To astronomers and earth scientists, balloons aren't toys; they're serious tools that allow a good view without the cost of launching a satellite. But in flight, research balloons must vent helium each time they are heated by the midday sun. They also bob up and down annoyingly and stay aloft no more than a week or two. So NASA engineers have created a pumpkin-shaped floater that can hang steadily at 115,000 feet and stay there for 100 days.
The ultra-long-duration balloon is made of a lightweight three-ply polymer, about as thick as plastic food wrap. The polymer can withstand high pressures as the balloon heats and cools over the course of a day, so it can stay completely sealed. No gas escapes. Fiber tendons, which form the lobes of the pumpkin, bear the weight of the payload and eliminate strain on the thin skin.
In a test run last June, a scaled-down pumpkin balloon flew for 30 hours without losing gas or altitude. The full-sized version, now under construction, will be the size of a football stadium and able to haul 3,500 pounds of payload— including, perhaps, telescopes to rival the Hubble Space Telescope. Its test flight is set for January 2001.
Photo by Steve Smith/NASA