New Jetpack Aims to Steady Astronauts on Asteroid Mission
On Feb. 12, 1984, astronaut Bruce McCandless ventured further away from the confines and safety of his ship than any previous astronaut had ever been using a nitrogen jet propelled backpack.
A simple act, such as turning a wrench or using a power drill, can threaten to send free-floating astronauts tumbling out of control in space. But a technology first tested in NASA jetpacks during the Skylab era of the 1970s could help steady astronauts against unwanted rockiness on future spacewalks.
New simulations have shown how spinning gyroscopes — technology used in the International Space Station and the Hubble Space Telescope — can stabilize astronauts better than jetpacks alone in low-gravity environments. The results may improve the design of NASA's next-generation jetpack for astronauts to wear during planned missions to near-Earth asteroids.
"People are going to be doing spacewalks differently in the future without the shuttle and once they're away from the space station," said Jeff Hoffman, a professor of aeronautics and astronautics at MIT.
Hammers in space
Astronauts who conduct spacewalks from the International Space Station (ISS) have the luxury of standing on a robotic arm or using other stabilizing work platforms, but free-floating astronauts working in a low-gravity environment must rely on their jetpacks alone to counteract the forces of their own motions as they hammer or drill away.
Hoffman experienced that sense of instability as a former NASA astronaut who conducted spacewalks to repair a malfunctioning satellite and the Hubble Space Telescope.
"I've done free-floating spacewalk work — you're really unstable," Hoffman told TechNewsDaily. "Every time you exert a force that doesn't go through your center of mass, it tends to not just move you but to also twist you."
Hoffman and his colleagues at the Draper Laboratory, a nonprofit research and development organization in Cambridge, Mass., see gyroscopes as the answer to steadying space explorers as they shovel, scoop and drill samples from asteroids. The Draper-funded project aims to prove that idea for the benefit of future NASA missions.
"ISS could benefit from this work, but we were inspired to test this concept because of humans visiting asteroids," said Bobby Cohanim, a mission design group leader at Draper Laboratory.
The team's computer simulations suggested that a jetpack combined with four gyroscopes would provide greater stability for astronauts than a jetpack by itself. That's because the spinning, electric-powered gyroscopes can turn in a smooth, continuous motion to compensate for any instability, but a jetpack must rely on the "bang bang" action of firing its cold-gas jets in a jerky, start-stop fashion.
The simulation also found that the gyroscopes helped reduce the jetpack's consumption of gas propellant by almost 66 percent during an asteroid mission scenario. Propellant savings equivalent to about 4 lbs. (1.81 kilograms) per simulated run gave researchers a rough idea of how much mass the gyroscopes can take up in the new jetpack design.
Back to the future
NASA first tried out gyroscopes in a prototype jetpack aboard the Skylab space station in the 1970s. That experiment led to the use of gyroscopes in the Manned Maneuvering Unit jetpack flown on three space-shuttle missions in 1984. But NASA's current jetpack, called Simplified Aid for EVA Rescue (SAFER), uses only jetpacks because of its function as an emergency rescue device for astronauts stranded in space.
The older gyroscopes tested aboard Skylab represented larger, clunkier and more power-hungry devices compared to the gyroscopes of today. Draper Laboratory and MIT hope their next-generation jetpack design can save enough jetpack propellant to make up for the added mass of the gyroscopes and their electrical power supply.
Tests of the combined-jetpack-gyroscopes concept are scheduled to take place this summer at NASA's Virtual Reality Lab at the Johnson Space Center in Houston. Unlike the computer simulations, the tests would involve real people wearing virtual-reality helmets and haptic-feedback devices to experience a virtual spacewalking scenario with the new spacesuit jetpack.
Cohanim hopes to develop a hardware prototype of the jetpack for testing in the NASA Johnson Space Center's microgravity simulator — and perhaps eventually aboard NASA's Vomit Comet aircraft that uses steep dives to simulate the weightless sensation of being in space.