New Drone Spies Combat Targets from the Stratosphere
Aerial
drones have garnered a lot of attention (and controversy) for their ability to launch
missile strikes for the U.S. military against enemies in Afghanistan, Pakistan and other
hotspots. However, the Department of Defense is now cultivating another type of unmanned
aerial vehicle (UAV) for use in combat planning, designed to soar high above the
battlefield for so-called ISR (intelligence gathering, surveillance and reconnaissance)
missions.
The STS-111 aircraft, which is still in prototype, is in essence a worm-like weather balloon that
undulates through the Earth's lower atmosphere, guided by satellite or ground
communications or programmed to operate autonomously. "It's really a communications
platform that has the ability to provide ISR," says Dan Erdberg, vice president of
operations for Sanswire Corp. in Aventura, Fla. Sanswire and Stuttgart, Germany-based TAO
Technologies formed a new entity called Sanswire-TAO in June 2008
specifically to develop, market and sell a lineup of ISR UAVs (the STS-111 being their
first).
The 33.8-meter long STS-111 is made up of four segments that form what Erdberg refers to
as an "airchain" platform. The first segment consists of a bullet-shaped balloon
filled with helium, making it lighter than air. The remaining three segments (connected by
hinges) house a single, elongated balloon filled with a gaseous fuel made of mostly
methane, making it neutrally buoyant (the balloon's mass equals the mass of the air it
displaces).
All four segments are contained within a large vented bag that
helps the segments move by allowing air to flow in and out. As the aircraft takes off, the
gas in each of the balloons expands, forcing air out of the outer bag. At the same time a
blower attached under the first segment sends air back into the outer bag. This constant
flow of air into and out of the bag creates the motion that helps the STS-111 gain
altitude. A small propeller affixed to the underside of the first segment provides thrust
and steering.
When fully inflated the STS-111's widest point is 3.4 meters, and it can carry a payload
(cameras and sensors, for example) of up to 9.1 kilograms over a distance of 2,800
kilometers. The aircraft is designed to carry out its missions at altitudes between 3,048
to 9,144 meters.
The Sanswire-TAO aircraft is different from other military drones in several ways, but the
two most important are cost and flight duration. Whereas the STS-111 costs about $3
million to make, the Air Force's new "Gorgon
Stare" UAV, essentially a Reaper
drone fitted with wide-area surveillance sensors, costs about $15 million. And, while
a fully loaded Reaper can stay in the air for a maximum of 14 hours, the STS-111 is
designed to monitor enemy targets for up to two-and-a-half days before returning to base.
(12.31.2009, Larry
Greenemeier) http://www.scientificamerican.com/article.cfm?id=uav-drone-stratosphere
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