The space plane that wasn't: everything you never needed to know about Dyna-Soar | Popular Science
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Vintage Space

Exploring the history of space-age efforts that never got off the ground. By Amy Shira Teitel

The space plane that wasn't: everything you never needed to know about Dyna-Soar

A couple of weeks ago I gave a talk at NASA's Goddard Spaceflight Centre about one of my all-time favourite projects that wasn’t: Dyna-Soar. A lot of people asked if I was going to put a video of the talk online, but I don’t think anyone necessarily wants to watch that awkward video. So instead, here’s a tightened version of the talk, and fair warning it's long, but broken up with videos and images! If you do want more details on the story, it's teased out in a lot more detail in my upcoming book, Breaking the Chains of Gravity, that you can pre-order now on Amazon!

I first came across Dyna-Soar when I was a teenager. I’m not sure how I found it but I was instantly fascinated because it seems to occupy a really strange spot in the history of spaceflight. It looks like a spaceplane, it was designed on the heels of the X-15, which is arguably the world’s first space plane, and it predicted the design of the space shuttle. So why didn’t it fly?

Hermann Oberth


Of all the places to start Dyna-Soar’s story, Hermann Oberth is as good as any. When he was 14 recovering from Scarlet fever in Italy, Rumanian future scientist read Jules Verne’s From the Earth to the Moon. The French novel tells the story of a group of men from the Baltimore Gun Club who build a giant cannon to shoot themselves in a train-like vehicle to the Moon. Oberth recognized that the story was fantastic but not impossible, though the Gun Club’s use of black powder was inefficient. Liquid propulsion, he knew, was the best way to get to the Moon, and so he designed his first rocket called a recoil rocket that moved through space by expelling exhaust gases from its rear end.

Oberth briefly flirted with a career as a physician during the First World War before switching his field of study at the University of Munich post-war to mathematics and physics, which allowed him to self-specialise in rocket propulsion. His work culminated in a doctoral dissertation expounding the virtues of liquid propelled rockets and their application for spaceflight that was poorly received by his advisers. They agreed that the material in his paper was astonishing but failed to meet the requirements for a degree in classical physics.

Undaunted, Oberth took his rejected thesis around to publishers and finally found a small press willing to print the volume. The Rocket into Planetary Space reached German bookshelves in 1923, and though less than 100 pages long it was so loaded with complex diagrams and calculations that it brilliantly alienated the casual reader. But it did draw in rocket enthusiasts, among them Eugen Sänger.

Eugen Sänger

via Astronautix

Sänger was inspired by Oberth to study liquid propelled rockets for spaceflight and also self-specialized in rocketry during his own doctoral degree. And also like Oberth, Sänger’s 1931 dissertation on rocket propulsion presented at the Technical University in Vienna in 1931 was rejected on the grounds that it was too fantastic to be plausible.

But like Oberth, Sänger was undaunted. He imagined a future where commercial flights would carry passengers and cargo through the upper stratosphere about 30 miles above the planet’s surface to reach any point on the globe within an hour of launching. Hoping to see this future come to pass, he designed a spacecraft.

At the heart of Sänger’s system was a vehicle roughly 90 feet long with a wingspan measuring close to 50 feet across. More of less cylindrical until it tapered to point at the front end with small wings, the vehicle also had a flat underside, which is where his system gets interesting. Sänger theorized that if this vehicle could be launched to a high enough altitude, it could bounce off the atmosphere as it descended from its peak altitude much like a stone skips across a calm pond, following an oscillating flight path as it glided to an eventual runway landing.

Where Sänger needed rocket power was to get the glider up to that high altitude. The launch system Sänger imagined used a sled on an angled monorail track so the launch would be more horizontal than vertical, ensuring the right ballistic trajectory and also offering a more comfortable flight for future passengers. The sled’s rockets would propel the glider off the ground, and once it was airborne the glider’s own rocket engine would ignite, kicking it up towards its peak altitude burning even available ounce of fuel along the way. Once the engines burnt out, momentum would take it the rest of the way, climbing a little higher until gravity took over and started the vehicle on its skipping and gliding descending flight path.

The antipodal bomber in flight

Mario Merino in Myhra's "Sänger"

From this first suborbital version, Sänger imagined adding more rocket power to eventually get the glider into orbit, turning it into the world’s first spacecraft. All that was missing was the necessary propulsion system, which was unfortunately not something he could develop without a laboratory space and some funding. And so he turned to the military in search of sponsorship.

Knowing the military wouldn’t be keen on a transportation system, Sänger added weapons and turned his boost-glide vehicle into a manned, long-range bomber that he called the antipodal bomber. As a weapon, he imagined the vehicle flying two basic mission types. The first was a point attack, a precision technique that would have the pilot release his bomb or bombs from a moderate altitude while flying at a moderate speed. Timed just right, he could destroy a bridge, a building, or effectively block an entrance to a tunnel in one fell swoop. The second type of mission was an area bombing attack that basically swapped precision for power. Designed to destroy or at least heavily damage a large area like a city, this type of attack had the pilot drop his bomb from altitudes as high as 100 miles while flying at a much faster speeds. Either mission type would end with the pilot gliding to safety or ditching the plane and landing by parachute.

Sänger first took his antipodal bomber idea to his native Austrian army, but it wasn’t well received; the Austrian National Defence Ministry said it couldn’t seriously consider the skip-glide system because Sänger had designed it with a liquid oxygen and hydrocarbon combustion system, a poorly understood chemical reaction that came with a high risk of explosions. A year later, he took the antipodal bomber to the German military, but it too wasn't interested. For one, Sänger wan’t German-born, and a requested security check into his background submitted to the SA went unanswered. Another strike against him was that Germany already had a rocket expert on hand already; Wernher von Braun had been building rockets for the army for a little less than two years at this point.

The German army passed on Sänger’s potentially duplicative work but urged him to take it to the Luftwaffe, which he successfully did. The Luftwaffe had no problem with Sänger’s Austrian background or with any similarities his technology bore to von Braun’s. In 1936, he was recruited to become a member of the Research Division of the Technical Office of the Göring Institute, joining the aeronautical research laboratory it was planning to build near Braunschweig in north-central Germany. The appointment also came with an influx of funding to establish a rocket research facility at Trauen, which was given the cover name of Aircraft Test Centre to hide its existence as much from the army as from the public.

Part of the Luftwaffe’s motivation for giving Sänger a lab was to not be outdone by the army and all the resources it was sinking into von Braun’s rocket program that was taking great strides towards the operational Aggregate 4 or A-4 rocket. The army’s site at Peenemünde was substantial, so Göring sunk almost 8 million Reichmarks into Sänger’s lab at Trauen and the winged bomber project.

But Sänger didn’t thrive during the war like von Braun did. His laboratory at Trauen had failed to keep pace with the developments at Peenemünde and was closed in the summer of 1942 under the guise of staff conflicts and fuel shortages. But Sänger never abandoned his antipodal bomber. In 1944, as the war was turning against Germany’s favour, he and his partner, mathematician Irene Bredt, cowrote a full proposal called “A Rocket Drive for Long Range Bombers” and began quietly circulating it around scientific circles but ultimately failed to garner new interest in the system. The country was in financial and physical ruins. There was just no money kicking around to bring a futuristic technology to life.

But two copies of Sänger’s proposal did land in historically interesting hand. One was Soviet Premier Joseph Stalin who was completely enthralled by the idea of bombing an enemy like the United States without having to send troops into the country. After the Second World War ended, Stalin had his men on the hunt to find Sänger and Bredt, but he never caught them.


German Federal Archive

The second pair of interesting hands to find a copy of Sänger’s report was Walter Dornberger, leader of the German army’s rocket program and direct superior to Wernher von Braun.

Dornberger did not make Wernher von Braun’s shortlist of 124 men he brought into the United States with him under Operation Overcast and Project Paperclip. When von Braun began his exodus to the New Mexico desert, Dornberger was among 85 Germans taken by the British to assist in Operation Backfire, a British program to evaluate and study the V-2. But he didn’t stay with his former colleagues very long. After first being isolated from his men for fear he would incite rebellion among them, he was then sent to London ostensibly for further interrogation but was actually taken in as a prisoner of war. From there he was sent to the infamous London Cage to stand trial for warcrimes in Hans Kammler’s stead; the high-ranking SS man had disappeared. But he was never tried, and instead was eventually transferred to the Bridgend Prisoner of War camp in South Wales where he spent two years theoretically contemplating the atrocities he committed against Britain.

Dornberger was finally released in 1947 and soon immigrated to the United States where he first served as an advisor to the US Air Force on Guided missiles, then left for a job with Bell Aircraft in 1950. Finally, working with a peacetime army and a contractor whose interests went beyond building weapons, Dornberger rehashed the idea of Sänger antipodal bomber, pitching it to Bell Aircraft chief engineer Bob Woods as something that could double as a sophisticated weapons system and a research aircraft.

In January of 1952, Woods issued a memo to the National Advisory Committee for Aeronautics proposing a hypersonic research program. Accompanying this memo was a letter from Dornberger outlining a progressive plan culminating in orbital flight. In Dornberger’s mind, it was only a matter of time before rocket engines made their way into commercial aircraft to create something he called ultra planes.

Dornberger’s ultra planes were a two-part vehicle consisting of a passenger glider mounted on the upper fuselage of a piloted booster. Before launch, the glider would slide into place along rails on the booster’s back, giving the appearance the the booster was giving the glider a piggy back ride. The mated booster-glider stack would be flipped on its end so their noses would be pointing skywards, then the pair would be mounted on a launch platform sitting on rails where they would be fueled. The vehicles would then travel along these rails from the hangar through a massive concrete passageways called canyons, and from those canyons into a large, circular, concrete launch area.

Passengers, meanwhile, would arrive at the airport, check in for their flight, then find their gate. From there, shuttle buses would take them to a point along the canyon leading to the launch area where an elevator would take them 20 feet into the launch crater walls where a gantry would grant them passage into the glider’s cabin. The glider’s main cabin, they would find, would be divided into smaller units with seats mounted to swivel freely to keep passengers upright at all times. There would be no inflight service on ultra plane flights; the fuel penalty of carrying flight attendants and food was just too much.

With everyone on board, the ultra plane would finish its railway journey into the middle of its circular launch pit. With its wings facing into oncoming wind to limit turbulence, the booster’s five rocket engines would ignite delivering 760,000 pounds of thrust to send the vehicles shooting into the sky. After two minutes, it would be time for staging. The glider pilot would activate a release mechanism and the small vehicle would slide off the rails on the booster’s upper fuselage. The booster’s pilots would guide the larger vehicle back to the airport for a runway landing after which it would be readied for another launch. The glider, meanwhile, would continue towards its destination.

Clear of the booster, the pilot would ignite the glider’s rocket engines that would propel it to more than 140,000 feet above the Earth faster than 8,400 miles per hour. Momentum would carry the vehicle higher after the engines cut out. Gradually, the glider would lose altitude, gliding silently to its destination airport as passengers enjoyed the sensation of lightness while taking in the stars shining against the blackness of space.

Dornberger’s knew that the first ultra plane flights would, by sheer cost of the venture, be reserved for the wealthy and social elite, but eventually intercontinental travel would be dominated by rocket planes. He also knew that before this future could come to pass there were some major technical hurdles associated with the return flight from near orbital altitudes that needed to be overcome, and this is where Bob Woods’ hypersonic program comes in. Aerodynamic heating and vehicle structure were foremost among the problems facing not just Dornberger’s ultra planes but any vehicles designed to fly up to 20 times the speed of sound. The friction these ultra planes would experience while gliding hypersonically through the increasingly thickening atmosphere from near space would heat the fuselage to dangerously high temperatures. Engineers would need to develop some new cooling method or even new materials to withstand this intense heat.

The call for a hypersonic research program finally gained traction in 1954, though it wasn't for something quite as futuristic as the hypersonic space plane. The first iteration was the X-15 rocket-powered aircraft designed to fly at speeds up to Mach 7 at altitudes up to 250,000 feet, the first step in understanding hypersonics.

Next steps were closer to Dornberger and Bell’s original idea picking up where the X-15 left off. One was called BoMi for Bomber Missile. Another version called Brass Bell was a dedicated reconnaissance vehicle. ROBO stood for Rocket Bomber, a version ultimately investigated by Douglas Aircraft, Convair, and North American Aviation in the mid-1950s. Another Air Force incarnation was Project HYWARDS, an acronym for hypersonic weapon and research and development system, that surfaced in 1956. It was also known as weapons system 464L, which eventually took on the nickname Dyna-Soar in reference to its dynamic soaring landing profile.

Dyna-Soar on a Titan II


But in any incarnation, the boost-glide profile was still a futuristic technology in need of a methodical program, which suited military and industry partners just fine; in the mid-1950s there was no need to fast track anything like a spacecraft. Instead, proposals focused on slowly building capabilities. One 1957 proposal called for a three-phase program wherein Dyna-Soar I would be the conceptual test article, Dyna-Soar II would be a reconnaissance version like Brass Bell, and Dyna-Soar III would be a bomber version similar to ROBO concept.

However ill defined, the boost-glide vehicle was on the docket as a ‘piloted very high altitude weapons system,’ but everything changed when the Soviet Union launched Sputnik on October 4, 1957.

A little over a week later on October 15, a long-planned NACA conference began at the Ames research laboratory in California. Called the Round Three Conference, it was set up to discuss the next phase of high-speed flight research — the first round having been breaking the sound barrier with the X-1 and the second round edging into hypersonic with the X-15. The third round was expected to push into space, and the fundamental question became what that vehicle would look like. And Dyna-Soar was one option back on the table, an Air Force project with supporting wind tunnel research from the NACA’s Langley laboratory intended to explore the potential of a flat bottomed delta wing boost-glide vehicle capable of reaching speeds as high as Mach 18.

In January of 1958, the Air Force invited the NACA to participate in what was then called the “multipurpose manned bomber” program. Months of negotiations ended with shared responsibility that would see both parties playing to their strengths: the Air Force would focus on the vehicle’s weapons while the NACA would research and develop a sound aerodynamic design. By the end of 1958, NASA had taken the place of the NACA, absorbing ongoing programs in the process. And Dyna-Soar survived. A two-stage program was in place for a boost glide research vehicle proceeding a weaponization system.

The Dyna-Soar mockup


Unfortunately, this clearcut plan didn’t last as the multipurpose manned hypersonic bomber program underwent multiple revisions in 1959. In February, the bombardment system was upgraded to a primary goal over any non-military applications. In April, the situation was reverse with the suborbital hypersonic flight taking over as the program’s main objective. In May, things were switched back and any development and focusing only on research was cancelled in favour of a determination of the boost glide system’s military potential.

The program started taking firm steps in November of 1959 when a contract for the glider’s construction was awarded to Boeing Aircraft and a contract for the booster awarded to the Martin company. As these contracts were formalized, more revisions were brought into the program, including the addition of another full research stage by the end of the year, Phase Alpha, intended to determine whether Dyna-Soar could be an orbital spacecraft.

From these positives steps, things looked good for Dyna-Soar at the start of 1960. The Air Force completed Phase Alpha in March and determined the vehicle was well suited to manned spaceflight, officially clearing the vehicle for suborbital flight testing. Things got even better midway through the year when the Department of Defence officially endorsed Dyna-Soar, an endorsement that came with financial support for the program through stages 2 and 3, the orbital stages. At this point, the Air Force wanted to build on this momentum, accelerating the program and moving the launch schedule up, but the rocket remained the missing piece of the puzzle.

But things still looked good. After the Soviet Union put Yuri Gagarin into orbit in April of 1961, the Department of Defense announced its commitment of $100 million – a little over $720 million in 2010 – to the USAF for the fiscal year 1962 for the Dyna-Soar program. Funding was secure for another year, industry contracts were finalized, and unmanned demonstrations were cancelled to fast track manned orbital flights.

In September, a delegation of US Air Force and NASA representatives travelled to Boeing’s plant in Seattle to inspect a mockup of the glider, and while things looked good for Dyna-Soar it was under intense scrutiny from USAF General Bernard A. Schriever. He called for a study into the military and space capabilities of the glider and found that these two goals should be separated, that the military and space-faring versions should be entirely separated from one another with the former version taking precedence.

It was around this time that pilots started getting into the Dyna-Soar program, most notably Neil Armstrong, who was charged with coming up with some launch abort procedure should the rocket beneath the manned glider explode on the launch pad. In launch configuration, the pilot would be just 100 feet off the ground inside the Dyna-Soar whose nose was facing skyward, which meant that the pilot was lying on his back relative to the ground. It was an orientation that ruled out ejection. Ejecting laterally from 100 feet off the ground, a parachute wouldn’t have enough time to open before the pilot hit the ground.

So Armstrong focused on using Dyna-Soar’s engine and aerodynamics as a pilot’s chief ally in escaping an exploding rocket. Knowing the engine could accelerate the glider 1,000 feet every 10 seconds, he figured he could quickly fly to a safe altitude that would give him plenty of time to find the ground and guide Dyna-Soar to a safe landing.

Without a flight ready Dyna-Soar, Armstrong used an analogue to run through this launch abort procedure, the Douglas Skylancer, which, lightly modified, had about the same aerodynamic qualities as the Dyna-Soar. The vehicle sorted, he went to the program’s planned launch site at Cape Canaveral to measure the lengths and distances of possible runways from the launch pad. Back at Edwards, he reproduced the launch pad and runways on the dry lakebed, a square representing the runway and a square representing the launch pad. Then he got into the Skylancer to fly.

Flying about 200 feet above the ground at nearly 575 miles per hour, Armstrong pitched the aircraft up over the drawn-on launchpad to enter a steep vertical climb, pulling 5 gs as he flew straight up to an altitude between 7,000 and 8,000 feet. Then he arced the aircraft over, rolled it upright, got a visual on his sketched out runway, and guided the aircraft to a smooth landing. It was an effective but difficult maneuver, one Armstrong later confessed that he was happy to never try in a real Dyna-Soar.

Though the human side of Dyna-Soar was coming together, the program on the whole was starting to lose momentum. Early in 1962, the Air Force cancelled all development towards stage III, the multi-orbital phase of the program. Suborbital flights were next to go following a recommendation from Boeing. Then the military version of Dyna-Soar was cancelled. By spring, the hypersonic boost-glide vehicle had been restructured into nothing more than an orbital research program. This amendment was formalized in June when the DOD gave Dyna-Soar its secondary designation of X-20, putting it squarely in the growing list of experimental X-planes that would inform but never become large-scale production vehicles.

A full-scale mockup of the Dyna-Soar-turned-X-20 was unveiled at a press conference in Las Vegas in September of 1962 with the accompanying announcement that the DOD was funding the program with $130 million for 1963 and $125 million in 1964. But the good news was short-lived.

By 1963, NASA’s Mercury program was taking great strides having put two men into orbit on increasingly lengthy missions that were also answering questions earmarked for Dyna-Soar, namely questions of aerodynamic heating and human response to being in orbit. And the agency was also by this point firmly committed to using capsules for the Apollo lunar landing program. There was no way a Dyna-Soar-type vehicle would supersede the ballistic-type Apollo spacecraft already under development.

Because Dyna-Soar didn't factor into the nation’s success in the space race, it was subjected to yet another US Air Force mandated review in March of 1963 alongside a review of NASA’s Gemini program, comparing the military potential of both systems. Dyna-Soar just didn’t have a place, and in December of 1963, McNamara formally announced its cancellation. The decision, he said, boiled down to a poor return on investment. By that point, Dyna-Soar had cost close to $400 million (over $2.8 billion in 2010) and still didn’t have a firm mission or even a clear reason for being. In its stead, the Air Force would pursue a larger, militarized version of the Gemini spacecraft called Gemini B or the Manned Orbiting Laboratory.

It’s not too hard to see that the odds were never in Dyna-Soar’s favour. It was never in a good position to compete with NASA’s capsule-based programs and was always just slightly too futuristic to come to pass quickly.

But had it developed, it might have turned into a useful asset. It could have been a shuttle ahead of its time, delivering hardware or supplies to astronauts on the Skylab space station. It could have been a shuttle with a goal rather than the space shuttle NASA did develop that was built before it had a station to service. It could have been a space taxi on standby as a rescue vehicle. Instead, became a footnote in popular retellings of spaceflight’s history, though it’s echoes are a little clearer. NASA came back a Dyna-Soar-esque vehicle with the space shuttle, which “inspired” the Soviet Union’s vanishingly short-lived Buran shuttle. And though we’re seeing a resurgence in capsule’s now with NASA’s Orion spacecraft, SpaceX’s Dragon, and Boeing’s CST-100, it’s possible that the next generation with circle back to the spaceplane idea, coming full circle once again to Dyna-Soar’s basic concept.

Selected Sources: "Sänger: Germany's Orbital Rocket Bomber in World War II" by David Myhra; "Dyna-Soar: Hypersonic Strategic Weapons System" from Apogee Books.

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