Friday, April 30, 2004

High Altitude Surveillance Aircraft

What if you had an aircraft that flew at 100,000 foot altitude and could stay aloft for months at a time? Unmanned of course. What could you do with it?

Several aircraft designs of this sort are being developed right now.

The projected uses include

  • Weather tracking
  • Telecommunications
  • Spying, "Homeland defense", and other military uses

At 100,000 feet altitude the aircraft is in a "near space" environment, and in fact humans are considered to be "astronauts" if they have flown above the 100,000 foot altitude. An aircraft at that altitude would essentially be a geostationary satellite, launched far more cheaply than a satellite, and retrievable or deployable at will.

How would this look? Try this cheesy diagram on for size.

The red dots are some kind of high altitude aircraft. At 100,000 feet they're well above the regular air traffic (35-40,000 foot ceiling) and well above the weather. There is a lot of wind, and they will need propulsion of some kind to keep them in place. The mission they perform is limited and determined by the equipment mounted on the aircraft. Want a surveillance vehicle? Mount cameras and point-point communications gear, for example.

The green and pink dots are the current sort of satellites. They are launched with rockets or the space shuttle, and fly either close to the earth or in distant geostationary orbits. The low orbit satellites move around the planet constantly, while the geostationary ones stay fixed over a single location. The geostationary satellites are at a high enough altitude that there is a significant time lag on communications relayed through the satellite.

The lines in the drawing show a potential communications network built using satellites and high altitude aircraft. This may not be a feasible design. What's obvious is that the high altitude aircraft can effectively serve as a communications link over a local area more readily than satellites. To communicate through a satellite requires careful aiming of a satellite dish antenna, and a strong enough signal to reach the geostationary satellite. Which just makes the equipment bulky and difficult to set up. Communicating through high altitude aircraft would be just like cell phone systems of today, with relatively low power transmissions and no need to aim a dish antenna.

In use as a surveillance mode, high altitude aircraft are are a much lower altitude than any satellite. This means the pictures are much clearer with these vehicles than from satellite, hence easier to interpret.

An interesting factoid. Tech Sphere Systems (see chart below) says that at 20 km altitude (65000 feet) communications gear have a 73000 square mile coverage radius. That's equal to the land area of Virginia, Maryland, Washington DC and West Virginia.

OrganizationWeb siteDiscussion
Tech Sphere Systemshttp://www.techspheresystems.com/index.htmlA spherical baloon with "thrusters" that let it move about in any direction it desires. The company discusses mosly missions related to military use.
Proxity Digital Systemshttp://www.proxity.com/Developer of communications gear and other security related technology. In partnership with Tech Sphere Systems.
New Mexico State University's Physical Science Laboratoryhttp://www.spaceref.com/news/viewpr.html?pid=8091

http://www.psl.nmsu.edu/

http://www.psl.nmsu.edu/aas/

University laboratory with many projects under development. Many of these have to do with high altitude aircraft designs for the Military.
Aerovironment & Sky Tower GlobalAerovironment and http://www.skytowerglobal.com/Aerovironment is a high-technogy R&D corporation that has developed many interesting products (such as GM's EV-1).

The Helios aircraft is merely the latest. It is a flying wing containing several propellers powered by electric motors. The aircraft uses solar panels and fuel cells to create a vehicle that can stay aloft for 6 months at a time without refueling.

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