rocket engine

A rocket engine is a type of jet engine that uses only stored rocket propellant mass for forming its high speed propulsive jet. Rocket engines are reaction engines, obtaining thrust in accordance with Newton's third law. Most rocket engines are internal combustion engines, although non-combusting forms (such as cold gas thrusters) also exist. Vehicles propelled by rocket engines are commonly called rockets. Since they need no external material to form their jet, rocket engines can perform in a vacuum and thus can be used to propel spacecraft and ballistic missiles.

Compared to other types of jet engines, rocket engines have the highest thrust, are by far the lightest, but are the least propellant efficient (have the lowest specific impulse). The ideal exhaust is hydrogen, the lightest of all gases, but chemical rockets produce a mix of heavier species, reducing the exhaust velocity. Rocket engines become more efficient at high velocities (due to greater propulsive efficiency and Oberth effect). Since they do not require an atmosphere, they are well suited for uses at very high altitude and in space.

Terminology

Here, "rocket" is used as an abbreviation for "rocket engine".

Chemical rockets are powered by exothermic chemical reactions of the propellant.

Thermal rockets use an inert propellant, heated by a power source such as electric or nuclear power.

Solid-fuel rockets (or solid-propellant rockets or motors) are chemical rockets which use propellant in a solid state.

Liquid-propellant rockets use one or more liquid propellants fed from tanks.

Hybrid rockets use a solid propellant in the combustion chamber, to which a second liquid or gas oxidiser or propellant is added to permit combustion.

Monopropellant rockets use a single propellant decomposed by a catalyst. The most common monopropellants are hydrazine and hydrogen peroxide.

Jet or rocket engine	Mass (kg)	Mass (lb)	Thrust (kN)	Thrust (lbf)	Thrust-to-weight ratio
RD-0410 nuclear rocket engine[9][10]	2,000	4,400	35.2	7,900	1.8
J58 jet engine (SR-71 Blackbird)[11][12]	2,722	6,001	150	34,000	5.2
Rolls-Royce/Snecma Olympus 593 turbojet with reheat (Concorde)[13]	3,175	7,000	169.2	38,000	5.4
Pratt & Whitney F119[14]	1,800	3,900	91	20,500	7.95
RD-0750 rocket engine, three-propellant mode[15]	4,621	10,188	1,413	318,000	31.2
RD-0146 rocket engine[16]	260	570	98	22,000	38.4
SSME rocket engine (Space Shuttle)[17]	3,177	7,004	2,278	512,000	73.1
RD-180 rocket engine[18]	5,393	11,890	4,152	933,000	78.5
RD-170 rocket engine	9,750	21,500	7,887	1,773,000	82.5
F-1 (Saturn V first stage)[19]	8,391	18,499	7,740.5	1,740,100	94.1
NK-33 rocket engine[20]	1,222	2,694	1,638	368,000	136.7
Merlin 1D rocket engine, full-thrust version [21]	467	1,030	825	185,000	180.1