Launch ascent testing of a representative Altair ascent stage methane tank

In order to support long duration cryogenic propellant storage, the NASA is investigating the long duration storage properties of liquid methane. The Methane Lunar Surface Thermal Control (MLSTC) testing is using a tank of the approximate dimensions of the Altair lunar ascent propellant tanks. The tank was insulated with multilayer insulation and placed inside of a vacuum chamber to simulate the various environments that would be encountered during launch and travel from the earth to the lunar surface, including long duration stays on the lunar surface. One of these environments to be studied is the launch and ascent environment; while all the effects of this mission phase cannot be simulated at the same time, an effort was made to simulate as many as possible. Boil-off testing included ambient pressure ground hold testing followed by a rapid depressurization of the vacuum chamber during which the liquid methane tank was allowed to come to steady state condition in the high vacuum environment. The data gathered from the series of tests fit with-in pre-test predictions and yielded much needed test data for rapid depressurization using liquid methane.

► Tested representative Altair tank during a rapid depressurization cycle. ► Total heat load throughout representative launch transients. ► Compare to analytical model of testing. ► Investigate main source of error in analytical model. ► Heavy wall tank contributes significantly to test results, artificially raising total heat load.