A LITTLE robot in a lab in Arizona is preparing to take several giant leaps
for robotkind. If it reaches Mars in the next century, as its developers hope,
it will produce its own fuel and be able to fly, hop and hover over the surface
of the Red Planet.
Last week the robotic rover underwent its first tests in a laboratory at the
University of Arizona. Known as Lorpex, the locally refuelled planetary explorer
is being developed by a team headed by Max Marcozzi at the Space Engineering
Lorpex is based on the Sojourner rover that was exploring the Ares Vallis on
Mars in July. Lorpex will still use wheels most of the time, but has been fitted
with thrusters and fuel tanks for longer journeys.
The team is hoping that Lorpex will be picked by NASA for a Mars mission
because it will be only half the weight of rovers that must carry fuel from
To produce its fuel, Lorpex uses solid oxide electrolysis. It has a fuel cell
that incorporates a zirconium oxide cell membrane catalyst. The membrane is
heated to 900 °C using power generated by the robot’s solar panels. At this
temperature, carbon dioxide, which makes up 95 per cent of the Martian
atmosphere, splits into oxygen and carbon monoxide. The membrane separates the
gases, which are then siphoned off and stored. The fuel cell produces around 1
kilogram of fuel every 10 days.
When the gases are recombined in a combustion chamber and burned, enough
thrust is produced to fuel a 2-kilometre flight, or a short hop-and-hover
manoeuvre that will take the rover to a more interesting site.
A carbon monoxide/oxygen fuel does not have as high a specific impulse as
other rocket fuels, where the specific impulse is the ratio of thrust to the
flow rate of propellant through the engine. Nevertheless, the researchers
believe the value is high enough to power short flights by the 21-kilogram
During last week’s tests, Lorpex had to make do with helium in place of the
real rocket fuel gases in order to make the tests safer in the indoor
laboratory. “We didn’t want to poison our students,” says Marcozzi. The helium
allowed the researchers to check the gas flows through the robot without