[AR] Re: Mars Rover Power source
- From: "John Stoffel" <john@xxxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Wed, 10 Mar 2021 17:00:58 -0500
"Henry" == Henry Spencer <hspencer@xxxxxxxxxxxxx> writes:
Henry> On Tue, 9 Mar 2021, John Stoffel wrote:
Since the Stirling cycle power systems have passed 14+ years of
continuous operation, and seem to give more power per kg of mass, why
wasn't this used on Perseverance? Or is it planned for any future
rovers? Or other orbital missions?
Henry> The big-budget "flagship" missions are severely averse to new
Henry> technology, where "new" means "anything that hasn't flown
Henry> before", no matter how long people have been testing it on the
Henry> ground. Better to have a mission that's half-crippled by
Henry> design, using old tech that everyone agrees is credible, than
Henry> to take the slightest chance that something new might
Henry> malfunction (and then *you* would get the blame).
It makes sense... to a degree.
Henry> For all his sins, one thing that Dan Goldin got right was the
Henry> need for an organized program of flight demonstrations of
Henry> important "new" technology, to establish once and for all that
Henry> it would work in space. After decades of sitting on the ground
Henry> waiting for a chance, ion propulsion suddenly became acceptable
Henry> for science missions when Deep Space 1 flew it. Alas,
Henry> political support for the Deep Space program didn't last.
It's a shame it doesn't work better. I'm actually not too sanguine
about Webb space telescope not having major problems.
Henry> (Even if it had, anything to do with RTGs is expensive, and
Henry> their Pu-238 fuel is in short supply, so doing a flight-demo
Henry> mission for Stirling RTGs would face unusual obstacles.)
I wonder if the switch to americium or some other radioisotope in
larger supply, even with less heat per/cm3 would make sense?
It would seem that having a bigger power budget would be a good thing
for any rover or orbiter, if only so you can push higher power
transmissions back to earth more easily.
Henry> Except in the far reaches of the outer solar system, orbiters
Henry> generally are better off with solar arrays, which produce
Henry> *much* more power per kilogram. RTGs make sense only when
Henry> there's some problem with solar power: inadequate sunlight due
Henry> to distance, long cold nights with no sunlight, or problems
Henry> with dust accumulation on solar arrays. (The big thing that's
Henry> missing from current Mars landers/rovers is an organized
Henry> attempt to test dust-removal technologies; removal by natural
Henry> winds is helpful but not entirely reliable.) But yes, if you
Henry> need isotope power, then *better* isotope power would
Henry> definitely be a good thing.
I wonder if some sort of stirling cycle for a lunar rover in the polar
regions would be a good first step. But it's an even more extreme
temp swing that mars, so heat management is going to be interesting no
matter what.
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