Leaps and Bounds

Unmanned wheeled rovers have explored the surface of the moon and Mars for decades, but they can’t crawl inside craters, scale cliffs, or travel quickly over rough terrain.

For two years, a team of students led by former NASA astronaut Jeffrey ­Hoffman, a professor of the practice in astronautics, has been collaborating with Draper Lab engineers to design and build a prototype for a new type of robotic explorer that would hop rather than roll across a planetary surface. Hopping, they believe, would make it easier to access tricky sites and travel greater distances–and collect more data during a mission.

Known as the Terrestrial Artificial Lunar and Reduced Gravity Simulator, or Talaris, the three-foot-wide vehicle is a smaller version of a hopper that would be used in space. It is designed to go about 20 meters per hop; space-based hoppers might cover tens of kilometers–or possibly more–in a single bound. The team that built Talaris wants to use it on Earth to test guidance, navigation, and control software developed by Draper that would allow the space-based hopper to navigate autonomously.

The prototype was developed as part of MIT’s effort to win the Google Lunar X Prize, a $30 million competition to get a privately funded spacecraft to reach the moon, travel 500 meters across its surface, and transmit video, images, and other data back to Earth. Both MIT and Draper are members of Next Giant Leap, one of about 20 teams registered in the competition.

Talaris uses two propulsion systems. One has electric ducted fans that provide lift to counter the vehicle’s weight and simulate the gravity environments of different planetary bodies. The other uses compressed nitrogen gas to maneuver the vehicle in the simulated conditions. This arrangement allows the researchers to test different navigation algorithms on Earth to perfect the control software.

The Talaris team is confident that hoppers can be used to explore any body in the solar system that has enough gravity to make hopping feasible, including asteroids. (Very small asteroids or moons might not have enough gravity.) Because hoppers can “simply hop in, collect data, and hop out,” Hoffman says, they can be used to do such things as explore deep craters on the moon that are thought to contain water, measure the magnetism of steep cliffs, or travel quickly to different locations to set up a network of seismometers. Astronauts orbiting Mars could even use a high-bandwidth signal to tele-operate hoppers on the surface of the planet.

The Talaris researchers are finalizing construction of the hopper and hope to complete a 20-meter test hop by the end of the calendar year. If Next Giant Leap is able to secure funding, a large-scale hopper could take flight by the end of 2014, the deadline for Lunar X Prize contestants to complete a trip to the moon.