This isn't your father's idea of a space rover. NASA's Chariot is the first prototype in a new line of lunar vehicles that could someday bulldoze roads, dig trenches, and drill for minerals on the moon. And it is already proving as nimble as it is powerful in earthbound testing.

Chariot, a two-tonne "truck" with a top speed of 20 kilometres per hour, has been tearing up the Lunar Yard, a test bed at the Johnson Space Center in Houston, Texas, since engineers there completed construction of the vehicle in September of 2007.

The Lunar Yard is a 2-acre expanse of small hills covered in a mix of sand and crushed granite designed to mimic the loose surface of the moon.

The current prototype has a detachable plough for turning over lunar soil, but future designs may incorporate a back hoe, or excavator, and a drill rig capable of boring into the lunar soil. "Building a lunar truck isn't so much 'rocket science' as it is applying what you know about earth-bound trucks," says Lucien Junkin, Chariot's lead engineer.

Mars lessons

Independent steering on each of its six pairs of wheels allows the vehicle to spin on the spot, zigzag up steep crater walls, and manoeuvre into tight spaces with ease.

The Chariot – so named because the current model has no seats, windows, or doors, and can be driven from the rear – can also lower its chassis to the ground making it easier for astronauts in bulky spacesuits to climb aboard.

The design builds on lessons learned from Spirit and Opportunity, NASA's twin rovers that have been exploring Mars for the past four years.

Both continue to limp across the Red Planet despite each having lost control of one their six wheels. Having six pairs of wheels, each powered independently, should allow Chariot to carry on functioning should anything go wrong with one of its wheels.

The current prototype uses fans to cool its battery-powered motors. This would not be possible on the moon, so finished versions will disperse heat by circulating fluid instead.

Improvements planned

Initial tests of the vehicle's speed, turning capacity, and ploughing ability at the Lunar Yard have exceeded its designers' expectations. Chariot's engineers are, however, trying to improve steering response times. They also hope to give the vehicle the ability to raise or lower each individual wheel to keep its chassis level on uneven ground.

The lunar truck, which was designed and built in 11 months at a cost of approximately $3.5 million, will undergo further testing this summer at Moses Lake State Park in Washington State, where the region's steep, shifting sand dunes offer similar topography to that of the moon.

Junkin says these tests, scheduled for the first two weeks of June will be open to the public. "America paid for it, they ought to be able to get a chance to see it at work," he says.