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There is a Czech engine called the PBS TJ-100 that I’ve seen used on some jet powered gliders. It’s about 290 lbs of thrust and retails for $75k. There is als

There is a Czech engine called the PBS TJ-100 that I’ve seen used on some jet powered gliders. It’s about 290 lbs of thrust and retails for $75k. There is also an uprated version, the PBS TJ-150 that’s about 340 lbs. I think that would be enough for an antiship missile with a smaller warhead like they’re building.

jojobas 2y ago
Is there any reason not to use much cheaper piston engines? If you're going for saturation of and defenses you don't need speed that much, you only need the ability to hit the target if not shot down.
- zakary 2y ago
  I imagine speed and simplicity. There’s a lot more things that need maintenance on a piston engine
  - jcgrillo 2y ago
    Simplest could be a pulse jet like the V1 used, and capable of higher speeds than a piston engine fan or propeller driven aircraft.
  - jojobas 2y ago
    Maintenance? It works for <10 hours and explodes.
- cameldrv 2y ago
  That's the basic philosophy of what people are now calling "fixed wing suicide drones." It's just a cruise missile with a propeller and a piston engine instead of a jet. Here are the tradeoffs as I see them: 1. The piston/propeller missile is slower, so it's easier to shoot down. If you have a certain detection range, you have more time between detection and impact. The traditional AEGIS type air defense on a high end ship has three layers -- long range missiles, short range missiles, and guns. Guns are the cheapest with the most ammo, but they're short range, so with a fast missile you only have a matter of seconds to shoot it down. If there are a lot coming at you simultaneously, you need more guns to get them all. If they're moving slower, this is a lot easier. 2. Lift is proportional to the square of the airspeed, so the slower you go, the bigger the wing you need. Compare for example the LRASM (the latest U.S. anti-ship missile), to a Cessna 172. They each weigh about the same (2500 lbs), and have very roughly comparable payload and range. Since the Cessna goes about 120 knots and the LRASM goes roughly 600 knots, that's a 5x difference in speed, so the Cessna needs roughly 25x bigger wings to stay in the air. You see this with the span, the LRASM has a span of 8 feet and the Cessna is 39 feet. Obviously the chord on the Cessna is a lot bigger too. The bigger wing will give you a bigger radar cross section, so you're detected sooner. It also makes the missile cost more due to all of the structure, and it makes it hard to put it in a launch tube if the wings are supposed to fold up. I'm sure there are a lot of creative solutions to this with flexible wings, etc, but there are good reasons to prefer a faster missile. Whether that ends up being the war winning solution though, time will tell. Things are a lot different than 20-30 years ago in terms of tradeoffs though. Back then your guidance system with a radar, computer, radio/satellite transceiver, and inertial navigation would weigh over 100 lbs, and cost over $100k in today's dollars, so making smaller missiles made less sense. Now, you can do guidance with GPS, strapdown inertial, and optical, and there are low power and low cost radio transcievers. Instead of a radar, you can do the terminal guidance optically with a multi-teraflop GPU that costs $50.
  - jcgrillo 2y ago
    > guidance with GPS This sounds like a major liability, GPS is an extremely brittle and vulnerable system--you'd only need one or a small handful of nuclear warheads detonated in space to knock it out completely. https://www.scientificamerican.com/article/what-happens-if-a-nuclear-weapon-goes-off-in-space/ https://www.scientificamerican.com/article/what-happens-if-a... OTOH it would be so much easier now to develop a celestial navigation system that works optically than it was back in the 1950s.
    - bartonfink 2y ago
      lmao at equating "extremely brittle and vulnerable" with "susceptible to multiple nuclear missiles shot to geostationary orbit". thanks for the chuckle.
      - jcgrillo 2y ago
        If you (a superpower) deploy a bunch of GPS dependent equipment, and I (another nuclear power) am fighting you--and I'm less dependent on GPS--why would I not destroy GPS immediately, given that it's not very hard? EDIT: Destroying GPS completely with nukes lobbed into space isn't the only way to mess it up either, it's susceptible to more terrestrial electronic countermeasures as well. It's generally not a good idea to depend on GPS alone, you need other backups as well. Pilots know this It's why they fly with a paper chart and a compass as well as GPS. EDIT: Also, if my opening move is nuking space, I don't just deny you GPS, I also deny you all your other space-based advantages. I'd guess that would be one of the very first things any nuclear adversary of the US would do, because the damage is so asymmetric.
  - Log_out_ 2y ago
    Last miles booster rocket or no enginr after climb?
  - impossiblefork 2y ago
    But the piston engine design really have to be slower? For example, some WWII fighter aircraft could be quite fast, easily comparable to the claimed top speed of Tomahawk missile that can be found on Wikipedia and since you'd have less drag I don't think you'd need a huge piston engine. I'm guessing you'd want something like 500 kW out of 200 kg of engine, but that's similar to the claimed performance of the apparently not-quite production ready Zoche Aero-Diesel.
- entropyneur 2y ago
  Ukrainians use Maxim guns to shoot down ICE-propelled Shaheds. Pretty hard to saturate that. You generally want to saturate the more advanced systems.
  - jojobas 2y ago
    Shaheds can fly at 4000m, good luck with your Maxim. They also try to catch them far from target areas by spreading roving AA squads all over the border, somewhat impossible at sea. Something similar could also dive from 4000m gaining quite some speed.
- siliconc0w 2y ago
  Armchair aeronautical engineer but other solutions might be pulsejets or ramjets which can be much less complicated and cheaper than a turbofan.
  - LorenPechtel 2y ago
    Ramjet has a high minimum flight speed. (Although this is an issue across most missiles--ground launch versions of missiles are the air launch version with an extra rocket on back that boosts it to a suitable flight speed.)
    - siliconc0w 2y ago
      Maybe electric launcher+ ramjet? Really the cheapest and most reliable thing would be an electric launcher that threw JDAM-like gliding bombs. Probably could get pretty good range with a strong enough launch system.

jojobas 2y ago

Is there any reason not to use much cheaper piston engines? If you're going for saturation of and defenses you don't need speed that much, you only need the ability to hit the target if not shot down.

zakary 2y ago
I imagine speed and simplicity. There’s a lot more things that need maintenance on a piston engine
- jcgrillo 2y ago
  Simplest could be a pulse jet like the V1 used, and capable of higher speeds than a piston engine fan or propeller driven aircraft.
- jojobas 2y ago
  Maintenance? It works for <10 hours and explodes.
cameldrv 2y ago
That's the basic philosophy of what people are now calling "fixed wing suicide drones." It's just a cruise missile with a propeller and a piston engine instead of a jet. Here are the tradeoffs as I see them: 1. The piston/propeller missile is slower, so it's easier to shoot down. If you have a certain detection range, you have more time between detection and impact. The traditional AEGIS type air defense on a high end ship has three layers -- long range missiles, short range missiles, and guns. Guns are the cheapest with the most ammo, but they're short range, so with a fast missile you only have a matter of seconds to shoot it down. If there are a lot coming at you simultaneously, you need more guns to get them all. If they're moving slower, this is a lot easier. 2. Lift is proportional to the square of the airspeed, so the slower you go, the bigger the wing you need. Compare for example the LRASM (the latest U.S. anti-ship missile), to a Cessna 172. They each weigh about the same (2500 lbs), and have very roughly comparable payload and range. Since the Cessna goes about 120 knots and the LRASM goes roughly 600 knots, that's a 5x difference in speed, so the Cessna needs roughly 25x bigger wings to stay in the air. You see this with the span, the LRASM has a span of 8 feet and the Cessna is 39 feet. Obviously the chord on the Cessna is a lot bigger too. The bigger wing will give you a bigger radar cross section, so you're detected sooner. It also makes the missile cost more due to all of the structure, and it makes it hard to put it in a launch tube if the wings are supposed to fold up. I'm sure there are a lot of creative solutions to this with flexible wings, etc, but there are good reasons to prefer a faster missile. Whether that ends up being the war winning solution though, time will tell. Things are a lot different than 20-30 years ago in terms of tradeoffs though. Back then your guidance system with a radar, computer, radio/satellite transceiver, and inertial navigation would weigh over 100 lbs, and cost over $100k in today's dollars, so making smaller missiles made less sense. Now, you can do guidance with GPS, strapdown inertial, and optical, and there are low power and low cost radio transcievers. Instead of a radar, you can do the terminal guidance optically with a multi-teraflop GPU that costs $50.
- jcgrillo 2y ago
  > guidance with GPS This sounds like a major liability, GPS is an extremely brittle and vulnerable system--you'd only need one or a small handful of nuclear warheads detonated in space to knock it out completely. https://www.scientificamerican.com/article/what-happens-if-a-nuclear-weapon-goes-off-in-space/ https://www.scientificamerican.com/article/what-happens-if-a... OTOH it would be so much easier now to develop a celestial navigation system that works optically than it was back in the 1950s.
  - bartonfink 2y ago
    lmao at equating "extremely brittle and vulnerable" with "susceptible to multiple nuclear missiles shot to geostationary orbit". thanks for the chuckle.
    - jcgrillo 2y ago
      If you (a superpower) deploy a bunch of GPS dependent equipment, and I (another nuclear power) am fighting you--and I'm less dependent on GPS--why would I not destroy GPS immediately, given that it's not very hard? EDIT: Destroying GPS completely with nukes lobbed into space isn't the only way to mess it up either, it's susceptible to more terrestrial electronic countermeasures as well. It's generally not a good idea to depend on GPS alone, you need other backups as well. Pilots know this It's why they fly with a paper chart and a compass as well as GPS. EDIT: Also, if my opening move is nuking space, I don't just deny you GPS, I also deny you all your other space-based advantages. I'd guess that would be one of the very first things any nuclear adversary of the US would do, because the damage is so asymmetric.
- Log_out_ 2y ago
  Last miles booster rocket or no enginr after climb?
- impossiblefork 2y ago
  But the piston engine design really have to be slower? For example, some WWII fighter aircraft could be quite fast, easily comparable to the claimed top speed of Tomahawk missile that can be found on Wikipedia and since you'd have less drag I don't think you'd need a huge piston engine. I'm guessing you'd want something like 500 kW out of 200 kg of engine, but that's similar to the claimed performance of the apparently not-quite production ready Zoche Aero-Diesel.
entropyneur 2y ago
Ukrainians use Maxim guns to shoot down ICE-propelled Shaheds. Pretty hard to saturate that. You generally want to saturate the more advanced systems.
- jojobas 2y ago
  Shaheds can fly at 4000m, good luck with your Maxim. They also try to catch them far from target areas by spreading roving AA squads all over the border, somewhat impossible at sea. Something similar could also dive from 4000m gaining quite some speed.
siliconc0w 2y ago
Armchair aeronautical engineer but other solutions might be pulsejets or ramjets which can be much less complicated and cheaper than a turbofan.
- LorenPechtel 2y ago
  Ramjet has a high minimum flight speed. (Although this is an issue across most missiles--ground launch versions of missiles are the air launch version with an extra rocket on back that boosts it to a suitable flight speed.)
  - siliconc0w 2y ago
    Maybe electric launcher+ ramjet? Really the cheapest and most reliable thing would be an electric launcher that threw JDAM-like gliding bombs. Probably could get pretty good range with a strong enough launch system.