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DARPA's air-steered X-65 jet
- martinky24 3y agoThis is sick. Who knows if it will go anywhere, but glad the government still finds ways to spend money on expensive experiments. It pushes collective science forward.
- schiffern 3y agoSo true. RIP "invisible hand" efficient market hypothesis. Don't get me wrong, I agree with you! I'm also happy that we use taxpayer money to subsidize corporate R&D, but let's not suddenly sugarcoat that fact (or forget it entirely) the instant our thoughts shift to economic policy. In the VC world, your one huge success needs to cover the cost of the other nine failed bets. When taxpayer-funded research gets "commercialized," this rule is quietly forgotten. That's the biggest subsidy giveaway right there.
- throw1234651234 3y agoI think the fact that we have tens of companies making different sugar water is proof that capitalism allocates capital in ways that is useful to humanity! Sarcasm aside, I don't actually have a better solution.
- gumby 3y ago> RIP "invisible hand" efficient market hypothesis. Smith didn’t claim that an “invisible” hand was a sole or even predominant mechanism, just that it could apply to specialization. In fact at a microeconomic level Coase’ “Nature of the firm” says the opposite is true, and he’s as mainstream as you can get. In general (this is not a comment about you, schiffern) most people who exalt Adam Smith have never read his book and would be shocked that he was such an enthusiast for welfare, regulation, and government intervention and support.
- schiffern 3y agoIndeed, I'm speaking to the modern mythologized usage of "invisible hand," which scarcely resembles Smith's original conception.
- xnx 3y ago2 days ago. 195 comments: https://news.ycombinator.com/item?id=38922657 https://news.ycombinator.com/item?id=38922657
- laktak 3y agoI also posted this two days ago. Must have been in the repost queue.
- fodkodrasz 3y agorepost queue?
- pansa2 3y agoSecond-Chance Pool: https://news.ycombinator.com/item?id=26998308 https://news.ycombinator.com/item?id=26998308
- fodkodrasz 3y agoTIL. thx.
- oefnak 3y ago[flagged]
- jojobas 3y agoProbably can't escape moving surface stabilizer trim.
- anilakar 3y agoHow so? Is there a sharp gradient in the boundary layer effect that makes it an on/off control system?
- jojobas 3y agoBoeing 747 stabilizer trim is achieved by rotating the entire tailplane by up to 15 degrees. The elevator is much smaller (less than 1/3 the area) and is deflected by a smaller angle. That's some serious force you'd have to apply with those air jets either throughout the cruise phase or takeoff/landing.
- anilakar 3y agoPositioning of nozzles in the video suggests they're experimenting with a BLC system, not just nozzles placed in the extremities like in the Harrier jets.
- tlb 3y agoPassenger jets need it because the center of gravity can vary a lot depending on passenger and cargo loading. A spy plane could probably be built with almost zero variation, with some careful fuel tank management.
- JumpCrisscross 3y agoThere are entire classes of tail-less aircraft. This is an abundantly solved problem.
- jojobas 3y agoHuge control surfaces harsh CoG limitations are the tradeoff.
- 3y ago
- solarkraft 3y agoAnd how does this "active flow control" control air flow without moving parts?
- Cthulhu_ 3y agoValves, which, yeah, are moving parts.
- askvictor 3y agoTesla valve?
- lupusreal 3y agoHow do you turn one on or off?
- sandworm101 3y agoTesla isnt really a valve, more a fluidic diode. And there are better fluidic diode designs out there.
- QuadmasterXLII 3y agoTesla valve is definitely a frisco haha
- me_me_me 3y agoI think original was more specific, no moving control surfaces
- sandworm101 3y agoThere are valves without wearing or rubbing parts. A solenoid that moves a ball back and forth can open or close billions of times without any appreciable wear.
- cbeach 3y agoMoving control surfaces are simpler, from an engineering perspective. I'd worry the failure modes of a pressurised air system, which are surely more numerous than a simple mechanical flap. Any failure would be catastrophic to the airplane.
- Cthulhu_ 3y agoYou're making very conclusive / "just so" statements; are you an engineer? Because the moving control surfaces have their own issues; actuators, hydraulics, wear and tear, etc. This looks (and I'm no engineer) to be mechanically simpler, lighter, fewer moving parts, etc. Of course, there's bound to be a caveat or ten, since else why wasn't it tried earlier? It doesn't look technologically advanced, doesn't look like it couldn't have been done decades ago.
- WJW 3y ago1. Air planes are full of pressurized air, hydraulic and fuel systems already, and they fail very rarely indeed. 2. Aircraft control surfaces are quite a bit more involved than being "a simple mechanical flap".
- zython 3y agoIts unmanned; even if it should crash its not catastophic IMO
- 0x457 3y ago
- akdor1154 3y agoSteering while at slower speeds might be tricky, right? Hope they lined up with the runway from far enough away!
- mannykannot 3y agoConventional moving control surfaces also have reduced effectiveness at slow speed. The thing is, though, that an airplane will not be flying unless it is traveling at a speed sufficient for it to create lift at least equal to its weight, and the forces needed to control the aircraft are a fraction of that (you can get an impression of the size of that fraction by comparing the area of the control surfaces to the area of the wing.) I doubt DARPA would commission this aircraft without having already established that it is likely to work, and it will have conventional control surfaces as a backup. I am curious as to whether they intend to keep conventional moving surfaces for trimming in pitch, especially if they are going to give it flaps.
- HPsquared 3y agoIt could be better than conventional controls at low speed, dependign on how strong the pressurized air jets are. A bit like reaction control thrusters on a spacecraft? I wouldn't be surprised if there are even control forces at zero airspeed, with just the air jets acting like reaction control thrusters. Or it might be more like active boundary layer control, just nudging the passing air stream one way or the other with the air jets.
- usrusr 3y agoOne outcome of the experiment is already certain: the demonstrator will live on forever in "ugliest plane" collections. And as usual with the constituents of these lists, it's not entirely without appeal. You almost want to pet them for providing consolation.
- qingcharles 3y agoOne man's ugly is another man's beautiful. I thought it looks fantastic.
- bilsbie 3y agoIs there a way to take off with only active flow control? ( I’m future craft) Otherwise it doesn’t seem like much of a win if you always need both systems.
- krisoft 3y ago> Is there a way to take off with only active flow control? I think so? Of course you still need steering control on the gears, but I don't think you mean that. Maybe you are thinking similar to how I was thinking about airplanes before I started learning to fly. I was thinking that taking off is surely some deviously hard trick, since you go from non-flying to flying. But in reality airplanes are designed to "want to" fly. You just apply throttle and it kinda happens almost on its own. In fact you need to push the nose down a bit so it doesn't fly up before you picked up enough speed to do safely. (I understand that this description might not be true for every airplane, but the general idea that take off is not that hard is usually true for all of them.) In short I don't see why it couldn't work.
- yohannparis 3y agoYes, this is explained in the video and article. The prototype will have both control for comparison study and baseline data. i.e. only manipulating yaw with air.
- 2OEH8eoCRo0 3y agoFewer surfaces that could reflect radar. Nice.
- tiffanyh 3y agoI'm surprised it still looks so much like a "normal" plane. When you remove the need for a person to sit in the aircraft, you'd think it would create the opportunity to generate entirely new design profiles. But this still looks like most planes.
- washedup 3y agoA big part of the idea is the have a plane the models what humans will eventually use, so that any test results they get can more easily translate to eventual human-carrying flights. It's not a mistake that the speed, weight, and shape closely match what fighter pilots train in.
- JumpCrisscross 3y ago> what humans will eventually use There is emerging consensus that the F-35 is the last manned fighter America will produce.
- nine_k 3y agoActuators without moving parts would be great to have on civilian airliners, too! Fewer moving parts means fewer chances of something to break, fewer parts to service when landed, less weight to carry, likely cheaper to produce. Wins all around.
- icegreentea2 3y agoPerhaps. But if you look at most UCAVs, they mostly have 'broadly normalish' looking shapes. XQ-58 for example is relatively conventional looking. I think the reality is that there are a lot of advantages of the 'normal' airplane shape that removing the pilot doesn't drastically change. Warplanes are going to have some pretty high mass, kinda bulky thing to manage (especially engines and radar). Keep those close to the center of mass is just... sensible. Since your flying forwards, that biases you towards either a tube with wings or flying wing. Pure flying wings are apparently kinda annoying to deal with - especially when what you're working on is trying to innovate in autonomous systems, maybe you don't want to spend extra effort trying to conquer too unconventional structural layouts.
- sudosysgen 3y agoChina also tried this a few years ago (2013, according to Wikipedia), with their GJ-11 drone : https://en.wikipedia.org/wiki/Hongdu_GJ-11 https://en.wikipedia.org/wiki/Hongdu_GJ-11, https://www.scmp.com/news/china/science/article/3209263/superior-stealth-chinese-drone-wing-design-aims-raise-bar-radar-evading-aircraft#Echobox=1675860085 https://www.scmp.com/news/china/science/article/3209263/supe... Supposedly, this could already be in production.
- WinstonSmith84 3y agoThat drone has very clear moving parts https://en.wikipedia.org/wiki/Hongdu_GJ-11#/media/File:GJ-11_at_Airshow_China_Zhuhai_2021.jpg https://en.wikipedia.org/wiki/Hongdu_GJ-11#/media/File:GJ-11...
- sudosysgen 3y agoThat's the bomb bay, not the control surfaces?