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If I fill a spacesuit to its maximum volume with hydrogen while wearing it (who cares about the breathing part anyway) and jump from space (let's say, from 100km above sea level, a.k.a. Karman Line), could I survive the fall? Or the hydrogen buoyancy/body weight ratio would be so little that it would make no difference for the speed of the fall?

Bonus questions: would I blow up when hitting the surface? Should I use helium instead?

Please help, I wanna jump from space!

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    $\begingroup$ What do you think? How about if instead of jumping from a height of 100 km you consider the simpler problem of jumping with a hydrogen-filled spacesuit from a height of only 100 feet off a building onto the hard pavement below? $\endgroup$ – user93237 Jul 24 '18 at 3:21
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    $\begingroup$ What happens unprotected spaceships that enter the atmosphere ? $\endgroup$ – StephenG Jul 24 '18 at 4:14
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    $\begingroup$ @SamuelWeir What if the OP takes your advice, jumps off a building, and dies on the hard pavement below? Or else gets a permanent disability and tracks where you live? Smooth... $\endgroup$ – safesphere Jul 24 '18 at 4:29
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    $\begingroup$ @safesphere - Good point. If you ever drop out of physics, you may have the makings of a good lawyer. The tech industry needs more lawyers to write more warning labels like these: itworld.com/article/2826901/security/… $\endgroup$ – user93237 Jul 24 '18 at 5:12
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    $\begingroup$ @safesphere - ....Oh, and also I'm counting on him suffocating himself in his hydrogen-filled spacesuit before he makes it to walking up beyond the 2nd floor to the top of the building anyway. $\endgroup$ – user93237 Jul 24 '18 at 5:17
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The hydrogen would have an infinitesimal effect. It is highly unlikely that any scientific instrument could detect it's effect.

The buoyancy of hydrogen comes from the mass of the air it displaces. So right away, we realize there's a problem. If you're in 1/1000th of an atmosphere, even a full spacesuit of hydrogen is denser than the air. It doesn't provide any buoyancy at all!

So let's give you the benefit of the doubt. Let's fill the space with pure vacuum instead. You said breathing was optional, right? Now consider your own mass. Perhaps it's around 100kg. That means your vacuum bubble needs to displace around 100kg of air. The density of air is roughly 1.225kg/m^3, meaning you'd need about 122 cubic meters of air. That's not the volume of a space suit. That's more like the volume of a room.

At a mere 10km of altitude, the atmospheric pressure is about a third of that, so you need around 450 cubic meters of air. At a mere 50km, atmospheric density is 0.002 kg/m^3, so you would need 50,000 cubic meters of air! That's getting into the volume of a supertanker!

Far better to use more typical means of arresting your fall, like parachutes.

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