A short hop to Mars

A Mars rover that could hop around the planet’s surface harvesting atmospheric gas for propulsion has been awarded funding by NASA.

The Mars Gas Hopper, designed by Robert Zubrin of Pioneer Astronautics, will use an electric pump to capture fuel in the form of carbon dioxide from the Martian atmosphere. Rather than taking months to move a few kilometres like current rover designs, the gas hopper would be able to fly distances of up to 100km from site to site to carry out research.

A demonstration version of the technology has shown that the unit can fly 100m and descend under control. ‘The gas hopper will totally outclass a surface rover,’ said Zubrin. ‘The Martian atmosphere is 95 per cent carbon dioxide so refuelling will be easy. It will allow access to areas where vehicles cannot go.’

According to Zubrin, the spacecraft’s pellet-bed rocket system (PBRS) could also maintain the International Space Station’s orbit by making use of waste CO2 from the life-support system.

Once collected, atmospheric CO2 is stored in liquid form at a pressure of about 10 bar. When the vehicle needs to move, a pellet bed made from beryllium or boron is heated to 1,000 degrees Centigrade and the CO2 is warmed to 300 degrees. This raises the pressure inside the tank to 65 bar. A valve is then opened to allow the liquid CO2 to pass through the pellet bed, where it is converted into a gas for propulsion.

The hot gas is then pumped into a series of thrusters beneath the spacecraft to produce vertical takeoff. Once the vehicle is airborne, the gas flow is directed into a rear-pointing thruster to generate forward flight. The direction of the gas is used to change the vehicle’s direction and to control its rate of descent during landing.

Electricity to collect the CO2 and heat the pellets is provided by solar panels mounted on the gas hopper’s wings.

The project is being funded under NASA’s Small Business Research and Development contract awards. A simple version of the spacecraft would weigh around 50kg — just a third of the weight of current rovers.