Merlin Vacuum
SpaceX Merlin Vacuum (MVac) gas-generator engine is the single restartable upper-stage engine for Falcon 9 and Falcon Heavy. SpaceX specifies liquid oxygen/RP-1 propellants, a fixed 165:1 expansion nozzle, dual redundant TEA-TEB igniters for restart reliability, and 981 kN (220,500 lbf) second-stage thrust; the vacuum-optimized configuration is distinct from sea-level Merlin 1D.
Identity
- Domains
- spaceflight
- Identity Level
- variant
- Kind
- liquid-rocket-engine
- Name
- Merlin Vacuum
- Status
- active
Details
- Description
- SpaceX Merlin Vacuum (MVac) gas-generator engine is the single restartable upper-stage engine for Falcon 9 and Falcon Heavy. SpaceX specifies liquid oxygen/RP-1 propellants, a fixed 165:1 expansion nozzle, dual redundant TEA-TEB igniters for restart reliability, and 981 kN (220,500 lbf) second-stage thrust; the vacuum-optimized configuration is distinct from sea-level Merlin 1D.
- Developers
- Family
- Manufacturers
- Propellants
- RP-1liquid oxygen
- Rocket Specs
- Cycle
- gas-generator
- Restartable
- Yes
- Vacuum Thrust Kn
- 981
Links
- Official Url
- https://www.spacex.com/vehicles/falcon-9/
Assets & Meta
- Creation Time
- July 29, 2026 at 08:54:09 UTC
- Updated Time
- August 22, 2026 at 01:15:32 UTC
Other
- Sources
- Accessed Date
- 2026-07-29
- Note
- FAA historical launch documentation supports the Falcon 9 v1.1 vehicle installation using a Merlin Vacuum upper-stage engine.
- Publisher
- Federal Aviation Administration
- Title
- Falcon 9 v1.1 official vehicle reference
- Accessed Date
- 2026-07-29
- Note
- FAA historical launch documentation supports the Falcon 9 v1.0 vehicle installation using a Merlin Vacuum upper-stage engine.
- Publisher
- Federal Aviation Administration
- Title
- Falcon 9 v1.0 official vehicle reference
- Accessed Date
- 2026-08-21
- Note
- SpaceX identifies one Merlin Vacuum engine on the Falcon 9 second stage, with 981 kN (220,500 lbf) vacuum thrust and multiple restart capability.
- Publisher
- Space Exploration Technologies Corp.
- Title
- Falcon 9
- Accessed Date
- 2026-08-21
- Note
- SpaceX identifies one Merlin Vacuum engine on Falcon Heavy's second stage at 981 kN (220,500 lbf) thrust.
- Publisher
- Space Exploration Technologies Corp.
- Title
- Falcon Heavy
- Accessed Date
- 2026-08-21
- Note
- SpaceX's Falcon Payload User's Guide specifies one MVac second-stage engine, 981 kN vacuum stage thrust, a fixed 165:1 expansion nozzle, and restart capability.
- Publisher
- Space Exploration Technologies Corp.
- Title
- Falcon Payload User's Guide