Superpressure Balloons Reach New Heights

Balloons originally designed to drift in the Earth's upper atmosphere for months may visit Martian skies in the next few years. Though they were first designed in the late 1700s, balloons may turn out to be a key technology for extraterrestrial exploration. Researchers at NASA's Goddard Space Flight Center, Greenbelt, Md., are developing unmanned balloons that withstand the harsh environment of earth's uppermost atmosphere and whose next mission may be on Mars. Their current task is to investigate gamma particles that could give clues to the origin of the universe. These "superpressure" balloons are sealed and made from material that can hold up under dramatic pressure and volume changes caused by the sun heating the gas. This technology is being applied to aerobots, self-deploying and inflating balloons that could float through the Martian atmosphere, taking pictures and dropping probes. The first mission is scheduled for December with a payload that tracks cosmic rays. Balloons as a means of transport compare favorably to rockets in a couple of important ways. For instance, balloons can lift payloads without the vibration and -forces of rocket launches, and often their payload is recoverable. A conventional balloon will stay afloat for one to two days, but the pressurized, pumpkin-shaped balloon on which NASA is working should be able to fly longer. The design goal, says NASA, is to support a 2,200-lb scientific payload and deliver 800 W of continuous power to it for 100 twelve-hour days. The balloon payload collects solar energy with three solar panels and stores power in nickel-metal hydride batteries. Scientists will be able to command instruments and read scientific data back on Earth via the Internet. The telemetry design may use a commercial satellite network as well as TDRSS, the satellite on which the space shuttle relies for communications. The pumpkin-shaped design