High altitude platforms

High altitude platforms (HAP) are an alternative to terrestrial wireless links. A HAP would hover between 17 and 22 km above the ground, out of the way of aircraft. Cost, maintenance and latency would be better than with a geostationary satellite, but a HAP must be kept in a fixed position and orientation. A HAP could have optical or radio links to other HAPs or to satellites in addition to communicating with ground stations.

Research and development on HAPs is being conducted in Europe, the U.S. and Japan. People are testing balloons, airships, planes, and tethered aerostats. If you are thinking "Hindenberg," bear in mind that new envelope materials that are strong, UV–resistant and leakproof are available today.

No HAPs are currently in use, but the Sanswire Networks HAP shown here has been tested and a joint venture signed to deploy five platforms in Colombia. It has the following characteristics:
  • 245 x 145 x 87 feet
  • Proprietary lifting gas technology
  • Outer envelope covered in film solar panels
  • Solar powered electric motors
  • Held in position using 6 onboard GPS units
  • Desired altitude: 65,000 feet
  • Line-of-sight to a 300,000 square mile area
  • Controlled by earth stations on the ground
  • Flight time: 18 months

For more on HAPs, see this article by T.C. Tozer and D. Grace.

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