Americans have always supported government activities that enable citizens to travel more easily across the challenging distances and geographic diversity of the country.
Even during pre-Revolutionary times, several colonies funded astronomy observations that led to improved celestial charts for pathfinding across the trackless North American wilderness and navigating its uncharted coastlines. Later generations funded construction of canals, railways, and interstate highways to improve travel as well as national security. And in the 20th century, the developing field of aeronautics attracted federal support as a promising technology both for transportation and for national defense.
During World War I, aeronautical groups in the United States learned that European aviation had dramatically surpassed American technology; Congress responded in 1915 by authorizing the organization of the National Advisory Committee for Aeronautics, soon known as NACA.
With a small administrative staff in Washington, D.C., NACA was intended to coordinate research under way elsewhere, but it quickly became a leader in aeronautics and astronautics research and its name became inextricably linked to the wind tunnels and research laboratories at Langley, Va. For many years these were NACA's only research facilities.
In 1958, responding again to a perceived lack of leadership in U.S. astronautics, the agency changed its name to the National Aeronautics and Space Administration: NASA. With new facilities devoted to rocketry and space exploration, NASA by 1988 had become a diverse bureaucracy with headquarters in Washington, D.C., and eight centers (including the contracted facilities of the Jet Propulsion Laboratory in California) from coast to coast. But aviation research remained the fundamental focus at Langley, dedicated in 1920, Ames Research Center near San Francisco (1939), Glenn Research Center in Cleveland (1940; formerly the Lewis Center), and Dryden Flight Research Center (1946) in the high desert north of Los Angeles.
After a slow start, NACA during the 1920s became globally recognized for its work in developing airfoil sections and improved propellers, as well as for a host of research and development efforts that advanced the understanding of aeronautical phenomena and the technology of flight. One early NACA effort involved close cooperation with the U.S. Navy to improve aircraft designed for operations from aircraft carriers. Research focused on aerodynamics and on countering the corrosive effects of salt on airframes and internal parts.
NACA's tradition of cutting-edge aeronautical research—and technical reports that enjoyed worldwide circulation—continued at NASA. Along the way, both agencies also integrated research and development from abroad.
Over the years, some aircraft—both civil and military—came to symbolize the collective success of various flight research activities; others represented specialized, experimental aircraft for specific research goals. Following are eight aircraft whose innovations represent just a sample of NACA/NASA's remarkable contributions to 70 years of worldwide aviation research—and whose influence will continue for years to come.
Curtiss Hawk AT-5A
Span: 31 ft
Length: 23 ft
Weight: about 2,000 lbs
Engine: Wright R790-1 radial; 220 hp
Performance: 118 mph
Remarks: Different versions of this trainer served as "pursuit," or fighter, planes during the 1920s and were exported overseas as well. NACA cowling had the effect of adding 83 horsepower, an increase in percentage of the engine's original rating.
The Hawk, a standard pursuit plane of the era, became a test bed for one of NACA's most significant technological legacies—a cowling that enveloped the plane's radial, air-cooled engine. In contrast to in-line engines (with cylinders arranged in a line to diminish frontal drag) that required pumps and liquid coolant, radials had cylinders arranged in a circle around the crankshaft, allowing air cooling and thus a lighter engine. But their blunt configuration created considerable drag. In Great Britain, various studies of this problem in the 1920s resulted in a device known as the Townend ring—a narrow, rounded cuff that encircled the engine and helped reduce turbulent air flow.
About the same time, NACA wind-tunnel research produced an advanced design for the engine cowling. Enclosing the entire radial engine, its close-fitting installation smoothed out the air flow over the plane's blunt nose; at the same time, the cowling's design enhanced the cooling effects of air flow around the cylinders. With the cowling installed on the Hawk in 1928, the plane's speed jumped by 16 percent, from 118 to 137 miles an hour. The next year an improved configuration of the cowling increased the performance of a Lockheed plane from 157 to 177 miles an hour. Ongoing research continued to yield refined designs, and the NACA cowling—applied to both civil and military designs— became a worldwide feature of modern aviation.
Douglas DC-3, C-47
Span: 95 ft
Length: 64 ft
Weight: 25,000 lbs
Engine: (two) Wright radial engines or Pratt & Whitney radials; 1,200 hp each
Performance: cruise at 190 mph; 21 passengers,2 pilots, 1 cabin attendant
Remarks: The original version of the DC-3 was intended for overnight service and featured bunk-type beds for sleeping. More than 10,000 were built (including military C-47 and variants), plus 60 in Japan (under pre-war license) and 2,000 more in the Soviet Union.
The redoubtable Douglas DC-3 benefited from a number of research and development programs dating back to the 1920s, as well as more modern features such as cantilevered (internally braced) wings, powerful new engines, and new alloys that reduced weight.
The DC-3 inherited from NACA's workshops a NACA cowling and installation of the engines into the leading edge of the wing, an arrangement that quickly led to a low-wing design for multiengine airplanes. The leading-edge installation eliminated all manner of struts and guy wires to stabilize engines, and the low wing also permitted retractable landing gear, which reduced drag and contributed to dramatic increases in aerodynamic efficiency. Many years of NACA investigation into the mysteries of deadly icing contributed to the anti-icing devices installed on the leading edges of the DC-3's wings and tail surfaces. The DC-3 also benefited from NACA's work to produce more efficient airfoils (wing cross-section shapes) and improved propellers, and from its attention to streamlining—all of which led to a new generation of planes with enhanced performance.
During World War II, top speeds of the fastest propeller-driven fighters reached and sometime exceeded 450 miles an hour in level flight. Some aircraft achieved speeds around 500 miles an hour in a dive, and air flowing over the wings began to approximate the speed of sound. But the associated buffeting often proved so severe that planes broke apart. Thus the dreaded "sound barrier" challenged designers and engineers to develop a new generation of aircraft.
Prop-driven fighters had another drawback: The propellers themselves created drag at high speeds. But the gas turbine—or jet engine—introduced by the Germans and British toward the end of World War II eliminated that problem, pointing the way to very fast aircraft—as long as the sonic barrier could be safely breached. The speed of sound is conventionally given as 760 miles an hour at sea level, although it varies with altitude (for example, 670 miles an hour at 30,000 feet). The Austrian physicist Ernst Mach is credited with establishing its parameters, leading to terminology expressing the speed of sound as Mach 1 and so on.
Span: 28 ft
Length: 31 ft
Weight: 12,250 lbs
Engine: Reaction Motors XLR 11 liquid rocket engine; 6,000 lbs of thrust
Performance: Mach 1 and above
Remarks: After nine preliminary flights, the X-1 went supersonic on Oct. 14, 1947. Because of Cold War secrecy, no public announcement was made until eight months later.
In 1944 both U.S. Air Force and NACA personnel began to consider using a Mach 1 aircraft to investigate phenomena in subsonic and supersonic environments. Bell Aircraft became the contractor. Engineers settled on rocket propulsion to achieve the desired speeds, and Reaction Motors, a fledgling rocket technology company, designed the engine.
As the design for the supersonic plane evolved, engineers realized that little information was available about aerodynamics at such high speeds. But they found useful aerodynamic information about the ammunition used in the military's .50-caliber guns. The shape of what was to become the XS-1 (experimental, sonic, one) owed much to the ballistics data derived from a bullet; the aircraft's thin, straight wings and tail surfaces would minimize shock waves at high speeds.
A modified B-29 carried the XS-1 to an altitude of 20,000 feet, where the XS-1 dropped away and fired two of its rocket engines, zooming another 20,000 feet into the sky. As it leveled off, the remaining chambers ignited and accelerated the plane. On Oct. 14, 1947, Capt. Charles (Chuck) Yeager piloted the first supersonic flight above Muroc Army Air Field in California.
Douglas Skyrocket D-558-2
Span: 25 ft
Length: 42 ft
Weight: 9,421 lbs
Engine: Reaction Motors XLR-8RM6 liquid rocket engine; 6,000 lbs thrust
Performance: Mach 2
Remarks: A contemporaneous aircraft for subsonic research, the D-558-1 Skystreak relied solely on its single jet engine and represented a conventional design with straight wings and tail surfaces. Although early experimental planes sported bright orange or red colors, glossy white paint against the dark background of the sky proved better for optical tracking and observation.
Although NACA considered use of the swept wings in order to delay and moderate the effects of shock waves at high speeds, it remained hesitant to proceed with intensive research into the design. But after captured German research data and experimental aircraft designs from World War II demonstrated the logic of high-speed aircraft with swept-back wings, important American experimental planes included swept wings and tail surfaces. These planes generated invaluable data that influenced a new generation of Cold War fighter aircraft.
When the U.S. Navy decided it needed a swept-wing research plane for future combat designs, it collaborated with NACA and Douglas Aircraft to design the D-558-2 Skyrocket. The first of three such aircraft flew in 1948. The Navy soon abandoned plans to use an auxiliary jet engine in the plane, eliminating it in favor of modifications and additional fuel for its rocket propulsion system, built by Reaction Motors. In 1953 a modified Skyrocket became the first aircraft to achieve a flight of Mach 2, or twice the speed of sound. Like boomerangs and automobile tail fins, the Skyrocket's swept wings and tail surfaces became pop culture icons of the 1950s.
During the early postwar era, NACA joined Air Force and Navy research into hypersonic aircraft designs for flight at Mach 5 and above. Such speed generated enough friction heat to threaten the integrity of airframes, electronics, and fuel systems—not to mention the pilots. Meanwhile, the launch of the Soviet Union's Sputnik satellite in 1957 prompted the United States to inaugurate an ambitious new program of space exploration. A new era of flight had arrived, and in 1958 NACA became NASA.
North American X-15
Span: 22 ft
Length: 50 ft
Weight: 31,275 lbs [56,130 lbs for X-15-A2]
Engine: Reaction Motors XLR-99 liquid rocket engine; 57,000 lbs thrust
Performance: 4,104 mph; 314,750 ft
Remarks: A modified version, the X-15-A2, reached 4,534 mph and a record height of 354,200 ft. Flight missions for the X-15 aircraft required a unique "test range" with heavily instrumented tracking stations that stretched for several hundred miles across California, Nevada, and Utah.
A series of X-15 flights by a trio of planes is usually considered the most successful flight research program ever conducted. They bequeathed invaluable data such as robust designs for high-altitude, high-speed research; carefully programmed incremental flight-test procedures; telemetry; pilot physiology; and temperature research in hypersonic flight.
The rocket-powered X-15s flew at speeds exceeding 4,500 miles an hour and operated at altitudes of up to 354,200 feet, or 67 miles. Its development included experiments for exotic alloy materials for hypersonic aircraft. At speeds that sometimes generated temperatures of 1,300 degrees Fahrenheit, some sections of the aircraft glowed cherry-red.
The plane's structure and dark finish were carefully calculated to dissipate thermal stress. Pilots for the X-15 wore full-pressure helmets and flight suits, gear worn by astronauts in the Mercury and Gemini space programs. The plane's reaction-control system (small rocket motors), designed for extreme altitudes where conventional control surfaces became inoperative, also factored into later space missions. During flights of the X-15 to extreme altitudes, scientists were able to add an impressive roster of successful experiments in high-altitude physics. Small scientific packages carried on high-altitude missions yielded information on temperature gradients, the radiation environment, and assorted high-altitude phenomena.
Span: 27 ft
Length: 48 ft
Weight: 17,303 lbs
Engine: GE F404-GE-400 turbofan
Performance: Mach 1.8 (1,100 mph)
Remarks: Swept-forward wings appeared on a few wartime designs, including an experimental American glider and a German jet attack bomber (JU-287). Germany briefly produced a postwar corporate jet with swept-forward wings, the Hansa HFB-320, but none were intended for the Mach speeds attained by the X-29.
With its wings swept forward instead of toward the rear, the X-29 was one of the more startling shapes to fly. Built of new composites, the swept-forward wings were a highly experimental configuration intended to keep lifting surfaces and certain control surfaces in undisturbed air flow during high-speed flight. The plane had a vertical rudder, but conventional elevators were replaced by a pair of canard surfaces (small devices for horizontal control) mounted near the nose of the aircraft. The plane's complex aerodynamics included sophisticated computerized controls to keep the plane from flinging itself into disastrous flight attitudes that would tear it apart. Two X-29 aircraft were delivered to NASA and carried out 442 test flights.
While NASA continued to explore aspects of combat maneuverability and high-speed flight, increasing effort went into civil aviation. NASA conducted studies into cockpit engineering, communications, and pilot workload. Aspects of cutting-edge electronic displays and human interfaces came under closer scrutiny. Against this background, NASA also investigated procedures that would lead to better methods of air traffic control and safety for the increasing numbers of aircraft operating within the national airspace network.
Additional efforts focused on the light plane industry, especially research and development support for improved designs in the 21st century. One series of dramatic tests demonstrated the dangers of smaller aircraft venturing into the vortex air flow patterns that very large jet airliners left in their wake. Other investigations looked into reducing jet engine noise around airports. Important research involving light planes led to improved safety in the event of a crash, more efficient engines, and improved construction using composite materials.
Span: 95 ft
Length: 215 ft
Weight: 410,000 lbs at takeoff
Engine: (four) Kuznetsov NK-321 turbofans; 55,000 lbs thrust each
Performance: Mach 2.3 (about 1,550 mph)
Remarks: This plane was the final production example of 17 supersonic Tu-144 airliners. The "LL" suffix designated it as a high-speed research aircraft never intended for commercial service. Its engines were originally produced for the Tu-160 Blackjack bomber.
When NASA needed a large supersonic aircraft to carry out new flight tests for potential hypersonic transports, no suitable aircraft existed in the United States. Realizing that a test version of the original Tupolev Tu-144 SST—built during the Soviet regime—was still flyable, NASA and Russian bureaucrats took advantage of the post-Cold War thaw to work out a historic agreement involving the Tu-144LL (the LL designated a special "flying laboratory"). A team of engineers and flight-test personnel packed up a cargo of special gear and shipped it off to the former Soviet Union. After their arrival, the Americans worked with their Russian counterparts assembling the customized equipment and fitting it into the airplane. Carrying out flight experiments in Russian airspace—27 missions between 1996 and 1999—Russian and American pilots flew the SST with American observers and test personnel monitoring the research gear in the plane. Some of the flight tests and ground tests were conducted jointly.
Span: 38 ft
Length: 26 ft
Weight: 2,250 lbs
Engine: Continental IO-550-N piston engine; 310 hp
Performance: 212 mph
Remarks: Along with its composite construction, design of the Cirrus featured special attention to an aerodynamically smooth finish. Its fixed gear reduced mechanical complexity and associated costs. The parachute device (inset), installed on some gliders and ultralights, had never before been approved for a multi-seat, propeller-driven plane.
During the 1990s NASA began to implement plans for developing general aviation technology, making it safer, simpler, and more economical to operate light planes within the national airspace. In the process of winning a series of NASA research and development contracts, the Cirrus Design Corporation developed the four-place SR20 type from 1994 to 1998, when it received full certification. By the end of 2003 more than 1,000 planes had been delivered, including an upgraded SR22 model. The planes featured composite construction, a modern "glass cockpit," and careful attention to ergonomics, such as the side-mounted control handle, which replaced a control wheel or control stick directly in front of the pilot. The planes also incorporated a built-in emergency parachute—a unique feature for a production aircraft. By 2004 the parachute had been successfully activated in flight three times, allowing the planes and their occupants to drift safely to the ground.
In the 21st century NASA continues its work in technical reports, research, development, and flight testing, from private planes like the Cirrus to the highly experimental, unmanned X-43, a test vehicle powered by an exotic hydrogen engine. In 2004, during its final flight test, the X-43 hit a speed of Mach 10.