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Collimatrix

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Everything posted by Collimatrix

  1. Collimatrix
    This slide explains that opposed piston diesels have a small inherent efficiency advantage due to lower surface area/volume ratio.
  2. Collimatrix
    You can see that the SU-57 with the UCAV flash on the vertical stabilizer also has replaced the upper and lower DIRCM turrets with antenna fairings. The obvious guess is that those antenna fairings are for controlling UCAVs.
  3. Collimatrix
    If there was, I haven't been able to find it. @Monochromelody mentions what sound like one-off T-80 variants with neutral steer capability in this thread. Mysteriously vanished SH user @Levi posted this excellent guide to Soviet MBT transmission design here. Sadly, most of the important material has fallen prey to the dreaded link rot. But I remember the basics well enough. In short, the T-64, T-72 and T-80 have basically the same transmission. The parts aren't compatible between the three (that would just be silly!), but they all work basically the same way. In a typical Western MBT the power flowing from the engine is split into a steering drive and the transmission. The transmission varies the drive ratio, and the steering drive alters the balance between the left and right tracks as needed. The power is then re-combined and sent to the final drives. In the Soviet tanks the power is split into left and right half transmissions. Essentially, each track has its own transmission, and these transmissions also double as steering drives and final drives. It's very simple and compact, and making a Western-style system that could fit in the same footprint would be quite a trick. Not necessarily impossible, but quite a trick.
  4. Collimatrix
    Haven't these people seen Zoolander?
  5. Collimatrix
    I don't think so. A poster here a long time ago mentioned that the Kharkov factory was working on an upgraded transmission for the T-80UD/T-84/Oplot family that would have a continuously variable drive ratio as well as neutral steering, but that this was never actually mass-produced.
  6. Collimatrix
    Don't post anything on this forum that will get it shut down by goons in suits. Don't post anything on this forum that might get your countrymen killed. If you screw up and accidentally post something that is uncomfortably close to any of the two categories I just listed, PM a moderator and they will disappear it like Stalin. Other than that, go nuts. If the super-secret specifications of some exotic armor array get leaked or accidentally photographed elsewhere and flood the 'net? It doesn't make sense to pretend that shit is secret.
  7. Collimatrix
    Perforated armor does not work particularly well against APFSDS in general. Doesn't matter what country the factory is located in. Perforated armor works by having an array of holes (thus the name) that are sized such that it is statistically likely that an incoming KE threat will catch one of the holes on the very edge. This tends to mangle the KE threat and also yaw the penetrator so it hit slightly side-on. APFSDS darts have a very high aspect ratio and a relatively small diameter, so they should be fairly easy to mangle and they should be enormously degraded if they rotate even slightly, right? So far so good. But APFSDS has a number of properties that also make it less vulnerable to perforated armor. The biggest problem is that APFSDS is really, really fast. If you impart a given amount of torque on an incoming projectile with a perforated stand-off plate, it will yaw less by the time it reaches the main plate if it's going faster. A given amount of torque will impart a given angular velocity on a given penetrator, and with APFSDS the penetrators are moving so fast that they don't have much time to yaw before they strike the main plate. On top of that, APFSDS has an extremely high moment of inertia about the yaw axes because it is so long. A given torque applied to the rod will rotate it less. Finally, APFSDS operates within a semi hydrodynamic regime, and the penetrators erode by design. They're not like traditional, full-caliber AP rounds that live and die by penetrator integrity, and this makes it a lot harder to apply torques to them in the first place. So, APFSDS is moving too fast to get turnt in time, it's resistant to getting turnt, and it's not easy to turnt it in the first place. All my sources on the matter (e.g. Hazell 2016) say that armor arrays that try to yaw APFSDS don't work particularly well. That said, a perforated array would work much better if the perforated array has more inertia. So, a perforated array made out of, say, depleted uranium might work against APFSDS where steel would fail. I have suspected in the past that this might be what the "DU mesh" in the Abrams' turret is, but @SH_MM has stated that he thinks a DU-based NERA array is more likely. In any case, the design of the DU arrays in the armor have changed from model to model. The T-14 almost certainly has ERA built in, and there is no reason to expect that future Russian ERA will look like 1980s vintage K1 "postage stamps". The grain size will only go down so much from a single rolling operation. To get ideal grain sizes, the process needs to be rinsed and repeated a few times. That costs.
  8. Collimatrix
    Everything I've read suggests that perforated armor does not work terribly well against APFSDS. I buy the rest of what you say, more or less. There have been substantial improvements to armor steel metallurgy over the past several decades. But they are costly improvements.
  9. Collimatrix
    You could have a conventional cartridge case that has perforations it bursts along.
  10. Collimatrix
    Complete speculation on my part. However, a hi-lo gun does not necessarily need the expansion chamber to be located in each casing, that's just how 40mm does it. It's entirely possible to have an oversize firing chamber.
  11. Collimatrix
    This is surprising. What could the Israelis possibly get from Ukrainian radar technology that they can't already make better on their own?
  12. Collimatrix
    Dennis Loebner
  13. Collimatrix
    I suspect that most cannons that are advertised as "low pressure" are actually high-low systems.
  14. Collimatrix
    The lower the pressure in the breech of the cannon, the less steel you need to keep the cannon from exploding. Low-pressure guns are much lighter, but also lower-performing relative to their size.
  15. Collimatrix
    I bet a game where you raced Kettenkrads would be fun as shit. Those things look like they would be really janky and unstable while turning at speed.
  16. Collimatrix
    I will be curious to see how the US pullout occurs. Does it mean that everyone will leave, or just normal units, with SF still there? Will the USAF/USN stop performing air strikes? If the USAF/USN leaves, the SDF may start having even more problems against ISIS remnants.
  17. Collimatrix
    Yes, that is very interesting. But Pasholok has a lot of access to the Soviet archives, right? I am curious to know how he developed this view.
  18. Collimatrix
    I don't know why everyone is so concerned about the survivability of this vehicle. The Pentagon has tried to kill it like, four times already. What the hell makes anyone think that ATGMs or 125mm gunfire are going to have any more luck?
  19. Collimatrix
    According to Richard M. Ogorkiewicz's absolutely indispensible Everything You Ever Wanted to Know About Tanks* but Were Afraid to Ask, diesel fuel has a mass efficiency of about 3 against shaped charges. That is to say, it is 3 times as effective as steel RHA, pound for pound. But, given the disparity in densities, this means that you need about 3 inches of diesel to match the protection of 1 inch of conventional steel armor. He does say that cellular fuel storage systems can "in practice it can be more than that." I think @SH_MM had some information on these sorts of fuel cell armor arrays. So, a good old-fashioned Malyutka will penetrate about 450mm of RHA. To stop the shaped charge jet just with diesel fuel, you would need a fuel tank that's nearly a meter and a half deep. That's clearly impractical. But supposing instead you had a hull design with 220mm RHA LOS (e.g. a 93mm glacis plate set back at 65 degrees, just like the M60 has) followed by 700mm deep fuel tanks, wrapped around the driver. That could work. If it's the 1970s, and you've just noticed that MBTs are dying in droves to guided missiles, and that fancy composite armor the boffins keep talking about isn't quite ready for mass-production yet, this would be a practical approach to making main battle tanks don't die quite so easily.
  20. Collimatrix
    NATO level 4 and 5 protection specifies a 20mm fragment simulating projectile that is 54 grams moving 960 m/s. That's about half the kinetic energy of WWII vintage Solothurn/Lahti 20mm AT rifles, which could penetrate something like 40mm of RHA. Jamming RF-based proximity fused shells does not incur any additional weight or complexity if the jammer is an AESA radar that is used by the APS. Trophy uses AESA. AESA radars can trivially double as jammers with just a software upgrade.
  21. Collimatrix
    Frustratingly, we won't know for at least weeks, but probably months. A few of the attacks that appeared to be opportunistic were actually coordinated by ISIS.
  22. Collimatrix
    Why would airburst shells sidestep any of the issues I mentioned? Think about it. 1) Average fragment density will still be subject to the inverse square law. 2) Artillery shell fragments have low sectional density and high aerodynamic drag, and thus poor armor penetration. Simply hardening sensor mounts to defend against airbursts isn't out of the question. 3) Airburst shells rely on active sensors (usually proximity fuses) to determine the distance to the ground. These can be jammed. This means an unavoidable trade-off between shells that are exploding far away above the tanks, in which case they have a low density fragmentation pattern with slow-moving fragments, or they're exploding closer to the tanks, which makes them easier to jam or engage with APS.
  23. Collimatrix
    Hard-kill APS could defend a tank from dumb artillery fire fairly easily. Consider: most APS are cued by radar. The radar can determine (within the resolution limits of the radar antenna) the position and velocity of incoming shells. Therefore, the APS need not expend ammunition against any threats that are not on an intercept course with its host vehicle. I think you would agree that a dumb artillery shell that doesn't hit the roof of a tank isn't going to do much. Maybe damage some sensors or rough up the skirts if it's a near miss. If the APS smacks the incoming shell hard enough that the shell detonates at some distance from the tank, then this is still a massive improvement over having the shell hit the tank from above. Shock wave intensity drops off as a function of the inverse square of distance. So, a shell that is detonated by APS ten meters away from a tank's roof will produce a blast overpressure that is one one-hundredth as powerful as one that detonates only a meter away. However, it is also possible, perhaps even likely when engaging insensitive munitions, that the intercepted shell will not detonate at all and will instead deflagrate or it may simply be ripped apart. In the case of fancy shells that use explosively forged penetrators or blast fragmentation rounds, the shell relies on sensitive geometry and timing, so hitting it with APS should keep it from functioning properly.
  24. Collimatrix
    Active shooter event in Strasbourg: https://www.bbc.com/news/world-europe-46530265
  25. Collimatrix
    I saw this news, and I am puzzled. Kinzhal is just short of 8 meters long. The maximum length of weapons that fit into SU-57's weapons bays is just over 4 meters. So this mini-Kinzhal will be about half the size, in linear dimensions, as a normal Kinzhal, which means it will be about 1/8th the weight. Seems like it should have much less performance.
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