Walter HWK 109-509

The HWK 109-509 was a German liquid-fuel bipropellant rocket engine that powered the Messerschmitt Me 163 and Bachem Ba 349 aircraft. It was produced by Hellmuth Walter Kommanditgesellschaft (HWK) commencing in 1943.

Design and development
The HWK 109-509 used a two-component hypergolic fuel/oxidizer combination, controlled by a dual-flow turbopump, to regulate the rate of combustion and thereby the amount of thrust. The turbopump was driven by steam produced by a Walther steam generator which decomposed T-Stoff in the presence of a solid catalyst. The engine worked on the principle of the "hot" Walter drive, which used C-Stoff in place of Z-Stoff, the latter tending to clog the jets in the combustion chamber, causing fluctuations in power and potentially explosions.

The fuel was known as C-Stoff, a mix of 30% hydrazine hydrate + 57% methanol + 13% water with a small amount of potassium-copper-cyanide, and the oxidizer, known as T-Stoff, consisted of a hydrogen peroxide, which reacted violently on contact, as a hypergolic propellant combination. The violent combustion process resulted in the formation of water, carbon dioxide and nitrogen, and a huge amount of heat sending out a superheated stream of steam, nitrogen and air that was drawn in through the hole in the mantle of the engine, thus providing a forward thrust of approximately 17 kN (3,800 lbf).

The engine was an integral design with all components of the drive, with the exception of fuel tanks, locked in a frame.

Variants

 * A-0: Pre-production model, manufactured from May 1943. The thrust of this engine was regulated between 300 kp (2.9 kN) and 1500 kp (14.7 kN).
 * A-1: The first series production engine was used in the Messerschmitt Me 163 B from August 1944. The thrust here was adjustable between 100 kp (1 kN) and 1600 kp (15.7 kN).
 * A-2: Version for the Messerschmitt Me 163B-1a. Weighing only 100 kg complete, this engine consisted of two main assemblies, the roughly-cubical shape framed forward assembly comprising the turbine housing, the fuel pumps geared to the turbine shaft, the control box, a pressure-reducing valve and the electric starter motor, with the aft assembly made up of the combustion chamber, connected to the fore unit by a cylindrical "thrust-tube" containing pipes which carried fuel to the combustion chamber's individual injector jets.  The thrust was adjustable between 200 kp (2 kN) and a maximum of 1700 kp (16.7 kN).
 * B-1: Increased performance version of the A-1. This engine had a second, "cruising" combustion chamber, nicknamed the Marschofen, just below the main combustion chamber, with an additional thrust of 300 kp (2.9 kN). This auxiliary chamber proved necessary due to the actual T-Stoff oxidizer consumption of the main unit, at nearly 5 kg/s, exceeding estimates by 100%. Thrust from main chamber adjustable between 100 kp (1 kN) and 2000 kp (19.6 kN).
 * C-1: Dual-chamber motor like the B-series, based on the uprated version of the A-2. The main combustion chamber gave between 400 kp (3.9 3.9 kN) and 2000 kp (19.6 kN), auxiliary chamber 400 kp (3.9 kN). To be used in the Me 263 (Ju 248).
 * D-1: Variant of the C-1 for use in the improved B-series airframes of the Bachem Ba 349 Natter. Engine designed to be recovered by parachute, along with the entire rear section with empennage.

Applications

 * Arado Ar E.381
 * Bachem Ba 349
 * Focke-Wulf Volksjäger 2
 * Messerschmitt Me 163
 * Messerschmitt Me 262C, in Heimatschützer prototype evaluation designs.

Engines on display

 * National Museum of the United States Air Force
 * National Museum of Flight
 * Luftwaffenmuseum der Bundeswehr
 * Shuttleworth Collection
 * Ballarat Aviation Museum

Specifications (109-509A)
Data from: Jane's