 NASA's Saturn V rocket was assembled inside the vehicle assembly building. The launch pad was three miles away. So how do you make a 363-foot rocket travel that distance with the crawler transporter? And that's what we're talking about today on Vintage Space. Figuring out how to get the Saturn V from the VAB to the launch pad felt Kurt debut, Gerg von Teessenhausen, and Theodor Popel. All three men had worked with von Braun on the V2 project in Germany so they had some experience in getting a rocket onto the launch pad. At Penemünde, the Germans had transported their rockets upright on a platform by rail to the launch site. And that's the basic idea they brought to the Saturn V, except that the Saturn V was a little bit bigger. The V2 stood 46 feet tall. The Saturn V was 363 feet. It would have to be a slightly different solution. One of the earliest proposals came from the Martin Company, and that was to use a barge. It would rack the Saturn V on a barge and carry it down some river to the launch pad. The proposal looked great on paper until NASA started digging in and realized that nobody on Martin's team was an optical engineer. Small scale testing said that when the barge moved through a narrow canal, it created a vortex that would make steering through the water basically impossible. And wind tunnel tests said that the gantry next to the rocket would act basically like a sail adding significant drag. It was just not a viable solution. And neither were rails, like the Germans had used in Penemünde. It was just unrealistic to use rigid rails on the softer soil like Cape Canaveral. The solution was to use a tried and true piece of 19th century coal mining technology. A crawler designed to deliver a smooth ride with no vibration. Scaled up, one could theoretically move the Saturn V without disrupting all the delicate systems and machinery. The finished vehicle was a six million pound machine with four crawlers rolling on treads made of a series of one ton links supporting the main deck where the rocket would sit. Powered by two engine rooms with half a dozen locomotive-sized diesel engines each, the vehicle delivered a total of 6,000 horsepower to motors and levers. To keep the rocket perfectly level on its trip down the crawlerway, NASA developed an ingenious sensing solution. A pair of pipes filled with mercury ran diagonally from corner to corner under the platform, bending up at the ends with a wire inserted into the tubes, a hairs width above the mercury. If the platform tilted, the wires contact with the mercury would short it out, sending a signal for hydraulic fluid to lift the appropriate corner to level out the platform. The system worked so well that the launch escape tower at the very top of the Saturn V never moved more than five inches away from perfect vertical. But that precision came with a bit of a speed penalty. The top speed of the crawler was about 1.5 miles per hour. Meaning it took about five hours for the rocket to move from the VAB to the launch pad. And a few people have asked me in previous videos why the gantry next to the Saturn V was painted red. I haven't been able to track down a definitive answer yet, but I suspect it was probably due to visibility. The same way the rocket was painted black and white so they could see it rolling in flight, I imagine the gantry was actually painted red so it would be visible against a daylight sky. But again, that's just conjecture. I am still looking up the proper answer to that one. But I did find that during the shell program, the structure next to the shuttle was given a zinc-based gray coating because of advances to corrosion treatment. Florida may be a great place for a launch, but that salty air isn't exactly great for metals. The same crawler transporter that took the Saturn V rockets also carried the space shuttles to its launch pad. So have any of you ever seen the crawler transporter in action? Let me know in the comments below. And if you want more vintage space content every single day of the week, be sure to follow me on Twitter as AST Vintage Space. And with new episodes going up every Tuesday and Friday, be sure to subscribe right here so you never miss an episode.