Shimmering as it swayed in the orbital sunlight 176 miles above Earth, an inflatable antenna swelled to the size of a tennis court and flew alongside space shuttle Endeavour on Monday.
“Pretty fantastic,” said shuttle commander John Casper.
The experimental, silver-colored antenna appeared to expand to its full size after being released by the Endeavour astronauts - nearly 50 feet in diameter, supported by three inflatable struts 92 feet long. Depending on your point of view, it looked like a flat parachute or a round trampoline on an upside-down tripod.
Then, after more than an hour’s worth of measurements, the antenna was cut loose from its orbiting platform. The antenna was expected to plunge through the atmosphere and burn up Tuesday.
“We really think we took a giant step,” said project manager Steven Bard of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “We really showed that you can inflate such a large structure like this.”
NASA is interested in inflatable antennas, sun shades and other space structures because they are lighter and less expensive than traditional mechanical systems. They also would be more reliable because of fewer moving parts.
Even if punctured by micrometeorites, the thin Mylar foil, similar to what’s used in birthday balloons, would hold its shape because of the low pressure and small amount of gas needed for inflation, officials said.
There were a few surprises in Monday’s experiment: The antenna rotated more than expected and even began to tumble, and had noticeable rippling across its surface.
Concerned about the tumbling, Mission Control told the astronauts to back away from the antenna a little sooner than planned. The crew had been observing the antenna from a distance of 400 feet.
Whether the antenna inflated properly will not be known for certain until Endeavour returns to Earth next week with all the data collected.
“But I’d say even in the worst case from what we’ve seen, it was very close to a full success,” Bard said.
Endeavour’s six-man crew had no problem deploying the antenna, which was folded into a box the size of a kitchen table. As soon as the doors on the box opened, nitrogen gas began filling the antenna and it popped out in one big jumbled mass.
The three narrow, accordionlike struts inflated first, followed by the sphere. With its spindly legs, it looked like a huge grasshopper as it unfurled.