5 ms·

>by using jets of air from a pressurized source Presumably bleed air from the jet engine compressor, which means this design won't work for piston-engine prope

>by using jets of air from a pressurized source Presumably bleed air from the jet engine compressor, which means this design won't work for piston-engine propeller drones, which is the usual configuration for small non-stealth drones. I wonder where in the copyediting process this got left out, because otherwise this design would be bonkers. >Eliminating external moving parts is expected to reduce weight External moving parts, of course, since it'll have just as many valves to control the flow of bleed air as a regular hydraulic setup. I wonder what material they're making the wings out of-- bleed air is pretty hot.

christkv 3y ago
What happens when propulsion fails on this. Does not seem likely it will be able to perform a glide landing.
- AdamN 3y ago
  It's unmanned so a self-destruct mechanism is probably the straightforward solution - or disable power and use a parachute
- londons_explore 3y ago
  Backup air reservoir?
- justin66 3y ago
  It's an X plane, and it's unmanned. If propulsion fails, it will presumably crash in the desert. Some of the press on this talks about weight savings. If they're really serious about that, well... none of their flights are intended to go above Mach 0.7. Possibly they could deploy a ballistic parachute like Cirrus airplanes offer.
- sgjohnson 3y ago
  Presumably, this would be operated in hostile territory, so nobody would particularly care about it turning into a giant fireball upon crash landing. Or self-destructed when still airborne.
- deleted 3y ago
  [deleted]
boxed 3y ago
Couldn't it have just one central compressor for this air?
- londons_explore 3y ago
  I suspect it needs rather large qualities of air. Ie. Cubic meters per second. It's gotta be a modified engine that lets you extract compressed air.
  - krisoft 3y ago
    > It's gotta be a modified engine that lets you extract compressed air. That is basically a standard feature on every jet engine. It is called bleed air. https://en.wikipedia.org/wiki/Bleed_air https://en.wikipedia.org/wiki/Bleed_air
- usrusr 3y ago
  Yes? For example that central jet engine that the plane already has? Doesn't change anything about requiring additional moving parts to control where the compressed air goes and where it goes not. The goal of this entire exercise is not to expel some extra compressed air in places where previously regular outside flow happened, the goal is to control the plane by changing when and where that disturbance by extra air happens.
  - Toutouxc 3y ago
    To be fair, the original comment was about piston engine powered aircraft. These would really need either a separate compressor/blower or a complicated modification of the exhaust system.
    - usrusr 3y ago
      True, must have missed that, deep branches on higher rated sibling comments. And at the time when I did skim the actual grandparent, I dismissed the part about piston because I don't believe that any of the suspected benefits of this pressed air disturbance control scheme could ever be meaningful in the realm of piston-engine drones. Control surfaces are cheap.
LargeTomato 3y ago
> Presumably bleed air from the jet engine compressor. We don't know that and this is the very first prototype so it could absolutely evolve over time. > Which means this design won't work for piston engine propeller drones In its current, nascent configuration where we are prototyping a new technology using a testbed platform, maybe. Again, this is not a commercial-ready product it's a prototype. > Which is the usual configuration for small non-stealth drones So this prototype doesn't fit on a $10 quad copter so it's... Flawed? > I wonder where in the copyediting process this got left out Prototype. > Because otherwise this design would be bonkers. More or less bonkers than dismissing a completely novel aviation technology before it's even gotten off the ground? More or less bonkers than dismissing a completely novel technology because it doesn't work for your one specific hypothetical use case?
- rmccue 3y ago
  > So this prototype doesn't fit on a $10 quad copter so it's... Flawed? I didn’t read the original as meaning non-military drones, rather non-stealth military drones. For example, to the OP’s point, the Predator drone is powered by a piston engine - I’m not overly familiar with other military drones, but stands to reason other UAVs use similar tech.
  - lupusreal 3y ago
    They're talking about this prototype doing mach 0.7, so it's a safe bet they intend it to have a turbofan. That's much faster than a MQ-1/MQ-9 and also faster than a (turbofan) MQ-20. Dismissing this design because it requires a jet engine just seems bizarre. Like okay, it doesn't work with piston props... so what?
- adrian_b 3y ago
  > We don't know that and this is the very first prototype so it could absolutely evolve over time. The high-pressure air must come from a compressor, either a separate compressor or the jet engine compressor. Obviously it is much cheaper and much more compact to use bleed air from the jet engine compressor, than to include a second compressor, only for maneuvering. On an aircraft without a turbo-engine adding a compressor would increase the cost and the energy consumption a lot in comparison with the traditional methods of steering the aircraft, so it is not advantageous. However this method without control surfaces should also be usable with turboprop engines, not only with jet engines.
fidotron 3y ago
BAE built a much smaller test UAV of the same idea in 2010 https://en.wikipedia.org/wiki/BAE_Systems_Demon https://en.wikipedia.org/wiki/BAE_Systems_Demon which was indeed a mixture of bleed air and exhaust.
krisoft 3y ago
> bleed air is pretty hot. Initially yes. But then it can be cooled by expanding it or mixing it with cold air. This is pretty routine. After all the air you breath on airlines is coming from bleed air too. > it'll have just as many valves to control the flow of bleed air as a regular hydraulic setup Sure, but that's not the heavy stuff. The fact that bits of the wing has to be independently movable means that it has to be much heavier. If the whole wing would be just one piece you could presumably support it more efficiently.
deleted 3y ago
[deleted]
ranger207 3y ago
There's been a bunch of piston engine planes with hydraulic pumps; I don't think a pneumatic one will be much more difficult
Aloisius 3y ago
> Presumably bleed air from the jet engine compressor It appears to come from an auxiliary power unit. https://youtu.be/G_jhcqGjUww?t=43 https://youtu.be/G_jhcqGjUww?t=43

christkv 3y ago

What happens when propulsion fails on this. Does not seem likely it will be able to perform a glide landing.

AdamN 3y ago
It's unmanned so a self-destruct mechanism is probably the straightforward solution - or disable power and use a parachute
londons_explore 3y ago
Backup air reservoir?
justin66 3y ago
It's an X plane, and it's unmanned. If propulsion fails, it will presumably crash in the desert. Some of the press on this talks about weight savings. If they're really serious about that, well... none of their flights are intended to go above Mach 0.7. Possibly they could deploy a ballistic parachute like Cirrus airplanes offer.
sgjohnson 3y ago
Presumably, this would be operated in hostile territory, so nobody would particularly care about it turning into a giant fireball upon crash landing. Or self-destructed when still airborne.
deleted 3y ago
[deleted]

boxed 3y ago

Couldn't it have just one central compressor for this air?

londons_explore 3y ago
I suspect it needs rather large qualities of air. Ie. Cubic meters per second. It's gotta be a modified engine that lets you extract compressed air.
- krisoft 3y ago
  > It's gotta be a modified engine that lets you extract compressed air. That is basically a standard feature on every jet engine. It is called bleed air. https://en.wikipedia.org/wiki/Bleed_air https://en.wikipedia.org/wiki/Bleed_air
usrusr 3y ago
Yes? For example that central jet engine that the plane already has? Doesn't change anything about requiring additional moving parts to control where the compressed air goes and where it goes not. The goal of this entire exercise is not to expel some extra compressed air in places where previously regular outside flow happened, the goal is to control the plane by changing when and where that disturbance by extra air happens.
- Toutouxc 3y ago
  To be fair, the original comment was about piston engine powered aircraft. These would really need either a separate compressor/blower or a complicated modification of the exhaust system.
  - usrusr 3y ago
    True, must have missed that, deep branches on higher rated sibling comments. And at the time when I did skim the actual grandparent, I dismissed the part about piston because I don't believe that any of the suspected benefits of this pressed air disturbance control scheme could ever be meaningful in the realm of piston-engine drones. Control surfaces are cheap.

LargeTomato 3y ago

> Presumably bleed air from the jet engine compressor. We don't know that and this is the very first prototype so it could absolutely evolve over time. > Which means this design won't work for piston engine propeller drones In its current, nascent configuration where we are prototyping a new technology using a testbed platform, maybe. Again, this is not a commercial-ready product it's a prototype. > Which is the usual configuration for small non-stealth drones So this prototype doesn't fit on a $10 quad copter so it's... Flawed? > I wonder where in the copyediting process this got left out Prototype. > Because otherwise this design would be bonkers. More or less bonkers than dismissing a completely novel aviation technology before it's even gotten off the ground? More or less bonkers than dismissing a completely novel technology because it doesn't work for your one specific hypothetical use case?

rmccue 3y ago
> So this prototype doesn't fit on a $10 quad copter so it's... Flawed? I didn’t read the original as meaning non-military drones, rather non-stealth military drones. For example, to the OP’s point, the Predator drone is powered by a piston engine - I’m not overly familiar with other military drones, but stands to reason other UAVs use similar tech.
- lupusreal 3y ago
  They're talking about this prototype doing mach 0.7, so it's a safe bet they intend it to have a turbofan. That's much faster than a MQ-1/MQ-9 and also faster than a (turbofan) MQ-20. Dismissing this design because it requires a jet engine just seems bizarre. Like okay, it doesn't work with piston props... so what?
adrian_b 3y ago
> We don't know that and this is the very first prototype so it could absolutely evolve over time. The high-pressure air must come from a compressor, either a separate compressor or the jet engine compressor. Obviously it is much cheaper and much more compact to use bleed air from the jet engine compressor, than to include a second compressor, only for maneuvering. On an aircraft without a turbo-engine adding a compressor would increase the cost and the energy consumption a lot in comparison with the traditional methods of steering the aircraft, so it is not advantageous. However this method without control surfaces should also be usable with turboprop engines, not only with jet engines.

fidotron 3y ago

BAE built a much smaller test UAV of the same idea in 2010 https://en.wikipedia.org/wiki/BAE_Systems_Demon https://en.wikipedia.org/wiki/BAE_Systems_Demon which was indeed a mixture of bleed air and exhaust.

krisoft 3y ago

> bleed air is pretty hot. Initially yes. But then it can be cooled by expanding it or mixing it with cold air. This is pretty routine. After all the air you breath on airlines is coming from bleed air too. > it'll have just as many valves to control the flow of bleed air as a regular hydraulic setup Sure, but that's not the heavy stuff. The fact that bits of the wing has to be independently movable means that it has to be much heavier. If the whole wing would be just one piece you could presumably support it more efficiently.

deleted 3y ago

[deleted]

ranger207 3y ago

There's been a bunch of piston engine planes with hydraulic pumps; I don't think a pneumatic one will be much more difficult

Aloisius 3y ago

> Presumably bleed air from the jet engine compressor It appears to come from an auxiliary power unit. https://youtu.be/G_jhcqGjUww?t=43 https://youtu.be/G_jhcqGjUww?t=43