A balloon taller than a 30-story building and wider than 100 yards will be built by NASA to carry astronomy instruments to near the edge of space.
The balloon will carry more weight higher and fly longer than any other scientific balloon ever, said Jack Tueller, a Goddard Space Flight Center astrophysicists and chief project scientist for the Ultra Long Duration Balloon Project.
The balloon would lift about 3,000 pounds more than 22 miles high and would stay aloft for 100 days, long enough to circle the globe about five times if the winds are right.
And the balloon will conduct astronomy experiments for about a million dollars, much less than the cheapest of NASA’s rocket launches, the Pegasus, which costs $15 million to $18 million, Tueller said.
He said the scientific capabilities of the superballoon and the Pegasus are “roughly comparable.”
“The Pegasus can launch a payload that will stay up for a couple of years, but it is only 500 pounds,” he said. “The balloon would carry about 3,000 pounds, but it will stay up only about 100 days.”
Another advantage for the balloon, said Tueller, is that instruments can be recovered and flown again, time after time. Instruments on rocket-launched satellites are rarely recovered.
“If you fly a payload (on a balloon) and its doesn’t work, then you just recover the payload, fix it and fly it again,” he said. This is impractical on a satellite.
The planned balloon would be made of a combination of a high tech fabric and an aluminized polymer material, such as Mylar.
“They have flown flights with small Mylar balloons that lasted for more than 100 days, so we know the material is good for that,” he said.
Tueller said the balloon would be partially inflated with helium on the ground, pumping in just enough of the light gas to ascend. As the balloon rises, the air pressure declines and the helium would expand until the balloon becomes a spherical shape some 328 feet in diameter. Altitude would be controlled by a combination of gas venting and heating from the sun.
A test flight planned for next summer will determine how much pressure the balloon can withstand. A test balloon, carrying a dummy payload, will be sent aloft and then inflated to the point of failure, said Tueller, “so we will know at what pressure it popped.” This flight will be from Fort Sumner, N.M.
Six payloads, proposed by various universities, are being considered, including instruments that would study gamma rays, cosmic rays or cosmic microwaves are being considered. Tueller said the instruments would gather data that is not now being collected by NASA’s fleet of scientific satellites.
Data collected by the balloon instruments would be radioed to a NASA satellite and then relayed to the ground.