How Hypersonic Wind Tunnels Recreate Mach 20

Wind tunnels have been part of aviation research since before the first powered aircraft took to the skies. And there are a huge range of capabilities available to researchers, including the ability to test models are mach numbers close to orbital velocity.

I discovered the thumbnail image on a NASA page showing a Mach 20 helium wind tunnel testing a model of the Space Shuttle Orbiter and thought it was worth explaining how all this comes together to create the image.

If you want to read more about the evolution of wind tunnels there's a book which primarily covers NASA's (and NACA's) wind tunnels

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[VinayPai]

I'm surprised Destin from Smarter Every Day didn't get summoned when you said "laminar flow" at 1:25.

[LeoHL]

I studied aeronautical engineering years ago, and got to use a wind tunnel for a project, it was subsonic, but we also had a blow down supersonic wind tunnel, that one worked by decompressing a chamber, and compressing another, and quickly releasing the pressure, and using a trigger to start a camera to record the shock waves around the model in the test section :)

[devincastellucci]

This was a fascinating topic and a fabulous job explaining it.

[johnturnbull]

Impressive! I am ashamed to say I am supposed to know all this ( I do really) but would trip over myself trying to explain it to the layman. Scott does a great job leading you through the subject starting from the basics, explaining the issues and they way they have been resolved to achieve Mach 20. I am very impressed.

[mkllove]

Thanks Scott ! This was a reminder of a great job I had in late 80's in Rocket Test for ARC ( now Aerojet I think ) that had a huge "Air Facility" as it was called in those days. I think it was an amalgam of ex NASA equipment that allowed them to test fire not models, but the actual full size SM-2 Standard Missile recreating it's entire flight profile while the motor operated, generating performance test data to qualify systems for manufacturing. They even had an expansion system around nozzle's exit to recreate lower external air pressures at altitude. It was a blowdown system with about a dozen immense tanks on railroad cars that took days to fill with the required compressed air it expended in tests. They literally flew the missile in a high speed wind tunnel while the rocket motor operated in real world test conditions ! They also did extensive ramjet testing with same facilities. I sometimes wonder if any of that stuff is still being used to test next gen systems currently ?

[SuperDwarf]

In 1968 I was stationed at NAS Moffet Field were Nasa Ames Research center. The wind tunnel would keep us awake, great stuff

[miroslavmilan]

This must be one of your best videos ever. Really succinct explanation and enjoyable narration.

[daniloduarte]

I am often impressed by how good and specific to the subject the visuals in these videos are. How do you usually go about finding the right images?

[eddiezebeast]

"But in the end, after testing, it was vastly more successful at converting aviation fuel into noise pollution" How much do I like these sarcastic quotes 😁

[WWeronko]

As a mechanical engineer, I have often said to disbelieving laymen, that engineers are some of the most creative people alive. This video does a good job at validating that concept. Thank you Scott.

[Zeusbeer]

My university has a mach 10+ wind tunnel, it doesn't run for very long though. I would love to get to use it one day.

[debrabuck]

I thought that i saw a shock spike while traveling in commercial aircraft when the light was just right. Thanks for confirming.

[Mosern]

Its Friday afternoon, and I learned more about hypersonic wind-tunnels. It is great that school honed my skills at acquiring knowledge I will never need in real life. I quite enjoyed that.

[rogerstone]

WONDERFUL video. This is why we come here. Thank you Scott. (PS - why didn't they just use the whirlpool vortex at the end of your video? WAY over mach 20, I'll bet.)

[flappergast]

Hi Scott - why are you so awesome!!! This is once again an amazing story about several amazing physical effects. KEEP IT COMING!

[alexeytsybyshev]

I think the reason for using Helium is that, temperature being proportional to the kinetic energy of gas molecules mv^2/2, the lower the mass of the molecule, the lower the temperature (and energy) needed to achieve the same velocity. That is why Helium needs much less heating than air to reach Mach 20. I think this was also used to fire a hypersonic Helium pellet gun in some video.

[alexwebster]

Great video. In case nobody else has mentioned it, I recommend the book "Facing the Heat Barrier" by T.A. Heppenheimer. The first part of the book goes into some detail about the different wind tunnels developed during the early years of the space age, and why they were necessary. It's an absolute must-read if you are interested in how the problems of heat were solved for ICBMs, Apollo, the X-15 and Space Shuttle.

[Sirmellowman]

my entire life anytime I heard the term "supersonic or hypersonic wind tunnel" I always wondered how the heck they would ever achieve those speeds in a wind tunnel. this has been very enlightening for me. thank you for the great video!

[el-domo]

Speaking of wind tunnels, please please feel free to use our open source wind tunnel to use for schools and other activities or just for yourself to have fun. You can find it in our channels. Go ahead and enjoy it.

[brianmann]

You mentioned that wind tunnels use vast amounts of power. In the 1980's I worked at a nuclear power plant (Surry) that was close to the Langley 30 by 60 foot wind tunnel. Surry put out about 2000 megawatts of electricity. When the wind tunnel would start, the power draw on the grid would slow down the generators and lower the frequency across the Virginia grid, and the operators at the plant would have to adjust nuclear power to compensate. A staggering amount of power was being drawn.