Engineering Students' Parachute Prototype Designed to Bring Small Satellites Back to Earth
April 29, 2012
Miles above the surface of the Earth, it's getting a bit crowded. A photograph from space reveals millions and millions of pieces of former satellites and other "space junk" making lonely, endless orbits around the globe.
How do we keep this man-made material from negatively affecting future orbital activity? Part of the answer is in creating mechanisms to bring these objects down when their work in space is done.
A group of senior engineering students at Old Dominion University have spent their final undergraduate semester wrestling with this issue. And they hope one day that their prototype design for a "parachute" to make tiny satellites fall back down to Earth gets tested by being blasted into orbit.
"If you look at an accurate photo of Earth debris and orbiting satellites, it's like a big snow globe up there," said Juan Parducci, a senior in mechanical engineering from Alexandria, Va. "What we've tried to design is a passive de-orbiting system to bring a small satellite back to Earth within 25 years, after its mission has been completed."
It was one of the projects that students could sign up for in the senior capstone design course in ODU's Frank Batten College of Engineering and Technology. Parducci and two other senior mechanical engineering majors from Virginia - Kimberly Scheider from Fairfax and Todd Estep from Chesterfield - comprised the team working on the passive de-orbiting system under Bob Ash, Eminent Scholar and professor of aerospace engineering.
Their job was to create an apparatus that would cause a "CubeSat," a 10-centimeter-cubed satellite used commonly to complete small tasks in orbit, to return to Earth within 25 years after its mission has been completed. The challenge? "We couldn't add any mass, volume or power requirements to the device. And it needed to activate on its own," Scheider said.
The team stayed within these restrictions using a sublimation method, a process in which a solid turns directly into a gas. This occurs when the pressure and temperature combinations are right for the specific substance.
The students placed a small quantity of benzoic acid inside a balloon and performed tests in a vacuum chamber facility. Tests have shown that in orbit, the powder will turn into a gas, and that vapor pressure will cause the balloon onboard the CubeSat to inflate.
"The density of the thermosphere, the layer of the atmosphere in which most satellites are placed into orbit, is very low but sufficient enough to de-orbit a satellite in 25 years. As long as our 'parachute' - the balloon onboard the CubeSat - is sufficiently large, meeting the time requirement won't be a problem," Parducci said.
When this "parachute" is deployed, it will gradually cause the CubeSat to fall out of orbit.
Due to the popularity of the project, the trio ended up working with four more students on two other teams, who are tackling different aspects of the same project. One of the teams is focusing on the structural analysis of a nano-satellite during a launch environment, and how it can withstand the rigors of leaving the Earth's atmosphere. The other, a command and control group, is working on data transmission issues in order to manipulate a CubeSat while it is in space.
Nathan Schwinn from Norfolk and Gregory Lemmer from Centreville, Va., are working on the structures team, while Dylan Blackshear of Hampton and Trevor McCarthy of Stephens City, Va., are working on command and control. All four are mechanical engineering majors.
The ultimate hope is for the work of all seven students to be passed down to future capstone classes, and one day for the ODU creation to hitch a ride on a rocket, testing their concept in space.
For Parducci, who has an internship at NASA Jet Propulsion Laboratory in Pasadena, Calif., this summer, and Scheider, who will do an internship at NASA Langley, seeing their work in space would be the ultimate manifestation of their hands-on experience.
"It's what we all want to do, and why we signed up for this project," Scheider said.