 Sometimes, cutting-edge research aircraft look a little on the strange side. Case in point, the pink X-15, and that's what we're talking about today on Vintage Space. The X-15 faced some major heating challenges. On its high altitude runs, it would be returning from near-space altitudes down to the dry lake beds at Edwards Air Force Base. On its speed runs, it would be pushing through all that atmosphere at exceptionally high speeds. It was designed to fly up to Mach 7. Both flight profiles meant that the airplane was going to get extremely hot. Able to retain its strength at temperatures up to 1200 degrees Fahrenheit, in Canal X went a long way in protecting the X-15 from high temperatures. But problems cropped up when the plane went hypersonic. That speeds in excess of Mach 5, or 5 times the speed of sound. The wing-leading edges distorted and the skin buckled. Covering troublesome areas helped, but if it was going to hit Mach 7, it would need a different level of heat protection. Enter the pink X-15. In 1966, the X-15A2 aircraft was covered nose-to-tail in an ablative coating. That is, a material designed to burn away and protect the aircraft from high temperatures associated with hypersonic flight. The pink material was actually only half the battle against high heat. It was a silicone elastomeric ablator that was sprayed on the X-15 in varying levels of thickness according to the heat loads of a specific part of the aircraft. And loading the material strategically kept the overall weight down. The leading edges were additionally protected by a related erosion-resistant material applied in preformed sections. This pink substance was then covered with a white sealant coat before flight. The idea was to have the sealant and the pink material burn away as the X-15 flew. By the time it was gone and the metal was showing, the X-15 would be traveling slow enough that the metal would be able to deal with the heat associated with the flight profile. Unfortunately, the pink ablative material and the white sealant weren't a very good long-term solution to the problem of aerodynamic heating. This is at a time, of course, when engineers were starting to think a little bit about going into space with these vehicles and refurbishing vehicles between flights. It took five weeks and 2,000 hours just to get the X-15 coated with all the ablative material. And it was just not something that could be done on a regular basis. But it did work. It was this coating that allowed the X-15 to reach its peak speed of Mach 6.7. Want to know more about how the Air Force and NASA got the X-15 up to that peak speed? Check out the latest article on vintage space linked below in the about box. For nearly daily vintage space type content, follow me on Twitter as AST Vintage Space. And with new episodes every Tuesday and Friday, don't forget to subscribe right here so you never miss an episode.