This diagram shows how the Copernicus spacecraft could be adapted to different missions and travel times

Engineers have proposed using seven launches (shown above) to carry cargo and crew to Mars in 2033

However, the project, which was a collaboration between Nasa and the US Atomic Energy Comission, was officially ended in 1973.

During that time, engineers produced several prototypes, the most advanced of which was known as a Pewee engine. None of the engines were ever used for flight.

Proposals to use nuclear powered rockets were also discussed in a presentation last year by Dr Michael Houts, nuclear research manager at Nasa's Marshall Space Flight Centre.

He described the nuclear propulsion was a 'game changing technology for space exploration'.

He said they hoped to prove the viability and affordability of the technology within the next three years.

Dr Houts said: 'Nuclear thermal propulsion is a fundamentally new capability - the energy comes from fission not chemical reactions.

'Advanced nuclear propulsion systems could have extremely high performance and unique capabilities.'