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Re: RE: starship-design: Deceleration scheme

In a message dated 7/31/97 7:53:39 AM, lparker@cacaphony.net (L. Parker)

>>Sigh, I'm beginning not to like the sail concept as much.  It is simple
>>and elegant, but between the deceleration problems, plus the difficulties
>>of such mega-structure operation, and the power beam generation problems,
>>I think the use of matter-antimatter and/or fusion ideas may be the
>>ultimate best way to go.
>The sail concept never has been a GREAT way to get there. It just offers 
>the advantages of simplicity and efficiency. It is however, SLOW. At 
>least it is if we are talking about relatively large manned missons. As 
>a method for propelling light Starwisp type probes, it can get them up 
>to relativistic velocities using only a few weeks worth of time from an 
>orbital power array.
>For manned missions we will need something that can provide much higher 
>thrust over longer periods of time. Since you just recently joined the 
>group you may have gotten the impression that one or more of us are proponent
>of sails. Actually, I don't think any of us expect them to be used for
manned missions
>although we do continue to explore the possibilities.
>There are too many things that can go wrong to depend upon a beam or fuel
>from Earth for manned missions. The only thing left that we KNOW has
>thrust is antimatter, which we are far from sure we can generate and store
in sufficient
>Lee Parker

One correction.  I am a advacate of a hybrid microwave acceleration sail/
fussion deceleration system (Fuel/Sail).   It offers fairly high speed (.42c
ish) and full two way flights.  For routine (?!) interstellar travel between
colonized starsystems a pure microwave sail design works, but by then would
be obsolete.

Given our curent understanding of physics, that about the best we can do.