Some info on the SB-400 , the smaller brother.
THE GERMAN SB 400 KUGEL K-"KURT" APPARATUS '
DESCRIPTION. The German "KURT" apparatus is a spherical, hydrostatically operated,
aircraft-laid, skip bomb ; a copy of a similar device used by the British.
It was designed to operate like -u skipping stone over a smooth water surface
for use against ship targets, power plants, lock gates, tidal installations and similar harbor
facilities.
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 Navy Ordnance Investigation Laboratory.
Development of the "KURT" apparatus was commenced in the late 1943 at the German airforce `
experimental center (lGStelle), Travemunde, Germany.
The original model was a sphere approximately 30 inches in diameter and weighing
400-450 kg.
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 bat 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 700 km/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' 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 dis
regarded.)
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
EXPLOSIVE COUPLING HYDROSTATIC FUZE
gyroscope was installed. However, no further tests were made.
DETAILS
A. WARHEAD
Diameter : 750 mm.
Thickness of case : 10--12 mm. (steel) .
Weight of charge : 300 kg.
Total weight of sphere : 400-450 kg.
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° to the transverse
pocket and contains a type 44 hydrostatic fuze.
B. MID-SEa-riox . 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 SECTIOY. The rocket section is a steel cylinder 18 inches in diameter an&86 inches
long. It houses the rocket propellant and 18 venturis.
The weight of the propellant is approximately
90 kg.
VENTURI TUBES
ROCKET SECTION
I AIR TAIL
PROPELLENT IGNITER
MID-SECTION
1 5
SUSPENSION BAND
SUSPENSION LUGS
D. AIR Tall. 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 38 by 50 inches.
Total length of the KURT apparatus is 80 inches.
OPERATION
A. WITHOUT ROCKET PROPULSION :
Plane speed ; 700 km/h.
Plane altitude : 20 mminimum-50 m max.
Speed of Kugel on impact : 1$0 meters/sec.
Effective distance : 400 meters.
WITH ROCKET PROPULSION :
Plane speed . 700 km/h .
Plane altitude : 20 in minimum-50 m max.
Speed of Kugel with rocket assistitnce : 330 m/second.
Speed of Kugel on impact : :320 m/second .
Distance through air before impact : 1,000- 1,500 meters.
Effective distance : 2.,500--4,000 meters .
C. THE RANGE DEPENDS ON :
1 . Height of plane.
2. Speed of plane.
3. Surface of water,
Under ideal conditions the Germans considered the Kugel without propulsion 100 percent accurate
at. a range of 400 meters when dropped from an altitude of 20 meters at 700 km/h. If the missile
was dropped from heights greater than 50 meters or at speeds less than 700 km/h the effective range
was decreased due to deviations from the target course.
Rough waters also caused serious deflections which could not be controlled .
D. Fuzes.
In the original Kugel without propulsion, two hydrostatic fuzes were used ;
a type 59 fuze that was designed to operate afters delay
of 23 seconds, and a type 44 fuze designed to operate at a depth of 8 dieters. The sphere was later
modified to accommodate two Krupp fuzes for normal hydrostatic operation at 8 meters, and an
electrical time delay fuze in case the missile penetrated the ship's hull .
E. CONDENSER FUZE.
A condenser fuze, EIAZ
49, functions in the following manner :
1 . Ignites an explosive element which starts the gyro immediately upon release of the missile from
the plane.
2 . Ignites the rocket propellant by exploding a 1-kg black powder charge after a delay of 0.5
second.
3. Allows either one of two possible types of electric fuzes used, to be armed (electric hydrostatic
or electric time delay) .
4. Fires the explosive coupling after a delay of 4.5 seconds.
When the rocket propellant is ignited it burns from 3 to 4 seconds.
One-half secolid after the rocket impulse ceases, the explosive coupling fires,
severing the sphere from the after body.
The rocket section drops o$ 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.
Zünder,
http://www.wk2ammo.com
