 I have posted a lot of videos about the X-15 lately, and every single time there are some really good questions in the comments, and a lot of them are pretty basic program questions. And so I thought today on Vintage Space, it would be a good thing to do a bit of a crash course on the X-15 program. In 1953, the Bell X-1A was the fastest plane on the planet. It was Chuck Yeager who took it to its top speed of Mach 2.44, and he almost died in the process. It was clear that there was a need for a high-speed research aircraft, something that could probe not only supersonic, but hypersonic velocities. That speeds in excess of Mach 5. And Bell aircraft's chief engineer, Robert Woods, was the first one to really pitch the idea to the NACA in 1952. By 1954, the NACA had a pretty good idea of what the aircraft should be, and had gotten the U.S. Air Force and the U.S. Navy to sign on to the project. Midway through 1955, North American aviation was chosen to build the aircraft that would become known as the X-15. But North American almost turned down the chance to build this high-performance research aircraft. The company had so much going on at the time that it really didn't want to have to take resources away from the bigger projects to devote time, energy, and manpower to a small run of experimental planes. It was Harrison Storms who was really the X-15's chief cheerleader with North American. Then manager of research and development at North American's Los Angeles Division, he took his case directly to Raymond Rice, the vice president and chief engineer of North American. Rice told Storms that North American could accept the X-15 contract on the condition that Storms keep everything relating to the eccentric aircraft off of Rice's desk. Storms was only too happy to oblige, and North American took the contract. And one other man played a very important role in getting the X-15 off the ground. Scott Crossfield believed so strongly in the need for a high-performance, hypersonic research aircraft that he actually left his job with the NACA and went to North American. He was, to use his own phrase, the X-15's chief son of a bitch. If any change or any development was going into that airplane, it was going to go through him first. So now on to the X-15 as an airplane. The X-15 was a single-seat mid-wing monoplane airplane, 50 feet long, with a 22-foot wingspan, and a wedge-shaped vertical tail, 13 feet high. But I kind of think about it almost as a missile with a cockpit. This is the tiny little cockpit up front, and the rest of the X-15's body was devoted to the fuel tank and all the plumbing that would power the one massive engine in the rear. The X-15 used conventional aerodynamic controls for flight in the atmosphere. That's rudder surfaces on the vertical stabilizer for yaw control, and canted horizontal surfaces on the tail for pitch control. But because the X-15 was designed to fly at altitudes where the atmosphere is far too thin for traditional flight control surfaces to work, the X-15 also had reaction controls, a series of hydrogen peroxide jets in the aircraft's nose and on its wings that could adjust its attitude at altitude. Coming back from altitudes above the appreciable atmosphere meant the X-15 would be exposed to intensive heat during reentry. That was one of the things that the aircraft was actually developed to look into. To handle these heat loads, the outer skin of the X-15 was made of a nickel-chrome alloy called Incanel-X, and built with a heat sink structure. The cabin, meanwhile, was made of aluminum and isolated from the outer body to keep it cool. When the X-15 first flew, it had two XLR-11 engines mounted in the rear. Each of these engines has four barrels that can be ignited individually to give it some sort of throttle ability. But the XLR engines combined produced a total thrust of just 16,380 pounds. These two engines were eventually replaced by the Big Engine, the XLR-99, a throttle-able engine that produced 57,000 pounds of thrust. But even the XLR-99 wasn't enough to get the X-15 off the ground and then send it to high altitudes above the atmosphere. To save all of the onboard fuel for the powered flight, the X-15 was launched from underneath the wing of a B-52 bomber already at altitude. The B-52 always took off from Edwards Air Force Base and launched the X-15 from about 30,000 to 40,000 feet overtop another lakebed somewhere in the area called the Launch Lake. From here, the pilot could fly one of two flight profiles. If the goal was a high altitude flight, he would pitch the nose up and fly in a high-arcing trajectory, burning all his fuel in the process. If the goal was a speed run, he would fly a more level path. One X-15, the X-15A2, was modified for high-speed runs. Delivered to NASA in February of 1964, it featured external tanks for liquid ammonia and liquid oxygen that provided roughly 60 seconds of additional engine burn time. At the end of either flight path, the X-15 landed on dry lakebed, ideally at Edwards Air Force Base, using two rear skids and forward nose gear. It landed typically at about 220 miles per hour. Between 1959 and 1968, 12 men piloted the X-15. They were Scott Crossfield, Joe Walker, Robert White, Boris Peterson, Jack McKay, Bob Rushworth, Neil Armstrong, Joe Engel, Milt Thompson, Bill Knight, Bill Dana, and Mike Adams. Pete Knight flew the fastest flight on October 3rd of 1967 in the X-15A2, hitting Mach 6.7. Joe Walker flew the highest flight on August 22nd of 1963, reaching a peak altitude of 354,200 feet. The X-15 was amazing in its time, and among the applications the research went to was the Space Shuttle. So having learned all that about the X-15, do you guys still have questions? Let me know in the comments below, and I will do my best to answer as many as I can as best I can. But if you really want to dig in a little bit more to the X-15 program, I've got a couple of books that I would definitely recommend. The first is Michelle Evans' The X-15 Rocketplane. It is a fantastically detailed book from somebody who grew up with and loves the program, I think more than anybody I've ever met. The second book is Milt Thompson's At the Edge of Space, which is a really phenomenal and really interesting look at the program because Milt Thompson was, of course, an X-15 pilot himself. He brings some really neat insights and personal stories into the book. For more vintage space content every day of the week, including pre-space space like the X-15, be sure to follow me on Twitter as AST Vintage Space. And with new videos going up every Tuesday and Friday, don't forget to subscribe right here so you never miss an episode.