Walter HWK 109-507

It had originally been developed as an unpowered glide bomb, "Gustav Schwartz Propellerwerke", and the engine was added later.

[3] As it was intended for attacking lightly- or unarmoured targets, it did not require an armour-piercing high impact speed.

Rather than the complex centrifugal turbopumps used for most Walter engines, a simple gas pressurisation system was used to feed the propellants.

A wartime British report expressed surprise that the engine's combustion chamber was made of mere mild steel, rather than anything more refractory.

This was a 'cold cycle' engine; the peroxide acted as a monopropellant and was decomposed by a catalyst into superheated steam and oxygen.

Propellants are forced into the combustion chamber by compressed air, stored at 200 bar (2,900 psi) in two steel vessels.

A non-return valve ensures that no catalyst can flow backwards into the air or propellant plumbing, with an explosive result.

A rubber diaphragm, broken as propellant pressure builds, ensures that there is no backflow through the combustion chamber either.