Robert Zubrin is best known for his advocacy of the manned exploration of Mars.

Zubrin also had a design for interplanetary propulsion called the Nuclear Salt Water Rocket.

A nuclear salt-water rocket (NSWR) is a theoretical type of nuclear thermal rocket. A conservative design for the rocket would be fueled by salts of 20 percent enriched uranium or plutonium. The solution would be contained in a bundle of pipes coated in boron carbide (for its properties of neutron absorption). Through a combination of the coating and space between the pipes, the contents would not reach critical mass until the solution is pumped into a reaction chamber, thus reaching a critical mass, and being expelled through a nozzle to generate thrust.

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