Last week on Friday 20th March and on Tuesday 24th March the first unignited pool tests with LH2 have been conducted. The first tests were done with a 0.5 m x 0.5 m pool with a maximum fill height of 0.1 m and a massive concrete bottom plate. So, the maximum inventory of the pool is 1.75 kg LH2.
They were showing some interesting phenomena:
- The thin alumina sheets were slightly bended due to thermal shock / stresses.
- There were wave like oscillations, partly attributed to the LH2 surface (which was hardly visible) and partly to cold hydrogen vapour/ water fog and ambient air interface (with smaller frequency).
- There is a high frequency oscillation heard (about 5-8 kHz) in the initial phase when the cryovalve is opened (similarily observed also when opening LN2 tanks).
- The heavy evaporation generated huge fog clouds which are deemed to coincide with flamable envelop.
- The almost steady pool evaporation rate was 10 g /s, corresponding to 1/7 liter / s or 3.43 cm / min.
- The pool and the release nozzle show a very homogeneous ice layer after the experiment, when LH2 is completely evaporated. It is asssumed that this is water ice.