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Path: utzoo!henry
From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: net.space
Subject: Re: Re: Debris from Upcomming ASAT Test
Message-ID: <6024@utzoo.UUCP>
Date: Fri, 4-Oct-85 15:49:55 EDT
Article-I.D.: utzoo.6024
Posted: Fri Oct  4 15:49:55 1985
Date-Received: Fri, 4-Oct-85 15:49:55 EDT
References: <385@aurora.UUCP> <15800003@uiucdcsp> <108@muscat.UUCP> <634@osu-eddie.UUCP>, <620@petrus.UUCP>
Organization: U of Toronto Zoology
Lines: 37

> The US has flown plenty of plutonium-239-fueled thermisotope generators...

Fussy but important point:  the isotope generators use plutonium 238, not
239.  238 is much harder to make, but is a fairly pure alpha emitter with a
relatively short half-life (years), which is exactly what is needed for
isotope power.  239, the fissionable isotope, has too long a half-life and
too mixed a radiation output to be useful for this.

> ...to date we have actually flown only one nuclear reactor
> in orbit. I believe this was on a Transit navigational satellite in the
> middle 60's.

It was SNAP-10A in the mid-60s, which was explicitly a reactor test with
no other mission.  For obvious reasons, it's in a fairly high orbit.
Some of the Transit satellites used isotope capsules, since solar cells
are too vulnerable to attack for the military's liking.

> 1. "Unburnt" plutonium or uranium is only weakly radioactive, and its alpha
> emissions are easily shielded (the Apollo astronauts handled the plutonium
> sources for ALSEP with their gloved hands). However, a reactor that has been
> running for a while becomes extremely hot because of accumulated fission
> products.

Uranium or plutonium-239 can be handled with bare hands, if you aren't
worried about toxicity.  If you check, I believe you'll find that the
Apollo crews used tongs for handling the plutonium-238 capsules, because
they are *thermally* very hot -- sort of obvious given that they are used
in thermal generators.

> ... shooting one of these [Soviet ocean-surveillance satellites] down
> with our ASAT would guarantee that its radioactive remains re-enter the
> atmosphere within a pretty short time...

A good point.  One wonders why this has not been brought up before.
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,linus,decvax}!utzoo!henry


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