Nasa’s Zero-G Flights Of Fancy

By | September 10, 2001 | Via Satellite

By Scott Chase

What goes up, must come down. In most cases, that old saying rings true. For a dozen aeronautical engineering students from Purdue University working on new ways to increase operational efficiencies and useful lifetimes of commercial communications satellites and other spacecraft, however, it may not hold. The students recently got the dream “up” of a lifetime when they and their experiments were selected for testing on NASA’s KC-135 Reduced Gravity Student Flight Opportunities Program (RGSFOP), and the zero-G experience lifted them high enough that most won’t come down for years.

In the heyday of the “Space Race,” dedicated and enthusiastic satellite builders and spacecraft design big thinkers were virtually a dime a dozen. The real task was in choosing the brightest and the best from a limitless pool of self-selecting top talent. More recently, recruiters and human resources pros will tell you, it’s been a scramble just to keep the pipeline filled.

But this threatened dearth of future space age worker bees was not in evidence during a recent 10-day stretch at the Johnson Space Center near Houston, TX. Joining the Purdue University contingent was a new generation of potential satellite and space professionals from a dozen colleges including Alfred, California Polytechnic, North Carolina State, Penn State, and others. The student teams were selected after a rigorous series of tests and evaluations of experiments that were months if not years in the making. Proposals ranged from gauging the effects of weightlessness on human organs to using virtual reality set-ups as zero-G training tools.

College teams have the option of inviting a “flight-team journalist” to help document the most exciting part of their experiment. Everyone unanimously agreed that that part is the zero-G flight itself, with NASA’s special KC-135, dubbed “Weightless Wonder V,” making 30 zero-G parabolas on a standard test mission, one lunar-G and one Martian-G arc. Total time of weightlessness for a typical RGSFOP flight is about 13-15 minutes, with each parabola providing 25-30 seconds of glorious freedom from Earth’s insistent pull.

Purdue Teams Focus On Satellite Technology

Three of four Purdue teams participating in the spring 2001 semester offered a spectrum of different approaches to serious problems encountered by commercial spacecraft in orbit.

One team experiment focused on weight reduction in propellant management vanes. These vanes, situated in the hydrazine fuel tanks typically used to position and move geostationary communications satellites and other spacecraft, keep the liquid propellant in a relatively stable state and help wick the fuel toward the tank outlet valves. Students proposed, built and then tested modified vanes that were designed to reduce overall weight. Another Purdue student test also targeted satellite fuel tanks, with a second team seeking ways to improve mass center control. The goal of this experiment attempted “to identify new technologies that will enable exact positioning of the fuel mass center by better controlling the ullage bubble.” The ullage bubble, is, according to Webster’s, “the amount that a container lacks being full.” Permutations in the weight of a satellite, the students postulated, can cause difficulties with wobbling in orbit and other stationkeeping management concerns.

A third Purdue team tackled the “experimental development of hydrazine fuel line gas arrestors.” In this experiment, students devised four mechanical schemes to trap gas bubbles that sometimes form while in orbit in the fuel lines of hydrazine arc-jet thrusters. These bubbles can increase electrode erosion and may disrupt the anticipated force of a thruster burst, thus complicating in-orbit maneuvers and stationkeeping.

In fact, according to team member Melanie Silosky, “the data gained from the proposed research could have a tremendous impact on future satellite design. Better dynamic modeling of satellites has positive impacts on guidance and controls, reaction wheel sizing, satellite failure rates, and fuel consumption.” With a typical direct broadcast satellite carrying somewhere in the neighborhood of 200 gallons of fuel, and a burn rate of about a gallon a month, any fuel management scheme that can either prolong the life of the spacecraft or improve its operational efficiency is money in the bank.

Along with support from Purdue, and from university Professor Steven Collicott, students participating in the 2001 RGSFOP also teamed with researchers and scientists from Lockheed Martin Missiles and Space Co.

Up Over The Gulf Of Mexico

The fun begins when the work is done.

On a gray, cloudy day at JSC, students, faculty advisors, and flight-team journalists assembled at dawn to test the fruits of a semester’s labors. Individual experiments had been loaded onto Weightless Wonder V the day before. Pre-flight checkout consisted of various tweaks to ensure that video cameras were in place and working, that needed tools and other equipment had been stowed, and that everything was locked down to the floor of the aircraft.

Rollout and takeoff were uneventful and, above the clouds, the sun shone brilliantly. Reaching cruising altitude, the lead test director, NASA’s John Yaniec, gave the word that student teams could make their final preparations for weightlessness. And then, suddenly, the KC-135 rolled up at 26,000 feet into a 45-degree angle climb, bleeding airspeed as it approached 34,000 feet. At the apex of the climb, seconds before the nose keeled over, Yaniec screamed out, “Over the top! Here we go!” The next few moments were pandemonium as students felt the floor fall away and they started drifting for the first time in a flying zero-G rubber room the size of a four-car garage.

Never has 30 seconds passed so quickly. Almost as soon as it began, Yaniec was shouting, “Feet down! Two seconds!” And, as abruptly as weightless had uplifted us and set us free, the crushing force of double gravity 2Gs pressed everyone to the floor as Weightless Wonder V came out of the dive and headed back up on the ascent. Within just a few minutes, the sequence was repeated. It took just two or three parabolas for most of the students to settle down to their experiments, gauges, and camcorders. And that’s all it took for a few unfortunates to find out definitively that weightlessness doesn’t agree with everybody. Out came the barf bags, and the most severe cases were seated, buckled down and covered with blankets to weather the next 25 or 30 loops as best they could.

Meanwhile, student teams put their experiments through their paces, the entire proceedings documented for all time by two NASA videographers and an agency still photographer. As a final finesse, the NASA pilots treated all passengers to two special parabolas. One simulated the gravity of the moon (about one-sixth of Earth’s) and another that of Mars (about one-half). People danced and leapt, with the more imaginative dreaming of the potential for a visit to long-abandoned lunar outposts.

We were back on the ground just two-and-a-half hours after liftoff.

What The Future Holds

Purdue University is the self-proclaimed “cradle of astronauts,” with good reason. Nearly two dozen graduates have participated in missions from the Mercury program (Virgil “Gus” Grissom) to the moon shots (the first on the moon, Neil Armstrong, and the last, Eugene Cernan), to the shuttle program. Today Purdue’s School of Aeronautical and Astronautical Engineering gets far more applicants to its RGSFOP class than it can handle. For the lucky few that make the cut, the payoffs go far beyond a letter grade.

“Our experiment on weight reduction performed according to our expectations, but it will take some time to fully understand and analyze the data that we captured,” says team member Adam Butt. Adds team member Paul Brower, “Every pound of material launched into orbit costs the satellite owner at least $10,000, and every month of extended lifetime is worth thousands in added revenues. The Purdue tests could end up being worth millions to satellite operators.”

The final outcome of student experiments created for and demonstrated during the 2001 RGSFOP won’t be known for months, perhaps years. But one thing is certain: The months of study, of building and testing on-ground prototypes, of managing and then passing the arduous NASA experiment selection process and pre-flight training regimen pays off each year for dozens of lucky college attendees and a handful of honor high schoolers.

“Zero-G was awesome. There’s nothing like it anywhere else,” says Butt. “You simply can’t get experience like this in the classroom.” And that’s the point of NASA’s Reduced Gravity Student Flight Opportunities Program at Johnson Space Center. Inspire a student today, and tomorrow the satellite and space industry worldwide will continue to grow, innovate, prosper and succeed.

Scott Chase is the president and CEO of The Strategis Group, a telecom market research and consulting firm based in Washington, D.C., with offices in London, Singapore, and Sao Paulo, Brazil.


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