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Huge balloon proposed to launch astronomy instruments
December 22, 1997
Web posted at: 8:37 p.m. EST (0137 GMT)WASHINGTON (AP) -- 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 $1 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."
Instruments could be reused
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.
Test balloon will be popped
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, New Mexico.
Six payloads, proposed by various universities, are being considered, including instruments that would study gamma rays, cosmic rays or cosmic microwaves. 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. The researchers also are considering the use of cellular phone technology, using commercial communications satellites to allow, in effect, the balloon to call home from any place during its flight.
Tueller said the superballoon would be launched from Australia or New Zealand. This would keep the balloon in the southern hemisphere, where it would spend most of its time over ocean waters.
"If you go north of the equator, you might fly over places like Libya, Iraq and Iran and that would not be good," said Tueller. Those countries have a history of denying scientific overflights.
Little control over balloon's path
The balloon mission is expected to be ready by 2000, with launch during January or June, when the high altitude winds are at their peak over Australia and New Zealand.
Tueller said there is little control over where the balloon goes, although it is expected to stay at about the same latitude of its launch.
When it is time to end the mission, NASA scientists would send a signal that would release the instrument package for a parachute drop to the Earth. The same signal would collapse the balloon and it would fall separately.
Tueller said the plan calls for the balloon to be brought down either over Australia or South America. He said there are international agreements in place that would permit both the launch and landing of the balloon.
The whole project, including development of the reusable instruments, he said, should cost about $10 million. Compared to the cost of NASA's typical rocket and spacecraft missions, said Tueller, that's a bargain.
Copyright 1997 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.
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