Aerodynamic Decelerators, The Year in Review,

Aerospace America, December 1995

Copyright c 1995 by the American Institute of Aeronautics and Astronautics, Inc, all rights reserved

Parachutes and other types of aerodynamic decelerators remain an integral component of military and space systems around the world. A new emphasis on precision delivery of men, munitions, and cargo has created an expanded interest in parafoils autonomously controlled by GPS navigation systems. Parachute scientists and engineers continue to investigate analytical methods to model the intricate fluid flow around the parachute during deployment and inflation.

The Army Natick Research, Development, and Engineering Center has teamed with Pioneer Aerospace and SSE to design and develop the guided parafoil airborne delivery system. GPADS will provide precision delivery of military equipment, vehicles, and supplies weighing up to 18 tons from offset distances of nearly 13 miles when dropped from altitudes of 25,000 ft. Each system consists of a gliding, nonpowered platform integrated with an autonomous GPS-based guidance and control system. Payload and platform hang under a 7,350-ft2 parafoil with a 150-ft wingspan and a 49-ft chord, more wing than any powered aircraft in production.

Inflation loads are managed by Pioneer's patented spanwise reefing system. This canopy has been dropped five times, with the final three drops incorporating SSE's navigation, guidance, and control system. The payload on the final drop test weighed 35,000 lb, the heaviest ever recovered by a parafoil.

Test parachutists have logged dozens of flights on GQ Parachute's high-glide advanced ram air (ARA) parachute. The ARA represents a major performance gain over the conventional parafoil, offering paratroopers even longer stand-off and greater wind penetration. Engineers have succeeded in closing and sweeping the canopy leading edge, substantially reducing drag as well as measurably increasing lift. Inflation vents and a central ram-air scoop ensure reliable inflation and positive pressurization of the envelope. Parachute glide ratios well above 7:1 have been recorded in carefully controlled, instrumented tests.

Textron Defense Systems has teaming with GQ to adapt the ARA parachute to the Army's Damocles autonomous intelligent submunition. Damocles is a dual-mode sensor fuzed submunition that maneuvers to find, classify, and destroy hidden surface-to-surface and surface-to-air rockets and missiles as will as command and control facilities. The ARA's extremely high glide ratio generates the broad search area required to ferret out high-value targets in hiding.

Parachute systems are being designed and developed for a multitude of space applications. A multinational team of scientists and engineers is developing a parachute recovery system for the Ariane 5 solid rocket boosters. ESA's Huygens space probe, due to be launched in October 1997, will use a parachute system for its descent onto Saturn's giant moon Titan. A successful full-scale descent flight rehearsal took place in northern Sweden in May, in close cooperation with ESA, the French space agency CNES, Aerospatiale, Martin- Baker Aircraft (U.K.), and Irvin Great Britain.

JPL is developing a descent and landing system comprising a parachute, retro rocket, and airbag impact attenuation system for the landing of NASA's Pathfinder spacecraft onto the surface of Mars. Sandia National Labs, ILC Dover, Pioneer Aerospace, and CDR Parachute Systems have designed, built, and tested prototype components.

Recent advances in numerical predictive capabilities include the ability to make calculations for the fluid flow over complicated parachute canopies; the coupling of calculations between the fluid flow and the parachute structure; development of some numerical tools to model the deployment process; and formulation of more sophisticated semiempirical momentum-base inflation models. Software engineers are adding front-end interfaces to these applications to provide tomorrow’s aerospace engineers with truly "user-friendly," practical design tools for desktop computer workstations.

by Donald Waye