BMW 109-718

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BMW 109-718
Type Liquid-propellant rocket (assist unit)
Manufacturer BMW
Number built 20

The BMW 109-718 was a liquid-fuelled rocket engine developed by BMW at their Bruckmühl facility,[1] in Germany during the Second World War.


The 109-718 (109 prefix number for the Reichsluftfahrtministerium, or RLM, designation used for all reaction-propulsion [rocket and gas turbine] aviation engine projects)[2] was designed as an assist rocket for aircraft, for rapid takeoffs or to enable them to achieve high-speed sprints,[2] akin to what Americans called "mixed power" postwar. It was combined with a standard BMW 003 jet engine, placed atop the rear turbine casing of the jet engine to create a new variant of it, the 003R, providing a total of 1,250 kg (2,760 lb) thrust at full power apiece;[2] it was expected the units would be fitted in pairs. Unlike most RATO boosters,[i] the liquid-fuelled 718 rocket engine system comprising the second propulsive source of an 003R engine remained with the airframe at all times.[2]

The rocket motor had internal and external main chambers which were cooled by the nitric acid oxidiser, fed through a coiled spiral tube.[2] The centrifugal fuel pumps[2] (operating at 17,000rpm)[3] delivered a mix of nitric acid oxidiser and hydrocarbon fuel[2] at 735 psi (50.7 bar),[ii] a rate of 5.5 kg (12 lb) per 1,000 kg (2,200 lb) thrust per second.[2] The 718s fuel pumps were driven by a power take-off from the jet engine which ran at 3,000 rpm.[3] The complete unit weighed 80 kg (180 lb).[2]

Before war's end, a Messerschmitt Me 262C-2b Heimatschützer II (Home Defender II, one of four different planned designs of the rocket-boosted Me 262 C-series) was tested with a pair of 718s — each as a part of a pair of the BMW 003R "mixed-power" propulsion units — climbing to 9,150 m (30,020 ft) in just three minutes.[2] The 109-718 was also tested aboard an He 162E,[3] though records do not indicate the results of this test.

The Germans hoped the rocket might eventually rely on the same fuel as jet aircraft.[2]

Only twenty 109-718 engines were completed by war's end, each taking some 100 hours to complete.[3]


Data from [4]

General characteristics




  1. ^ Such as the parachute-droppable and reusable Walter HWK 109-500
  2. ^ Christopher (2013) calls it 50 atmospheres.[3]
  1. ^ Christopher (2013), p. 123.
  2. ^ a b c d e f g h i j k Christopher (2013), p. 124.
  3. ^ a b c d e Christopher (2013), p. 125.
  4. ^ Christopher (2013).
  5. ^ Price, P.R, Flight Lieutenant. "Gas turbine development by BMW" (PDF). Combined Intelligence Objectives Sub-Committee. Retrieved 7 June 2014.


  • Christopher, John (2013). The Race for Hitler's X-Planes. The Mill, Gloucestershire: History Press.