6 ms·
Dynamic soaring
- stavros 3y agoHere's what it looks like: https://www.youtube.com/watch?v=0nyYaL0dGAA https://www.youtube.com/watch?v=0nyYaL0dGAA
- jessriedel 3y agoHere's a really wonderful talk by Spencer Lisenby about the basic physics and Lisenby's work on pushing the speed https://www.youtube.com/watch?v=nv7-YM4wno8 https://www.youtube.com/watch?v=nv7-YM4wno8 Some other interesting HN comments: https://news.ycombinator.com/item?id=32739679 https://news.ycombinator.com/item?id=32739679 https://news.ycombinator.com/item?id=38653688 https://news.ycombinator.com/item?id=38653688
- adolph 3y agoThe Lisenby lecture is excellent.
- codethief 3y agoGreat article with some more background: https://newatlas.com/aircraft/dynamic-soaring-speed-record-spencer-lisenby/ https://newatlas.com/aircraft/dynamic-soaring-speed-record-s...
- croemer 3y agoWas about to share this here ;) RC glider going at nearly the speed of sound. Crazy! https://youtu.be/0nyYaL0dGAA?si=BM_M8ZkUEhoTLshk https://youtu.be/0nyYaL0dGAA?si=BM_M8ZkUEhoTLshk
- JKCalhoun 3y agoAmazing. I am having a hard time though separating dynamic soaring from ordinary slope soaring. I'll have to keep thinking on it until I understand it. Edit: very cool. I watched the video referenced in the HN comments (BTD10: The 835kph Sailplane and Dynamic Soaring) and I get it.
- stavros 3y agoSlope soaring is just riding a current that's going up because it hits a slope. Dynamic soaring is taking advantage of two masses of air of different speeds so you get a bunch of free airspeed as soon as you cross their barrier. Say you have a glider with a 2 m/s headwind. If you cross into a wind mass that's a 10m/s headwind, you've just gained 8 m/s of airspeed for free. Rinse and repeat.
- deleted 3y ago[deleted]
- hedgehog 3y agoFor anyone who hasn't seen the video: it's really worth watching with headphones on. It looks absurd and the sound is familiar to anyone who has spent any time around fast jets, but it's a glider.
- EdwardCoffin 3y agoThe third part of Neal Stephenson's novel Seveneves [1] has a neat application of this. [1] https://en.wikipedia.org/wiki/Seveneves https://en.wikipedia.org/wiki/Seveneves
- pavel_lishin 3y agoWhich part is that? I don't recall this bit being in the book.
- EdwardCoffin 3y agoThe first few pages of Part 3, when Kath 2 returns to the ring.
- taneq 3y agoOoh, sounds like what alba- oh here's the section on albatrosses. Super interesting, I was always dubious of those claims of "this bird only lands every 6 months" and the like, then I learned about the spiral glide pattern between two layers of windshear. It's fascinating (if no longer suprising) all the ways that nature has learned to harvest energy from the environment.
- tim333 3y agoWhile they only return to land occasionally they do land on the sea sometimes and need to go to it to feed and drink. On the other hand Swifts apparently can stay up for months. They eat flying insects so can stay in the air. https://www.latimes.com/science/sciencenow/la-sci-sn-common-swift-flight-20161027-story.html https://www.latimes.com/science/sciencenow/la-sci-sn-common-...
- psd1 3y agoThe idea of sleeping on the wing is mind-boggling
- yencabulator 3y agoConsider dolphins and think of a human sleeping while diving. "Sleep" is not quite the same across species.
- cedws 3y agoI've been watching a lot of glider videos on YouTube recently and it blows my mind that pilots can travel ~500km, even ~1000km with no propulsion, using only the lifting air. It would be a pretty good mode of transport if the general population could be trusted to responsibly and competently fly aircraft. Very low carbon.
- btreecat 3y agoYou should pay attention to the fatality rate for gliders. Some of the worst in maned aviation. It's considered 3-4x more dangerous than driving based on the annual fatality rate. Not that it isn't cool, it just won't become mainstream due to safety alone.
- croemer 3y ago3-4x more dangerous per what? Distance travelled, or time, or per year using average amounts that people drive/glide?
- croemer 3y agoIt's 50 times more dangerous than driving per hour: https://chessintheair.com/the-risk-of-dying-doing-what-we-love/ https://chessintheair.com/the-risk-of-dying-doing-what-we-lo...
- H8crilA 3y agoYou can fly even 3000km in a single day if you use lee waves, that's the world record. But gliding is really really far from being a viable transport, it's just a sport where you spend most of the time waiting for good weather. It's an exaggeration, but thinking that sailplanes could be used for commercial transport is almost like thinking that wave surfing could be used as such. We will sooner see some big return of airships than we will see commercial transport using gliders. As a sport it's absolutely breathtaking, it might be the best single thing that I've ever done. Please do mind the safety, though, it is not easy and it is not safe even though it may seem so after you've done your first ~hundred hours. It is a lot safer than paragliding because you'll crack the landing gear or the tail and not your spine on a bad landing.
- CrazyCatDog 3y agoThe rc gliders are loaded chock-full with weight (tungsten or lead), we literally seek cover behind cars and boulders, and the bravest among us holds the radar speed gun—-if you want to see something outside of this world, or spark your kids’ imaginations as to the universe unlocked by the sciences—visit a DS site! P.S. bring ski goggles—you’ll need them if the conditions are good, you won’t see without them if it’s a 400mph day—which is more and more common these days!
- mannykannot 3y agoIngo Renner (four times world gliding champion) reportedly demonstrated dynamic soaring in a human-carrying glider in 1977[1]. Trying to do so in the boundary layer at ground level would be extremely dangerous, if at all possible, but Renner's insight was that there is sometimes an exploitable windshear at a safe altitude, on the boundary of an inversion. From the article: "Renner has been attempting dynamic soaring for about four years, and the difficulties can be gauged from the fact that he has achieved only four really successful flights in that time." [1] Flight International, 22 October 1977 reprinted here (PDF): https://www.sac.ca/index.php/en/free-flight-magazine-2/1970s/1978/86-ff1978-04/file https://www.sac.ca/index.php/en/free-flight-magazine-2/1970s...
- Maarten88 3y agoThose RC dynamic soaring gliders pull up to 80G, which might also be an indication that this is probably not a good fit with manned flight.
- consumer451 3y agoThis concept may be applied to accelerating spacecraft. > Dynamic Soaring as a Means to Exceed the Solar Wind Speed https://arxiv.org/abs/2211.14643 https://arxiv.org/abs/2211.14643 Related video: https://youtu.be/SkGRVvA23qI?t=799 https://youtu.be/SkGRVvA23qI?t=799
- bjackman 3y agoI feel a bit silly here... but why do you keep your airspeed when you turn 180° after entering the faster-moving air? The article says "due to momentum" but that doesn't really make sense to me. It says "the tailwind has now accelerated the glider", but if it was all down to tailwind you would only be able to reach the groundspeed of the wind, after that there can be no tailwind right?
- hedgehog 3y agoThis is probably not exactly right but here's a way to think about it. Look at the diagram on the Wikipedia page. Set aside parasitic drag for a moment, and imagine the loop as four segments (up, downwind, down, upwind). Imagine the glider is headed straight up in the upward segment at speed X (air and ground for the sake of the example0, and the wind is moving at speed W. The wind pushes the glider's ground speed from 0 to W, adding momentum. Now the glider pulls into the downwind segment, translating the upward airspeed X into downwind air speed X and downwind ground speed X+W. As the glider pulls into the downward segment and into the lower region of still air the momentum translates into airspeed X+W, then it completes the loop and repeats. It's sort of like how if you push someone on a swing a little bit each oscillation you can keep adding energy even though your pushes aren't particularly fast or energetic.
- mannykannot 3y agoIt's not a silly question (apparently, more than just a few pilots don't understand this), and the phrase "the tailwind has accelerated the glider" is incorrect. What actually happens in any of the turns is that the glider undergoes a change of velocity equal to twice its original airspeed, in the direction opposite to which it was originally flying. This is simply a consequence of it flying an energy-conserving path (we are ignoring drag and also assuming the turn is made in level flight, so there's no change of potential energy.) When measured in a frame of reference moving with the wind, with W as the wind speed and A as the air speed, a glider flying upwind has a velocity of -A, and after turning 180 degrees has a velocity of +A. The magnitude of both velocities is the same. From the ground frame of reference, it has gone from W-A to W+A, so the magnitude has increased, from the difference to the sum. In both cases, the change in velocity is +2A, regardless of how strong the wind speed is or whether there is any wind. The appearance of there being an acceleration when the wind is blowing but not when it is still results from considering the change of ground speeds before and after, instead of change in velocities (measured in any inertial frame of reference, as long as it is the same one before and after.) It is not easy to see intuitively how this allows the kinetic energy of the glider to keep on increasing, but perhaps this will help: the 180 degree turns are like elastic collisions (i.e. without energy loss) between the glider and the air. From this perspective, we can make an analogy with a bat and an elastic ball: if you bounce the ball between the bat and the floor, striking it downwards each time it bounces back, it will keep on picking up speed: it rebounds from each blow you give it faster than it was coming up, and it keeps that newly-acquired speed when it bounces back off the floor. In this analogy, the bat stands for the wind at altitude, and the floor stands for the still air below.
- HPsquared 3y agoSoaring in general seems like a ripe opportunity for automation. If someone makes software that can seek out and make use of lift (using various information sources), it could pave the way for very low-energy drones. EDIT: Interesting.... seems there is something already that handles the "circling and staying in thermals" part. https://ardupilot.org/plane/docs/soaring.html https://ardupilot.org/plane/docs/soaring.html https://arxiv.org/abs/1802.08215 https://arxiv.org/abs/1802.08215 "ArduSoar: an Open-Source Thermalling Controller for Resource-Constrained Autopilots"
- lightbulbjim 3y agoYeah, except the fun part of soaring is the flying. Programming flight controllers is boring.