Engineers and technicians from NAWCWD China Lake and the Jet Propulsion Laboratory (JPL) in Pasadena, Calif. recently conducted the first demonstration of a new method of performing load tests on large parachutes.
Historically, parachutes have been load-tested by various methods including release from an aircraft, deploying in a wind tunnel, dragging through water, and shooting out of an air cannon. Each type of testing has its own advantages and drawbacks. JPL conducted a review of all of the available test methods and, due to the loading mechanics peculiar to parachutes deploying in a very thin atmosphere, decided that none were appropriate for testing the next generation of Mars lander parachutes.
Having had recent experience with NAWCWD’s Supersonic Naval Ordnance Research Track (SNORT) for the supersonic inflatable aerodynamic decelerator (SIAD) test series, they decided on a new approach to parachute testing. A helicopter would lift the parachute into the sky with a rope trailing down to a pulley on the ground. The rope would go through the pulley and attach to a rocket sled. The parachute would be released and inflate as it dropped to the ground. Once the parachute was fully inflated, the rockets would be fired and the sled would tow the parachute down towards the ground. This would impart the desired loads to the parachute in the fully-open shape it would take above Mars, verifying its design.
During the course of two years, China Lake and JPL engineers refined the Parachute Design Verification (PDV) test series. As this was a novel test approach, a myriad of test configuration determinations needed to be made, both from the airdrop perspective as well as the parachute loading perspective. Personnel in the NAWCWD Escape, Parachute and Crashworthy Division spent the first year focusing on the development of the specialized airdrop equipment necessary for this test, including the release platform, load platform, a launch support structure, and a method to attach and release the packed parachute from a helicopter. They then performed an airdrop test to verify the function of the newly-developed equipment, as well as determine the motion characteristics of a 4,000-foot rope suspended by a helicopter. After this very successful test, which indicated that this test method just may work, significant development and fabrication began on the parachute loading apparatus.
JPL determined that the structure that supports the pulley would have to withstand 200,000 pounds of force. To support the pulley, a large tripod was designed with 12 inch-by-12 inch square beams spanning 40 feet. A large funnel to guide the rope to the pulley would be placed on top of the tripod bringing the total height to 19 feet. The tripod assembly was coordinated by Jack Ingle from the Escape, Parachute and Crashworthy Division with support from the NAWCWD Weapons Prototype Division and Weapons Survivabili
