NASA announced yesterday that its Balloon Program Office had ended the second test flight of its Super Pressure Balloon, or SPB. The balloon took off from New Zealand on May 16th and landed in Peru yesterday. It circumnavigated the earth during its first 14 days aloft, and flew for a total of 46 days, 20 hours, and 19 minutes. That’s short of the project’s goal of keeping a balloon a loft for 100 days or more, but it is still a record-length flight for a balloon of this type.
That type is: very, very large. The Super Pressure Balloon has a total volume of 18.8 million cubic feet, and measures 114 meters in diameter. It’s engineered to fly at 110,000 feet, or about 21 miles, above the earth’s surface. That’s just about the height of the Earth’s ozone layer.
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The balloon is innovative because it uses pressurized helium to float (hence the name). That’s intended to help it overcome the cyclical rise and fall in altitude that conventional balloons experience when the sun warms them. According to Science, that expansion also causes leaks, limiting their lifespan in warmer weather.
The current mission ended because the balloon was beginning to lose altitude during cold periods. Program officials say they still need to determine why.
Long-lived, high-altitude balloons have the potential to be a lower-cost alternative to satellites. As proof of that concept, this SPB test carried a spectrometer searching for Gamma rays, and a package of microphones listening to low-frequency sound. Those sounds, which can be heard more easily from the sky than from earth’s surface, could help scientists monitor everything from ocean currents to volcanoes and earthquakes.
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The ability to put long-lived balloons into the upper atmosphere could have an impact on the commercial space market. Though most of the customers for companies like SpaceX are launching heavy commercial satellites, some satellite functions could eventually be taken over by balloons. The most high-profile preview of this is Google’s (GOOG) Project Loon, which is working to provide Internet service to remote areas using balloons.