Small Liquid Hydrogen Tank for Drop Tower Tests

A researcher fills a small container used to represent a liquid hydrogen tank in preparation for a microgravity test in the 2.2-Second Drop Tower at the National Aeronautics and Space Administration (NASA) Lewis Research Center. For over a decade, NASA Lewis endeavored to make liquid hydrogen a viable propellant. Hydrogen’s light weight and high energy made it very appealing for rocket propulsion.

One of the unknowns at the time was the behavior of fluids in the microgravity of space. Rocket designers needed to know where the propellant would be inside the fuel tank in order to pump it to the engine. NASA Lewis utilized sounding rockets, research aircraft, and the 2.2 Second Drop Tower to study liquids in microgravity. The drop tower, originally built as a fuel distillation tower in 1948, descended into a steep ravine. By early 1961 the facility was converted into an eight-floor, 100-foot tower connected to a shop and laboratory space. Small glass tanks, like this one, were installed in experiment carts with cameras to film the liquid’s behavior during freefall.

Thousands of drop tower tests in the early 1960s provided an increased understanding of low-gravity processes and phenomena. The tower only afforded a relatively short experiment time but was sufficient enough that the research could be expanded upon using longer duration freefalls on sounding rockets or aircraft. The results of the early experimental fluid studies verified predictions made by Lewis researchers that the total surface energy would be minimized in microgravity.