Lockheed just gave this talk at Penn State (Score 4, Informative)

A man from Lockheed, whose nuclear space program is located in King of Prussia, PA, just gave a talk on this at Penn State to the Nuclear Engineering students. To clarify what is actually up there, there is 1 US RTG core, and about 35 Russian RTG cores (that we know of). RTG is a Radioisotope Thermoelectric Generator, they provide power for a very long time many times outlasting the life of the satellite. The reason we use these and not just solar panels has to do with harsh environments, and solar energy exponentially decays the further from the sun you get, once you get past Mars it is effectively zero. All the cores total about 1 Metric ton of highly enriched Uranium 235. The reason they are there is a simple one, when a malfunction happened on board a satellite the nuclear core was detached and shot off into a higher orbit. (on one occasion the satellite's guidance system was out and it actually sent the core crashing towards Earth. It landed somewhere in the jungle of South America, but the Soviets never found it, and refused our help.) So those cores are sitting up there in a high orbit and will come crashing down in about 600 years. As far as burning up in the atmosphere, well that was the methodology that NASA used to work with (now they are working with the idea that they should make the core indestructible and just retrieve it), however I am not sure and the man from Lockheed didn't give the impression it was. Personally I believe that's what we hope, but we just are not sure. Also, remember that we only have 1 core up there, the Soviets have 35 (at least) so who knows what to say about their cores.