 Hey guys, in the comments on my video about how airplanes fly, there was some discussion about why the 747 stopped carrying the space shuttle into orbit. This didn't actually happen, but there are pictures of the shuttle on the back of a 747. So today on Vigid Space, we're going to talk a little bit about air-launching vehicles. The first aircraft to be air-launched was the X1, Bell's first supersonic aircraft specifically designed to break the sound barrier. It was a small aircraft with a rocket engine in the back and fuel tanks taking up most of the fuselage, and the rationale behind air-launching it was simple. If you needed to save all of that fuel and all of that power for the high-speed run to try to break the sound barrier, don't waste any of the fuel getting up to altitude. The solution was to air-launch it. Have it nestled underneath the belly of a B-29 bomber and release it at 23,000 feet. Once airborne at altitude already, the pilot would have all of his available fuel to go as fast as he possibly could to break the sound barrier, which Jack Yeager did in 1947. But those high-speed runs weren't the only air-launched flights the X1 ever made. Before any of the powered flights, the X1 made glide flights. On these flights, the pilot was released at altitude and flew the aircraft down for smooth landing on the dry lake bed at Edwards Air Force Base entirely without power. It was a way for the pilot to become comfortable with the aircraft's controls. But also, because the X1's fuel was reserved for that high-speed push to Mach 1, it wouldn't have any fuel for the landing, so the X1 would always make an unpowered gliding landing. These glide runs were a way to practice that unpowered landing. The X planes that came after the X1 followed the same basic flight profile. There were glide flights before powered flights, but the X15 did something different. The X15 was mounted underneath the wing of the B-52 mothership, not underneath the belly. And before any glide flights, they did captive flights. The X15 stayed inside the pylon firmly underneath the wing and wasn't released. It was a chance for the pilot to become familiar with the way the aircraft felt in an airstream. Then the X15 went on to glide flights before going into powered flights. The powered flights, of course, were the high-speed and high-altitude runs. And the space shuttle was put through the exact same tests. These are some of the pictures you see with the shuttle mounted on the back of a 747. The space shuttle is far bigger than the X15 or the X1, far too big to be launched from underneath the belly of a mothership or from underneath the wing. So it was mounted on top of a 747. And it did more or less the same thing that the X15 did. First, there were captive flights with the shuttle never leaving the back of the 747. Then there were glide flights where the shuttle was released from the back of the 747 and flown to a smooth, gliding landing at Edwards Air Force Base. Some of these were done with a fairing over the rear engines and some without. And it was exactly what the shuttle would do when coming back from orbit because it was not powered on its descent. But unlike the X15 and the X1 and all the other rocket planes that were air-launched, the shuttle never made a powered flight at Edwards. The first time it made a powered flight was the first time it was launched on STS-1. And, of course, the shuttle was transported to its final destinations and museums across the country, also on the back of 747s. I hope that clears things up for you guys. And if you have other topics you would like to see discussed on the show, please leave them in the comments below and also any other questions you might have. And I will do my best to answer them. And with new episodes going up every Tuesday and Friday, don't forget to subscribe right here so you never miss an episode. And for some daily vintage space content, be sure to follow me on Twitter as AST Vintage Space.