Nuclear decay-driven machines could gather gases from the atmosphere of Mars, giving future robotic missions leaps of a kilometer once per week The Opportunity rover, which has been on the Martian surface for nearly seven years, passed the 25-kilometer mark this week. A new Mars hopper could cover 50 kilometers per year or 350 kilometers over seven years.
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. A systematic study of the thermodynamics, heat transfer and selection of core materials for a Mars hopper was undertaken. The aim was to advance the motor design and assess technical risks and feasibility. Analytical and numerical motor models were developed; the former to generate thermodynamic performance limits, an ideal hop distance and plot a materials selection chart using simple explicit relations. The numerical model assessed the effect of core configuration and geometry. A hop coefficient Chop is shown to characterize the effect of core geometry independently of core material and temperature. The target hop distance of 1 km is shown to be robust. A moderate advantage to pebble-bed cores over a core consisting of straight channels was suggested. High-performance engineering ceramics such as boron carbide offer the longest hop providing the core temperature can be increased significantly above 1200 K.
2. NASA could explore more of Mars in a few days than it has over the past six years through using a vehicle under development at Draper Laboratory that could land on the Martian surface and then propulsively “hop” around to various areas of interest.
Two hoppers could likely travel a total of 25 miles on the Martian surface with five hops in a matter of hours or a few days. NASA’s Spirit and Opportunity have traveled a total of just under 20 miles since landing on Mars in January 2004.
Draper is developing a planetary hopper test bed with MIT students and staff to mature operations, algorithms, and experience. The Terrestrial Autonomous Lunar Reduced gravIty System (TALARIS) testbed is designed to simulate a planetary gravity environment using a ducted fan propulsion system while an independent cold-gas control system performs the hop in the simulated environment. Draper is the lead systems engineer and developer of the guidance, navigation and control (GNC&C) and avionics systems; MIT is building the test bed structure and propulsion system.