German Explosives
SB 400 Kugel K - "Kurt" Apparatus
The information contained in this report was obtained through the interrogation of German scientists and prisoners of war. Complete specimens of this device have been shipped to the United States Nay Ordnance Investigation Laboratory.
Development of the "KURT" apparatus was commenced in the late 1943 at the German airforce experimental center (E-Stelle), Travenmunde, Germany. The original model was a sphere approximately 30 inches in diameter and weighing 400-450kg. It contained two fuzes; one, a type 59 fuze with a 23-second powder delay train, and the other, a hydrostatic, type 44 fuze. The effective range of this spherical missile was calculated at 400 meters. To increase the range to 4,000 meters a rocket propulsion unit was fitted to the sphere. Some experiments were carried out with the propulsion unit but no actual tests were made. Work was stopped on this device in August 1944 when efforts were directed to more advanced projects. Because of the scarcity of documents and test datum it is impossible to substantiate adequately the information obtained through interrogation.
The first experiments were carried out with a model having the same weight and dimensions as the final "KURT" warhead. The ideal altitude for the attacking plane was calculated at 20 meters and at a speed of 700km/h. It was found that under ideal conditions, the missile had an effective range of 400 meters. To increase the range and to offer more protection for the attacking aircraft, a rocket propulsion unit was added. The modified "KURT" with rocket assistance included an air tail with its elevators preset to an angle of 10 degrees to prevent sharp trajectory as in the case of the sphere without rocket assistance. (Because of the essentially shorter running distance of the sphere without rocket assistance, sharp trajectories and slight deviations from the target course were disregarded.) This modification proved unstable in flight because the assembly tended to rotate about its longitudinal axis, deviating from the target course to such an extent that the target would be missed completely. To obviate this large deviation and to give the missile directional stability, a gyroscope was installed. However, no further tests were made.
Details:
A. Warhead
-Diameter: 750mm
-Thickness of case: 10-12mm (Steel)
-Weight of charge: 300kg
-Total weight of sphere: 400-450kg
The warhead, a spherical shell, is filled with cast hexanite and contains two fuze pockets. A transverse pocket, housing two KRUPP hydrostatic fuzes which replaced the type 59 fuze, runs through the sphere and is open at both ends. The other pocket is set at an angle of 45 degrees to the transverse pocket and contains a type 44 hydrostatic fuze.
B. Mid-Section
The cylindrical mid-section houses a gyro unit which is operated by a gas evolved from a burning element. It also houses the lifting lug and the explosive coupling which severs the warhead from the propulsion unit.
C. Rocket Section
The rocket section is a steel cylinder 18 inches in diameter and 36 inches long. It houses the rocket propellant and 18 venturis. The weight of the propellant is approximately 90 kg.
D. Air Tail
The air tail is the same as used with the bomb-torpedo. It is made of plywood and its elevators are controlled by the gyro. Dimensions of the air tail: 18 by 36 by 50 inches. Total length of the KURT apparatus is 80 inches.
Operation:
A. Without Rocket Propulsion
-Plane speed: 700km/h
-Plane altitude: 20m minimum - 50m maximum
-Speed of Kugel on impact: 180 meters/second
-Effective distance: 400 meters
B. With Rocket Propulsion
-Plane speed: 700km/h
-Plane altitude: 20m minimum - 50m maximum
-Speed of Kugel with rocket assistance: 330 meters/second
-Speed of Kugel on impact: 180 meters/second
-Distance through air before impact: 1,000 - 1,500 meters
-Effective distance: 2,500 - 4,000 meters
C. The range depends on:
1. Height of plane
2. Speed of plane
3. Surface of water
Under ideal conditions the Germans considered the Kugel without propulsion 100 percent accurate at a range of 400 meters when dropped from an altitude of 20 meters at 700km/h. If the missile was dropped from heights greater than 50 meters or at speeds less than 700km/h the effective range was decreased due to deviations from the target course. Rough waters also caused serious deflections which could not be controlled.
D. Fuzes
In the original Kugel without propulsion, two hydrostatic fuzes were used; a type 59 fuze that was designed to operate after a delay of 23 seconds, and a type 44 fuze designed to operate at a depth of 8 meters. The sphere was later modified to accommodate two Krupp fuzes for normal hydrostatic operation at 8 meters, and an electrical time delay fuze in case the missile penetrate the ship's hull.
E. Condenser Fuze
A condenser fuze, E1AZ 49, functions in the following manner:
1. Ignites an explosive element which starts the gyro immediately upon release of the missile from the plane.
2. Ignites the rocket propellant by exploding a 1-kg black powder charge after a delay of 0.5 seconds.
3. Allows either one of two possible types of electric fuzes used, to be armed.
4. Fires the explosive coupling after a delay of 4.5 seconds.
When the rocket propellant is ignited it burns from 3 to 4 seconds. One-half second after the rocket impulse ceases, the explosive coupling fires, severing the sphere from the after body. The rocket section drops off and the sphere continues toward the target. The missile then hits the target and sinks. When at a depth of 8 meters, one of the hydrostatic fuzes is actuated to fire the main charge.
SB 1000
Body Diameter: 26 inches
Tail Width: 26 inches
Tail Length: 26 inches
Filling: RDX/A1/Wax biscuits in Trialen 106 matrix
Weight of filling: 735 kilograms
Total weight: 1,000 kilograms (approx.)
Charge/Weight ratio: 0.74% (approx.)
Construction: The bomb has a welded sheet metal body. A drawn steel threaded nose piece is of streamlined construction to reduce air resistance while the bomb is attached to the plane. (Earlier models had a welded nose piece.) There is no base plate. The bomb is filled through the nose and an exploder tube runs along the central axis from the fuze pocket to the nose. It is filled with TNT pellets.
Electric leads run through the center of the bomb connecting fuze and nose switch.
Bomb has a drawn steel cone-type tail.
Suspension: Horizontal by H-type lugs or trunnions for use if carried by dive bombers.
Remarks: Due to its thin case and brisant explosive, this bomb is sensitive to small arms fire.
SB 1000 Parachute Bomb
Body Length: 65 and 1/2 inches
Elliptical Body: 31 by 16 and 1/2 inches
Wall Thickness: 0.06 to 0.125 inches
Filling:
Main charge: Dinitro benzine (48%); RDX (15%); ammonium nitrate (37%)
Biscuit filling: ammonium nitrate (51%); calcium nitrate (31%); RDX (16%)
Charge/Weight ratio: 80%
Color: The bomb casing is painted field gray with the following markings stenciled in black along the body.
Construction: The parallel sided body of the SB 1000 is made of steel plate and is roughly elliptical in end section. It is formed by two halves which are welded together externally. The bomb body is strengthened by a longtudinal bulkhead and two perforated diaphragms all welded into position. The base plate is welded into the body 2 and 1/2 inches from the end. The recess so formed is used to house the parachute container.
The fuze pocket is welded into a slot in the longitudinal bulkhead. Nose plate is welded into position and has in it filling holes. There is a nose extension in the center of the nose plate which houses the impact switch 55 A/M fuze. The fuze pocket is connected to the impact switch by two wires which are house in a metal tube. The parachute container, a thin metal box, is positioned between two ribs riveted to the base plate. It is secured to the base of the bomb by bolts. Inside the outer box an inner container is welded to the base of the outer box. Four extension springs are secured to the base of the inner container and are also attached to a plywood platform which is the base for the parachute. The parachute is folded on the plywood, the platform depressed, compressing the spring then held in place by canvas flaps secured over the top. The under flap carries a loop of cord which is threaded through eyelets of the other three flaps, a quick release pin is passed through the loop, thus retaining assembly against action of the spring.
Operation: On release from the aircraft the quick release pin is withdrawn from the loop by a time parachute release which can be set for delays of 2, 3, 4, 5, or 6 seconds. This device obtains its delay by means of a spring and cog wheel.
The parachute is of coarse weave vegetable matter. Red, green, and blue parachutes have been found. There are 16 double parachute shroud lines.
Suspension: Horizontal.
SB 1000/410 - 52A+, 52A
No picture available
It has been assumed that the figure "410" refers to the type of aircraft by which the bomb is carred. ME 410.
SB 2500-kg
Body Length: 87 and 3/4 inches
Body Diameter: 31 inches
Wall Thickness: 17/32 inches
Tail Width: 33 inches
Tail Length: 66 and 1/2 inches
Filling: 40/60 Amatol or Trialen 105
Total Weight: 2400 kilograms
Color: Sky blue overall. Two yellow stripes are painted on the body between the tail fins. SB 2500 is stenciled on the body.
Construction: The main difference between this and the SC 2,500-kg type Max are: the construction is of steel instead of aluminum alloy and the filling extends into the tail cone with the object of keeping the charge/weight ratio as high as possible. The case is constructed in three parts, a cast steel nose, with a cast steel base welded to the cylindrical body. The nose of the bomb is fitted with a filling plug to which is fitted a tube extending to the forward fuze pocket, the tube houses a rod which on impact crushes the impact fuze and activates the bombs. There are two transverse fuze pockets; the forward pocket houses the anti-break-up fuze and the after pocket is for the normal impact type fuze.
The tail unit is a four fin drum type. The cone portion is sheet steel and the fins and tail drum are constructed of alloy.
Suspension: Horizontal by an H-type lug. The suspension lug is keyed to a securing plate locked by bolts.
Next Time: SD Bombs
Source: German Explosive Ordnance Vol. 1: Bombs, Rockets, Grenades, Mines, Fuzes & Igniters
Source: German Explosive Ordnance Vol. 1: Bombs, Rockets, Grenades, Mines, Fuzes & Igniters
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