I am ashamed to say that my knowledge of aerospace is limited to the realms of fiction, but I was particularly intrigued to read about NASA's Ulysses craft. Whilst its mission was interesting (to study the sun) its the length of service and the reason its mission has ended captured my interest. NASA has now ended the vehicles mission after seventeen years as its power system has now run out. Considering my phone runs flat in two days and my Frog runs for little more than 10 minutes, what the hell was powering this thing?
Like something out of Dr Brown's car, the energy for the Ulysses came from a radioisotope thermoelectric generator. This cell generates power using thermocouples heated by radioactive fuel. The radioisotope decays and gives off heat, which the thermocouple converts to electricity. The isotopes used allow for an extended cell life, hence the Ulysses lasting 17 years.
Where things get a bit scary is that isotope thermoelectric generators aren't confined to what we send out into space (or what falls back to Earth). The Soviets were big fans of them for beacons and lighthouses, and concerns remain as many have been just left, their status unknown.
