Oliver “Perk” Perkins was the U.S. Navy’s liaison at Edwards who Crossfield hoped would be eager to secure a speed record for the navy. As a former naval aviator himself, Crossfield offered to make an attempt at reaching Mach 2 in the Skyrocket with “U.S. Navy” stamped all over the project. He sold Perkins on the idea, then urged him to lean on Dryden. If the pressure to fly at Mach 2 was coming from the navy and not from a zealous pilot, Crossfield expected Dryden might be more receptive to the idea. This circuitous and potentially professionally disastrous move was a daring one on Crossfield’s part, but it paid off. Perkins took the case right to the Pentagon, and a week later Dryden called Walt Williams at the Muroc Flight Test Unit to say that the Skyrocket’s speed ban had been lifted, but only for one flight. Crossfield had one shot to break Mach 2. If he missed, it would be Yeager’s record to secure in the X-1A. A delighted Crossfield promised Williams that he wouldn’t miss.
Friday, November 20, 1953, dawned cold and blustery in the desert. Shivering and weak from a recent bout of the flu, Crossfield arrived at Edwards before daybreak far more concerned with the Skyrocket’s health than his own; he was sure he could summon his mental and physical strength for the four minutes of powered flight. He found the Skyrocket nestled underneath the belly of a B-29 launch plane, surrounded by the swirling liquid oxygen vapor that accompanied fueling operations.
Crossfield recognized that he was asking the Skyrocket to perform a small miracle. As such, he resolved to do everything he could to help the vehicle along. He and the ground crews had developed a few tricks to squeeze as much speed out of the aircraft as possible. They figured out that shooting super-chilled liquid oxygen through the engine right before it was launched increased its performance. Crossfield had also learned, through trial and error on previous flights, the best sequence in which to light the engine’s barrels to get the most power out of all four combined. But nothing would help push the Skyrocket past Mach 2 more than carrying more fuel, and they had even come up with a means to increase the aircraft’s fuel capacity through cold soaking, a process that involved filling the tanks with super cold liquid oxygen hours before launch and letting it settle so the tanks would stretch out and hold a precious few extra pounds of fuel. The launch crews had also perfected a method for topping off the liquid oxygen tank right before releasing the Skyrocket, so Crossfield would have the most fuel available to burn. Crossfield had even had the ground crew wax and polish the Skyrocket’s fuselage so it would slice right through the air with the least amount of friction. He had one shot to break Mach 2, and he was pulling out all the stops to get there.
The B-29 took off into morning skies, and after an hour and a half, the bomber with the Skyrocket shackled to its belly was at its launch altitude of thirty-two thousand feet. The mother ship’s pilot released the Skyrocket, and Crossfield lit all four rocket barrels in rapid sequence to begin a smooth, shallow ascent into the upper atmosphere. He had calculated that his fuel load would afford him about two hundred seconds of powered flight, and getting the most from every second meant following a very precise arcing parabolic flight path; any deviation could cost him precious speed. The Skyrocket rose to seventy-two thousand feet before Crossfield pitched it over ever so slightly with his rocket engine still blazing. The cold soak had done the trick. The Skyrocket’s engine burned for a full 207 seconds before running out of fuel. In the cockpit, Crossfield watched as the Mach meter on his instrument panel edged over the 2.0 mark. He reached a top speed of Mach 2.005, a hair over twice the speed of sound but enough to secure the record.
With all his available fuel consumed, the Skyrocket’s engine abruptly shut down, throwing Crossfield forward against his restraints. The now silent and powerless aircraft started losing speed and altitude, gliding toward the ground and easing back into subsonic flight. Just twelve minutes after he’d launched from the B-29, Crossfield brought the Skyrocket to a smooth landing on the Rogers dry lake bed. A press conference at the Statler-Hilton hotel in Los Angeles the next day secured Crossfield’s place in history with reporters jockeying to interview the fastest man alive.
Twenty-two days later, Yeager made his own attempt to break Mach 2. Having failed to secure the record first, he at least wanted to break Crossfield’s record and take back the title of fastest man alive right in time for the fiftieth anniversary of the Wright brothers’ first flight on December 17. The first time Yeager had taken the X-1A out earlier that year, it felt familiar, and the two flights that followed had been equally smooth. His fourth flight, on December 12, was different, however.
The day started normally enough for Yeager, with a couple of hours spent hunting before he arrived at Edwards. After a light breakfast and a forced delay to mend a minor problem with his pressure suit, time he used to clean his shotgun, the X-1A was mounted underneath its B-50 launch plane, and Yeager was ready to go. At thirteen thousand feet, he climbed through the bomb bay into the small cockpit and checked out his systems before giving the B-50 crew the all clear to lower the domed canopy over his head and bolt it into place. Imprisoned at thirty thousand feet, Yeager heard the familiar sound of the shackles releasing the rocket plane from its mother ship and felt himself rise up in his seat at the sudden fall. He reached for his ignition switch, lit three rocket barrels, and watched as shock waves danced over his wings. With his nose slightly higher than anticipated, Yeager hit eighty thousand feet, and just before his engine ran out of fuel he hit Crossfield’s Mach 2.005. Then he pitched the unpowered X-1A over to gain more speed and watched as the needle on his Mach meter rose to 2.4.
It was only then that Yeager realized he was flying too fast at too high an altitude. One of his wings kept coming up, forcing the aircraft to roll over, and in the thin upper atmosphere he couldn’t fight the rolling motion. Bell Aircraft’s engineers had warned him not to take the aircraft above Mach 2.3, and they had been right. The roll had started right as Yeager hit Mach 2.4, then the X-1A started tumbling as it fell from the sky. Yeager was thrown around inside the cockpit so forcefully that his helmeted head broke through the canopy and nearly caused him to lose consciousness. Sensing a loss of pressure in the cockpit his pressure suit inflated, which immediately fogged up his faceplate. Yeager had half-obscured glimpses of light and dark, the Sun and the ground alternatively flashing by his line of sight as he continued to tumble. All the while, he could do little more than mumble unintelligibly over the radio. Still blind from the fogged helmet, Yeager groped over the familiar instrument panel and found the switch to readjust his rear stabilizer. It did the trick, and in the thicker atmosphere at thirty thousand feet the X-1A entered into a normal spin, something Yeager knew how to get out of. He recovered in just five thousand feet. Dazed and unsure whether the aircraft was too damaged to fly, Yeager managed to bring the X-1A to a safe landing on the dry lake bed at Edwards Air Force Base. Yeager’s skill and a fair bit of luck had saved his skin on what could have been a fatal flight.
Crossfield’s flight in the Skyrocket and Yeager’s near-death experience in the X-1A underscored a serious discrepancy. It was clear that aviation as an industry needed a new research plane to address the problems of flights in excess of Mach 2 if anything was eventually going to fly higher and faster. There was one aircraft under development that promised to make great strides, Bell Aircraft’s X-2. The X-2 was designed to expand the speed and altitude regimes of the X-1, but the program had been continually stunted by development problems, leaving it languishing in a hangar when it was needed in the sky. Desperate to see this powerful plane fly, Crossfield had asked Hugh Dryden if he could be loaned to Bell on a special assignment just to get the X-2 flight ready, then return to Edwards with the new research plane in tow. However useful it might have been to have an NACA representative pushing for the X-2’s completion, Dryden rejected the proposal. Crossfield was, Dryden countered, needed at Edwards.
Luckily for Crossfield’s desire for a more advanced research vehicle, Woods’s 1952 memorandum pitching a hypersonic ai
rcraft had eventually found some support at the NACA. The NACA Committee on Aeronautics wasn’t immediately interested in pursuing Woods’s proposed program but didn’t disregard the idea right away either. The proposal was shelved until a meeting that June during which the committee passed a two-stage resolution. First, it recommended that the NACA undertake a research program into flights up to fifty miles at hypersonic speeds between Mach 4 and Mach 10. The second called for some future program that would deal with flights above fifty miles at speeds from Mach 10 to escape velocity, speeds fast enough for the vehicle to achieve orbit. Spaceflight, however poorly understood and seemingly futuristic, was already in the minds of key decision makers. These early inclinations toward spaceflight spawned some early proposals, one of which called for a supersonic mother ship to launch a rocket plane fitted with Sergeant rockets developed at Caltech’s Jet Propulsion Laboratory to extremely high altitudes.
It took two years for the proposed hypersonic research program to take the first steps from concept toward reality. By 1954, experts agreed that the potential of rocket-powered aircraft, and particularly hypersonic flight, was exciting, but they also recognized that the future of hypersonic rocket-powered flight hinged on major advances in all areas of aircraft design. Sänger’s 1944 assumption that a boost-glide vehicle would demand only minor new technologies proved to be erroneous. Aerodynamic heating was one known problem, the so-called thermal barrier. Another was the challenge of flying in the thin upper atmosphere. Airplanes have control surfaces, ailerons, rudders, and elevators that push against the air to move the vehicle. But at altitudes where the air is too thin for traditional flight controls to push against, a pilot would need some other means of control. Hypersonic flight would remain fodder for science fiction until engineers could devise a high-altitude flight control system into a vehicle that could survive a punishingly hot reentry profile.
Luckily, the time was right for such an aircraft. Coming on the heels of the Mach 2 flights, consensus in the aviation industry was largely in favor of a continued rapid increase in speeds. That the engineering problems couldn’t be solved in ground testing was another factor pushing for a hypersonic flight research program. A new research airplane would be the test object and the sky, its laboratory. It would be powered by the same rocket engines that were powering the missiles being developed by the armed services. That there was no competing program under development helped push the NACA’s hypersonic research aircraft forward. After early successes, there was ample political and industry support for the X-series of aircraft to continue. The U.S. Air Force Science Advisory Board Aircraft Panel also believed that the time was right for a new NACA-military program and stood firmly behind the idea of developing a research aircraft to gather data at Mach numbers from 5 to 7 at altitudes of several hundred thousand feet.
The bureaucratic necessities to bring this hypersonic program to life were also falling into place in 1954. Dryden, a lifelong proponent of super- and hypersonic flight research and the NACA’s director, was named chairman of a new Air-Force-Navy-NACA Research Airplane Committee. This committee was dedicated to collecting experimental research aircraft data, exploring the problems of piloted flight at high speeds and altitudes, as well as guiding the development of an airplane to explore the problems of flight at the highest speeds and altitudes possible. The proposed hypersonic aircraft met the committee’s needs and fell under a now-familiar arrangement: the military would fund the development and construction of the aircraft that the NACA would use in its flight research program, and both the military and the civilian agency would benefit from the research results.
A hypersonic research program was formally initiated in February 1954 with goals ranging from probing these new flight areas in order to gather data to developing operational supersonic fighter aircraft that could fly between Mach 2 and Mach 3. Early studies set the basic design constraints such that the aircraft would address major areas of interest. Engineers with the NACA determined that the best way to return from high altitudes was to have the aircraft’s nose aimed toward the sky, a high angle of attack configuration that would expose the aircraft’s whole underside to the atmosphere, acting as a large aerodynamic brake. Preliminary studies revealed that control and stability were problems in desperate need of an answer; no one wanted a repeat of the flight that had nearly killed Yeager.
The launch configuration would also have to be different. The B-29s were being phased out and the next logical choice, the B-36, was too unknown to the team at the High Speed Flight Station and Edwards Air Force Base for them to turn it into a viable launch plane. The larger B-52 emerged as the best option for a new mother ship, but it lacked the large central bomb bay of the B-29. The hypersonic plane would have to be launched from underneath one wing. This practical decision introduced more unknowns, namely how the mother ship would take off and fly with an asymmetrical load and offset center of gravity that would change in flight at the moment of launch. Another consideration was the flight path of this proposed aircraft. To this point, all rocket aircraft had launched in the skies over and landed at the Rogers dry lake bed. Their powered flights were short and relatively low, allowing them to be monitored from ground stations at Edwards. This wouldn’t work for the hypersonic aircraft designed to fly higher and faster than anything else. If it were to land on Rogers, it would have to launch over another lake, and the pilot would have to rely on other dry lake beds in the vicinity if he ran into some midair emergency. Extending the physical space of the flight in turn demanded a better communications and tracking system.
By July, the NACA had completed its studies and was ready to present its hypersonic aircraft, designated X-15, to the U.S. Air Force and Navy. The preliminary concept set the basic design requirements of an aircraft obviously heavily influenced by missiles. Forty-eight feet long with stubby wings just twenty-seven feet across in the middle of the fuselage, it was mainly the small bump with two narrow windows toward the nose of the fuselage that made it clear that the vehicle was a manned aircraft and not a pilotless missile. A thick, wedge-shaped vertical stabilizer featured prominently in the aircraft’s rear, something engineers found broke up airflow to eliminate the kind of instability that had nearly killed Yeager. One Langley researcher had added a split trailing edge on the vertical stabilizer, something that could act as an additional speed break.
The NACA design also featured an x-shaped empennage, the stabilizing surface at the tail end of the aircraft, to bring increased stability and control to the high-speed flight through the thin upper atmosphere. To minimize the impact of aerodynamic heating, the NACA study specified that the X-15 be made of Inconel X, a nickel alloy that could withstand the intense temperatures the aircraft would be subjected to during reentry. Even though it wouldn’t be going into orbit, the X-15 would still descend quickly through multiple layers of the Earth’s atmosphere. To reach its prescribed high altitudes, the aircraft would have to fly a ballistic profile not unlike a missile, arcing high into the upper atmosphere before curving back down again. And the height of this ballistic path meant the aircraft would reach air thin enough to demand a system of hydrogen-peroxide-powered reaction controls for attitude control. The hypersonic aircraft emerged from this study as a futuristic vehicle, but for all the technological advances wrapped up in the program space wasn’t overtly in the cards. High-altitude flight was one thing, but space was still a dirty word as far as the air force was concerned. The service was in the business of expertly engineered, technologically advanced aircraft, not simple vehicles designed to leave the atmosphere.
Langley released the specifications of this conceptual research aircraft during a meeting at the NACA headquarters on July 9, 1954. In attendance were representatives from the aviation industry, the NACA, the air force, and the U.S. Navy by Dryden’s invitation; he wanted to get all military branches involved as well as the Department of Defense, though the hypersonic aircraft would be primarily a joint air force–NACA program with navy support. Wh
en the committee met again in October, Scott Crossfield was on hand as one of the NACA representatives. Having reviewed historical data relating to the project, he outlined for attendees the performance requirements for this new aircraft. And after watching the X-2 languish and coming face to face with the challenge of flying at just Mach 2, Crossfield was desperate to see this hypersonic research aircraft brought to life on schedule. But there were development challenges facing the project that went beyond the immediate technical aspects. Largely thanks to the Korean War, missiles were advancing in leaps and bounds and were routinely flying faster than Mach 10. This meant the technical side of hypersonic research was understood, leaving the human factor as the largest unknown. And this new program promised to take a massive leap. Instead of a series of vehicles designed to fly incrementally faster, this new aircraft was going to jump from Mach 2 to Mach 7, more than tripling existing speed records in one fell swoop. It was an audacious goal that risked becoming controversial enough to kill the project.
But once it gained momentum the X-15 program moved quickly. In December, the air force’s Air Materiel Command invited prospective bidders to submit their proposals. Four were received for evaluation by the NACA the following May from Bell Aircraft, Douglas Aircraft, North American Aviation, and Republic Aviation. Each proposal had its merits, and each contractor brought different experience to the program. Bell Aircraft, arguably the most experienced company when it came to building successful rocket-powered aircraft, pitched an airplane as simple and clean as the X-1. Douglas Aircraft also drew on its past successes, presenting a hypersonic aircraft reminiscent of the Skyrocket. Republic Aviation was at the time working on a Mach 3 interceptor aircraft and brought its relevant research to its X-15 proposal. Only North American Aviation had no experience building supersonic, rocket-powered aircraft, but it did have some experience building missiles; it was working on a winged cruise missile called Navajo that used the V-2 as its jumping-off point.
Breaking the Chains of Gravity Page 15
