BMW 109-718
| 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
Data from Christopher, John. The Race for Hitler's X-Planes. The Mill, Gloucestershire: History Press, 2013.
General characteristics
- Type: Liquid-propellant rocket
- Length:
- Diameter:
- Dry weight:
Components
- Compressor:
- Combustors: Catalyst ignited or Hypergolic combustion in a single combustion chamber
- Fuel type: J-2 Diesel fuel and red fuming nitric acid (RFNA / S-Stoff) oxidiser with injected catalyst
or R-stoff / SV-stoff fuel and oxidiser[5]
Performance
- Maximum thrust: 12.2625 kN (2,756.7 lbf)
- Specific fuel consumption: 0.561 kg/kN/s (12.125 lb/lbf/s)
- Power-to-weight ratio:
Notes
- ↑ Christopher, John. The Race for Hitler's X-Planes (The Mill, Gloucestershire: History Press, 2013), p.123.
- 1 2 3 4 5 6 7 8 9 10 11 Christopher, p.124.
- 1 2 3 4 Christopher, p.125.
- ↑ Christopher, p.125, calls it 50 atmospheres.
- ↑ Price, P.R, Flight Lieutenant. "Gas turbine development by BMW" (PDF). Combined Intelligence Objectives Sub-Committee. Retrieved 7 June 2014.
Sources
- Christopher, John. The Race for Hitler's X-Planes. The Mill, Gloucestershire: History Press, 2013.
