BMW 109-558

109-558
Type	Liquid-propellant rocket (sustainer)
National origin	Germany
Manufacturer	BMW
Major applications	Henschel Hs 117 Schmetterling missile
Number built	120
Unit cost	400-500 RM[1]

The BMW 109-558 is a liquid fuelled sustainer rocket motor developed by BMW at their Bruckmühl facility,^[2] in Germany during the Second World War.

The 109-558 (with the "109-" prefix being the Reichsluftfahrtministerium, or RLM, designation for reaction-propulsion aircraft power projects, encompassing all jet & rocket engine designs)^[3] was designed as a sustainer rocket for the Henschel Hs 117 surface-to-air missile.^[4] It was tubular, measuring 12.5 cm (4.9 in) diameter and about 46 cm (18 in) long overall.^[5] The engine had a compressed air tank to pressurise tanks for the R-Stoff fuel (50% triethylamine and 50% xylidine) and SV-Stoff oxidiser (94% nitric acid with 6% dinitrogen tetroxide).^[6] SV-Stoff was used to cool the combustion chamber.^[7]

The 109-558 was capable of propelling an Hs 117 at 900–1,000 km/h (560–620 mph; 490–540 kn), with throttle control by sliding valves in the exhaust nozzle, operated by a servomotor controlled by a Mach sensor. Production of the 109-558 took forty to sixty hours using a very high proportion of slave labour.

Applications

• Henschel Hs 117
• Henschel Hs 117H

Specifications

General characteristics

• Type: liquid-fuelled rocket engine
• Length: 2,400 mm (7 ft 10 in)
• Diameter: 1,250 mm (49 in)
• Dry weight: 160 kg (350 lb).^[8]

Components

• Compressor:
• Combustors: Hypergolic combustion in a single combustion chamber
• Fuel type: R-Stoff fuel (50% triethylamine and 50% xylidine) and SV-Stoff oxidiser (94% nitric acid with 6% dinitrogen tetroxide)

Performance

• Maximum thrust: 3.7 kN (830 lbf) for 33 sec, followed by 0.588 kN (132 lbf) for 24 sec
• Thrust-to-weight ratio: 0.023125 kN/kg (2.36 lbf/lb)

Notes

1. Christopher, p.127.
2. Christopher, John. The Race for Hitler's X-Planes (The Mill, Gloucestershire: History Press, 2013), p.127.
3. Christopher, p.124.
4. Christopher, p.127.
5. Christopher, p.127.
6. Christopher, p.127.
7. Christopher, p.127.
8. Christopher, p.127.

Sources

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