UAV Can Deliver The Goods On Its Own

Precision-guided munitions have successfully pinpointed aerial bombings for years. Now, the same idea is being researched for airdropping supplies and equipment. One system identified and tested by the Airdrop Technology Team at the US Army Soldier Systems Center here could soon vastly improve the way the military drops extra-light loads of supplies.

The Sherpa Autonomous Parafoil Delivery System developed by Mist Mobility Integrated Systems Technology (MMIST) Inc. in Ontario, Canada, is a commercial off-the-shelf item that enables service members on land to get what they need almost exactly where they want it.

"When you drop a dumb parachute system from high altitudes, it can drift away and you may not find it quickly," said Jaclyn McHugh, project officer for the Sherpa. "The Special Forces say this system is amazing. They've had to hike between 1-3 kilometers to find their supplies with current airdrop systems."

The Sherpa, a mature product, is one of many "just-in-time" resupply systems in its payload-weight class of the Airdrop Technology Team's Precision Extended Glide Airdrop Systems (PEGASYS) Demonstration, according to Richard Benney, Airdrop Technology Team leader.

With the Sherpa, transport aircraft or helicopters at altitudes of 5,000-25,000 feet and as far as 9 miles away can dispatch supply pallets weighing 400-1,200 pounds to within 200 meters of the target location.

To get close to this accuracy, Benney said current airdrop systems with round parachutes are pushed out at altitudes under 1,000 feet, which exposes aircraft to enemy fire and minimizes stealth.

In more than 30 drops in testing, the Sherpa has been effective and reliable. It was most recently successfully demonstrated to soldiers at Fort Polk (LA) in February.

The Sherpa flies autonomously with a Global Positioning System (GPS), by remote control, guided by a beacon or by a combination of the methods.

For autonomous flight, an operator enters critical information, such as altitude, mass, wind and target point, into a computer and downloads it into the Sherpa's parachute control unit before pushing out the cargo.

Once out of the aircraft, a parafoil opens and servo-actuators in the control unit steer the load left or right by pulling down the parafoil's trailing edges as the Sherpa's GPS receiver determines the coordinates of its own position from the parameters entered into the system. The system guides itself to within 100 meters of the target coordinates.

"If it goes too far, it'll just turn around and fly to the location," McHugh said. "The system's simple to learn and easy to operate."

When directed manually by a trained operator on the ground or in the air, landing accuracy for remote control is limited only by the operator's skill. A manual remote override capability enables users to switch between remote control and autonomous flight.

By activating a beacon transmitter on the target site, the Sherpa can also be programmed to home in and land within 200 meters of the signal.

As it approaches the target, the Sherpa lands in any of three modes.

At 4,500 feet, the cargo follows an 80-meter-radius circle around the target in the spiral mode by pulling on the steering line with each pass to create a tighter turn radius until landing. The direct landing is used for high accuracy. However, the load can hit the ground hard because it can land in the same direction as the wind and does not flare, which is the rapid slowdown from retracting both sides of the parafoil.

When accuracy is less important, the Sherpa in the approach mode follows the same 80-meter circle but turns into the wind to lower its speed for a softer landing, which is important for more sensitive items, such as medical supplies, according to McHugh.

The remote control mode has benefits over both spiral and approach modes. "Using the remote control is an advantage with the direct landing because the operator can flare the parafoil for a softer landing," McHugh said.

Once on the ground, the Sherpa can be recovered during de-rigging for further drops.

Limited fielding of the item to Army units is going to depend on how well the capabilities of the current Sherpa match their needs, according to Benney.

FMI: http://www.natick.army.mil