Reaction engine

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A reaction engine is an engine that generates thrust solely through the use of onboard propellant. Unlike jet engines, which require an oxygen-rich atmosphere to operate, rocket engines are able to function where no oxygen is present. If a reaction engine involves chemical combustion it is called a rocket engine.

Physics

All reaction engine work with the same principle: mass is propelled out of the nozzle which accelerates the vehicle due to Newton's third law of motion. Every engine in the game uses this basic principle, differing in the environments in which they will function (jet engines require an oxygen-rich atmosphere), the types of fuel they consume (ion engines require the vehicle to mount xenon tanks), and the game controls which activate them (RCS thrusters respond to directional controls, all others respond to the throttle).

Solid fuel rocket engines

→ Main article: Solid rocket booster

The most basic type is the solid fuel rocket, which is simply a solid, self-oxidizing compound or mixture within a casing with a nozzle at the rear to allow the gases produced to escape.

Advantages

  • Very high thrust-to-weight ratio.
  • Engine and fuel tank are combined in one part, lowering part count and simplifying design.

Disadvantages

  • Cannot be throttled or switched off after ignition.
  • Cannot be refueled or use fuel stored elsewhere on the craft.
  • Low efficiency compared to other types of engines.
Available solid fuel rocket engines
Solid Fuel Density is 7.5 kg/unit Mass
(t)
Fuel
(Units of fuel)
Thrust
(kN)
TWR Isp (s) Burn
(s)
Full Empty
Image Part Radial size Cost
(Funds)
Full Empty Max. Temp.
(K)
Tolerance
(m/s)
Tolerance
(g)
atm vac atm vac atm vac atm vac
RT-5 White.png
RT-5 "Flea" Solid Fuel Booster Small, Radial mounted 200
(116)
1.50 0.45 2 000 7 50 140 162.91 192.0 11.07 13.05 36.92 43.51 140 165 8.8
RT-10 White.png
RT-10 "Hammer" Solid Fuel Booster Small, Radial mounted 400
(175)
3.56 0.75 2 000 7 50 375 197.90 227.0 5.66 6.50 26.91 30.86 170 195 23.7
BACC SFB.png
BACC "Thumper" Solid Fuel Booster Small, Radial mounted 850
(358)
7.65 1.50 2 200 7 50 820 250.00 300.0 3.33 4.00 17.00 20.39 175 210 42.2
SRB.png
S1 SRB-KD25k "Kickback" Solid Fuel Booster Small, Radial mounted 2 700
(1 140)
24.00 4.50 2 200 7 50 2 600 593.86 670.0 2.52 2.85 13.46 15.18 195 220 62.8
Sepratron.png
Sepratron I Radial mounted 75
(70.2)
0.0725 0.0125 2 000 7 50 8 13.79 18.0 19.40 25.32 112.51 146.84 118 154 5.0
Mite.png
FM1 "Mite" Solid Fuel Booster Tiny, Radial mounted 75
(51.0)
0.375 0.075 2 200 7 50 40 11.012 12.5 2.93 3.33 14.68 16.66 185 210 49.44
Shrimp.png
F3S0 "Shrimp" Solid Fuel Booster Tiny, Radial mounted 150
(96.0)
0.875 0.155 2 200 7 50 90 26.512 30.0 3.22 3.65 17.1 19.35 190 215 47.44
Thorougbred.png
S2-17 "Thoroughbred" Solid Fuel Booster Large, Radial mounted 9 000
(4 200.0)
70.00 10.00 2 200 10 50 8 000 1 515.217 1 700.0 2.16 2.43 15.15 17.0 205 230 79.6
Clydesdale.png
S2-33 "Clydesdale" Solid Fuel Booster Large, Radial mounted 18 500
(8 660.0)
144.00 21.00 2 200 10 50 16 400 2 948.936 3 300.0 2.05 2.29 14.04 15.71 210 235 85.9

Liquid fuel rocket engines

Liquid fuel engines are powered by liquid fuel ignited with oxidizer. In the real world typical liquid fuels are liquid hydrogen or kerosene, and typical oxidizers are liquid oxygen or nitrous-oxide. All engines use Bell nozzles except the aerospike engine.

The LV-N Atomic Rocket Motor would not be classified as a liquid engine in the real world, but it is here to simply the gameplay and Squad's development work.

Advantages

  • Fuel and oxidizer can be moved between tanks. This opens many possibilities for fuel management and logistics, including replenishing the fuel supply of a craft already in flight.
  • Engines and fuel need not be mounted in the same location on the ship, expanding design possibilities.
  • Variable throttle allows different levels of thrust at different times, or for the engines to be shut down entirely and restarted later in the flight.
  • Some liquid engines have gimbals which allows them to help steer the craft.
  • Available in a wide range of thrusts and efficiencies, all of which may share fuel with each other.

Disadvantages

  • Lower thrust-to-weight ratio compared to solid rocket engines.
  • Separation of engine and fuel leads to increased part count (excepting the KR-1x2).
Available liquid fuel rocket engines
Thrust
(kN)
T/W
ratio
Max. Fuel
Consumption
(Units of fuel/s)
Isp (s) TVC
Image Part Radial size Cost
(Funds)
Mass
(t)
Max. Temp.
(K)
Tolerance
(m/s)
Tolerance
(g)
atm vac atm vac atm vac Gimbal
(°)
LV-1R Shroud.png
LV-1R "Spider" Liquid Fuel Engine Radial mounted 120 0.02 2 000 7 50 1.79 2.0 9.14 10.20 0.141 260 290 10.0
24-77 Orange.png
24-77 "Twitch" Liquid Fuel Engine Radial mounted 230 0.08 2 000 7 50 15.17 16.0 19.34 20.39 1.125 275 290 8.0
Mk-55 Radial mount engine.png
Mk-55 "Thud" Liquid Fuel Engine Radial mounted 820 0.90 2 000 7 50 108.20 120.0 12.26 13.60 8.024 275 305 8.0
O-10.png
O-10 "Puff" MonoPropellant Fuel Engine[Note 1] Radial mounted 150 0.09 2 000 7 50 9.60 20.0 10.88 22.66 2.039 120 250 6.0
LV-1 Shroud.png
LV-1 "Ant" Liquid Fuel Engine Tiny, Radial mounted 110 0.02 2 000 7 50 0.51 2.0 2.59 10.20 0.129 80 315
48-7S Shroud.png
48-7S "Spark" Liquid Fuel Engine Tiny 240 0.13 2 000 7 50 16.56 20.0 12.99 15.69 1.275 265 320 3.0
LV-909 Shroud.png
LV-909 "Terrier" Liquid Fuel Engine Small 390 0.50 2 000 7 50 14.78 60.0 3.01 12.24 3.547 85 345 4.0
LV-T30 Liquid Fuel Engine recent.png
LV-T30 "Reliant" Liquid Fuel Engine Small 1 100 1.25 2 000 7 50 205.16 240.0 16.74 19.58 15.789 265 310
LV-T45 LFE.png
LV-T45 "Swivel" Liquid Fuel Engine Small 1 200 1.50 2 000 7 50 167.97 215.0 11.42 14.62 13.703 250 320 3.0
KS-25 LFE.png
S3 KS-25 "Vector" Liquid Fuel Engine Small, Radial mounted 18 000 4.00 2 000 22 50 936.51 1 000.0 23.87 25.49 64.745 295 315 10.5
ToroidalAerospikeLiquidFuelEngine.png
T-1 Toroidal Aerospike "Dart" Liquid Fuel Engine Small, Radial mounted 3 850 1.00 2 000 20 50 153.53 180.0 15.66 18.35 10.797 290 340
LV-N Atomic.png
LV-N "Nerv" Atomic Rocket Motor[Note 2] Small 10 000 3.00 2 500 12 50 13.88 60.0 0.47 2.04 1.530 185 800
RE-L10.png
RE-L10 "Poodle" Liquid Fuel Engine Large 1 300 1.75 2 000 7 50 64.29 250.0 3.75 14.57 14.568 90 350 4.5
SkipperV2.png
RE-I5 "Skipper" Liquid Fuel Engine Large 5 300 3.00 2 000 8 50 568.75 650.0 19.33 22.09 41.426 280 320 2.0
MainsailV2.png
RE-M3 "Mainsail" Liquid Fuel Engine Large 13 000 6.00 2 000 7 50 1 379.03 1 500.0 23.44 25.49 98.683 285 310 2.0
LFB KR-1x2.png
LFB KR-1x2 "Twin-Boar" Liquid Fuel Engine[Note 3] Large, Radial mounted 17 000
(14 062.4)
42.50
(10.50)
2 000 20 50 1 866.67 2 000.0 4.48
(18.13)
4.80
(19.42)
135.964 280 300 1.5
Big1.png
Kerbodyne KR-2L+ "Rhino" Liquid Fuel Engine Extra large 25 000 9.00 2 000 7 50 1 205.88 2 000.0 13.66 22.66 119.968 205 340 4.0
Quad.png
S3 KS-25x4 "Mammoth" Liquid Fuel Engine Extra large 39 000 15.00 2 000 20 50 3 746.03 4 000.0 25.47 27.19 258.978 295 315 2.0
Rapier Engine 01.png
CR-7 R.A.P.I.E.R. Engine[Note 4] Small 6 000 2.00 2 000 20 50 162.30 180.0 8.27 9.18 12.036 275 305 3.0
  1. Consumes monopropellant. (the density of monopropellant is less: 4kg/unit)
  2. Consumes liquid fuel only.
  3. The LFB KR-1x2 is a liquid fuel booster -- a combination of a "normal" engine and a fuel tank.
  4. The R.A.P.I.E.R. Engine is a combination of liquid fuel and jet engine. Only the liquid fuel engine properties are shown.
Available liquid fuel tanks
Liquid fuel and oxidizer density are both 5 kg/unit Mass
(t)
Liquid
Fuel

(Units of fuel)
Oxidizer
(Units of fuel)
Image Part Radial size Cost
(Funds)
Full Empty Max. Temp.
(K)
Tolerance
(m/s)
Tolerance
(g)
R-4 FT.png
R-4 'Dumpling' External Tank X 50
(39.90)
0.1238 0.0138 2 000 5 50 9.9 12.1
R-11 FT.png
R-11 'Baguette' External Tank X 50
(25.21)
0.3038 0.0338 2 000 5 50 24.3 29.7
R-12 FT.png
R-12 'Doughnut' External Tank Small 147
(119.46)
0.3375 0.0375 2 000 6 50 27 33
Oscar-B FT.png
Oscar-B Fuel Tank Tiny 70
(51.64)
0.225 0.025 2 000 6 50 18 22
FL-T100 Dark.png
FL-T100 Fuel Tank Small 150
(104.1)
0.5625 0.0625 2 000 6 50 45 55
FL-T200 Dark.png
FL-T200 Fuel Tank Small 275
(183.2)
1.125 0.125 2 000 6 50 90 110
FL-T400 Dark.png
FL-T400 Fuel Tank Small 500
(316.4)
2.25 0.25 2 000 6 50 180 220
FL-T800 Dark.png
FL-T800 Fuel Tank Small 800
(432.8)
4.5 0.5 2 000 6 50 360 440
X200-8 White.png
Rockomax X200-8 Fuel Tank Large 800
(432.8)
4.5 0.5 2 000 6 50 360 440
X200-16 White.png
Rockomax X200-16 Fuel Tank Large 1 550
(815.6)
9 1 2 000 6 50 720 880
X200-32 White.png
Rockomax X200-32 Fuel Tank Large 3 000
(1 531.2)
18 2 2 000 6 50 1 440 1 760
Jumbo-64 White.png
Rockomax Jumbo-64 Fuel Tank Large 5 750
(2 812.4)
36 4 2 000 6 50 2 880 3 520
Kerbodyne S3-3600 Tank.png
Kerbodyne S3-3600 Tank Extra large 3 250
(1 597.6)
20.25 2.25 2 000 6 50 1 620 1 980
Kerbodyne S3-7200 Tank.png
Kerbodyne S3-7200 Tank Extra large 6 500
(3 195.2)
40.5 4.5 2 000 6 50 3 240 3 960
Kerbodyne S3-14400 Tank.png
Kerbodyne S3-14400 Tank Extra large 13 000
(6 390.4)
81 9 2 000 6 50 6 480 7 920
Mk2 LF+O Fuselage Short.png
Mk2 Rocket Fuel Fuselage Short Mk2 750
(566.4)
2.29 0.29 2 500 50 50 180 220
Mk2 LF+O Fuselage.png
Mk2 Rocket Fuel Fuselage Mk2 1 450
(1 082.8)
4.57 0.57 2 500 50 50 360 440
Mk3 Rocket Fuel Fuselage Short.png
Mk3 Rocket Fuel Fuselage Short Mk3 2 500
(1 352.5)
14.29 1.79 2 700 50 50 1 125 1 375
Mk3 Rocket Fuel Fuselage.png
Mk3 Rocket Fuel Fuselage Mk3 5 000
(2 705)
28.57 3.57 2 700 50 50 2 250 2 750
Mk3 Rocket Fuel Fuselage Long.png
Mk3 Rocket Fuel Fuselage Long Mk3 10 000
(5 410)
57.14 7.14 2 700 50 50 4 500 5 500
C7 Brand Adapter - 2.5m to 1.25m.png
C7 Brand Adapter - 2.5m to 1.25m Small, Large 800
(433.0)
4.57 0.57 2 300 20 50 360 440
C7 Brand Adapter Slanted - 2.5m to 1.25m.png
C7 Brand Adapter Slanted - 2.5m to 1.25m Small, Large 800
(433.0)
4.57 0.57 2 300 20 50 360 440
Mk2 to 1.25m Adapter.png
Mk2 to 1.25m Adapter Small, Mk2 550
(366.4)
2.29 0.29 2 500 50 50 180 220
Mk2 to 1.25m Adapter Long.png
Mk2 to 1.25m Adapter Long Small, Mk2 1 050
(682.8)
4.57 0.57 2 500 50 50 360 440
Mk2 Bicoupler.png
Mk2 Bicoupler Small, Mk2 x 2 860
(676.4)
2.29 0.29 2 500 50 50 180 220
2.5m to Mk2 Adapter.png
2.5m to Mk2 Adapter Large, Mk2 800
(432.8)
4.57 0.57 2 500 50 50 360 440
Mk3 to Mk2 Adapter.png
Mk3 to Mk2 Adapter Mk2, Mk3 2 200
(1 282.0)
11.43 1.43 2 600 50 50 900 1 100
Mk3 to 2.5m Adapter.png
Mk3 to 2.5m Adapter Large, Mk3 2 500
(1 353.0)
14.29 1.79 2 600 50 50 1 125 1 375
Mk3 to 2.5m Adapter Slanted.png
Mk3 to 2.5m Adapter Slanted Large, Mk3 2 500
(1 353.0)
14.29 1.79 2 600 50 50 1 125 1 375
Mk3 to 3.75m Adapter.png
Mk3 to 3.75m Adapter Extra large, Mk3 2 500
(1 353.0)
14.29 1.79 2 600 50 50 1 125 1 375
ADTP-2-3 Gray.png
Kerbodyne ADTP-2-3 Large, Extra large 1 623
(246.0)
16.88 1.88 2 000 6 50 1 350 1 650

Ion engines

An ion engine uses electricity to ionize atoms of xenon gas and accelerate them in an electrostatic or electromagnetic field to propel them as exhaust. Remarkably little xenon gas fuel is needed, but ion engines are very demanding on electrical generation and storage.

Advantages

  • Extremely high efficiency, which is unaffected by atmosphere.

Disadvantages

  • Extremely low thrust. Ion engines cannot be used to lift off from most celestial bodies, and most maneuvers will take tens of minutes to complete.
  • High electric consumption.
  • No thrust vectoring currently available.
Available ion engines
Thrust
(kN)
TWR Isp (s) Max. Consumption
Image Part Radial size Cost
(Funds)
Mass
(t)
Max. Temp.
(K)
Tolerance
(m/s)
Tolerance
(g)
atm vac atm vac atm vac Electricity
(⚡/s)
Xenon
(Xenon unit/s)
PB-ION.png
IX-6315 "Dawn" Electric Propulsion System Tiny 8 000 0.25 2 000 7 50 0.048 2.0 0.019 0.816 100 4 200 8.741 0.486

RCS thrusters

RCS thrusters use their own fuel, monopropellant, and do not require a separate oxidizer. RCS is primarily used for steering a craft or making very small positional adjustments during docking; it is too weak and inefficient to function as a main maneuvering engine.

Advantages

Disadvantages

  • Very low thrust. The available RCS thrusters are too weak to lift off from most celestial bodies.
  • No thrust vectoring is available (however, the most commonly use thruster, the RV-105 RCS Thruster Block, can thrust in 4 directions).
  • The user can only switch engines on or off, while the SAS can run them on different thrust levels in between.
  • Low efficiency.
Available RCS engines
Image Part Radial size Cost
(Funds)
Mass
(t)
Max. Temp.
(K)
Tolerance
(m/s)
Tolerance
(g)
Thrust
(kN)
Fuel
(Units of fuel/s)
Isp (s) (atm) Isp (s) (vac)
RV-1X.png
RV-1X Variable Thruster Block Radial mounted 30 0.005 1 500 12 50 0.1 0.01 100 240
PlaceAnywhere1.png
Place Anywhere 1 Linear RCS Port Radial mounted 15 0.001 1 500 12 50 0.2 0.02 100 240
RV-105.png
RV-105 RCS Thruster Block Radial mounted 45 0.04 1 500 15 50 1.0 0.11 100 240
Linear RCS.png
Place-Anywhere 7 Linear RCS Port Radial mounted 25 0.02 2 600 15 50 2.0 0.21 100 240
Vernor.png
Vernor Engine[Note 1] Radial mounted 150 0.08 2 000 15 50 12.0 0.94 140 260
  1. The Vernor Engine uses a liquid fuel/oxidizer mixture.

See also