FONTANA, Calif. ? They’re a motley bunch of garage tinkerers, off-road enthusiasts, high-school students, physicists and programmers who hope their microprocessor-jammed jalopies usher in the next generation of military combat vehicles.

The question is, can any of these meticulously engineered, unmanned autos actually make it across the Mojave Desert on their own?

On Saturday, the Defense Advanced Research Projects Agency, the Pentagon’s few-holds-barred research and development arm, will award $1 million to the first team whose robotic vehicle can cover a rugged desert course from Barstow, Calif., to Primm, Nev., in less than 10 hours.

The vehicles in the so-called Grand Challenge, part of Pentagon efforts to have one-third of all ground vehicles unmanned by 2015, cannot be controlled remotely. They’ve got to navigate all by themselves.

“It’s a marriage of the geeks and the greaseballs,” said Sal Fish, a longtime desert off-road race promoter and the lead designer of the course. “If they go even two miles, I’ll be in awe.” Five teams dropped out of the competition even before qualifying runs began Monday, leaving 20 entrants.

Two hours before the race begins, DARPA will give competitors a CD-ROM with Global Positioning System coordinates that chart the eastward course.

A DARPA vehicle will be assigned to each robot contestant, with a judge ready to hit a kill switch if it goes astray. Helicopters will also monitor the action.

DARPA officials are considering several possible routes along dirt roads and rough trails, ranging from 150 to 210 miles. Even the shortest course would require the robots to average 15 mph, a feat that has eluded major defense companies.

Several of the robots are capable of 65 mph but obstacles along the way will require them to go much slower as they rely on combinations of orientation devices ranging from GPS satellite positioning to digital compasses, ultrasonic scanners and gyroscopes.

California Institute of Technology's robotic vehicle negotiates an obstacle course in Fontana, Calif. It was one of 20 teams Monday involved in qualifying tests for race across the Mojave Desert.

If no one finishes on time — a likely outcome, many participants say — DARPA will host another contest, probably in 2006.

All eight teams that took part in Monday’s trials failed in their first try at finishing a flat obstacle course a little longer than a mile that was strewn with bricks, gravel patches and metal rods.

Only two teams — from the California Institute of Technology and Palos Verdes High School in a wealthy suburb of Los Angeles — made it very far past the starting line on their first attempt. The other six had immediate mechanical problems and were making modifications before trying again.

The other 12 teams were making their first runs Tuesday and it was expected that the field would be winnowed further.

In addition to military uses, technologies growing out of the race could eventually find form in such inventions as collision avoidance systems for cars or automated farm equipment.