This summer, a team of engineering undergraduates will plummet 8,000 feet out of the sky, and they’ll do it eighty times in two days. As a part of NASA’s Reduced Gravity Research Program, 10 students from the University’s Student Space Systems Fabrication Laboratory, or S3FL, will test a new satellite design on a series of microgravity flights out of Johnson Space Center in Houston.
To create the effect of weightlessness, a NASA C-9 jet, also called the “Vomit Comet,” climbs from 24,000 feet to 32,000 feet, then dives back down to repeat the process. As the jet rapidly changes from a steep dive to an equally abrupt climb, the passengers and cargo are shoved to the floor by twice the normal force of gravity.
Then, as the jet reaches the top of its trajectory, it enters a controlled free-fall, simulating zero gravity. At this point, gravity is actually as strong as ever, but the plane is falling just as fast as everything inside so there is no force holding objects down – the floor is literally falling out from under them. This is the same reason astronauts experience microgravity while in orbit.
The S3FL students will conduct microgravity experiments to assist with the Air Force-funded Tethered SATellite Testbed, or TSATT. The project is comprised of two small satellites connected with a kilometer-long tether.
“The goal of TSATT is to prove the concept of formation flying and rendezvous technologies using a tethered satellite pair,” said Ashley Smetana, Engineering junior and chief engineer on the C-9 microgravity project.
Formation flying will eliminate the need for difficult planning and calculations in the control room every time a satellite needs to be moved while in orbit. In addition, a group of small satellites flying in formation could do the job of a much larger satellite for a fraction of the cost. It will benefit scientific research as well as reconnaissance missions. Rendezvous technologies are crucial, too. They will allow satellites to safely dock with one another in orbit, a very important ability for robotic and manned missions.
The work done by the S3FL students will help to predict how the satellites will behave as they separate. Two spinning satellites connected by a tether can have very complicated behaviors, so it is crucial to know what to expect before launching the full-scale TSATT into orbit. This will directly help the TSATT team avoid problems during the initial deployment.
On the C-9 flights, the students will test a scaled-down version of TSATT to understand how it behaves as the two satellites separate. While in microgravity, after giving the TSATT model a certain spin, a signal will be sent to release the pins holding the satellites together. As they pull apart, two digital video cameras will follow the positions of colored tracking stickers on the model.
Back on the ground, “the image of the satellite will be imported into a computer program which will read the colored stickers and decipher where each sticker was and how it moved from frame to frame,” said Suzanne Lessack, assistant lead on the project and Engineering freshman. “A 3-D model will be generated on the computer and we will be able to recreate what happened in our experiment and analyze the data.”
Participating in a gut-wrenching microgravity flight is not easy. Several weeks ago, the S3FL students submitted their project proposal to NASA. Once approved, they earned the chance to fly on the plane by putting in long hours designing and constructing the satellite.
Finally, after passing a flight physical, they are subjected to centrifuge testing to become familiar with rapidly changing levels of gravity. “I think flying will be a great experience,” Smetana said. “It’s not something every undergraduate gets to experience, so flying a project we’ve worked so hard on will be very rewarding,” The microgravity flights will take place this June.
The Student Space Systems Fabrication Laboratory is entirely student-run, and participates in a number of engineering projects.
In addition to the C-9 microgravity project, a team is involved in studying tether re-entry deceleration: the use of a trailing tether to slow the fall of a re-entering satellite. Another group is developing robotic space elevator technology, a concept that may revolutionize access to space.
Three teams are also working on developing and launching cansats: small can-sized atmospheric probes that record temperature and pressure over a range of altitudes.