NASA’s predecessor agency, the National Advisory Committee for Aeronautics (NACA), began a legacy of aeronautical innovation that continues today. While much of the focus of NASA’s first 50 years has been on the space-related achievements of the agency, it is the first “A” of the NASA acronym — aeronautics — that has resulted in many of the technologies that got the Apollo missions to the Moon, and that continue to improve our air travel safety today.
Early aeronautical problems included how to enable airplanes to fly faster while being more energy efficient. NACA/NASA researcher Richard Whitcomb created three crucial innovations to solve this problem: the area rule, the supercritical wing, and winglets, all of which would eventually be widely and routinely deployed on aircraft.
Whitcomb’s first innovation was the area rule in the 1950s. He found that if the fuselage of an airplane was narrowed to resemble the shape of an old-fashioned Coke bottle, drag would be substantially reduced and speed significantly increased — but without the need for additional engine power. Although quickly adopted by the military for supersonic fighter aircraft, the area rule made commercial subsonic jet travel practical by making it affordable.
In the 1960s, Whitcomb’s supercritical wing revolutionized the design of jet aircraft. The key was the development of a swept-back wing airfoil that delayed the onset of aerodynamic drag, increasing the fuel efficiency of aircraft flying close to the speed of sound. He found that a smoother flow of air would be achieved above wings not configured in the traditional bird-like shape. Instead, a wing virtually flat on top would produce less drag than one with an upper surface that curved downwards.
In the 1970s, Whitcomb’s third major advance was winglets — vertical wing tips that reduced yet another source of drag to further improve aerodynamic efficiency. The first aircraft to adopt winglets were within the general aviation and business jet communities. In the mid-80s, Boeing produced the 747-400 commercial jetliner, which used winglets to increase its range. Today, many airliners and private jets now sport wingtips that are angled up for better fuel performance.
In the late 1950s and through the 1960s, NASA partnered with the Navy and Air Force to develop the X-15 experimental aircraft (X-vehicles). Between 1959 and 1968, the X-15 made 199 flights, setting an altitude record of 354,200 feet (67 miles) on August 22, 1963, and a speed record of Mach 6.7 (4,520 mph) on October 3, 1967.
The X-15 program set benchmarks for hypersonic aircraft performance, stability, and control; high-temperature materials; shock interaction; and aerodynamic heating. It marked the use of the first reaction control system for attitude control in space, and development of the first practical full-pressure suit to protect pilots in space. Knowledge gained from X-15 flights contributed to all four American manned spaceflight programs: Mercury, Gemini, Apollo, and the space shuttle.
NASA’s X-vehicle programs are still going strong. One is the X-51, a joint venture with the Air Force and the Defense Advanced Research Projects Agency (DARPA) to develop a supersonic combustion ramjet — or scramjet — aircraft intended to fly at Mach 4.5 to 6.5. Engine tests on the ground successfully achieved a thrust equivalent of Mach 5.0 in 2007. The first test flights are scheduled for 2009.