Boundary layers, drag (pressure vs skin friction) & heat loads

19:26also the case that because of the lack of to be able to do hypersonics is extremely expensive Yeah. >> And it's also classified. >> Yeah. >> And so the amount of actual source for data >> to inform the models >> is not really accessible. >> Yeah. >> In terms of having a feedback loop for how you iterate on your model's predictions. >> Yeah. >> And so you're kind of extrapolating from what you can get. But it's an environment because of this laminer flow to turbulent flow and these new problem sets that happen when you start going hypersonic. >> Yeah. the ability to have a feedback loop from real world real world data sets is kind of a cha it's a little bit

20:06of a challenge. >> It is a little bit of a challenge and you know I will I will go out on a limb and say that even the classified programs haven't really crap cracked like greater than five mock. >> Okay. >> Okay. Because because >> some of this fundamental physics is just like so foreign. >> Yeah. that like there hasn't been fundamental research that's happened to figure that out. Maybe they've cracked it for small things, right? Missiles. Okay. Right. But like you're putting a human in something that's going hypersonic. >> Yeah. Yeah. >> No, that's a different No, that's that's actually No, you could you could be going at Mach 10. You could be going at Mach 10 in the

20:47upper upper upper Earth's atmosphere. Yeah. Right. >> Yeah. >> There's not that many particles. The density of air is low. >> I mean, okay. Is the International Space Station going at Mach 90 or whatever the hell? Right. It's not really a thing. >> Yeah, that's fair. >> Right. That's fair. >> But but when when densities are high, >> right, >> then it >> it's a different it's a different >> it matters. >> It's a different like animal altogether, right? And even I mean one of the things that I I would suggest is the space shuttle for example, right? The orbiters, they had these overdesigned tiles, the heat absorbing tiles on the on the very end. They were overdesigned because predictive models of that turbulence of the laminer from turbulent

21:29background. >> Yes. >> Were so bad that they were just like, "Okay, I'm just going to make this like 10 times >> what I need." >> Right. >> Right. Because I don't know where that transition is and I don't know the physics of that. >> So I'm just going to I'm just going to overdesign for safety reasons. Right. >> So So it shows you that I mean I mean I'm sure like the top echelons of NASA have access to some of the hypersonic stuff, >> but but I don't know. But a key point is as far as we know at this point in time in the public data realm, hypersonics are exclusively for >> payloads like missiles, not for human travel. >> Exactly. Which is they're very different. >> Those are very different things like like like a human life is worth way more

22:11than some nuclear thing that I just like made as I'm I'm testing. Yes. You know. >> Yes. No. No. But that that that is the that is the key thing. >> That's the key thing and that's where this paper comes in. Okay. >> Okay. Okay. The central challenge of hypersonic design is predicting and modeling that turbulent boundary layer. Right? And this paper is doing an experimental >> addressing >> of that >> of that problem. Okay. And that's why I think it's very it's very exciting. Okay. What it's doing is basically testing a 60-year-old hypothesis. Okay. It's a it's called a Morov hypothesis. And what it says is the essential dynamics of this like very high-speed

22:52high mock turbulence is not fundamentally different from low mock turbulence. >> Okay. >> Okay. Morov came up with this in 1962. He was looking at some preliminary data and he said that this seems to be true. Okay. It's essentially the same. What he's saying is at high moach air is going to become compressible and there's going to be all of these density fluctuations and temperature fluctuations. But what I can do is I can take the physics that I know from low mock and I can do a transformation.