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.
[1] The rocket motor had internal and external main chambers which were cooled by the nitric acid oxidiser, fed through a coiled spiral tube.
[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.
[2] Data from The Race for Hitler's X-Planes: Britain's 1945 Mission to Capture Secret Luftwaffe Technology[4]