Boeing’s design in the 1960s followed the lines of the same concept and could have been weaponized with ease given its 10,500 pound maximum payload. Verifiable details on the X-20 are murky at best as it never made it past the prototype stage, and it never actually flew. But the project came so close to being greenlit that astronauts and test pilots were actively training to fly the craft using simulators. Neil Armstrong himself worked on creating such simulators. According to Armstrong, the Dyna-Soar itself was a separate project developed by the United States Air Force and not NASA.
$410 million later and the project was scrapped. According to Boeing, the X-20 didn’t really have any realistic use in combat, and, given the proliferation of nuclear-capable missiles and long range strategic bombers, it was going to be very quickly outdated even if it did see the light of day. The project was officially shuttered on December 10th, 1963, a little under six years before Neil Armstrong walked on the Moon, without the help of a space plane.
About 60 years after the program was canceled, no prototypes are known to have survived, and all that currently exist are photographs of prototypes, illustrations of what it may have looked like in a completed state, and scale models of the craft.