The U-1 was a 1950s liquid hydrogen trailer designed to carry cryogenic liquid hydrogen (LH2) on roads being pulled by a powered vehicle. It was designed in response to requirements of the secret US government program code-named Suntan, which aimed to develop a high speed, high altitude hydrogen-powered military aircraft. The trailer was constructed by the Cambridge Corporation and had a capacity of 26,500 liters with a hydrogen loss rate of approximately 2 percent per day. The U-1 was a single axle semi-trailer. The specifications for its successor the U-2 a double axle semi-trailer were issued on 15 March 1957.
- Sloop, John L. "Liquid hydrogen as a propulsion fuel, 1945-1959". NASA History Program. National Aeronautics and Space Administration. Retrieved April 22, 2016.