On Mars, a 6-meter diameter ball could be used for descent (replacing the parachute), landing (replacing the airbag), and mobility (wind-driven on surface).

In a lab that appears to mix three parts of serious R&D to one part of Santa's festive workshop, Jones and his colleagues are surrounded by shiny Mylar balloons of various sizes, pink and yellow beach balls, heavy-duty nylon tumbleweed ball prototypes, tall tanks of compressed gas and worktables full of mechanical and electronic devices. The team, which includes senior engineer Sam Kim and design engineer Jay Wu is now preparing for desert tests later this month that will incorporate a radar into the ball's center to test the prototype's ability to find underground water. Such instrumentation could eventually be used to search for possible water hidden beneath Mars' surface.

The ball is weighted so that it has a preferred axis of rotation. It tends to roll with the heaviest part down, so two weights opposite each other send the ball along a straight path. The upcoming tests will also try out a center-of-mass control device that Connors conceived of which would allow the ball to be steered by pumping contained fluid to the left, right or center of the tire, which will be slightly oblong.

"Again, this is experimental, so we're trying different things," said Jones. "But I'm pretty confident it will work."

"Tumbleweed" is a large, beachball-like device that holds a central payload by means of a series of tension cords.

"With a 20 kilogram ball and 20 kilogram payload, the 6-meter diameter tumbleweed ball is light enough that it could be added on to another lander and deployed from the ground, or it could be in its own delivery vehicle," said Jones. The large, lightweight ball could possibly also serve as its own parachute and landing airbag, he said, able to withstand the bounce following a 30-meter per second terminal velocity descent at Mars. The ball itself shares the same heritage as the airbag used for Pathfinder and that which will be used for the Mars Exploration Rover.

Upcoming Tests

Other work being planned for coming months include desert drop tests with a prototype tumbleweed ball made of super rugged Vectran, the same material used for the Mars Pathfinder's airbag landing system. In the coming year, Jones hopes to arrange for long-range testing of hundreds or thousands of kilometers in the harsh, challenging, Marslike environment of the Arctic or Antarctic.