One high-flying group of engineering students discovered the heavy importance of gravity in a few moments of weightlessness.
The team, dubbed the Moon Goons, participated in NASA’s Reduced Gravity Education Program in June. They spent a week at NASA’s base in Houston to learn about space, experience safe zero-gravity flying, and prepare and fly their experiment.
The students experienced near-zero-gravity thanks to NASA’s custom Boeing 747 airplane, commonly called “the Vomit Comet.” The plane flies in parabolic arcs, first shooting up in a steep climb, subjecting its passengers to a body-crunching 2G – twice the gravity at Earth’s surface – before taking a nosedive, leaving its occupants weightless for about 30 seconds. The plane goes through this cycle multiple times per flight.
“You don’t get tired of zero-G – it’s just really cool every time,” says Dan Hirnyj, the team leader of the Moon Goons, who graduated in May with a degree in engineering physics. Hirnyj put together a cross-disciplinary team including electrical and computer engineering students Alejandro Gomez, Ehsan Keramat and Sunny Gautam; computer science student Sam Liu; and materials science and engineering student Linas Sulas.
NASA annually chooses about 15 proposals to participate in the program, from more than 70 applications. The Moon Goons devised an experiment using visual navigation to dock a drone – a computer-controlled quadrocopter. The drone, fitted with a camera, used visual input to align itself to a custom docking station that the students built, much in the way that NASA engineers might want to guide small satellites or landing modules to a target. It also used magnetic braking to slow down as it approached the target.
“It’s an interesting problem,” said computer science instructor Lawrence Angrave, the Moon Goons’ faculty adviser. “We were using the quadrocopter as a stand-in, but the navigational principles and alignment principles are the same no matter what technology you’re using.”
The drone was controlled by a laptop computer running a vision algorithm that searched for a red cloth background and quickly made power adjustments to the four propellers to turn the drone toward the red cloth.
“Analyzing images is an active area of computer science research,” said Liu, who was responsible for the quadrocopter’s vision system. “We simplified the processing required by using a large red cloth and a faster color-moment algorithm. It was fast and sufficient to tell us when the craft had rotated away from the desired docking angle so we could add extra thrust to some of the fans.”
Thanks to Gautum, the computer received a wireless video stream of 15 pictures per second from a camera mounted on the side of the quadrocopter. The software translated the real-time camera images transmitted from the quadrocopter into power changes of each of the four motors. Gautum developed the communication system and also discovered how to work around the drone’s built-in software that assumed it was operating in Earth’s gravity.
The Moon Goons were given two days of zero-G flights to test their docking system. Before the flight, the team’s NASA mentors dispensed anti-motion sickness medication and reminded the team that avoiding neck movements and staying still during the 2G pull-up phases would help avoid motion sickness. But no amount of advice could prepare them for the disorientation of weightlessness.
“Zero-G is difficult,” Angrave said. “Now we understand why astronauts move slowly. The smallest of pushes will send you drifting and tumbling away. Even just starting the experiment was challenging.”
The first day of zero-G flight proved taxing to the Moon Goons when the quadrocopter failed to fly during the short weightless periods. The team had set the motors’ thrust to minimum, not wanting the drone to shoot up too quickly without gravity. However, the minimum thrust was not enough to overcome friction and fly the drone to the docking station.
The team scrambled to adjust the settings. Zero-G flight requires all tools, bolts and loose items be accounted for and the experiment be strongly secured, so the Moon Goons’ drone and docking system had to be completely contained within a clear plastic box. Electrical and computer engineering senior Gomez worked furiously at the laptop debugging and recompiling code while his long dreadlocks drifted in all directions around him.
While the team was not able to fix the settings on the plane the first day, after a night of teamwork to rewrite the control software, the second day’s experiments were successful. The drone flew, oriented itself and docked smoothly.
The trip was the last time members of the Moon Goons, all graduating seniors, worked together as a U. of I. team. But the new graduates and Angrave hope that others will take up the Moon Goons mantle and apply for the Reduced Gravity program in years to come.
“Something like this gives you an experience you won’t get just by doing your classes,” Hirnyj said. “I would highly recommend that anyone thinking about being an engineer involve themselves in a project that gives you the opportunity to start at nothing and progress all the way to a finished project, whether it’s an experiment or engineering competitions. It really makes you look at the big picture. It involves a lot of planning, a lot of work, but it prepares you for the environment that you would be working in as a full-time employee.”