MOBILE NUCLEAR FISSION ENGINES
FOR MARS SURFACE VEHICLES AND/OR AIRCRAFT
Robert D. Woolley
When humans go to Mars, we should take vehicles such as “rovers” or helicopters, powered by compact nuclear fission reactor engines. This would provide portable “muscle power” for digging, e.g., in search of life or water, and for long distance mobility to explore the entire planet without having to periodically return to a fixed ground base. Reactor power would provide continuous life support, including heat to survive the frigid Martian nights.
Technical requirements for Martian mobile nuclear fission engines are discussed. The fundamental design issue is minimizing mass while providing adequate power conversion and radiation shielding.
Nuclear fission reactors have supplied more than 20% of earth’s electricity over the last several years, using either natural uranium fuel or uranium slightly enriched in the fissionable isotope U235. However, a compact reactor must use either Highly Enriched Uranium (HEU) or plutonium fuel in its core. A plutonium core would be smaller than a HEU core but would suffer from a smaller experience base. Compact nuclear fission reactors using HEU are ubiquitous in the submarines of several nations’ navies and are even used to power some aircraft carriers.
Substantial design, development and testing activity was pursued in the 1950s and 1960s to adapt mobile nuclear fission reactors to propel jet aircraft and nuclear thermal rockets. The aircraft and rocket applications are not in use today, in part due to radiological safety issues that could accompany a crash in a populated region. In contrast to plutonium, HEU fuel carries the safety advantage of having negligible radioactivity before it is inserted into a reactor and fissioned. If a Mars mission with an unoperated HEU-fueled reactor as cargo were to crash while being launched from earth, radiological safety issues would be insignificant.