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.
The 60s and 70s
In the 1960s, NASA partnered with industry to develop a common generic software program that engineers could use to model and analyze different aerospace structures, including any kind of spacecraft or aircraft. Today, NASTRAN is an industry-standard tool for computer- aided engineering of all types of structures. NASA’s specialists in computational fluid dynamics, or CFD, made huge strides in matching computer-based, aeronautical design and modeling code to the requirements of real-world flight. NASA developed sophisticated computer codes that could accurately predict the flow of a fluid using complex simulations, such as air over an aircraft’s wing or fuel through a space shuttle’s main engine. Today, CFD greatly reduces the time required to test and manufacture nearly any type of aircraft.
Also in the 1960s, NASA conceived and developed a process for cutting transverse grooves into runways to channel away standing water. Through two decades, NASA conducted more than 1,000 test runs of aircraft and ground vehicles, proving that grooved runway surfaces have significantly greater friction properties. Grooved runways have since helped aircraft make safe landings on pavement made slick from rain, snow, or ice. NASA’s groove process was adapted for use on military base runways, U.S. public highways, and even swimming pool decks.
During the 1960s and 1970s, NASA helped develop and flight test the digital “fly-by-wire” system, which replaced heavier and less reliable hydraulics systems with a digital computer and electric wires to send signals from the pilot to the control surfaces of an aircraft. Fly-by-wire is used today on new commercial and military aircraft, and on the space shuttle.
In aircraft materials research, NASA first partnered with industry during the 1970s to develop high-strength, nonmetallic materials that could replace heavier metals and aluminum on aircraft. Composite materials have gradually replaced metallic materials on parts of an aircraft’s tail, wings, fuselage, engine cowlings, and landing gear doors.
Beginning in 1976, NASA, the Army, and the Navy developed the first tiltrotor vehicle — the Bell XV-15 — that demonstrated the ability to hover like a helicopter but could then rotate its engines and rotors to achieve forward flight like a fixed-wing aircraft.
The 80s and 90s
The 1980s saw a flurry of NASA aeronautical developments, including stallresistant wing research that has influenced wing designs on modern general- aviation aircraft to improve stalldeparture characteristics, and onboard windshear-detection systems to alert pilots of the imminent approach of hazardous weather.
Also developed in the 1980s was airtraffic management automation re - search, using computers and specialty software to gather information from sources including radar, flight plans, and weather reports, to identify and predict where slowdowns may occur because of airspace congestion. Over the decades, NASA has developed a number of air-traffic management simulation tools, including the Center TRACON Automation System (CTAS) in the 1990s.
The Traffic Management Advisor (TMA), also developed in the 1990s, forecasts arriving air traffic to help controllers plan for safe arrivals during peak periods. The Surface Management System (SMS) lets controllers know when aircraft arrive on the ground or at the gate. Finally, the Future Air traffic management Concepts Evaluation Tool (FACET) maps thousands of aircraft trajectories to improve traffic flow across the United States.
During the 1980s and 1990s, NASA led the first comprehensive research program to discover the characteristics of microburst and wind shear hazards. The resulting NASA technology base led to the manufacture of on-board sensors that alert pilots in advance of wind shear hazards.
Another key research area came about as the result of the crash of a commuter flight in 1994, where supercooled large droplet (SLD) icing was suspected as a primary cause. At that time, little was known about the exact process whereby large droplets freeze on wings and how ice accumulates under SLD conditions. NASA collaborated with experts in such fields as atmospheric characterization, ice-accretion physics, and computer simulation in an SLD research initiative, which led to greater understanding of how such conditions arise and how pilots and planes can avoid them.
Other NASA aeronautics innovations included glass cockpits, which were pioneered in ground simulators and demonstration flights in NASA’s Boeing 737 flying laboratory. This technology replaced electromechanical dials and gauges with full-color, multifunction, electronic flat-panel displays on which pilots can select a variety of easy-to-read graphical views of key flight indicators. This concept quickly became commonplace on commercial, business, and military aircraft and eventually on the space shuttle in the 1990s.
Today and Beyond
NASA continued to push the aeronautical- research envelope in the first decade of this century. Research has begun to develop a cost-effective turbofan jet engine casing that could be lighter, but still protect against possible fan blade failure inside the engine. The solution was a fan case made of braided composite material that can reduce overall engine weight, increase safety, and improve aircraft structural integrity. NASA also is participating in NextGen, the Next Generation Air Transportation System. The NextGen goal is the overhaul of the nation’s air system to accommodate a doubling or even tripling of current capacity by the year 2025. Aiding in the effort is NASAcreated software to help air-traffic control systems become more efficient, rapidly generating thousands of aircraft trajectories that will enable smooth, minute-by-minute air-traffic flows at the national level.
Beyond NextGen, NASA is also examining how future aircraft could be retooled to become safer, quieter, and more environmentally friendly. For example, in the case of noise reduction, by leveraging computer simulations and wind tunnel and flight tests, NASA researchers have helped develop engine nozzle chevrons that use an asymmetricalscallops design to reduce noise in both the passenger cabin and on the ground.
NASA has also led the Synthetic Vision System (SVS) initiative, which makes use of flat-screen displays to provide real-time, clear-daylight views to pilots regardless of the weather or hour of the day. Visual information is culled from onboard sensors, inputs from a derivative of the Global Positioning System (GPS), and topographical databases that are subsequently analyzed and processed by computer. Synthetic Vision gives pilots a clear, electronic picture of what is beyond their windows, regardless of the weather or time of day.
NASA researchers are involved in a long-term project called the Morphing Project, in which airplanes will be able to change shape in flight as a bird does. This will permit the plane to adapt to a wide variety of flight conditions. To allow for more flexibility, the wings of the airplane are made of materials that cause the wings to be shaped more like a bird’s than those of the airplanes on which we now fly.
NASA, in partnership with Boeing, is researching a futuristic airplane body that could carry between 450 and 800 passengers for up to 7,000 miles at a maximum speed of 560 miles per hour while consuming 20 percent less fuel than today’s jetliners. The Blended Wing Body uses a flying wing shape as well as the standard features of today’s airplane. The wingspan of the aircraft would be just slightly wider than that of a conventional Boeing 747 and could operate from existing airport terminals.
Part of NASA’s ongoing experiments with unmanned airplanes is the Helios Prototype, which is remotely piloted from the ground. The goal of this research project is to fly the aircraft at an altitude above 50,000 feet for at least four days using only solar energy for power. In 2001, the Helios Prototype aircraft flew at a world-record height of 96,863 feet. Fitted with digital aerial cameras and other scientific instruments, this wing can assist farmers and can also act as a relay platform for telecommunications systems, enhance weather observation, and provide a disaster- monitoring and emergencyresponse communications relay.
This article features just a sampling of the aeronautical innovations developed by NASA. For a more comprehensive overview, visit the NASA 50th Anniversary Web site at: www.nasa.gov/50th/ .