DEMISE OF THE DYNA-SOAR

It is July 1966. At Cape Canaveral Air Force Station in Florida, a 41-year-old test pilot named Jim Wood is moments away from becoming the United States’ 17th man in space. Alone, pressure-suited and tightly strapped into the tiny cockpit of a stubby winged ship called ‘Dyna-Soar’, he will shortly be boosted by a Titan III-C rocket onto a suborbital trajectory to evaluate the world’s first reusable manned spacecraft. It was a precocious forerunner of the Space Shuttle and, indeed, had it flown, many observers believe that it could have revolutionised – perhaps even ‘routinised’ – today’s space travel.

Wood’s mission never happened. Nor did Dyna-Soar itself reach fruition, although at the time of its cancellation in December 1963 it was supposedly eight months away from performing a series of airborne drop-tests from a modified B-52 bomber. Much criticism has been levelled at then-Secretary of Defense Robert McNamara, accusing him of poor judgement in killing a project with so much promise, so close to completion and whose contractors had already spent nearly half of its $530 million development budget. To be fair, Dyna-Soar faced immense problems of its own, the most important of which was its ill-defined purpose.

The spacecraft was viewed from two different perspectives during its genesis in the late Fifties: as a research vehicle to explore hypersonic flight regimes or, as the Air Force preferred, as a fully functional military glider capable of delivering live warheads with precise, pilot-guided accuracy onto targets anywhere on Earth. Ambitious plans were even afoot for the inspection and maybe destruction of enemy satellites in orbit, as well as the carriage of reconnaissance cameras, side-looking radar and electronic intelligence sensors. Assuming a manned flight sometime in the summer of 1966, it was hoped that Dyna-Soar would evolve into this advanced weapons system by the mid-Seventies. This would offer military strategists a route around the problem that ‘conventional’ ballistic missiles might no longer be able to strike hardened targets with sufficient accuracy. Moreover, the ‘boost-glide’ flight profile of Dyna-Soar – able to cover velocities between Mach 5 and 25 – was perceived as a better alternative to using complex, air-breathing turbojet or ramjet engines, which were difficult to develop and could only operate a lower speeds. Indeed, according to studies conducted by the Rand Corporation, vehicles flying below Mach 9 might be rendered vulnerable to Soviet air defences by 1965.

In the most paranoid days of the Cold War, Dyna-Soar thus provided the United States with a seemingly invincible means of attacking and snooping on enemy targets from any direction and, when flying at low altitudes, gave barely a three-minute warning of its arrival. Additionally, it could sweep across Soviet territory at altitudes in the range of 40 to 80 km, providing a much better imaging resolution than was possible with the best spy satellites and its data could be in the hands of Pentagon officials within hours.

Size-wise, this astonishing machine was a third as large as today’s Shuttle: 10.6 m long, with a wingspan of 6 m. Powered by a Martin-built ‘trans-stage’ engine, capable of 32,660 kg of thrust, it would have ridden into space atop the Titan III-C. This choice of launch vehicle changed significantly as Dyna-Soar’s own purpose fluctuated. ‘‘It was originally scheduled to be launched on the Titan I,’’ said Neil Armstrong, one of its original pilots, ‘‘[then] when the Titan III was introduced, with additional [solid] rocket engines strapped on the side, it [became] an orbital vehicle.’’ Armstrong left the project in mid-1962 to join NASA’s astronaut corps and later revealed that Dyna-Soar’s main aim was for hypersonic research, hence its acronym: the ‘dynamic soarer’. Its 72.48-degree delta wings were flat-bottomed and its aft fuselage was ‘ramped’ to give directional stability at transonic speeds. This would have provided a sufficient hypersonic lift-to-drag ratio to permit a cross-range capability of around 3,200 km. In other words, a diverted landing from Edwards Air Force Base in California meant that it could conceivably touch down anywhere in the continental United States, Japan or even Ecuador.

In fact, thanks to a unique set of wire-brush ‘skids’, it could even land on compacted-earth runways little more than 1.6 km long. Typically, it would have been launched from Cape Canaveral by the Titan III-C, then remained affixed to the rocket’s third and final stage. This would have acted as a restartable ‘trans-stage’, capable not only of inserting Dyna-Soar into a 145 km orbit, but also adjusting its altitude and inclination. The trans-stage could boost its velocity, thus frustrating ground-based efforts to predict its overflight path during bombing or spying missions.

Emergency aborts during a Dyna-Soar launch, though, did not fill Armstrong with confidence. ‘‘There was a question [of] what kind of abort technique would be practical to try to use in case there was a problem with the Titan,’’ he recalled years later. ‘‘It was determined, rather than a ‘puller’ rocket, [we had a] ‘pusher’ rocket to push the spacecraft up to flying speed from which it could make a landing, but it wasn’t known at that time what might be practical, how much thrust would be needed and how much performance would be needed. We had the F-5D aircraft, which I determined could be configured to have a similar glide angle for the Dyna – Soar for similar flight conditions and devise a way of flying the aircraft to the point at which the pusher escape rocket would burn out, so you would start with the identical flight conditions that the Dyna-Soar would find itself after a rocket abort from the launch pad. Then, you only had to work out a way to find your way to the runway and make a successful landing. I worked on that project for a time and found a technique that would allow us to launch from the pad at Cape Canaveral and make a landing on the skid strip. We practiced that and I believe that [NASA test pilots] Bill Dana and Milt Thompson both continued after I transferred from Edwards to Houston. There was a NASA report written about the technique. It was a practical method. I wouldn’t like to have to really do it in a real Dyna-Soar!’’

During its development, the Air Force also hoped to conduct synergistic exercises in which the spacecraft could dip into the upper atmosphere, employ its aerodynamic manoeuverability to change its inclination relative to the equator and refire the trans-stage to boost itself back into orbit. This tricky task was provisionally pencilled-in for the fifth manned test, sometime in the spring of 1967, after which pilots would have begun evaluating its precision-landing capabilities. In the event of trans-stage problems, a solid-fuelled abort motor, derived from the Minuteman missile, was attached to Dyna-Soar and would have separated the pair, performed an emergency retrofire and initiated re-entry. On the other hand, assuming a successful mission had been completed, the trans-stage would have been jettisoned over the Indian Ocean and the spacecraft would commence its long glide through the atmosphere to touch down at Edwards. Later missions, intended to complete two or even three Earth orbits, were expected to fly at higher altitudes of around 180 km. During re-entry, the pilots would test Dyna-Soar’s controllability at various pitch angles during a range of hypersonic and thermal flight regimes.

It was not, however, completely controllable by its pilot throughout the entire speed range and a fly-by-wire augmentation system was provided to run in four automatic modes. A side-arm controller offered him the ability to perform pitch and roll inputs and, through conventional pedals, to execute yaw manoeuvres; the Titan III-C would even have been able to be flown manually during part of its initial boost in orbit! Throughout re-entry, the guidance computer – capable of storing up to ten airfield locations – would have provided continuous updates on Dyna-Soar’s display to advise on issues such as angle-of-attack, banking angles and structural limitations.

Physically, the spacecraft was based on a Rene 41 steel truss, which compensated for thermal expansion within the heated airframe during re-entry. Dyna-Soar was roughly divided into four parts: a pilot’s cockpit, pressurised central section and two unpressurised equipment bays. Each internal compartment was encased in a ‘water wall’ to offer passive cooling during re-entry, allowing their pressure shells to be constructed from conventional aluminium. Additional cooling within each compartment brought temperatures down still further to around 46°C.

In order to withstand the fiery plunge into the atmosphere, Dyna-Soar’s belly and wing leading edges were coated with molybdenum and its nosecap tipped with zirconium. Theoretical predictions expected the wing edges to reach temperatures of 1,550°C, the nosecap around 2,000°C and the belly some 1,340°C during the most extreme re-entry profiles. During all flight phases, the pilot had clear views through two side windows, but the three-piece forward windshield was covered during ascent, orbital operations and most of re-entry. Interestingly, the cover – which guarded against thermal extremes – was not scheduled to be blown off until Dyna-Soar reached a speed of Mach 6, just in time for landing. Tests conducted by Neil Armstrong in the modified Stingray fighter, however, showed that, in the dire eventuality that the cover failed to jettison properly, landings could be safely performed using only the two side windows for visibility. Clearly, this was far from ideal and stands testament to the skills of the men chosen to fly Dyna-Soar: Wood, Armstrong, William ‘Pete’ Knight, Milt Thompson, Al Crews, Hank Gordon and Russ Rogers.

The cockpit in which the pilot would have sat provided all the instrumentation and life-support gear to fly the vehicle, together with an ejection seat which could only be used at subsonic speeds. Behind the cockpit, the central section – pressurised with 100 per cent nitrogen – would have carried a 450 kg instrumentation package, fitted with data recorders for more than 750 temperature, pressure, loads, systems performance, pilot biometrics and heat flux sensors. Finally, at the rear of Dyna – Soar were the equipment bays, containing liquid hydrogen and nitrogen supplies, hydrogen peroxide tanks and power system controls.

The leading contenders for building the spacecraft in the late Fifties were Bell and Boeing, both of which offered the capability to cover the entire requirement range from low-Mach speeds to orbital velocity using a single vehicle. Ultimately, despite Bell’s expertise in designing winged spacecraft of this type, Boeing was chosen as Dyna-Soar’s prime contractor in June 1959. Original plans called for three ‘waves’ of operations: a series of suborbital flight tests, followed by orbital and eventually operational weapons-delivery missions. By the autumn of 1962, critical design reviews of Dyna-Soar’s subsystems had been completed and significant break­throughs achieved in high-temperature materials and fabrication of components for the ‘real’ airframe. Publicly, it seemed worth the wait. When a mockup of the spacecraft was displayed at Las Vegas in September of that year, it quickly grabbed the imagination of America. Writing in Reader’s Digest after the event, John Hubbel

described it as looking “like a cross between a porpoise and a manta ray” and enthused that Dyna-Soar was one of the most important aviation triumphs since the Wright Brothers’ first flight.

Many others agreed with him. The Mercury capsules were blunt and uninspiring in comparison to this sleek, futuristic spaceplane. Despite the public adoration of Dyna-Soar, however, the project was in serious trouble and barely months away from cancellation. Robert McNamara had already expressed serious concerns that it lacked direction or specific purpose – the Department of Defense regarded it as a hypersonic research vehicle, the Air Force as a strategic bomber – and very little attention had been paid to precisely what missions it would undertake. McNamara made his opinions clear during a series of reviews of the project during the course of 1963, before ultimately cancelling it at year’s end in favour of a military space station called the Manned Orbiting Laboratory. Ultimately that, too, wasted millions of dollars and never bore fruit.

More than four decades later, Dyna-Soar is recognised as an ambitious, far­sighted endeavour, literally at the cutting-edge of the technology of its day. Its legacy remains visible in many elements of the Shuttle’s design and capabilities – from the concept of the ‘rocket-glider’ to the payload bay, from landing on pre-determined runways to its reusability – and its extensive wind-tunnel testing provided valuable engineering data for later projects. In the words of a recent NASA study of the X – planes, of which Dyna-Soar was one, ‘‘very few vehicles have contributed more to the science of high-speed flight – especially vehicles that were never built!’’