Rocket Motor

OVERALL LENGTH

DIAMETER

TOTAL WEIGHT

PROPELLANT

PROPELLANT WEIGHT

WIDTH OF FINS

BURNING TIME

COMPLETE ROUNDS

1. H.E. Shell & Tail Propelling, U-5", Mk IV/N

2. Chemical Shell & Tail Propelling, U-5", Mks I-V

3. Incendiary Shell & Tail Propelling, U-5", Mk VI/N

4. Smoke Shell & Tail Propelling, U-5", Mk III/N

SHELLS

H.E. MK I

SMOKE MK I

INCENDIARY

CHEMICAL MK I

OVERALL LENGTH

DIAMETER

TOTAL WEIGHT

FUZING

FILLING

GENERAL:

These rocket are intended primarily for beach barrage from landing craft. The Incen-diary shell is employed only for ranging purposes, providing a visual indication of the at-tainment of the proper range. A change-over is the made to H.E., Smoke, or Chemical shells.

DESCRIPTION:

Shell, H.E., 29 lb., 5", Mk I: This shell consists of a thin-walled steel forging, closed at the after end by an externally threaded base plate. The base plate carries a thread-ed spigot which screws into the shell adapter of the rocket motor. Set into the explo-sive filling at the nose end of the shell is an exploder container with two perforated and one solid C.E. (tetryl) booster pellets. The shell may be alternatively filled with Amatol or an upper layer of T.N.T. and a lower layer of Amatol. If the former filling is employed, a T.N.T. surround is located around the exploder container. The shell is painted buff overall.

Shells, Smoke, Chemical, and Incendiary, 5", Mk I: These shells are of identical con-struction, differing only in the nature of the filling. The shell body consists of a metal cylinder welded to a closing plate at the nose end and to a tail plate at the rear. The closing plate is internally threaded to receive the fuze adapter, and a spigot is welded into the central operning in the base plate. This spigot is externally threaded to screw into the rocket motor and threaded internally to receive a tapered filling plug. For bet-ter ballistic qualities a sheel steel nose fairing is fitted over the nose fuze, which pro-trudes through a central opening in the fairing. The fairing is held in place by a metal circlip around the outside of the fuze body.

Tail Propelling, U-5", Mk VI/N: This motor consists of a cylindrical steel body, the forward end of which is closed by a cast iron pressure plate and transit plug. Within the after end is a cast iron venturi tube, closed by a closure plate to which is attached the automatic contact leads. A drum and four fins are attached to the after end of the mo-tor for stabilization.

Ignition of the cordite propellant is achieved by a magnesium igniter fitted at the forward end of the cordite grains. The igniter is fired by an electric squib, "Fuze, Elec-tric, No. F. 53 Mk I", whose leads pass to two sockets fitted to but insulated from the venturi closing plate. An automatic contact disc is fitted to the outher side of the clo-sure plate, two leads from which are fitted to two sockets in the closure plate. The automatic contact disc connects one of the igniter leads to "earth", in this case the motor body. The central brass disc of the automatic contact disc makes contac with an insulated spring finger on the projector.

These rocket motors must not be fired outside of the temperature range of 0-120° F. Moisture-proofing is effected by a silica gel capsule fitted into the after end of the venturi tube.

REMARKS:

(1) Propelling Tails, Mks I-V, used with the Chemical shell, are obsolescent. Mks III/N and VI/N have been modified to incorporate automatic electric contacts. Since the Mk VI/N is slightly more accurate, it must be used with the H.E. shell and the Incendiary ranging shell.

(2) Proposed new nomenclature for the rocket motors is as follows:

Old Nomenclature

Tail Propelling, Rocket, U-5", Mks I-V

Tail Propelling, Rocket, U-5", Mk III/N

Motor, Rocket, 5", No. 2 Mk I

Tail Propelling, Rocket, U-5", Mk VI/N

Motor, Rocket, 5", No. 2 Mk II