 The "A" stood for Nitric Acid ("Azotnokislotny" in Russian), versus K for Liquid Oxygen ("Kisloroda" in Russian), a distinction of unusual importance and controversy among Soviet rocket scientists.Dushkin's turbine propellant pump was causing considerable problems, driven by hot gas and steam from a small combustion chamber fed with rocket propellants mixed with water, but this system was perfected a few years later for the RD-2M engine.The D-1-A-1100 was built from S54 steel (a 12% chromium alloy).