The sign accompanying the RL-10. It reads
Pratt & Whitney RL-10 Rocket Engine
Develops 15,000 lbs. of thrust.
Two RL-10 engines power the Centaur upper
stage vehicle. Centaur was the first operational rocket to use high
energy cryogenic propellant:
- Liquid oxygen: -297°F (-183°C)
- Liquid hydrogen: -423°F (-253°C)
Glenn pioneered in the research of these propellants in the 1950s.
Liquid hydrogen and liquid oxygen are used on the Space Shuttle, Atlas-Centaur,