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April 10, 2001

Release: 01-21

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On April 14, 1981, more than 300,000 aerospace aficionados assembled on the barren east shore of Rogers Dry Lake at Edwards Air Force Base to witness a first in aerospace history. Some seven miles away, on the ramp at NASA's Dryden Flight Research Center, another 20,000 distinguished visitors and NASA employees gathered to behold the same event.

They were rewarded that sunny spring morning, as the double-crack of a powerful sonic boom resounded across the desert, heralding the coming conclusion of the first Space Shuttle orbital mission. Moments later, astronauts John Young and Robert Crippen guided the shuttle Columbia onto lakebed runway 23, proving beyond shadow of doubt that a spacecraft could return to Earth safely with a powerless but controlled airplane-style landing. But NASA's flight research outpost in Southern California's high desert had made numerous contributions to the Space Shuttle program before that historic first landing, and has made many more since. Even today, 20 years after that epochal event, the Dryden Flight Research Center plays a significant though often overlooked role in America's space flight program. Dryden's major past and present contributions to the Space Shuttle program include:

* 1960s: Development of space-rated control, environmental and navigation systems - The X-15 hypersonic rocket plane program contributed directly to the Space Shuttle program through its pioneering development of reaction control systems for attitude control in space, including transition from aerodynamic controls to reaction controls and back again. Other X-15 contributions to the Shuttle program included the first practical full-pressure suit for pilot protection in space, inertial flight data systems in a high dynamic pressure space environment, demonstration of a pilot's ability to function in a weightless environment, and development of improved high-temperature seals and lubricants.

* 1960s-1970s: Energy Management Techniques for Re-entry and Landing - The X-15 rocket plane and the lifting bodies flown at Dryden made a major contribution to the development of energy management and unpowered landing techniques for the Space Shuttles. The X-15 and the wingless lifting bodies demonstrated that it was feasible for an aerospace vehicle with a low lift-to-drag ratio to make a safe, controlled landing without power.

* 1970s: The F-8 Digital Fly-By-Wire program - Another Dryden contribution to shuttle development was in the testing of the flight control computers later used on the shuttles. The IBM AP-101 computers were flight-validated during the second phase of the F-8 Digital Fly-By-Wire (DFBW) research program before they were used on the shuttles.

* 1970s: Shuttle Carrier Aircraft -- Once the decision had been made to eliminate jet engines for the shuttles' approach and landing at Edwards, a means of ferrying the shuttles back to the launch site had to be devised. Dryden engineers proposed a variation of the tried-and-true "mothership" concept that had been used for lifting the X-1 through X-15 and the lifting bodies to launch altitude; the modified Boeing747 Shuttle Carrier Aircraft evolved from their recommendation.

* 1970s: YF-12 High-Speed Research - During the high-speed, high-altitude flight research program conducted with the Lockheed YF-12, Dryden engineers developed a central airborne performance analyzer which monitored various aircraft systems, detected problems and provided that data to the pilot, as well as to engineers and maintenance personnel on the ground. The analyzer became the forerunner of vehicle health monitoring systems used on the space shuttles and a variety of today's aircraft.

* 1977: Shuttle Approach and Landing Tests -- Dryden hosted and helped conduct the Approach and Landing Tests (ALT) of the prototype shuttle orbiter Enterprise at Edwards AFB in 1977. The ALT validated the concept of carrying the shuttle on the 747 Shuttle Carrier Aircraft during captive-carry flights and of landing the shuttle without power during five free flights.

* 1977: Resolving Pilot-Induced Oscillation problem -- On the final ALT flight, the pilot overcontrolled the Enterprise and it entered a dangerous pilot induced oscillation (PIO)-a frequent phenomenon with new digital fight control systems-just at touchdown on Edwards' main concrete runway. Subsequent flights with the F-8 DFBW and other aircraft demonstrated that the problem with the shuttle flight control system lay in a time delay that stimulated pilots to over-control because their inputs to the flight control computer were taking too long to go into effect. With their experience with digital flight controls from the F-8 DFBW, Dryden engineers designed a PIO suppression filter that solved the problem and was incorporated into the shuttles' flight control computers.

* 1977-78, 1983-85: Booster Recovery System - Dryden's NB-52B mothership made 31 test flights in a two-phase project to validate the performance and reliability of the shuttle's solid rocket booster parachute recovery system. The parachutes are used to slow the descent of the solid rocket booster casings once they have completed their boost phase and separated from the shuttles' external fuel tank.

* 1979-80: Structural Loads and Orbiter Handling Analysis - At Johnson Space Center's request, Dryden engineers conducted an independent analysis of the shuttle design related to aerothermal-induced structural loads and handling qualities prior to its first space flight. Dryden's analysis found the shuttle's control system was capable of compensating for uncertainties in the shuttle's flight characteristics, and verified the overall adequacy of the design to accomplish re-entry from orbit and a safe landing on Earth.

* 1980s: Thermal Protection System Testing - Dryden research pilots flew 60 missions in Dryden's F-104 and F-15 aircraft to test space shuttle thermal protection tiles under various aerodynamic load conditions. The tests led to several changes to improve techniques for bonding the tiles to the shuttles' surfaces.

* 1990: Shuttle Drag Parachute Tests - NASA Dryden's venerable NB-52B was used to help develop the drag parachute deployment system now used during space shuttle landings. During a series of eight flight tests in 1990, the modified bomber validated the initiation, deployment, inflation and overall operation of the parachutes. The drag chutes are deployed from the shuttles moments after touchdown, reducing tire and brake wear and shortening the rollout distance on the runway.

* 1993-1995: Shuttle Tire and Brake Tests -- NASA Dryden modified a Convair 990 into a Landing Systems Research Aircraft in the mid-1990s to test the shuttles' tires and braking systems on a variety of runway surfaces. These tests led to improvements in both the tires and brakes, an increasing in the allowable crosswind landing limits and resurfacing of the runway at the Kennedy Space Center's Shuttle Landing Facility which reduced shuttle tire wear by half.

* 1981-Today: Primary/Alternate Landing Site - Dryden and the Edwards complex was the primary space shuttle landing site for the first 12 years of the program, and has served as the backup alternate landing site since then. Out of 102 shuttle missions completed to date, 47 have landed at Edwards, 54 at the Kennedy Space Center, and one at the White Sands Missile Range in New Mexico. The most recent mission to land at Edwards was STS-98, which saw the shuttle Atlantis land here on Feb. 20, 2001.

* 1981-Today: Shuttle Post-Flight Processing Capability -- Dryden maintains a full complement of equipment to support Space Shuttle landing, recovery, post-flight processing and turnaround operations to prepare the shuttles for their ferry flights back to the Florida launch site when landings occur at Edwards AFB. One of NASA's two modified Boeing 747 Shuttle Carrier Aircraft is maintained on-site for this purpose.


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