Rotor Drones for Mars

by Dr Graham Mann

As in many terrestrial applications, there are good reasons to think that small, highly maneuvrable drones would be valuable to human explorers on Mars. They could be used for scouting difficult or dangerous terrain, aerial photography for EVA safety and maintenance inspection purposes, hoisting antenna wires, fast location of small science targets and rapidly transporting small tools, instruments, circuit boards or regolith samples. In 2014 MSA field trials of Mars astronaut-assistance robots, a small Phantom quadrotor performed as well or better than the ground robots in many tasks.

Very low atmospheric densities and temperatures as well as windblown fine dust make flight in the Martian atmosphere a severe challenge for rotorcraft. To provide sufficient lift, even allowing for one third the gravity of Earth, rotors need to be larger and turn much faster than their terrestrial counterparts. That puts a lot of stress on the rotors. Combined with poor battery efficiency at low temperatures, it could impose serious limits on the endurance of such a machine. Fine abrasive dust particles would also spell trouble for exposed bearings, sensors and cameras.

Still, Aubrey Cason, David Parlevliet and I have been studying the problem at Murdoch University in Perth. Our preliminary tests in a low-pressure chamber have suggested that with the right rotor design, those problems might be overcome. We'll describe those results in the forthcoming International Astronautical Congress in September. Although current NASA Mars helicopters favour single-rotor designs, we have concluded that for small (< 5kg) machines, four rotors may be preferable and have commenced building our own prototype. And since in a small vacuum chamber there’s limited freedom to move, we intend to drop a 4kg test vehicle from a balloon at 120,000 feet, where atmospheric conditions approximate those at Mars, and then record performance data on-board during programmed manoeuvres during the descent. That is, we will if we can raise the funds for this last part!