ABOUT MERLIN 1D VACUUM
The Merlin 1D Vacuum (MVac) is the vacuum-optimized variant of the Merlin 1D, featuring a larger niobium alloy nozzle extension for improved performance in the vacuum of space. It powers the second stage of both Falcon 9 and Falcon Heavy. The extended nozzle significantly increases specific impulse compared to the sea-level variant.
Image: SpaceX
PERFORMANCE
| Thrust (Sea Level) | N/A (vacuum only) kN |
| Thrust (Vacuum) | 981 kN (220,500 lbf) kN |
| ISP (Sea Level) | N/A s |
| ISP (Vacuum) | 348 s s |
| Chamber Pressure | 9.7 MPa (1,410 psi) bar |
| Mass | 490 kg |
| Thrust-to-Weight | 204 |
| Throttle Range | 60–100% |
| Restart Capable | Yes (multiple) |
THRUST CONVERSIONS (VACUUM)
| Kilonewtons | 981.0 kN |
| Pounds-force | 220,538 lbf |
ENGINE CYCLE
Gas Generator
A gas generator cycle taps off a small portion of propellants to drive turbopumps via a separate combustion chamber. The turbine exhaust is dumped overboard, making it less efficient but simpler and more reliable. Used by the Merlin, F-1, and RS-27.
PROPULSION
| Propellant | RP-1 |
| Oxidizer | LOX |
| Engine Cycle | Gas Generator |
| Mixture Ratio | 2.36:1 |
| Flow Rate | ~280 kg/s kg/s |
PHYSICAL
| Dimensions | 0.92 m diameter × 3.5 m length (with nozzle extension) |
| Combustion Chambers | 1 |
| Nozzle Expansion Ratio | 165:1:1 |
GENERAL
| Manufacturer | SpaceX |
| Country | United States |
| Status | Active |
| First Flight | April 25, 2026 |
VARIANTS (2)
- Merlin 1D Vacuum
- Merlin 1D Vacuum+
VEHICLES USING MERLIN 1D VACUUM (2)
- Falcon 9 (second stage)
- Falcon Heavy (second stage)
ENGINE LINEAGE
Merlin 1C Vacuum→Merlin 1D Vacuum
⚖ PROPELLANTS
🏢 MANUFACTURER
