meiza - 14/6/2007 11:34 AMIt's easier to make high thrust kerosene engines. Turbopumps are sized by volume of flow, not mass, and hydrogen is really light. Also hydrogen is tricky to deal with in a big stage.
Propforce - 14/6/2007 3:08 PMQuotemeiza - 14/6/2007 11:34 AMIt's easier to make high thrust kerosene engines. Turbopumps are sized by volume of flow, not mass, and hydrogen is really light. Also hydrogen is tricky to deal with in a big stage. Huh? What? So I make the LH2 turbopump a little bigger, what is the big deal?
pad rat - 14/6/2007 2:53 PM...and when you spill it, it cracks your launch table
Antares - 14/6/2007 4:25 PMFor me it's an operability question.Hydrogen volatility and leak tendencyThe helium required to purge hydrogen systems,helium is an increasingly scarce commodity,boosters/tanks that have to get barged instead of flown (at least for ILV class),-423F is a lot worse than -290ishF,another large set of cryogenic flight valves...... From a purely technical stance, LH2 is great. But when total launch system cost and ease of use are added, it's RP all the way.Heck, I'd imagine Elon did a pretty hard cost analysis since he had a clean sheet, and SpaceX didn't even use a hydrogen second stage.I think the reason Delta IV went LH2 was the company still had experience with the SSME and Shuttle MPS.