Monday 28 October 2019

German Explosive Ordnance - Rockets Introduction and Part 1







German Explosives





German Rockets



Introduction


General

The value of the rocket as a weapon of war has been proved during the conflict of the past 5 years.  Even with the vast amount of work that has been done on the rocket during this war, there is a great deal of work still to be done in perfecting it.  During the past few years research work in this field has brought about the following improvements over the old types:


1.  The accuracy has been increased by rotating the projectile.  This is effected by using skew venturi.  The rotations developed range between 1,000 and 1,500 r.p.m. and considerably reduce the deviations of the projectile due to the influence of the wind.

2.  The range has been increased by using a greater weight of propellant in addition to the development of a new powder: Nitrodiglycol.  This new powder is more efficient than black powder and results in greater range and less smoke formation on firing.


3.  Multibarrel projectors carrying up to 42 rounds have been developed by the Germans to effect a greater rate of fire.  Reloading these new projectors is carried out mechanically.


When these first new efforts proved successful, great new exertions were made on the part of the Germans to develop more effective rocket weapons: rocket-propelled depth charges, anti-tank weapons, anti-aircraft rockets, flares, and aircraft bombs with rocket propulsion were tried out; and at the peak of the research program came the radio-controlled long range rocket which was still under development at the end of the war in Europe.



Solid Fuel Rockets

The following is a brief resume on the construction of the rocket at the beginning of this war.  The rocket motor consists of the combustion chamber sealed at one end and the base plate which threads into the open end of the combustion chamber.  The base plate has a series of holes in it, some of which are parallel to the axis of the rocket and some of which are inclined 45 degrees to the axis.


Propellant.  The propellant used at this time is the solid nitrodiglycol type.  Its advantage lies in the high calorific value and smokelessness, also in the slow rate of burning.  Its density is 1.5 kg/m^3, which is less than black powder, but this is compensated by the higher calorific value.  The range for an 8.6 cm rocket using this type of propellant is 1,200 meters.  Maximum velocity is 200 m/sec with a burning time of 5 seconds.  This is not considered very good performance and so the rocket is used only against low level attacks.

As long as long range is not required, powder may be used for rocket propulsion.  It must, however, be remembered that powder rockets are heavy (heavy combustion chamber) and that the charge/weight ratio is small.  An attempt might therefore be made to develop powder rockets o flight construction, by using some arrangements for reloading the combustion chamber so that a larger weight of propellant may be carried.  This should increase the range.  Experiments on these lines have been carried out in Germany, but it was found that in order to insure reliable operation, the constructional complications became very great.  This reduces use of the main advantages of rockets - less weight and simple construction.


Stabilization.  The foundation for the method of stabilization was the spinning shell.  By placing the ventureis askew to the main axis of the rocket produced a sufficient spin.  This action gives rise to a gyroscope effect and tends to resist all external disturbing forces.  This method has given very good results and is greatly superior to the fin stabilization, which is inherently subject to wind errors.



Liquid Fuel Rockets


The liquid fuel rockets are superior to power rockets as regards to:

1. Weight ratio of the propellant carried.
2. Greater energy available in the liquid propellant.


Liquid Propellant.  For example, when 5 gm of powder is required for an impulse of 1 kg/sec, only 0.3 to 0.4 gm of hydrogen-oxygen mixture is required for the same impulse.  It will be seen that there is, in this case, a vast difference in the energy content of the propellant, moreover, the density of the liquid fuels is far greater than that of powder.  The time of burning is increased, greater velocity is reached, and altogether the advantage lies in much lighter construction, i.e., deadweight of the rocket, since the fuel and oxygen containers can be made of thin steel sheet.  The combustion chamber also becomes lighter.

However, the load on the combustion chamber becomes a problem, because of the greater energy and therefore higher temperatures; but this problem was solved.  Combustion temperatures for powder rockets are approximately 980 to 1,000 degrees Celsius; they are 3,000 to 4,000 degrees Celsius for oxygen-hydrogen mixtures, and in addition there is the boiling point of the mixture, the boiling points for hydrogen and oxygen being 253 and 183 degrees Celsius respectively.  These temperatures make severe demands on the material, and it is necessary to look for new alloys which can withstand these demands.

It is, of course, possible to consider other fuels than a hydrogen-oxygen mixture, e.g., petrol, benzol, methyl alcohol, petroleum, spirit, etc., together with liquid-oxygen.  These fuels have the advantage of a high boiling point and do not require special materials for the tanks; these are only needed for the oxygen.



Fuel Tanks.  For the hydrogen and oxygen containers, for example, it is possible to use an alloyed steel, covered with a thin lead coating; if the rocket is to be used only once.  At low temperatures (-183 to -253 degrees Celsius), all metals except copper become hard and brittle; however, copper remains ductile even down to such temperatures, and is therefore the best material to use for the fuel tanks.

The containers for liquid fuels at temperatures lower than -160 degrees Celsius are best made spherical (e.g., V-1), since this form offers the greatest strength.  They must be insulated, but this offers no difficulties.







PC 1400 FX Radio-Controlled Glider Bomb


Overall Length: 130 inches
Length of the Control Unit Housing: 16 inches
Length of Fins at the Root: 31 and 5/8 inches
Length of Fins at Outer Edge: 18 and 1/4 inches
Length of Fin Leading Edge: 18 and 5/8 inches

Max. Width of Tail Unit: 48 inches
Min. Width of Tail Unit: 33 and 3/4 inches
Span of the Fins: 58 and 3/4 inches

Weight of Filling: 270 kilograms
Total Weight: 1,650 kilograms (approx.)



General Description: The PC 1400 FX is a radio-controlled glider bomb designed for attack against capital ships or similar targets.  The complete missile consists of three distinct units: the H.E. armour piercing warhead, the control unit housing, and the tail assembly.  There are four aluminum alloy fins secured ot the missile at approximately the center of gravity.  The purpose of these fins is to give the bomb sufficient lift so that the control surfaces in the tail unit can exercise adequate influence.


Warhead: The warhead is an ordinary PC 1400kg bomb to which four above-mentioned fins have been attached.  It has one transverse fuze pocket located aft the H-type suspension lug.  Two horizontal exploder tubes are centered in the warhead to insure high order detonation on impact.  The usual filling for the warhead is 50/50 amatol.


Control Unit Housing: The control unit housing, made of cast magnesium alloy, is attached between the base of the H.E. warhead and the tail unit.  This space contains the gyroscopes, radio receiver, power source, and a small demolition charge for destruction of the control unit.

There are two gyroscopes mounted 90 degrees to each other in the after section of the control unit.  These two gyros control the stabilizing flaps on two of the tail surfaces.

The directional apparatus consists of the radio receiver and the servo motors which take the impulses from the radio.  The power source is a 24-volt battery.  This equipment operates four control surfaces measuring 8 cm by 1 and 1/2 cm, which are located on the trailing edge of each of the four fins.  These control surfaces are actuated in pairs; two of them control the lateral direction of the bomb, and the other two, its trajectory.

The demolition charge consists of approximately 1 and 1/2 pounds of penthrite wax.  It is fuzed usually with the VZ 80 "all-ways action" fuze.  The main purpose of this charge is to destroy the directional equipment in case the fuze for the main charge in the warhead fails to function.


Tail Unit: The tail unit consists of an inner cast magnesium alloy tail cone fitted with two long and two short case magnesium alloy struts.



Operation.   Bombing with the PC 1400 FX is carried out in conjunction with the Lotfe 7D bomb sight.  The only extra duty of the operator being to switch on the gyroscope of the bomb some 2 minutes before the moment of release.  The aim of the bombardier is taken the same way as in ordinary bombing.  AS the bomb is released, the aircraft is throttled back and put into a climb with the flaps down.  This action is to insure not overshooting the missile.  Once the requisite reduction in speed has been effected, the pilot flattens out.

At this time, corrections in the course of the missile can be taken if necessary.  At the moment of release, the bombardier starts a stop-watch going.  The bomb cannot be controlled during the first 15 seconds after release.  On the 16th second, the operator takes control of the missile.  It has been estimated that the missile can be guided with a margin of error of only 50 meters from an altitude of 7,000 meters.

The bomb takes 42 seconds to reach the ground from 7,000 meters, and 38 seconds from 6,000 meters.  The lowest possible height for satisfactory release is 4,000 meters.  At the moment of impact, the bomb, dropped from 7,000 meters is said to have a velocity of 270 meters per second.





Next Time: Rockets (Part 2)


Source: German Explosive Ordnance Vol. 1: Bombs, Rockets, Grenades, Mines, Fuzes & Igniters

Monday 21 October 2019

German Explosive Ordnance - Containers (Part 5)







German Explosives





AB 500-1B Container


Overall Length: 80 inches
Tail Length: 29 inches
Tail Width: 17 inches
Diameter of Body: 18 inches
Filling: 28 SD 10 FRZ bombs


Colour and Markings: Markings on container - 28 SD 10 FRZ


Construction: The AB 500-1B container is similar to the AB 500-1.

The 28 SD FRZ bombs are accommodated in the central compartment of the container, 15 bombs being accommodated in the rear portion and 13 bombs in the forward portion.

Bombs are loosely packed nose to tail and are not secured by bands.






ABB 500 Container


Overall Length: 69.6 inches
Body Length: 25.2 inches
Body Diameter: 18.4 inches
Wall Thickness: 0.05 inches
Filling: 133 1-kg incendiaries, 2,200 "crow's feet"
Total Weight: 152.4 kilograms


Colour and Markings: Inside and outside of container is painted a dull slate grey.  There are two red bands; one is around the midsection of the bomb body, and the other is around the nose of the bomb.

Letters "ABB 500" are stenciled in black at center of bomb between the fuze pocket ad the suspension lug.

Letters "1941 bbZ 170 7" appear on tail fin.


Construction: The body is cylindrical shaped similar in appearance to a SC bomb except for the nose, which is more blunt.  The bomb is divided into two halves longitudinally and united by a rolled joint.  The vanes and other fittings are welded.  A loading hatch is screwed to the body just forward of the fuze pocket.  There is only one fuze pocket which is 7 and 3/4 inches in depth.  Fuze pocket contains one annular picric acid pellet fuze and a wooden cylindrical packing piece.


Operation: The aerial burst action of the fuze and picric acid pellet splits the case in half down a weak weld.


Suspension: Horizontal.


Remarks: The bomb container is a C 500 flam casing adapted to carry approximately 133 1-kg incendiary bombs.  Among the 1B's found, in one container were some chalk cement rods (with a wire core) 1.9 inches in diameter (possibly used as filling pieces.)






"Streubrand C 500" Container

No picture available

Overall Length: 69.5 inches
Body Length: 18.8 inches
Tail Length: 24.5 inches
Tail Width: 25 inches
Filling: 1,200 green celluloid incendiary boxes immersed in water.



Construction: The Container is similar in appearance and dimensions to the ABB 500 Container, with the exception that the loading hatch is absent as in the AB 500-1.

A 7/16 inch internal diameter steel tube, welded to the upper half of the casing directly above the longitudinal joint of the two halves of the container, connects at right angles to the side of the fuze pocket to which it is also welded.

A single length of green detonating fuze leads from this tube to turn along the longitudinal joint and run round the nose of the container, returning via the junction of the tail to enter the 7/16 inch tube.  At intervals along the longitudinal joint steel clips are placed to secure the detonating fuze firmly in position.

The two halves are hermetically sealed together by welding at the longitudinal seam.  Inside the container is a steel strut, which is used to give support to the two halves of the casing.  The strut is weakened in one place.

Screwed to the fuze in the normal way is a standard gaine projecting into a wood packing piece.  One end of the detonating fuze is housed in this packing piece to contact the side of the gaine.

On release of the container, the fuze is charged.  After a short delay, the fuze fires, firing the gaine which in turn detonates the detonating fuze.  Detonating wave travels round the seam of the container to separate the two halves.  The weak part of the internal supporting strut is broken and the two halves are parted.


Remarks: The Streubrand C 500 appears to have been an inefficient incendiary weapon, and the method of separating the two halves of the container may have been found to be unsatisfactory in practice since damage to exposed detonating fuze would result in failure.






Mark 500 Boden Container


Overall Length: 69.6 inches
Body Diameter: 18.4 inches
Wall Thickness: 0.05 inches
Tail Length: 24 inches
Tail Width: 2 inches

Filling: 9 or 15 single candle flares and 6 SD 2 bombs.


Color: Slate grey or black overall.  Stenciled between the fuze pocket and suspension lug:

Mark 500 Boden
6 SD



Construction: This container is similar to the AB 500.  The tenth flare normally carried in the ABB 500 has been replaced by a subsidiary container for 6 SD 2 bombs.  Instead of the usual opening device, the container is opened by means of a continuous strand of detonating cord (green with pink filling, thought to be penthrite) which circumscribes the container at the junction of the two halves.

The subsidiary container for the 6 SD 2 bombs is anchored by the double wire cable to the U-shaped bracket positioned in the lower half of the body to one side of the internal suspension strip.  The 6 SD 2 container is formed along the longitudinal axis in two halves, retained by the two steel female end caps drilled at the side to admit the thin container securing wire.  Secured to each end cap is a U-shaped bracket, a 0.25 inch round bar, to which is attached the double wire cable.

After the 6 SD 2 container falls free, it is arrested by the double wire cable.  The jerk is so applied to the end cap that it suffices to break the securing wire and the end cap is pulled off.  The bombs then are free to fall away.


Suspension: Horizontal.






AB 1000-2 Container


Overall Length: 123 inches
Body Diameter: 26 inches
Wall Thickness: 0.075 inches

Filling:
-620 1-kg 1Bs; or
-246 1-kg 1Bs and 234 2-kg B.2 EZs; or
-372 2-kg B.2 EZs


Color and Markings: Light khaki overall.

Markings on body:

AB 1000-2
B.1.3 EZ
B 2 EZ



Construction: The body is T-shaped in cross section.  The longitudinal axis of the container is formed by two sheet steel plates 26 and 1/2 inches by 70 inches.  Indented together with circular spot welded pressings and welded along their greater dimensions to two U-shaped girder pieces.  Two circular sheet steel plates form the nose and tail bulkheads.  A slightly domed sheet steel nose is welded to the nose bulkhead and is reinforced by a tubular steel sheet approximately 8 inches long welded to both the bulkhead and the domed nose.  A sheet steel top plate is welded to the upper U-shaped girder to form an arc-line canopy extending 13 and 1/2 inches on either side of the girder.  The top plate is recessed to receive the H-type suspension lug and to accommodate the fuze pocket.

The central support for the tail unit is a steel bar welded to a square plate which in turn, is riveted to the tail bulkhead.  A flanged circular sheet steel plate is spot welded to the tube and tail cone for added support.  The tail fins consist of two layers of sheet steel pressed together, each layer being part of the adjoining quadrants of the tail cone.  Fuzes are housed in a thin sheet steel box inside the tail cone and are welded to the tail bulkhead.  An inspection hatch in the tail gives access to the fuzes.

On the under side of the fuze box are two steel clips which accommodate the 4 ounce penthrite charge provided to destroy the electromagnet generating units attached to the bottom end of the fuze.  Five sections containing incendiary bombs can be arranged in each side of the center bulkhead of the container.  Each section is separated by semicircular sheet steel separator plates.  The bombs are held in place by five sheet steel retaining bands which are drawn tightly around the bomb and container by turnbuckles.  Each strap is held in position at the lower edge of the vertical position by a large split pin anchored to a bracket support which carries a small charge consisting of two detonators.  Two rectangular steel plates near the nose hinge outward when the forward band is severed and form air brakes.

The fuze pocket accommodates the charging head from which six orange colored cables are led to the fuzes.  Two of the cables are connected by a fuze charging attachment to the head of the (89) B fuze; the remaining for cables are connected in pairs to two bayonet joint charging attachments housing the (69) D fuzes.  Six leads pass from the fuzes to a junction box in the tail unit.  Leading from the junction box are three cables for each of the six points (five retaining bands and the destroying charge on the steel fuze box), plus six black colored cables, all of which are enclosed in a green cover.  Four of those leads branch off to each of the five retaining bands (two wires to each det.) and four leads branch off to the self-destroying charge.

All detonators on the (89) B fuze circuit are instantaneous while the detonators on the (69) D fuze circuits have delays varying from 1 to 6 seconds, the variance between detonators being 1 second.  They are so placed that the 1-second delay is on the band nearest the tail unit, the 2-second delay is next, etc.  The 6-second delay detonator is used on the self-destroying charge of the fuze box.  On release, an electrical charge is imparted to one of the plungers of the charging head, depending on which of the fuzes is to be used.

The fuze functions and ignites a black powder pellet which drives a piston forward.  A projection of the piston strikes a soft iron core in the center of a coil of copper wire enclosed within a magnetic sheath.  The rapid displacement of this iron core induces an electric current in the coil which is passed to the junction box and then to the detonators which sever the bands.

Containers can be dropped from low altitudes with the (89) B fuze and instantaneous detonators used to secure a heavy concentration of bombs, or containers can be dropped from high altitude with the (69) D fuze and varying delay detonators used.  This would give a wide dispersion of the bombs.



Suspension: Horizontal.







Message Tubes (Sea and Land)


Sea
Overall Length: 14.75 inches
Body Diameter: 2.6 inches
Total Weight: 2.25 pounds



Land
Overall Length: 15.75 inches
Body Diameter: 2.0 inches
Total Weight: 1.5 pounds


Color: Yellow overall

Markings:
Meldebusche (land)
                Unegefahrlich (not dangerous)
                              Wechtige Moldung (important message)
                         Sofort Weitergeben (forward at once)


Construction: The sea message tube is made of aluminum and is painted yellow.  The top is closed by a disc with a friction igniter through it.  The igniter has a red top and a delay pellet giving a delay of 1 second.  The aluminum smoke container is below the igniter.  It contains a reddish brown powder, the surface of which has a black powder charge to start the burning of the smoke mixture.  The container is made watertight by tightening the wing nut.

The smoke container is 5.4 inches in length, has a diameter of 1.75 inches and weighs 0.75 pounds.

The land message tube is made of aluminum and is painted red.  The top cover holding the red-topped friction igniter (1-second delay) is a push fir over the container.  Through a hole in the cup-shaped aluminum piece near the cover protrude the ends of four strands of quickmatch.  These strands run down the side of the smoke container and meet several pieces of fire quickmatch below the smoke container.

When ignited, the reddish brown powder gives off a very bright yellow smoke.  The smoke container is 5 inches in length, has a diameter of 1.75 inches, and a weight of 10.3 ounces.












Next Time: Rockets - Introduction and Part 1


Source: German Explosive Ordnance Vol. 1: Bombs, Rockets, Grenades, Mines, Fuzes & Igniters