During the brief time the three main engines
operate during liftoff and ascent, they burn more than 500,000 gallons
of super-cold liquid hydrogen and liquid oxygen propellants stored in
the huge external tank. Originally developed in the 1970s, the Space Shuttle's
main engines remain the world's most sophisticated reusable rocket engine.
NASA continues to increase reliability and safety through a program
of on-going engine enhancements. Major modifications were also performed
in 1988, again in 1995, and the latest in 2000. To understand the operation
of this high-performance rocket engine, an understanding of its basic
propellant flow is first in order.
here to see 3-D model.