Aerial Delivery - PMA

Parachute retraction soft landing has been the subject of study at the Army’s Mobility Directorate, Natick Soldier RD&E Center, where both analysis and actual demonstrations have shown the potential of this concept. Soft landing of wheeled vehicles—such as the High-Mobility Multi-Purpose Wheeled Vehicle (HMMWV)—has high potential payoff, including the elimination of paper honeycomb and the ability to immediately drive the vehicle.

HDT’s flexible composite AirBeam™ technology makes compact and highly efficient long-stroke actuators for parachute retraction possible. These actuators are slender flexible tubes with means for mechanical attachment on each end and a pneumatic fitting at one end. Prior to pressurization, the actuator is flexible and can be packed for deployment with the parachute. When pressure is applied through the end fitting, the actuator contracts strongly, providing a force useful for a variety of applications. The name "Pneumatic Muscle Actuator"(PMA) is descriptive of this device.

One of the most striking characteristics of the PMA is that the initial tension provided is 25 or more times the force of a pneumatic cylinder of the same diameter.Other characteristics include the fact that it is extremely lightweight and has the ability to be packed into a small volume prior to inflation. These attributes are highly suggestive of recovery systems applications.

System Description

The soft landing airdrop system consists of the payload, the parachute and the retraction device. The retraction device consists of a braided fiber tube, a gas barrier liner, one end closure with a mechanical load attachment and one end with a mechanical load attachment, a pyrotechnic gas generator and a ground-proximity sensing initiator. A PMA with an active length of 28 feet has been shown to reduce the impact velocity of a 15,000-pound payload descending under a cluster of four 100-foot diameter G-11 cargo parachutes from 24 feet per second (16 miles per hour) to a gentle 8 feet per second (5½ miles per hour) in just a half second.