X-20: The U.S. Military’s Plan for 17,500 Miles Per Hour Space Plane

A former member of the U.S. Air Force breaks down the X-20: When the Soviet Union launched Sputnik into orbit, the Western world was shocked – and caught flat-footed, without a response in place. Jolted into action, paranoid that the Soviets would dominate outer space (and hence the world), Americans began hectically brainstorming adequate responses. Desperate to launch a man into space, the Americans considered all possible available options – including personnel options (from surfers to acrobats and gymnasts before ultimately settling on military pilots) and vehicle options. While NASA long ago settled on launching astronauts into space in capsules perched upon rockets, the then-nascent space agency considered flying to space, in an aircraft, undermanned control. 

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Early Experimental Aircraft

The U.S. Air Force even developed experimental aircraft to fly into space. The most viable program, the X-15, actually broke the threshold of space, earning the X-15 pilots their astronaut wings. But the U.S. Air Force had another X-plane in the works, something designed to fly into space itself and conduct a variety of missions including space rescue, space interceptor, satellite maintenance, satellite-killing, and high-altitude reconnaissance. The plane would have been perhaps the most advanced machine in existence. Yet you’ve likely never heard of the plane, the Boeing X-20 Dyna-Soar because the thing was never actually built.

X-2o: A History 

Despite never flying, despite never even being constructed, the X-20 was a very real program. Operating from October 1957 until December 1963, the X-20 program cost taxpayers USD 660 million. Today, that figure is the equivalent of $5.58 billion – all for a set of blueprints. The X-20 was born from Operation Paperclip, a top-secret U.S. program to harvest Nazi Germany’s most brilliant scientists after World War II’s conclusion; the X-20 was a natural extension of the Nazi plot to create hypersonic planes that could be launched from Europe and bomb the United States before landing in Imperial Japan. Fortunately, the Nazi scheme was never realized, but their concept informed the X-20 program.

Whereas the Mercury (and later Gemini and Apollo) programs used capsules, which hurtled through space, spam-in-a-can style, the X-20 program was powered and flown like an aircraft. The designs featured a low, delta-shaped wing, no-tail, and a cockpit for one pilot. Like a Mercury capsule, the X-20 would hitch a ride aboard a rocket, but instead of plummeting back to Earth, and clumsily landing in the sea beneath a parachute, the X-20 would glide back to Earth, with dignity, before landing on a runway like any other plane might. Although, the X-20 would land on a pair of retractable wire-brush skids, rather than traditional landing gears (rubber landing gears would have incinerated during re-entry). Before returning to Earth, the X-20 would rely upon its two rocket engines to reach speeds of 17,500 miles per hour and altitudes of 530,000 feet. 

The X-20’s extreme flight characteristics, and novel mission profiles, demanded skilled pilots. In April 1960, an elite group of seven pilots was surreptitiously selected from amongst the astronaut corps to join the X-20 program. Among them: is Neil Armstrong, a veteran of the X-15 program who would one day land on Mare Tranquillitatis. 

“Armstrong never flew the X-20, of course. No one did,” I wrote for The Debrief. “Nagging problems plagued the spaceplane’s development. Securing funds was a constant problem, naturally. But the most time-consuming problem was uncertainty regarding the launch vehicle.”

Which One Will Be Part of the Space Race?

The USAF was conflicted between sending the X-20 to space on either LOX/JP-4, fluorine-ammonia, fluorine-hydrazine, or RMI engines. Meanwhile, Boeing wanted the X-20 to ride an Atlas Centaur. Ultimately, the Titan III rocket was selected as the launch vehicle – but the debate had cost years and Mercury missions had commenced in 1961, placing the X-20 program behind the curve.

Despite settling on the Titan III rocket, the X-20 program still faced questions. “What is the purpose of this program? What is the X-20 going to do up there,” I asked? “The X-20 was originally designed to conduct aeronautical research and weapons system developments simultaneously. But as the program progressed, questions persisted.” Seeking to answer all lingering questions, Secretary of Defense Robert McNamara greenlit a study to determine whether the X-20 weapons program was feasible. “The results of the study doomed the X-20 program.”

While the USAF had been intently studying controlled re-entry with their X-20 program, they had neglected to properly consider weapons development. Well, McNamara and the Department of Defense didn’t care so much whether a space vehicle came back to Earth in a controlled or uncontrolled manner – whatever works, as long as the thing was a viable weapons system. The X-20 developers, however, had neglected the weapons systems side of the program. McNamara was not impressed. He canceled the program, just as construction began on the first prototype. 

The years and resources spent on the X-20 may seem wasted, naturally, since the space plane was never built. But the knowledge gleaned from the X-20 program proved valuable; the X-20 is the direct ancestor of the Space Shuttle program, arguably the most sophisticated piece of machinery humans have ever constructed. And a progeny of the X-20 is still flying today: Boeing’s mysterious X-37 – an autonomous, reusable space plane.   

Bonus Photo Essay: Meet the X-37B 

Harrison Kass is the Senior Defense Editor at 19FortyFive. An attorney, pilot, guitarist, and minor pro hockey player, he joined the US Air Force as a Pilot Trainee but was medically discharged. Harrison has degrees from Lake Forest College, the University of Oregon, and New York University. He lives in Oregon and listens to Dokken. Follow him on Twitter @harrison_kass.