[amsat-bb] Re: Since We Are Off Topic Somewhat....

Robert Bruninga bruninga at usna.edu
Fri Feb 15 06:18:09 PST 2008

> Is it not possible to engineer a craft with 
> a much lower re-entry speed thus reducing friction?

Yes.  The problem is slowing from 17,000 MPH to 0.

Remember, it took the entire billion gallons of fuel to
accellerate the shuttle from 0 to 17,000 MPH.  It takes just as
much energy to slow it from 17,000 MPH back to zero.  Rather
than taking along a second External fuel tank with a billion
gallons of fuel into orbit and a retro-rocket, just to slow
down, it is more cost effective to just let the air slow you
down.  You get all that "slow down" energy from the air, and
that generates heat.

So yes, you could retro fire a slow-down rocket above tha
atmosphere, slow to zero speed and then just simply fall like a
rock and keep cool all along the way.  But it takes an awful lot
of fuel...


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