RL10A-4-1
Pratt & Whitney RL10A-4-1 is an expander-cycle liquid-hydrogen/liquid-oxygen RL10 variant used on the retired Atlas IIIA upper stage. NASA's RL10 evolution table lists the A-4 at 20,800 lbf (92.52 kN) vacuum thrust and approximately 449 s specific impulse; the exact Atlas IIIA installation is preserved separately.
Identity
- Domains
- spaceflight
- Identity Level
- variant
- Kind
- liquid-rocket-engine
- Name
- RL10A-4-1
- Status
- retired
Details
- Description
- Pratt & Whitney RL10A-4-1 is an expander-cycle liquid-hydrogen/liquid-oxygen RL10 variant used on the retired Atlas IIIA upper stage. NASA's RL10 evolution table lists the A-4 at 20,800 lbf (92.52 kN) vacuum thrust and approximately 449 s specific impulse; the exact Atlas IIIA installation is preserved separately.
- Developers
- Family
- Manufacturers
- Propellants
- liquid hydrogenliquid oxygen
- Rocket Specs
- Cycle
- expander cycle
- Vacuum Specific Impulse S
- 449
- Vacuum Thrust Kn
- 92.52
Links
- Official Url
- https://www.nro.gov/Launches/Launch-Vehicles/
Assets & Meta
- Creation Time
- July 29, 2026 at 09:02:57 UTC
- Updated Time
- August 22, 2026 at 11:05:11 UTC
Other
- Sources
- Accessed Date
- 2026-07-29
- Publisher
- NASA Technical Reports Server
- Title
- Cryogenic upper stage propulsion: RL10 and derivative engines
- Accessed Date
- 2026-07-29
- Note
- Supports the legacy vehicle installation and the narrow canonical identity used during migration.
- Publisher
- Official vehicle or program source
- Title
- Atlas IIIA official vehicle reference
- Accessed Date
- 2026-08-22
- Note
- NASA's RL10 evolution table lists the A-4 model at 20,800 lbf vacuum thrust and approximately 449 s specific impulse; 20,800 lbf is normalized to 92.52 kN.
- Publisher
- NASA Technical Reports Server
- Title
- Cryogenic upper stage propulsion: RL10 and derivative engines