7 ms·

Reading this, I just realized that I bet we do more and more testing of cutting edge aircraft in computer simulations nowadays, waiting until later in the stage

by atonse 9y ago

Reading this, I just realized that I bet we do more and more testing of cutting edge aircraft in computer simulations nowadays, waiting until later in the stage to actually build prototypes. This might also explain why we've got fewer "UFO" sightings than we used to even 20-30 years ago, in spite of all of us carrying cameras in our pockets (apart from the fact that many of these were hoaxes to begin with).

godelmachine 9y ago
I don't think even modern day smartphones are fast enough to capture objects traveling at hypersonic speeds. Just a guess, I may be wrong here.
- Retric 9y ago
  Distance makes speed irrelevant. The moon is traveling 1km every second but that's hard to directly notice. If you every watched a jet moving at ~600mph then I think we can agree something going 10 times as fast would still be easy to notice.
  - maxerickson 9y ago
    Possible to capture if you noticed it anyway. Jets cross out of view in a couple minutes and are big (and probably flying lower). So a little thing in ~20 seconds.
    - Retric 9y ago
      If it's tiny, dark, and distant then it's hard to see even if stationary. Thus the real issue would not be speed.
      - maxerickson 9y ago
        Yeah, I was agreeing with that part of you comment and quibbling over "easy to notice". Even with the tiny size the speed is still a big factor because the opportunity to sight the object from a given location will be pretty short.
- SEJeff 9y ago
  Take something like an SR-71 blackbird... It flew subsonic until it was often near the edge of space. If it was vaguely near takeoff or landing, it would be possible to see with the naked eye. If you're a fan of the SR-71, this hilarious interview with pilot Brian Shul is definitely worth watching: https://www.youtube.com/watch?v=MmyAvRKDvJk https://www.youtube.com/watch?v=MmyAvRKDvJk
- maxxxxx 9y ago
  They are able to capture rocket launches so it should be OK. A hypersonic plane will be very high altitude so it won't move across the sky that fast. The ISS needs several minutes to cross the sky.
- akhatri_aus 9y ago
  It's not going to be hypersonic 100m from the earth's surface, or it'll burn up. So it wont be because of speed i'tll just be too far away.
Jtsummers 9y ago
For hypersonic it's been all about computer simulations. The costs are just too high. The tests for such aircraft are very expensive and typically result in catastrophic failure (complete loss of the system). Though they learn a lot about what works and doesn't in each test. A major driver for better CFD has been to better simulate hypersonic speeds and reduce the number of real test flights needed. https://www.google.com/search?q=hypersonic%20flight%20test%20failure&cad=h https://www.google.com/search?q=hypersonic%20flight%20test%2...
- phkahler 9y ago
  Someone in the FEA/CFD/Simulation industry upon seeing the SpaceX video on their capability indicated that no commercial product he was aware of could match what they were doing. Firewall won't let me confirm this link is correct: https://www.youtube.com/watch?v=txk-VO1hzBY https://www.youtube.com/watch?v=txk-VO1hzBY SpaceX has best in class hypersonic combustion CFD capability that runs on a GPU. Written in-house.
  - Balgair 9y ago
    To be fair, it is a VERY hard problem. 'Most' airplanes are designed in a laminar flow situation. Meaning that turbulence is just left out. This makes the calculations much easier, as you can set boundary conditions. In super-sonic conditions, the air is no-longer in-compressible, so the boundary conditions change and you have to add more variables to the equations. In hyper-sonic flow, the air itself is now a variable, as the molecules are split and recombine along the wing in ways we have not yet even empirically measured. This ads a complexity to the equations that is very large and the 'educated guess' of those chemistries on the wing becomes very important.
    - phkahler 9y ago
      ...as the molecules are split and recombine along the wing in ways we have not yet even empirically measured. I'm sure one can speculate. In the video they do talk about all the possible intermediate species, so one might have to add air molecules (which can break apart and add to the reactants) to the mix. But yeah, lots of unknowns. Doing experiments and comparing to the simulations should help figure it out. The problem has traditionally been an inability to do the simulations, but that's possible now.
tzs 9y ago
> This might also explain why we've got fewer "UFO" sightings than we used to even 20-30 years ago, in spite of all of us carrying cameras in our pockets. At night, though, we can still see a lot better than the cameras in our phones. For instance, I saw something weird one night. It was big enough and bright enough that I had no trouble seeing it, but my iPhone 6 plus camera just got a vague blob. This was not a UFO, since among other things it was on the ground, but it illustrates the limits of the cameras. (In case anyone is curious, I'll describe what I saw at the end of this comment). The most interesting current UFO reports I've seen (interesting in the sense that they are probably something real--not aliens or supernatural stuff of course, just either an unknown natural phenomenon or some manmade thing that is not well known) are where people see what looks like a star, but moving in a straight line (sometimes pausing now and then), that then suddenly changes direction and zooms off over the horizon very suddenly. No way is a phone camera going to capture that. The weird thing I saw: this was the night before the 2017 total solar eclipse in the US. I was parked in a big field that had been turned into a car camping area for the eclipse and the day/night before. A few rows down and a couple dozen spots to the left I saw what looked like two copies of a movie or TV show side by side, kind of wavy and translucent. It looked like either they had hung up a sheet and were projecting video onto it, or they had a couple of flat panel displays and there was a sheet between them and me. Then what looked like an arm poked up. If they had been in a tent I would have said it looked like someone in the tent was pushing up on the top, stretching the tent--but tents were not allowed. (There were some trucks and vans that had tent-like extensions on top, so they may have had something like that). The arm moved back and forth a while, and then was apparently pulled down. Then what looked like a leg replaced it...but it was a huge leg. It looked to be about 2 meters long. The "leg" started moving rapidly back and forth along what would be the length of the vehicle. After it had done this a few times, it disappeared. (There may have also been an arm or two mixed in here). Then a light rose up from the middle of the vehicle. I though it might be a flashlight. It then stopped rising, and started turning. It continued turning until it was pointing right at my car, and then it stopped turning for about 10 seconds. Finally, it resumed turning until it went all the way around, and then it descended, and things were dark, with no activity at that other vehicle. I thought "what the hell was all that?". Then the images came back, and the whole thing repeated! The third time it happened I had my phone out and the camera recording. Unfortunately, all the recording shows is that there was some lights moving around in that direction.
andrewla 9y ago
I don't think there are fewer "UFO" sightings than there were 20-30 years ago. I think there are way more. You don't have to dig very far on YouTube to find giant communities of people who are "seeing" UFOs. Video evidence of UFOs is easy to collect -- all you need to do is not identify the objects in the sky. And there are all sorts of weird things in the sky -- reflected lights and spotlights, weather balloons (and regular balloons), drones, sundogs, regular planes, satellites and the ISS, even the occasional actual meteor. It's also much easier to ignore these things, since most of them are just ordinary things that the person who took the video doesn't know how to identify. If you made a great UFO hoax now, chances are nobody would ever see it who was the least interested in looking at it skeptically, because it would be lost in the noise of people seeing trash bags blowing in the wind. So I think that https://xkcd.com/1235/ https://xkcd.com/1235/ is premature about UFOs, though I think it's pretty conclusive about lake monsters and bigfoot (although if you look around, people see a lot of strange looking mangy bears that people think are bigfoot).
- jandrese 9y ago
  One thing that is getting harder is taking really shitty video that is impossible to interpret. Phone cameras are getting better every year so the kind of grainy shaky stuttery video you normally get with these cases becomes harder and harder to justify.
ggm 9y ago
http://hypersonics.mechmining.uq.edu.au/facilities http://hypersonics.mechmining.uq.edu.au/facilities there are still places which put models into chambers. (I know, I used to work behind this one, and we have a steel membrane punched through by the airblast to make the shockwave from the dumpster out back)
- chrisbennet 9y ago
  ”I know, I used to work behind this one, and we have a steel membrane punched through by the airblast to make the shockwave from the dumpster out back” I can’t parse this sentence. Could you explain? Thx
  - BoorishBears 9y ago
    I think the commenter is trying to say they have a steel membrane that had a hole punched through it by an air-blast. Said membrane came from the dumpster out in back.
    - ggm 9y ago
      http://hypersonics.mechmining.uq.edu.au/t4 http://hypersonics.mechmining.uq.edu.au/t4 the part called "primary diaphragm"
    - chrisbennet 9y ago
      Thanks!
azernik 9y ago
And also of engines - one of the reasons relatively small companies like SpaceX and Blue Origin can design their own high-performance rocket engines is that they can simulate combustion and fluid flow using CFD techniques. Back in the F1 days they had to light up the engine and come up with interesting ways to observe the internal processes and debug instabilities; now many of those debug cycles (and associated manufactured test articles) are unnecessary. You still have to build the thing to catch some bugs, but that's gotten much cheaper.
- Gravityloss 9y ago
  Also CNC and 3D printing have made iterating hardware more possible with less labor. One person teams now can get liquid rocket motors printed. Of course turbopumps are many levels from that.

by atonse 9y ago

godelmachine 9y ago

I don't think even modern day smartphones are fast enough to capture objects traveling at hypersonic speeds. Just a guess, I may be wrong here.

Retric 9y ago
Distance makes speed irrelevant. The moon is traveling 1km every second but that's hard to directly notice. If you every watched a jet moving at ~600mph then I think we can agree something going 10 times as fast would still be easy to notice.
- maxerickson 9y ago
  Possible to capture if you noticed it anyway. Jets cross out of view in a couple minutes and are big (and probably flying lower). So a little thing in ~20 seconds.
  - Retric 9y ago
    If it's tiny, dark, and distant then it's hard to see even if stationary. Thus the real issue would not be speed.
    - maxerickson 9y ago
      Yeah, I was agreeing with that part of you comment and quibbling over "easy to notice". Even with the tiny size the speed is still a big factor because the opportunity to sight the object from a given location will be pretty short.
SEJeff 9y ago
Take something like an SR-71 blackbird... It flew subsonic until it was often near the edge of space. If it was vaguely near takeoff or landing, it would be possible to see with the naked eye. If you're a fan of the SR-71, this hilarious interview with pilot Brian Shul is definitely worth watching: https://www.youtube.com/watch?v=MmyAvRKDvJk https://www.youtube.com/watch?v=MmyAvRKDvJk
maxxxxx 9y ago
They are able to capture rocket launches so it should be OK. A hypersonic plane will be very high altitude so it won't move across the sky that fast. The ISS needs several minutes to cross the sky.
akhatri_aus 9y ago
It's not going to be hypersonic 100m from the earth's surface, or it'll burn up. So it wont be because of speed i'tll just be too far away.

Jtsummers 9y ago

For hypersonic it's been all about computer simulations. The costs are just too high. The tests for such aircraft are very expensive and typically result in catastrophic failure (complete loss of the system). Though they learn a lot about what works and doesn't in each test. A major driver for better CFD has been to better simulate hypersonic speeds and reduce the number of real test flights needed. https://www.google.com/search?q=hypersonic%20flight%20test%20failure&cad=h https://www.google.com/search?q=hypersonic%20flight%20test%2...

phkahler 9y ago
Someone in the FEA/CFD/Simulation industry upon seeing the SpaceX video on their capability indicated that no commercial product he was aware of could match what they were doing. Firewall won't let me confirm this link is correct: https://www.youtube.com/watch?v=txk-VO1hzBY https://www.youtube.com/watch?v=txk-VO1hzBY SpaceX has best in class hypersonic combustion CFD capability that runs on a GPU. Written in-house.
- Balgair 9y ago
  To be fair, it is a VERY hard problem. 'Most' airplanes are designed in a laminar flow situation. Meaning that turbulence is just left out. This makes the calculations much easier, as you can set boundary conditions. In super-sonic conditions, the air is no-longer in-compressible, so the boundary conditions change and you have to add more variables to the equations. In hyper-sonic flow, the air itself is now a variable, as the molecules are split and recombine along the wing in ways we have not yet even empirically measured. This ads a complexity to the equations that is very large and the 'educated guess' of those chemistries on the wing becomes very important.
  - phkahler 9y ago
    ...as the molecules are split and recombine along the wing in ways we have not yet even empirically measured. I'm sure one can speculate. In the video they do talk about all the possible intermediate species, so one might have to add air molecules (which can break apart and add to the reactants) to the mix. But yeah, lots of unknowns. Doing experiments and comparing to the simulations should help figure it out. The problem has traditionally been an inability to do the simulations, but that's possible now.

tzs 9y ago

> This might also explain why we've got fewer "UFO" sightings than we used to even 20-30 years ago, in spite of all of us carrying cameras in our pockets. At night, though, we can still see a lot better than the cameras in our phones. For instance, I saw something weird one night. It was big enough and bright enough that I had no trouble seeing it, but my iPhone 6 plus camera just got a vague blob. This was not a UFO, since among other things it was on the ground, but it illustrates the limits of the cameras. (In case anyone is curious, I'll describe what I saw at the end of this comment). The most interesting current UFO reports I've seen (interesting in the sense that they are probably something real--not aliens or supernatural stuff of course, just either an unknown natural phenomenon or some manmade thing that is not well known) are where people see what looks like a star, but moving in a straight line (sometimes pausing now and then), that then suddenly changes direction and zooms off over the horizon very suddenly. No way is a phone camera going to capture that. The weird thing I saw: this was the night before the 2017 total solar eclipse in the US. I was parked in a big field that had been turned into a car camping area for the eclipse and the day/night before. A few rows down and a couple dozen spots to the left I saw what looked like two copies of a movie or TV show side by side, kind of wavy and translucent. It looked like either they had hung up a sheet and were projecting video onto it, or they had a couple of flat panel displays and there was a sheet between them and me. Then what looked like an arm poked up. If they had been in a tent I would have said it looked like someone in the tent was pushing up on the top, stretching the tent--but tents were not allowed. (There were some trucks and vans that had tent-like extensions on top, so they may have had something like that). The arm moved back and forth a while, and then was apparently pulled down. Then what looked like a leg replaced it...but it was a huge leg. It looked to be about 2 meters long. The "leg" started moving rapidly back and forth along what would be the length of the vehicle. After it had done this a few times, it disappeared. (There may have also been an arm or two mixed in here). Then a light rose up from the middle of the vehicle. I though it might be a flashlight. It then stopped rising, and started turning. It continued turning until it was pointing right at my car, and then it stopped turning for about 10 seconds. Finally, it resumed turning until it went all the way around, and then it descended, and things were dark, with no activity at that other vehicle. I thought "what the hell was all that?". Then the images came back, and the whole thing repeated! The third time it happened I had my phone out and the camera recording. Unfortunately, all the recording shows is that there was some lights moving around in that direction.

andrewla 9y ago

I don't think there are fewer "UFO" sightings than there were 20-30 years ago. I think there are way more. You don't have to dig very far on YouTube to find giant communities of people who are "seeing" UFOs. Video evidence of UFOs is easy to collect -- all you need to do is not identify the objects in the sky. And there are all sorts of weird things in the sky -- reflected lights and spotlights, weather balloons (and regular balloons), drones, sundogs, regular planes, satellites and the ISS, even the occasional actual meteor. It's also much easier to ignore these things, since most of them are just ordinary things that the person who took the video doesn't know how to identify. If you made a great UFO hoax now, chances are nobody would ever see it who was the least interested in looking at it skeptically, because it would be lost in the noise of people seeing trash bags blowing in the wind. So I think that https://xkcd.com/1235/ https://xkcd.com/1235/ is premature about UFOs, though I think it's pretty conclusive about lake monsters and bigfoot (although if you look around, people see a lot of strange looking mangy bears that people think are bigfoot).

jandrese 9y ago
One thing that is getting harder is taking really shitty video that is impossible to interpret. Phone cameras are getting better every year so the kind of grainy shaky stuttery video you normally get with these cases becomes harder and harder to justify.

ggm 9y ago

http://hypersonics.mechmining.uq.edu.au/facilities http://hypersonics.mechmining.uq.edu.au/facilities there are still places which put models into chambers. (I know, I used to work behind this one, and we have a steel membrane punched through by the airblast to make the shockwave from the dumpster out back)

chrisbennet 9y ago
”I know, I used to work behind this one, and we have a steel membrane punched through by the airblast to make the shockwave from the dumpster out back” I can’t parse this sentence. Could you explain? Thx
- BoorishBears 9y ago
  I think the commenter is trying to say they have a steel membrane that had a hole punched through it by an air-blast. Said membrane came from the dumpster out in back.
  - ggm 9y ago
    http://hypersonics.mechmining.uq.edu.au/t4 http://hypersonics.mechmining.uq.edu.au/t4 the part called "primary diaphragm"
  - chrisbennet 9y ago
    Thanks!

azernik 9y ago

And also of engines - one of the reasons relatively small companies like SpaceX and Blue Origin can design their own high-performance rocket engines is that they can simulate combustion and fluid flow using CFD techniques. Back in the F1 days they had to light up the engine and come up with interesting ways to observe the internal processes and debug instabilities; now many of those debug cycles (and associated manufactured test articles) are unnecessary. You still have to build the thing to catch some bugs, but that's gotten much cheaper.

Gravityloss 9y ago
Also CNC and 3D printing have made iterating hardware more possible with less labor. One person teams now can get liquid rocket motors printed. Of course turbopumps are many levels from that.