Reaction engine

LV-T30 Liquid Fuel Engine

A rocket engine is an engine that uses nothing but its onboard propellant to generate thrust. Unlike traditional air breathing engines used by atmospheric crafts rocket engines are able to function in a vacuum where no oxygen is present.

History

Rocket engines were present in KSP in all public releases of the game.

Approaches to rocket engines

Rocket engines come in two commonly used forms. The first and most ancient type is a solid fuel rocket which is as simple as igniting a solid, self-oxidizing compound or mixture within the casing of the rocket and allowing the escaping gases to be released through a nozzle at the rear. There are currently two booster rocket sizes included.

Liquid fuel engines are powered by a liquid propellant which is comprised of combustible liquid fuel and oxidizer. In the real world typical liquid fuels are often liquid hydrogen or kerosene, and typical oxidizers are liquid oxygen or nitrous-oxide. All engines use Bell nozzles except the only aerospike engine.

Solid fuel rocket engines

→ Main article: Solid rocket booster

Advantages

• Have a very high thrust to weight ratio.
• Engine and fuel tank are combined in one part, lowering part count, simplifying design and improving stability, which is especially important in the early stages of a rocket launch from the surface of a planet where large ammounts of more or less heavy parts and high-powered rockets cause stress both to the vessel itself and the player's computer.

Disadvantages

• Monolithic design, must be built in one piece.
• Cannot be throttled or switched off after ignition.
• Once spent, they are unable to use fuel from another source of the craft.

Available solid fuel rocket engines

Solid Fuel Density is 7.5 kg/unit				Mass (t)					Fuel ()	Thrust (kN)		TWR				Isp (s)		Burn (s)
												Full		Empty
Image	Part	Radial size	Cost ()	Full	Empty	Max. Temp. (K)	Tolerance (m/s)	Tolerance (g)		atm	vac	atm	vac	atm	vac	atm	vac
	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 "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 "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
	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 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
	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
	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
	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
	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

• Fuel and oxidizer can be moved between liquid fuel tanks, which means that spacecraft with liquid fuel engines and fuel tanks are easier and more resource-efficient to refuel than vessels with solid fuel engines, which required the entire engine bay to be replaced, while liquid fuel and oxidizer can quickly be moved between two docked vessels.
• Modular design: fuel and other components can be stored elsewhere in the craft.
• Throttle can be adjusted depending on thrust requirements.
• Can be switched off and re-ignited at will.
• Many nozzles can be gimballed for thrust vectoring.
• Efficiency largely dependent on design, with large variations. For early stages, high-output engines with low fuel-efficiency can be used to reach a low Kerbin orbit, while extremely efficient but low-power engines should be used for travelling between planets and moons to save fuel and extend the range of the craft.

Disadvantages

• Lower power to weight ratio compared to solid rocket engines.
• Complex design with fuel tanks and other additional components.
• More points of possible failure such as if the parts tear apart from stress.

Available liquid fuel rocket engines

								Thrust (kN)		T/W ratio		Max. Fuel Consumption (/s)	Isp (s)		TVC
Image	Part	Radial size	Cost ()	Mass (t)	Max. Temp. (K)	Tolerance (m/s)	Tolerance (g)	atm	vac	atm	vac		atm	vac	Gimbal (°)
	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 "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 "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 "Puff" MonoPropellant Fuel Engine	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 "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 "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 "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 "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 "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
	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
	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 "Nerv" Atomic Rocket Motor	Small	10 000	3.00	2 500	12	50	13.88	60.0	0.47	2.04	1.530	185	800	—
	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
	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
	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 "Twin-Boar" Liquid Fuel Engine	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
	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
	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
	CR-7 R.A.P.I.E.R. Engine	Small	6 000	2.00	2 000	20	50	162.30	180.0	8.27	9.18	12.036	275	305	3.0