Engineers think there's a better way to explore the moon or Mars than stationary landers or slow-moving rovers -- hopping robots that can leap over boulders, land inside pits and survey tall peaks.
NASA is getting a lot of mileage out of its two Mars rovers, which have been exploring opposite sides of the Red Planet since 2004. But Spirit is trapped in sand and Opportunity has been trudging along for more than two years now on its way to Endurance Crater, a tantalizing site for science located about 14 miles from the rover's original landing spot.
"Rovers can't cover great distances because of the terrain," Seamus Tuohy, director of space systems at Charles Stark Draper laboratory in Cambridge, Mass., told Discovery News. "Scientists told us they'd like to get a picture of a planet on a regional scale. They'd also like to get to places that a rover can't get to ... into valleys, on the top of a hill."
Enter Talaris, the Terrestrial Autonomous Lunar Reduced Gravity System, a prototype robot under development at the Massachusetts Institute of Technology in partnership with the non-profit Draper Lab. Rather than wheels, Talaris would use chemical rocket thrusters to launch itself off a planetary surface, hover, fly to a new location and gently lower itself to the ground again.
"We do this on Earth all the time -- we call it a 'helicopter,'" Tuohy said.
The challenge is designing a system that can operate in low-gravity environments.
Testing the technology on Earth presents another set of problems, one that the engineers have resolved by designing a prototype with ducted fans, powered by cold gas jets, to counter the force of Earth's gravity. Tests of a coffee table-sized demo are under way at MIT, with the first outdoor flight slated for April.
"We believe that once we demonstrate that hopping is possible, others will fall in line and say 'Yes, this is how we should do future science missions,'" said Bobby Cohanim, the project's technical leader.
A Talaris also is in line for a test run on the moon. A team called Next Giant Leap is developing a hopping robot to compete in the Google-sponsored Lunar X Prize. The contest, which has drawn 29 contenders, requires teams to meet various milestones, including having their lunar vehicles travel at least 500 meters.
"It might take days for a rover to go 500 meters. A hopper can do it in minutes -- or seconds depending on how fast you want to traverse," Cohanim said.
Jeffrey Hoffman, a former shuttle astronaut and professor of astronautics at MIT, points out that hoppers could be used to explore worlds like Titan, a Saturn moon covered with rivers of methane.
One shortcoming of hopper probes is fuel. Unlike solar-powered rovers, hopping vehicles need chemicals to power their thrusters.
"Eventually you're going to run out of fuel," Hoffman told Discovery News, though scientists and engineers are working ways to manufacture propellants indigenously from resources on planetary bodies.
Besides, adds Cohanim, once fuel is gone, a hopper's science mission can continue on as a sedentary one.