German Explosives
8.6-cm R. Sprg L/5.5 Rocket
Motor
Propellant: Diglycol
Nozzles: 10
Throat Diameter: 5.25
Cant Angle: 17 degrees
Nozzle K: 495
Performance
Thrust: 57 degrees
Burning Time: 0.52
Impulse: 185
Velocity (max): 300 m/sec
Range: 4,500 meters
Description: The 8.6-cm R. Spgr L/5.5 rocket has a longer motor and a smaller payload than the Spgr L/4.5. The details of construction of the motor are similar to the Spgr L/4.5 in that the motor closure is not fixed permanently to the motor tube. A KLAZ 40 impact-firing nose fuze is employed.
The propellant grain consists of two concentric cylinders of a diglycol propellant, extended to different diameters than for the other grains. The length is 220 mm and the diameters are 66/41 and 32/71, with a total weight of 1,000 grams. The forward igniter is a 40 mm disk of incendiary material.
Remarks: This rocket has the same design factors as shown for the 8.6 cm RLg 1000 rocket except for the throat diameter and uses the same type launcher.
8.6-cm R. Sprg L/4.5 Rocket
Motor
Propellant: Diglycol
Nozzles: 4.6
Throat Diameter: 6.9, 5.25
Cant Angle: 12 degrees
Nozzle K: 460, 525
Performance
Thrust: 243
Burning Time: 1.22 minutes
Impulse: 116
Velocity (max): 250 m/sec
Range: 3,500 meters
General: In July 1944, a new series of 8.6-cm R. Spgr's was designed; the L/4.5 being the smallest rocket of the new series. The nozzle plate is threaded on to the motor tube and the loose motor closure design is employed. The body of the projectile has been lightened and the base fuze cavity eliminated. A KLAZ 40 impact-firing nose fuze is used in place of a self-destructive pyrotechnic time fuze that is used with the Spgr L/4.8.
Description: The ignition train for the motor consists of a percussion cap, rear igniter of granular black powder and a flash tube running up the central hole of the inner propellant grain to the forward igniter. The forward igniter consists of a 30-mm diameter disk of incendiary material, which is not black powder.
The propellant grains are two concentric cylinders, 130 mm in length, having diameters of 70/40 and 35/7 mm and weighing 680 grams. The grains and igniters are held in place by a light three-armed grid of plastic.
Remarks: This rocket has the same design factors as shown for the 8.6-cm RLg 1000 rocket except for the throat diameter and uses the same type launcher.
21-cm R-Lg. Rocket
Ballistics
Caliber: 21 cm
Bourrelet Diameter: 21.4 cm
Total Weight: 60 kg
Length: 5.1 cal.
Length (fuzed): 109 cm
Maximum Velocity: 560 m/sec
Maximum Ordivate: 5,400 meters
Spin Velocity: 11,900 rev/sec
Moment of Inertia:
Longitudinal: 0.0334 mkg/sec²
Transverse: 0.363 mkg/sec²
Stability Factor: 1.5
Launching Velocity: 19.1 m/sec
Launching Time: 0.118 seconds
Motor Performance
Nozzle K: 500 cm²/cm²
Burning Time: 3.3 seconds
Impulse: 3,040 kg sec.
Velocity 560 m/sec
Motor Volume: 12,600 cm³
Number of Nozzles: 6
Throat Diameter: 1.48 cm
Nozzle Area: 10.3 cm²
Nozzle Length: 7.5 cm
Cant Angle: 9 degrees
Expansion cone angle: 12 degrees
Description: The rocket projectile is a high-altitude, rearward-ejecting parachute-suspended flare. The rocket consists of two concentric cylinders, the inner tube containing the flare and the outer containing the rocket propellant. Six nozzles, arranged symmetrically around the base of the motor, are canted to provide the spin necessary to stabilize the projectile. The launcher used for the tests at Unterluss was a single-barreled launched designated "21-cm R Ag M 42", which had a barrel 1.12 meters in length.
Rocket Motor: The 21-cm R Lg rocket motor has a unique design, considering the usual German construction. The motor tube has a groove cut into the inner wall, one near each end of the tube. The purpose of the two grooves is to provide a seat for a ring-type retainer to secure the closure plates. The closure plates have thin obturator disks to prevent the escape of the hot propellant gases around the closures. The upper closure uses one obturator disk and the lower closure two. The second obturator disk is unnecessary at the top of the motor because of the threaded fit of the central tube containing the flare unit and the upper closure.
The assembly procedure is rather complicated due to the closure plate system. First, the nozzle plate is assembled with the grid and obturators. The assembled nozzle plate is fitted into the tube and the locking ring retainer seated in the retainer groove. An annular locking plate, which has the skirt crimped onto it, is bolted to the nozzle plate. The locking plate seats on the base of the motor tube and stresses the nozzle plate against the ring retainer. Three bolt positions, 180 degrees apart, are used to attach the nozzle plate and the locking plate.
The propellant grain consists of a single tube of R 6 m diglycol propellant 19.2 by 10.8 cm in diameter and 51 cm in length, weighing 15.2 kg. This grain is placed upon the grid in the motor tube. An igniter of 70 grams of black powder, contained in a ring-shaped plastic case; is placed ont he top of the propellant grain. The front motor closure is then secured to the motor by means of a retainer ring and locking plate.
A chamber for the electric igniter is permanently attached to the top closure and provided with a screw-on cap to enable insertion of the igniter after the motor has been loaded. After insertion of the electric igniter, the flare unit, with the wind-shield attached, is fitted into the motor and threaded into the upper motor closure. The manner in which the electric igniter makes an external contact cannot be determined from the information available.
Two construction designs are given for the nozzle assembly. Both types have insert nozzles, ie, the nozzles are individually assembled to the nozzle plate. In both cases, the nozzle plate is drilled and reamed 6 places, 60 degrees apart, at the desired cant angle of 9 degrees. The hole is then drilled out to a larger diameter for a short distance on the exit side of the plate forming a seat for the flange on the nozzle. The inside of the nozzle plate hole is made slightly conical in the first design. After the nozzle has been inserted, the entrance cone of the nozzle is swaged outward into this cone, thus securing the nozzle to the nozzle plate. The newer design shows the nozzle pressed into a cylindrical hole in the nozzle plate omitting the swaging operation. This is sufficient, since the effect of the high-pressure gases flowing out of the nozzle is to have a net forward thrust on the nozzle, thus forcing it more firmly against the shoulder of the nozzle plate.
Flare Unit: The flare unit is contained in a cylinder which is equal to the full length of the rocket. The front of the cylinder forms the nose of the rocket and carries the time-fuze and the ejecting charge. The ejecting charge consists of 35 grams of black powder. A thin conical windshield streamlines the forward end of the flare chamber into the body of the motor. The flare unit contains 7.5 kilograms of illuminant and has a burning time of 120 seconds. The flare unit fits in the forward part of the tube and the parachute in the rearward part of the tube. The parachute is contained in a split metal container which transmits the thrust of the ejecting charge to the base closure plug. The base closure plug is attached to the central cylinder by 3-mm diameter wires which are sheared by the thrust from the ejecting charge. The entire flare unit fits into the rocket and threads onto the forward closure. The rearward end of the flare unit projects through the nozzle plate and is obturated by a thin collar.
Remarks: This rocket has the same design factors as shown for the 8.6 cm RLg 1000 rocket except for the throat diameter and uses the same type launcher.
Next Time: German Mines and Grenades (Part 1)
Source: German Explosive Ordnance Vol. 1: Bombs, Rockets, Grenades, Mines, Fuzes & Igniters
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