A conventional rocket engine uses the phenomenon of exhaust gases that originate from the combustion of fuel. Interesting The application of nuclear technology is a rocket engine with a reactor. In such a case, in the engine, the propulsion medium is the hydrogen flowing through the reactor, heating to a very high temperature. Then it enters the nozzle where, as in a normal engine, it expands and flies out in the opposite direction to the direction of flight.
In the 60s, the NERVA research program was carried out, the goal of which was to construct a nuclear rocket engine. A number of prototypes and experimentally confirmed that it is possible to make a nuclear engine obtained a higher specific impulse than a chemical engine. The largest of the prototypes, NERVA XE PRIME, was ignited a total of 28 times, and with an output of over 1000 MW, it was able to work for almost half an hour. In comparison, the Merlin 1D vacuum engine from SpaceX works for approx. 5 minutes.
On some sites on the Internet you can read that NERVA was canceled due to the risk of contamination in the event of a rocket explosion at takeoff. This is not true. Nuclear reactors have been taken out more than once in space satellites. Fresh uranium fuel does not contain decay products, which are the most radioactive. The real reason for shutting down the program was the rising costs of the Vietnam War, which forced the US to reduce its Research. For this reason, Apollo 18, 19, 20, supersonic passenger flights and a number of other scientific projects were canceled.
NERVA video [1].
