Cutaway model of a WW2 British 3 60Lb RP S.A.P. (Rocket Projectile Semi Armour Piercing), in short RP-3.
The name 3 is derived from the diameter of the motor (76 mm). As it is unguided, aiming was a matter of judgment and experience. The rocket suffered badly from trajectory drop, making aiming difficult unless in a steep dive. Against slow moving large targets like shipping the rocket was a formidable weapon, and it was on anti-shipping operations that the RP-3 was first used in 1942.
The RP-3 were fitted to British fighter bomber aircraft such as the hawker Typhoon, the Bristol Beaufighter and the DeHaviland Mosquito FB MkXVIII. A typical installation was 4 projectiles on launching rails under each wing. They would be fired in pairs, one left, one right toward the target on the ground. A full eight rocket salvo of 60Lb SAP rockets can be compared to the broadside salvo of a cruiser.
The 3 Mk.2 motor:
The motor exists of a thin walled 3 steel pipe with a venturi welded into the base of the pipe.
It top an internally threaded bushing is fixated into the pipe by means of two rings of removable rivets. These rivets are held in position by two ring shaped springs whom press the rivets outward.
The motor is filled with an 11 pounds (5,2 kg) stick of cordite. This stick when cut across- has the shape of a cross. The motor is electrically ignited by the igniter charge No.53, placed in the top of the motor in a recess in the powder stick. A moisture tight steel saeling cap is placed in the venturi. Through this cap the electric wire runs from the igniter charge to the electric connection plug.
A bag of silica gel is placed in the venturi to remove any moisture. A cross formed grid is placed between the powder stick and the venturi, preventing large pieces of cordite of blocking the venturi. This grid is connected to the powder stick by means of two nails.
The motor has 4 square sheet metal clip-on tailfins to stabilize the rocket in flight.
The 60 Lb SAP projectile:
The 60Lb (27,9 kg) Semi Armour Piercing warhead is made of two parts, a pointed hardened nose which is screwed on a mild steel body. The projectile is filled with 5,6 kg (cast) TNT or Amatol 60/40. The projectile is fuzed with the Fuze 878. Above the fuze a cartboard C.E. pellet is placed as a booster.
A hollow bushing, threaded on the outside, connects the motor with the projectile and also houses a screwed in cap in the base containing a black powder thermal initiator which armes the fuze only after ignition of the motor. In the base of this cap an appr. 9 mm dia. piece is appr. 0,5 mm thick, enabeling it to ignite the thermal initiator through heat transfer of the motor.
Fuze No.878:
The fuze is all brass made, exept for the firing pin, the safety ball and the safety rod. On igniting the motor, the thermal initiators black powder charge explodes, filling the hollow part of the connection bushing with high pressure gas. The gas enters the base of the fuze (blue holes) and will press the membrame in the base of the fuze -and the connected safety rod- forward. In afterward membrame position (safe , like in picture) the rod prevents the ball -that blocks the firing pin from moving forward- from moving outward, it also keeps the (rotation) shutter -housing the detonator- out of line with the firing cap. The safety rod has two 1mm deep recesses which enables the lock up ball to move outward -releasing the firing pin and the shutter to rotate in line with the firing cap when the safety rod moves forward. On impact the firing pin is swung forward, riding the creep spring into the firing cap (red). On ignition of the firing cap the gasses are pressed forward into a small gas collection chamber above the firing cap, after which the gas is pressed into another chamber on top of the first, and than into the detonator (the Fuze No.865 is completely identical to the No.878, exept for the upper chamber which contains a black powder delay pellet in the No.865 ). this ignites the detonator in the shutter which -on its turn- ignites the gaine.
Weight of the complete rocket: 44,2 kg
Weight of motor: 16,3 kg
Weight of projectile: 27,9 kg
Diameter of motor: 83 mm
Diameter of 60Lb. S.A.P projectile: 152 mm
Length of the complete rocket: 1876 mm
Wing span: 340 mm
Burning time of motor : 1,5 seconds at 15,6 degr. celcius
Fuzes used: No.878 or No.865
Vo: 480 mtrs/sec
Range: appr 1600 mtrs (1 mile)
Some nice movies, showing the 3 60Lb SAP rocket in action can be found here:
http://www.youtube.com/watch?v=Iffn...mid=26&func=view&catid=11&id=3108
[ame="http://www.youtube.com/watch?v=IZ-a8U1QWUw"]YouTube- || de Havilland Mosquito - DH.98 / RAF / WWII / GunCam ||[/ame]
Regards , DJH
The name 3 is derived from the diameter of the motor (76 mm). As it is unguided, aiming was a matter of judgment and experience. The rocket suffered badly from trajectory drop, making aiming difficult unless in a steep dive. Against slow moving large targets like shipping the rocket was a formidable weapon, and it was on anti-shipping operations that the RP-3 was first used in 1942.
The RP-3 were fitted to British fighter bomber aircraft such as the hawker Typhoon, the Bristol Beaufighter and the DeHaviland Mosquito FB MkXVIII. A typical installation was 4 projectiles on launching rails under each wing. They would be fired in pairs, one left, one right toward the target on the ground. A full eight rocket salvo of 60Lb SAP rockets can be compared to the broadside salvo of a cruiser.
The 3 Mk.2 motor:
The motor exists of a thin walled 3 steel pipe with a venturi welded into the base of the pipe.
It top an internally threaded bushing is fixated into the pipe by means of two rings of removable rivets. These rivets are held in position by two ring shaped springs whom press the rivets outward.
The motor is filled with an 11 pounds (5,2 kg) stick of cordite. This stick when cut across- has the shape of a cross. The motor is electrically ignited by the igniter charge No.53, placed in the top of the motor in a recess in the powder stick. A moisture tight steel saeling cap is placed in the venturi. Through this cap the electric wire runs from the igniter charge to the electric connection plug.
A bag of silica gel is placed in the venturi to remove any moisture. A cross formed grid is placed between the powder stick and the venturi, preventing large pieces of cordite of blocking the venturi. This grid is connected to the powder stick by means of two nails.
The motor has 4 square sheet metal clip-on tailfins to stabilize the rocket in flight.
The 60 Lb SAP projectile:
The 60Lb (27,9 kg) Semi Armour Piercing warhead is made of two parts, a pointed hardened nose which is screwed on a mild steel body. The projectile is filled with 5,6 kg (cast) TNT or Amatol 60/40. The projectile is fuzed with the Fuze 878. Above the fuze a cartboard C.E. pellet is placed as a booster.
A hollow bushing, threaded on the outside, connects the motor with the projectile and also houses a screwed in cap in the base containing a black powder thermal initiator which armes the fuze only after ignition of the motor. In the base of this cap an appr. 9 mm dia. piece is appr. 0,5 mm thick, enabeling it to ignite the thermal initiator through heat transfer of the motor.
Fuze No.878:
The fuze is all brass made, exept for the firing pin, the safety ball and the safety rod. On igniting the motor, the thermal initiators black powder charge explodes, filling the hollow part of the connection bushing with high pressure gas. The gas enters the base of the fuze (blue holes) and will press the membrame in the base of the fuze -and the connected safety rod- forward. In afterward membrame position (safe , like in picture) the rod prevents the ball -that blocks the firing pin from moving forward- from moving outward, it also keeps the (rotation) shutter -housing the detonator- out of line with the firing cap. The safety rod has two 1mm deep recesses which enables the lock up ball to move outward -releasing the firing pin and the shutter to rotate in line with the firing cap when the safety rod moves forward. On impact the firing pin is swung forward, riding the creep spring into the firing cap (red). On ignition of the firing cap the gasses are pressed forward into a small gas collection chamber above the firing cap, after which the gas is pressed into another chamber on top of the first, and than into the detonator (the Fuze No.865 is completely identical to the No.878, exept for the upper chamber which contains a black powder delay pellet in the No.865 ). this ignites the detonator in the shutter which -on its turn- ignites the gaine.
Weight of the complete rocket: 44,2 kg
Weight of motor: 16,3 kg
Weight of projectile: 27,9 kg
Diameter of motor: 83 mm
Diameter of 60Lb. S.A.P projectile: 152 mm
Length of the complete rocket: 1876 mm
Wing span: 340 mm
Burning time of motor : 1,5 seconds at 15,6 degr. celcius
Fuzes used: No.878 or No.865
Vo: 480 mtrs/sec
Range: appr 1600 mtrs (1 mile)
Some nice movies, showing the 3 60Lb SAP rocket in action can be found here:
http://www.youtube.com/watch?v=Iffn...mid=26&func=view&catid=11&id=3108
[ame="http://www.youtube.com/watch?v=IZ-a8U1QWUw"]YouTube- || de Havilland Mosquito - DH.98 / RAF / WWII / GunCam ||[/ame]
Regards , DJH
