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CR-7 R.A.P.I.E.R. Engine

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CR-7 R.A.P.I.E.R. Engine
Part image
Hybrid engine by
C7 Aerospace Division and Rockomax Conglomerate
Radial size Small
Cost (total) 6 000.00 Fund
Mass (total) 2.00 t
Drag 0.2
Max. Temp. 2000 K
Impact Tolerance 20 m/s
Research Aerospace tech.png Aerospace Tech
Unlock cost 35000 Fund
Since version 0.23
Part configuration rapierEngine
Testing environments
On the surface ✓ Yes
In the ocean ✓ Yes
On the launchpad ✓ Yes
In the atmosphere ✓ Yes
Sub orbital × No
In an orbit × No
On an escape × No
Docked × No
Test by staging ✓ Yes
Manually testable ✓ Yes
Liquid fuel engine
Maximum thrust (1 atm) 162.30 kN
(vacuum) 180.00 kN
Isp (1 atm) 275 s
(vacuum) 305 s
Fuel con­sumption 12.02 units of fuel/s

Thrust vectoring 3 °
Jet engine
Maximum thrust 105 kN
Isp (max) 3200 s
Fuel con­sumption 0.04 units of fuel/s
Intake air consumption 0.63 Air unit/s
Thrust vectoring 3 °

The CR-7 R.A.P.I.E.R. Engine (Reactive Alternate-Propellent Intelligent Engine for Rockets) is a hybrid engine. It can change between an airbreathing jet and a liquid fuel engine. It has the feature to auto adjust, changing between jet and rocket mode automatically when it runs out of intake air. This engine is an in-game counterpart of the real life SABRE engine, which is also visible in the naming as both are named after swords.

This is the first stock engine which has multiple engines incorporated into one part (four in this case).

This is the first engine which has two different manufacturers. Prior to 0.24 one of the manufacturers seems to be misspelled. Instead of Rockomax Conglomerate an o was missing attributing it to the Rockmax Conglomerate. However, the description text used the common spelling and the manufacturer entry was fixed in 0.24.


This engine has two modes of operation. An AirBreathing mode in which it runs on liquid fuel and intake air like a jet engine and a ClosedCycle mode in which it runs on liquid fuel and oxidizer like a rocket engine. The engine can either be set to switch automatically to closed-cycle when the intake air runs out or it can be switched manually between the two modes. The hybrid feature makes this engine especially useful for single-stage-to-orbit designs as it saves the weight of a separate engine.

This engine is one of the few engines that do not provide electric charge when active, another example being the LV-909 engine.

Unlike the other jet engines, the R.A.P.I.E.R. has a rear mounting point.


Like other jet engines, the air-breathing mode only works in the atmospheres of Kerbin or Laythe. The air-breathing mode has lower specific impulse than the other jets, though still a order of magnitude higher than most rocket engines. On the other hand, it delivers better performance than the J-X4 "Whiplash" Turbo Ramjet Engine at high speeds (~1000 m/s and higher) and altitudes (~17 km and higher), making it a good choice for high-speed atmospheric flight. Top speed is ~2,100 m/s in kerbins atmosphere(mach 6.2)


The closed-cycle performance is merely mediocre. Its specific impulse is in the middle of the pack compared to other rocket engines. As a pure rocket, its thrust-to-weight ratio is worse than any conventional rocket. However, the R.A.P.I.E.R. is lighter and more compact than having a separate jet engine and rocket, and has relatively higher ISP than most rocket engines. This makes the R.A.P.I.E.R a good choice for single-stage-to-orbit (SSTO) where use of the rocket can be kept to a minimum, but not practical for extended spaceflight.

Product description

The R.A.P.I.E.R. (Reactive Alternate-Propellant Intelligent Engine for Rockets) is a joint venture between C7 Aerospace and the Rockomax Conglomerate. Designed to fill a gap in the design requirements for sustainable single stage to orbit aircraft, this engine combines the best of rocket and air-breathing thrust technology.


  • Jet engine Isp halved, thrust reduced
  • Mass increased from 1.2 to 2.0; cost increased from 3600 to 6000; maximum jet thrust reduced from 190 to 140; maximum liquid fuel thrust increased from 175 to 180.
  • Cost decreased from 5900 to 3600 (and made meaningful), manufacturer name fixed, mass decreased from 1.75 to 1.2
  • Initial release