One day late this year, a missile will streak over Florida burning what the Air Force calls "the ultimate chemical fuel": liquid hydrogen. When burned with liquid oxygen ("lox"), liquid hydrogen delivers 40% more thrust than currently used fuels, can double the payload of a satellite-carrying rocket. Last week the Air Force took the wraps off a secret plant near West Palm Beach known prosaically as the Apix Fertilizer Co. The name is a phony to hide the fact that the plant produces liquid hydrogen.
The Florida plant was built by Air Products. Inc., a fast-growing company that has become...