The cast macroporous Zirfon (R) diaphragm has been developed many years ago to be used as a gas separator in industrial alkaline water electrolysers. It has also been proven as an excellent separator in alkaline electrolysers for space applications For space applications it is preferred to operate the electrolyser with a fixed alkaline electrolyte so that no pumps are needed and all kinds of electrolyte circulation problems can be avoided The target of this development was the casting of an Electrode Diaphragm Electrode (EDE) as a single unit comprising the anode, the diaphragm and the cathode This EDE should operate at a minimum cell voltage and the highest possible gas purity (C) 2009 Professor T Nejat Veziroglu Published by Elsevier Ltd. All rights reserved.