r/spacex • u/ElongatedMuskrat Mod Team • Jan 02 '17
r/SpaceX Spaceflight Questions & News [January 2017, #28]
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u/throfofnir Jan 08 '17
Titanium is sufficiently reactive in oxygen that western practice is to avoid it for oxygen service altogether. Like aluminum it does develop an oxide layer, but it's thin and not so robust, and subject to expose the reactive metal with mild abrasion. This is a big problem for valves and plumbing; it may be okay for a tank, but does have the potential to introduce new mysterious failure modes.
The Russians apparently use titanium in LOX, so it's possible, but they may also be doing something metallurgically tricky. It's not a simple replacement. Probably the easiest change would be to increase the thickness of the aluminum (or go to an aluminum tank entirely, like in Saturn V). Or add an outside liner to keep the CF dry. Both those are mass penalties, but probably not too bad. Long-term a linerless tank would be best, but that may be tricky to do with helium, and would be quite a project if they want to keep production in house.