Category NASA’S CONTRIBUTIONS TO AERONAUTICS

The partnership between NASA and the FAA that facilitates that exchange of ideas and technology was forged soon after both agencies were for­mally created in 1958. With the growing acceptance of commercial jet air­liners and the ever-increasing number of passengers who wanted to get to their destinations as quickly as possible, the United States began explor­ing the possibility of fielding a Supersonic Transport (SST). By 1964, it was suggested that duplication of effort was underway by researchers at the FAA and NASA, especially in upgrading existing jet powerplants required to propel the speedy airliner. The resulting series of meetings during the next year led to the creation in May 1965 of the NASA-FAA Coordinating Board, which was designed to "strengthen the coordina­tion, planning, and exchange of information between the two agencies.”[187]

The Airspace Concept Evaluation System (ACES) is a computer tool that allows researchers to try out novel Air Traffic Management (ATM) the­ories, weed out those that are not viable, and identify the most promis­ing concepts. ACES looks at how a proposed air transportation concept can work within the National Airspace System (NAS), with the aim of reducing delays, increasing capacity, and handling projected growth in air traffic. ACES does this by simulating the major components of the NAS, modeling a flight from gate to gate, and taking into account in its models the individual behaviors of those that affect the NAS, from depar­ture clearance to the traffic control tower, the weather office, navigation systems, pilot experience, type of aircraft, and other major components. ACES also is able to predict how one individual behavior can set up a ripple effect that touches, or has the potential to touch, the entire NAS. This modeling approach isolates the individual models so that they can continue to be enhanced, improved, and modified to represent new con­cepts without impacting development of the overall simulation system.[251]

Among the variables ACES has been tasked to run through its sim­ulations are environmental impacts when a change is introduced,[252] use

of various communication and navigation models,[253] validation of cer­tain concepts under different weather scenarios,[254] adjustments to spac­ing and merging of traffic around dense airports,[255] and reduction of air traffic controller workload by automating certain tasks.[256]

During World War II, human factors was pushed into even greater prom­inence as a science. During this wartime period of rapidly advancing military technology, greater demands were being placed on the users of this technology. Success or failure depended on such factors as the operators’ attention span, hand-eye coordination, situational awareness, and decision-making skills. These demands made it increasingly chal­lenging for operators of the latest military hardware—aircraft, tanks, ships, and other complex military machinery—to operate their equip­ment safely and efficiently.[316] Thus, the need for greater consideration of human factors issues in technological design became more obvious than ever before; as a consequence, the discipline of human engineer­ing emerged.[317] This branch of human factors research is involved with finding ways of designing "machines, operations, and work environ­ments so that they match human capacities and limitations.” Or, to put it another way, it is the "engineering of machines for human use and the engineering of human tasks for operating machines.”[318]

During World War II, no area of military technology had a more critical need for both human factors and human engineering consid­erations than did aviation.[319] Many of the biomedical problems afflict­ing airmen in the First World War had by this time been addressed, but new challenges had appeared. Most noticeable were the increased phys­iological strains for air crewmen who were now flying faster, higher, for longer periods of time, and—because of wartime demands—more aggressively than ever before. High-performance World War II aircraft were capable of cruising several times faster than they were in the pre­vious war and were routinely approaching the speed of sound in steep dives. Because of these higher speeds, they were also exerting more than enough gravitational g forces during turns and pullouts to render pilots almost instantly unconscious. In addition, some of these advanced air­craft could climb high into the stratosphere to altitudes exceeding 40,000 feet and were capable of more hours of flight-time endurance than their human operators possessed. Because of this phenomenal increase in aircraft technology, human factors research focused heavily on address­ing the problems of high-performance flight.[320]

The other aspect of the human factors challenge coming into play involved human engineering concerns. Aircraft of this era were exhibiting a rapidly escalating degree of complexity that made flying them—particu­larly under combat conditions—nearly overwhelming. Because of this com­bination of challenges to the mortals charged with operating these aircraft, human engineering became an increasingly vital aspect of aircraft design.[321]

During these wartime years, high-performance military aircraft were still crashing at an alarmingly high rate, in spite of rigorous pilot train­ing programs and structurally well-designed aircraft. It was eventually accepted that not all of these accidents could be adequately explained by the standard default excuse of "pilot error.” Instead, it became apparent that many of these crashes were more a result of "designer error” than operator error.[322] Military aircraft designers had to do more to help the humans charged with operating these complex, high-performance aircraft. Thus, not only was there a need during these war years for greater human safety and life support in the increasingly hostile environment aloft, but the crews also needed better-designed cockpits to help them perform the complex tasks necessary to carry out their missions and safely return.[323]

In earlier aircraft of this era, design and placement of controls and gauges tended to be purely engineer-driven; that is, they were constructed to be as light as possible and located wherever designers could most conveniently place them, using the shortest connections and simplest attachments. Because the needs of the users were not always taken into account, cockpit designs tended not to be as user-friendly as they should have been. This also meant that there was no attempt to standardize the cockpit layout between different types of aircraft. This contributed to longer and more difficult transitions to new aircraft with different instrument and control arrangements. This disregard for human needs in cockpit design resulted in decreased aircrew efficiency and perfor­mance, greater fatigue, and, ultimately, more mistakes.[324]

An example of this lack of human consideration in cockpit design was one that existed in an early model Boeing B-17 bomber. In this air­craft, the flap and landing gear handles were similar in appearance and proximity, and therefore easily confused. This unfortunate arrangement had already inducted several pilots into the dreaded "gear-up club,” when, after landing, they inadvertently retracted the landing gear instead of the intended flaps. To address this problem, a young Air Corps physiologist and Yale psychology Ph. D. named Alphonse Chapanis proved that the incidence of such pilot errors could be greatly reduced by more logical control design and placement. His ingeniously simple solution of mov­ing the controls apart from one another and attaching different shapes to the various handles allowed pilots to determine by touch alone which control to activate. This fix—though not exactly rocket science—was all that was needed to end a dangerous and costly problem.[325]

As a result of a host of human-operator problems, such as those described above, wartime aircraft design engineers began routinely working with industrial and engineering psychologists and flight sur­geons to optimize human utilization of this technology. Thus was born in aviation the concept of human factors in engineering design, a disci­pline that would become increasingly crucial in the decades to come.[326]

NASA and a group of U. S. aerospace corporations began research for this ambitious program in 1990. Their goal was to develop a jet capa­ble of transporting up to 300 passengers at more than twice the speed of sound. An important human factors-related spinoff of the so-called High-Speed Civil Transport (HSCT) was an External Visibility System. This system replaced forward cockpit windows with displays of video images with computer-generated graphics. This system would have allowed better performance and safety than unaided human vision while

eliminating the need for the "droop nose” that the supersonic Concorde required for low-speed operations. Although this program was phased out in fiscal year (FY) 1999 for budgetary reasons, the successful vision technology produced was handed over to the previously discussed AvSP – AvSSP’s Synthetic Vision Systems element for further development.[430]

One of the more complex and challenging areas in aerospace technology is the prediction of paths of aircraft components following the release of items such as external stores, canopies, crew modules, or vehicles dropped from mother ships. Aerodynamic interference phenomena between vehicles can cause major safety-of-flight issues, resulting in catastrophic impact of the components with the airplane. Unexpected pressures and shock waves can dramatically change the expected tra­jectory of stores. Conventional wind tunnel tests used to obtain aero­dynamic inputs for calculations of separation trajectories must cover a wide range of test parameters, and the requirement for dynamic aero­dynamic information further complicates the task. Measurement of aerodynamic pressures, forces, and moments on vehicles in proximity to one another in wind tunnels is a highly challenging technical proce­dure. The use of dynamically scaled free-flight models can quickly pro­vide a qualitative indication of separation dynamics, thereby providing guidance for wind tunnel test planning and early identification of poten­tially critical flight conditions.

Separation testing for military aircraft components using dynamic models at Langley evolved into a specialty at the Langley 300-mph 7- by 10-Foot Tunnel, where subsonic separation studies included assess­ments of the trajectories taken by released cockpit capsules, stores, and canopies. In addition, bomb releases were simulated for several bomb – bay configurations, and the trajectories of model rockets fired from the wingtips of models were also evaluated. As requests for specific separa­tion studies mounted, the staff rapidly accumulated unique expertise in

testing techniques for separation clearance.[500] One of the more important separation studies conducted in the Langley tunnel was an assessment of the launch dynamics of the X-15/B-52 combination for launches of the X-15. Prior to the X-15, launches of research aircraft from carrier aircraft had only been made from the fuselage centerline location of the mother ship. In view of the asymmetrical location of the X-15 under the right wing of the B-52, concern arose as to the aerodynamic loads encountered during separation and the safety of the launching procedure. Separation studies were therefore conducted in the Langley 300-mph 7- by 10-Foot Tunnel and the Langley High-Speed 7- by 10-Foot Tunnel.[501]

Detailed measurements of the aerodynamic loads on the X-15 in proximity to the B-52 under its right wing were made during conven­tional force tests in the high-speed tunnel, while the trajectory of a dynamically scaled X-15 model was observed during a separate inves­tigation in the low-speed tunnel. The test set up for the low-speed drop tests used a dynamically scaled X-15 model under the left wing of the B-52 model to accommodate viewing stations in the tunnel. Initial trim settings for the X-15 were determined to avoid contact with the B-52, and the drop tests showed that the resulting trajectory motions provided adequate clearance for all conditions investigated.

During successful subsonic separation events, a bomb or external store is released, and gravity typically pulls it away safely. At super­sonic speeds, however, aerodynamic forces are appreciably higher rel­ative to the store weight, shock waves may cause unexpected pressures that severely influence the store trajectory or bomb guidance system, and aerodynamic interference effects may cause catastrophic collisions after launch. Under some conditions, bombs released from within a fuselage bomb bay at supersonic speeds have encountered adverse flow fields, to the extent that the bombs have reentered the bomb bay. In the early 1950s, the NACA advisory committees strongly recommended that focused efforts be initiated by the Agency in store separation, especially for supersonic flight conditions. Researchers within Langley’s Pilotless Aircraft Research Division used their Preflight Jet facility at Wallops to conduct research on supersonic separation characteristics for several

high-priority military programs.[502] The Preflight Jet facility was designed to check out ramjet engines prior to rocket launches, consisting of a "blow down’-type tunnel powered by compressed air exhausted through a supersonic nozzle. Test Mach number capability was from 1.4 to 2.25. With an open throat and no danger to a downstream facility drive sys­tem, the facility proved to be ideal for dynamic studies of bombs or stores following supersonic releases.

One of the more crucial tests conducted in the Wallops Preflight Jet facility was support for the development of the Republic F-105 fighter – bomber, which was specifically designed with forcible ejection of bombs from within the bomb bay to avoid the issues associated with external releases at supersonic speeds. For the test program, a half-fuselage model (with bomb bay) was mounted to the top of the nozzle, and the ejection sequence included extension of folding fins on the store after release. A piston and rod assembly from the open bomb bay forcefully ejected the

store, and high-speed photography documented the motion of the store and its trajectory. The F-105 program expanded to include numerous specific and generic bomb and store shapes requiring almost 2 years of tests in the facility. Numerous generic and specific aircraft separation studies in the Preflight Jet facility from 1954 to 1959 included F-105 pilot escape, F-104 wing drop-tank separations, F-106 store releases from an internal bomb bay, and B-58 pod drops.

Jeremy Kinney

Even before the invention of the airplane, wind tunnels have been key in undertaking fundamental research in aerodynamics and evaluat­ing design concepts and configurations. Wind tunnels are essential for aeronautical research, whether for subsonic, transonic, supersonic, or hypersonic flight. The swept wing, delta wing, blended wing body shapes, lifting bodies, hypersonic boost-gliders, and other flight con­cepts have been evaluated and refined in NACA and NASA tunnels.

N NOVEMBER 2004, the small X-43A scramjet hypersonic research vehicle achieved Mach 9.8, roughly 6,600 mph, the fastest speed ever attained by an air-breathing engine. During the course of the vehicle’s 10-second engine burn over the Pacific Ocean, the National Aeronautics and Space Administration (NASA) offered the promise of a new revolu­tion in aviation, that of high-speed global travel and cost-effective entry into space. Randy Voland, project engineer at Langley Research Center, exclaimed that the flight "looked really, really good” and that "in fact, it looked like one of our simulations.”[528] In the early 21st century, the pub­lic’s awareness of modern aeronautical research recognized advanced computer simulations and dramatic flight tests, such as the launching of the X-43A mounted to the front of a Pegasus rocket booster from NASA’s venerable B-52 platform. A key element in the success of the X-43A was a technology as old as the airplane itself: the wind tunnel, a fundamen­tal research tool that also has evolved over the past century of flight.

NASA and its predecessor, the National Advisory Committee for Aeronautics (NACA), have been at the forefront of aerospace research since the early 20th century and on into the 21st. NASA made funda­mental contributions to the development and refinement of aircraft and spacecraft—from commercial airliners to the Space Shuttle—for

operation at various speeds. The core of this success has been NASA’s innovation, development, and use of wind tunnels. At crucial moments in the history of the United States, the NACA-NASA introduced state-of – the-art testing technologies as the aerospace community needed them, placing the organization onto the world stage.

The history of composite development reveals at least as many false starts and technological blind alleys as genuine progress. Leo Baekeland, an American inventor of Dutch descent, started a revolution in mate­rials science in 1907. Forming a new polymer of phenol and formal­dehyde, Baekeland had succeeded in inventing the first thermosetting plastic, called Bakelite. Although various types of plastic had been developed in previous decades, Bakelite was the first commercial success. Baekeland’s true breakthrough was inventing a process that allowed the mass production of a thermosetting plastic to be done cheaply enough to serve the mechanical and fiscal needs of a huge cross section of prod­ucts, from industrial equipment to consumer goods.

It is no small irony that powered flight and thermosetting plas­tics were invented within a few years of each other. William F. Durand, the first Chairman of the NACA, the forerunner of NASA, in 1918 summarized the key structural issue facing any aircraft designer. Delivering the sixth Wilbur Wright Memorial Lecture to the Royal Aeronautical Society, the former naval officer and mechanical engineer said, "Broadly speaking, the fundamental problem in all airplane construction is adequate strength or function on minimum weight.” [648] A second major structural concern, which NACA officials would soon come to fully appreciate, was the effect of corrosion on first wood, then metal, structures. Thermosetting plastics, one of two major forms of composite materials, present a tantalizing solution to both problems. The challenge has been to develop composite matrices and production processes that can mass-produce materials strong enough to replace wood and metal, yet affordable enough to meet commercial interests.

While Baekeland’s grand innovation in 1907 immediately made strides in other sectors, aviation would be slow to realize the benefit of thermosetting plastics.

The substance was too brittle and too week in tensional strength to be used immediately in contemporary aircraft structures. But Bakelite eventually found its place by 1912, when some aircraft manufacturers started using the substance as a less corrosive glue to bind the joints between wooden structures.[649] The material shortages of World War I, how­ever, would force the Government and its fledgling NACA organization to start considering alternative sources to wood for primary structures. In 1917, in fact, the NACA began what would become a decades-long effort to investigate and develop alternatives to wood, beginning with metal. As a very young bureaucracy with few resources for staffing or research, the NACA would not gain its own facilities to conduct research until the Langley laboratory in Virginia was opened in 1920. Instead, the NACA committee formed to investigate potential solutions to mate­rials problems, such as a shortage of wood for war production of air­craft, and recommended that the Army and the Bureau of Standards study commercially available aluminum alloys and steels for their suit­ability as wing spars.[650]

Even by this time, Bakelite could be found inside cockpits for instru­ments and other surfaces, but it was not yet considered as a primary or secondary load-bearing structure, even for the relatively lightweight aircraft of this age. Perhaps the first evidence that Bakelite could serve as an instrumental component in aircraft came in 1924. With fund­ing provided by the NACA, two early aircraft materials scientists— Frank W. Caldwell and N. S. Clay—ran tests on propellers made of Micarta material. The material was a generational improvement upon the phe­nolic resin introduced by Baekeland. Micarta is a laminated fabric—in this case cotton duck, or canvas—impregnated with the Bakelite resin.[651] Caldwell was the Government’s chief propeller engineer through 1928 and later served as chief engineer for Hamilton Standard. Caldwell is cred­ited with the invention of variable pitch propellers during the interwar period, which would eventually enable the Boeing Model 247 to achieve altitudes greater than 6,000 feet, thus clearing the Rocky Mountains and becoming a truly intercontinental aircraft. Micarta had already served

as a material for fixed-pitch blades in World War I engines, including the Liberty and the 300-horsepower Wright.[652] Fixed-pitch blades were optimized neither for takeoff or cruise. Caldwell wanted to allow the pilot to change the pitch of the blade as the airplane climbed, allow­ing the pitch to remain efficient in all phases of flight. Using the same technique, the pilot could also reverse the pitch of the blade after land­ing. The propeller blades now functioned as a brake, allowing the air­craft to operate on shorter runways. Finding the right material to use for the blades was foremost among the challenges for Caldwell and Clay. It had to be strong enough to survive the stronger aerodynamic forces as the blade changed its pitch. The extra strength had to be balanced with the weight of the material, and metal alloys had not yet advanced far enough in the early 1920s. However, Caldwell and Clay found that Micarta was suitable. In an NACA technical report, they concluded: "The reversible and adjustable propeller with micarta blades. . . is one of the most practical devices yet worked out for this purpose. It is quite strong in all details, weighs very little more than the fixed pitch propeller and operates so easily that the pitch may be adjusted with two fingers on the control level when the engine is running.” The authors had performed flight tests comparing the same aircraft and engine using both Micarta and wooden propeller blades. The former exceeded the top speed of the wooden propeller by 2 miles per hour (mph), while turning the engine at about 120 fewer revolutions per minute (rpm) and maintaining a simi­lar rate of climb. The Micarta propeller was not only faster, it was also 7 percent more fuel efficient.[653]

The propeller work on Micarta showed that even if full-up plastics remained too weak for load-bearing applications, laminating wood with plastic glues provided a suitable alternative for that era’s demands for structural strength in aircraft designs. While American developers continued to make advances, critical research also was occurring over­seas. By the late 1920s, Otto Kraemer—a research scientist at Deutsche Versuchsanstalt fur Luftfahrt (DVL), the NACA’s equivalent body in Germany—had started combining phenolic resins with paper or cloth. When this fiber-reinforced resin failed to yield a material with a struc­tural stiffness superior to wood, Kraemer in 1933 started to investigate

birch veneers instead as a filler. Thin sheets of birch veneer impreg­nated with the phenolic resin were laminated into a stack 1 centimeter thick. The material proved stronger than wood and offered the capabil­ity of being molded into complex shapes, finally making plastic a viable option for aircraft production.[654] Kraemer also got the aviation industry’s attention by testing the durability of fiber-reinforced plastic resins. He exposed 1 – millimeter-thick sheets of the material to outdoor exposure for 15 months. His results showed that although the material frayed at the edges, its strength had eroded by only 14 percent. In comparison to other contemporary materials, these results were observed as "practically no loss of strength.”[655] In the late 1930s, European designers also fabri­cated propellers using a wood veneer impregnated with a resin varnish.[656]

A critical date in aircraft structural history is March 31, 1931, the day a Fokker F-10A Trimotor crashed in Kansas, with Notre Dame foot­ball coach Knute Rockne among the eight passengers killed. Crash inves­tigators determined that the glues joining the wing strut to the F-10A’s fuselage had been seriously deteriorated by exposure to moisture. The cumulative weakening of the joint caused the wing to break off in flight. The crash triggered a surge of nationwide negative publicity about the weaknesses of wood materials used in aircraft structures. This caused the aviation industry and passengers to embrace the transition from wood to metal for airplane materials, even as progress in synthetic mate­rials, especially involving wood impregnated with phenolic resins, had started to develop in earnest.[657]

In his landmark text on the aviation industry’s transition from wood to metal, Eric Schatzberg sharply criticizes the ambivalence of the NACAs leadership toward nonmetal alternatives as shortsightedness. For exam­ple, "In the case of the NACA, this neglect involved more than passive ignorance,” Schatzberg argues, "but rather an active rejection of research on the new adhesives.” However, with the military, airlines, and the trav­eling public all "voting with their feet,” or, more precisely, their bank accounts, in favor of the metal option, it is not difficult to understand the NACA leadership’s reluctance to invest scarce resources to develop
wood-based synthetic aircraft materials. The specimens developed during this period clearly lacked the popular support devoted to metal. Indeed, given the dominant role that metal structures were to play in aircraft and aerospace technology for most of the next 70 years, the priority placed on metal by the NACAs experts could be viewed as strategically prescient.

That is not to say that synthetic materials, such as plastic resins, were ignored by the aerospace industry in the 1930s. The technology of phenol- and formaldehyde-based resins had already grown beyond functioning as an adhesive with superior properties for resisting corro­sion. The next step was using these highly moisture-resistant mixtures to form plywood and other laminated wood parts.[658] Ultimately, the same resins could be used as an impregnant that could be reinforced by wood,[659] essentially a carbon-based material. These early researchers had discovered the building blocks for what would become the carbon – fiber-reinforced plastic material that dominates the composite structures market for aircraft. Of course, there were also plenty of early applica­tions, albeit with few commercial successes. A host of early attempts to bypass the era of metal aircraft, with its armies of riveters and con­cerns over corrosion and metal fatigue, would begin in the mid-1930s.

Clarence Chamberlin, who missed his chance by a few weeks to beat Charles Lindbergh across the Atlantic in 1927, flew an all-composite airplane. Called the Airmobile, it was designed by Harry Atwood, once a pupil of the Wright brothers, who flew from Boston to Washington, DC, in 1910, landing on the White House lawn.[660] Unfortunately, the full story of the Airmobile would expose Atwood as a charlatan and fraud. However, even if Atwood’s dubious financing schemes ultimately hurt his reputation, his design for the Airmobile was legitimate; for its day, it was a major achievement. With a 22-foot wingspan and a 16-foot- long cabin, the Airmobile weighed only 800 pounds. Its low weight was achieved by constructing the wings, fuselage, tail surfaces, and aile­rons with a new material called Duply, a thin veneer from a birch tree impregnated with a cellulose acetate.[661]

Writing a technical note for the NACA in 1937, G. M. Kline, work­ing for the Bureau of Standards, described the Airmobile’s construction: "The wings and fuselage were each molded in one piece of extremely thin films of wood and cellulose acetate.”[662] To raise money and attract public attention, however, Atwood oversold his ability to manufacture the air­craft cheaply and reliably. According to his farfetched publicity claims, 10 workers starting at 8 a. m. could build a new Airmobile from a sin­gle, 6-inch-diameter birch tree and have the airplane flying by dinner.

After a 12-minute first flight before 2,000 gawkers at the Nashua, NH, airport, Chamberlin complained that the aircraft was "nose heavy” but otherwise flew well. But any chance of pursuing full-scale manufacturing of the Airmobile would be short-lived. To develop the Airmobile, Atwood had accumulated more than 200 impatient creditors and a staggering debt greater than $100,000. The Airmobile’s manufac­turing process needed a long time to mature, and the Duply material was not nearly as easy to fabricate as advertised. The Airmobile idea was dropped as Atwood’s converted furniture factory fell into insolvency.[663]

Also in the late 1930s, two early aviation legends—Eugene Vidal and Virginius Clark—pursued separate paths to manufacture an air­craft made of a laminated wood. Despite the military’s focus on devel­oping and buying all-metal aircraft, Vidal secured a contract in 1938 to provide a wing assembly molded from a thermoplastic resin. Vidal also received a small contract to deliver a static test model for a basic trainer designated the BT-11. Schatzberg writes: "A significant innova­tion in the Vidal process was the molding of stiffeners and the skin in a single step.” Clark, meanwhile, partnered with Fairchild and Haskelite to build the F-46, the first airliner type made of all-synthetic materi­als. Haskelite reported that only nine men built the first half-shell of the fuselage within 2 hours. The F-46 first flew in 1937 and generated a great amount of interest. However, the estimated costs to develop the molds necessary to build Clark’s proposed production system (greater than $230,000) exceeded the amount private or military investors were willing to spend. Clark’s duramold technology was later acquired by Howard Hughes and put to use on the HK-1 flying boat (famously nick­named—inaccurately—the "Spruce Goose”).[664]

The February 16, 1939, issue of the U. K.-based Flight magazine offers a fascinating contemporary account of Clark’s progress:

Recent reports from America paint in glowing terms a new process said to have been invented by Col Virginius Clark (of Clark Y wing section fame) by which aero­plane fuselages and wings can, it is claimed, be built of plastic materials in two hours by nine men. . . . There is little doubt that Col Clark and his associates of the Bakelite Corporation and the Haskelite Manufacturing Corporation have evolved a method of production which is rapid and cheap. Exactly how rapid and how cheap time will show. In the meantime, it is well to remember that we are not standing still in this country. Dr. Norman de Bruyne has been doing excellent work on plastics at Duxford, and the Airscrew Company of Weybridge is doing some very interesting and promising experimen­tal and development work with reinforced wood.[665]

The NACA first moved to undertake research in plastics for aircraft in 1936, tasking Kline to conduct a review of the technical research already completed.[666] Kline conducted a survey of "reinforced phenol – formaldehyde resin” as a structural material for aircraft. The survey was made with the "cooperation and financial support” of the NACA. Kline also summarized the industry’s dilemma in an NACA technical note:

In the fabrication of aircraft today the labor costs are high relative to the costs of tools. If large sections could be molded in one piece, the labor costs would be reduced but the cost of the molds and presses would be very high. Such a change in type construction would be economically practicable excepting the mass produc­tion of aircraft of a standard design. Langley suggests, therefore, that progress in the utilization of plastics in aircraft construction will be made by the gradual intro­duction of these materials into an otherwise orthodox
structure, and that the early stages of this development will involve the molding of such small units as fins and rudders and the fabrication of the larger units from reinforced sheets and molded sections by conventional methods of jointing.[667]

Kline essentially was predicting the focus of a massive NASA research program that would not get started for nearly four more decades. The subsequent effort was conducted along the lines that Kline prescribed and will be discussed later in this essay. Kline also seemed to under­stand how far ahead the age of composite structure would be for the aviation industry, especially as aircraft would quickly grow larger and more capable than he probably imagined. "It is very difficult to outline specific problems on this subject,” Kline wrote, "because the explora­tion of the potential applications of reinforced plastics to aircraft con­struction is in its infancy, and is still uncharted.”[668]

In 1939, an NACA technical report noted that synthetic materials had already started making an impact in aircraft construction of that era. The technology was still unsuited for supporting the weight of the aircraft in flight or on the ground, but the relative lightness and durabil­ity of synthetics made them popular for a range of accessories. Inside a wood or metal cockpit, a pilot scanned instruments with dials and casings made of synthetics and looked out a synthetic windshield. Synthetics also were employed for cabin soundproofing, lights encasings, pulleys, and the streamlined housings around loop antennas. The 1939 NACA paper concludes: "It is realized, at present, that the use of synthetic resin mate­rials in the aircraft industry have been limited to miscellaneous accesso­ries. The future is promising, however, for with continued development, resin materials suitable for aircraft structures will be produced.”[669]

In the mid-1970s, coincident with the beginning of the fuel and litiga­tion crises that would nearly destroy GA, production of homebuilt and kit-built aircraft greatly accelerated, reflecting the maturity of light air­craft design technology, the widespread availability of quality engineer­ing and technical education, and the frustration of would-be aircraft owners with rising aircraft prices. Indeed, by the early 1990s, kit sales would outnumber sales of production GA aircraft by more than four to one.[869] Today, in a far-different post-GARA era, kit sales remain strong. As well, new manufacturers appeared, some wedded to particular ideas or concepts, but many also showing a broader (and thus generally more successful) approach to light aircraft design.

Exemplifying this resurgence of individual creativity and insight was Burt Rutan of Mojave, CA. An accomplished engineer and flight – tester, Rutan designed a small two-seat canard light aircraft, the VariEze, powered by a 100-hp Continental engine. Futuristic in look, the VariEze embodied very advanced thinking, including a GA(W)-1 wing section and Whitcomb winglets. The implications of applying the configuration to other civil and military aircraft of far greater performance were obvious, and NASA studied his work both in the tunnel and via flight tests of the VariEze itself.[870] Rutan’s influence upon advanced general aviation air­craft thinking was immediate. Beech adopted a canard configuration for a proposed King Air replacement, the Starship, and Rutan built a subscale demonstrator of the aircraft.[871] Rutan subsequently expanded his range of work, becoming a noted designer of remarkable flying machines capable of performance—such as flying nonstop around the world or rocketing into the upper atmosphere—many would have held impossible to attain.

NASA followed Rutan’s work with interest, for the canard config­uration was one that had great applicability across the range of air­craft design, from light aircraft to supersonic military and civil designs. Langley tunnel tests in 1984 confirmed that with a forward center of gravity location, the canard configuration was extremely stall-resistant. Conversely, at an aft center of gravity location, and with high power, the canard had reduced longitudinal stability and a tendency to enter a high – angle-attack, deep-stall trim condition.[872] NASA researchers undertook a second series of tests, comparing the canard with other wing planforms including closely coupled dual wings, swept forward-swept rearward wings, joined wings, and conventional wing-tail configurations, evaluat­ing their application to a hypothetical 350-mph, 1,500-mile-range 6- or 12-passenger aircraft operating at 30,000 to 40,000 feet. In these tests, the dual wing configuration prevailed, due to greater structural weight efficiencies than other approaches.[873]

Seeking optimal structural efficiency has always been an important aspect of aircraft design, and the balance between configuration choice and structural design is a fine one. The advent of composite structures enabled a revolution in structural and aerodynamic design fully as sig­nificant as that at the time of the transformation of the airplane from wood to metal. As designers then had initially simply replaced wooden components with metal ones, so, too, in the earliest stage of the com­posite revolution, designers had initially simply replaced metal com­ponents with composite ones. In many of their own GA proposals and studies, NASA researchers repeatedly stressed the importance of getting away from such a "metal replacement” approach and, instead, adopt­ing composite structures for their own inherent merit.[874]

The blend of research strains coming from NASA’s diverse work in structures, propulsion, controls, and aerodynamics, joined to the cre­ative impact of outside sources in industry and academia—not least of which were student study projects, many reflecting an insight and expertise belying the relative inexperience of their creators—informed NASA’s next steps beyond AGATE. Student design competitions offered a valuable means of both "growing” a knowledgeable future aerospace workforce and seeking fresh approaches and insight. Beginning in 1994, NASA joined with the FAA and the Air Force Research Laboratory to sponsor a yearly National General Aviation Design Competition estab­lishing design baselines for single-pilot, 2- to 6-passenger vehicles, tur­bine or piston-powered, capable of 150 to 400 knots airspeed, and with a range of 800 to 1,000 miles. The Virginia Space Grant Consortium at Old Dominion University Peninsula Center, near Langley Research Center, coordinated the competition. Competing teams had to address "design challenges” in such technical areas as integrated cockpit sys­tems; propulsion, noise, and emissions; integrated design and manu­facturing; aerodynamics; operating infrastructure; and unconventional designs (such as roadable aircraft).[875] In cascading fashion, other oppor­tunities existed for teams to take their designs to ever-more-advanced levels, even, ultimately, to building and test-flying them. Through these competitions, study teams explored integrating such diverse technical elements as advanced fiber optic flight control systems, laminar flow design, swept-forward wings, HITS cockpit technology, coupled with advanced Heads-up Displays (HUD) and sidestick flight control, and advanced composite materials to achieve increased efficiencies in per­formance and economic advantage over existing designs.[876]

Succeeding AGATE was SATS—the NASA Small Aircraft Transportation System Project. SATS (another Holmes initiative) sought to take the integrated products of this diverse research and form from it a distributed public airport network, with small aircraft flying on demand as users saw fit, thereby taking advantage of the ramp space capacity at over 5,000 public airports located around the country.[877] SATS would benefit as well by a Glenn Research Center initiative, the GAP (General Aviation Propulsion) program, seeking new propulsive effi­ciencies beyond those already obtained by previous NASA research.[878] In 2005, SATS concluded with a 3-day "Transformation of Air Travel” held at Danville Airport, VA, showcasing new aviation technologies with six air­craft equipped with advanced cockpit displays enabling them to operate from airports lacking radar or air traffic control services. Complementing SATS and GAP was PAV—a Langley initiative for Personal Air Vehicles, a reincarnation of an old dream of flight dating to the small ultralight aircraft and airships found at the dawn of flight, such as Alberto Santos – Dumont’s little one-person dirigibles and his Demoiselle light aircraft. Like many such studies through the years, PAV studies in the 2002-2005 period generated many innovative and imaginative concepts, but the

Agency did not support such studies afterwards, turning instead towards good stewardship and environmental responsibility, seeking to reduce emissions, noise, and improve economic efficiencies by reducing air­port delays and fuel consumption. These are not innocuous challenges: in 2005, airspace system capacity limitations generated fully $5.9 bil­lion in economic impact through airline delays, and the next year, fuel consumption constituted a full 26 percent of airline operating costs.[879]

The history of the NACA-NASA support of General Aviation is one of mutual endeavor and benefit. Examining that history reveals a surpris­ing interdependency between the technologies of air transport, military, and general aviation. Developments such as the supercritical wing, elec­tronic flight controls, turbofan propulsion, composite structures, syn­thetic vision systems, and heads-up displays that were first exploited for one have migrated and diffused more broadly across the entire aeronau­tical field. Once again, the lesson is clear: the many streams of NASA research form a rich and broad confluence that nourishes and invigorates the entire American aeronautical enterprise, ever renewing our nature as an aerospace nation.

The Low-Observable Flight Test Experiment (LoFLYTE) program was a joint effort among researchers at NASA Langley and the Air Force Research Laboratory with support from NASA Dryden and the 445th Flight Test Squadron at Edwards Air Force Base. Accurate Automation, Corp., of Chattanooga, TN, received a contract under NASA’s Small Business Innovation Research program to explore concepts for a stealthy hypersonic wave rider aircraft. The Navy and the National Science Foundation provided additional funding. A wave rider derives lift and experiences reduced drag because of the effects of riding its bow shock wave. Applications for wave rider technology include transatmospheric vehicles, high-speed passenger transports, missiles, and military aircraft.

The LoFLYTE vehicle was designed to serve as a testbed for a vari­ety of emerging aerospace technologies. These included rapid prototyp­ing, instrumentation, fault diagnosis and isolation techniques, real-time data acquisition and control, miniature telemetry systems, optimum antenna placement, electromagnetic interference minimization, advanced exhaust nozzle concepts, trajectory control techniques, advanced land­ing concepts, free-floating wingtip ailerons (called tiperons), and adap­tive compensation for pilot-induced oscillations.[1008] Most important of all, LoFLYTE was eventually to be equipped with neural network flight controls. Such a system employs a network of control nodes that inter­act in a similar fashion to neurons in the human brain. The network "learns,” altering the aircraft’s flight controls to optimize performance and take pilot responses into consideration. This would be particularly useful in situations in which a pilot needed to make decisions quickly and land a damaged aircraft safely, even if its controls are partially destroyed. Researchers also expected that neural network controls would be useful for flying unstable configurations, such as those necessary for efficient hypersonic-flight vehicles. The computing power of Accurate Automation’s neural network was provided by 16,000 parallel neurons making 1 billion decisions per second, giving it the capability to adjust to changing flight conditions faster than could a human pilot.[1009] The LoFLYTE model was just 100 inches long, with a span of 62 inches and a height of 24 inches. It weighed 80 pounds and was configured as a narrow delta planform with two vertical stabilizer fins. The shell of the model, made from fiberglass, foam, and balsa wood, was constructed at Mississippi State University’s Raspet Flight Research Laboratory and then shipped to SWB Turbines in Appleton, WI, for installation of radio control equipment and a 42-pound-thrust microturbine engine.[1010] The first flight took place at Mojave Airport, CA, on December 16, 1996. The vehicle was not yet equipped with a neural network and relied instead on conventional computerized stabilization and control systems. All went well as the LoFLYTE climbed to an altitude of about 150 feet and the pilot began a 180-degree turn. At that point—about 34 seconds into the flight—the ground pilot was forced to land the craft wheels-up in the sand beside the runway because of control difficulties. The model suffered only minor damage, and researchers generally considered the flight a suc­cess because it was the first time a wave-rider-concept vehicle had taken off under its own power.[1011] Testing resumed in June 1997 with several flights from the Edwards North Base runway. This gave researchers the opportunity to verify the subsonic airworthiness of the wave rider shape and analyze basic handling characteristics. The results showed that a full – scale vehicle would be capable of taking off and landing at normal speeds (i. e., those comparable to such high-speed aircraft as the SR-71). Flight tests of the neural network control system began in December 1997 and continued into 1998. These included experiments to verify the system’s ability to handle changes in airframe configuration (such as removal of vertical stabilizers) and simulated damage to control surfaces.[1012]

The American involvement in combat operations in Vietnam escalated by the late 1960s to something that was not called a war by the Government but actually was. The public turned against the war as casualties and costs escalated; by 1968, a sense of distrust of the Government and all its programs also affected a significant portion of the populace. The Apollo program was about to achieve President Kennedy’s goal of landing on the Moon, but people were beginning to question its value. A youth – oriented cultural shift had not only a pro-peace stance but also an anti­technology bent, and environmental movements such as the Sierra Club were becoming increasingly influential. Nuclear powerplants and nuclear weapons were increasingly cited as being harmful to the environment, and many people wanted them limited or banned. The United States SST program was a high-visibility target and opportunity for environmental movements. Initially, the arguments focused on the sonic booms to be produced by an SST fleet. Dr. William Shurcliff, a Harvard University physicist, formed the Citizens League against the Sonic Boom to argue against the SST. As the SST and Sonic Boom Handbook (published in 1970 by an environmental activist organization) stated on its jacket, "This book demonstrates that the SST is an incredible, unnecessary insult to
the living environment, and an albatross around the neck of whatever nations seek to promote it.”[1094]

American legislators were not deaf to this increasing clamor. The sonic boom problem remained real and apparently technically unsolv­able. An operational solution was to ban overland supersonic flights by the SST. This had a serious impact on the economic case for an air­plane that would have to fly at off-design cruise speeds for significant amounts of time if flying on anything other than transatlantic or trans­pacific flights. Transcontinental flights in the United States had always been a prime revenue generator for airlines. A further noise problem was represented by New York City airports surrounded by densely pop­ulated communities. Subsonic jets with 10,000-pound thrust engines had difficulty meeting local noise standards; engines with 30,000 and even 60,000 pounds of thrust promised to be even more intractable. But even solving these problems would not satisfy some later environmen­tal concerns. Water vapor from SST exhaust at high altitude having the potential to damage the protective ozone layer was a major concern, which later proved to be unwarranted, even if 500 SSTs had been built (although this was not so for fluorocarbons in spray cans at sea level). At a hearing before the United States Senate in May 1970, a member of the President’s Environmental Quality Council referred to the SST as "the most significant unresolved environmental problem.”[1095] By late 1970, polls showed that American voters were 85 percent in favor of ending Federal funding for the SST program. In May 1971, the Senate voted to withhold further Government funding. Boeing, already developing the 737 and 747 at its own expense, said it could not proceed without $500 million in Federal funding. The American SST program of the 1960s was over.

The international SST race ended with only one horse crossing the finish line, albeit at a walk rather than a gallop. Although the Soviet SST flew first at the end of 1968, it required redesign and never was commer­cially successful. Two were lost in crashes during trials, and it only flew limited cargo flights from Moscow to Siberia over the sparsely populated Russian landmass. The SST field was left to the Anglo-French Concorde, which finally entered service on the transatlantic run in 1976 and flew for over 25 years. Only 13 aircraft entered service with the British and French national airlines, and most of their traffic was on the transatlantic run
for which the aircraft had initially been sized. The fuel price increase that started in 1974 and the de facto ban on overland supersonic flight meant that there was no move to improve or expand the Concorde fleet. It essen­tially remained a limited capacity first-class-only means of quickly getting from the United States to Paris or London while experiencing supersonic flight. Boeing’s privately financed gamble on the 747 jumbo jet turned out to be the winning hand, as it revolutionized air traveling habits, especially after airline deregulation began in the United States in 1978.[1096]