Interesting trade offs and compromises that deep spacecraft engineers have
to anticipate and deal with missions lasting years, even decades.
Thanks,
K
On Tue, Mar 2, 2021 at 3:44 PM Henry Spencer <hspencer@xxxxxxxxxxxxx> wrote:
On Mon, 1 Mar 2021, roxanna Mason wrote:
it's not an accident that even Pu-238 RTGs tend
to be located away from electronics, in fact preferably out on booms --
Right and that's what the booms on Voyagers spacecraft are for. So isn't
that a good solution for rad. damage, just put the RTG on a boom plus
put a shield between the source and spacecraft which wouldn't be that
large a cross section considering the distance and source area.
If you're thinking of the radiation damage to the thermoelectric
converters that I mentioned, alas, no -- they're part of the RTG, they
*have* to be snuggled up to the heat source to work at all. (There are
some tricks that could be played to run them a bit cooler during cruise
periods, reducing the damage the radiation does while power demands are
lower and converter efficiency less of a concern; this was proposed,
although I believe not implemented, for Cassini.)
And unfortunately, no, it's not practical to put useful shielding between
a boom-mounted RTG and the rest of the spacecraft, because stopping gamma
rays and neutrons is hard -- they are very penetrating, you need *thick*
(and therefore heavy) shielding to stop even a sizable fraction of them.
If you've got mass to spend on radiation reduction, probably the most
effective way to use it is to make the booms longer, so the spacecraft
intercepts less of the RTG radiation output.
Henry