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S3 KS-25x4 Engine Cluster

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S3 KS-25x4 Engine Cluster
Part image
Liquid fuel engine by
Radial size Extra large
Cost (total) 32 400.00 Fund
Mass (total) 9.75 t
Drag 0.2
Max. Temp. 3600 K
Impact Tolerance 20 m/s
Research Tech tree very heavy rocketry.png Very Heavy Rocketry
Unlock cost 65000 Fund
Since version 0.23.5
Part configuration Size3EngineCluster
Maximum thrust 3200 kN
Isp (1 atm) 320 s
(vacuum) 360 s
Fuel con­sumption (1 atm) 203.67 l/s
(vacuum) 181.04 l/s
Thrust vectoring 0.5 °
On the surface ✓ Yes
On the ocean ✓ Yes
In atmosphere ✓ Yes
In space ✓ Yes
Staging ✓ Yes
Event ✓ Yes

The S3 KS-25x4 Engine Cluster is a liquid fuel engine with four nozzles. This is the engine with the highest thrust and, compared to the thrust, high specific impulse. It doesn't allow placing additional stages beneath the engine cluster. This is the second liquid fuelled engine after the R.A.P.I.E.R. Engine which uses multiple nozzles.

The KS-25 might be a reference to the Space Shuttle Main Engines which are also named RS-25, especially as it was introduced as a Space Launch System component which uses four RS-25 engines.

It is the most expensive part in the game.

Product description

Designed for usage as a first stage, this engine uses four of Kerbodyne's KS-25 rocket motors. This is the first in a series of designs that move away from the pattern of simply increasing the engine and nozzle size on a rocket.


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