"Robert J. Bradbury" wrote:
>
> It looks like India may be getting into the space development
> business. They've designed a reusable space plane (the Avatar)
> that they claim will significantly lower launch costs for 1 ton
> satellites (much bigger than what we need to bring back an asteroid).
>
> URL: http://www.spacedaily.com/news/india-01i.html
>
> The key trick is to gather and liquefy the oxygen in the air
> rather than carrying it up from the surface. They say the idea is
> based on a Rand report published in 1987.
>
> Anyone have any comments on why this idea hasn't been pursued
> more seriously in the U.S. or Russia? It would seem to me
> the tricks here require relatively lightweight machinery
> for performing the liquefication and separation.
The air handling equipment is fairly massive and requires very very
delicate heat exchangers- the liquid hydrogen is passed through millions
of stainless steel tubes with wall thickness in the single micron
range. Dana Andrews gave a presentation at Space Access this April-
http://www.andrews-space.com/en/news/publications.html
It has been described by some viewers as a "single stage to NASA
funding" design- tech candy which pushes the threat of cheap access to
space decades into the future.
I have several objections to air liquefaction systems-
* the system is massive and startlingly complex, thus expensive and
unreliable
* the oxygen it produces has substantial argon and nitrogen
contamination, reducing performance
* bulk LOX at $0.05/lb is the second cheapest liquid after water
* the fuel _must_ be hydrogen, increasing vehicle bulk and drag
* the system must have airbreathing engines which *also* must be
hauled to orbit- or else the system is no better than a simple
two-stage rocket. Two stage to orbit is easy- why bother with
making LOX?
This all boils down to an impractical, expensive, unreliable, overweight
system which is extremely unlikely to result in a useful vehicle. It
smells like son of X33 to me.
-- Doug Jones, Rocket Plumber (Speaking for myself only)
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