Long before NASA’s Space Shuttle became one of the most recognizable vehicles on the planet, the Americans had come close to developing another spaceplane that carried many of the same hallmarks. I say it came close because this project was cancelled in 1963 just after production of the prototype had begun – meaning we never even got to see a Boeing X-20 Dyna-Soar in the flesh.
Had the X-20 been built as planned, it would have been capable of aerial reconnaissance, bombing, space rescue, satellite maintenance, and enemy satellite sabotage – which is a broad portfolio if I’ve ever seen one. So does this mean that the United States wasted $660 million (around $5.7 billion today) on this failed program? Maybe. Or maybe this was just a stepping stone for what was to come. The idea of X-20 appeared in the late 1950s when science-fiction was booming and no doubt imaginations were running wild. Even today, we don’t have anything that can cover all of those bases, and it may well be that this versatile little spaceplane design simply appeared way too far ahead of its time.
The Silbervogel proposal
If you’re an avid viewer of Megaprojects you can probably guess where we’re going to start this video from, simply because most Cold War-era technology seemed to have a habit of originating from there.
Germany during the 1930s and 1940s was a terrible place to be for many, but seemingly a great place to be for rocket designers and aerospace engineers. The number of videos we’ve covered that either concern the Nazis directly, such as the V weapons, or indirectly after the war had finished, such as the Saturn V rocket and intercontinental missiles, show just how impressive this era was in terms of mechanical engineering.
And today we’re beginning in the thick of World War II with two German engineers, Eugen Sänger and Irene Bredt. The Silbervogel plane which they outlined was designed to be a liquid-propellant rocket-powered sub-orbital bomber that could have potentially been used to attack U.S cities.
Word is that Adolf Hitler had a somewhat bizarre fascination with bombing New York into oblivion and leaving it a smouldering wreck. The Amerikabomber program, which was first mentioned in 1938, planned to do just that – but with a minor problem – they didn’t have an aircraft that had any hope of being able to complete a round-trip of 11,600 km (7,200 miles).
The Silbervogel was one of several options that were considered for the Amerikabomber program and called for the plane to be launched along a 3 km (2 mi) long rail track by a large rocket-powered sledge reaching speeds of around 1,930 km/h (1,200 mph). Once airborne, the plane would fire its rocket engines and climb to 145 km (90 miles), at which point its speed would be roughly 21,800 km/h (13,500 mph).
Here’s where things get interesting. As the plane descended, and thanks to the increasing air density, the Silbervogel would experience lift against the underside of the plane, causing it to effectively bounce through the air. I know that sounds a little ridiculous, but bear with me. Each of these bounces would gradually bring it closer to the ground and with the aircraft now above New York, it could then disgorge a 4,000 kg (8,800 lb) bomb. But that’s not the end of it. This isn’t the kind of plane that turns around and the early Silbervogel designed suggested it could carry on across the United States – across the Pacific – before landing somewhere in friendly Japanese held territory in Asia – travelling a total of between 19,000 and 24,000 km (12,000 to 15,000 miles).
Now, in terms of mad Nazi plots during the War this might not even make the Top 5 – if you want to get really wacky why not check out our video on the Nazi Sun Gun idea. But Nazi lampooning aside, much of the science behind the Silbervogel was relatively sound. After the war, Sänger and Bredt worked for the French government but their ideas had caught the attention of the next tyrant to attempt to rule Europe, Comrade Stalin, who ordered that both be kidnapped and brought back to the Soviet Union where they would realise their plan. However, it didn’t work and both eventually returned to Germany.
While Sänger and Bredt may have found work with the French, many more brilliant German minds were whisked across the Atlantic and generally embraced by the American government who had now pretty much forgotten about the Germans and were now eyeing the Soviets suspiciously.
Two such men were Walter Dornberger, who had been the leader of Nazi Germany’s V-2 rocket programme and rocket-propulsion engineer Krafft Ehricke. The two began working at Bell Aircraft and in 1952 they proposed an adapted version of the Silbervogel with the name ‘Bomber Missile’ or ‘BoMi’.
This would be a vertical launch version of the German idea with a few significant differences. Instead of coming to a calm landing somewhere on the other side of the world, the Bomber Missile would use boost-glide, reentry trajectories that push an aircraft or an object back upwards meaning it could even double its ballistic trajectory. By doing this multiple times in a row, the aircraft would eventually lose speed, to a point at which the pilot would be able to bring it in for a safe landing.
Now, again, I know this sound far fetched, but by 1956, three separate programs were being developed in conjunction with one another, all using this kind of technology; the RoBo (Rocket Bomber), the Brass Bell, a long-range reconnaissance vehicle, and the Hywards (HYpersonic Weapons Research and Development Supporting system).
However, Uncle Sam received a rude awakening on 4th October 1957 with the launch of the Soviet Sputnik I. In an instant, the U.S realised it was well behind in the space race and just days later all three programs that I just mentioned were merged into the Dyna-Soar project or Weapons System 464L, and in 1959 Boeing was awarded a contract for the three-stage Dyna Project.
The first was Dyna-Soar I, a reconnaissance vehicle with glider tests expected in 1963 and actual powered flights taking place in 1964 when the plane was expected to hit Mach 18 – 22,000 km/h – 13,810 mph. The second, Dyna-Soar II, based on the Brass Bell long-range reconnaissance vehicle, would be operational by 1968 and the third, Dyna-Soar III, loosely the Robo rocket bomber, ready to go in 1974.
Now, of course, none of that actually happened because we never even saw a finished X-20 Dyna Soar, but let’s take a look at what would theoretically have been created. The small plane would have come with a crew of just one, a length of 10.77 metres (35.34 ft) and a wingspan of 6.3 metres (20.8 ft).
Two AJ10-138 rocket engines, with 8,000 lbf each, would have given the X-20 a top speed of 28,200 km/h (17,500 mph) and a range of 41,000 km (25,000 mi) – around three and half times around the equator. The service ceiling would have been an extraordinary (160 km) 100 miles straight up – that’s 421 Empire State Buildings on top of one another.
The design was a low-wing delta shape, with winglets to control the aircraft rather than having a tail. The airframe was due to be built with René 41 superalloy, a nickel-based alloy that retains high strength in the 600–1,000 °C (1,200–1,800 °F) temperature range. The bottom of the X-20 would be constructed with molybdenum sheets placed over René 41, while the nose would be built using graphite and zirconia rods.
The X-20 would have been launched on the back of a Titan Booster which would have jettisoned once the space plane reached its desired altitude. Coming back down to Earth would have been more complex and an opaque heat shield made from a refractory metal would protect the pilot’s window as it reentered the atmosphere. Once safely through, this too would have fallen away, which in theory just left the pilot needing to bring the plane in for a smooth landing. The X-20 couldn’t use conventional tyres because they would just shred so Goodyear developed retractable wire-brush skids using the same René 41 alloy as on the airframe.
While this aircraft never actually got to the testing phase, seven astronauts were covertly hired and scheduled for testing once the aircraft finally emerged. You’ll certainly know one name from the list because nine years before taking a giant leap for mankind, Neil Armstrong was recruited to the Dyna Soar program, where he remained between 1960 and 1962.
Strangely enough, the X-20 was even given a glitzy Las Vegas unveiling in 1962 by the U.S Air Force, no doubt eager to impress the American public still muttering bitterly about Sputnik 1. Several individual components were tested, such as the boosters and inertia guidance subsystem and the B-52 Stratofortress had even been earmarked to air-drop the X-20 when it was ready.
At this point, you’d be forgiven in thinking that it was just a matter of time until the X-20 Dyna Soar roared into life, but alas, it all came to nothing. In an instant, on 10th December 1963, the entire project was cancelled.
So why did they cancel it all when everything was going so well? While designs were certainly progressing and there were plenty of encouraging results from early testing, there were still a lot of unanswered questions surrounding the X-20 Dyna Soar. There were question marks over the booster and the launch system to be used but also much more fundamental queries over just what exactly the mission profile for this kind of spaceplane would be.
In the late 1950s, the B-52 had shown itself as more than capable of circling the globe all on its own, meaning a theoretical military strike wherever needed. Then there was the Intercontinental Ballistic Missiles which also began appearing towards the end of the decade, which again, could soon hit any target on earth. With these two forms of attack, it’s unclear where a hugely expensive, experimental aircraft fitted into the U.S Air Force plans.
Then there was the cost. As I mentioned earlier, at the time the project was cancelled it had cost around $660 million (around $5.7 billion today) which is a massive investment to be backing away from with nothing to show for it. But it’s estimated that the project would have needed another $373 million ($3.2 billion today) and at least another two and a half years before its first flight. So I guess if you’re going to pull the plug it’s probably best before you hit the $1 billion mark ($8.6 billion today) which it almost certainly would have eventually surpassed.
But despite the huge costs and the very obvious fears that come with such a drastically different kind of aircraft, most people associated with the project have long said that it was all entirely feasible. As far as we can tell, the only reason we didn’t have a spaceplane capable of boost-glide in the late 1960s, was because of the cost.
The X-20 Dyna Soar may have crashed and burned before it had even lived, but its legacy can be seen in several projects that came after it. The Space Shuttle is often compared to the X-20 and while they are vastly different in many ways, they certainly share several characteristics. We’ve recently also done a video on another space vehicle that also echoes the memory of the X-20, the Boeing X-37, which is currently undergoing its sixth test flight.
The X-20 may not have worked out as a stand-alone program, but it undoubtedly acted as a technological stepping stone to where we are today. As it seems was often the case during this period, revolutionary out of the box thinking was more often than not halted by economical and political reasons rather than scientific or engineering.