RE-M3 "Mainsail" Liquid Fuel Engine

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RE-M3 "Mainsail" Liquid Fuel Engine
Part image
Liquid fuel engine by
Rockomax Conglomerate

Radial size Medium, Large
Cost (total) 13 000.00 Funds
Mass (total) 6.00 t
Drag 0.2
Max. Temp. 2000 K
Volume  ?
Impact Tolerance 7 m/s
Research Heavier rocketry.png Heavier Rocketry
Unlock cost 38 000 Funds
Since version 0.16
Part configuration liquidEngineMainsail_v2.cfg
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 RE-M3 "Mainsail" Liquid Fuel Engine is one of the heaviest and most powerful large-diameter liquid fuel engines among the stock parts.

Product description

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

Rockomax Conglomerate


The Mainsail is usually 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. It has a reasonably high atmospheric Isp of 285 s, but a low vacuum Isp of 310 s.

It is a common choice for lifting large stacks of liquid fuel tanks into orbit and beyond, or propelling large heavy lift vehicles. As of version 1.11.1, this is one of four size 2 engines in the base game. 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. The specific impulse is also fairly good, though it can still consume large amounts 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 limiting the gimbaling is often recommended.

Appearance as of 1.3


  • The reskin also gave the Mainsail a new cfg file; the old one can be found here.


  • New texture and variants
  • Renamed from RE-M3 "Mainsail" Liquid Engine to RE-M3 "Mainsail" Liquid Fuel Engine
  • Cost increased (850 → 5650), specific impulse increased (280-330 → 320-360)
  • heatProduction reduced from 500 to 400, as a work around to heat transfer bugs with the Jumbo-64
  • Renamed from LV-T30 Liquid Fuel Engine to Rockomax "Mainsail" Liquid Engine, thrust increased (1200 → 1500), mass decreased (7 → 6), new description
  • Initial release