Volume 40       Issue 22       Dryden Flight Research Center, Edwards, California          November 30, 1998

Researching Spacecraft


Dryden's primary mission is aeronautics, but the center also
had played a critical role in researching spacecraft

By Dill Hunley
Dryden Historian

In the forty years since the inauguration of NASA on Oct. 1, 1958, the primary mission of what is today designated the NASA Dryden Flight Research Center has been atmospheric flight research. Especially since the formation of NASA, however, the Center under its various designations has made a great many contributions to NASA's space mission.

X-38
The X-38, which is a prototype for a Crew Return Vehicle for use on the International Space Station, had its first drop test at Dryden in March.
Already in the waning days of the National Advisory Committee for Aeronautics, the High-Speed Flight Station (as Dryden was then called) had begun investigations of reaction controls in the X-1B and a mechanical reaction control simulator, the iron cross (plus an analog computer). Because of fatigue cracks in its propellant tank, the X-1B flew only three times with reaction controls. The project of testing them then had to be transferred to the F-104, providing design guidelines that were applied to the X-15. NASA, in turn, applied the experience with simulation, the F-104, and the X-15 to the reaction controls used in the Mercury, Gemini, Apollo and Space Shuttle programs. This was only one of many contributions of the X-15, flown from 1959 to 1968, to NASA's space efforts. Among other things, the X-15 program, in partnership with the Air Force, Navy and North American, also contributed: the first practical, full-pressure suit for pilot protection in space; the first large, restartable, human-rated rocket engine; the first reusable superalloy structure for thermal protection against the temperatures and thermal gradients of reentry from space; and the first demonstration of piloted, lifting re-entry into the atmosphere.

Other X-15 contributions included a pilot's ability to function in the micro-gravity of space; measurements of hypersonic (Mach 5+) acoustics used in designing the Mercury capsule; successful use of an adaptive flight control system involving the automatic transition from aerodynamic to reaction controls and back again; methods of correlating flight data with wind-tunnel data so as to correct the latter; nitrogen cabin conditioning for safety; and the first employment of energy-management techniques.

Many of these items and much of the data from the X-15 were applied to the design and operation of the Space Shuttle, since the X-15 offered the only data for flying from Mach 3 to Mach 6.7, for piloted re-entry from space and for managing a vehicle's energy to land horizontally without engine power. Besides their role in testing reaction controls, the F-104 Starfighters performed other space-related flight research. Beginning in 1959, the Center drop-tested versions of the drogue parachute for Project Mercury from the F-104 at altitudes above 49,000 feet. The flight research revealed several critical design flaws that Project Mercury engineers corrected before use on the Mercury spacecraft. In the 1980s, a Starfighter and an F-15 conducted flight research on a variety of Shuttle tiles that yielded several discoveries about the abilities of the tiles to withstand launch and in-flight airloads as well as atmospheric moisture (clouds and rainfall).

Enterprise
Space Shuttle protype Enterprise is pictured on Rogers Dry Lakebed after one of its early drop tests from a specially modified Boeing 747. The 747 is part of a flyby to honor the successful completion of the test. the aerodynamic shape was proven at Dryden, Which also was the primary site for Space Shuttle landings early in the proigram Occasionally, Shuttles still land at Dryden. Dryden also was the site for testing Shuttle braking on the CV-990.
Then in 1996 and 1998, Dryden performed flight tests with an F-15B on the thermal protection system (TPS) for the X-33 Advanced Technology Demonstrator, which will test the technology for a potential next-generation reusable launch vehicle. Both series of tests of TPS materials on the F-15's flight test fixture were positive, boosting the confidence of the X-33 team in the ability of the materials to withstand the stresses they will encounter when the X-33 begins its flights from Dryden (projected for 1999). Dryden's venerable B-52 "008," which served as one of two motherships for the X-15 and also the lifting bodies, performed other space-related flight research. It conducted a series of drop tests on the parachute system designed to recover the Shuttle's solid rocket boosters, then tested a drag chute for the Shuttle itself. The B-52 also served as a launch aircraft for the Pegasus rocket six times from 1990 to 1994.

From 1963 to 1975, Dryden conducted a lifting-body flight research program - in conjunction with the Air Force, Ames and Langley Research Centers, Northrop and Martin- to offer astronauts a way to return from space than splashing down in a ballistic capsule and to demonstrate (at very low cost) the viability and versatility of wingless configurations, including their ability to fly to high altitudes and then land with their rocket engines no longer burning.

Their unpowered approaches and landings showed that the Space Shuttles need not decrease their payloads by carrying fuel and engines that would have been required for the conventional, powered landings initially planned for the Shuttle. The lifting bodies also prepared the way for the later X-33 and X-38 technology demonstrators that featured lifting-body shapes for, respectively, a reusable launch vehicle and a potential crew return vehicle from the International Space Station - two programs that Dryden is supporting today.

X-15
A U.S. Air Fiorce photo shows the X-15 in flight
Limitations of space do not permit detailed coverage of other important contributions of Dryden's flight research to NASA's space effort. Suffice it to say that the Center's development of (in partnership with Bell Aerosystems), and flight research with, the ungainly "flying bedsteads" known formally as the Lunar Landing Research Vehicles, together with their derivative Lunar Landing Training Vehicles, provided absolutely essential simulation for the Apollo astronauts' landing on the moon.

Also, Dryden's F-8 Digital Fly-By-Wire (DFBW) aircraft did the flight research on the IBM AP-101 digital flight control computer later used on the Shuttle, getting the bugs out of the system before the Shuttle used it. The DFBW team later solved the problem of pilot induced oscillation (PIO) revealed when astronaut (and former Dryden research pilot) Fred Haise made the first runway landing of the Shuttle prototype Enterprise on its fifth and last free flight in the Shuttle's Approach and Landing Tests here at Edwards. Suspecting (and then confirming in flight of the F-8 DFBW) that a 270-millisecond time delay in the Shuttle's flight control system was the cause of the PIO, the DFBW team designed a suppression filter that has resulted in safe landings of the Shuttle ever since - including a great many here at Edwards.

Finally, from 1993 to 1995, in conjunction with other centers, Dryden used a Convair CV-990 to perform Shuttle tire tests. The results provided the Space Shuttle program with data to support its flight rules and enabled it to resurface a grooved runway at Kennedy Space Center that had added unnecessary wear to the Shuttle tires.

In short, while Dryden's mission has been and remains primarily atmospheric flight research, from before the beginnings of NASA until today the Center has cooperated with its sister centers in NASA and its other partners to make a very large number of significant contributions to NASA's mission in space.

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November 13, 1998 X-Press

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