A nuclear salt-water rocket (NSWR) is a theoretical type of nuclear thermal rocket which was designed by Robert Zubrin. In place of traditional chemical propellant, such as that in a chemical rocket, the rocket would be fueled by salts of plutonium or 20 percent enriched uranium. 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. Proposed design Chemical rockets use heat energy produced by a chemical reaction to heat the gas products. The hot products exit through a propulsion nozzle at a very high speed, creating thrust. In a nuclear thermal rocket (NTR), thrust is created by heating a fluid by using a nuclear fission reactor. The lower the molecular weight of the exhaust, hydrogen having the lowest possible, the more efficient the motor can be. However, in this engine the propellant can be any of many fluids having suitable properties as it does not participate in generating heat. In a NSWR the nuclear salt-water would be made to flow through a reaction chamber and out of an exhaust nozzle in such a way and at such speeds that critical mass will begin once the chamber is filled to a certain point; however, the peak neutron flux of the fission reaction would occur outside the vehicle. Advantages of the design There are several advantages relative to conventional NTR designs. As the peak neutron flux and fission reaction rates would occur outside the vehicle, these activities could be much more vigorous than they could be if it was necessary to house them in a vessel (which would have temperature limits due to materials constraints). Additionally, a contained reactor can only allow a small percentage of its fuel to undergo fission at any given time, otherwise it would overheat and melt down (or explode in a runaway fission chain reaction). The fission reaction in an NSWR is dynamic and because the reaction products are exhausted into space it doesn't have a limit on the proportion of fission fuel that reacts. In many ways NSWRs combine the advantages of fission reactors and fission bombs. Because they can harness the power of