWII fighter the center of lift will be located somewhere a little bit back from the front quarter mark of the chord length of the wings.  Airfoils generally have their aerodynamic center around 25% of of the Mean Aerodynamic Chord, but the horizontal stabilizers push it back a little further.  The center of gravity will be in front of that.  So, basically, a designer would want the fuel tanks to be centered at about the leading edge of the wing.
 
That's the reason that most WWII fighters only have fuel tanks in the fuselage, often immediately behind the engine or under the pilot.  Surprisingly few have fuel tanks in the wings, given the amount of volume the wing represents.  Generally speaking the wings were already full of landing gear, guns and ammo, and sticking gas tanks in there wasn't worth the bother.  It may have been possible to put auxiliary fuel tanks in the wings further outboard of the guns, but this would have reduced roll rate at least until that fuel was consumed.  I'm not aware of any designs that did this, but that doesn't mean they didn't exist.

One big exception is the P-51 Mustang.  The P-51 had those wonderful laminar-flow wings that did everything except actually make the airflow laminar.  Laminar flow airfoils can be much larger for a given amount of drag than their conventional counterparts, and the P-51 had gigantically thick wings.  This meant that there was plenty of room for guns, ammo, landing gear, and a generous amount of fuel:


 
So, practically speaking, most designers were stuck with the amount of internal fuel they could pack under the pilot and behind the engine.

Increasing lift to drag ratio typically optimizes for aircraft with very smooth, cigar-shaped fuselages and long, skinny wings.  So, basically B-29 shaped sorts of things.  That synergizes well with optimizing for sustained turn rate, but as we've seen, optimizing for sustained turn rate conflicts with just about everything else.
 
Most WWII engines tended to have samey fuel efficiency, although the British sleeve-valve engines had a small edge in fuel economy.  The Soviets did try using diesel engines in bombers, but for a variety of reasons this didn't really work.  This may not have been a total loss; according to some sources the V-2 diesel in the... well, just about every Soviet medium and heavy tank was derived from a diesel intended for aircraft.  I've never seen the final word on whether that's true or not.  @EnsignExpendable, do you know?
 
Flying at higher altitude tended to result in better range.
 
At the end of the day, the best way to solve the problem was probably drop tanks.