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For use with Chapter 13
States of Matter

NASA's New Technology Is Full of Hot Air
Posted December 1, 1999

In recent years, NASA has faced major budget cuts. This has caused NASA researchers to develop more efficient projects and technology. One famous example of such efficiency is the Mars Pathfinder, a mission to the Red Planet launched several years ago, that cost only a fraction of what originally was planned.

NASA is now working on perfecting a new spacecraft. It's not a state-of-the-art rocket ship, nor is it a top-secret satellite. In fact, the technology for this new type of spacecraft is based on the oldest type of flying craft-the balloon. Balloons are relatively inexpensive to launch into our atmosphere, and they can stay aloft for up to 100 days. In addition, their parts can be recycled for further missions.

Balloons are more efficient than other inner-atmosphere probes, such as a robotic plane, because they use buoyant forces to lift them into the air. Inner-atmosphere probes use massive amounts of fuel to move about, as well as maintain a certain altitude. Balloons do not have this difficulty. They stay aloft because the weight of the gases and equipment is lighter than the weight of the gas they displace. Balloons can move about and maintain altitude by just adjusting the heat of the gas inside the balloon, much like a hot-air balloon, or by adjusting the amount of gas inside the balloon. Hence, the only fuel needed is what is required to heat the gas.

Balloons have already been placed into atmospheres of other planets. In 1985, the former Soviet Union, in cooperation with France and the United States, sent two balloons into the atmosphere of Venus. Rockets launched from Earth carried capsules to Venus, which then inflated the balloons in the planet's atmosphere. The sensors carried by the balloon made detailed measurements of the winds on Venus.

Scientists are faced with the challenge of keeping a balloon in flight for an extended period of time. In December 2001, NASA Goddard Space Flight Center will launch the Ultra-Long Duration Balloon (ULDB) into Earth's atmosphere, where it will glide for several months at an altitude four times higher than that of passenger jets. In order to meet this altitude and duration of flight, NASA has had to redesign the shape and the material of a traditional balloon.

Traditional balloons had a spherical shape and were made of light, yet strong, material. But when a balloon flies at high altitudes, the balloon will expand as it rises, which places stress on the circumference of the balloon. The instruments hanging below the balloon add additional stress. NASA has been able to circumvent this problem by switching to a pumpkin-shaped balloon. The stress in a pumpkin-shaped balloon occurs more along the seams of the segments, which can be reinforced. This then reduces the strength requirement of the balloon material. Despite this reduction, to meet the strength requirement in this high-altitude project, the material must be stronger than a traditional balloon and must not allow as much gas to diffuse out, since the loss of gas prevents a longer flight. To meet these requirements, NASA has chosen to use a composite material, with three different layers—a polyester fabric, a polyester film, and a polyethylene film.

In the future, NASA hopes to use the advances in current balloon projects, such as the ULDB, to send balloons into the atmospheres of other planets, including Venus, Mars, Jupiter, Saturn, Uranus, Neptune, and Titan, a moon of Saturn.

Activity
Use the Internet to learn more about the ULDB projects and other balloons. Write an entry in your Science Journal explaining how different types of balloons function and use buoyant forces.

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