# V-2 rocket propulsion
The V-2's propulsion system was a liquid-propellant rocket engine burning liquid oxygen with diluted ethanol, fed by a steam-driven turbopump and cooled by its own fuel. At a thrust of 25 metric tons (about 55,000 lb), it was the world's first large liquid-propellant rocket engine and the first large pumped rocket engine.[1](https://airandspace.si.edu/collection-objects/rocket-engine-turbopump-and-accessories-v-2/nasm_A19771237000) The engine that flew in the Model 39 configuration of 1943 produced 55,000 lb of sea-level thrust, ran at 218–239 psi chamber pressure, delivered a specific impulse (rocket efficiency measure: thrust per unit propellant weight flow) of 203–239 seconds and burned for about 60 seconds.[2](https://www.enginehistory.org/Rockets/RPE02/RPE02-2.shtml)
| Key fact | Value |
|---|---|
| Propellants | Liquid oxygen + 75% ethyl alcohol (ethanol cut with water)[3](https://doi.org/10.5479/sil.930902.39088014776371) |
| Sea-level thrust | 55,000 lb[2](https://www.enginehistory.org/Rockets/RPE02/RPE02-2.shtml) (about 245 kN)[4](https://www.deutsches-museum.de/en/flugwerft-schleissheim/ausstellung/exponate/translate-to-english-raumfahrt/translate-to-english-raketenmotor-a-4) |
| Chamber pressure | 218–239 psi[2](https://www.enginehistory.org/Rockets/RPE02/RPE02-2.shtml) |
| Specific impulse | 203 s sea level, 239 s vacuum[5](https://www.enginehistory.org/Museums/USSRC/USSRC_V-2.shtml) |
| Propellant flow | 286 lb/s (72 kg/s LOX, 58 kg/s alcohol)[2](https://www.enginehistory.org/Rockets/RPE02/RPE02-2.shtml) • [4](https://www.deutsches-museum.de/en/flugwerft-schleissheim/ausstellung/exponate/translate-to-english-raumfahrt/translate-to-english-raketenmotor-a-4) |
| Burn time | 60 seconds[2](https://www.enginehistory.org/Rockets/RPE02/RPE02-2.shtml) |
| Turbopump power | 580 hp[6](https://www.nationalmuseum.af.mil/Visit/Museum-Exhibits/Fact-Sheets/Display/Article/195894/v-2-rocket/) |
| Production | About 6,000 engines, 1944–1945[6](https://www.nationalmuseum.af.mil/Visit/Museum-Exhibits/Fact-Sheets/Display/Article/195894/v-2-rocket/) |
## Propellant choice: liquid oxygen and diluted ethanol
The V-2 burned liquid oxygen against a fuel of 75% ethyl alcohol diluted with water. Alcohol was chosen over gasoline primarily because it needs much less of the expensive and difficult-to-handle cryogenic liquid oxygen.[7](http://www.astronautix.com/v/v-2.html) The water additive helped cool a motor that reached maximum operating temperatures of about 4,900 °F.[8](https://airandspace.si.edu/collection-objects/missile-surface-to-surface-v-2-a-4/nasm_A19600342000) The dilution traded energy density for cooling capacity and lower oxygen demand: the fuel itself doubled as the engine coolant.
The standard load included 80% hydrogen peroxide (for the turbopump's steam generator), four pounds of TNT, and 1.7 cubic feet of air at 3,200 psi.[3](https://doi.org/10.5479/sil.930902.39088014776371) The oxidizer-to-fuel mixture ratio was 1.13.[2](https://www.enginehistory.org/Rockets/RPE02/RPE02-2.shtml)
## Feed system and turbopump
The V-2 used a turbopump, moving about 9,700 kg of alcohol and liquid oxygen from tanks to engine.[9](https://collection.sciencemuseumgroup.org.uk/objects/co524981/v2-turbopump) Over the 60-second burn the pump moved approximately 4,200 kg (9,200 lb) of water-alcohol and 5,500 kg (12,200 lb) of liquid oxygen.[1](https://airandspace.si.edu/collection-objects/rocket-engine-turbopump-and-accessories-v-2/nasm_A19771237000)
The pump was powered by steam, not by the propellants themselves. The turbine ran on steam generated by catalyzing 85% hydrogen peroxide with a permanganate (calcium, potassium, or sodium, depending on the account) dissolved in water.[2](https://www.enginehistory.org/Rockets/RPE02/RPE02-2.shtml) [Compressed air](https://www.edgepedia.org/compressed-air) forced the peroxide and catalyst into a mixing chamber.[1](https://airandspace.si.edu/collection-objects/rocket-engine-turbopump-and-accessories-v-2/nasm_A19771237000) A contemporary Allied assessment reported steam at 420 °C (788 °F) and 350 psi feeding a simple single-wheel, partial-admission turbine developing about 500–600 hp at 5,000 rpm.[10](https://engineersatwar.ww2.imeche.org/wp-content/uploads/2019/08/imeche_proceedings_perring_mechanism_v2.pdf) The engine-history society's account gives a nominal operating range of 3,800–4,900 rpm with a 5,000 rpm overspeed shutdown and 580 hp output; the two sources do not fully agree on the operating speed.[2](https://www.enginehistory.org/Rockets/RPE02/RPE02-2.shtml)
The pump had to move ethanol at ambient temperature and liquid oxygen at −297 °F while sealing both fluids from each other and from high-pressure steam. Cavitation was controlled through tank pressurization and impeller and diffuser design.[2](https://www.enginehistory.org/Rockets/RPE02/RPE02-2.shtml) It delivered 128 lb of alcohol at 333 psi and 158 lb of LOX at 254 psi per second into a chamber burning at 218 psi.[5](https://www.enginehistory.org/Museums/USSRC/USSRC_V-2.shtml)
Engine start and stop were managed by specialized valves, the 25-Ton and 8-Ton valves, which staged thrust from 8 to 25 metric tons.[2](https://www.enginehistory.org/Rockets/RPE02/RPE02-2.shtml)
## Combustion chamber and the 18-burner head
[Walter Thiel](https://www.edgepedia.org/walter-thiel), the engine designer on the von Braun team, found that poor combustion was reducing efficiency. His response was to shorten the combustion chamber into a spherical form, raise chamber pressure and improve the injectors. He used 18 small-engine injector burner cups arranged in concentric circles around the head of the spherical chamber, all feeding the common thrust chamber, which stabilized combustion in the 25-ton engine.[2](https://www.enginehistory.org/Rockets/RPE02/RPE02-2.shtml) • [5](https://www.enginehistory.org/Museums/USSRC/USSRC_V-2.shtml) Alcohol reached the injection head through six pipes spread around the engine base.[5](https://www.enginehistory.org/Museums/USSRC/USSRC_V-2.shtml)
A 2025 review of injector technology describes the V-2's system as the introduction of a multi-element architecture of about eighteen injector "pots", each containing numerous elements including [swirl injectors](https://www.edgepedia.org/swirl-injector) and simple orifices. Early versions produced mainly parallel jets of fuel and oxidizer, which gave relatively limited mixing efficiency.[11](https://www.mdpi.com/2227-7080/14/5/285)
## Regenerative and film cooling
Combustion ran at roughly 2,660 °C,[4](https://www.deutsches-museum.de/en/flugwerft-schleissheim/ausstellung/exponate/translate-to-english-raumfahrt/translate-to-english-raketenmotor-a-4) hot enough to melt steel.[6](https://www.nationalmuseum.af.mil/Visit/Museum-Exhibits/Fact-Sheets/Display/Article/195894/v-2-rocket/) Survival depended on two techniques. In [regenerative cooling](https://www.edgepedia.org/regenerative-cooling), the 75% ethanol circulated through the space between the inner and outer walls of the double-walled thrust chamber, entering near the nozzle bottom via six pipes, absorbing heat as it flowed up to the injection head.[2](https://www.enginehistory.org/Rockets/RPE02/RPE02-2.shtml) • [4](https://www.deutsches-museum.de/en/flugwerft-schleissheim/ausstellung/exponate/translate-to-english-raumfahrt/translate-to-english-raketenmotor-a-4) In film cooling, four rings of small holes in the inner wall bled about 3% of the fuel into the chamber and nozzle, where it evaporated into a protective vapor boundary layer along the walls.[2](https://www.enginehistory.org/Rockets/RPE02/RPE02-2.shtml) • [5](https://www.enginehistory.org/Museums/USSRC/USSRC_V-2.shtml)
## Development problems and failure modes
The von Braun team encountered thrust chamber burn-throughs, explosions, fires, frozen valves, and unreliable electrical components during development.[2](https://www.enginehistory.org/Rockets/RPE02/RPE02-2.shtml) The burn-throughs were a direct consequence of Thiel's shortened chamber: reducing its length from 2 m to 30 cm raised exhaust velocity from 2,000 m/s to 2,100 m/s, and eventually 2,280 m/s, but the reduced cooling area increased burn-through problems. Fixes included a conical throat exit and a mixing chamber ahead of the burning chamber.[7](http://www.astronautix.com/v/v-2.html) Earlier, the 1.5-tonne development engine had run at 15 bar against a desired 50 bar; every attempt to raise chamber pressure caused burn-throughs and forced increases in pump and tank mass.[7](http://www.astronautix.com/v/v-2.html) The turbopump's thermal problem, warping from the temperature differentials between ambient ethanol, −297 °F LOX and 725 °F steam, was another recurring failure mode.[2](https://www.enginehistory.org/Rockets/RPE02/RPE02-2.shtml)
## By the numbers
The [Deutsches Museum](https://www.edgepedia.org/deutsches-museum)'s engineering record for a Mittelwerk-built A-4 engine of about 1944 lists about 245 kN thrust at 14 bar chamber pressure and 2,660 °C, a 400 kg engine weight, and a 65-second combustion duration.[4](https://www.deutsches-museum.de/en/flugwerft-schleissheim/ausstellung/exponate/translate-to-english-raumfahrt/translate-to-english-raketenmotor-a-4) The engine-history society's figures for the Model 39 give 55,000 lb thrust, 218–239 psi chamber pressure, 203–239 s specific impulse, a 60-second burn, 286 lb/s total flow, a 1.13 mixture ratio, 580 hp turbopump output, and a 2,484 lb engine weight, a thrust-to-weight ratio of 22.[2](https://www.enginehistory.org/Rockets/RPE02/RPE02-2.shtml) The chamber pressure and burn time differ slightly between the two sources; both sets of figures are given here without adjudication.
[Specific impulse](https://www.edgepedia.org/specific-impulse) was about 203 seconds at sea level and 239 seconds in vacuum, limited partly by the straight-sided divergent section of the nozzle, which later engines replaced with more efficient bell-shaped nozzles.[5](https://www.enginehistory.org/Museums/USSRC/USSRC_V-2.shtml) The short, round chamber shape itself made the engine more efficient than older longer, thinner designs.[6](https://www.nationalmuseum.af.mil/Visit/Museum-Exhibits/Fact-Sheets/Display/Article/195894/v-2-rocket/)
Germany made about 6,000 V-2s in 1944–1945.[6](https://www.nationalmuseum.af.mil/Visit/Museum-Exhibits/Fact-Sheets/Display/Article/195894/v-2-rocket/) The initial production cost of an A-4 rocket was 100,000 Reichmarks excluding warhead and guidance, later reduced to an average of 75,110 RM; production took 10,000–20,000 man-hours at [Peenemünde](https://www.edgepedia.org/peenemunde) but about 7,500 at Mittelwerk.[8](https://airandspace.si.edu/collection-objects/missile-surface-to-surface-v-2-a-4/nasm_A19600342000) The man-hour reduction reflects conditions at Mittelwerk, where rockets were built by 2,000 civilian technicians and roughly 10,000 prisoner laborers from the Dora camp; of the approximately 20,000 deaths in Mittelbau-Dora, about half are ascribed to the V-2 program.[8](https://airandspace.si.edu/collection-objects/missile-surface-to-surface-v-2-a-4/nasm_A19600342000)
## How it compares with other propulsion approaches
What was genuinely new was the combination: the first large liquid-propellant engine and the first large engine to use a turbopump, with regenerative cooling built in from the start.[1](https://airandspace.si.edu/collection-objects/rocket-engine-turbopump-and-accessories-v-2/nasm_A19771237000) • [9](https://collection.sciencemuseumgroup.org.uk/objects/co524981/v2-turbopump)
## References
1. [Turbopump and Accessories, Rocket engine, V-2 — National Air and Space Museum](https://airandspace.si.edu/collection-objects/rocket-engine-turbopump-and-accessories-v-2/nasm_A19771237000)
2. [Rocket Propulsion Evolution: 2.2 – V-2 Propulsion](https://www.enginehistory.org/Rockets/RPE02/RPE02-2.shtml)
3. [Final report, Project Hermes V-2 Missile Program](https://doi.org/10.5479/sil.930902.39088014776371)
4. [Rocket engine A 4 — Deutsches Museum](https://www.deutsches-museum.de/en/flugwerft-schleissheim/ausstellung/exponate/translate-to-english-raumfahrt/translate-to-english-raketenmotor-a-4)
5. [USSRC: V-2](https://www.enginehistory.org/Museums/USSRC/USSRC_V-2.shtml)
6. [V-2 Rocket — National Museum of the United States Air Force](https://www.nationalmuseum.af.mil/Visit/Museum-Exhibits/Fact-Sheets/Display/Article/195894/v-2-rocket/)
7. [V-2 — Encyclopedia Astronautica](http://www.astronautix.com/v/v-2.html)
8. [V-2 Missile — National Air and Space Museum](https://airandspace.si.edu/collection-objects/missile-surface-to-surface-v-2-a-4/nasm_A19600342000)
9. [V2 Turbopump — Science Museum Group Collection](https://collection.sciencemuseumgroup.org.uk/objects/co524981/v2-turbopump)
10. [The Mechanism of the German Rocket Bomb ("V2"): Informal Discussion, 12 October 1945](https://engineersatwar.ww2.imeche.org/wp-content/uploads/2019/08/imeche_proceedings_perring_mechanism_v2.pdf)
11. [A Comprehensive Review of Liquid-Injector Technologies for Space Propulsion](https://www.mdpi.com/2227-7080/14/5/285)
12. [Alcohol — Encyclopedia Astronautica](http://www.astronautix.com/a/alcohol.html)
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*Topic: Encyclopedia › Technology and the built world › Transport and spaceflight › Spaceflight › Launch systems and rocketry › Rocket propulsion › Propellants, stages, and boosters › Historical propulsion and early propellants*
*Initially written Sep 17, 2026 · Reviewed: Sep 30, 2026 · Edited: Sep 30, 2026; Oct 11, 2026; Oct 25, 2026 · Last review: Sep 30, 2026*
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License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license