This is an self-propelled, circumferential venting H.E. rocket filled T.N.T. The shell is in rear of the propelling unit. It is fired electrically and projected from either the 15 cm Pan-zerwerfer 42 or the 15 cm Nebelwerfer 41 projector.

The general shape of the rocket and its external markings are shown in Fig. 18. The complete round weighs approximately 76 lb. 10 oz., and its overall length is 36.4 inches. It is painted either a deep olive green or light grey green and stencilled in white on the propelling unit and in black on the shell.

Shell filled T.N.T.;

Base fuze Bd.Z. DOV;

Gaine gr.Zdlg. C/98 Np;

Motor unit;

Electric ignition fuze.

The body is of malleable iron, cylindrical in shape with a radiused base. The overall length, including the obturator, is 10.4 inches, and the external diameter 4.97 inches. The wall of the body is approximately 0.4 inch thick. The base is bored centrally and screwthreaded to receive a fuze adapter to which the steel gaine container is attached by indenting the mouth of the latter to an internal cannelure in the former. The forward end of the body is screwthreaded internally to receive the base of the venturi block which screws on to the flange of an inverted cup-shaped cast iron obturator, accommo-dated in a recess in the base of the venturi block.

The bursting charge, weighing approximately 5 lb. 10 oz., consists of two pressed pellets of T.N.T. completely enclosed in a shaped cardboard carton with a cavity to accommo-date the gaine at the rear end and reduced in diameter at the forward end to fit into the obturator. The carton is cemented to the body by a magnesium oxychloride composition.

A description of this gaine is given in Pamphlet No. 4, page 33, and illustrated in Fig. 22.

The motor unit with venturi block weighs approximately 50 lb. 11 oz., and has an overall length of 18.9 inches. It consists mainly of a tube, ballistic cap, venturi block, propellant charge, grid, spacing ring and ignition system.

The tube is cylindrical with a closed end and appears to be a solid forging, machined in-side and out to a diameter of 5.05 inches and 5.5 inches respectively, and to an internal depth of 18 inches. It weighs 24 lb. 13 oz. The closed end is bored centrally and screw-threaded for the attachment of the ballistic cap. The open end is chamfered internally and screwthreaded externally to receive the venturi block.

The ballistic cap is of thin pressed steel and provided with a perforated internal dia-phragm with a central screw to enable the cap to be secured to the tube.

The venturi block, which unites the motor unit and shell, weighs 10 lb. 14 oz. The top is cup-shaped and screwthreaded internally to a depth of 1.75 inches to receive the tube; externally it is chamfered from the skirt towards the top. The base is provided with a screwed boss for the attachment of the shell unit and is recessed to accommodate the shell obtruator. Twenty-six venturis, equally spaced to form an annular ring, are bored in the skirt near the periphery. Each venturi has a throat diameter of 0.22 inch and is inc-lined at 14 degrees to rotate and stabilize the rocket in flight. The venturi are sealed by a thin aluminium disc inserted on the inside.

The propellant, as indicated by the stencilling "Digl" on the tube, is of the double-base type consisting of nitrocellulose 61.1 per cent, diethylene-glycoldinitrate 33.3 per cent, stabilizer (probably akardite) 2.1 per cent, graphite 0.24 per cent, ash (carbonated) 0.75 per cent, and undetermined matter 2.51 per cent. The charge weighs 13 lb. 1 oz. and is in the form of six tubular sticks surrounding a seventh. Each stick is 16 inches long, 1.65 inches and 0.25 inches external and internal diameters respectively. The charge is held between a grid at the base and a spacing ring at the head.

The grid, which weighs 1 lb. 3 oz., is a cast iron ring, 4.4 inch external circumference on a web of six spokes radiating from a central ring. It is centred by the chamfered interior of the tube, which suits the chamfered end of the spokes. Longitudinal movement of the grid is prevented by means of a felt disc which is compressed when the venturi is scre-wed to the tube.

The spacing ring at the head is a split ring with ten pairs of lugs bent inwards to form a "U" shape in section.

The ignition system comprises a rear and forward igniter and a length of primed celluloid tubing.

The rear igniter consists of an annular transparent plastic ring containing approximately 1 oz. 7 dr. of black powder, and a silk flat bag containing approximately 3 dr. of gun-powder. The ring is housed immediately inside the venturis. Stuck to the inside of the ring is an opaque plastic flange with a felt disc cemented to it. The felt bag is sewn to the centre of the felt disc.

The forward igniter consists of 3 oz. of gunpowder in a circular cardboard box which is housed in a metal cup with a wide flange. The flange is held against the head of the tube by the spacing ring so that the igniter is held centrally within the ring and facing the central stick of propellant. The igniter ensures complete ignition of the propellant.

The celluloid tubing is housed in the central stick of propellant. It contains quick-match and is closed at each end by a small gunpowder pellet.

The electric ignition fuze is described as a separate item in this pamphelt. It is inserted in one of the venturis.

An electrical current generated from a remote control fires the electric fuze, thereby producing a flash which in turn ignites the rear igniter, the primed celluloid tubing, the forward igniter and the propellant charge. Pressure set up by the gases and escaping through the venturis propels the rocket forward. The venturis being inclined cause the rocket to rotate and so stabilizied it in flight.

Fig. 18