[blach]

I find the power system constraints for the mission super interesting. The MMRTGs are pretty hefty (45 kg) and end up providing about 2.4 W/kg, without the batteries (which are sized independently) required to store their output. Also, just noticed it puts out ~2kW of thermal power in addition to the 110W of electrical power, hadn't seen a number on that previously.

[Rebelgecko]

I was surprised that they're only expecting 70W by the time the mission actually arrives at Titan. You'd only expect to lose ~1%/year due to decay. I wonder if they'll be mixing new and old plutonium due to availability concerns?

[hughes]

They may be reserving a large portion of the generated heat for thermal control. It's extremely cold on Titan.

[jacobush]

I guess, but it all (well, 99.999999% and more) gets converted to heat anyway when you use the electricity. So ... I don't understand.

[lmilcin]

I guess the reason might be it is pretty difficult to make efficient conversion from heat to electricity that would also be very reliable.

[velosol]

They also mentioned decay in the conversion process. I wonder if we have good data on the decay of the thermal-electric converters from missions like Voyager that have traveled through large portions of space or if they're being conservative?

[petschge]

Efficiencies between 5% and 10% are pretty typical for thermoelectric devices. So getting 110W out of 2kW decay heat is about what you would expect. The RTGs on board the Voyager spacecrafts initially produced 2.4kW thermal power of which 155W were available electrically. Note that each Voyager carried three of those RTGs.