Half a croissant, on a plate, with a sign in front of it saying '50c'
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50km space station

very interesting place due to the relatively warm climate
 
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Hi !

Just another idea I would like to discuss:

If we look at the way the atmospheric pressure and temperature goes there is a pretty interesting area at about 50km height.

Air pressure is almost gone (less then 100Pa which is 1/1000 of the 100000Pa at sea level)

BUT the temperature recovers to something pretty close to Zero degree Celsius where an Eskimo will start to show perspiration.

This means if we build the head of a space tower or a space station exactly there you would have no real heating or isolation problems.

Compressing the outside air with a factor of 500 (giving high mountain air pressure) can be still achieved with standard equipment.

So you have a 'not so bad' temperature and relatively cheap air supply at this place.

Does anybody know why this interesting place is ignored for building a human habitat/station?

BTW if I remember right the sonic speed is mainly dependant from the Temperature, so at 50km it should be close to the normal one at sea leven (at a much lower pressure = resistiance when going to space from this spaceport).

I'm aware that if we don't build a space tower it would need a lot of fuel to stay at 50km due to the remaining air resistance at orbital speed (Mach 27 if I remember right)

But constructing a tower there would avoid the fuel problem and be a magnitude simpler from the material point. Plain Dyneema strings are able to hold 300-400km of their own weight, so there would be plenty of security margin for such a structure (a security factor of 6-8 is human ready as cable cars are not having a higher one either).

And balloons can go up to 30-40km, so the remaining gap would be amazingly small and energy friendly for lifting supply (you can even use a steel cable to pull up the rest, if there would not be the orbital speed in case it is not a tower)

Input is welcome

gutemine, Sep 09 2010

Floating Space Station http://www.jpaerospace.com/atohandout.pdf
[MechE, Sep 10 2010]

[link]






       At such a low pressure the temperature is irrelevant anyway.
ldischler, Sep 09 2010
  

       //Does anybody know why this interesting place is ignored for building a human habitat/station?//   

       Phobia of heights.
Jinbish, Sep 09 2010
  

       Perhaps there are too many spiders. Have you not read "Charlie and the great glass elevator"? Other nasty monsters up there too. Earth's thick atmosphere protects us. Don't give them a way in...
saedi, Sep 09 2010
  

       A better place would be Venus. There you can find an altitude with earth-like pressures and temperatures. Sure, the clouds are sulfuric acid, but you'll get used to that.
ldischler, Sep 09 2010
  

       The last thing space stations need is more heat, they have plenty of that. The challenge is to get rid of that heat because the sun generates a lot more radiant heat than you can get rid of without a medium to dissipate it to.
DIYMatt, Sep 09 2010
  

       People seem to ignore the difference between stiffness and tensile strength. Anything that makes nice string/thread/cloth is not going to work well as a structure, it's not stiff enough. The addition of a resin to produce composites makes it stiff enough, but the overall material is weaker for a given weight.   

       And given that we have yet to produce a structure 1km high, I think we're a long ways from being able to design one 50km high.   

       And yes, air resistance would be a major limiting factor in any sort of orbiting station at that height.   

       What you're really looking for is what JP Aerospace is in the process of baking. See link for details.
MechE, Sep 10 2010
  

       Well, a temperature slightly below 0 should give you a big enough temperature gradient to do the cooling and you still have remaining air outside to get some kind ov convection to get rid of it.   

       And this idea ist not really about how to build the tower (this idea is next - promised).   

       Air resistance goes with the square of velocity. The winds in that height are not that exciting. Jet streams are at a much lower place (between 10-20km if I remember right) where temperature decides to go up again after falling quite dramatically. Hence the air friction for the station is not so much of a pain if you are going for the tower approach and not for the orbiting approach.   

       I just pointed out that it could be a much healthier place. Off course you would have other problems then in 100 or 400 km height .   

       But if I understand your feedback right is that you don't think the trading of problems there is worth considering ?   

       And I fully understand the difference between stiffness and tensile strength.   

       But the inflatable space tower people found a neat way to convert these two, and they got their patent granted (which is fun reading, because I think they forgot something which would make their life much easier)   

       And regarding the point that mankind has not yet built a 1km high structure:   

       Well, you are wrong. On 1. August 1919 Mankind had already a train of kites flying successfull at 9740 m height. This is still the official world record. And yes this was a structure connected to the surface reaching out that far and built with 90 year old technology.   

       If they would have had a Dyneema string, they should have been able to almost double the number on a good jet streaming day.   

       If you add some balloons on top (to make the JP Aerospace fans happy) you can almost double the number once more, and then the spiders would have a lot of rope to climb.
gutemine, Sep 10 2010
  

       Ah, and did those kites stand up to:   

       An earthquake, a crossbreeze, a hurricane/cyclone/tornado, a bird strike, still air, etc?   

       It's not a standing structure if it requires outside impetus to survive.
MechE, Sep 10 2010
  

       //then the spiders would have a lot of rope to climb//   

       NASA needs a program to stoke the public's enthusiasm. Itsy Bitsy Spider to Space (IBSS) would be just the thing.
ldischler, Sep 10 2010
  

       A kite doesn't care for earthquakes. Trees also survive and they have lots of structure on top.   

       But you are right, so the real question is how to keep the weight DOWN and make it go UP. Which brings you back on how to bring paperplanes to space   

       But this idea here is about the best place for a station.   

       BTW it could also be the BOTTOM station of a space tether :-)   

       Anyway. Tomorrow is 9/11 anniversary, and I decided this will be the perfect day for discussing a new idea to build an ultra high structure!   

       PS: And the problem of NASA is that they are fixed on proven technology and old science fiction. Even when they try something 'new' like Space Elevator they instantly spoil the idea with High Tech like Nanotube Tethers, Laser beaming of energy for climbers,... and then they offer prizes for other people to solve their mess :-)
gutemine, Sep 10 2010
  

       Bottom of a space station tether will be experience something similar to oribtal velocity, exerting a significant wind drag on the station itself.
MechE, Sep 10 2010
  

       You are right, but the wind drag at <100Pa is not 'that' bad - and no insects on the windshield. It should be equivalent to 1/1000th of Mach 27 at ground = <30km/h equivalent of wind 'pressure'   

       I would build from bottom up anyway - because everything else is dreaming. But then the 50km would be a nice sunny place for the first stop which is all what this idea is about.   

       PS: If Felix Baumgartner succeeds with the Red Bull Stratos project we could even make a fortune with all the base jumpers queuing who want to save on the downward ticket.
gutemine, Sep 10 2010
  

       I forget which company, but someone's already selling tickets for that.
MechE, Sep 10 2010
  

       for parachuting from >30 km ?   

       Well, we could still push them out of the market by offering a 50% discount and a free coffee cup :-)
gutemine, Sep 10 2010
  

       Yup, one of the sub-orbital launch companies (not Scaled Composities/Virgin) is offering one way flights for the passengers. Launches to start in the next couple of years.
MechE, Sep 10 2010
  

       dead or alive ?
gutemine, Sep 10 2010
  

       // at sea leven //
Is that near Loch Leven?
//The challenge is to get rid of that heat because the sun generates a lot more radiant heat than you can get rid of without a medium to dissipate it to. //
Air-con, duh.
AbsintheWithoutLeave, Sep 10 2010
  

       I think I read somewhere that, although the atmosphere is technically warm at 50km, it still feels cold because there are so few particles floating around (or something like that).
DrWorm, Sep 10 2010
  
      
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