Active flow control (AFC) can be pneumatic or electric
Given a small Helion-type fusion reactor, crazy aircraft will be possible
from [1]:
> Electric AFC techniques use arrays of electrodes to discharge aerodynamic or electrical pulses to locally alter airflow. Effectors called synthetic jets – millimeter-wide openings in the aircraft surface that open into centimeter-wide cavities with diaphragms – rely on rapid voltage pulses to make diaphragms oscillate inward or outward, creating airflow sucking or blowing effects, much like a human lung.
> Electrically powered plasma actuators discharge pulses of electricity into the air through electrodes. The heat from the electricity turns the air into plasma, thermally altering flow vectors. All of these techniques have been researched through decades of AFC experiments in laboratories, wind tunnels and small-scale aircraft.
Given the not terribly successful attempts to use fission reactors in aircraft I did wonder about this. Apparently Helion's approach is "mostly aneutronic fusion" - still means that 5% of power output as fast neutrons - which I suspect is probably too much to shield from in an aircraft (mind you I am not a nuclear or aircraft engineer so what do I know!).
Thinking about the fictional Helios in the excellent For All Mankind does make me wonder if it might work in a spacecraft!
But with lots of power output, you can put up heavier craft, even much heavier craft. It's hard to know where all the curves would work out because we have no idea how large, or perhaps rather how small, a mature fusion reactor can be, which means it's more in the realm of science fiction right now than anything we can put real engineering to.
Some interesting actual work on fission-powered planes was done: https://en.wikipedia.org/wiki/Nuclear-powered_aircraft but as the article says the niche they would theoretically occupy ended up going away, especially since a crashing fusion-powered plane is a pretty significant inconvenience but a crashing fission-powered plane is a catastrophe. We're not used to thinking of air flight as something with huge amounts of power available to it for very long periods of time, so our intuitions don't match what is possible. Still, I would think these would be very expensive, if for no other reason than that there is no reason to build them unless you meant to make them very, very large. It's the sort of power plant that could make something like the helicarriers in the Avengers movies possible (albeit I suspect with rather more surface dedicated to control and pushing through air) and it would probably have to be a plane, not a helicopter-based system), but even if we had the blueprints in hand we'd be looking at investments sized more like Navy ships than airplanes.
The term Active Flow Control encompasses a surprisingly wide array of techniques [1]. Most of them are far more subtle that a Harrier like vectoring of exhaust gas.
Personally I'm a fan of "Electrically powered plasma actuators" which can use a high voltage AC source to alter how well the airflow sticks to the wing, and actively reduce drag. Here's some info I read about 2 decades ago on that approach[2] There were open source experiments with high voltage AC and lamp cord wire ("zip cord") in the year 2000.[3]
The more time goes on, the more stuff I see as "leading edge" that I read about 20 years ago. ;-)
> Most of them are far more subtle that a Harrier like vectoring of exhaust gas.
The Harrier has a number of bleed air reaction nozzles dotted around the aircraft so it can be controlled whilst hovering. The vectored thrust is just for the main "drive", these nozzles replace the control surfaces at hover speeds.
> For me the significant area was the flight "puffer" small reaction nozzles that are the most important and the most ingenious aspect of the Harrier. It is actually quite easy to support any aircraft on a downward thrust of gases, and even here with the clever engine mounted vector nozzles... the real trick was in actually controlling the aircraft in the air. The Harrier has a unique system of engine bleed that directs air to the various reaction nozzles...
Many DARPA projects over the years have approached similar X-65 design goals of increased flight control, modularity/redundancy. One of my favorites was Pulse Ejector Thrust Augmentation (PETA). Wired's sensational take on it is at https://www.wired.com/2011/07/boeings-millennium-falcon-floa...
One of the big benefits of X-65/PETA/et al is generating increased lift at takeoff and landing without the wings. One can think of it as a hybrid or multi-lift design. The wings for flight are smaller since it is augmented with other controlled lift/thrust, and this allows the aircraft to be lighter and smaller since it doesn't need huge wings for the low-speed takeoff and landing.
> huge wings for the low-speed takeoff and landing
For military aircraft, at least, large wings aren't just for low speed takeoff and landing, they're also for greater agility and maneuverability. I'm assuming that one of the goals of this X project will be to see whether those performance characteristics can be maintained or improved.
It's not mentioned in the article, but I wonder if part of this is about stealth. I imagine the moving control planes might create additional cross section vs not having them?
I am not an expert by any means, but my understanding is that stealth generally does not work by rending surfaces transparent, but by absorbing the energy or reflecting it in a very, very focused way (away from the origin).
If you send a radar beam and nothing comes back, for the radar operator that means "no plane".
With this scheme it seems you could concentrate all the twisty complicated stuff to a small area in the body of the plane and use rubber hoses to deliver the air to the control surfaces.
Internal space of wings is often used for storing fuel.
I'm not sure if there are any studies on how well modern radar could detect sloshy blobs of kerosene flying through the sky. (Inside totally radar-transparent containers.)
"We have tried to conceive a demonstrator that can accommodate all types of active flow control in a diverse range of aircraft planforms and uses for AFC, whether for high-lift, flight control or other objectives,” says Aurora’s government programs lead, Graham Drozeski.
I'm not quite sure it's the same thing, but I many years ago had an idea for inflatable control surfaces for low-speed vehicles place of mechanical ailerons. I was in between jobs at the time and thought it might be an interesting diversion, especialyl as I've always been a bit of a plane geek. I'm sure it might've been, but after buying a few books on patenting and general design development I quickly realised I was going to be in way over my head and that my savings - grand as I thought they were at the time - would barely make a dent in development costs. Ho hum.
I more meant "not jet-powered" for 'low-speed', and this was a good twenty years ago. It's quite crazy how much RC-tech has advanced in that short span, so maybe you've got a point!
I don't see the word "plasma" once in the article. That said, neither de-icing nor small surface conduits are new in aviation. The J58 famously bled air overboard to disrupt a boundary layer [1].
Darpa is testing a completely novel type of flight control and all these HN comments are just nitpicking irrelevant things, missing the forest through the trees, and saying "it won't work on propeller drones".
The quality of discussion on this website is abysmal.
HN is really good at programming language, IT, and computer science discussions. It really varies once you get outside that bubble.
Sometimes you get a topic on mathematics and a few mathematicians are on there answering questions directly and it's great. In my own field of energy markets and power grid operation, I've noticed the comments have a good mixture of informed folks and those that are way off base. I'm sure it's much worse on some topics and that I'm just as guilty at times :)
Hopefully there are enough experts in an area to drown out the noise.
I'm not aware of any better place for people to chat about programming languages including esoteric stuff like APL where someone actively developing the main commercial offering and another writing an open source alternative are actively contributing to the conversation and explaining how low level operations work.
I've seen plenty of experts here on stuff like Prolog, Lisp, Forth, Smalltalk (Alan Kay has posted on here), tons on Java, Python, R, C++, Julia...it goes on and on.
> There are a surprising amount of that on various discord servers.
I'm never surprised anymore by how much productive discussion is entombed in Discord servers, just sad. Servers are hidden from the public, not web-searchable, barely searchable internally, horrible threading, notification hell, proprietary software, zero data ownership - it could hardly be a worse public discussion forum if it tried. Which makes sense because it was designed to be something else. Sigh... got a link to any of these servers that have better discussion than HN?
The quality of actual technical discussion on HN is not much better on average than any programming or technical subreddit in my experience, if they are well moderated. It shouldn't be surprising that the most technically adept people here also tend to post the least often.
The biggest difference is HN is strongly anti-humor, primarily because of the weird pathology the culture here has about Reddit and appearing "mainstream." But the lack of memes here doesn't make the rest of the content better, rather it tends to result in aggression, knee-jerk contrarianism and overconfident assertions in ignorance becoming low effort virtue signals instead.
HN is just barebones. I don’t think there’s anything about it that specifically makes it better than anything else other than tech articles float to the top.
Because it is filled with all kinds. Junior devs arguing over some pedantic point, and senior devs trying to explain the forest and the trees. Birds are objects, bees are functions.
For a thousand niche subjects in CompSi, there are 0-100 levels of knowledge.
The discourse can be great, and can also go off the rails.
And people post short comments that take strong positions in such a way that it's really hard to decide whether it's a complete beginner bluffing or an expert talking from a wealth of experience.
> HN is not actually good at self deprecating jokes, either
One problem is Hacker News are terrible at recognizing dry humor. 90% of readers interpret tongue-in-cheek posts as face-value. And among those who recognize the humor, 77% want an accompanying "/s" flag iff (day-of-week mod 13 == -2).
I get pushback when I say "If something is too ridiculous, assume it is a joke." Because people are insistent that there are people who really believe dumb shit. They're not wrong, but if they are sincere, why treat them as anything but a joke? It's not like you're going to convincingly correct them when they make such grave errors. So why not a joke? What's the old saying? I'd rather laugh than cry.
Engineer's Disease: the idea that domain competence translates to anything out of that domain.
Put another way, the most hardline, fundamentalist Mormon I've ever known was a former boss, who was a fantastic engineer -- and completely incapable of challenging his assumptions in any other area. Ruthlessly logical when it came to system design, but couldn't apply that to anything else.
Point is, you have a lot of adaquate STEM types talking out their ass about stuff outside their domain.
Plus a non-trivial amount of marketing and agit-prop bots, which shouldn't come as a surprise to the crowd that was talking about GPT long before it was cool.
Just to be clear, fundamentalist Mormon means he had multiple wives, and most likely lived on a secluded compound or in one of the surrounding areas of one of these compounds. Your likelihood of interacting with such a person is near zero.
I think there's a corollary to Gell-Mann amnesia where experts subconsciously believe their expertise in one field transfers to other fields. I've certainly caught myself making this mistake, at least.
I remember it being both comforting and disappointing to read Plato and find Socrates noting this same phenomenon. We've made many advancements as a species, but in some areas we're largely unchanged from ancient times.
Nitpicking a bit, but Gell-Mann amnesia isn't that. Its about generally trusting newspapers/journalists and then reading an article about a theme you're familiar with. Then you realize that the journalist is full of it and got things completely wrong. By turning the newspapers page you start reading an article about something you're not familiar with. You immediately forget the BS from the page before and continue reading (probably same sort of BS) from another journalist but this time you're again trusting the newspapers as some kind of good source of truth.
I've butchered the explanation, but its described much better here:
PS I've seen this effect many times in my life first hand and its frankly astonishing how much power some journalists wield and some don't even know it.
This is my experience with HN: First come the stupid remarks, plain wrong, people that only read the title. Then come the remarks like this one: Complaining about the abysmal quality of the remarks... Then we wait a bit longer and the sewage of remarks is voted down and this remark above remain for a bit longer... Then this remark also disappears and we are left with some insightful stuff at the top. Just wait for some time.
Maybe it doesn't always happen, but generally by the time I read a remark like yours, the really poor ones are at the bottom and nice ones are lining up just below it.
Tech people tend to be "what about" types. You will always find armchair experts in this crowd making an argument why something isn't good enough or unacceptable. I guess it's intellectually stimulating to them. It's a big part of why things like software engineering have become a self-licking ice cream cone; actual problems are set aside to squabble over minutiae and reinvent things all the time because everything is wrong regardless of costs vs benefit.
There's a phenomenon where a lot of tech types begin treating discussions and conversations as adversarial pursuits instead of collaborative exchanges. I definitely recognize that behavior in young me.
It has a side benefit of being a subtle intelligence signal if you're the "what about" person, i.e. "I saw the gap/flaw that OP missed, therefore smarter".
This, I think, is an "I'm smart" feedback loop that promotes more of the same behavior. It's a powerful motivator when you're on sites and boards also populated by ostensibly smart people. No one wants to be the dumb one. So you start to get wrapped up in being the bug finder/doubt-conjurer/"what about"-er.
Enough time goes by with those types being uncorrected and you wind up with comment sections that just turn into TTFC (time to first complaint) races, often by people with no practical experience in a domain save a quick wikipedia search or who don't even read tfa but boy howdy they've sure got some thoughts about that field as a "science" and gosh i can't wait to read them.
Of course this is all just an old man grumbling out a theory on a Tuesday. I'm not sure how to fully solve it and doubt there's a general solution. For myself, I was eventually broken of shitty habits like that through what would probably now be considered bullying. Gotta say though; sometimes it works. Sometimes your brain needs its ass kicked into realizing you're a smart cookie but you're not the smartest, and that's okay.
I think the phenomenon you're describing is just a big part of the engineering skill set.
In my field, Civil Engineering, I get paid mostly to figure out all those things that could go wrong and mitigate or account for them within the budget and constraints available.
Experience is valued in engineering because you can see the probable future on things are likely to break/fail/go wrong, BEFORE they actually do.
It's not surprising to me then that a bunch of engineers who spend all day thinking in this way do the same in different contexts where it may be less appropriate because they are less knowledgeable.
I don't think it's necessarily a way to try to look smart or something.
> It's not surprising to me then that a bunch of engineers who spend all day thinking in this way do the same in different contexts where it may be less appropriate because they are less knowledgeable
Bingo! On HN, the "I am very smart" often becomes "I can reason about any unfamiliar ${complex field} from first principles in the time it takes to write a 2-paragraph comment based on only TFA". Such comments elicit confirmation bias from other non-experts and you may have a completely wrong (or not even wrong) comment at the top. It's a frustrating failure-mode of HN.
"... making an argument why something isn't good enough or unacceptable."
In my experience, it is because most things are not good enough or are unacceptable. You see this in software engineering, technology, and science. Not in this particular case necessarily, but most "innovations" can be shown to be impractical and not good enough through back of the envelope calculations. Yet, the discourse on the Internet is full of these useless things, including this stupidity I remember back at the height of Covid: https://news.sky.com/story/coronavirus-lg-unveils-battery-po...
You need a very diverse community to address these subjects. HN is IT-centered, there’s overlap with a lot of fields and occasionally you’ll get a (few) people who are at home with the subject at hand to explain the subtle intricacies.
But this also relies on the size of the HN populations. Too many and the noise takes over, making it difficult or even frustrating to participate.
Thew few topics that I'm "at home with" come up on HN rarely, but when they do 90%+ comments are just so out of touch with the industry it makes me question anything that isn't deep in SV/YC territory.
There's also an adverse selection bias where the people that talk the most are more likely to be less-informed since they are talking instead of doing.
What's tough is that there's no way to tell who exactly they are. I could be a member of this group for all we know!
It’s not even a matter of sticking to what you know.
Recognising non-goals is a core skill for any technical profession. This is a research project doing completely novel things, and specifically mentions some of the intended use-cases. Of course they’re not the least bit concerned with propeller drones.
A diverse community would help but it would also help if people would recognize when they don't know what they're talking about. I don't make strong statements about ML because I don't know ML. That's just maturity.
Thank you for sharing that. Not only is it an interesting aircraft, but the page answered my main question about this type of control system design, which was "is it using the Coandă effect?"
Years ago, when I read about the original grandiose plans for the Air Force's Y-2, one of the aspects I thought was very interesting was the ability to create a "virtual airfoil"[1] via the Coandă effect. It seemed like one of those designs that was impractical with a human 100% in control, but that might come around again with computer assistance or a fully computer-piloted aircraft. Pretty neat that someone already made it happen.
The one that specifically weirds me out is critiques about how prototypes and things in development aren't products. I mean this is __hacker__ news. Aren't a lot of us aware how shitty projects begin and how long it takes to turn something from an idea into a product? Or are we all disillusioned with get right hacking over the weekend? Like once a week we see something from a uni research lab and the top 5 comments are about how it doesn't beat current industry versions. Fwiw, all my reviewers in conferences are turning into Reviewer 2. I wonder if these are related. It just seems like people don't want context and want to complain instead of critique.
I think acute pedantism often is a sign of being in the autism spectrum.
either that, or it's because the internet encourages people to be passive aggressive but polite, which is a new way to fight online.
it's a problem of being in front of a screen for too long, a lot of people always want to be right, and they treat scientific accuracy like it's a religion.
nitpicking is the second worse thing after online trolling
In the days before contact lenses people who wore glasses were in the minority. Sometimes they were ridiculed. Today it seems rare to find somebody who doesn't benefit from corrective lenses. I don't think human optic abilities have deteriorated so much as human culture has shifted. But we still think people with 20/20 vision have ideal vision. We don't consider them to have a condition with a label like "myopia".
If 90% of people exhibit some characteristics of the autism spectrum, shouldn't we start to consider the people with none as the ones worthy of a label? Like people with true pitch. We give them a label, not people with less than perfect pitch.
Perhaps pedantry is like true pitch or "perfect" vision. It's actually a good thing. Even if it annoys people who don't have it. I wonder if people with true pitch go through life cringing on the inside every time they hear a wrong note. But they learn to never let on that they notice.
Perhaps the part of pedantry that puts a person on the autism spectrum is not so much the noticing as it is the voicing--the seeming inability to control the expression and calling out a correction instead of just letting it slide.
>I don't think human optic abilities have deteriorated so much as human culture has shifted.
You are simply wrong. This is a well demonstrated reality: We have more myopia than we used to. It probably (as in, initial studies are showing) that it has to do with getting enough sunlight.
Well if OP's original "missing the forest for the trees" analogy is to be revisited (which I tend to agree with), it's that pedantry is sort of by (some) definition focusing on the letter rather than the spirit of what's at hand, and due to its often lack of necessity, comes across as taking the opportunity to "one up" or criticize something that doesn't end up making any pragmatic differences.
I've heard some people describe the compulsion something along the lines of "I don't think of it that way, I just noticed something they said was incorrect and so I presented them the correct information", often assuming it would be appreciated.
I mean, it's probably good for engineers in the engineering room, but the culture outside of maker's spaces probably won't consider it smashing conversation.
Yeah, often enough it feels like there a lack of imagination, as well as a lack of appreciation for the history of progress (i.e., it's not linear, it's littered with it-can't be dones that get done, etc.) Most everything here is literal, to a fault. Also there's quite a bit of band wagon jumping. That is, there'll be an initial nearly pointless comment and the conversation takes off from there (nearly void of addressing the original article).
Finally, mention any of this and you get a lesson from HN down vote gang bangers. Sometime I feel like the only free-thinking adult in the room.
There is very little to discuss in finance / economics except insider trading. I am NOT into politics and am NOT posting this for it's value to republicans, but just look at Nancy Pelosi getting 65% returns and beating out every hedge fund this year.
Furthermore, finance is dead - it's the "hot field" of the 80s / 90s. It has been commoditized and isn't interesting.
I say this as a CFA who also had various useless finance licenses like CFP, Series 7, 63, 6 etc and worked both on the sales / "advisor" (read Fidelity call center out of college, where I liked to point out that we wear suits and make less than garbagemen to coworkers) side of things and real analysis and still chose to go to IT the first chance I got.
> The Unusual Whales report also notes that of 100 stock-trading members of Congress, a third beat the S&P with their portfolios.
> Last year, the average Democrat nabbed returns of 31% – well ahead of the average Republican’s 18%. Unusual Whales notes Democrats are more invested in tech stocks – which surged in 2023 – while Republicans are more exposed to the banking and oil sectors.
I'm all for a ban in Congressional stock trading, but the idea that she needs to risk that with an already-wealthy VC husband with plenty of his own insider access seems similarly laughable. (Headlines also tend to call it her wealth, which seems pretty misleading.)
In 2022, their return was -19.8%. 2023 saw the market up enormously, and as my link indicates, Dems in Congress have been benefiting from a focus on tech stocks like Nvidia across the board.
I am more inclined to take that as an argument for "most of Congress" insider trades rather than "Nancy doesn't". I will leave that here though, long political argument ahead if we keep going. Agreeing to disagree. Also, thank you for the link, these stats definitely give a more balanced view.
> I am more inclined to take that as an argument for "most of Congress" insider trades rather than "Nancy doesn't".
1/3 beat the market; that means 2/3 did not. Right?
In a population of random idiots, you'd probably expect a certain amount to beat the market, a certain amount to match it, and a certain amount to flub.
They were likely flagged for generalizing. The quality of comments varies greatly depending on the topic. It's not fair to say that HN comments are generally abysmal. It is fair to be flagged for it, since it doesn't contribute anything of value to the discussion.
When I read it, your comment was invisible to most users and at the bottom of the page. Flagging is done by other users who are offended at what you say (presumably by the 'experts' who dismiss an experimental prototype aircraft because the new tech doesn't make sense for quadcopters..)
You can vouch though after clicking on the "... minutes ago" field, which is what I did in this specific case and apparently enough others to undo the flag.
Yeah. The Hacker News Guidelines say "No the website is not going downhill". But I can point to a shitton of threads from 2018 on often identical topics to threads today, where the quality of debate is quantitatively higher quality than it is today. Most of the people I know in Technology(tm) have not only stopped reading HN, but also derisively refer to it as The Orange Hellsite, because the quality of comments is often consistently worse than Reddit for comparable topics, these days.
There's a button the the profile page that brings you to the front page on the day you signed up. I just checked it the other way, things really went downhill. There is actually an open source project that banned referrals from HN due to the kind of toxic people they get from here. That's something.
> Most of the people I know in Technology(tm) have not only stopped reading HN, but also derisively refer to it as The Orange Hellsite, because the quality of comments is often consistently worse than Reddit for comparable topics, these days.
That's very unlikely. This website has not implemented the features that continuously make Reddit worse as time goes by - self-segregated communities and extensive down voting.
For every reddit comment there R, you can find a distinct comment here H, such that H is worse than R.
There's just way more informed expertise on Reddit. The big advantage of HN is that some tech luminaries post here. But the overall quality is much lower than the topic-reddits. It's more like an /r/technology.
I encourage you to read the site guidelines about commenting - because of how you've written comments, asked "What does it mean to be flagged for it?", and wrote this comment I'm guessing you're not familiar with them. A large problem seems to be that you don't understand what you are seeing or how the site works, and are leaping to uninformed conclusions.
If you have knowledge about the technology, I hope you will share it. You've posted three-ish comments that share only a tiny amount:
* This comment (and others in this thread), which contributes nothing to the discussion, degrades the dialog generally, and violates site guidelines.
* "Why?"
* A comment that leaps to a negative interpretation of someone else's comment and criticizes them, though also does provide some knowledge: https://news.ycombinator.com/item?id=38923926
Honestly, the quality is only lowered by this comment. You already replied to the drones thing. Writing a second, ranting, comment at the top level scaling up that comment to represent all of HN discussion of all time is just a bit silly.
Add in anything that’s even remotely related to intelligence or defence which is typically just filled with qanon style nonsense. I’ve noticed it for years as well, you aren’t wrong.
I don't know, I think there needs to be some form of unambiguous BS pushback signal, a gradient that starts with minimal intrusion on discussion along the lines of "people are starting to notice that some of us are talking past our pay grade." Not saying anything at all amounts to an endorsement of penalty free bullshiting, and after enough of this the hard-won cultural expectations start to shift about what constitutes acceptable participation.
There's a spectrum between Reddit on one end, and the typical IRC channel fiefdom with its mod-permissioned voicing, invisible banhammer tripwires, and admonitions to LuRK MoAR, on the other, and I think HN is in a sweet spot/zone somewhere between those extremes, but perhaps might need an adjustment in the direction of the latter.
Downvoting/flagging somewhat furnishes this signalling, but it's too ambiguous of a signal and is often abused by people who simply want to suppress information that is perfectly valid but not to their liking.
This is where a slashdot type of lightly sentiment-coded moderation system really may be worth bringing back into fashion.
It might be useful to have LLMs do automoderation on forums, tweaked by the moderators to shift the discussion the direction they want it to go. Have it so that the feedback is immediately on pressing the submit button rather than after-the-fact. And probably with more useful information to the poster than the "our users don't post messages like this" message.
I think it'd be useful to ban pun threads and other low effort shitposting, but it would probably have issues determining actual expertise from faux expertise. With the wrong settings it would be frustratingly useless, but over time some useful defaults should emerge.
The signal to noise ratio is so bad that addressing the problem head on seems like a valid solution. Is it the best solution? Maybe, maybe not, but I disagree that mentioning an acute problem is a self-awareness-less action. I doubt most readers are able to truly tell just how bad these comments are so I'm doing some sort of service to some people by calling it out.
Let me give an example for myself. I am not an expert in ML. I come to HN to learn about ML and I feel like I learn a good amount. I try to grok the comments, read the articles, etc. If I stumbled upon a bunch of very, very misguided comments I'd expect or hope that someone would say something so I could save myself some time. I see that kind of behavior a lot when users on HN call out "bad physics" but no one calls out bad aerospace.
Eh I guess it’s supposed to be water cooler talk for startup founders. The vibe would be different if people stuck only to what they know. We all know we’re ignorant, but it’s more fun to be interestingly wrong than boringly correct.
It says it reduces complexity, but does it? You still need the compressed air systems and and the control systems needed to inject exactly the right amount of air in the right places for the right amount of time. Sounds complex to me.
Some kinds of complexity are more fragile and easier to maintain than others.
Active flow control systems benefit from the fact that any individual valve has very little effect on the flight characteristics of the aircraft, making achieving high redundancy much easier. Also, the moving parts will be much smaller, and so easier to replace and maintain.
Keep in mind that traditional control surfaces need the complex hydraulic systems that already do something similar, so if there are other benefits to be gained (efficiency, post stall manoeuvrability) by the lack of the movable flap, it seems well worth a try.
After reading the article, it seems they want to have a plane that is controlled by little thrusters that can move the airplane in the desired direction - pretty much like spacecraft is being controlled in space.
I don't know how they will perform takeoffs and landings using this new system.
That is not what I understood. They are not thrusters, they work by changing the profile of the airflow rather than pushing the aircraft directly, in a way similar to flaps. They would not work in space.
I never said the plane would work in space, just that they would work like thrusters to change airplane direction. Just like a normal dual engine airplane would yaw if thrust becomes asymmetric, it could go up/down or roll just as easy if thrust is applied to push against any other surface.
> they would work like thrusters to change airplane direction
The thrusters don't push the plane. They push the boundary layer that lifts the plane.
It's not incorrect to think of conventional control surfaces as tools to physically push the boundary layer around, which is ultimately the mass that impacts the prevailing wind to create lift. This is just doing that with air. Aerodynamic, not astrodynamic or ballistic.
Having hundreds of tiny holes in the wing to release compressed air sounds mechanically too complicated.
But advanced jet engines have used the same technique INSIDE THE TURBINE BLADES for ~50 years now to keep them from melting, so it probably isn't too bad if the results are good. And it may be simpler and more reliable than the existing hydraulic systems.
I used to think these projects were cool and even strategized on bidding on some of them. Now I just see another face of the military industrial complex that’s destroyed our democracy and I don’t care what they’re making. The “defense” industry makes me sick.
This is like someone’s destroying my home and stops to show me how cool their hammer is.
Because the world is just full of airliners with ejection seats.
It's a technology demonstrator. They are testing a technology. For the reading challenged:
The X-65 will be built with two sets of control actuators – traditional flaps and rudders as well as AFC effectors embedded across all the lifting surfaces. This will both minimize risk and maximize the program’s insight into control effectiveness. The plane’s performance with traditional control surfaces will serve as a baseline; successive tests will selectively lock down moving surfaces, using AFC effectors instead.
That’s for testing purposes. For those reading challenged “Eliminating external moving parts is expected to reduce weight and complexity and to improve performance.”
Creates an interesting game theory case if every passager can action every other passenger’s. The equilibrium will either be an empty plane or a quiet plane.
Shouldn’t*. We let massive objects full of fuel that become uncontrollable if the engine fails drive through populated areas, and by the common clay of the west no less! Economics trumps safety, it’s all about the trade off our society is willing to make. And our society is willing to make some pretty huge ones.
I for one would not be worried about a slightly higher possibility of getting hit by a falling plane, unless this system was provably very unreliable or something.
Drones are sort of viewed as the future of military aerospace, or at least a large part of it, and are less well defined (hence needing DARPA research).
Airliners, even if they lose the big engines under the wings, still have a small one in the back, called an APU, that can provide power and bleed air (!) for all kinds of critical systems. A hypothetical airliner from the future relying on active flow control would absolutely have several redundant systems to ensure controllability.
A design in this vein might want to keep moving control surfaces locked down in all but extraordinary circumstances: spin recovery or flameout. Maximum g turns? For that matter, it's not crazy to think that they'd want to keep the moving control surfaces available for takeoff and landing.
I went through this idea in my head reading the sibling speculations about civilian use and discarded the idea: when you have the control surfaces, there's no cost in using them. In terms of aerodynamic inefficiency I'd expect it to be a tie at best, both are disturbances that make the flow worse to achieve an effect.
If they do discover a way to improve aerodynamic qualities with compressed air, chances are civilian aircraft would just switch it on whenever it helps and keep control going through conventional control surfaces just like before.
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.
The title's "no moving control surfaces" (both on HN and the DARPA site) contradicts the article itself:
> The X-65 will be built with two sets of control actuators – traditional flaps and rudders as well as AFC effectors embedded across all the lifting surfaces. This will both minimize risk and maximize the program’s insight into control effectiveness. The plane’s performance with traditional control surfaces will serve as a baseline; successive tests will selectively lock down moving surfaces, using AFC effectors instead.
> “The X-65 conventional surfaces are like training wheels to help us understand how AFC can be used in place of traditional flaps and rudders,” said Wlezien. “We’ll have sensors in place to monitor how the AFC effectors’ performance compares with traditional control mechanisms, and these data will help us better understand how AFC could revolutionize both military and commercial craft in the future.”
Was anyone else's first reaction to DARPA's "Artist's Rendering" to wonder "what new kiddie cartoon show is that from?"
What contradiction? The prototype has both types of control surface. It’s for testing the new tech; you don’t want it uncontrollable if something goes wrong with the new stuff.
It was a reasonable design decision to put both types of controls on the prototype.
But if I put chocolate chips in a cookie, claim that the cookie is chocolate-free, and then (when called on it) explain that the chocolate chips were only needed to make it taste good, while working on my cookie recipes - I still have lied.
Faulty analogy - "wireless internet" is a specific ~1/4-century-old computer set of technologies, and ~everyone knows that "wireless internet" devices still have plenty of cords.
His Majesty's English contains quite a few words - "mixed" and "hybrid" come to mind - which could very easily be used to describe the airplane. Without resorting to a cool-but-counter-factual headline.
BTW - how do you feel about Tesla's "Full Self Driving"?
You're gonna try that approach after the chocolate chip cookie one?
> BTW - how do you feel about Tesla's "Full Self Driving"?
That's a good analogy, actually. If it actually worked, it'd be fine to call it a "full self-driving car" even if it had a manual steering wheel option. Just like this prototype aircraft!
The problem with FSD isn't the fact that it also has a steering wheel, it's that it can't actually meaningfully function without the steering wheel.
Given a small Helion-type fusion reactor, crazy aircraft will be possible
from [1]:
> Electric AFC techniques use arrays of electrodes to discharge aerodynamic or electrical pulses to locally alter airflow. Effectors called synthetic jets – millimeter-wide openings in the aircraft surface that open into centimeter-wide cavities with diaphragms – rely on rapid voltage pulses to make diaphragms oscillate inward or outward, creating airflow sucking or blowing effects, much like a human lung.
> Electrically powered plasma actuators discharge pulses of electricity into the air through electrodes. The heat from the electricity turns the air into plasma, thermally altering flow vectors. All of these techniques have been researched through decades of AFC experiments in laboratories, wind tunnels and small-scale aircraft.
[1] https://www.aerospacetestinginternational.com/features/is-ac...