Nuclear Energy for Space Travel

One of the Future ATP campers asked, "What’s the difference between nuclear power on a submarine and nuclear energy that Cassini uses?" In reality they are very different sources of power. The nuclear power on a submarine comes from a controlled fission reaction which allows you to control the power available and in essence the rate of fuel usage. Additionally a submarine generates MW's of power to propel and power the onboard systems. Cassini uses radioisotope thermal generators (RTGs) of 630 W. This means that the power is generated from the decay of a radioisotope. The material undergoes radioactive decay and generates heat which is then used to generate electricity. There are a number of good references available on both systems and the strengths of both to fulfill different missions.