COMPASS Conceptual Design Team has a funded NASA NIAC phase 1 study. They want to develop a hopper vehicle using a radioisotope thermal rocket engine, using in-situ propellant, to explore Neptune’s moon Triton. This moon is thought to be a captured Kuiper Belt object due to its retrograde orbit and surface. It has a very thin atmosphere. Because of the variety of terrain and a gravity of only 8% that of Earth, a rocket- powered vehicle, or “hopper,” is a desirable choice for exploration, capable of hemispheric traverses and atmospheric sampling during hops. To be capable of a robust program of exploration, the vehicle must be capable of refueling using available resources. Power will come from an isotope heat source, which will also be used to power the rocket. Trades of using ice collected on or below the surface versus collecting the very thin atmosphere using cryogenic pumping will be made to downselect the propellant for the isotope powered rocket. The COMPASS team will be used to develop the concept which will demonstrate both radioisotope thermal propulsion and in-situ refueling.
There previously were designs by others for a hopping rover on Mars. Nuclear power would be provided for decades and fuel would produced to enable a short rocket flight. The vehicle woul use fuel for a short flight of about 5-10 kilometers. The nuclear power would be used to generated fuel fromt the atmosphere.