Jumping robots with radioactive rockets could someday explore Mars

The craggy Martian terrain is daunting for wheeled probes, and Mars' distance from Earth makes refueling rovers impossible. English scientists are exploring the possibility of harnessing radioactive isotopes and Mars' abundant carbon dioxide to launch probes across the Martian landscape.

Researchers at the University of Leicester are investigating the possibility of using radioisotopes that could compress Martian CO2 into a liquid and heat it as a booster. In theory, these radioisotope-powered rockets could launch a 10-foot-long, 880-pound probe approximately 0.6 miles (1 kilometer) over Mars' terrain. This propulsion system would also benefit from longer usage, as it would be able to use CO2 to explore the planet over several years. Says the researchers in their findings published today at Proceedings of The Royal Society of A:

Rocket-propelled vehicles capable of travelling a kilometre or more in a ballistic ‘hop' with propellants acquired from the Martian atmosphere offer the potential for increased mobility and planetary science return compared with conventional rovers. In concept, a radioisotope heat source heats a core or ‘thermal capacitor', which in turn heats propellant exhausted through a rocket nozzle to provide thrust [...] Exploration of the surface of Mars has been driven by a diverse but interlinked range of scientific objectives as wide ranging as geology, climate, radiation environment, the search for indications of biological life and identification of in situ resources to support future manned or long-duration missions [...] The Martian atmosphere is composed mainly of CO2 [...] Given this in situ resource, several authors have identified the potential for a ballistic ‘hopping' vehicle using this CO2 as a propellant, proposing hop distances of 0.5–20 km.

The use of high-quality ceramics could propel the craft even further. Sadly, these radioisotope-powered probes won't be bounding around like Edgar Rice Burrough's Barsoomian Kangaroo Men — these hoppers would have to rest and recharge, says Leicester researcher Nigel Bannister (via Space):

Between flights, the vehicle will be re-heating the core, compressing carbon dioxide to fill the propellant tank and conducting science experiments [...] A week is a reasonable initial estimate for this turnaround, but in a final design the compression system could be designed so the refueling time is similar to the expected duration of science experiments.

You can watch a video simulation of the probe at Space.

[Photo of NASA's Phoenix Mars Lander, which is different from the UofL team's proposed vehicle, via Aviation News.]