Difference between revisions of "Reaction engine"

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[[File:LV-T30 Liquid Fuel Engine.jpg|right|thumb|[[LV-T30 Liquid Fuel Engine]] before [[0.18]]]]
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[[File:LV-T30 Liquid Fuel Engine recent.png|right|thumb|200px|[[LV-T30 Liquid Fuel Engine]]]]
−
A '''reaction engine''' is an [[engine]] that works via “equal and opposite <u>reaction</u>” as in [[w:Newton%27s_laws_of_motion#Newton.27s_third_law|Newton's third law of motion]]. Specifically, they generate thrust by expelling reaction mass in the opposite direction as their acceleration. For our purposes, the reaction mass propelled outward is always a form of [[fuel]], though not always one modelled on ''chemical'' reactions.
+
A '''reaction engine''' is an [[engine]] that works via “equal and opposite reaction” as in [[w:Newton%27s_laws_of_motion#Newton.27s_third_law|Newton's third law of motion]]. Specifically, they generate thrust by expelling reaction mass in the opposite direction as their acceleration. In [[Kerbal Space Program]], the reaction mass propelled outward is always a form of [[fuel]], though not always one modeled on chemical reactions.
  
 
== Types ==
 
== Types ==
 
Different sources classify kinds of reaction engine a bit differently, but all contradistinguish those which must collect outside material from those using only onboard material as reaction mass.  
 
Different sources classify kinds of reaction engine a bit differently, but all contradistinguish those which must collect outside material from those using only onboard material as reaction mass.  
  
−
Staying relevant to KSP, we separate out [[intake air|air]]-breathing '''jet engines''' which can only operate inside an [[oxygen]]-rich [[atmosphere]]. All{{check version||0.90.0}} use the same [[resources]] and are controlled the same way.
+
Staying relevant to KSP, we separate out [[intake air|air]]-breathing '''jet engines''' which can only operate inside an [[oxygen]]-rich [[atmosphere]] from those able to operate in space. All{{check version||1.12.3}} use the same [[resources]] and are controlled the same way.
  
−
All{{check version||0.90.0}} KSP's other reaction engines can operate using only resources stored or generated onboard and are collectively called '''rocket engines'''. There are many types of rocket engines. They differ by the kind of fuel they use and the controls used to operate them in-game.  
+
All{{check version||1.12.3}} KSP's other reaction engines can operate using only resources stored or generated onboard and are collectively called '''rocket engines'''. There are many types of rocket engines. They differ by the kind of fuel they use and the controls used to operate them in-game.  
  
 
Listed below are general descriptions of jet engines and several broad types of rocket engines along with their advantages and disadvantages.
 
Listed below are general descriptions of jet engines and several broad types of rocket engines along with their advantages and disadvantages.
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----
 
----
 
{{main article|Jet engine}}
 
{{main article|Jet engine}}
 +
{| class="wikitable floatright"
 +
|-
 +
! Advantages !! Disadvantages
 +
|-
 +
| Excellent fuel efficiency || Efficiency changes with altitude
 +
|-
 +
| Excellent thrust-to-weight ratio || Thrust output changes with speed
 +
|-
 +
| Some engines provide thrust vectoring || Does not respond rapidly to throttle changes due to turbo lag
 +
|-
 +
| || Can only be used with an oxygenated atmosphere
 +
|-
 +
| || Engines available only in 0.625m, 1.25m, and 2.5m
 +
|}
 +
 
Jet engines use the same fuel as rocket engines, but unlike them jets draw oxygen from the atmosphere using [[air intake]]s rather than carrying the weight of oxidizer onboard. This is represented in-game by a much lower rate of fuel consumption. The classical rocket equation doesn't hold valid for them. In flight they face the trade-off between the lower atmosphere where [[intake air]] is easily available at lower speeds but air resistance is greater, and the upper atmosphere where there's less air resistance but higher speeds are required to collect sufficient intake air.
 
Jet engines use the same fuel as rocket engines, but unlike them jets draw oxygen from the atmosphere using [[air intake]]s rather than carrying the weight of oxidizer onboard. This is represented in-game by a much lower rate of fuel consumption. The classical rocket equation doesn't hold valid for them. In flight they face the trade-off between the lower atmosphere where [[intake air]] is easily available at lower speeds but air resistance is greater, and the upper atmosphere where there's less air resistance but higher speeds are required to collect sufficient intake air.
−
 
−
==== Advantages ====
 
−
* Excellent fuel efficiency within an oxygenated atmosphere
 
−
* Excellent power to weight ratio
 
−
* All current{{check version||0.90.0}} jet engines provide thrust vectoring for greater maneuverability
 
−
 
−
==== Disadvantages ====
 
−
* Cannot be used outside of an oxygenated atmosphere.
 
−
* Thrust output changes depending on speed
 
−
* Efficiency changes depending on altitude
 
−
* Engine requires time to “spool up” to maximum thrust potential
 
  
 
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{{FlipBox
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}}
 
}}
 
{{FlipBox
 
{{FlipBox
−
|title=Available "jet fuel" tanks
+
|title=Available jet fuel tanks
 
|content={{Stats Table Fuselage}}
 
|content={{Stats Table Fuselage}}
 
}}
 
}}
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----
 
----
 
{{Main article|Solid rocket booster}}
 
{{Main article|Solid rocket booster}}
−
The most basic type of rocket engine is the [[solid fuel]] rocket. Solid fuel is simply a self-oxidizing compound or mixture within a casing with a nozzle at the end to direct the exhaust gases produced. It offers no real control beyond choosing when to ignite it, though [[tweakables]] enable altering the thrust limit and total fuel.
 
  
−
==== Advantages ====
+
{| class="wikitable floatright"
−
* Very high [[thrust-to-weight ratio]]
+
|-
−
* Engine and fuel tank are combined in one part, lowering part count and simplifying design
+
! Advantages !! Disadvantages
 +
|-
 +
| High [[thrust-to-weight ratio]], especially in atmosphere || Cannot be throttled or switched off after ignition
 +
|-
 +
| Engine and fuel tank are a single unit || Cannot refuel or transfer fuel stored elsewhere on the craft
 +
|-
 +
| Cheap || Low efficiency compared to other types of engines
 +
|-
 +
| || No thrust vectoring
 +
|}
  
−
==== Disadvantages ====
+
The most basic type of rocket engine is the [[solid fuel]] rocket. Solid fuel is simply a self-oxidizing compound or mixture within a casing with a nozzle at the end to direct the exhaust gases produced. It offers no real control beyond choosing when to ignite it, though [[tweakables]] enable altering the thrust limit and total fuel.
−
* Cannot be throttled or switched off after ignition
 
−
* Cannot be refueled or transfer fuel stored elsewhere on the craft
 
−
* No thrust vectoring
 
−
* Low efficiency compared to other types of engines
 
  
 
{{FlipBox
 
{{FlipBox
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=== Liquid fuel rocket engines ===
 
=== Liquid fuel rocket engines ===
−
----
 
−
Liquid fuel engines utilize a mixture of [[liquid fuel]] and liquid [[oxidizer]] in a 9:11 ratio — generally called “rocket fuel”. The lone{{check version||0.90.0}} exception is the [[O-10 MonoPropellant Engine]] which uses [[monopropellant]].In the real world, typical liquid fuels are liquid hydrogen or kerosene, and typical oxidizers are liquid oxygen or nitrous-oxide.
 
  
−
All liquid fuel rocket engines can be staged and respond to [[throttle]] controls. All engines use [[w:Bell nozzle|Bell nozzles]] except the [[Toroidal Aerospike Rocket]].
+
{| class="wikitable floatright"
 +
|-
 +
! Advantages !! Disadvantages
 +
|-
 +
| Work both in vacuum and in atmosphere || Less efficient in atmosphere than jet engines, and less efficient in space than ion engines
 +
|-
 +
| Can be throttled to allow fine tuning of thrust || Lower [[thrust-to-weight ratio]] compared to solid rocket engines
 +
|-
 +
| Fuel and oxidizer can be moved between tanks or vessels || Separation of engine and fuel leads to increased part count |
 +
|-
 +
| Available in a wide range of shapes, sizes, and power levels || |
 +
|-
 +
| Frequently [[gimbals|gimballed]] to allow flight control || |
 +
|-
 +
| Immediate throttle response || |
 +
|}
  
−
The [[LV-N Atomic Rocket Motor]] was inspired by real-world nuclear thermal rockets, such as the [[w:NERVA|NERVA]]. In these, the propellant (typically liquid hydrogen) is heated by a nuclear reactor, rather than being combusted with an oxidizer, expanding into a high velocity jet of gaseous hydrogen. However, in order to reduce development effort and to simplify gameplay, [[Squad]] chose to have the LV-N to use the same rocket fuel mixture as other engines.
+
Most liquid fuel engines utilize a mixture of [[liquid fuel]] and liquid [[oxidizer]] in a 9:11 ratio — generally called “rocket fuel”. The exceptions{{check version||1.0.4}} are the [[O-10 MonoPropellant Engine]] which uses [[monopropellant]] and the [[LV-N "Nerv" Atomic Rocket Motor]] which only consumes liquid fuel (heating it in the core of a nuclear reactor rather than combusting it with oxidizer). The [[IX-6315 "Dawn" Electric Propulsion System]] uses [[xenon gas]] and [[electric charge]] to power it. This engine has a very low thrust, but is very efficient, with an [[Isp]] of over 1000 seconds. In the real world, typical liquid fuels are liquid hydrogen and a highly-refined kerosene blend called RP-1, and typical oxidizers are liquid oxygen and nitrous oxide.  
  
−
==== Advantages ====
+
All liquid fuel rocket engines can be staged and respond to [[throttle]] controls. All engines use [[w:Bell nozzle|Bell nozzles]] except the [[Toroidal Aerospike Rocket]].
−
* Work both in vacuum and in atmosphere
 
−
* 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
 
−
* Full thrust output on demand without “spool up” time like jets
 
−
* Some have [[Gimbal|gimbals]] giving thrust vectoring to help steer the craft
 
−
* Available in a wide range of thrusts and efficiencies, all using the same fuel supply
 
−
* Fuel and oxidizer can be moved between tanks or refuelled from another vessel during missions
 
−
* Engines and fuel need not be mounted in the same location on the ship, expanding design possibilities
 
−
 
 
−
==== Disadvantages ====
 
−
* Lower [[thrust-to-weight ratio]] compared to solid rocket engines
 
−
* Less efficient in atmosphere than jet engines
 
−
* Less efficient in space than ion engines
 
−
* Separation of engine and fuel leads to increased part count for all except the [[LFB KR-1x2|KR-1x2]].
 
  
 
{{FlipBox
 
{{FlipBox
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=== RCS thrusters ===
 
=== RCS thrusters ===
−
----
 
−
RCS thrusters make up the [[Reaction Control System]] designed primarily for translation maneuvers, especially useful during [[docking]]. They cannot be [[throttle]]d and are controlled with a separate set of keys from the pitch-yaw-roll keys. They use only [[monopropellant]] fuel, except for the [[Vernor Engine]] which uses rocket fuel.
 
  
−
==== Advantages ====
+
{| class="wikitable floatright"
−
* [[Monopropellant]] is automatically distributed throughout a craft, so neither crossfeeding or [[fuel line]]s have to be set up
+
|-
−
* Only engines that respond to translation controls
+
! Advantages !! Disadvantages
−
* Provide additional thrust for [[SAS]] to stabilize a craft
+
|-
 +
| [[Monopropellant]] is automatically routed || No throttle; either switched on or off
 +
|-
 +
| Offers rotation and translation maneuverability || Low thrust and low thrust-to-weight ratio
 +
|-
 +
| Offers additional thrust for SAS when reaction wheels cannot provide enough torque || Low fuel efficiency
 +
|}
 +
 
 +
RCS thrusters make up the [[Reaction Control System]] designed primarily for translation maneuvers, especially useful during [[docking]]. They cannot be [[throttle]]d and are controlled with a separate set of keys from the pitch-yaw-roll keys. They use only [[monopropellant]] fuel, except for the [[Vernor Engine]] which uses rocket fuel.  Monopropellant flows automatically from tanks mounted anywhere on a vessel to thrusters mounted anywhere on a vessel, so there is no need to set up fuel lines or mount thrusters directly on tanks if it is inconvenient or unsightly.
  
−
==== Disadvantages ====
+
In addition to separate thruster parts, the [[Mk1-3 Command Pod]] has its own built-in RCS thrusters, with the same power and I<sub>sp</sub> profile as the RC-105 RCS Thruster Block.
−
* Very low total thrust and thrust-to-weight ratio — too weak to escape from most [[celestial body|celestial bodies]].
 
−
* Low efficiency
 
−
* No thrust vectoring (however, the most commonly used 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
 
  
 
{{FlipBox
 
{{FlipBox
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=== Ion engines ===
 
=== Ion engines ===
−
----
+
 
 +
{| class="wikitable floatright"
 +
|-
 +
! Advantages !! Disadvantages
 +
|-
 +
| Extremely high efficiency || Extremely low thrust; inefficient for orbital transfers
 +
|-
 +
| Cool blue glow || Uncool excessive electric consumption
 +
|-
 +
| || No engine gimbal
 +
|-
 +
| || Xenon containers have lower mass ratio than rocket fuel tanks
 +
|}
 +
 
 
An ion engine uses [[electric charge]] to ionize atoms of [[xenon gas]] and accelerate them in an electrostatic or electromagnetic field to propel them as exhaust. Remarkably little xenon gas is needed, and probes equipped with just a few tanks are considered able to operate forever, or until something inevitably goes wrong. However, ion engines are very demanding on electrical generation and storage and very slow to accelerate.
 
An ion engine uses [[electric charge]] to ionize atoms of [[xenon gas]] and accelerate them in an electrostatic or electromagnetic field to propel them as exhaust. Remarkably little xenon gas is needed, and probes equipped with just a few tanks are considered able to operate forever, or until something inevitably goes wrong. However, ion engines are very demanding on electrical generation and storage and very slow to accelerate.
  
 
In real-life, they are often not considered true “rocket” engines. But given that they require no outside material or mass to operate, for ease and simplicity they are included with rocket engines on this wiki.
 
In real-life, they are often not considered true “rocket” engines. But given that they require no outside material or mass to operate, for ease and simplicity they are included with rocket engines on this wiki.
−
 
−
==== Advantages ====
 
−
* Extremely high efficiency
 
−
* Cool blue glow
 
−
==== Disadvantages ====
 
−
* Extremely low thrust; inefficient for Hohmann transfers
 
−
* High electric consumption
 
−
* No thrust vectoring currently{{check version||1.0.2}} available
 
−
* Propellant containers have poor mass ratio
 
  
 
{{Wikipedia|Hall effect thruster}}
 
{{Wikipedia|Hall effect thruster}}

Latest revision as of 10:46, 30 November 2022

LV-T30 Liquid Fuel Engine

A reaction engine is an engine that works via “equal and opposite reaction” as in Newton's third law of motion. Specifically, they generate thrust by expelling reaction mass in the opposite direction as their acceleration. In Kerbal Space Program, the reaction mass propelled outward is always a form of fuel, though not always one modeled on chemical reactions.

Types

Different sources classify kinds of reaction engine a bit differently, but all contradistinguish those which must collect outside material from those using only onboard material as reaction mass.

Staying relevant to KSP, we separate out air-breathing jet engines which can only operate inside an oxygen-rich atmosphere from those able to operate in space. All use the same resources and are controlled the same way.

All KSP's other reaction engines can operate using only resources stored or generated onboard and are collectively called rocket engines. There are many types of rocket engines. They differ by the kind of fuel they use and the controls used to operate them in-game.

Listed below are general descriptions of jet engines and several broad types of rocket engines along with their advantages and disadvantages.

Jet engines

→ Main article: Jet engine
Advantages Disadvantages
Excellent fuel efficiency Efficiency changes with altitude
Excellent thrust-to-weight ratio Thrust output changes with speed
Some engines provide thrust vectoring Does not respond rapidly to throttle changes due to turbo lag
Can only be used with an oxygenated atmosphere
Engines available only in 0.625m, 1.25m, and 2.5m

Jet engines use the same fuel as rocket engines, but unlike them jets draw oxygen from the atmosphere using air intakes rather than carrying the weight of oxidizer onboard. This is represented in-game by a much lower rate of fuel consumption. The classical rocket equation doesn't hold valid for them. In flight they face the trade-off between the lower atmosphere where intake air is easily available at lower speeds but air resistance is greater, and the upper atmosphere where there's less air resistance but higher speeds are required to collect sufficient intake air.

Available jet engines
Image Part Radial size Cost
(Funds)		 Mass
(t)		 Max. Temp.
(K)		 Tolerance
(m/s)		 Tolerance
(g) 		Thrust
(kN) 		TWR Fuel
(Units of fuel/s) 		Intake
(Air unit/s) 		Isp (s) TVC
(°) 		Reverse
J90JunoBasicJetEngine.png
 J-20 "Juno" Basic Jet Engine Tiny 450 0.25 2 000 7 50 20.0 Mach 0
20.6 Mach 1.3 		8.16 Mach 0
8.40 Mach 1.3 		0.064 1.402 6 400 — No
J33WheesleyBasicJetEngine.png
 J-33 "Wheesley" Turbofan Engine Small 1 400 1.5 2 000 7 50 120.0 Mach 0 8.16 Mach 0 0.233 29.601 10 500 — Yes
J404PantherAfterburningTurbofan.png
 J-404 "Panther" Afterburning Turbofan Small 2 000 1.2 2 000 7 50 85.00 Mach 0
107.89 Mach 1.75 /
130.00 Mach 0
219.48 Mach 2.5 		7.22 Mach 0
9.17 Mach 1.75 /
11.05 Mach 0
18.65 Mach 2.5 		0.193 /
0.663 		7.705 /
7.954 		9 000 /
4 000 		10.0 No
JX4WhiplashTurboRamjetEngine.png
 J-X4 "Whiplash" Turbo Ramjet Engine Small 2 250 1.8 2 000 7 50 130.00 Mach 0
386.66 Mach 3.0 		7.36 Mach 0
21.90 Mach 3.0 		0.663 5.303 4 000 1.0 No
J-90 Goliath Turbofan Engine.png
 J-90 "Goliath" Turbofan Engine Radial mounted 2 600 4.5 2 000 7 50 360.0 Mach 0 8.16 Mach 0 0.583 132.273 12 600 — Yes
Rapier Engine 01.png
 CR-7 R.A.P.I.E.R. Engine[Note 1] Small 6 000 2.0 2 000 20 50 105.00 Mach 0
465.64 Mach 3.75 		5.35 Mach 0
23.74 Mach 3.75 		0.669 4.015 3 200 3.0 No
  1. ↑ The R.A.P.I.E.R. Engine is a combination of liquid fuel and jet engine. Only the jet engine properties are shown.
Available jet fuel tanks
Liquid Fuel Density is 5 kg/unit Mass
(t) 		Liquid
Fuel
(Units of fuel)
Image Part Radial size Cost
(Funds)		 Full Empty Max. Temp.
(K)		 Tolerance
(m/s)		 Tolerance
(g)
Engine Nacelle.png
 Engine Nacelle[Note 1] Small 600
(480) 		0.925 0.15 2 000 10 50 150
Engine Pre-cooler.png
 Engine Pre-cooler[Note 1] Small 1 650
(1 618) 		0.375 0.15 2 000 10 50 40
Mk1 Fuselage-Intake.png
 Mk1 Diverterless Supersonic Intake[Note 1] Small 720
(560) 		1.18 0.17 2 000 10 50 200
Mk0LiquidFuelFuselage.png
 Mk0 Liquid Fuel Fuselage Tiny 200
(160) 		0.275 0.025 2 000 10 50 50
Mk1 Liquid Fuel Fuselage.png
 Mk1 Liquid Fuel Fuselage Small 550
(230) 		2.25 0.25 2 000 10 50 400
Mk2 Liquid Fuselage Short.png
 Mk2 Liquid Fuel Fuselage Short Mk2 750
(430) 		2.29 0.29 2 500 50 50 400
Mk2 FT.png
 Mk2 Liquid Fuel Fuselage Mk2 1 450
(810) 		4.57 0.57 2 500 50 50 800
Mk3 Liquid Fuel Fuselage Short.png
 Mk3 Liquid Fuel Fuselage Short Mk3 4 300
(2 300) 		14.29 1.79 2 700 50 50 2 500
Mk3 Liquid Fuel Fuselage.png
 Mk3 Liquid Fuel Fuselage Mk3 8 600
(4 600) 		28.57 3.57 2 700 50 50 5 000
Mk3 Liquid Fuel Fuselage Long.png
 Mk3 Liquid Fuel Fuselage Long Mk3 17 200
(9 200) 		57.14 7.14 2 700 50 50 10 000
NCS Adapter.png
 NCS Adapter Small, Tiny 320
(256) 		0.5 0.1 2 400 10 50 80
FAT455AirplaneWing.png
 FAT-455 Aeroplane Main Wing[Note 2] X 2 800
(2 320) 		3.78 0.78 1 200 15 50 600
BigSWingStrake.png
 Big-S Wing Strake[Note 2] X 1 000
(920) 		0.6 0.1 2 400 15 50 100
BigSDeltaWing.png
 Big-S Delta Wing[Note 2] X 3 000
(2 760) 		2.0 0.5 2 400 15 50 300
  1. ↑ 1.0 1.1 1.2 The Engine Nacelle, Engine Pre-cooler, and Mk1 Diverterless Supersonic Intake are a combination of air intake and liquid fuel tank. Only the tank properties are shown. They are located in the "Aerodynamic" category in the game.
  2. ↑ 2.0 2.1 2.2 The FAT-455 Aeroplane Main Wing, Big-S Wing Strake, and Big-S Delta Wing are a combination of lifting surface and liquid fuel tank. Only the tank properties are shown. They are located in the "Aerodynamic" category in the game.

Solid fuel rocket engines

→ Main article: Solid rocket booster
Advantages Disadvantages
High thrust-to-weight ratio, especially in atmosphere Cannot be throttled or switched off after ignition
Engine and fuel tank are a single unit Cannot refuel or transfer fuel stored elsewhere on the craft
Cheap Low efficiency compared to other types of engines
No thrust vectoring

The most basic type of rocket engine is the solid fuel rocket. Solid fuel is simply a self-oxidizing compound or mixture within a casing with a nozzle at the end to direct the exhaust gases produced. It offers no real control beyond choosing when to ignite it, though tweakables enable altering the thrust limit and total fuel.

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

Advantages Disadvantages
Work both in vacuum and in atmosphere Less efficient in atmosphere than jet engines, and less efficient in space than ion engines
Can be throttled to allow fine tuning of thrust Lower thrust-to-weight ratio compared to solid rocket engines
Fuel and oxidizer can be moved between tanks or vessels
Available in a wide range of shapes, sizes, and power levels
Frequently gimballed to allow flight control
Immediate throttle response

Most liquid fuel engines utilize a mixture of liquid fuel and liquid oxidizer in a 9:11 ratio — generally called “rocket fuel”. The exceptions[outdated] are the O-10 MonoPropellant Engine which uses monopropellant and the LV-N "Nerv" Atomic Rocket Motor which only consumes liquid fuel (heating it in the core of a nuclear reactor rather than combusting it with oxidizer). The IX-6315 "Dawn" Electric Propulsion System uses xenon gas and electric charge to power it. This engine has a very low thrust, but is very efficient, with an Isp of over 1000 seconds. In the real world, typical liquid fuels are liquid hydrogen and a highly-refined kerosene blend called RP-1, and typical oxidizers are liquid oxygen and nitrous oxide.

All liquid fuel rocket engines can be staged and respond to throttle controls. All engines use Bell nozzles except the Toroidal Aerospike Rocket.

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

RCS thrusters

Advantages Disadvantages
Monopropellant is automatically routed No throttle; either switched on or off
Offers rotation and translation maneuverability Low thrust and low thrust-to-weight ratio
Offers additional thrust for SAS when reaction wheels cannot provide enough torque Low fuel efficiency

RCS thrusters make up the Reaction Control System designed primarily for translation maneuvers, especially useful during docking. They cannot be throttled and are controlled with a separate set of keys from the pitch-yaw-roll keys. They use only monopropellant fuel, except for the Vernor Engine which uses rocket fuel. Monopropellant flows automatically from tanks mounted anywhere on a vessel to thrusters mounted anywhere on a vessel, so there is no need to set up fuel lines or mount thrusters directly on tanks if it is inconvenient or unsightly.

In addition to separate thruster parts, the Mk1-3 Command Pod has its own built-in RCS thrusters, with the same power and Isp profile as the RC-105 RCS Thruster Block.

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.
Available monopropellant tanks
RCS Fuel Density is 4 kg/unit Mass
(t) 		Monopropellant
(Units of fuel)
Image Part Radial size Cost
(Funds)		 Full Empty Max. Temp.
(K)		 Tolerance
(m/s)		 Tolerance
(g)
FL-R10.png
 FL-R20 RCS Fuel Tank Tiny 200
(176) 		0.10 0.02 2 000 12 50 20
FL-R25 FT.png
 FL-R120 RCS Fuel Tank Small 330
(186) 		0.56 0.08 2 000 12 50 120
FL-R1 Yellow.png
 FL-R750 RCS Fuel Tank Large 1 800
(900) 		3.4 0.4 2 000 12 50 750
Mk2 Monopropellant Tank.png
 Mk2 Monopropellant Tank Mk2 750
(270) 		1.89 0.29 2 500 50 50 400
Mk3 Monopropellant Tank.png
 Mk3 Monopropellant Tank Mk3 5 040
(2 520) 		9.8 1.4 2 700 50 50 2 100
Stratus-v roundified monopropellant tank.png
 Stratus-V Roundified Monopropellant Tank X 200
(176) 		0.10 0.02 2 000 12 50 20
Stratus-V Cylindrified.png
 Stratus-V Cylindrified Monopropellant Tank X 250
(190) 		0.23 0.03 2 000 12 50 50

Ion engines

Advantages Disadvantages
Extremely high efficiency Extremely low thrust; inefficient for orbital transfers
Cool blue glow Uncool excessive electric consumption
No engine gimbal
Xenon containers have lower mass ratio than rocket fuel tanks

An ion engine uses electric charge to ionize atoms of xenon gas and accelerate them in an electrostatic or electromagnetic field to propel them as exhaust. Remarkably little xenon gas is needed, and probes equipped with just a few tanks are considered able to operate forever, or until something inevitably goes wrong. However, ion engines are very demanding on electrical generation and storage and very slow to accelerate.

In real-life, they are often not considered true “rocket” engines. But given that they require no outside material or mass to operate, for ease and simplicity they are included with rocket engines on this wiki.

Hall effect thruster on Wikipedia

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
Available xenon tanks
Xenon density is 0.1 kg/unit Mass
(t) 		Xenon
(Xenon unit)
Image Part Radial size Cost
(Funds)		 Full Empty Max. Temp.
(K)		 Tolerance
(m/s)		 Tolerance
(g)
PB-X50R.png
 PB-X50R Xenon Container Radial mounted 2 220
(600) 		0.054 0.014 2 000 12 50 405
Pb-x150 xenon container.png
 PB-X150 Xenon Container Tiny 3 680
(800) 		0.100 0.024 2 000 6 50 720
PB-X750 Xenon Container.png
 PB-X750 Xenon Container Small 24 300
(1 500) 		0.76 0.19 2 000 6 50 5 700

See also

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