On Mon, 8 Oct 2001, Bruce Moomaw wrote:
> It's what it has been from the start: some kind of thermionic nuclear
> generator converting the heat from Pu-238 into electrical energy. However,
> NASA would like to develop a new system more efficient at this conversion
> than the current RTGs, thereby reducing the amount of plutonium necessary by
> a factor of 2 or 3.
A conversation with Chris Chyba over a year ago, seemed to suggest to
me that there was only one remaining RTG in existence (perhaps a spare
from the Cassini mission). In order to do Europa & Pluto the development
of a new source was a *necessity*.
> Their first development attempt -- the "AMTEC" generator -- was a royal
> technological fiasco, so they're now trying to develop a Stirling generator.
I believe the development work was being handled by LANL or LLNL, so I
don't think you can blame the failure on NASA. After all there aren't
a lot of nuclear engineers working at NASA.
> [snip] but, as I say, it would use far less plutonium,
> which is good both from the safety point of view and from the viewpoint of
> how extremely costly it is to manufacture the stuff.
Why is it costly to manufacture? Or is it just the handling costs that
drive up the expense?
> Any generator that uses Pu-238 at all, of course, runs a safety risk from a
> launch accident. NASA insists that the risk, even in the event of a launch
> explosion or accidental reentry, is miniscule; but then NASA lies a lot.
Ah, making claims without citing "factual" data (shame shame).
It would appear that the RTGs were designed by the DOE, so you would
need to make an argument that the DOE is lying about their safety, *not* NASA.
Here is a page about the RTG architecture -- judge the safety for yourself.
http://spacepwr.jpl.nasa.gov/rtgs.htm
> Solar power now looks perfectly practical for Jupiter flybys, since solar
> arrays have gotten a lot lighter than they used to be -- but solar-cell
> damage from Jupiter's intense radiation belts is still a very serious
> problem for a Jupiter orbiter, and the weight problem is also very serious
> for a Europa orbiter.
They can get *much* lighter still, but they probably have to be assembled
in space due to the high g forces during Earth launches. The limits would
appear to be at least 3 orders of magnitude lower than current areal densities.
Robert
==
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