Robot parachutists hit the mark

Two US Marine Corps' skydivers made their first combat zone landing in earlier this year at a little-known and remote US army camp in Iraq's Al Anbar Province. The landings were significant enough to go down in history but there was little fanfare at the time as the aim of the exercise was to supply remote troops with the things they needed in a combat situation – the Sherpas each rode a pallet of rations to the drop zone, controlling their chute from two miles high to within 200 metres of their target.

The Sherpa is an intelligent robot that uses a Global Positioning System to steer the rectangular, 900-square-foot parachute by motor-tugged lines. The Sherpas belong to the 1st Air Delivery Platoon, part of Combat Service Support Battalion 7, 1st Force Service Support Group, which delivers supplies to Marine units throughout the vast western portion of Iraq's Al Anbar Province.

GPS-guided parachutes like the Sherpa eliminate numerous disadvantages of air dropping supplies to far-flung troops in that it can be steered, unlike a round parachute. It also incorporates a small drogue parachute to help stabilize the cargo pallet, keeping it facing upward so the main chute opens properly after freefalling.

While in flight, the Sherpa constantly checks its position using a GPS receiver, and makes flight adjustments as necessary, pulling on two steering lines to turn the parachute.

Before any mission, the aircraft's altitude and speed, the cargo's weight, the drop zone location and wind speeds for various heights must be programmed into the Sherpa's control unit so it can calculate a flight plan, said Gunnery Sgt. Lorrin K. Bush (no relation), 35, head of the air delivery platoon. It can even be programmed to maneuver around obstacles or locations where enemy forces are located.

In response, the Sherpa calculates the precise point in the sky where the cargo must be dropped. As a result, the riggers are taking on more responsibility since they can now plan part of the flight's path. Previously, this task fell upon the plane's navigator.

"We give them the mission and say "Fly this,'" Bush said. "They're not used to hearing that from us."

Currently, cargo is dropped via "dumb" parachutes, which have varying accuracy depending on the altitude of the aircraft and wind conditions during the drop, said Pack. Low-altitude drops, classified as anything under 2,000 feet, are fairly accurate, but put the plane and its crew in range of crippling enemy fire.

"The GPS-guided chute gives us more flexibility dropping the load," said Edmonds, Wash., native Capt. Robert D. Hornick, 28, a KC-130 cargo plane co-pilot from Marine Aerial Refueler Transport Squadron 352, the unit that flew the mission. "We just get close to the 'DZ' and drop it and it does the rest."

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