Cornell students test new robotic arm in NASA's "Vomit Comet"

By Kenny Berkowitz

As NASA’s “weightless wonder,” a modified McDonnell Douglas C-9, approaches the top of its arc, there’s a slight rumble before the engines grow quiet. Then, as the fliers begin their descent into zero gravity, their bodies rise into the air, and time seems to slow down.

Nicole Monahan ’11 experiences microgravity while M.Eng. student Qing Liu ’07 ME commands the robotic arm to move to get data on its power performance. -NASA

“You get a tingling in your stomach, like you’re about to slide down a roller coaster,” says Master’s of Engineering student Tim Ulm ’07 ME, back in Ithaca after flying 32 parabolas in NASA’s Reduced Gravity Student Flight Opportunities Program. “Then in an instant, once your body starts to lift off the floor, there’s an initial rush, and everything changes. The tingling fades, all sensation fades, and once your body recognizes that you’re floating, you feel completely free. Once you realize you’re not going to spontaneously combust, all the anxiety drifts away, and you want to embrace that feeling, play with it. But everything comes at you so quickly, until you suddenly remember you’re supposed to be focusing on the experiment. So you pull yourself back, ignore how it feels, and remind yourself to press the right buttons on the laptop.”

It’s the beginning of Study Week, and with the sound of machines whirring all around their basement laboratory, the members of Cornell’s Microgravity Research Team huddle around a pair of tables. The four fliers—Ulm, Mark Amato ’07 ECE, and Qing Liu ’07 ME,  all Master of Engineering students, and Nicole Monahan ’10—and their eight teammates have just come back from Houston, where they successfully tested their gyroscope-driven robotic arm in zero gravity, and though they all need to catch up before finals, the mood around the table is spirited and the conversation is about riding the “Vomit Comet.”

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M.Eng. students Tim Ulm ’07 ME and Mark Amato ’07 ECE get used to weightlessness in preparation for their experiment. -NASA

At first, I was very worried that I would, well, do what the name of the plane suggests,” says Liu, who is co-leading the 2007–08 team with Monahan. “For the first two zero-gravity parabolas, I felt really nauseous, like I was going to be sick. You really do feel disoriented in zero gravity, because there’s no real sense of up or down. But then, on the third parabola, I remembered this book I’d read about some kids in space. They get over their nausea by thinking of their feet as being down, no matter what their orientation. So that’s what I did, and I was completely fine for the rest of the flight. And it became this very stimulating, perspective-altering experience that I couldn’t have gotten any other way.”

Now in its third year, the student-run project began with a plan to design a space telescope that would use gyroscopes to power its movements. From there, the project shifted direction, trying instead to design a prosthetic human arm to be used here on Earth; but after a disappointing first year, the second team decided to begin its work from scratch, changing direction again to concentrate on building a robotic arm that could operate effectively in space.

The three projects all share a common center in mechanical engineering, which most of the teammates are currently studying. For years, aerospace engineers have used control-moment gyroscopes (CMG) to orient their spacecraft, and in theory, a motor driven by scissored pairs of CMGs could be used just as easily on a smaller scale, providing a low-energy, high-efficiency control mechanism for a robotic arm to move objects from one place to another.

Amato, Monahan, Liu, and Michael Stocke ’07 explain their experiment to NASA officials to verify they have followed safety procedures, have working equipment, and have prepared appropriate operational guidelines. -NASA

As part of their outreach work, the team has been traveling to elementary schools around the county, where they explain the project with the help of a rotating bicycle wheel, a Sit ’n Spin, and a little Newtonian physics. One at a time, the children stand on the Sit ’n Spin while tilting the bike wheel from side to side. When the wheel spins clockwise, the Sit ’n Spin turns counter-clockwise; when the wheel is tilted to rotate counter-clockwise, the Sit ’n Spin responds by turning clockwise.

Though the movements seem counter-­intuitive, they serve as a quick demonstration of the conservation of angular momentum. At its simplest level, the wheel represents a gyroscope spinning freely on its axis. When it’s connected to the Sit ’n Spin, the two behave as a pair of counter-rotating discs, transferring angular momentum from one to the other. Like the wheel-and-turntable combination, the team’s robotic arm requires very little power to move even relatively heavy objects; in the frictionless environment of space, the robotic arm’s hauling potential is even greater. Cornell’s arm is motored by three pairs of CMGs, one at each joint, that generate a constant, easily controlled gyroscopic torque; because the pairs are scissored, the angular momentum of the tilting CMGs always points along the joint’s axis of rotation, changing the joint’s spin speed as they tilt but requiring virtually no input power to maintain that motion.

A NASA medical officer assesses Amato’s flight readiness.  -NASA

According to team calculations, a gyroscope-powered arm could be as much as 90 percent more efficient than the more familiar flywheel-driven arms that could be used onboard the international space station. If the team’s numbers are accurate, there would be more than enough reason to begin manufacturing the arms commercially, and in the short term, say a decade from now, they might be used to assemble a spacecraft from component parts or perform repairs on a broken satellite. In the long term, still decades away, the technology might be adapted to power environmentally friendly factories on our own planet, using a fraction of the energy used by contemporary manufacturing.

That’s what brought Cornell’s MRT to Houston, and the purpose of attending NASA’s Microgravity University was to put that theory to the test in zero gravity, where conditions are dramatically different from anything they could find here on the ground. “Power is in very short supply in space,” says Mason Peck, assistant professor of mechanical and aerospace engineering and faculty adviser to the MRT. “NASA simply can’t launch a space station intact. They have to send it in pieces, and in-orbit construction is a task that could be done by robots, and probably will be. With this technology, you can move extremely fast without using a whole lot of power.

Students receive flight training. -NASA

“Imagine a robotic arm with a set of spacecraft components floating nearby,” he continues. “The arm picks up one component, moves it into place, then reaches for the next, and the next. Using gyroscopes to conserve momentum and energy makes a lot of sense, but nobody else has really tried to exploit this technology the way we’re doing. No one would propose driving a robotic arm this way, and I think that’s what really keeps this team going.”

After pursuing a Ph.D. in medieval literature, and even teaching English at Roosevelt University, Peck returned to the University of Texas for a bachelor’s degree in aerospace engineering. He followed it with an engineering Ph.D. from UCLA, seven years as a systems engineer at Hughes Space and Communications, three years as a fellow at Honeywell Defense and Space Systems, and several patents for his work in spacecraft dynamics.

Since arriving at Cornell in 2004, Peck has taught courses in dynamics, control, and systems engineering. He’s been given the Robert and Vann Cowie Teaching Award, and made a name for himself as a visionary behind the “starship on a chip,” a nano-fabricated device so tiny that it could be propelled through the farthest reaches of space by magnetic forces. (It doesn’t hurt that Peck’s father is a science-fiction novelist.)

Monahan experiences weightlessness during parabolic maneuver.  -NASA

The bulk of his research revolves around spacecraft dynamics and control-moment gyroscopes, and as a sideline to the work of his research group, Peck spends an hour or two a week with the MRT, working to develop an effectively hands-off approach. “If you give a student team too much autonomy, they’ll just get lost,” says Peck. “If you give them too little autonomy, they’ll never develop the independence they need. The challenge here is to find that sweet spot, because if you give them just enough direction to get them to the next problem, the results are completely theirs. It can be awkward at times, because I can’t really afford to be completely dependable, can I? For better or worse, the members of the team know they can’t rely on me to provide a solution and they can’t just look up the answer on Google. They’ve got to get used to the idea of solving problems on their own, because that’s what these student teams are really about: problem solving.”

For the members of the MRT, which won the 2007 Cornell Engineering Alumni Association’s Student Project Team of the Year Award, the lessons hit home. “From Professor Peck, I learned to always consider alternatives,” says Amato, who survived 31 parabolas before losing his lunch on the Vomit Comet’s last dive. “When we ask him questions, more often than not he tries to point us toward finding our own conclusions. Of course, they’re generally the conclusions he’s already reached, but he expects us to find the answer ourselves. It’s like giving us the keys to the car and letting us drive.”

Ulm and Amato operate the experimental robotic arm. -NASA

After applying to NASA, working for two semesters on the arm, fine-tuning their design, and testing all their components in their lab, the 2006–07 MRT flew to Houston, where they joined student teams from 33 other colleges. But as soon as they tried to retest everything on-site—and impressed NASA engineers with their project’s vast potential for injury—their power failed, and they quickly realized their work was far from finished.

Under the leadership of Josh Kennedy, M.Eng. ’07, and Michael Stocke, M.Eng. ’07, the team restored the power supply with a quick shopping trip to the mall, covered up the arm’s exposed gears with Tupperware, and padded its sharp edges with duct tape. Then, after planning all along to control the robotic automatically, they learned the last piece of bad news: In the interest of safety, NASA’s flight crew needed them to provide an in-flight human controller to keep the one-foot-tall, 63-pound arm from colliding with fliers.

Liu somersaults in zero gravity with the help of a NASA spotter. -NASA

“That was definitely a wrench in our overall plan, but they felt we wouldn’t be able to react if someone was flying toward the arm,” says Liu. “So we decided to use a spare laptop and made some last-minute adjustments to use the computer keys to control the arm. Granted, it was only four keys, but it took some getting used to, because when you’re weightless, direction doesn’t feel very intuitive.”

For the first flight, Amato and Ulm solved the challenge by strapping themselves to the laptop, and then to the floor of the plane. For the second, Liu and Monahan alternated between controlling the robotic arm, videoing the experiment, and turning somersaults in zero gravity, all under the watchful eye of space shuttle astronaut and Cornell alum Don Thomas, M.S. ’80 MSE, Ph.D. ’82, who’d come along for the ride.

Both flights followed the same plan, with 30 seconds of zero gravity followed closely by 30 seconds of hypergravity, repeated 30 times, with one Martian parabola (one-third of Earth’s gravity) and one lunar parabola (one-sixth of Earth’s gravity) thrown in for a little change of pace. For Monahan, who describes the experience as “kind of like swimming at the bottom of a pool,” the flight was gentler than expected, but for her three teammates, the hardest part came at the bottom of each parabola, as the plane climbed steeply from 0G to 2G.

“Zero gravity was fine, but being in 2G was pretty tough,” says Amato, who responded to yet another crisis by reprogramming the arm’s data acquisition module in flight. “On Earth, I weigh about 175, and I have a thin frame. But when we hit 2Gs, I weighed about 350 pounds. I thought I’d be able to hold myself up just using my abs and my trapezius. Instead, it was like wearing weights on every part of my body, and it turned out my head was a lot heavier than I thought.”

Ulm operates the experiment while Amato records the motion of the arm on video. -NASA

The team had come to Houston with high hopes of outperforming the international space station’s Canada Arm 2. Even with the problems in collecting data, and even after all the ad hoc engineering that took place on site, they made their point: The gyroscopic drive used significantly less power than that of a conventional flywheel drive.

“We proved that you could effectively use control-moment gyroscopes to actuate a robotic arm in a zero-gravity environment,” says Ulm. “Being able to put together a project like this in less than a year is a testament to the power of the ideas behind it. We may have missed some of the data, but just proving the functionality of the ideas is ground-breaking for a project team like ours.”

With the fall semester underway, a new team has formed around Liu and Monahan, with plans to either refine the existing design or begin all over again. Instead of three pairs of gyroscopes, the 2008 model will use four or five, and instead of using the laptop, it will be driven by a haptic controller attached to the arm of one of the fliers. The next prototype promises to be considerably lighter and more agile than the first, and if this year’s team is invited to return to Houston, they expect to be even more successful.

MRT Team 2006-07: Mark Amato, Diego Asturias, Michele Carpenter, Keith Corrigan, Josh Kennedy, Todd Levin, Qing Liu, Nicole Monahan, Michael Stocke, and Tim Ulm.

“It was an awesome experience,” says Monahan, who hopes to someday become an astronaut. “We built it, we actually got to test it in zero gravity, and we came back with usable data. We weren’t always sure it was going to work, but in the end, it really did. Plus, the fact that we could actually do it as students is really cool.”

“Looking back, my memories are of floating around in zero gravity,” adds Amato. “The whole thing went by so fast, but that’s really what stays with you: the feeling.”