A balloon-shaped robot explorer that one day could search for water on other planets has survived some of the most trying conditions on planet Earth during a 70-kilometer (40-mile), wind-driven trek across Antarctica.
|This is not your parent's Mars rover. A giant inflatable ball -- bearing little resemblance to better-known rovers like Sojourner or MER -- might someday prowl the surface of the Red Planet. A 6-meter diameter ball on Mars could accelerate to about 10 m/s (22.4 mph) pushed along by Martian afternoon winds of 20 m/s (44.7 mph).
Credit: NASA JPL
The Tumbleweed Rover, which is being developed at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif., left the National Science Foundation's Amundsen-Scott South Pole Station on Jan. 24, completing its roll across Antarctica's polar plateau roughly eight days later.
Along the way, the beach-ball-shaped device, roughly two meters (six feet) in diameter, used the global Iridium satellite network to send information about its position, the surrounding air temperature, pressure, humidity and light intensity to a JPL ground station.
The test was designed to confirm the rover's long-term durability in an extremely cold environment, with an eye toward eventually using the devices to explore the Martian polar caps and other planets in the solar system. It reinforces the findings of a test conducted previously on the Greenland ice cap, also carried out under the auspices of NSF's Office of Polar Programs (OPP).
OPP manages the U.S. Antarctic Program, arranging logistical support and infrastructure for NSF-supported scientists as well as other government agencies, such as NASA, when they conduct science in Antarctica.
The final Tumbleweed Rover is envisioned as a lightweight, roughly 40-kilogram (88 pound) device that can serve multiple roles as an independent robotic explorer. The rover's design allows it to act as a parachute while descending through an atmosphere, an air bag on landing, and, ultimately, as an unmanned vehicle equipped with a package of scientific instruments.
'Tumbleweed' is the brainchild of several JPL scientists, including Alberto Behar, a researcher with JPL's robotic vehicles group.
|The spherically-wheeled rover that inadvertently gave birth to the idea for a giant tumbleweed ball. When one of the wheels broke loose during a test, it traveled across the terrain only too well
Credit: NASA JPL
During a three-day deployment at the South Pole, Behar unpacked, assembled, inflated, tested, and deployed the rover. He says that the efficiency of the deployment is testament to Tumbleweed' s cost-effectiveness and ease of use.
Even though the average external temperature during the rover's deployment approached minus 30 degrees Celsius (minus 22 degrees Fahrenheit), the rover kept its internal instrument payload at an average temperature of roughly 30 degrees Celsius (86 degrees Fahrenheit) using excess heat from the instrument electronics circulated by an air pump.
The ultra-durable ball reached speeds of 30 kilometers per hour (18 miles per hour) over the Antarctic ice cap, and traveled at an average speed of about six kilometers per hour (3.7 mph). The winds at the South Pole were unusually low during the test. As a result, the rover did not move at all for several periods during its deployment.
But, even taking those lulls into account, Tumbleweed managed an average speed of 1.3 kilometers per hour (0.8 mph) over the course of the deployment. Such speeds are unattainable in conventional, mechanical rovers--such as Spirit and Opportunity, currently operating on the surface of Mars--which average little more than 0.05 kilometers per hour (0.03 mph) on flat, dry ground.
Behar said the rover's design is especially well suited for polar missions that use instrument packages to look for water beneath the surface of an ice sheet, a task that cannot be done accurately from orbit.
Plans to construct the next generation Tumbleweed rover are already underway at JPL.
|View of Mars Exploration Rover (MER) mission as landing airbag deploys above Martian surface. Credit: NASA/JPL MER
Design refinements are likely to focus on reducing the rover's weight and rolling resistance to lower the minimum winds needed to propel the rover and enable it to travel farther and adapting the payload to include a ground-penetrating radar or magnetometer to conduct ice surveys.
Behar said he hopes an updated version of Tumbleweed will be deployed again in late 2004 or early 2005, and that the Tumbleweed design may one day find itself rolling over the polar icecaps of Mars.
NSF is an independent federal agency that supports fundamental research and education across all fields of science and engineering, with an annual budget of nearly $5.58 billion. NSF funds reach all 50 states through grants to nearly 2,000 universities and institutions.