The RL10B-2 is a unique cryogenic upper stage engine in the long line of Pratt & Whitney dependable rocket engines.

Derived from the core of the legendary RL10 that built a reputation as NASA’s most reliable upper stage engine, the RL10B-2 features the world’s largest carbon-carbon extendible nozzle. This high-expansion ratio nozzle enables the RL10B-2 to achieve a remarkable 465.5 seconds of specific impulse and lift payloads of up to 30,000 lbs.

Upper Stage Rocket Engine

The RL10B-2 currently powers the upper stage of the medium and heavy-lift versions of Boeing’s Evolved Expendable Launch Vehicle (EELV) and commercial offerings, the Delta IV, in addition to the upper stage of the Delta III.


Thrust: 24,750 lb

Weight: 664 lb

Fuel/oxidizer: Liquid hydrogen/liquid oxygen

Mixture ratio: 5.88:1

Specific impulse: 465.5 sec

Starts (total): 15

Service life (total): 3500 sec

Expansion ratio: 280:1

Length: (stowed) 86.5, (deployed) 163.5

Diameter (nozzle extension): 84.5

Delta 4 Rocket

Delta 4 Rocket


– Modern Engineering for Design of Liquid-Propellant Rocket Engines (Progress in Astronautics and Aeronautics, Vol 147
from Amazon.comAmazon.co.uk
Rocket Propulsion Elements, 7th Edition by George P. Sutton (Author), Oscar Biblarz (Author)

– Rocket Exhaust Plume Phenomenology by Frederick S. Simmons 
from Amazon.comAmazon.co.uk

– Amateur Rocket Motor Construction: A Complete Guide To The Construction Of Homemade Solid Fuel Rocket Motors.
from Amazon.com

RL10B-2 Links

  • RL-10B-2: by Astronautix.
  • RL10B-2 Pratt & Whitney: Link no longer active – Information and picture source (19 August 2007)

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