Re: Interstellar Propulsion idea using an Asteroid and a few comets!

From: Rob Dekker (rob_at_verific.com)
Date: 09/01/04 

Date: Wed, 01 Sep 2004 09:14:56 GMT

"Grimble Gromble" <grimble.gromble@virgin.net> wrote in message
news:PtkYc.342$017.259@newsfe3-gui.ntli.net...
> "Rob Dekker" <rob@verific.com> wrote in message
> news:A2iYc.12930$qp6.3387@newssvr27.news.prodigy.com...
> > It's alright. Dont worry.
> > Consider the extremes : What if the spacecraft does not isolate at all?
> > In that case, it would be a 'black-body', radiating at a balmy 25C (or
> > whatever you want the interior temperature of the ship to be).
> ...
> It's the temperature (and area) of the external surface that determines
how
> much black body radiation is emitted. The Stefan-Boltzmann law says how
> much: E = s * T^4 where s = 5.6696 * 10^-8 Wm^-2k^-4.
>
> At 10k that would be about 0.6 mW per square metre. At 100K it climbs to
> about 6 Wm^-2.
> Grim
>

Thanks Grim ! Very useful !
So, at 25C (300K), we radiate about 500 W m^-2.
A spherical space ship of 3000m diameter thus radiates 14GW energy.

We probably do not need that much energy to keep the lights on in the
spacecraft, so it DOES make sense to have some isolation material.
I suggest a good layer of styrofoam instead of miles of rock.
Saves a lot of weight...

Rob

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