Demanding Design Booms Shuttle Engine

A space shuttle main engine burns at 6,000 degrees F, but the outside of the nozzle remains cool to the touch. Prior to launch, sometimes it even frosts over.

The nozzle technology that allows a finger-width of ridged metal to contain and steer flames that would boil iron is just one of the scores of innovations designers came up with for the engines three decades ago.

Such advances were critical if NASA was going to realize its plans for a reusable space shuttle that, unlike the previous rockets, would not use its engines once and then drop them in the ocean.

Added together, the innovations became a rocket engine that is more than 99.9 percent efficient, which means that almost all of its hydrogen and oxygen is used to create thrust. For comparison, an automobile engine is about a third as efficient, since most of its energy is created in the form of heat that does not turn the wheels.