Jump to content
Please support this forum by joining the SH Patreon ×
Sturgeon's House

Collimatrix

Forum Nobility
  • Posts

    7,230
  • Joined

  • Last visited

  • Days Won

    192

Collimatrix last won the day on March 19 2023

Collimatrix had the most liked content!

3 Followers

Profile Information

  • Gender
    Not Telling

Recent Profile Visitors

20,403 profile views

Collimatrix's Achievements

Advanced Member

Advanced Member (3/3)

3.8k

Reputation

  1. The sabot design of the ASCALON rounds seems sub-optimal to me, though it is possible that some advance in composite technology has changed what the optimal shape is. It seems like they're trying to minimize the overall length of the rounds, but that this will come at the expense of too much parasitic sabot mass.
  2. As expected, Nvidia announced their 4000 series GPUs at the 2022 GTC Keynote: Not too many surprises here. Improvements in rasterizing performace look solid while improvements in raytracing look downright impressive. Of note are all the new features Nvidia keeps pushing with their GPUs. Nvidia has a really gigantic R&D budget, so they are nearly always the leaders in new software/hardware tricks while others follow. I'm really not digging the prices, although the power consumption for the base models looks slightly less insane than what a number of board partner leaks had suggested. I guaran-fucking-tee you that the weaker of the two 4080 models was originally supposed to be the 4070.
  3. AMD just officially showed off their new Ryzen 7000 series CPUs. They should be available by September 23. How time flies! Performance for these CPUs is on the high end of what leakers and analysts were estimating. However, it remains to be seen exactly how these perform in games vs. the handpicked average shown off in this presentation. We should be seeing actual benchmarks soon. It also remains to be seen how this will compare with Intel's Raptor Lake 13th generation CPUs. Rumors and leaks suggest that, at least in single-core performance, the offerings from the two respective companies will be very close in performance. TSMC's 5nm node looks quite impressive here, as it apparently allows for blistering 5.7GHz max boost frequency. In an interesting reversal, the AMD CPUs will require a new motherboard with the new AM5 socket. Intel has confirmed that their upcoming 13th generation chips will use the same socket as the previous models, which will make upgrading easier for people with existing 12th generation Alder Lake systems. The highest-performing AMD CPUs for this generation will be less expensive than had been anticipated. This suggests that their production efficiency is very good, and also that they're gunning for more market share. However, because these new CPUs will require a new motherboard and new DDR5 RAM, making a new system using them will still be expensive. This rumor suggests, however, that AMD will decisively take the performance crown in Q1 of 2023. Their vertically-stacked vcache will be back, and at least according to this source, it's considerably improved over the implementation in the Ryzen 7 5800X3D. The CPU frequency penalty for the vcache is lower, and the performance boost is higher. Again, the proof will be in the pudding. I do also wonder what pricing and availability will be like. The chiplet strategy has helped AMD's CPU production efficiency overall, but the more components they add to each chip the more vulnerable they are to various global supply chain disruptions that have been going on at least since the 2019 South Korea / Japan trade war, and which were accentuated by COVID-19 and the Ukraine War.
  4. Do they have any more pictures of that early sabot design? It's quite unusual.
  5. That's magical thinking. Unless the ASCALON is firing ammunition that burns at lower pressure than what the breech can handle, being lower pressure doesn't imply more growth potential. That would imply that they're making the initial gun much stronger, which means thicker and heavier, than it needs to be for the initial ammunition offering. That makes no sense.
  6. I was just about to post that tweet. 20MJ at the muzzle, I wonder what this means. That's quite a bit more than was stated earlier. Are they including the sabot energy? 140mm straightwall does make some more sense if they are developing an NLOS round for it.
  7. The interface between the sliding wedge of the breech block and the breech ring is what is improved. As you can see, on the M256 the shoulder in the breech ring that the sliding wedge rests against is a single element that's more or less a square corner (albeit radiused). In the Rheinmetall 130mm weapon you can see that the interface between the sliding wedge and the breech ring has two layers, and that it's sort of a rolling teardrop shape with a much more generous radius. It's not unlike what the US was looking at with the XM360: It's been known for a very long time that this sort of design of sliding wedge is stronger, but it's traditionally been considered too much of a pain in the ass to manufacture to be worth it. Perhaps computer stress modelling and improved manufacturing technology have changed that. By reducing stress I mean it reduces stress in the metal of the breech mechanism. The stress at any given point in the breech ring and the breech block has to be lower than the yield strength of whatever uber-steel it's made out of so the gun isn't permanently deforming itself with each shot. Ideally the stress should be quite a bit lower in order that the mechanism has good fatigue life. When the original 120mm Smoothbore was designed (late 70s) I doubt that full computational finite element analysis was possible; the computers were too pathetically weak back then. The stress analysis was probably done with some computer modelling, but also good old fashioned rules of thumb and photoelastic stress simulations: It is possible to modulate pressure within the tube with propellant design, but to what end? Yes, pressure in the breech is what causes the stress on the locking elements. Pressure in the breech is also what makes the projectile go downrange. Keeping the peak recoil force within reasonable bounds is important as well, so I suspect that the recoil system on the 130mm will need to permit the gun to travel further than the system in current 120mm armed vehicles. However, increasing the travel of the gun during recoil doesn't really change the width of the gun system that much. Look at how cramped the gunner's position is in an Abrams, which is supposed to be one of the MBTs with more generous elbow room: That position, by all accounts, kind of sucks, but if the gun gets even a few centimeters wider it's going to suck way more.
  8. Their overall design rationale reminds me a lot of the conceptual studies in British tank guns that led up to the 120mm L11. Lower breech pressure means that the breech, ceteris paribus can be narrower and thus take up less room in the turret because the breech ring and barrel don't need to be as thick. This also makes stabilization a little easier because there's less steel for the stabilizer to have to wrestle with. Lower peak pressure also makes life a little easier for the ammunition designers because the interface between the sabot and the dart is experiencing less peak force. The problem with this line of thinking is that it's really hard to get the raw performance. Kinetic energy of the projectile is the integral of the pressure at the base of the projectile swept along the volume of the bore. For a given mass of propellant, higher pressure guns have better thermodynamic utilization of the propellant. In small arms, higher peak pressure also gives more consistent internal ballistics and thus accuracy, but I am not sure if this is a major factor in tank guns. The Rheinmetall 130mm has the same cartridge base dimensions as the 120mm: So the increase in breech thrust against the breech block and the stress in the firing chamber and breech ring should only be greater by (approximately) the percentage increase in pressure. On top of that, the breech designs Rheinmetall has shown have a more sophisticated wedge design that existing 120mm guns which should provide better distribution of the firing loads and thus lower peak stress: There may also have been metallurgical improvements in gun breech materials in the... what, half century since the 120mm smoothbore was invented? So the width increase of the 130mm vs. the 120mm may be very small. The gun will probably need greater recoil travel and may need to be mounted further back in the turret, so it is not space-neutral or anything like that. However, with the current manned tank turret design of placing the gunner, gun, and commander abreast (or loader, gun and gunner in designs with a flesh loader), the width of the gun breech is dividing the turret right down the center and determines to a large degree how much elbow room is left for the crew for a given turret ring diameter. So, given that the Rheinmetall design is more mature, more powerful, and shouldn't be too much wider than the existing 120mm smoothbore, the advantages the Ascalon offers seem poor by comparison.
  9. No. The stabilizing lift force provided by the fins is a function of angle of attack times fin area times airspeed squared. The overturning moment acting on the rod is a function of the moment arm between the aero center and center of gravity times airspeed squared. The stabilizing moment provided by the fins is a function of their stabilizing lift force times the moment arm between the fins and the center of gravity. Thus, as long rods have gotten longer and longer, these competing effects have more or less canceled out and the fins have stayed about the same size. Because the stabilizing force provided by the fins is a function of airspeed squared and the overturning force is also a function of airspeed squared, a long rod penetrator that's stable at one airspeed is stable at any airspeed. The only exception is the transonic where lift coefficients and aero centers can jump around, but that's pretty much academic because an APFSDS long rod going transonic velocities isn't going to be killing very much.
  10. So... I have a question, and I don't have an answer. Right now, in English-language "respectable" news sources, I am seeing a lot of stories of Ukrainian bravery and staunch resistance and heavy Russian losses. I am pretty sure that some of these stories might even be true. But who exactly is collating these stories and publishing them to English-speaking audiences? Does Ukraine have an incredibly slick media interface to their American allies that knows exactly what buttons to push? Or am I watching mostly American self-deception? I am increasingly convinced it is the latter.
  11. As for what a 1990s tank would realistically look like, by the 1990s most tanks were really samey. Powerplant: The earliest tanks with diesels were experimented with in the 1930s, I believe either the Japanese or the Soviets were the first. By the 1940s the advantages were obvious, but de-rated aviation gasoline engines were reliable and already in mass production, so many countries stuck with those. I'm less clear on the rationale for the Germans keeping gasoline motors as theirs were not aeroderivative. In any case, there actually was a German tank diesel program, it just went nowhere. By the 1990s there were pretty much two realistic possibilities for a tank powerplant; either a turbodiesel or a gas turbine. 1990s MBTs are about half armor by weight, so they're very sensitive to the compactness of things. Turbocharged diesels don't have amazing power density, although with a lot of careful engineering they can be made competitive, but they have very low fuel consumption and lower waste heat rejection requirements than gasoline engines. Once you factor in the volume of the engine plus the volume of the fuel plus the volume of the cooling fans, and the strategic mobility advantage the fuel-sipping diesel, it's definitely coming out ahead of the gasoline motor. Gas turbines do not scale down particularly well. Very large gas turbines like the 33,000 horsepower Rolls Royce WR-21 naval gas turbine in the Type 45 destroyer achieve 42% thermal efficiency, which is like middling efficiency by diesel standards. A gas turbine that will fit inside of a tank is much less efficient; realistically about a match for a gasoline engine in terms of specific fuel consumption when it's at design point and much worse if it's idling or doing any kind of stop and go. Gas turbines also need beefier air filters than diesels due to much higher mass airflow through the engine. However, there are still a number of advantages that must be taken into consideration. Gas turbines are (very nearly) completely self-cooling, so while there will still need to be cooling fans to keep the transmission cool, the total powerpack losses to cooling power will be smaller and the ballistic windows from the ventilation will be much smaller. Gas turbines with a free power turbine (which is most of them) have a very different torque/RPM characteristics from a diesel; they produce max torque at their lowest RPM and max power at their minimum torque. These are very favorable characteristics if you want to keep the transmission small (although the Abrams' XR-1100 transmission was, as I understand, designed to work with both the AVCR-1360 and AGT-1500 so it likely does not take much advantage of this effect). Gas turbines are easier to start in the cold. Gas turbines have very little vibration because their moving parts rotate rather than reciprocate. Gas turbines are actually multi-fuel, no questions asked and no mucking around with adjusting the engine to suit the fuel. The Brayton cycle uses continuous, constant-pressure ignition which simply does not care about octane numbers or cetane numbers. Finally, it's easier to design gas turbine fuel burners so they produce very little smoke than it is to ensure that a diesel produces very little smoke due to the much different fuel burn stoichiometry of a gas turbine. It should be noted that not all gas turbine designers have actually succeeded in doing so, however. A gas turbine good enough for a tank would be roughly similar to a turboshaft for a helicopter, albeit tweaked more for better fuel consumption than for absolute power to weight ratio. The list of countries that can design very good turboshaft engines is quite short, but then so is the list of countries that can make high specific power diesels. If tank-sized gas turbines performed as well as ship-sized ones this would be no contest, but they don't so either choice is competitive and it's pretty ambiguous which is "best". But most countries in the world realistically do not have the luxury to pick and choose between a top of the line diesel and a top of the line turbine. Interestingly, the UK is in a position to make such a choice and they still managed to fuck it up somehow by fielding a tank diesel that's 300 horsepower short of its stablemates. The French hyperbar engine is a turbocharged diesel, just tweaked for very fast throttle response and compactness at some expense to efficiency. Armament: By the 1990s, advances in digital fire control systems largely rendered gun-launched missiles obsolete. There was probably still a case for them as a sort of long-range precision round for swatting at helicopters and the like, but that role could also be filled with something like M830A1. There were various flirtations in the mid Cold War era with sorta-kinda howitzer like armament for tanks in the form of medium pressure guns and gun/launcher hybrids, but by the late 1970s there was basically a consensus amongst all sensible people that the tank armament of the future would either be the Rheinmetall 120mm or would look a lot like it. Even British engineers were aware of this: In any event, the Soviets taking their toys and going home meant that the world did not suddenly fill with various super-tanks, and tank lethality ended up being more economically improved by advances in ammunition design rather than arming the tanks with larger guns. You can't go too much larger than current 120mm without requiring an autoloader.
  12. As LoooSeR said, context is important. During the 1940s, tanks were simple enough that relatively small countries could design and field reasonably competitive designs on their own. The expertise required for tanks largely overlapped with either other armament industries (tank guns were often adapted naval, AA guns, or field artillery and the engines were often modified aircraft powerplants), or civilian heavy industries (much of the casting/welding and transmission design could be readily adapted from car/train/ship making industries). By the 1990s, however, tanks were much higher tech and a lot of that tech was much more tank-specific. It should be possible to adapt a helicopter turbine or heavy prime mover engine to work in a tank. Fabrication of the hull could still probably be done with expertise from other industries. Production of the special armor packages, transmission and running gear would require tank-specific knowledge but not necessarily tank-specific industry. Production of the gun, fire control systems, and other combat electronics would by that point require very specific knowledge and would overlap relatively little with too many other things already in production if it were a nation's first tank. I think it's instructive to look at the smallest/poorest countries that have produced their own tanks. Romania was able to produce the TR-85, albeit in somewhat limited quantities, and they didn't design their own gun, and the turret and hull design are at least based on the design of the T-54/55 albeit very heavily modified. As far as I can tell they did design their own engine and transmission, which is quite impressive, but this took some time and all the while they were cribbing notes off of foreign designs. No shame in that; high specific output diesels are not easy to design. Israel designed the Merkava, which has a completely original hull and turret design, locally designed suspension and tracks, and locally designed special armor packages and fire control on the later models. The engine is either US or German designed, and the transmissions have been US, German or Israeli designed based on the mark. The gun was a straightforward clone of the M68, and later a locally designed version of the German 120mm smoothbore. Both of these guns are compatible with the wide range of ammunition in either caliber, although Israel has a local ammunition industry capable of designing and producing its own tank gun ammunition (which in some cases has been widely adopted outside of Israel). South Korea has produced two MBTs locally, the K1 and K2. The former had a great deal of assistance from Chrysler, but the latter appears to be a largely local effort. Early K2s had a German designed engine and transmission, but these are eventually to be phased out and replaced with locally-designed equivalents. I believe the tracks are German-designed. Not sure about the suspension. The armor packages and fire control system are locally designed and manufactured. The gun is some sort of version of the German 120mm, although again South Korea is capable of designing and producing their own ammunition. Turkey, which has roughly the same size economy as South Korea if we discount their current economic woes, has had a much harder time developing their own MBT. Despite considerable help from South Korea, they have struggled to develop their own engine and transmission and are currently dependent on political good will from Germany if the project is to go forward quickly. I don't want to give the impression that Turkey has a weak local manufacturing sector or is a stranger to high tech industries. Neither is true; they are actually capable of producing their own helicopter gas turbines, combat UAVs, missiles, and a variety of other quite challenging materiel. Turkey has, current monetary woes aside, a well diversified and fairly well developed economy. They're just not a match for South Korea, which has an extremely well-developed heavy industry and electronics sector relative to the country's size, natural resources and population. Israel has an even smaller population and GDP, but their defense industry is outrageously well-developed for a country of that size for some mysterious reason, and there is abundant local expertise in the design of complex weaponry. So, any country that is plausibly going to mass-produce a 1990s tech-level tank (and let's be honest, that's not dramatically different than a 2022 tech level tank) is going to need a fairly robust economy, well developed local heavy industry, and a large number of mechanical and electrical engineers. I think the poorest of the countries I just listed is Romania, with the 39th largest GDP in the world (out of 190-something). By the 1990s, being able to design and produce a tank on ones own was a privilege reserved for a fairly small number of countries. Even countries that could plausibly design their own engine, transmission and tracks frequently farmed these out to Germany's Renk and Diehl, respectively. Alternatively, you might say that Brazil in the 1980s represents the floor economy of a nation capable of designing and producing its own tank, although the entire turret on that vehicle is a British design from Vickers. So that would be the first thing I would say about designing a 1990s tank; it's not for small nations, and even the rich ones frequently used foreign components.
×
×
  • Create New...