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.
Royal Society Publishing - A Mars hopping vehicle propelled by a radioisotope thermal rocket: thermofluid design and materials selection
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.
13 pages of supplemental information.
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.
Bobby Cohanim, Draper’s technical lead for the hopper prototype, and Eph Lanford, a Draper Fellow, check fittings and connections as part of pre-flight operations. (photo credit: John Earle)
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.
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