Re: starship-design: Re: Starship design

[KellySt@aol.com]

In a message dated 9/30/97 12:54:37 AM, stevev@efn.org (Steve VanDevender)
wrote:

>KellySt@aol.com writes:
> > Glad you liked the site.  We were trying to inspire people.  ;)
> > 
> > We did actually consider something like your design called M.A.R.S.
> > (Microwave Augmented Rocket System).  In M.A.R.S. a microwave sail was
used,
> > and the microwaves focused back to drive a deceleration rocket.  I'm not
sure
> > where we finished with that, but it had two problems.  Forst the amount
of
> > energy causes tremendous waste heat problems.  Secound, the sail is so
> > efficent at producing forward thrust, its difficult to generate enough
> > reverse thrust to counteract it.  Can't remember if its proponent (Kevin
> > Houston) was ever sure it could slow down?
>
>As I recall there was a great deal of debate about this, mostly around
>the physically impossible idea of slowing down using beamed power from
>Earth without using reaction mass.  If you use some sort of reaction
>mass (and in a real sense, a retromirror is reaction mass -- it gains
>the forward momentum so the payload can lose its momentum) then you can
>slow down.

I'm not sure, but I think your right.  Thou for technical reasons a
retro-mirror system, is probably unworkable.


>I suspect that it may be more practical to exploit drag from the
>interstellar medium to decelerate down from high relativistic speeds,
>then use a fusion rocket or the like to do the final braking into the
>target system.  Then you need neither beamed power nor to carry extra
>reaction mass that increases power requirements during the boost phase
>of the trip.

I'm not sure, but I think we gave up on using interstellar media for drag?
 Probably their just isn't enough of it to be worth using.  Anyone remember?


>Of course, this isn't very helpful for the return trip unless the
>travelers can build a boost beam in their target system, but I believe
>that among the other advances needed for interstellar travel, we'll have
>to advance past the notion that explorers should always return from
>their trips.


?! This is an advance?  Throwing away a ship and crew to save fuel costs?

Kelly