Stanford’s Jet Propulsion Laboratory (JPL) in collaboration with MIT have conceived of a new means of asteroid exploration, modeled after a Hedgehog. The prototype robot does not need wheels, legs, or conventional means of locomotion. It instead relies on an internal series of flywheels that can be accelerated or decelerated to cause inertial reaction movements in order to get the robot where it needs to go.
Recent tests on the cube have involved its performance in a microgravity environment, which is similar to what it will encounter on its planned missions to asteroids, comets, and similar bodies.
Because the gravity on these objects is so small when in space, wheeled transport does not have sufficient traction, along with the constraint that the wheels must be facing downward in order to work.
The same problems apply to a design using legs, so the team behind the Hedgehog went with a cube-based design containing three “reaction wheels.” Because the cube is symmetrical, there is no right side up to maintain when landing on an asteroid, or comet. Again, due to the low gravity on its proposed missions, the internal reaction wheels will be able to generate enough torque on the Hedgehog to cause it to jump great distances, when needed.
It is easy to envision a scenario where the Hedgehog could land in a depression on the surface of a comet or asteroid, requiring it to launch itself to a more favorable position with sunlight exposure in order to power its solar panels.
Marco Pavone of Stanford commented on the progress of their design, “The general strategy is to make this ready for flight, at least in its most basic configuration, fairly soon, so that whenever a flight opportunity arises, we can raise our hands and say, ‘look, we have an option here with a secondary payload to dramatically increase your science with a minimal cost.’” With the modular design of the Hedgehog, it is a relatively simple matter to mix and match the desired instrumentation for a proposed mission.