sevich

I don't remember where I read it, but supposedly the 3rd Army did testing on sandbags as well as concrete and other materials that were being put on tanks.  They found that these improvised types of armor actually made shaped charge weapons more effective since they improved the stand off distance of the warhead detonation, allowing the particle stream to form a little further out from the armor plate.  This is why Patton ordered all Third Army tanks to remove any extra armor other than actual armor plate.  

Elements of Power describes Trump's involvement with the reduction in the F-35's price as a bit of clever showmanship that leverages the media's obsession with all things Trump to force a new perspective on a program that they've loved to hate.
By the way, Elements of Power is a heavyweight aerospace engineer.  I highly recommend his piece on energy maneuverability theory.

They do not.  The RF noise that Black Crow picked up was from the spark plugs, and diesels and turbines don't have those.

In fact, I'm not sure if this technique even works against all Otto engines, or whether it just worked against the ones that were common at the time.

We've had this link in the resources section for a while on TMEPS.  The engine was not "a standard AGT-1500," as the document explains, it had a new high pressure turbine rotor, new high pressure turbine cylinder, new recuperator, new power turbines, a new electronic control unit and a new auxiliary power take off.

It's related. There's a mathematical measure of how well a cross-section will resist bending, which I was taught as second moment of area (although bronez calls it area moment of inertia earlier, same difference). Using the same axes as my earlier post, when bending in the x axis with a force in the y axis you double integrate y^2 over the y axis and the z axis. This, combined with the stiffness of the material and the bending moment at that particular point, gives the curvature; and integrating the curvature twice along the x axis dives you the displacement (the first integral gives the angle the beam is at, the second the displacement). So for a rod without a constant cross section, the thicker bits have less curvature and the thinner bits have more curvature. The second moment of area scales with the width (in the axis of the bending force) cubed multiplied by the other width, so a wide structure (like a birdcage) is much much stiffer for the same weight as a thin structure (like the wire the cage is made from).
 
In practice, the maths for beams with constant cross-section is fiddly and a pain, and non-constant cross-sections even worse, so everyone hides the maths in a computer FEA model

For shiggles I threw together a few rods in solidworks and used the SimulationXpress default settings to judge stiffness. 3 rods: one smooth (10mm r 800mm l); one ribbed (11.5mm r with a 1.5x1.5mm revolved cut every 3mm, so just like the original rod with a series of 1.5mm square rings with 1.5mm between each, 800mm l); and one with a thread (11.5mm total diameter, with a 3mm pitch square thread cut 1.5mm deep - so like the second rod only with threads instead of a series of grooves).
All were fixed at one face and had 20N applied parallel to the other face, material assumed to be tool steel. Results were:
1) Solidworks hates threads. It took 1s for the smooth rod, 22s for the ribbed rod and half and hour for the threaded rod
2) Unsurprisingly, ribs or threads do improve stiffness. Max displacement was 2.139mm for the smooth rod, 2.001mm for the ribbed rod and 1.994 for the threaded rod. This is an improvement, but I'm not sure if it corresponds to a 46% improvement in second moment of area

Survivability
Armor protection of the M1 is very interesting subject because it's not entirely well understood what happend with requirements when US joined the British "Burlington" program.
One is certain, that original requirements for 115mm APFSDS at 800m and 127mm HEAT warhead over frontal arc, are requirements for early armor types developed by BRL, and are not connected with later development.
Recently the CIA declassified some drawings of the original M1 armor.

This confirms that vehicle was protected by "Burlington" type armor. Similarities can be observed when we compare these drawings with the British drawings of the "Burlington" armors developed for Chieftain. I strongly recommend here articles by Polish historian Paweł Przeździecki.
http://wceo.com.pl/images/Dokumenty/WBBH/PHW/PHW_3_2011.pdf  -> PDF reader page 112.

http://wceo.com.pl/images/Dokumenty/WBBH/PHW/PHW_4_2011.pdf  -> PDF reader page 106.

Another interesting factors is that declassified document that says one of the armor types used in M1 turret, offered KE protection = 400mm RHAe and CE protection = 750mm RHAe at front.



Another document is also interesting because it says.


This fragment is very interesting when taken in to account later fragment of this post when I will talk a bit about armor types. Because it makes situation confusing. We know that BRL tested two armor types, BRL-1 that is assumed to be the original M1 armor, and heavier, better performing BRL-2. The question is, are both armors related? And what type of armor was used by M1IP variant, did it used simply the same armor as M1, and only improvement was added through increasing turret front armor thickness? Or perhaps M1IP used the same armor type as M1A1?
When it comes to the armor itself, this is based on my estimations and measurements I made on the real thing.

 
Besides that:

Hull sides over crew compartment - 40mm + 30/40mm = 70-80mm.
Hull sides over engine compartment - 40mm.
Hull sides around suspension attachement points - 40mm.
Hull rear - 40mm.
Upper front plate and drivers hatch - 50mm at 82-85 degrees = 359.26/573.69mm.
Turret roof front - 50mm at 82-85 degrees = 359.26/573.69mm.
Turret roof around hatches and turret bustle - 25mm.
Engine compartment roof - 25mm.
Hull belly - 25mm.
Heavy ballistic skirts - 70-80mm.
Non ballistic skirts - 5-10mm.
 

Before we move to the armor itself it's also worth to note something about hulls and turrets.
Because there is no official classification I needed to create one by myself. However there are very clear difference between various generations of tank variants.
Turrets:
Type 1 "Short Turret", used only in original M1, it have thinner frontal armor that have effective armor thickness ~700-750mm, and a bit different roof over turret bustle with 3 cutouts for blow off panels.
Type 2 "Interim Long Turret", used only in M1IP variant, have thicker frontal armor, effective thickness ~800-900mm (Steven Zaloga in one of his books said that armor thickness was increased by ~200mm), no other structural changes.
Type 3 "Long Turret", this is the final turret variant used in M1A1 and M1A2, older turrets can't be upgraded to this variant due to significant structural changes thus all these turrets are new builds, even if M1 or M1IP was upgraded to M1A1 or M1A2 standard. Front armor effective thickness is also ~800-900mm.
Hulls:
Type 1 used in M1 and M1IP, it lacks the overpressure NBC protection system, probably have some minor differences with the next type. Front armor effective thickness where special armor is mounted is ~650-700mm and did not changed till this day.
Type 2 used in M1A1 and M1A2 variants, major difference is that overpressure NBC protection system is present, some other minor differences are present depending on tank variant, Type 1 hulls can be upgraded to Type 2, however it requires complete disassembly, cutting and welding in some places.
About special armor itself, there were several types used:
BRL-1 (1980) used in original M1.
BRL-2 (1984) used in M1IP and M1A1 (Not certain!).
HAP 1st generation (1987/1988) used in early production M1A1HA.
HAP 2nd generation (1990) used in late production M1A1HA as well as new M1A1HC and M1A2.
HAP 3rd generation (1999/2000) used in M1A1SA, M1A1FEP, M1A2SEPv1 and M1A2SEPv2 (there is possibility of some upgrades for this armor in 2010+ period of time).
NGAP/NEA (2017+) used in newest M1A2SEPv3.
EAP (?) used in all export variants for Arab states.
BRL stands for Ballistic Research Laboratory, these were designations of lighter and heavier armor variants based on British research, that were developed by BRL in US, it's assumed that BRL-1 was for original M1, while BRL-2 was improved, heavier version for M1IP and M1A1 however as mentioned before, this is not certain.

HAP stands for Heavy Armor Package that uses components made from depleted uranium alloy, we know that there are at least 3 generations of this armor, there is also special variant for Australia where depleted uranium was replaced by something else, perhaps tungsten alloy, but Australian documents I found suggest that it's protection levels are equal to 3rd generation Heavy Armor Package, originaly it was said this type of armor is used in turret front only, however I found mentions in official sources saying it is used also in hull front and turret sides.

EAP or Export Armor Package is meant for non NATO/Close allies (like Australia) of the US, used in tanks provided to Arab states, some theoretize it might be equivalent to BRL-2 but it's probably heavier and offer better protection, but lower than HAP armor package.
One more important thing to note, today we also know that at least the newest M1's also uses Titanium alloy in their armor and several other components.
http://c.ymcdn.com/sites/www.titanium.org/resource/resmgr/2005_2009_papers/Gooch_Final_2007.pdf
http://c.ymcdn.com/sites/www.titanium.org/resource/resmgr/2010_2014_papers/GoochWilliam_2010_MilitaryGr.pdf


There are also two types of serial numbers. One for the turret, and one for the hull, serial numbers on turrets says us what type of armor vehicle uses, and on the hull where it was made. X will equal digit.

Turret:

XXXX - BRL-1 or BRL-2 armor package.
XXXXU - Heavy Armor Package.
XXXXM - Heavy Armor Package (some US tanks have it, don't know why that change in letter).
XXXXA - Heavy Armor Package variant for Australia.
XXXXE - Export Armor Package for Arab states.

Hull:

XXXXD - Tank was made in Detroit Tank Arsenal.
XXXXL - Tank was made in Lima Army Tank Plant/Joint Systems Manufacturing Center.

When it comes to armor itself, today we know it is indeed some type of advanced NERA or NxRA armor, however we only know more or less the structure of the turret side armor, and still only of older variant probably M1A1HA or M1A1HC.

This is how probably turret side armor over crew compartment looks like.

And this is how turret bustle side armor looks like.

And it makes sense, on one of the photos we can see some turrets after armor replacement/upgrade work in Joint Systems Manufacturing Center Lima, Ohio. We can notice that their frontal and side armor was replaced, but turret bustle was untouched.

With such evidence we can assume that turret armor is only replaced over crew compartment, while turret bustle armor might be untouched, and it makes sense from armor protection distribution point of view, where majority of protection increase and thus weight increase we want around the crew and for vehicle frontal 60 degree arc.

Here some more sources.

And here US Army Weapons Hand Book 2016.

https://www.army.mil/e2/c/downloads/431298.pdf

At page 14 in PDF reader we can read for M1A1SA and M1A2SEP "Survivability improvements include frontal armor and turret side-armor upgrades.", of course term "frontal armor" means most likely both turret and hull, and we have confirmation of side turret armor upgrades. And it also seems that M1A1SA and M1A2SEP shares the same armor type, which makes sense because due to reduced costs, simplicity etc. at one specific time you manufacture only one specific type of armor and it makes sense for MBT's even in various but not that much different variants to share the same armor protection. USMC M1A1FEP is also technically equivalent to US Army/ARNG M1A1SA with some minor differences, thus it's safe to assume that it also shares the same armor.

Good question is how exactly DU is applied to the armor design? We do not know, but perhaps it might be part of the NERA array itself like in this prototype British armor (perhaps one of several armor types developed within "Burlington" program?) which uses DU alloy plates with polycarbonate as a reactive layer?



When it comes to armor steel alloys used in the vehicles construction and armor, most likely these standard NATO steel types are used with such range of thickness and hardness.




Another thing is that M1's armor, like all modern 3rd generation MBT's armor is modular or semi modular, which makes it's replacement or repair relatively easy, quick and cheap. Another factor is that M1's turret and hull have very simple geometrical shapes making both manufacturing relatively simple, quick and cheap, as well as armor replacement/repair will be such relatively simple, quick and cheap task.

This also means that frontal protection is uniform for both hull and turret, and have very small weak zones.


Some additional protection over hull front is added by massive fuel tanks (visible on one of the drawing above), Israeli data says that 70mm of fuel is equivalent for 10mm of armored steel, thus we can assume that front hull protection where fuel tanks are is significantly increased.

However the largest improvement in protection will be made in M1A2SEPv3, photographs of one of the 9 prototypes shows us vehicle with massive weight simulators on turret front and hull front. This prototype still uses 3rd generation HAP armor package because it was originally M1A2SEPv2 converted in to M1A2SEPv3 prototype.


Each turret cheek have 4x welded plates, each looks to be ~50mm thick at most. Hull front have 3x welded plates, also each looks to be ~50mm thick at most. This means very significant weight increase over the previous generation armor, so we can assume also very significant protection levels increase over the front. There are also weight simulators packs welded to the turret roof, two have 4x 50mm plates and one have 3x 50mm plates.

http://www.dote.osd.mil/pub/reports/FY2015/pdf/army/2015m1a2sep3.pdf

Some additional informations about vehicle survivability improvements can be found here.

Final armor protection improvement are M19 ARAT-1 and M32 ARAT-2 Explosive Reactive Armor modules.

M19 ARAT-1 is modern, multilayer explosive reactive armor, which might have some sort of anti-tandem warheads capabilities.








From these photos we can see angled layers of ERA inside the module, and perhaps some sort of passive component?

Also to M19 modules, can be attached M32 modules.


It's very unusual design for ERA, and it's interesting it can be combined with M19 modules in to a single, multilayer type of ERA protection. M32 modules can also be attached alone to the turret sides.

In such configuration both turret and hull sides have very good, right ERA cover. The system is modular and can be arranged per need.

Of course besides it's armor M1 have other survivability meassures, primary one is mentioned earlier complete isolation of the main gun ammunition storage. It needs to be noted that the biggest tank and crew killer is not the enemy ammunition penetrating the armor but own ammunition cooking off.

The original M1 and M1IP had such ammo storage:

Turret bustle ready rack - 22 rounds.
Turret bustle semi ready rack - 22 rounds.
Turret basket floor armored box - 3 rounds.
Hull ammunition rack - 8 rounds.

M1A1 and M1A2 have such ammo such ammo storage:

Turret bustle ready rack - 17 rounds with old type of racks and 18 with new type of racks.
Turret bustle semi ready rack - 17 rounds with old type of racks and 18 with new type of racks.
Hull ammunition rack - 6 rounds.
 
 




Blow off panels and ammo racks in turret are connected, so if possible during ammunition cook off, blow off panels will be able at least to some degree pull out ammo racks with burning ammo outside, thus minimizing the damage.



These are armored blast doors for the hull ammunition magazines.



Hull blow off panels are placed in top (we can see large opening for main blow off panel) and belly of the hull (we can see two smaller openings for blow off panels).

In future another upgrade that will increase M1's already fantastic protection and survivability will be hard kill active protection system, however and it's not widely known, M1's had in the past, but not used often a soft kill active protection system or actually two, the AN/VLQ-6 and AN/VLQ-8, both are sort of IR dazzlers which work similiar to Russian TShU-1-7 Shtora-1 and Ukrainian Varta.





In future also M1 will be equipped with Hard Kill Active Protection System, most likely Israeli Trophy HV system as a mid term solution before new Modular Active Protection System will be ready.
 

And finally, another part of survivability improvements are multispectral camouflage nets and covers.

US Army is purchasing Saab Barracuda MCS.



And also uses a set of camouflage nets.

HEMP lacks a nose fuse, so should have better performance against reinforced targets than either of the israeli rounds. The lack of submunitions ought to reduce cost as well. HEMP only has 3 modes, I can't see much similarity at all with the mistakes of APAM.
https://web.archive.org/web/20170127175609/http://www.benning.army.mil/armor/eARMOR/content/issues/2013/APR_JUN/Articles/PeraltaArticle.pdf
Look at page 24, no sabot

Number of individuals under the age of 1 year on California's gang member database: 42
Number of people shocked by this level of incompetence by the state of California: 0
 
http://www.voiceofsandiego.org/topics/public-safety/scathing-audit-bolsters-critics-fears-secretive-state-gang-database/

It gets worse:
https://www.theatlantic.com/science/archive/2017/01/inception-but-with-parasites/514211/
Like russian dolls, but horrifying.

A Decidedly Brief And Altogether Inadequate History And Description of The Small Caliber High Velocity Ammunition Concept: A Treatise On Extended Nomenclature And Extraneous Verbosity For The Individual Highly Valuing The Immediate Temporal Period

(THIS ARTICLE ASSUMES FAMILIARITY WITH BASIC SMALL ARMS TERMINOLOGY ON THE PART OF THE READER)

"Small Caliber; High Velocity" is nothing more or less than what it says. Relative to the contemporary norm, ammunition and the guns that fire them should be smaller caliber, while also achieving higher velocity; doing both will increase performance while decreasing weight, recoil, and materiel usage.

Why is this desirable? In brief:
 
1. The bullet weight of a cartridge is a major driving factor in that cartridge's characteristics. A lighter bullet weight is, from the perspective of the shooter, better than a heavier bullet weight. Lighter weight bullets will induce less recoil, all things being equal, than heavier ones. The bullet of a rifle cartridge also typically makes up a third or more of the total weight of the round; reducing bullet weight is a good way to reduce the weight of ammunition.
 
2. A faster bullet produces a superior trajectory to a slower one. Less adjustment is needed for distant targets, and the error possibilities for incorrect range estimation are lower. Contrary to popular belief, 5.56mm produces an excellent trajectory for its size; in fact, I have a hard time noticing a difference between it and 7.62mm NATO until about 800 yards. Ballistic tables bear this out; along its supersonic flight range, 5.56mm has a very flat trajectory. PEO Soldier sets 5.56mm's Maximum Effective Range when fired from an M4 at 500m. Compared to that, 7.62x39 lags behind by about 120m, despite having a very similar bullet shape, sectional density, and ballistic coefficient. Note that 7.62x39 produces 80% of the velocity of 5.56 when fired from the same barrel. I created a graph to illustrate the relationship velocity and ballistic coefficient have in terms of informing trajectory. It plots the ballistic coefficient necessary to produce the same drop at 500m as a .151 G7 BC bullet fired at 2,970 ft/s. Note that below 2,700 ft/s, a tremendously high BC is needed to achieve this level of performance. In short, muzzle velocity is the overwhelmingly primary agent in producing a better unadjusted sight trajectory at normal and even extended ranges. If sight adjustment is assumed, this changes, but that is not relevant for the discussion of modern military small arms.
 
3. For a given trajectory and specific energy*, a smaller-caliber round will be lighter and smaller than a larger-caliber counterpart. This is only true within a certain bound of performance, but the performance needed from modern military rifle ammunition lies well within this bound.

4. Sectional density, a major factor in both penetration and drag, can be maintained as caliber is reduced relative to length. Sectional density is calculated, in common discussion, as mass/diameter^2. Imagine a cylinder .5" in diameter that is 1" long, made from steel. Now imagine another cylinder, also made of steel and still 1" long, but now .25" in diameter. Both cylinders have the same sectional density, but the second cylinder is one quarter the weight of the first.

*Specific energy, .5*mass*(velocity^2)/(diameter^2), is an important metric in approximating target penetration characteristics when assuming homologous bullet design.
 
Now, how is this bounded? Well, in a couple of ways:

A. In conventional rifle ammunition, the projectile diameter and bore diameter are both coupled together. Change the diameter of the bullet, and you need a wider or thinner bore to accommodate it. Because of this, you reach a limit where so much powder is being used to try to attain a higher muzzle velocity through such a small bore that the fluid flow rate is limited by the extreme necking down of the cartridge case. Therefore, for normal modern rifle ammunition, muzzle velocity does not typically exceed 4,600 ft/s. However, if bore diameter and bullet diameter are decoupled (as through a sabot), or unusually light projectiles are used, velocities at the limit of nitrocellulose's capability are possible, out to around 6,000 ft/s.

B. Military ammunition has other concerns that limit it further. One is the barrel wear of the ammunition; militaries are economical organisms, and they do not want to be throwing away barrels too quickly. Because of this, and because trajectory and weight gains are minimized beyond around 3,500 ft/s, velocity is limited. Another concern is weapon overheating: Beyond a certain temperature, rifles lose a great deal of their accuracy; thus ammunition is maintained below the heat flux threshold for a desired sustained rate of fire for the rifle. This doesn't limit velocity as much as it limits over-boredness, the ratio of the caliber squared over the chamber volume. A small caliber, high velocity round will want to be as overbore as possible, so this does limit the concept for military use.

C. Spin-stabilization only works out to a point, and that point is "about" a 7 caliber length-to-diameter ratio. For military use, the limit is closer to 5 calibers due to stability being absolutely essential from a wide variety of barrels and conditions. Remember our dieting cylinder example up there? Once it gets down below about .18" in diameter, it will begin to have problems.

Now, if one decouples the bore diameter from the projectile diameter, and drag-stabilized, instead of spin-stabilized the projectile, they would run into very different limits. Research into this area, which began in the early fifties with the SALVO project, resulted in micro-caliber finned flechettes fired at velocities up to 5,000 ft/s:
 

 
These high velocity flechette rounds weighed very little, while producing exceptional penetration and flatness of trajectory. So, they can be considered the ultimate evolution of the small caliber, high velocity concept.
 
A detrimentally brief history of SCHV:

SCHV has been around for a while. .45-70, .30-40 Army, and 5.56 NATO were all considered "small caliber" and "high velocity" for their day; all of the principles I describe above were known well before the 1870s. However, the term "small caliber, high velocity" doesn't really get used in official literature until the 1950s when experiments with .22 caliber military rifles really took off. In the context of today, small caliber high velocity refers to a cartridge optimized for low weight and a flat trajectory out to 300m, typically with a caliber under .24" and a velocity above 2,800 ft/s. However, it's important to remember that caliber does not inform performance; A 6.5mm cartridge may perform much the same as a 5.56mm one, if the velocity is high enough and the bullet weight low enough. It's better, then, not to group ammunition sharing a bullet diameter together, but rather group together cartridges that share similar performance characteristics.

I've covered the GPC before, several times on my blog. Feel free to click through these links and read that material, too:

The Case Against a General Purpose Cartridge
 
The New Caliber Mafia

The General Purpose Cartridge Revisited

So this is a very interesting quote from the M1919 website I posted earlier. 
 
Saginaw Steering Gear Division of General Motors applied their considerable production 
know how by introducing the concept of casting some of the M1919 parts using a perlitic malleable iron alloy previously used to cast hard to machine interchangeable auto parts.

Saginaw trade named this class of casting materials "ArmaSteel".  The Ordnance Department used several different alloys to cast parts for weapons, however over the years all of them are commonly referred to by Saginaw's trade name.

Innovations like this, previously unknown in Government operated manufacturing facilities, lowered the cost of a single M1919A4 from a contract price of just over $650 to less than $60 in four years.
 
 
 
 
When was the last time you heard of anything like that on a government contract?  
 
Chrysler did a similar thing with the M3/M4 Tanks, they improved the buildability of the SHerman so much they gave money back, millions of bucks, to the government. 

On the earlier tanks, yes. But on the T-80UD and late T-72B/T-90 hull and turret armor follow the same technology, the shape of the inserts was just adapated to the shape of the hull.
 
 
Some sources suggest so, other sources however disagree. There are at least five M1 Abrams tanks with DU armor in the hulls located in the US Army schools - but it seems possible that DU armored hulls were not adopted in US Army service (yet).
 

 
From a document of the US Army TACOM Life Cycle Management Command Safety Office to the  U.S. Nuclear Regulatory Commission.

Why would they be so hesistant? aside from the fact not all of the documents are actually written by the CIA but were simply deemed safe to declassify by them, these aren't even close to the latest models of Abrams, the timeline would put them at the very first models in the early 80s back when the cold ward was still a thing, chances are alot has changed since them. And besides, much has been revealed unwittingly regarding the armor layout of many sections of the current models of Abrams by simply looking at battle damaged photos of them in Iraq.