The Open University has been conducting experiments with a vacuum microwave chamber to melt or sinter lunar simulants for construction purposes. Microwave energy efficiently heats lunar simulants volumetrically, overcoming problems with the low thermal conductivity of lunar regolith. The temperatures more than that required for hydrogen reduction of ilmenite and iron oxides to produce water. The high temperatures will improve the reaction rate; however, the simulant is molten inside a crucible and requires diffusion of gases through the molten simulant.

50 g samples were prepared of JSC-1A mare simulant with ilmenite added to give an ilmenite concentration ranging from 0.5% to 20%. The crucibles were heated in the microwave chamber with an atmosphere of 0.15 – 0.2 bar hydrogen for one hour. During the reaction any water produced was trapped in a liquid nitrogen cooled cryotrap and the hydrogen pressure measured. Gas in the chamber was monitored by a mass spectrometer with care taken to ensure that there were no atmosphere leaks into the system. After he reaction the water collected was transferred to a cold finger and weighed.

The reaction of hydrogen was observed to occur reasonably rapidly (in a few minutes) as the sample melted. The amount of water collected was proportional to the ilmenite concentration with calculations indicating that approximately 10% of the ilmenite had reacted.Adding a hydrogen reduction stage to an ISRU process that melts ilmenite rich lunar regolith would give oxygen as a useful additional byproduct.