S3 KS-25x4 "Mammoth" Liquid Fuel Engine

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S3 KS-25x4 "Mammoth" Liquid Fuel Engine
Part image
Liquid fuel engine by
Radial size Extra large
Cost (total) 39 000.00 Funds
Mass (total) 15.00 t
Drag 0.2
Max. Temp. 2000 K
Impact Tolerance 20 m/s
Research Tech tree very heavy rocketry.png Very Heavy Rocketry
Unlock cost 115 000 Funds
Since version 0.23.5
Part configuration Size3EngineCluster
Liquid fuel engine
Maximum thrust (1 atm) 3 746.03 kN
(vacuum) 4 000.00 kN
Isp (1 atm) 295 s
(vacuum) 315 s
Fuel consumption 258.98 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 S3 KS-25x4 "Mammoth" Liquid Fuel Engine is a liquid fuel engine with four nozzles. It is currently the most expensive part and the most powerful engine available in the game. It has the highest specific impulse at sea level of any liquid fuel engine, tied with that of its counterpart, the S3 KS-25 "Vector" Liquid Fuel Engine, making it an effective engine for S.S.T.O vehicles. There are no attachment nodes for placing additional stages beneath the engine cluster. This is the second liquid fueled engine after the R.A.P.I.E.R. Engine which uses multiple nozzles. According to the part description. the engine is assembled from four S3 KS-25 "Vector" Liquid Fuel Engines.

KS-25 is a reference to RS-25, the official designation of the Space Shuttle Main Engines. The part, which uses four KS-25 engines, is inspired by the main engine component of the Space Launch System, which similarly uses four RS-25 engines. The part was introduced along with several other SLS-inspired parts.

Product description

Kerbodyne engineers got fed up with having to contend with overly complicated staging arrays for lifting heavy payloads, and decided instead to just build a truly enormous engine of the highest efficiency. Strapping together four of Kerbodyne's KS-25 rocket motors in a single assembly, they created the largest rocket engine in production anywhere, and each KS-25 has the highest chamber pressure--the reason for four small nozzles and combustion chambers, not one big one (those kept going boom). It's certainly got the power to match its size, and although it excels in its main role as a first-stage engine, the lack of structural hardpoints on its underside makes it quite less suitable for other purposes. Its price tag also seems to match its size, in fact.



  • Cost increased from 5900 to 32400 (and made meaningful)
  • Initial release