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Thread: Pratical method of exiting earth's atmosphere?

  1. #1 Pratical method of exiting earth's atmosphere? 
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    Dec 2013
    Hey people! My name's Jeremy! I want to first make it clear that I have no understanding of science or smart people things whatsoever (I almost failed geometry and never took physics). So don't rag on me too much if what I ask here has already been thought up or is just plain stupid.

    So the other day I was watching some YouTube videos on space travel and things of that nature, (I'm a huge Sci Fi fan) and the little wheels in my head started turn over the next few days and this idea popped into my head.

    As I understand one of the chief problems with current space travel is that it is really expensive (understatement). I think one of the figures I saw was something like 10,000 U.S. dollars per pound to put something into space. One article I read said that orbital elevators would greatly decrease this cost but are still with current technology impossible to make. However what about something like an semi-orbital lift?

    In my head the design would work something like this: Hydrogen in much lighter than air and eventually escapes earths gravity. This is also true for helium but hydrogen is much easier to create and supply. I know that recently hydrogen airships have been designed and are being researched for better and more efficient cargo transportation. Now from what I've researched online the higher you go the less energy it takes to escape earth's gravitational pull.

    My question is this: Is it possible and practical to create a giant floating lift using hydrogen, that can take rocket ships to the border of our atmosphere reducing the cost in launching materials into space?

    PLEASE FEEL FREE TO CORRECT ME! I want to learn and I'm very curious about this idea.

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  3. #2  
    Forum Cosmic Wizard
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    Quote Originally Posted by spacefan87 View Post
    My question is this: Is it possible and practical to create a giant floating lift using hydrogen, that can take rocket ships to the border of our atmosphere reducing the cost in launching materials into space?
    Yes. However the problem isn't "getting into space." That's the easy part, some aircraft/rocket hybrids can do it. The hard part is then accelerating to orbital speed. That's what takes all the acceleration (and fuel.)

    Historically this method was used for launching sounding rockets. It was cheaper than the additional lower stage it would require. One problem is that the operator has no control over where the balloon goes after it is released, and thus issues like dropped stages become a lot more problematic. For this reason most "rockoon" launches were done at sea.

    To launch something orbital you'd have to lift hundreds of thousands of pounds, and the cost of the ballon/lifting gas might be more expensive than the additional lower stage.

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  4. #3  
    Universal Mind John Galt's Avatar
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    Jul 2005
    Hi spacefan, welcome to the forum. I have nothing to add to billvon's technical comments. I just wanted to say that, despite your lack of science education, you came up with a potentially really good idea. Feel pleased about that. Sure, it turns out to be impractical - at least at present - but so do most potentially good ideas people have. Keep imagining!
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  5. #4  
    Moderator Moderator Janus's Avatar
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    Jun 2007
    There are limits on how high a balloon can get. Mainly because the higher you go, the thinner the air gets, and so to maintain buoyancy, the balloon has to expand to keep the inside and outside pressure the same. You can ony allow for so much expansion of the balloon. The record for balloon altitude is ~40 km.

    Now while it is true that gravity does get weaker with height, we measure this height from the center of the Earth. The surface of the Earth is 6378 km above the center, and another 40 km doesn't make much difference. At that height, gravity has only dropped by about 1%.

    Then there is the problem of getting the airship back to Earth, it will have to vent some of its hydrogen so that it can sink back to the ground to be re-used, so you will lose some hydrogen in the bargain. Rockets burn hydrogen for fuel. So that lost hydrogen will have to be subtracted from any fuel savings made from launching from 40 km. All in all, it really doesn't seem worth the effort.
    "Men are apt to mistake the strength of their feelings for the strength of their argument.
    The heated mind resents the chill touch & relentless scrutiny of logic"-W.E. Gladstone

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