Nuclear Propulsion
Written by Tega Jessa
You may have thought when watching a shuttle launch or hearing about the delays in a mission to Mars, “Why don’t those NASA guys just stick a nuclear reactor on the shuttle and call it a day?” We know the awesome energy and power nuclear technology can produce. However applying it to space flight is more complicated than most people know. So I’m going to tell you about the history of research on nuclear powered flight in America and the basic designs existing and why we haven’t made significant progress with nuclear propulsion.
NASA first researched a nuclear powered engine in the 1960s and the early 70s. The project for this research was called the NERV rocket. This project’s goal was to make a nuclear reactor powered propulsion system for a Saturn V rocket. However problems quickly arose from political pressure, environmental concerns, and design flaws. America was still in the throes of a nuclear arms race and cold war, so nuclear power was strongly lobbied against. Also, the environmental concerns about radioactive waste played a big part in killing the project. The final nail in the coffin was the effectiveness of the NERV rockets in comparison to conventional rockets already in use. The main problem was that the rockets were not able to efficiently convert the energy of the nuclear reactions. This made them only as or less powerful than rockets already used. The project eventually ended in 1972.
The next nuclear propulsion attempt by NASA started in 2003 with the Prometheus Project. This project uses a multipronged approach following the two main lines of research for nuclear powered rocket propulsion. The first approach is Nuclear Thermal Propulsion (NTP) and second Nuclear Electric Propulsion (NEP). While some progress is being made economics stresses are affecting the budget for the project further impeding any significant progress.
So how does each of the present concepts for nuclear propulsion work? The principals are simple but the execution can be complicated. NTP works on the same concept as a hydrogen rocket. The material that makes thrust is heated by a heat source. In this case it is a nuclear reactor. The sheer energy this system can produce when properly managed can exceed that of normal rocket systems.
Unfortunately this type of propulsion is highly inefficient as the temperatures needed to make it truly effective would actually melt any known material now used to make rockets. To prevent this, the engine would have to lose 40% of its efficiency. The other approach is Nuclear Electric Propulsion. This works on the concept of using electrical power to heat the rocket propellant. The main design concept now in use for this type of propulsion is the Radioisotope Thermoelectric Generator. The generator is powered by the decay of radioactive isotopes. The heat generated by the isotopes is captured by thermocouples which convert this heat to the electricity need to heat rocket propellants. This technology is currently being used by NASA deep space probes like Voyager and Cassini.
We have written many articles about nuclear propulsion for Universe Today. Here's an article about about NASA and the department of Energy working on a nuclear propulsion system.
Want more information on nuclear propulsion? Check out NASA's resource on nuclear reactors in space.
Finally, listen to an episode of Astronomy Cast, all about rockets. Episode 100: Rockets
Filed under: Astronomy
