Tuesday, September 27, 2005

LH2: Love it or hate it?

Jon Goff has an absolutely fantastic post here at LH2: Love it or hate it?

LH2 seems most clearly stupid for a first stage fuel. Hydrogen engines have low thrust-to-weight, low thrust-to-cost, and big tanks which can cause a lot of atmospheric drag. Hydrogen first stages also see larger gravity losses than hydrocarbon first stages.

Both the Shuttle and the Delta IV use LH2/LOX engines off the pad. The Shuttle uses hydrogen because those engines are ground-ignited second stage engines, so it has at least some excuse. But the Delta IV is a simple two stage rocket with both stages being LH2/LOX. Why? Did they need to be different than the Atlas V?