RE-M3 "Mainsail" Liquid Engine

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RE-M3 "Mainsail" Liquid Engine
Part image
Liquid fuel engine by
Rockomax Conglomerate
Radial size Large
Cost (total) 13 000.00 Funds
Mass (total) 6.00 t
Drag 0.2
Max. Temp. 2000 K
Impact Tolerance 7 m/s
Research Heavier rocketry.png Heavier Rocketry
Unlock cost 38 000 Funds
Since version 0.16
Part configuration liquidEngineMainsail
Liquid fuel engine
Maximum thrust (1 atm) 1 379.03 kN
(vacuum) 1 500.00 kN
Isp (1 atm) 285 s
(vacuum) 310 s
Fuel consumption 98.68 Units of fuel/s

Thrust vectoring 2 °
Testing Environments
On the surface ✓ Yes
In the ocean ✓ Yes
On the launchpad ✓ Yes
In the atmosphere ✓ Yes
Sub orbital ✓ Yes
In an orbit ✓ Yes
On an escape ✓ Yes
Docked × No
Test by staging ✓ Yes
Manually testable ✓ Yes

The Rockomax "Mainsail" Liquid Engine is used to provide thrust for larger rockets and lower stages. It is typically fueled by large diameter liquid fuel tanks like the Rockomax X200-32 Fuel Tank.


The Mainsail is the most common choice for lifting large stacks of liquid fuel tanks into orbit and beyond, or propelling large heavy lift vehicles. As of 0.22[outdated], this is one of three size 2 engines, and it is the highest thrust stock part. The thrust vectoring also gives it good pitch and yaw control, greatly easing first stage stability, though care must be taken to not allow S.A.S. to tear the ship apart. The thrust-to-weight ratio of this engine is excellent. However, the Mainsail suffers from a rather low specific impulse, especially in a vacuum and consumes large amount of fuel.

The high thrust of this engine, combined with thrust vectoring can destroy poorly built rockets in the middle of ascents. Throttling down or locking the vectoring is often recommended. As of 0.22[outdated], the Mainsail no longer tends to quickly explode from overheating when run on maximum throttle and placed under a Rockomax Jumbo-64 Fuel Tank, though other parts may encounter the same bug. Placing a small strut or fuel tank between the engine and the Jumbo-64 will mitigate this.


A monster of an engine for heavy lifting purposes, the Mainsail's power rivals that of entire small nations.

Rockomax Conglomerate


  • heatProduction reduced from 500 to 400, as a work around to heat transfer bugs with the Jumbo-64
  • (Undocumented) Renamed, thrust increased (1200 → 1500), mass decreased (7 → 6), new description
  • Initial release