8
The X-Men
America’s first civilian astronaut never flew aboard a spacecraft. On 19 July 1963, Joe Walker took his rocket-powered aircraft above a height of sixty-two miles (one hundred kilometres) – the so-called Kármán line – which by some definitions marks the boundary between Earth’s atmosphere and outer space. The plane was the North American X-15, and Walker was among a select group of individuals to fly aboard one of the extraordinary X-series of planes. Another X-plane pilot was the first human to travel faster than sound, Chuck Yeager.
The first X-plane (X for ‘experimental’) was conceived in 1944, at the tail end of the Second World War, by the US Army Air Force and NACA (National Advisory Committee for Aeronautics) – the forerunner of NASA. Its goal was straightforward: to break the sound barrier. Bell Aircraft Corporation was given the contract to build the plane, and at the end of 1945 handed over the first Bell X-1 for testing.
The X-1 was designed to travel as fast as a proverbial ‘speeding bullet’, so it made sense that it should be shaped like a bullet with wings. The fuselage was modelled after a Browning .50-calibre machine-gun bullet, which was known to be stable in supersonic flight. No bulges – such as a bubble cockpit – were allowed, so the pilot had very poor visibility. In fact, from where he sat, he had no view at all to the rear and only a very poor view looking forward, given the gentle slope to the nose and the bank of dials and switches that were piled high in front of his face.
20 The Bell Aircraft Corporation X-1 with shock-wave pattern visible in its exhaust plume.
There was also a problem of how to escape from the plane if something went wrong as the bullet shape didn’t provide enough room for an ejection seat. There was a little side hatch that the pilot could squeeze out of in a dire emergency. But he would have to be pretty desperate, because right behind the hatch was the wing, and if by some miracle he missed that then he’d likely be thrown up into the tail. Given that the choice was between staying with the plane or ending up as mincemeat, it’s no surprise to hear that the X-1 programme didn’t see a single bail-out.
As far as propulsion went, the X-1 was all rocket. The rocket motor had four chambers and there was a choice to fire one or more chambers at a time, but once they had been ignited that was it: they would burn full on until all the liquid fuel was used up or they were shut off completely (rockets that could be throttled came later). At maximum thrust, with all four chambers firing, the X-1 had just two and a half minutes of power. To save its precious fuel for boosting it to record-high speeds, rather than the mundane tasks of getting off the ground and climbing the first twenty-odd thousand feet, the X-1 was carried aloft by a B-29 Superfortress and mated to its mothership by a standard heavy-duty bomb shackle.
Onwards and upwards
The name Charles ‘Chuck’ Yeager is synonymous with the Bell X-1 and the smashing of the sound barrier. But he wasn’t the first to take the controls of the flying bullet. That honour went to Bell Aircraft’s chief test pilot, Jack Woolams. In September 1942, although only in his late twenties, Woolams had already become the first person to fly a fighter non-stop from coast to coast across the United States and, the following summer, had cracked the world altitude record for an aircraft, reaching 47,600 feet.
Woolams was a consummate prankster. During the war he was at the Materiel Command Flight Test Base (later part of Edwards Air Force Base), California, putting the new Bell XP-59A through its paces. This was America’s first military jet and a hush-hush project, so that when it was towed from its hangar to the run-up area, a fake propeller was attached to the nose to disguise its true nature. Still, Woolams couldn’t resist the opportunity for a practical joke, even if it meant breaching security. During a daylight XP-59A mission in autumn 1943, he noticed a Lockheed P-38 Lightning from a nearby training unit flying in the same area. Taking off his flight helmet, he slipped on a furry mask and short-brimmed hat, and eased the jet alongside the P-38. The Lightning’s pilot must have got the shock of his life when he saw the sleek, propeller-less plane, barely twenty feet away, being flown by what appeared to be a gorilla in a derby hat – waving a cigar.
In January 1946 Woolams found himself in a very different situation. He was 8,000 feet up in a B-29, climbing down a ladder and into the tiny cockpit of the Bell X-1 nestled partly inside the bomber’s dark underbelly. At 28,000 feet the countdown to launch began and, at zero, the small rocket plane was released into the dazzling light of day for its maiden flight – an unpowered cruise back to Pinecastle Army Airfield near Orlando, Florida. Nine more such outings followed before the first X-1 was taken back to Bell Aircraft for some modifications. A new series of tests was to begin in September 1946, but they would be flown by another pilot.
At the end of August, Woolams was flying over Lake Ontario in a Bell P-39 Airacobra – a single-seater that had been one of the most successful American fighter aircraft of the Second World War. He was preparing for the upcoming National Air Races in Cleveland, and nudging the P-39 up towards 400 miles per hour. Suddenly and inexplicably it went out of control, plunging into the water and breaking up on impact. Woolams’s body was recovered four days later.
21 Chuck Yeager standing alongside the Bell X-1, which he nicknamed ‘Glamorous Glennis’ after his wife.
The Bell X-1 tests resumed, but by the following summer the air force had grown impatient with the progress of the project. Bell Aircraft were running what the brass considered to be too slow a build-up to the assault on Mach 1 – the speed of sound. Bell’s contract for testing was cancelled and responsibility for going through the sound barrier was handed to the Army Air Force Flight Test Division (the ‘Army’ part of that title was soon to be dropped as the US Air Force became a separate service in September 1947). The new chief test pilot was Charles ‘Chuck’ Yeager, a Second World War veteran blessed with astonishingly acute 20/10 vision (which once enabled him to shoot a deer at 600 yards). During the war, he was the first pilot in his P-51 Mustang group to ‘ace in a day’, accounting for five enemy planes in a single mission. He was also one of the few Allied pilots to shoot down a German jet, a Messerschmitt Me 262.
Through the barrier
After a couple of months flying the X-1, Yeager was nudging it very close to the sound barrier. At speeds of Mach 0.95 – ninety-five per cent of the speed of sound – the plane was getting buffeted a lot by the turbulent air piling up around it. No one quite knew what was going to happen when the aircraft finally went supersonic, because there was no useful wind-tunnel data. Models had been put in wind-tunnels and subjected to air moving at supersonic speeds but the shock that formed on the models at about Mach 0.9 would simply bounce off the walls and block the air flow. So what happened between about ten per cent below the speed of sound and ten per cent above it was more or less a mystery.
The term ‘sound barrier’ first came into use during the Second World War. Fighter pilots who made high-speed dives noticed several irregularities as flying speeds approached the speed of sound: aerodynamic drag increased markedly, much more than normally associated with increased speed, while lift and manoeuvrability decreased in a similarly unusual way. Pilots at the time mistakenly thought that these effects meant that supersonic flight was impossible; that somehow planes would never travel faster than the speed of sound.
Tuesday 14 October 1947 was the date earmarked for Yeager’s next Bell X-1 flight. Although there was no set goal of trying to go supersonic on that day, a sense of anticipation was growing among everyone involved with the project, given how close the plane had been flirting with the barrier. But on the Saturday before the flight, Yeager and his wife Glennis were out horseback riding when Yeager hit a fence that had been closed across a road; he was thrown off his horse and ended up cracking two ribs. Rather than let the flight surgeon know about his injury and risk being grounded, Yeager and his buddy Jack Ridley decided to try a work-around. Flying the plane wasn’t going to be a problem. The snag was that, with his injured right side, Yeager wouldn’t be able to close the cockpit door with his right arm. The solution: Ridley sawed off a ten-inch length of broomstick so that Yeager, once in the pilot’s seat, would have enough leverage to push the locking mechanism closed.
With the B-29 at 8,000 feet, Yeager climbed down into the 250-miles-per-hour ice-cold slipstream, bending double and climbing painfully into the dark little cockpit. A few minutes later came the drop into the blinding light of day, and then a wild ride into the history books. Yeager fired off all four engine chambers, climbed to 35,000 feet, turned off two of the chambers, and continued to climb to 42,000 feet before levelling off and reigniting the third chamber. With the machmeter showing Mach 0.92 he experienced the usual buffeting; at Mach 0.97 the needle suddenly jumped off the scale (the maximum value marked on it was 1.0). At first, Yeager thought the instrument was faulty and radioed ‘it’s gone kinda screwy on me’. On the ground, a loud bang was heard – not the X-1 breaking up but breaking through the sound barrier. Suddenly the buffeting stopped and Yeager took the rocket plane up to Mach 1.07 (about 650 miles per hour) before gliding back to base and the congratulations of a select handful of people who knew about the achievement. The X-1 project was classified and news that the sound barrier had been crossed wasn’t made public until June the following year.
Danger at Mach 2
With supersonic flight now a reality and fears about the sound barrier blown away, there was a major push to move on to much higher speeds. The research was important to the field of aerospace as a whole and the development of new, high-performance fighter planes in particular.
Even as work began on new X-planes – such as the Bell X-2 rocket plane, with its swept (angled-back) wings; and the incredibly slender, jet-powered Douglas X-3 Stiletto – the original Bell X-1, which eventually reached 1,000 miles per hour, evolved into a number of variants. On 12 December 1953 one of these, the Bell X-1A, was piloted by Yeager to another speed record – Mach 2.4. But on this occasion events threatened to get seriously out of hand and only Yeager’s experience managed to save the day.
The X-1A was about seven feet longer than the old X-1 and carried almost twice as much fuel so that it could accelerate for much longer. After three flights, Yeager had already cranked the new plane up to Mach 1.9. The fourth flight started well with a good drop and all four rocket chambers firing, powering the plane on a steep climb through 60,000 feet, 70,000 feet, and on up to 80,000 feet. By now the X-1A was passing Mach 2.3, gaining another thirty miles per hour every second. Suddenly, the plane started to yaw, its nose drifting to one side. Yeager responded by pushing the rudder to try to get the nose back in line, but it had no effect. The yaw got worse, and then the outside wing began to rise. The situation quickly became desperate. The aircraft rolled until it was flying upside down, pitched up. The stress on the cockpit canopy was too great and it split open, exposing Yeager to the cold, thin outside air, and causing his pressure suit to inflate.
The X-1A was rolling ferociously, as if it were the most vicious corkscrew roller-coaster you could imagine, rotating twice around per second, and putting Yeager through a withering 9g. Ground and sky flashed by in dizzy succession but, crucially, Yeager stayed conscious and alert to what was happening with the plane. As the X-1A ran out of fuel it slowed, and the rolling stopped. Yeager saw the sky ‘below’ him and the horizon going round and round, and realized he was in an inverted, flat spin, pulling negative g’s – not ideal, but at least he knew what to do about it. Test pilots are as used to spinning planes as test drivers are to making handbrake turns, and they know exactly how to make them stop: set the aileron (the hinged flap on the trailing edge of each wing) with the spin direction, apply the rudder, then fall out of the spin. It worked. The whole ordeal, from the time that the aircraft started to yaw at 80,000 feet until Yeager popped out of the spin at 25,000 feet, lasted a mere 51 seconds, but contained enough stomach-churning action and danger to last most ordinary mortals a lifetime. Throughout it all Yeager had had to contend with a smashed canopy, exposure to the sub-Arctic cold of high altitude, and a bulked-out, inflated pressure suit. But now he was as good as home. Looking around, he spotted his landing site, Rogers Dry Lake, about fifty miles away and glided on back to base. The X-1A had made its first and only excursion above Mach 2.
At the edge of space
Of all the dozens of other X-planes that have been built – and continue to be built – only one, the X-15, has achieved a similar, legendary status to the X-1. It too was a rocket plane, but instead of peaking out at two and a half times the speed of sound, it eventually reached more than Mach 6 and flew so high that, for minutes at a stretch on some missions, it was not an aircraft but a spacecraft plunging through the near-airless void fifty or sixty miles above the ground. Thirteen flights of the X-15 by eight different pilots met the US Air Force’s criterion for a spaceflight and earned their pilots the right to be called astronauts.
22 Neil Armstrong next to the X-15.
The X-15 was a collaborative project between the US Air Force and Navy, and NASA. With an airframe built by North American Aviation and an engine supplied by Reaction Motors, the fifty-foot-long plane was the first to be designed specifically to cope with the unusual demands of hypersonic speeds – those above about Mach 5.5. The wedge-shaped tail surfaces were to give directional stability at speeds where aerofoils of a more conventional shape wouldn’t have been effective. The large upper and lower fins, and the downward slant of the stubby wings, were intended to keep the aircraft stable during steep climbs and at high altitudes.
Stability was only one of the big challenges of hypersonic flight. Another was overheating caused by friction with the high-speed air. Designers knew that some parts of the plane, like the nose and wing edges, would reach temperatures above 650 degrees Celsius. So they needed a metal that would maintain its strength at that heat. In the end, they chose titanium with a covering of an incredibly tough, heat-resistant nickel-chromium alloy called Inconel X.
Like the Bell X-1, the X-15 was carried up by a mothership, a giant B-52 bomber, to an altitude of 40,000 feet. After being released, its powerful rocket engine fired for about 85 seconds, burning up to 15,000 pounds of fuel in that time, and pushing the plane and its pilot to accelerations of as much as 4g. From drop to landing, an entire flight would last about twelve minutes.
Among those who flew the X-15 was Neil Armstrong, the first man on the Moon. Less well known is Joseph Walker, a NASA test pilot who can claim another remarkable record – the first man to fly into space on two different occasions.
23 Joe Walker exiting his X-1A, cowboy style.
A veteran of the Second World War, Walker had been raised on a farm in Pennsylvania and showed an engineering talent and a thirst for knowledge early on. After the war, he joined NACA’s Aircraft Engine Research Lab in Cleveland, Ohio as an experimental physicist, and later became a test pilot at the Edwards Flight Research Facility (now Dryden Flight Research Center) alongside Edwards Air Force Base. There he flew a variety of experimental aircraft, including the X-1 and its variants, and later X-planes.
In 1958, Walker was picked to take part in the US Air Force’s Man In Space Soonest programme, aimed at putting an American in space before the Soviet Union. The programme was cancelled after a few months and replaced by NASA’s Project Mercury. Only two men from the Man In Space Soonest programme would go on to reach space – Neil Armstrong and Walker. These two were also among the select few to pilot the Lunar Landing Research Vehicle (LLRV), a notoriously hard-to-fly contraption used to simulate the descent of the Apollo Lunar Module onto the surface of the Moon. On 30 October 1964, Walker was the first to lift off in the LLRV, taking it for three flights lasting a total of just under a minute to a peak altitude of ten feet.
In 1960, Walker became the first NASA pilot to fly the X-15, and the second X-15 pilot of all, after Scott Crossfield who ran initial tests on behalf of the manufacturer, North American Aviation. On Walker’s maiden outing in the X-15, he was shocked by the plane’s brutal acceleration. Having just ignited the engine he was crushed back into his seat, yelling ‘Oh, my God!’, to which the flight controller calmly replied, ‘Yes? You called?’
Walker went on to fly the X-15 a couple of dozen times – twice in succession in 1963 to heights of more than 62 miles (100 kilometres) which, in the eyes of both the US Air Force and Fédération Aéronautique Internationale (FAI), counts as the edge of space. On 19 July he peaked out at 65.8 miles (105.9 kilometres), and a month later bettered that by going to 67 miles (107.8 kilometres), travelling at a speed of over 3,700 miles per hour on both occasions. The first of these flights made Walker the first US civilian in space and the second civilian astronaut in history after the Soviet Union’s Valentina Tereshkova (who wasn’t in the military at the time of her trip into orbit); the second flight made him the first person to go into space twice (according to Air Force and FAI rules). No manned plane would beat Walker’s X-15 record altitude until Virgin Galactic’s SpaceShipOne soared to over sixty-nine miles in 2004.
24 Joe Walker after a flight of the X-15 #2.
On 8 June 1966, Walker was flying an F-104 Starfighter in tight formation with other high-performance planes for a US Air Force publicity photo. He was trying to maintain position just below, and seventy feet to the side of, an XB-70 Valkyrie prototype bomber. At some point he misjudged where he was, and may also have flown into the wake vortex of the other plane. In any event, his Starfighter drifted too close to the XB-70’s right wingtip, made contact with it, and flipped over. Rolling inverted, the Starfighter passed over the top of the bomber, smashed into its vertical stabilizers, and exploded, killing Walker instantly.