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Path: utzoo!linus!decvax!decwrl!sun!amdahl!ems
From: ems@amdahl.UUCP (ems)
Newsgroups: net.space
Subject: Re: Getting stuff into Orbit (skipping stones)
Message-ID: <2441@amdahl.UUCP>
Date: Fri, 27-Dec-85 19:41:02 EST
Article-I.D.: amdahl.2441
Posted: Fri Dec 27 19:41:02 1985
Date-Received: Sat, 28-Dec-85 13:18:44 EST
References: <8512261825.AA16515@s1-b.arpa>
Organization: Circle C Shellfish Ranch, Shores-of-the-Pacific, Ca
Lines: 36

> There has been some discussion recently about how to get mass into
> stable Earth orbit, using some form of ground-based accelerator.
> 
> If we consider only one mass at a time, then of course it isn't possible.
> When the mass leaves the accelerator, it is in free fall, and so its
> trajectory must return to that point - which presumably is quite close
> to the ground and so well within the atmosphere.  Lagrange strikes again!
> 
> One could also consider a mass that had aerodynamic lift, but again the
> answer is the same: it will return to the point where ballistic motion
> began; and if that was deep enough in the atmosphere to provide some lift
> on the way out, it will surely introduce drag on the way back in.
>
> The only way is to give the body some more impulse once it is outside the
> atmosphere, by means of rockets, an orbiting grabber, or whatever.
> 
Would it be possible to 'skip on the surface'?  If one
re-enters on a rough tangent, cannot some form of 'aerobraking' be
used to modify the orbit?  I must admit that the physics of it is
well beyond me, but it seems intuitive that some combination of
airfoil interactions on the way out and back would result in an orbit
not impacting the ground.  After all, we only need to change the
orbit by about 100 miles out of 8000 ... (Then again, intuition and
physics are often at odds, anyone can see feathers fall slower :-)

BTW the discussion on two masses was marvelous, what happens if one
mass is sent up, but divides in two at apogee?  I know that this
could be used to keep one mass in orbit.  Is there a way to keep
both masses in orbit by having them blasted in different directions?
Can this be done with minimal delta V and fuel?  (Yes, this is an
invitation to the soap box...)

-- 
E. Michael Smith  ...!{hplabs,ihnp4,amd,nsc}!amdahl!ems

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