With a hopper you have time to make corrections after each jump, so it doesn't need to steer while it's in the air. Once we determined that semi-random mobility was OK, we knew a hopper was possible. The combustion chamber fires, the piston punches the ground, and the hopper leaps. Each hopping cycle is about 5 seconds. The hoppers have been tested in a variety of conditions, and they performed reliably against obstacles, mud, sand, and rough terrain, says Spletzer.
Several patents are pending on the invention.
It wasn't easy. Recalling his youthful experience launching tennis balls out of a tube using lighter fluid, Fischer first suggested that evaporated fuels might provide power needed for high hops. At one point the Sandia research team had set a goal of simply achieving atmospheric combustion in a small piston chamber. When we finally made it fall over, we were happy. Later the team tried maximizing the power of the piston, ultimately achieving hops higher than 30 feet.