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RE: starship-design: Hull Materials

On Monday, November 10, 1997 10:37 AM, Antonio C T Rocha 
[SMTP:arocha@bsb.nutecnet.com.br] wrote:
> A few doubts regarding radiation shielding and fractional lightspeed.
>   Would there be any considerable effect from doppler-shifting of
>   impinging
> radiation - taking into consideration relativistic effects?.
>   Ditto for particles?

I don't think Doppler shift is the problem, it is total energy in the 
quanta rather than its frequency - a megajoule laser is more powerful than 
a milliwatt x-ray, period. This the problem with particulate matter though, 
a grain of sand impacting the ship at near c contains quite a bit of 
energy, we don't even want to think about hitting anything larger. As 
Timothy pointed out, dust alone is going to cause significant erosion and 
thermal gain, "streamlining" may begin to make sense again.

It should be possible to at least deflect charged particles with some sort 
of magnetic field, but a lot of these particles are going to either be 
neutral or simply to massive to deflect in time so the hull has to be 
capable of absorbing quite a bit of impact for long durations. This means 
high melting points, high thermal transmissivity or a least high 
emissivity, extremely hard and yet ductile enough to remain "tough for 
several years of use.

We almost need something as tough as the inside of a nuclear reactor for 
the hull! Another problem that Timothy started to get into is secondary 
radiation. We have to screen against alpha and beta particle radiation 
caused by gamma ray collision with our own shield. Probably need to 
consider a fuel tank forward design to keep as much of the mass in front of 
the crew as possible.

Which brings us to deceleration, NOW the shields need to be at the BACK of 
the ship, not the front...

>   Would that make the ships hull look "harder" to the rad than to itself 
>    due to
> mass increase?

Umm, that is a relativistic mass increase, from the frame of reference of 
the ship there is no mass increase, or is there? Timothy, you want to help 
on this?