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.
> 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?
I also was puzzled by the focus on piston engines and stealth. Just ask why rather then assume something negative; almost always, I find people have a good reason - one that they will never bring up if I attack them. People react: Attack -> Defend; Ask -> Answer. IME, people have a lot of good stuff to say if I give them space, and can sound like idiots of I attack them.
'Why are you focusing on piston engine propeller drones and not, say, passenger airliners or military fighters or all the other flying machines? Do they say that small, non-stealth drones are their goal?'
If it's truly spam, flag the comment (and downvote it) and move on; there's little of that on HN. I assume you're talking about comments we perceive as low-quality. The obvious solution there is to downvote them, but I think you are talking about responding:
Passing judgment is very tenuous business and how I make most of my worst mistakes - then I'm the fool, who is spamming and worse, poisoning the conversation. Much better to be curious and ask. Usually I learn that what I understood as spam was my limitation - I didn't think of another interpretation, or that the author just needed to spell out a good idea a bit more, and now I've learned something. And sometimes the author didn't think of something and they learn something from me, which they wouldn't do if I attacked them.
It's also respectful, which is essential, and we have two people with positive interactions, which is also critical in this age.
As an example, I personally would say, if I had to judge, that your comments are spamming this discussion, and in multipile ways that explicitly violate HN guidelines. I am giving you the benefit of the doubt, that you are an intelligent person in good faith - which you deserve - and I think we're both rewarded.
Seriously, read the HN guidelines (link at bottom of page). They not only explain the ways of HN, they are a good guide to effective social media technique in general.
> Do you believe there is ever ...
My response is that hyperbolic, extreme hypotheticals lead to arguments and are not useful. Life does not happen at those extremes, nor does the interesting discussion.
It's interesting you feel like poisoning a conversation is wrong or bad. When I see a conversation or thread that is "bad" I feel like immediately poisoning it is a valid solution. A blunt one, no doubt, but in the face of overwhelming waves of "bad" or dangerous conversation it's a fine tool to have.
I would email the HN moderators - smart, responsive people who really know their stuff - and talk about it with them. They encourage people to reach out, including about things like what we're talking about.
hn@ycombinator.com
I'm not sure where they are today - usually they would have arrived long ago for a conversation like this one. You are entitled to your opinion, of course, but that type of activity - poisoning, etc. - isn't welcome on HN.
> 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.
Actually, these active flow control concepts can shape the flow so much that it's possible to create ridiculous L/D, and even create negative drag in certain regimes. So it's possible to be paying for a compressor and have it still come out ahead.
> 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.
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?
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.
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.
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.
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.
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.
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.
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.