Instead it burns storable liquid fuels (a mixture of hydrazine and unsymmetrical dimethylhydrazine with nitrogen tetroxide as oxidizer) that are "hyper-golic," ignited .
It is steered by injections of liquid nitrogen tetroxide into the white hot gas stream through valves in the sides of the engine's nozzle.
Still another costly delay followed a mishap on the pad that occurred during a supposedly routine fueling operation when a jammed valve caused a back-up of nitrogen tetroxide.