An arxiv paper looks at possible engines for a manned Mars mission that are currently being tested or with flight proven capabilities. One propulsion system that was examined that is unproven is the “Pure Electro-Magnetic Thrust” (PEMT), presented in 2002 by Carlo Rubbia. In his proposal, the engine produces thrust as a Solar Sail, but uses a nuclear reactor as the power source.
The propulsion systems considered are:
• Common Extensible Cryogenic Engine (CECE) - a classical chemical propulsion;
• Nuclear Engine for Rocket Vehicle Application (NERVA) II - a nuclear thermal propulsion;
• RIT-XT, a modern electric propulsion;
• Pure Electro-Magnetic Thrust (PEMT) - a concept propulsion.
Cryogenic chemical systems have higher thrust then regular chemical rockets. Cryogenical chemical systems have Isp of about 465 seconds.
Nuclear thermal engines have been developed since the 1940s. A single propellant, usually hydrogen, is heated by the nuclear core and is expelled through a nozzle while expanding. The core, usually an uranium derivative (like dioxide or carbide) or plutonium, releases heat due to the nuclear reaction, providing energy to the gas expansion, and resulting in an Isp approximately the double of the chemical engines. The heat released is limited by the melting point of the materials.
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