Work on such a drive is underway.
Rocket-propelled rockets would be twice as efficient than currently used chemical rockets. However, it is not enough that the construction of sufficiently small reactors that would power the rockets is demanding, but using them would involve considerable risk for obvious reasons. Despite this NASA believes that this risk may be necessary.
"You can reach Mars using a chemical propulsion system, but it will be very difficult. A journey further than to the Moon is better accomplished using nuclear propulsion. ", said Bill Emrich, an expert in the field of nuclear propulsion – one of the members of the research team that is implementing the NASA project named George C. Marshall at the Space Flight Center NTREES (Nuclear Thermal Rocket Element Environmental Simulator).
NTREES allows engineers and scientists to perform realistic, non-nuclear prototype testing of nuclear engine components. Instead of conducting nuclear reactions, researchers use powerful electrical current to heat the elements of the propulsion fuel system.
Such tests are very important not only because they are incomparably safer than ground-based tests using real nuclear propulsion, but also because they allow the development of ways to cope with the gigantic heat generated by nuclear propulsion, and thus – to create the propulsion that will be able to survive this heat. While nuclear reactors used on the Earth's surface heat up to over 315 degrees Celsius, rocket propulsion reactors are expected to reach temperatures of at least 2000 degrees Celsius.
NTREES project simulator. Source: NASA
It is worth mentioning that even if over time a rocket is equipped with a nuclear propulsion, such a drive would not be used during starts. That would be too risky (and nobody wants another Chernobyl disaster). Therefore, chemical propulsion would carry rockets into orbit, and nuclear propulsion would be used already in space itself. There, nuclear engines can be extremely useful.
"Many space exploration problems require continuous availability of high density power, and there is a class of problems for which nuclear power is the preferred, if not the only, solution.", said Rex Geveden, a former NASA administrator, in August. Current NASA administrator, Joe Bridenstine, said that nuclear-powered rockets can be "Breakthrough" and "an amazing opportunity that the United States should seize".
NTREES project a few years after its creation, it was included in a larger program that aims to see how a nuclear engine can be integrated with a new generation NASA rocket – SLS (Space Launch System). In addition, for nuclear propulsion to finally become a reality, in 2017 the agency awarded BWX Technologies a three-year contract worth $ 19 million and the goal of building such a propulsion that uses nuclear fission. The implementation of NASA's nuclear drive should be accelerated by a $ 125 million cash injection that the agency received from the US Congress this year.
Before NASA launches a nuclear-powered rocket, it must develop safety protocols related to its use, as requested by the White House. Once these arise, the first nuclear engine flight will take place in 2024, as currently planned. Although eventually rockets equipped with such an engine are to fly to Mars and next, they will probably fly to the moon first – after all, they must first be tested in space.