Breaking the Chains of Gravity

by Amy Shira Teitel

  Feltz’s X-15 team had to deal with more than just technical flight considerations. The pilot’s comfort was another matter. Unlike what Chuck Yeager had done with the X-1, the X-15 pilot couldn’t ride up to altitude in the mother ship and climb into the rocket plane’s cockpit when it was time to launch. The launch plane for the X-15 had changed from the piston-powered B-36 to the jet-powered B-52, a larger bomber that would launch the X-15 from a pylon mounted underneath one of its wings. This meant the rocket aircraft’s pilot would be in the cramped cockpit for hours, waiting on the ground during the final fueling and checkout and throughout the B-52’s ascent. He would need some protection against stiffness and pain from the vibrations of the mother ship, but that protection had to be lightweight. Even a foam rubber cushion could add a devastating two pounds to the aircraft’s overall weight.

  The team in the garret sat down and asked themselves what company in the country had the most experience keeping men comfortable in a seat in rough conditions for hours at a time and came up with the International Harvester Company, a purveyor of tractors. Part of the company’s success was due to its investigation of the human spine’s natural frequency—its response to sitting in a vibrating vehicle for a length of time—and subsequent design of a seat that could protect it while driving over hard terrain. The seat in the X-15 was designed as an exact duplicate of a tractor seat.

  But honing the technical design of the X-15 was only half the battle. The pilot needed to be more than just comfortable, he had to be kept alive at extremely high altitudes. At sea level, atmospheric pressure is high enough that humans don’t have to wear protective garments. But above forty-five thousand feet, the atmosphere is so thin that blood wants to escape into the less dense environment and skin can’t compress the body enough to stop this from happening. With the X-15, flying higher than 250,000 feet, the pilot would need some protection against the thin atmosphere. The solution was a pressure suit. Pressure suits do at altitude what skin can do at sea level, compressing the body and exerting a restraining pressure on the skin to mimic the safety of sea level. In this case, the suit would have to be self-cooling to protect the pilot from succumbing to heat exhaustion and also provide him with enough oxygen to survive the flight. It would also need some arrangement of rubber bladders that could inflate at the first sign of high g-forces to protect the body during a high-speed ejection.

  Opinions were divided on the best pressure suits. At the time the U.S. Air Force favored a partial pressure suit, a cloth suit that simply squeezed the body with enough force to offset the effects of low atmospheric pressure. The navy preferred a full-pressure suit, a self-contained unit that could have applications far beyond high-altitude flights. The right full-pressure suit could protect men from the vacuum while walking on the surface of the Moon, which some forward-thinking navy engineers expected to see happen sooner rather than later. With this futuristic application in mind, David Clark had designed a full-pressure suit for the U. S. Navy that was like a wearable inner tube. An inner layer of rubberized nylon would inflate at altitude to compress the body and the outer layer of cloth would keep the nylon firmly in place. It was a flexible design that wouldn’t constrict the pilot’s movements much, thanks to the fabric. In the 1930s, David Clark had invented a knitting machine that could sew a seamless piece of fabric with two-way stretch. It became extremely popular for girdles and brassieres and allowed him to corner the market. His company had expanded to military garments beginning with the Second World War, but women’s undergarments remained his bread and butter.

  Crossfield strongly preferred the navy’s Clark-designed full pressure suit for the X-15. He had first discovered it in 1951 when he visited a navy laboratory in Philadelphia after his assignment to the Skyrocket program. He had donned the suit, climbed into an altitude chamber, and waited patiently as mechanics removed enough air to simulate an altitude of ninety thousand feet. A pleased Crossfield was somewhat stunned to learn that his test was the first time the suit had been used at such a simulated high altitude. Its benefits widely known, a version of the Clark suit had been included in North American’s bid for the X-15, and under Crossfield’s supervision it was on track to be the official life support system for the rocket plane’s future pilots.

  Over the course of his first year with North American, Feltz’s team was still feeling its way to bringing the X-15 to life. Crossfield remained the most familiar with rocket planes, but the group’s spirit made up for their collective lack of experience. The last half century had been a battle against drag and gravity, slowly developing the streamlined and efficient machines that would fight gravity and carry men off the ground. Now, this one aircraft—promising to send men into a wholly unknown region of near space—was coming together in record time, and the transition from final design to actual flight hardware couldn’t come soon enough.

  With the X-planes at Edwards growing increasingly antiquated, the need for the new research aircraft was fast becoming pressing. Coming on the heels of the X-1 as its immediate predecessor, the X-2 was intended not only to fly higher and faster than anything that had come before it but to withstand higher temperatures as well. This aircraft had been designed to begin tackling the problem of aerodynamic heating, clearing the way for the X-15 and later vehicles to push toward space. Made of stainless steel and a high-strength copper-nickel alloy called K-Monel, the aircraft’s fuselage was prepared for the heat associated with a Mach 3 flight.

  Many problems had dogged the X-2. Proposed not long after the Second World War ended, this aircraft’s high speed, high altitude, high heat flight profile hinged on the development of a host of new technologies, not all of which made it into the final aircraft. One unrealized system was fly-by-wire, a system that would feed the pilot’s control inputs from the cockpit into a computer that would in turn operate the aircraft’s control surfaces with motors. It was a decision that came down to scheduling. Though easier to fly and acting as a failsafe by checking the pilot’s inputs, fly-by-wire was eventually abandoned in favor of a conventional hydraulic system that could be incorporated into the aircraft sooner. This heavier system that had the pilot’s control inputs directly move the aircraft’s control surfaces left control squarely in the hands of the man in the cockpit. The X-2 also used a conventional gyroscope to give the pilot information on his orientation, a device typically so inaccurate at high altitudes that it became basically unusable.

  Shortcomings aside, when the X-2 finally had rolled out and made its first glide flight in 1952, it was a very welcome addition to the hangars at Edwards where the X-1 was entering its fifth year as the most advanced aircraft on site. Now four years later, in 1956, the X-2 had racked up a mixed bag of successful missions and failed or aborted flights under the U.S. Air Force and Walt Williams was eager to take over the aircraft so the NACA could start probing the intricacies of aerodynamic heating. By early fall the handover was imminent, but the air force was reluctant to give up the X-2 without securing a new record. And so both parties worked out a deal wherein the X-2 would remain with the air force long enough for Captain Mel Apt to familiarize himself with the rocket-powered aircraft and make an attempt to reach Mach 3.

  Men weaving through the ghostly mist of liquid oxygen swirling around a bullet-like airplane nestled beneath a towering mother ship under predawn skies was fast becoming a familiar scene at Edwards Air Force Base. It was the scene unfolding on the morning of September 27, 1956, when Captain Mel Apt arrived. The runway adjacent to the Rogers dry lake bed was buzzing with activity as technicians readied and fueled a small white aircraft with wide swept-back wings and a long pointed nose for the morning’s flight. The mother ship was a B-50 bomber, its cargo was Bell Aircraft’s X-2 Starburster, and Apt’s challenge that morning was to become the first man to fly at three times the speed of sound.

  The day’s flight was Apt’s first in the X-2. The original flight plan had called for him to keep his speed below Mach 2.45 and focus on flying the perfect flight pro
file, but the speed limit had been lifted in light of the NACA’s pending takeover. And while he’d never flown the X-2, Apt had spent the better part of seven months preparing for the flight. He had studied performance and time data from previous X-2 flights and spent hours in the simulator. He had received multiple briefings on high-speed stability from NACA experts. He had practiced unpowered or “dead-stick” landings in an F-86 to simulate the X-2’s gliding landing from altitude onto the dry lake bed and flown trial flight paths in an F-100 jet aircraft. He had performed ground runs of the X-2’s engine to familiarize himself with its power and had worn his pressure suit for cockpit and failure procedures training in the aircraft. He was ready.

  The Sun rose to reveal another bright and clear day in the Mojave. Shortly after daybreak the B-50 roared to life with its rocket-powered cargo snugly under its belly. The mother ship rose steadily, and at 31,800 feet the X-2 was released. Apt fell away from the mother ship and lit his rocket engine to quickly put a large distance between himself and the two F-100 chase planes monitoring the flight. He passed through Mach 1 at 40,000 feet and managed to fly a nearly perfect profile as he ascended to 72,000 feet where he nosed the aircraft over into a shallow dive. The engine burned slightly longer than anticipated. Apt reached Mach 3.2 before his engine cut out, its fuel used up. He successfully became the fastest man alive.

  All that remained now was for Apt to make his gliding return to the Rogers dry lake bed. He knew from studying previous flights that the X-2 had to slow to below Mach 2.4 before he could safely turn the aircraft back toward the desert air force base; if he didn’t, he risked the aircraft becoming unstable. But he also knew that his high-speed run had taken him quite a ways from Edwards. If he waited for the X-2 to lose speed before turning, he might not have enough energy to glide all the way back to the lake bed. Weighing his options, Apt ultimately decided to begin his return sooner rather than later. He began banking around and pitched his nose up at the same time so the full underside of the aircraft would act as a brake against the atmosphere. But he was still traveling too fast. Apt lost control and the X-2 started tumbling, battering its pilot against the sides and canopy of the cockpit. Subjected to 6 g’s in all directions, Apt briefly lost consciousness before waking to find himself in a subsonic inverted spin at forty thousand feet, the X-2 spinning around its roll and yaw axes in opposite directions. He managed to separate the X-2’s forebody from the fuselage but ran out of time and altitude before he was able to eject from the cockpit and ride his own parachute to safety. Apt was still in the cockpit when it slammed into the desert floor traveling at several hundred miles per hour.

  Apt’s flight was the last of the X-2 program, and the crash was a wakeup call for those pushing aviation into the hypersonic realm that highlighted a much larger issue. Though the problem began with the high speed turn back toward Edwards, the culprit had ultimately been inertial coupling, the sometimes lethal phenomenon wherein the inertia of an aircraft’s fuselage overpowers the stabilizing forces of the aircraft, causing it to tumble. Once it starts to tumble, the pilot can’t do anything to regain control until he reaches denser air. It was the same phenomenon that had nearly claimed Chuck Yeager’s life in the Bell X-1A, and it was a problem that promised to only get worse when aircraft began flying at near-orbital altitudes.

  The same day that inertial coupling claimed Mel Apt’s life, the beginnings of a solution were already taking shape at the High Speed Flight Station. In a large, bright hangar alongside parked aircraft, tanks of compressed gas, and other miscellany was a large cross made of iron girders. Laying horizontally, it sat balancing with its center on a universal truck joint commonly used in automotive drive shafts. The joint acted as a pivot, allowing the cross to move freely in all directions. The strange-looking contraption was meant to replicate an aircraft in flight, the four corners of the cross corresponding to the four corners of an aircraft: the nose, tail, and the two wingtips. A month later, one of the High Speed Flight Station’s newest additions, Neil Armstrong, sat in a seat on one of the girders’ ends facing away from the pivot. In front of him was a board with three instruments displaying the cross’s pitch and bank angles as well as its angle of sideslip showing the aircraft’s angle relative to the oncoming airstream, effectively turning his seat into a rudimentary open cockpit. In his left hand he gripped a standard control stick that unconventionally combined his pitch, yaw, and roll control in one device. The stick was wired to six thrusters on the ends of the cross’s limbs each powered by compressed nitrogen gas. With the flick of his wrist, Armstrong could send the gas shooting out from one of the thrusters, the force of which would move the whole cross on its pivot. Twisting the stick activated thrusters in the forward end of the cross to control sideways motions. Pivoting the stick forward, backward, and laterally activated the thrusters on the other three corners. At the end of each limb was a crash bar designed to reset the test if it hit the ground. Called the Iron Cross Attitude Simulator, for all its simplicity it was the first tool NACA pilots had to learn to fly at near-space altitudes.

  For Armstrong, brow furrowed in concentration and eyes fixed on the instruments in front of him, the Iron Cross was his introduction to a whole new way of flying. He was just three years back from a tour in Korea with the U.S. Navy where he’d flown F9F Panthers, the service’s first successful carrier-based jet fighter aircraft. This single engine straight wing fighter had a central yoke and pedals in the pilot’s footwell for rudder control. It was a standard cockpit layout, one that Armstrong had become familiar with over the course of a flying career that had begun when he’d earned a pilot’s license at sixteen before getting his driver’s license. Now he was learning to fly using only his left hand to control a stick that generated counterintuitive movements. Engineers rigged the Iron Cross such that pitching the nose up meant pushing the stick forward, an input opposite to a traditional stick control. The trickiest part, though, was figuring out how much thrust was needed to get the right response from the thrusters. And the displays weren’t spectacular and hardly correlated to what he could expect in a real aircraft.

  But it was exactly this type of flying that appealed to Armstrong. As early as elementary school he had already settled on aviation as his future career, though he dreamed of being an aircraft designer rather than a pilot. He viewed learning to fly as a means to an end. Understanding what it felt like to fly, he reasoned, could only help him design better aircraft. And so he set off on a self-guided quest to learn everything he could about airplanes, devouring both fiction and nonfiction about aviation. In grade school he built a wind tunnel at home, a project that added to his knowledge of aerodynamics and also taught him how to blow out fuses in his parents’ house. Armstrong’s formal pilot training began after high school when he won a university scholarship through the navy’s Holloway Plan, a program that would pay his tuition fees, buy his books, and give him a stipend for room and board at an approved university in exchange for naval service. He enrolled at Purdue University, but toward the end of 1950 was forced to put his education on hold to serve in Korea. He returned in March 1952 with seventy-eight combat missions under his belt and spent five months ashore ferrying aircraft out of the naval air station at San Diego before leaving the navy to complete his degree.

  Armstrong graduated from Purdue in 1955 with a bachelor’s degree in aeronautical engineering, and he immediately sought employment with the NACA, drawn to the organization’s blend of precision engineering and piloting expertise. His first choice was the High Speed Flight Station at Edwards Air Force Base, the research center where innovating aircraft were regularly flying innovative research missions. But unfortunately for Armstrong, his application ended up circulating among NACA centers before landing at the Lewis Flight Propulsion Laboratory in his native Ohio. Armstrong accepted the position and found himself working on anti-icing systems. Six months later, he learned that a spot had opened up at the High Speed Flight Station with Crossfield’s departure. He packed up and
drove out to the California desert.

  When he first arrived, Armstrong was one of five pilots flying seventeen different aircraft. He began his tenure with familiarization flights, simple missions that would allow him to get the feel of a new aircraft before taking on the specific flight techniques he would follow on data-gathering flights. There were a number of experimental X-planes on Armstrong’s roster as well as a handful of fighter aircraft designed to be flown through extremely precise flight profiles. After every mission, he would turn in the results of his flights to check that they lined up with the results of the veteran research pilots who had flown before him; it was the best way to measure whether or not he was getting the hang of it. He also flew larger planes such as the B-29 Superfortress that had air launched the X-1, a very different kind of aircraft. It was an especially exciting time for the young research pilot to arrive at the High Speed Flight Station, and as he gained experience Armstrong was gradually assigned more demanding missions in increasingly sophisticated aircraft. And training on the Iron Cross was preparation for his first truly exotic flight assignment.

  Though broadly designed to teach pilots how to control an aircraft’s attitude with one hand using reaction controls, the Iron Cross was specifically designed by NACA technicians to match the dimensions and inertia ratios of the X-1B. One of four second-generation X-1s built by Bell Aircraft, the X-1B was originally earmarked for research flights testing the aerodynamic loads on the airframe, but its purpose changed when it was handed over to the NACA. Three hundred thermocouples were installed on the X-1B, and beginning in August 1956 research pilots flew the aircraft on missions designed to gather data about atmospheric heating. But the NACA had plans to fit the aircraft with reaction controls. The Iron Cross was a way for pilots to get the feel for these controls in the safety of a hanger before taking the modified X-1B up into the upper atmosphere.