U-1 (semi-trailer)
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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 by Cambridge Corporation for a secret United States government program. The trailer had a vacuum-insulated tank that carried liquid hydrogen at extremely low temperatures (around −253 °C).
The U-1 liquid hydrogen trailer was designed in response to requirements of the secret United States government program code-named Suntan, which aimed to develop a high speed, high altitude hydrogen-powered military aircraft for the United States Air Force.[1][2] The trailer was designed and built by the Cambridge Corporation with the delivery coordinated through Wright Field in Ohio.[1]
Design
The U-1 trailer consisted of a vacuum-insulated, double-walled tank designed to maintain the liquid hydrogen at extremely low temperatures of about −253 °C (−423.4 °F). [3] It had a storage capacity of approximately 26,500 L (5,800 imp gal; 7,000 US gal) of liquid hydrogen.[1] As liquid hydrogen has a very low density (around 70 kg/m³), the mass of the entire payload was relatively small compared to its large volume.[4] This low weight made it feasible for the trailer to be designed with a single axle, despite the larger size of the tanker.[1]
During storage, the trailer experienced about two percent of content loss per day due to the evaporation of liquid hydrogen (hydrogen boil-off) due to heat, despite being maintained at low temperatures.[1] This required the cryogenic hydrogen systems to have pressure-relief and venting mechanisms to safely expel the evaporated hydrogen gas.[3]