To explore space, a propulsion system that is more durable and powerful than chemical fuel is needed. In addition, there is also a need to find energy sources for the colony that will be built. Therefore, nuclear energy sources are seen as a two-in-one solution for both of these problems.
Rolls Royce has shared the concept design of their mini nuclear reactor that will be used by the UK Space Agency. At this time it is still in the design stage with the most suitable fuel being sought. It needs to be Uranium based but needs to be durable enough to be used in space. The mini-reactor is of the same fusion type as the reactor developed by Rolls Royce for Royal Navy submarine use.
A program to build a mini-reactor for use in space missions was announced by the UK Space Agency in 2021. There is still no timeline for when it should be operational.
Last month NASA and DARPA announced they will test the DRACO nuclear rocket engine by 2027. If it goes well, this will pave the way for NASA to launch a mission to Mars before the end of the 2030 decade.