C-Stoff propellant is pumped to the combustion chamber jacket, cooling the chamber to provide efficient combustion, and provide a degree of mechanical longevity of one of the most stressed portions of the motor.

Following cooling, C-Stoff is returned to the main propellant control valve. However, before the propellant is fed into the system proper, the C-Stoff is passed through a filter to remove any dirt or debris particles.

The largely cylindrical aluminium filter housing is attached by bolts to the end of the motor propellant control valve. At the top, a cover plate, bolted to the filter cylinder body, allows easy access to the filter element.

The filter element consists of two cylindrical castings, one fitted inside the other, both covered in a fine, 0.0075 inch mesh steel gauze. Fuel passes into the annular space between the casing and the filter element, passing first through the outer, then the inner elements before flowing to the center of the filter, and then on to the barrel of the C-Stoff propellant control valve.

In later production models, the inner filter was dispensed with, as it was felt that it was largely superfluous, and was causing an unnecessary pressure drop in the C-Stoff delivery.

The Air Ejectors - "Ejektoren".

One of the principal problems with the 109-509.A-1 series motors, was stalling of the motor thrust in flight, when air in the propellant lines caused pressure drops in the pumping system, shutting down the motor.

Flight manouvering, despite a complex system of baffles in the propellant tanks, drew air into the propellant lines, and caused a failure in priming the centrifugal pumps. Developed for the 109-509.A-2 series motor, was an air bleed system, called the air ejector.

The body of the valve is aluminium, in one section of which is a steel piston, with ports cut in its side, halfway along its length. These ports correspond with outlet ports in the cylinder and are connected to the inlet of a venturi tube.

A pipe connected to the top of the cylinder leads to the propellant pump, so when the ports coincide, there is a direct connection between the pump and the venturi. Steam enters the ejector and is directed through the venturi, causing a pressure drop, drawing the air from the propellant line.

The piston is loaded fully open by means of a spring, but when all the air is removed from the line, propellant under pressure emerges. This pressure is transmitted to the top of the ejector piston, pushing it down, closing the outlet ports to the venturi.

At the same time, the piston acts on a push rod, forcing a poppet valve onto its seating, shutting off the inlet of more steam.

When there is air in the propellant line, the hydraulic pressure of the propellant is removed and so the springs open the piston, the flow of steam begins again, and the air is drawn out until propellant pressure returns to shut off the cycle.

Web Master Shamus Reddin