[bradleyland]

Ok, you should definitely look in to RTGs then:

http://en.m.wikipedia.org/wiki/Radioisotope_thermoelectric_g...

I'll reiterate that hazmat suits are essential when working around rocket propellant, because the oxidizers involved will cause any organic material to ignite on contact. Literally, a pair of cotton gloves would turn in to a ball of flames on contact. That is all that is needed to explain their presence.

The government would have no reason to hide the presence of a nuclear power device, so the power systems described as powered by solar cells + LiIon batteries is entirely plausible. Preferred, in fact, because you needn't address the concerns of radioactive material in a tightly confined space. Arguably, it makes the engineering easier (marginally).