23 mile skydive!

I've heard more intelligent people than myself saying that using Hydrogen would have offered maybe 8% more lift? I imagine that when the air gets to such a low density at those heights, the difference between helium and hydrogen becomes negligible, due to the fact that I think it is the difference between the outside air and the internal helium/hydrogen which causes the balloon to ascend, therefore negligible atmospheric pressure means no density gradient? It'd have to simply be a bigger balloon to go a lot higher, more displacement the greater the interaction between the balloon and the less dense atmosphere outside?

I imagine that if they had used hydrogen all they would have experienced is a faster rate of climb and maybe a couple of thousand feet more altitude, but I'm guessing.
 
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Judge said:
Hate to say it but am I the only one thinking whats the big deal ?

People skydive everyday, he just did it from higher up ..... Even I could do that so fail to see why this is even news worthy.
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Flare said:
Ah just the person I was looking for, have you head of these guys http://www.halojumpers.com/en.php They do jumps from 30,000ft. One day I will do a jump with them!

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The army do a lot of HALO jumps. :)

It's pretty damned awesome - and a fantastic way of getting troops to an area quickly, with minimal observation.

I've never done a HALO - max I've jumped from is nearly 24k feet, and deployment at 3.5k.

Lowest deployment was an illegal jump, and was about 800ft off the ground :o

Judge said:
Hate to say it but am I the only one thinking whats the big deal ?

People skydive everyday, he just did it from higher up ..... Even I could do that so fail to see why this is even news worthy.
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As someone with several hundred jumps, I can assure you, there is nothing ordinary about this sort of jump.
 
SourChipmunk said:
Questions 1 and 2 (as I tried to explain to a friend), I think of it like a fishing bobber in a lake with a lead weight on it. Take the bobber to the bottom and release it, it will float to the surface of the water and bob there, moving up and down with the motion of the water. Now, disconnect the lead weight and the weight will drop to the lake bottom, but the bobber will float up just a little higher on top of the water. There it will hang out until eaten by a grue. Using this example demonstrates why the balloon appeared to inflate more as it gained altitude -- the "weight" of the atmosphere crushed it at ground level just as water would crush a sealed container if it went deep enough.

My question is, if said bobber is filled with helium it might float just a little higher in the water or possibly even float slightly above it (depending on weight and internal volume). If they had used hydrogen instead of helium in the balloon -- although much more hazardous -- how much (if any) additional altitude could have been gained?
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I'm not surprised your friend didn't understand that! :p

Isn't it something along the lines of: Helium is lighter than air so it floats. Once the density of the air gets so low the helium is no longer lighter so it stops getting higher.
 
I await the day a sky elevator is built and somebody jumps off that from an even more ridiculous height.

Given that you wouldn't be in orbit per se, you could potentially be at something like 100miles up and still fall straight down?
 
Evilsod said:
I'm not surprised your friend didn't understand that! :p

Isn't it something along the lines of: Helium is lighter than air so it floats. Once the density of the air gets so low the helium is no longer lighter so it stops getting higher.
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Yes, he understood after I used that analogy. He couldn't understand why the altitude kept going up and down right before the jump.

I had another buddy tell me Felix was going to burn up immediately when entering the atmosphere just like meteors do. I had to convince him there was quite a bit of difference between 0-800 mph and 25,000-160,000 mph. :D
 
Pigeon_Killer said:
Hydrogen may have provided 8% more lift but it would've also provided 100% more flammability.
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VaderDSL said:
Well there is the explosiveness of it :) However I wonder how it would burn/explode at 128K feet with such a rarefied atmosphere, would it even combust fully with that little oxygen?
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I was just using hydrogen hypothetically. The thin material of the balloon, risk of static discharge at any altitude, and all the electronics involved would make that a really dumb idea. So the estimate is 8%, and would have brought the ceiling to almost 140,000 feet in this case. Yeah, not worth the risk for the extra altitude. I believe we're still in the stratosphere at this point, so hydrogen would still have buoyancy. But there is still "air" in the thermosphere. Would it be enough to support hydrogen with the additional weight attached? How much would volume make a difference?

All hypothetical, I know. :)
 
norm said:
Given that you wouldn't be in orbit per se, you could potentially be at something like 100miles up and still fall straight down?
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Our own moon is in freefall toward Earth right now, and the Earth is in freefall toward the Sun, and always has been. But centripetal force from the "ground speed" keeps it out where it is, just like how a spacecraft requires about 18,000-25,000 mph to remain aloft in orbit around Earth. Higher speed equals higher orbit.

As far as I know, we have one man-made object in space that is [relatively] stationary: a little satellite we have watching the Sun for us. It sits right in the zone between the Sun and the Earth called the "Lagrangian point", where the gravity is equally pulling toward the Earth and the Sun. One minor nudge in either direction though will send it to its doom. :)
 
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SourChipmunk said:
Our own moon is in freefall toward Earth right now, and the Earth is in freefall toward the Sun, and always has been. But centripetal force from the "ground speed" keeps it out where it is, just like how a spacecraft requires about 18,000-25,000 mph to remain aloft in orbit around Earth. Higher speed equals higher orbit.
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Yes I'm aware of that, but if you are familiar with the concept of a space elevator, it would essentially be a static tower extending in to space.

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If you were to climb it, your speed relative to the ground wouldn't change, making it an ideal platform to jump from.
 
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