2-in. U.P. Rocket Flare (Service)

Over-all length

Diameter

Total weight

Fuzing

Thermal initiator

Over-all length

Diameter

Width of fins

Total weight

Propellant

Propellant weight

Burning time at 60° F.

0.9 sec.

General: This flare is used to illuminate enemy targets at night. It is used in conjunc-tion with medium-caliber guns. A flare launcher is mounted on either side of the gun shield at a fixed angle of 30 degrees. This arrangement makes it possible to keep a tar-get illuminatied and at the same time engage it with the main armament.

Description

Rocket Flare Head, 2-in., No. 1 Mks I and II, No. 2 Mk I, and No. 3 Mk I – The flare head consists of a cylindrical tinned-plate container, with two cannelures near the base. Inserted in the container is a metal canister, which houses the illuminating candle and attached parachute assembly. A ballistic cap is fitted to the forward end of the contai-ner, to which it is secured with adhesive tape. A base socket is secured to the other end of the container by indenting the cannelures. The base socket screws into the shell ring of the rocket motor and contains the thermal ejector. This latter consists of a steel base plate, in the center of which is a metal septum of accurately machined thickness. The lower end of a length of safety fuse (primary delay) cut to burn approximately 22 se-conds, makes contact with 2½ grains of lead-dinitro-resorcinate (L.D.N.R.), which is stemmed into the septum recess. The upper end of the safety fuse extends into a maga-zine containing about 40 grains of G.12 gunpowder (primary ejection charge). Protruding from the base end of the canister is a short length of safety fuse (secondary delay) cut to burn for 3 seconds. The lower end of this secondary delay is in close proximity to the primary ejection charge, and its upper end projects into a magazine containing about 40 grains of G.12 gunpowder (secondary ejection charge).

The different flare heads vary only in the contents ejector employed as follows: Flare Head No. 1 Mk I uses Ejector, Contents, No. 4 Mk I (with 22-sec. delay); Flare Head No. 1 Mk II uses Ejector Contents, No. 4 Mk II (with 18-sec. delay); Flare Head No. 2 Mk I uses Ejector, Contents, No. 5 Mk I (with 9-sec. delay); and Flare Head No. 3 Mk I uses Ejector, Contents, No. 8 Mk I.

Tail, Propelling, U. 2-in., Mks VI and VII – The Motor Mk IV is identical to the 2-in. Motor Mk III described in Part. 3, chap. 2, H.E. Rockets, except that the obturator of the latter is perforated, while that of the former is not, but rather is rust-proofed to allow free conduction of heat to the thermal fuze in the flare head. For this reason, Motors Mk IV are marked T.I., indicating their use with thermal intiators. No other motor may be used with the flare head.

The Motor Mk VII differs from the Mk VI in that the castellations in the charge are omitted and a metal cased cylindrical igniter is employed.

Operation: When the rocket is fired, heat from the burning propellant grain is trans-mitted through the head obturator and the thin septum of the thermal ejector, igniting the L.D.N.R. and initiating the lower end of the primary delay. After a set delay, the pri-mary ejection charge is ignited, and the canister is ejected from the container in a for-ward direction. The secondary delay is initiated by the flash from the primary ejection charge, and after three seconds, initiates the secondary ejection charge, which ignites the candle and eject the parachute, cable, and candle in a forward direction from the canister. The parachute opens when ejected from the canister, and the lighted flare candle is suspended in mid-air.

The purpose of the secondary delay is to allow the velocity of the canister to be re-duced to a speed at which the flare and parachute assembly may be ejected without danger of break-up.

The flare is ejected at a range of about 5,000 yards and an altitude of about 2,000 feet. The duration of burning of the flare is about 70 sec.

Remarks: These flare, fitted with 4-in. x 1-in. fins, may be fired from a spiral launcher to obtain greater accuracy.

The complete round (flare head and motor) weighs 12.25 lb. and measures 51 inches in over-all length.