I hate to be a science Kill-joy, but...

[cthulu2016]

Last edited Sun Oct 14, 2012, 02:50 PM - Edit history (3)

This guy is going to shortly jump out of a capsule about 20 miles up and free-fall, becoming the fist human to break the speed of sound outside a vehicle.

http://www.redbullstratos.com/live/

When he jumps the atmospheric pressure will be less than 0.2 psi, versus 14 psi on the ground.

Um... what is the speed of sound in a gas at 0.2 psi? It is a lot lower than what we call the speed of sound. (768 mph in dry air at room temperature sea level.)

(ON EDIT: The PSI does not have any effect on speed of sound in a gas unless pressure and density are for some reason not interchangable, but despite that error on my part, the speed of sound where he was was lower than we are used to,)

The speed of sound is not a constant like the speed of light. It is determined by the material the sound is passing through. For instance, the speed of sound through metal is very fast.

So I am not sure what to make of this free-falling guy going supersonic.

After he breaks the speed of sound 20 miles up he will slow down considerably closer to Earth— the air gets denser. The terminal velocity of a human body near the Earth is about 200 kilometers/hour which is why some people have survived falling out of airplanes.

[Democratopia]

1. I agree. When I first heard this, I thought t this guy is going to hit the ground dead.

[aletier_v]

4. He still might. Hopefully he has an automatic chute release

In case he passes out.

[Posteritatis]

7. He's in a spacesuit for all practical purposes, so the altitude isn't going to hurt him. (nt)

[aletier_v]

11. yes but he'll be accelerating pretty quickly. He might pass out from stress, too.

The live feed is more interesting than i expected.

[Posteritatis]

14. He'll accellerate at the exact same rate all falling objects do. (nt)

[aletier_v]

16. Ahem. there's a chart in the thread here about wind resistance

He'll be falling faster at the start.

Also, commentator mentioned tumbling, so I imagine he could go into a spin and lose consciousness too.

At any rate, they also mentioned automatic deployment mechanism, which I expected to be there.

[Posteritatis]

17. Gravity doesn't change with altitude. (nt)

[dems_rightnow]

23. Of course gravity changes with altitude

The further one gets from the earth's core, the less the gravity effect. If you go far enough, you go into orbit.

[wtmusic]

26. Not significantly in this case

About .01 times less gravity from 20 miles up.

[Posteritatis]

27. He didn't jump from orbit, and gravity doesn't *increase* with altitude either.

You need to spend some time reading about both gravity and orbital mechanics, because you're really, really not understanding either.

[dems_rightnow]

34. Thanks!

For setting me straight on my contention that he jumped from orbit, and that gravity increases with altitude.

[wtmusic]

21. No more likely to go into a spin than if he jumped from 10,000 ft.

The wind resistance will never be more than his weight, no matter how fast he's going.

[kestrel91316]

2. I predict a Darwin Award for this guy. I can't see this actually succeeding.

[cynatnite]

5. He did it at 90 or 95,000 feet a few months ago....

Plus he's been training 4 years for this.

[Posteritatis]

8. And there were jumps above 100,000 feet as far back as 1960. (nt)

[obamanut2012]

25. Jo Kittinger did it at 103,000 feet 52 years ago

Why did you think Felix wouldn't succeed?

[Logical]

30. Darwin award?? WTF, you think he is stupid or something??

[Jamastiene]

36. Nice post, Nostradamus. n/t

[kestrel91316]

37. LOL. I was sure he was gonna die.

[Wounded Bear]

3. Ummmm....the speed of light varies by the medium, too....

It's faster in a vacuum than in air or glass. That's why prisms work.

[cthulu2016]

9. True. Slight varriability, but true.

[bananas]

6. speed of sound vs altitude

http://en.wikipedia.org/wiki/Speed_of_sound

Density and pressure decrease smoothly with altitude, but temperature (red) does not. The speed of sound (blue) depends only on the complicated temperature variation at altitude and can be calculated from it, since isolated density and pressure effects on sound speed cancel each other. Speed of sound increases with height in two regions of the stratosphere and thermosphere, due to heating effects in these regions.

[morningfog]

10. So, will he break the sound barrier or not?

That is really the only question.

[cthulu2016]

12. He will break the sound barrier where he is...

but will not exceed 768 mph.

[Indpndnt]

13. Heretic!! There is no such thing as science!

[url=http://www.cosgan.de/smilie.php][img][/img][/url]

I'm wondering what, if anything (beyond publicity), this guy is thinking, too. The numbers will make this very interesting, perhaps a bit too interesting for his wellbeing.

[surrealAmerican]

15. Would this mean that astronauts ...

... on "space walks" have already broken the speed of sound while not in a vehicle?

[Posteritatis]

18. Astronauts on spacewalks are moving about Mach 25-30 relative to the ground. (nt)

[wtmusic]

19. "Wind is out of the west, I mean out of the east..."

Mission Control not exactly to NASA standards

[obamanut2012]

28. That was 84-year-old Col. Joe Kittinger (ret.)

Why jumped from 103,000 feet in 1960, and, even after today, still has the longest freefall ever recorded.

Felix wanted only him to speak to him today, as he is the only living person who would understand what he was going through.

[wtmusic]

32. OK he gets a pass. nt

[wtmusic]

20. Air pressure makes no difference in the speed of sound; temperature does

http://wiki.answers.com/Q/Does_the_speed_of_sound_in_air_depend_upon_the_atmospheric_pressure

[cthulu2016]

22. You're right (99%)

I was mostly wrong and you are mostly right, but though pressure and density are closely related they are not precisely the same thing, so air pressure (and or gas density) does have a slight effect.

The composition of the atmosphere is probably different at 20 miles up, which does have an effect. And the temperature, of course.

Anyway, I went about it wrong but got the right answer accidentally—he didn't break what we think of as the speed of sound, but did break the speed of sound for the atmosphere he was in.

[Xipe Totec]

29. There is a slight variation depending on temperature, not pressure.

I should know, I worked on shuttle entry to landing navigation, and calculating mach was critical.


When calculating the speed of sound forget the atmospheric pressure, but look accurately at the very important temperature. The speed of sound varies with altitude (height) only because of the changing temperature there!

http://www.sengpielaudio.com/calculator-speedsound.htm

[TeamPooka]

24. He nailed the fall and the landing!

[Posteritatis]

33. Between the stiff suit and the ridiculous spin, the landing was amazing. (nt)

[Logical]

31. Something tells me you don't "hate to be a science killjoy" ever!

[cthulu2016]

35. No, I am a huge fan of science and scientific wonder

I usually post to increase the joy found in science.

But I am a skeptic, by temperment, and when someone says this guy will break the speed of sound I thing, "Which speed of sound?"

But the shot of him standing on the capsult edge looking down was truly beautiful.

[Bake]

38. Glad he survived, but wasn't that kind of stupid?

Does a human REALLY have to do everything?

No. We don't.

Bake

[Bake]

39. Who wants to be the first human to survive jumping into a volcano????

Yeah. I didn't think there'd be a lot of volunteers.

Bake