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 is a liquid fuelled rocket motor 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 solid-fueled JATO boosters, the liquid-fueled 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 fuel, 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 (5,070 kPa),[4] 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" propusion 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]

Specifications[edit]

Data from Christopher, John. The Race for Hitler's X-Planes. The Mill, Gloucestershire: History Press, 2013.

General characteristics

Components

Performance

Notes[edit]

  1. ^ Christopher, John. The Race for Hitler's X-Planes (The Mill, Gloucestershire: History Press, 2013), p.123.
  2. ^ a b c d e f g h i j k Christopher, p.124.
  3. ^ a b c d Christopher, p.125.
  4. ^ Christopher, p.125, calls it 50 atmospheres.
  5. ^ Price, P.R, Flight Lieutenant. "Gas turbine development by BMW" (PDF). Combined Intelligence Objectives Sub-Committee. Retrieved 7 June 2014. 

Sources[edit]

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