Tom Gallard, London asked:
How is oxygen made and recycled on the International Space Station?
We put this question to Mark Hempsell, Senior Lecturer, University of Bristol:
The only way I can think to produce it would be by splitting water into hydrogen & oxygen; but wouldn't it be easier/cheaper to ship pressurised oxygen cylinders from Earth?
If I remember correctly, at least in the past they used compounds like lithium (usually preferred because lighter) or potassium peroxide: it absorbs the CO2 and the H2O produced by the astronauts and in doing this it releases O2:
The NASA article says something very interesting - that emergency oxygen is produced by "perchlorate candles" and that the same system is used to produce the emergency oxygen supply on aeroplanes. Unfortunately they give no details of this reaction - so what is it?