Aerodynamic Decelerators, The Year in Review,

Aerospace America, December 1999

Copyright c 1998 by the American Institute of Aeronautics and Astronautics, Inc, all rights reserved

Aerodynamic decelerator technology has made significant advances this year with many reported at the Aerodynamic Decelerator Systems Seminar and Conference (June 1999). Advances in fundamental research through large-scale development were reported. Smart decelerator technologies continue to be of high interest for many applications. New controllable concepts have been introduced and demonstrated. Advances in this area will continue rapidly as investments are increasing.

The NASA-JSC X-38 program is the largest controllable parafoil (Pioneer Aerospace) program in the world and currently manifested to fly on Space Shuttle Mission STS-111 (May 2001). This program was established to satisfy the ISS requirement for a crew return vehicle to replace Soyuz. The program performed its first free flight last year with additional successful flight tests since then. Focus on detailed modeling and testing to assure repeatable and predictable control of the deployment sequence, controlled flight and flared landing have lead to many advances in large parafoil technologies.

The Stardust program recovery system (Pioneer Aerospace) is the fourth in a series of NASA Discovery missions (launched, February 1999). After collecting cometary particles, this system's decelerator sub-system will be put to the test upon reentry (January 2006). Decelerator systems for space applications were numerous this year with controllable systems being considered for future applications.

Work continues on the Kistler Aerospace K-1 Reusable Launch Vehicle recovery system. The main parachute test program was concluded with the successful drop (see photo) of six 156 foot diameter ringsail parachutes (Irvin Aerospace) setting a new world record. Ground impact requirements are being met with advanced smart airbags.

The Sombrero slider (Butler Aerospace) has shown great promise for controlling and consistent openings of round parachutes. Slider technology is dominant for small sport parafoils and initial validation of the "ideal parachute model" with experimental testing (Parks College) is ongoing. Mechanical systems to control decelerator opening loads are also showing great promise (Vertigo and Martin-Baker Aircraft).

The US DoD continues to invest in new decelerator technologies. Methods of softlanding cargo and personnel are being explored which include pneumatic muscle actuators (PMA's) (Vertigo). PMA's have been demonstrated in a controllable round canopy application that pulls "riser slips" for directional control. Initial testing of this system on a G-12 (64ft diameter) round canopy (US Army) has demonstrated lift to drag ratios of 0.8. The US Air Force continues investment in airdrop related technologies which include advanced planning algorithms (Draper Labs). These utilize 3D wind predictions and/or measurements (Planning Systems Inc, Northrop Grumman and Lockheed Martin) and, in near real time, communicate with the pilot and relay coordinates etc. to controllable payloads.

Coupled aero-elastic computer models have the greatest potential to dramatically impact all decelerator system technologies and are being developed by groups around the world. Initial validation of fully coupled 3D models were demonstrated for a wide range of systems. These tools are being developed and concurrently validated with results from fundamental and applied wind tunnel testing. An airdrop virtual proving ground environment should be in place within the next few years.

Decelerator technology enters Y2K with more public interest and first time recreational jumpers than ever in history. The sport community has also made significant advances in personnel decelerators with many being scaled for larger applications. A virtual reality parachute simulator (Systems Technology Inc) has increased in fidelity and is being used by many larger organizations for training with new capabilities under development. This may be the closest experience available outside of really jumping. For links to decelerator technologies which include the topics discussed above, please visit our Technical Committee's homepage at:

By Richard J. Benney