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, in Germany during the Second World War.

Development

The 109-718 (109 prefix number for the Reichsluftfahrtministerium, or RLM, designation used for all reaction-propulsion [rocket and gas turbine] aviation engine projects) was designed as an assist rocket for aircraft, for rapid takeoffs or to enable them to achieve high-speed sprints, 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; it was expected the units would be fitted in pairs. Unlike most RATO boosters,[lower-roman 1] the liquid-fuelled 718 rocket engine system comprising the second propulsive source of an 003R engine remained with the airframe at all times.[1]

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

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. The 109-718 was also tested aboard an He 162E, although records do not indicate the results of this test.[3]

The Germans hoped the rocket might eventually rely on the same fuel as jet aircraft.[1]

Only twenty 109-718 engines were completed by war's end, each taking some 100 hours to complete.[2]

Specifications

Data from The Race for Hitler's X-Planes: Britain's 1945 Mission to Capture Secret Luftwaffe Technology[4]

General characteristics

Components

Performance

  • Maximum thrust: 12.2625 kN (2,756.7 lbf)
  • Specific fuel consumption: 0.561 kg/kN/s (12.125 lb/lbf/s), which translates to an ISP of 181.75 (s), probably at sea level

Notes

  1. ↑ Such as the parachute-droppable and reusable Walter HWK 109-500
  2. ↑ Christopher (2013) calls it 50 atmospheres.[2]

Citations

  1. 1 2 Christopher (2013), p. 124.
  2. 1 2 Christopher (2013), p. 125.
  3. 1 2 Christopher (2013), pp. 124–125.
  4. ↑ Christopher (2013), pp. 123–125.
  5. ↑ Price, P.R, Flight Lieutenant. "Gas turbine development by BMW" (PDF). Combined Intelligence Objectives Sub-Committee. Retrieved 7 June 2014.{{cite web}}: CS1 maint: multiple names: authors list (link)

Bibliography

  • Christopher, John (2013). The Race for Hitler's X-Planes: Britain's 1945 Mission to Capture Secret Luftwaffe Technology. Stroud, UK: History Press. ISBN 978-0-7524-6457-2.
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