By Christian Gelzer (Tybrin Corp.)
Historian, NASA Dryden Flight Research Center
Sixty years ago this September, the National Advisory Committee for Aeronautics (NACA) helped launch a new era in aviation. The NACA and its successor, NASA, have had a significant and uninterrupted presence in the high desert of Southern California ever since, leading to an unbroken chain of advances in aerospace.
Today the Hugh L. Dryden Flight Research Center at Edwards Air Force Base is NASA’s-indeed, the world’s-premier flight research center, dedicated to exploring the unknowns in atmospheric flight.
Over the past six decades there have been four major chapters in Dryden’s history-speed and control, access to space, the controls revolution, and efficiency and safety. To one degree or another, almost everything done at Dryden has fallen into one of those categories. And while it is convenient to think of them as chapters, it is useful to remember that the chapters overlap, and some are not yet finished.
Beginning in 1946 the NACA’s engineers, pilots and support staff at the newly established Muroc Flight Test Unit – which became today’s Dryden Flight Research Center – played a central role in determining whether an airplane could successfully exceed the speed of sound. That milestone was first accomplished in the famed Bell X-1 rocket plane, flown by Air Force Capt. Charles E. “Chuck” Yeager, in October 1947.
What drove the NACA’s research beside the dry lakebed in the high desert was the advent of the turbojet engine, which made the experiences, technology and understanding of aerodynamics over the preceding 40 years almost irrelevant. The higher speeds made possible by jet engines fundamentally altered aircraft design, construction, materials, speed, altitude, control and aerodynamics. The future of aviation drew little from the past at this juncture, and the NACA/NASA research efforts in the first two decades after World War II focused on these uncharted regions of flight.
Although the X-1 and its follow-ons demonstrated that one could successfully fly faster than the speed of sound, more questions about aircraft control at transonic speeds were tackled in the D-558-2 program, whose swept wings uncovered difficulties at certain points in flight. Air Force and NACA researchers at the Rogers Dry Lake base continued to explore high-speed flight and control with the X-4, an almost tailless aircraft, which revealed stability problems that could only be solved with advances in computers. The X-5 demonstrated that an aircraft’s wings could be swept in flight, yielding greater efficiency and higher speeds.
But it was the X-15, the greatest rocket plane of them all, which caught the world’s attention. The X-15 explored hypersonic flight – above Mach 5 – attaining a speed of 4,520 mph on one flight; and exo-atmospheric flight, reaching an altitude of 67 miles on another. The X-15 also conducted countless experiments on human physiology outside the atmosphere, control of a vehicle in space, and dynamic heating, to list but a few.
By the 1960s, a noticeable broadening in Dryden’s focus included space-related activity, what has since been dubbed “access to space.” The X-15 began this move by virtue of its regular flights to the edge of space – eight of the twelve pilots were awarded astronauts wings – but it was not the only program with space as a component.
In the mid-60s Dryden began testing and validating the Lunar Landing Research Vehicle as a tool to train astronauts for actually landing on the moon. From the testing done at Dryden came the Lunar Landing Training Vehicles that the Apollo astronauts flew as their launch dates approached.
Dryden also pioneered the concept of lifting bodies, aircraft that had no wings but whose blunt shape made it possible to enter Earth’s atmosphere from space and glide to a controlled landing on a designated runway. This was in marked contrast to the only method then in use: descending in a capsule under parachutes. The success of the lightweight M2-F1 – the world’s first lifting body – led to a family of heavier lifting bodies, and data from these programs was applied to the development of the space shuttle.
The center continued its space-related efforts over the decades. Dryden has not only hosted nearly half of all space shuttle landings, it conducted essential research and testing for the shuttle, including the all-important validation of its unpowered approach and landing on return from space. More recently, Dryden successfully flew the X-43, the world’s first airframe-integrated scramjet; the two research vehicles reached speeds of nearly Mach 7 and Mach 10 during their missions, becoming the fastest air-breathing aircraft in the world.
Dryden’s work with the LLRV led directly to a third chapter in its history – digital-fly-by-wire controls. The LLRV was entirely controlled by on-board analog computers with no mechanical backup systems. This unique vehicle gave Dryden engineers confidence to apply that experience to modifying the flight controls of an F-8, from which they removed all mechanical and hydraulic controls.
In their place, engineers substituted a digital computer and small electric motors to drive the control surfaces of the wings and empennage. This program’s success not only benefited the space shuttle, it paved the way for computer-controlled aircraft in the military and commercial fields, and is now the dominant means of flight control for high-performance aircraft.
Moreover, Dryden conducted follow-on research with digital electronic engine controls, which, in turn, led to the development of self-repairing, and then intelligent flight control systems. The latter can enable an aircraft to remain flyable even after sustaining significant physical damage, because of its sophisticated computer system. Such digital controls enable more precise and efficient operation of an aircraft, as well.
Dryden engineers also pursued efficiency and safety in commercial and private aircraft, in what might be termed the fourth chapter in its history. In the 1970s, Dryden demonstrated the efficiency of a supercritical wing, a reshaped airfoil that allowed either higher speed or greater fuel efficiency at transonic speeds; such wings are now found on many new military, commercial, and corporate jets. At almost the same time, Dryden flew a pair of winglets on a KC-135 to validate a NASA assumption about improved efficiency. So effective were winglets that they, too, are now commonplace on business jets, commercial airliners, and even military transports.
On the ground, Dryden conducted research in the 1970s with aerodynamic fairings on trucks. The result was a redesigned long-haul truck cab that looks very much like what manufacturers make today, based on Dryden’s research three decades ago.
And Dryden engineers tested the strength of general aviation aircraft, verifying or disproving the stated airworthiness.
To researchers, failure is often more instructive than success, and such was the case with the Controlled Impact Demonstration in late 1984. To flight-validate an anti-misting additive to jet fuel intended to reduce the chance of a post-crash fire that the FAA was about to require in airliners, Dryden teamed with the Jet Propulsion Laboratory and Langley Research Center to intentionally crash an old Boeing 720 airliner, flown remotely, onto Rogers Dry Lake. To everyone’s surprise, the airplane exploded in a ball of fire. The additive was never used again.
Sixty years beyond its founding, the Hugh L. Dryden Flight Research Center remains deeply involved in aeronautical testing and research. A team of NASA and industry partners are preparing to fly a blended wing body, a design potentially capable of carrying far more than today’s aircraft can. And one of its F-15Bs serves as the test bed for the Intelligent Flight Controls System, which incorporates self-learning neural networks – a form of artificial intelligence – in aircraft control. The aeronautical future continues to be seen first at Dryden.
But Dryden is also aiding NASA’s space exploration effort, by managing the Constellation program’s launch abort system testing for the new Orion capsule planned for the next lunar mission. It continues its role as the primary alternate landing site for the remaining space shuttle missions. And its high-flying ER-2s continue their role in Earth science and satellite validation missions, to be augmented in the future by several high-altitude, long-endurance unmanned aircraft systems.
NASA Dryden’s six decades of achievement in flight research has laid the framework for advancing space and aeronautics technology through flight in the decades to come. As it celebrates its 60th anniversary on Sept. 30, 2006, the nation’s premier high-speed, high-altitude flight test and aerospace research facility looks to the future by continuing to fly what others only imagine.
PHOTO EDITORS: High-resolution photos to support this release are available electronically on the NASA Dryden web site at: http://www1.dfrc.nasa.gov/Gallery/Photo/Places/index.html. Photos EC01-0264-14 and EC01-0264-55 are suggested. Numerous other photos of aircraft mentioned in this article are also available at http://www1.dfrc.nasa.gov/Gallery/Photo/index.html. For historic video b-roll footage, please call (661) 276-3449.
For more information about NASA Dryden Flight Research Center and its research projects, visit: https://www.nasa.gov/centers/dryden on the Internet.
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