RE: starship-design: Re: Hull Materials

["L. Parker" <lparker@cacaphony.net>]

On Thursday, November 13, 1997 5:26 AM, Timothy van der Linden 
[SMTP:TLG.van.der.Linden@tip.nl] wrote:
> Hi Kelly,
>
> >>> High melting points may indeed be handy if we're going much higher
> >>> than
> >>> 0.3c, then the temperatures can be similar to those of the Shuttle's
> >>> shield when entering orbit.
> >
> >Does this mean my litium-6 sail and fuel plug will have a heating
> >problem?
> > Cruise speed was supposed to be over .4 c.
>
> Yes, I think it will have a problem.
>
> The number (6000Watt/m^2) I mentioned assumes that all radiation is
> transferred into heat. To do that, a certain amount of stopping power is
> necessary. That is, the shield should be thick enough.
> It seems that lower energy protons will loose their energy rather fast,
> actually faster than one would realize: A 10MeV proton will come to a
> complete "standstill" after only 60 micrometers of aluminium.
> My table/formula is only valid upto 10MeV protons, so I can't be sure
> about
> what happens when one encounters a 80MeV proton (the energy of a proton
> at
> 0.4c), but I assume it will not lessen the problem.
>
> Timothy
>

I don't remember the specifics on Kelly's sail, but most proposals for 
solar/laser/microwave sails are only 100 micrometers thick at best. I still 
think most protons, etc. will just blow right through the sail without even 
impacting much of anything, especially if it isn't a solid sail, and there 
is no reason why it should be solid.

Lee