They float through the air with the greatest of ease

I am strapped to a chair in the cockpit of NASA's KC-135A, the agency's fabled microgravity research and training aircraft, whose nicknames range from Weightless Wonder to Vomit Comet.

As the plane takes a dive at 34,000 feet over the Gulf of Mexico, the ocean comes rushing toward my face. Seconds later, the aircraft climbs steeply and then arches over the top of its parabolic flight path, creating the desired 25-second snippet of reduced gravity.

Held by our restraints, neither the pilots nor I float freely. But the main cabin has a confusion of body parts tossing about in every direction, screams of surprise reaching us in full force.

No matter how many times you fly the KC-135A, those first seconds of microgravity hit the senses. But when it is your first time and you are an excited student seated by your experiment box, these precious moments also mean the culmination of years of preparations, proposals, exams, tests, and mixed emotions.

Though it is widely known for its role in NASA's personnel training – every astronaut gets a first taste of weightlessness here – 80 percent of KC-135A flights are devoted to research. This is the only way scientists can observe the behavior of materials, objects, phenomena, and even plants, animals and people, destined for space. Free from gravity, the aircraft becomes a laboratory to look at things with new eyes.

An equally important role of the "K-bird," based at Houston's Ellington Field, is to serve as a testbed for groups of college and university students, who design and build their own science experiments and compete to bring them on board. Swept off their feet by science, these students aspire to become NASA's future engineers and astronauts.

"I can't believe I am floating here!" yells Drexel University's Mary Sullivan as she hovers above a box containing a diesel flame inside a steel cylinder. "I always knew I wanted to be an astronaut. But now I am determined to become one."

Ms. Sullivan is a chemical engineering major, and her team wants to collect soot particles to study the combustion in microgravity of bio-diesel – a mixture of soy fuel and diesel. "Learning how the soot forms, its size and shape, can give us valuable information to be applied in designing safer engines in the future," she says excitedly.

In spite of the enthusiasm of students like her – 110 colleges in 44 states have flown since the program began in 1995 – budget restraints last year made the future of the Reduced Gravity Flight Opportunities Program for Students uncertain. The cost of each flight hour is about $11,000 for crew, maintenance, and fuel.

Yet NASA officials made clear they think it is important enough to be kept alive.

"NASA is proud to support microgravity research opportunities for students," says Scott Pace, NASA's deputy chief of staff, who flew in from Washington D.C., to evaluate the program. "We will continue to fund it one way or another because it promotes good work and dedication. Students learn leadership, science and engineering skills, and also, professionalism."

For Caltech's Cristina Thomas, whose team and project came close to falling apart, the experience was a valuable course in managerial skills. "It taught me not to give up," she says.

Caltech's project had to do with measuring the speed of sound as it traveled through a mixture of water and air bubbles. The experiment needed to be done in microgravity to prevent the air bubbles from migrating toward the top of the box.

"Though this is basic science, it does have interesting applications in sonar technologies, because boat and submarine engines create bubbles as they move through the water," says Ms. Thomas.

Throughout the years, the KC-135A team has seen student experiments of virtually all sciences. "We have had life sciences, chemistry, engineering, astronautics, you name it," says Donn Sickorez, university affairs officer. There was even a study on body painting, as a proposed way for astronauts to play during their spare time in orbit.

The complexities of parabolic flight and NASA's concern for safety mean every person on board must first pass a physical and be trained in a decompression chamber to experience what it's like at the oxygen-starved equivalent of 25,000 feet. And of course, there is "the vomit thing."

"One hour prior to boarding, they gave us a very powerful anti-nausea medication," says Drexel's Brian di Paolo. "I did not get sick at all, in part because I did not move my head too suddenly during the high-G pullout periods, when the aircraft is climbing onto the next parabola, and the inner ear is at its most sensitive."

Paying attention to what the crew says can also mean the difference between having a blast and having a tough time on a flight that performs 30 to 40 parabolas nonstop.

For students, the rewards of the trip are worth the unusual challenges it presents.

"This is one of the greatest student programs I've ever encountered," Thomas says. "I've learned so much about so many things, not just science. Microgravity changes a variable that on the ground is always constant. If we have the opportunity to lift it, even if for just a few seconds, there is no end to what we can discover."