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On Top of the World

In an experiment transcending the classroom, Viterbi School’s Zero G team takes their fire ball experiment for a ride on NASA’s Vomit Comet

April 26, 2007 — Weightlessness wasn’t anything like Emily Hedges imagined it would be. It wasn’t like being on a roller coaster.  It wasn’t like swimming either. 

“If anything, it was like spinning,” said the junior aerospace engineering major.  “If you tried to swim and flailed your arms, you didn’t get anywhere.”

Quinn Freyermuth, center, stands teammates John Duncan, left, and Emily Hedges, right, upside down onboard the Vomit Comet. 
— Photos courtesy of Johnson Space Center.

Adriel Carreno said it was like a “30-second freefall.”

“I ended up in the middle of the cabin, and I couldn’t reach anything, so I started swinging my arms and legs,” said the junior, who is majoring in mechanical engineering. “I was trying to grab on to something before we got to 2 g.”

“No one threw up,” added Viterbi School team captain Daniel Calvo, a junior in aerospace engineering.  “But we were smart.  We strapped ourselves down for the first parabola. It would have been catastrophic if we hadn’t.”

In an experiment that transcended the classroom, Hedges, Carreno and Calvo, and two additional classmates, hitched a ride aboard NASA’s DC-9 Vomit Comet this spring to test a flame experiment outside the bounds of gravity.  The Viterbi School students were among 34 university teams across the country given a chance this year to purpose, design, fabricate, fly and evaluate a reduced gravity experiment of their choice aboard the space agency’s one-and-only microgravity aircraft. 

It didn’t take much convincing to get this team — all members of a new student exploration club at USC called Students for the Exploration and Development of Space (SEDS) — down to Johnson Space Center for 10 days of training, tours and flying.  After arriving at the space facility, they traveled to Ellington Field, located 17 miles southeast of downtown Houston, to see the Vomit Comet and NASA’s fleet of shuttle training aircraft.  At Johnson Space Center, they toured the Neutral Buoyancy Laboratory, a huge water tank at JSC used to train astronauts who will work on the international space station, and visited the historic Apollo mission control center.   

Adriel Carreno floats off the floor as the aircraft reaches 2 g. "It felt like a 30-second freefall," he said.  

The training for weightlessness was stretched over many days and many drills, but after about a week, the team was ready for flight. Each of the participating teams were given two flight days to conduct their experiments.

USC's team soared over the Gulf of Mexico, lighting fire balls near the pinnacle of each parabola to find out how fast fire would burn in three different atmospheres. The DC-9 aircraft flew 30 parabolic maneuvers each flight day, giving students 60 chances (2 flights x 30 parabolas/flight) in all to experience near weightlessness (1.8 g to 2 g).  Low gravity occurred each time the plane climbed to the top of its arc and “nosed over” to begin its descent. 

“It felt like being right at the top of a roller coaster ramp, and then you get pulled down, except that it lasted for 25 or 30 seconds,” said John Duncan, a junior in aerospace engineering.

“The first parabola was the most disorienting for me, because all of a sudden I was floating off the floor,” Hedges said.  “I remember trying to hold down onto a strap, but that was surprisingly difficult. It takes a little while to learn to relax and just float. The more you tense up, the more out of control you feel.”

 “The thing that you don’t realize about zero G is that it’s not just that you’re weightless, but that everything just starts floating around, and if you have the slightest movement, you’ll float away,” added Calvo. 

The experiment started just as the aircraft reached zero G. Floating over to three test chambers, Calvo and the others lit wax balls standing on pedestals inside the clear plastic boxes, which were filled with different gaseous atmospheres.  One box was filled with oxygen diluted with carbon dioxide (CO2); another with oxygen and helium (He); and the third with oxygen and nitrogen (N2).  After lighting the wax balls, the team observed how fast the fire burned.

Daniel Calvo ignites a fire ball inside one of the experimental boxes during weightlessness. Adriel Carreno is behind him.

“Fire burns very differently in space than it does on Earth, especially in the microgravity environment that we have aboard the space shuttle or on the international space station,” Calvo said.  “We were interested in finding out if the fire extinguishers onboard the shuttle and space station are really the best for space flight, because they use a CO2-based fire suppressant, like the ones we use on Earth, but in space, CO2 may actually increase heat transfer."

CO2 is a radiatively active gas and increases the heat transfer by radiation to a flame.  Helium is just the opposite; it is a radiatively inactive gas and is likely to decrease the heat transfer by radiation to a flame.  A nitrogen-based atmosphere was used to simulate the type of environment that is present in manned space vehicles.

Things didn’t go exactly as planned.  The boxes had been jiggled during takeoff, which created a few mechanical problems.  The igniter didn’t always light.  The experimental chamber for nitrogen malfunctioned.  And floating around while trying to conduct the experiments made it all the more difficult to pull off.    

After a few awkward attempts, Hedges said, they got used to the ups and downs of the Vomit Comet and began to collect data from the CO2 and He experiments.

“We were really excited to get the wax balls to ignite in microgravity,” she explained.  “They formed these awesome spheres of flame for about half a second.  For the tests that we were able to run, the carbon dioxide atmosphere did produce hotter flames than the helium ones.”

Most of the Zero G team, with feet planted firmly on the ground. Top, left to right: Daniel Calvo and John Duncan. Bottom, left to right: Emily Hedges and  Adriel Carreno.

“Twenty-to-30 degrees hotter than the helium fire,”Calvo added. “Even though we didn’t get any hard data for the nitrogen atmosphere, we have enough qualitative data to warrant flying the experiment again next year.”

With some refinement and additional testing, the students plan to enter an improved version of the fire ball test chamber in the 2008 Reduced Gravity Student Flight Opportunities Program.  So stay tuned.  If all goes accordingly, they hope they’ll be spending next spring break flying many more parabolas over the Gulf of Mexico. 

Other members of the USC team included Quinn Freyermuth, a junior in mechanical engineering, and Mikeala Blackler, a junior in industrial systems engineering.  Eugene Bickers, a physics professor and associate vice provost for undergraduate programs, and former astronaut Paul Ronney, a professor of aerospace and mechanical engineering, served as advisers