RL10A-4
Pratt & Whitney RL10A-4 is a cryogenic upper-stage engine variant used by the retired Atlas IIA and Atlas IIAS launch vehicles. The RL10 evolution table in a 1991 Pratt & Whitney presentation archived by NASA lists the A-4 at 20,800 lbf vacuum thrust, approximately 92.52 kN, and approximately 449 s specific impulse.
Identity
- Domains
- spaceflight
- Identity Level
- variant
- Kind
- liquid-rocket-engine
- Name
- RL10A-4
- Status
- retired
Details
- Description
- Pratt & Whitney RL10A-4 is a cryogenic upper-stage engine variant used by the retired Atlas IIA and Atlas IIAS launch vehicles. The RL10 evolution table in a 1991 Pratt & Whitney presentation archived by NASA lists the A-4 at 20,800 lbf vacuum thrust, approximately 92.52 kN, and approximately 449 s specific impulse.
- Family
- Propellants
- liquid hydrogenliquid oxygen
- Rocket Specs
- Vacuum Specific Impulse
- …
- Vacuum Thrust
- …
Links
Assets & Meta
- Creation Time
- July 29, 2026 at 09:02:54 UTC
- Updated Time
- October 29, 2026 at 13:16:26 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 for migration.
- Publisher
- Official vehicle or program source
- Title
- Atlas IIAS official vehicle reference