Breaking the Chains of Gravity Page 16

  To Crossfield, North American was the default winner right off the bat. Bell Aircraft was fast falling out of favor with the NACA over the X-2 debacle. Douglas Aircraft’s proposal was sound but had shirked the NACA’s recommendation to use Inconel X in favor of a material called HK31, which was significantly thicker, heavier, and ill-suited to the X-15’s demanding flight profile. Republic Aviation almost seemed to misinterpret the NACA’s guidelines in its proposal, pitching an aircraft that emphasized high speed over high altitude. North American Aviation’s proposal was the most straightforward, essentially giving the NACA its concept aircraft right back with just minor changes. North American’s version of the proposed X-15 was slightly longer at fifty feet with a slightly narrower twenty-two-foot wingspan. The NACA’s High Speed Flight Center, Ames Research Center, and Langley Research Center each evaluated the four proposals. Ames and Langley preferred North American’s proposal, while the High Speed Flight Center alone preferred Douglas’s. But its strong standing in the aviation world certainly helped push North American over the top. The company’s P-51 Mustang fighter planes were among pilots’ favorites of the Second World War and its F-86 Sabres were among the earliest American swept wing supersonic fighter jets taking on Soviet MiG-15s in dogfights over Korea. The final standing in July saw North American emerge as the winner. Its proposed aircraft wasn’t perfect, but it was on the right track. And to the chagrin of the military footing the bill, the winning bid came with the highest price tag of $56.1 million.

  After submitting its proposal, however, North American turned out not to be too keen on the idea of building a small run of three highly experimental aircraft, and the company requested to withdraw its proposal in September. Hugh Dryden was far more inclined to reopen the bidding process rather than award the contract to Douglas, the runner-up contractor, though the prospect wasn’t appealing. Hoping that North American would eventually change its mind, Dryden opted to continue with the procurement process in spite of the contractor’s reservations, though it didn’t look promising. North American was busy with other, much larger projects and remained unwilling to divert manpower to a small research project. The NACA offered to extend the proposed production schedule by eight months, but still North American’s chief engineer, Raymond Rice, shied away from accepting the contract.

  One man, however, was extremely anxious to secure the X-15 contract for North American. Harrison Storms was the manager of research and development at North American’s Los Angeles division. After studying under Theodore von Kármán at Caltech, Storms had cut his teeth in the aviation industry with North American during the Second World War. He had joined the company right after the Japanese attack on Pearl Harbor and devoted himself to building better airplanes for the American Army Air Force. He had been with the company ever since. One day in the midst of the X-15 contract discussions, Rice called Storms into his office. He could have the X-15, Rice told Storms, on one condition. Storms would have to take full charge of the program, acting as the top North American representative on the project, and keep every single problem off of Rice’s desk. With this new arrangement, North American finally accepted that it had won the X-15 contract. The first hypersonic research plane thus fell under a team led by Storms and Charles Feltz as chief project engineer.

  Storms might have been eager to get the X-15 program started, but Scott Crossfield had some lingering concerns. He worried that something as conceptually big as a hypersonic research aircraft would stall in the development stage and become stagnant like the X-2 had done for so long. So he went to Walt Williams at the High Speed Flight Station and again made a very specific and very unorthodox request of his director: he wanted to be officially assigned as the NACA liaison at North American Aviation on the X-15 project. He wanted to be on hand with the contractor to ensure the program met the NACA’s constraints and stayed on schedule. But Williams denied Crossfield’s request, again making the argument that Crossfield was needed at Edwards. Crossfield, however, disagreed, and was far firmer in his conviction this time around. When Williams refused to give in, Crossfield tendered his resignation from the NACA.

  His unemployment pending, Crossfield traveled alone to North American Aviation’s Los Angeles division, the site where the X-15 would be built. Luckily for Crossfield, having been the first man to reach Mach 2 meant he was known and respected in the aviation community, and he had already met a handful of industry giants, among them the president of North American Aviation, Lee Atwood. Crossfield went to Atwood’s office and presented the same proposal he had to Williams. He told Atwood he was a man who could bring a valuable wealth of knowledge, experience, and familiarity with rocket planes to an organization that was taking on this exotic challenge for the first time. He wanted to be part of the program from the start, from the initial designs all the way through the airplane’s entire construction and flight test program, making the first test flights before the X-15 was handed over to the NACA and U.S. Air Force for the record-breaking flights. It was an unusual proposal for Atwood, but both he and Rice signed off on it.

  Crossfield left North American’s Los Angeles division having created a job for himself, but he remained with the Muroc Flight Test Unit for a few months. The Muroc Flight Test Unit had changed drastically in the five years since he first toured the desert site. Originally run by the NACA’s Langley Memorial Laboratory, Congress had allocated funding to transform the satellite site into a new outpost in 1951. On July 1, 1954, the Muroc Flight Test Unit had been rededicated as the High Speed Flight Station, the newest NACA site with strong in-house capabilities to demonstrate the advances in high-speed aeronautics. Crossfield’s imminent departure, however, opened a spot for a new test pilot to join the NACA’s contingent at Edwards Air Force Base. To Neil Armstrong, also a young pilot engineer with a passion for research, Edwards was mecca.

  CHAPTER NINE

  Edging into Hypersonics

  In December 1955, Scott Crossfield pulled his car into a parking lot near a group of large manufacturing buildings on the south side of Los Angeles International Airport. Together, the buildings housed North American Aviation. Crossfield made his way to Building number 20, a Second World War–era relic that now housed the company’s cafeteria. Alongside the cafeteria was a small, cramped space employees called the garret. A sign on its door read SECRET, UNAUTHORIZED PERSONNEL PROHIBITED. Though right next to where they ate meals, no North American employee could pass through the door without being cleared to enter the area and signing into a logbook. Even then, every visitor needed an escort at all times. Crossfield, however, was cleared to enter the cramped space on his own. Inside he found a series of desks placed too close together where nearly a dozen men sat poring over papers and technical drawings. He took his place among the small team assigned to turn the X-15 from concept to reality. After years of dreaming of a hypersonic research aircraft to soaring through the skies over Edwards, Crossfield could finally start thinking about this plane in terms of real flight hardware.

  Everything about the X-15 was new and different. A giant in the aviation industry, North American usually built planes the way major auto manufacturers built cars in Detroit. Once an aircraft’s design was agreed upon by the engineers in charge, it was frozen, and the company set out to build a large run of its newest product with the efficiency of an assembly line. But the X-15 was different. Not only was it far more complex than any of North American’s previous aircraft, it had a very small production run with just three units contracted by the NACA. And because it was a specialized program, management was reluctant to take resources away from the larger programs that promised a financial return. As such, the X-15 became something of an anomaly, a project run by a small special team under the company’s Advanced Design Section, wholly independent from every other part of North American.

  After arguing with Raymond Rice to allow North American to take on the X-15 project, Harrison Storms was the overall manager of the program. But management of all day-to-day opera
tions was assigned to Charlie Feltz, the chief project engineer. A veteran mechanical engineer whose career began around the start of the Second World War, Feltz had never heard of the hypersonic research plane until the assignment landed on his desk and he became the leader of a skeleton crew of ten men. Crossfield’s arrival increased Feltz’s team to eleven, and the pilot was almost as much of an anomaly to Feltz as the X-15 was. The pilot turned consultant didn’t work directly for Feltz, he hadn’t been hired by Feltz, and his duties were vaguely undefined. Crossfield was there to lend his experience as a supersonic pilot to the team, a role that Feltz finally called Design Specialist. It was a somewhat haphazard title that suited Crossfield’s role as technical adviser and expert as well as anything.

  As Feltz’s team started hashing out the details of the X-15 based on the original proposal, it revealed itself as an increasingly complicated machine. Externally it was simple and sleek, a fairly traditional design for a rocket-powered aircraft. Its tall, thick vertical tail, elongated nose, and smooth body with a V-shaped canopy barely sticking up above the fuselage were fairly standard, as were its short, stubby wings jutting out from both sides. The most obviously unconventional thing about the X-15 was its power plant.

  The early concept drawings listed the engine as an XLR-99, a throttleable liquid-fueled rocket engine capable of delivering fifty-seven thousand pounds of thrust at forty thousand feet, meaning it could match most missiles in terms of its power output. Equivalent to about one million horsepower, the XLR-99 engine promised to accelerate the small plane to speeds in excess of 1.5 miles per second or nearly 8.7 million miles per hour, equivalent to about Mach 7 at altitudes over 250,000 feet. The X-15 would more than double existing speed and altitude records.

  Crossfield realized before too long that once the X-15 started making regular flights at breakneck speeds to unprecedented altitudes, engineers and scientists nationwide would be clamoring to add their experiments to the aircraft. But every addition threatened to add weight and delay production, so he gave himself an unofficial role as “the X-15’s chief son-of-a-bitch.” Nothing on the aircraft would change without going through him first. He was going to keep it on schedule come hell or high water.

  As soon as they started digging into the intricacies of the X-15, Feltz’s team unveiled no shortage of wrinkles that needed to be ironed out.

  Managing the X-15’s flight profile was one problem. It was clear that with a peak altitude above 250,000 feet the X-15 would need some kind of reaction control system to keep the aircraft oriented in the upper atmosphere; short bursts of compressed gas would allow the pilot to trim his attitude, adjusting his aircraft’s orientation in flight. But the pilot would also have to transition seamlessly from reaction controls to traditional flight controls on his long, gliding descent. Some kind of testing and development of this new system was in order.

  Atmospheric heating was another issue. Though the X-15 wouldn’t get as hot as Walter Dornberger’s proposed ultra planes, it would still be flying in a heat region about which fairly little was known. Construction materials would help; Inconel X, the steel-nickel alloy, was one strong ally in the X-15’s fight against high heat. But the edges of the aircraft that would bear the brunt of the heat would need something more to protect them. The initial solution was to add an ablative coating to these edges, something that could harmlessly burn away to protect the vehicle from the hottest portions of the flight. But this coating not only added weight to the aircraft, wind tunnel tests revealed that ablative leading edges would make the X-15 aerodynamically unstable. The only solution was to make the leading edges solid Inconel X, an effective but heavy solution.

  In the first months after Crossfield’s arrival at North American, the X-15’s development crew grew steadily, but so did the aircraft. Every pound added meant the aircraft would fly slightly slower and reach a slightly lower peak altitude. The use of solid Inconel X was only one matter. Another was the NACA’s stipulation that the X-15 have 3 percent fuel ullage allowance to account for the fact that the tanks could never be completely filled. But 3 percent of the aircraft’s eight tons of fuel translated to a loss of about two seconds of flight, a seemingly small but quite significant performance penalty. The solution was to increase the aircraft’s diameter to allow for larger fuel tanks, increasing its fuel capacity by twenty-five hundred pounds. But this solution also added weight. Small adjustments like this added up until the plane weighed in at thirty-one thousand pounds, at which point Feltz had to draw the line. The X-15 couldn’t get any bigger, he told his team, and urged the men to shave off as many ounces as they could from any nook or cranny that could spare it.

  The issue of weight became more complicated months into the X-15’s development when updated information on the XLR-99 engine said its power output would be lower than initially anticipated. There was no way to shave off enough weight to account for the now less powerful engine, but Feltz came up with an elegant solution to increase the aircraft’s lift to regain the lost speed and power. From the start, X-planes had maintenance tunnels running along the top and bottom of their fuselages. These were large, pipelike housings through which wires, control cables, and plumbing tubes were routed; because the fuel and oxidizer tanks took up most of the space inside these aircraft, routing plumbing and power cables around the tanks was a necessity. Feltz wondered whether the tunnels could be moved to the sides of the fuselage, broadening the base to increase its lift. Wind tunnel tests revealed his instinct was a good one. The side-mounted tunnels increased lift, and cutting them off just behind the cockpit combatted the strange aerodynamic phenomenon observed in wind tunnel testing that caused the nose to pitch up in flight.

  Questions also swirled around the X-15’s landing. Like the rocket planes that came before it, the X-15 was designed to glide to an unpowered landing on the dry lake bed at Edwards Air Force Base, touching down on rear skids and a forward nose wheel. But the tail became a problem. Early design studies and wind tunnel tests said that the best aerodynamic shape for the X-15’s vertical tail was a diamond shape as seen from an overhead perspective. Extending that diamond-shaped tail above and below the fuselage would bring the same stability to the high speed portions of the flight. But not only was it a heavy design, this tail extended beyond the skids and landing gear. The team half-joked that the tail promised to turn the X-15 into the world’s fastest plow upon landing.

  The whole X-15 team pored over drawings and blueprints together trying to find a solution to the plow problem. They finally brought Storms into the mix, the absent leader whose responsibility for the program’s success meant he was never more than a phone call away. In instances like this when he was called to bring his expertise to a problem, Storms descended on the team in a manner befitting his last name. He considered the X-15’s tail and offered what he viewed as an obvious solution: use an explosive charge to detach the lower portion of the tail before landing. It was only needed during the high-speed portions of the flight, so why not get rid of the lower portion once it was no longer useful? Storms similarly offered an elegantly simple way to shave weight off the aircraft. The forward half of the diamond tail was necessary, but the rear half was little more than the completion of the shape. Cutting it in half, turning it from a diamond into a wedge, could literally halve the weight of the tail. Wind tunnel tests confirmed that Storms’s instincts were right, and the changes were made.

  But for every problem the team solved, another one soon took its place. At one point in 1956, the U.S. Air Force alerted North American to a new ruling that said every air force plane had to have an escape pod for the pilot in lieu of a traditional ejection seat. Not only would an escape pod add about twelve hundred pounds to the X-15 at the cost of about one Mach number in speed, the related pyrotechnic system would further complicate the aircraft. Not only that, but Crossfield was dead set against an escape pod. The Douglas Skyrocket in which he’d reached Mach 2 had had an escape pod system that Crossfield swore he would never use after
early testing said the g-force associated with a pyrotechnic escape would almost certainly be fatal.

  Feltz agreed with Crossfield. In an emergency, the X-15’s cockpit was probably one of the safest places in the world. It was pressurized with non-flammable nitrogen gas so there was no risk of a fire, and the whole thing was reinforced to protect the pilot against the high g-forces of a hard landing. It would be far safer for a pilot to remain in the X-15 and eject at a slower, safer speed. Not to mention that making this kind of addition could only make the overall project more expensive and delay the X-15’s initial flight by as much as a year. Changing the air force’s mind, however, wasn’t as easy as calling the service to ask for an exception to the escape pod rule. So Feltz’s team was forced to go through engineering the escape pod meticulously to show exactly why it wasn’t necessary for the X-15.

  When the first cockpit mockup was completed in July 1956, it included a specially designed ejection seat with small stabilizers on the sides that would limit any oscillations upon ejection. The pilot would land by personal parachute. When air force representatives visited the North American facilities, they listened to Crossfield’s briefing and said nothing about his exclusion of the ejection pod. Crossfield, it seemed, swayed the air force men to his way of thinking. They signed off on the design, which passed with flying colors. It was one instance, Crossfield felt, when he truly lived up to his self-proclaimed title of the X-15’s chief SOB.