German Explosives
Wasserfall C-2
General Description
A. This flak rocket was given the name Wasserfall and the designation C-2 8/45.
B. The C-2 was designed to be launched vertically from the ground, and traveling at a supersonic speed to be guided into bomber formations where it would be exploded.
C. The Wasserfall resembles a half-size V-2 with small wings. It has a similar motor and is launched in much the same manner. Its control gear is also similar.
It could reach a maximum speed of about 770 meters per second in about 45 seconds after which time the speed would decrease as the fuel would be exhausted. It could still chase targets until its speed had dropped to about 350 meters per second. Its maximum fighting ranges were : 18 kilometers in height and 26 kilometers in horizontal range. It was designed to withstand maneuvers of up to 4.4g. The missile was guided by radio signals from the ground until approaching the target at which time a self-contained homing system was to lead it in. It was planned to incorporate a proximity fuze to explode the weapon close to the bombers.
With these properties the Germans expected every other missile to bring down a bomber making 2g evasive maneuvers at a speed of 250 meters per second.
Operational Aspects
A. The Wasserfall was planned for use from the ground against air targets, specifically bombers. Suggested locations for launching sites were along the French coast and the approaches to major targets of bombers.
B. The launching site requires much equipment and, although mobile, would thus be subject to attack. Lack of maneuverability against relatively slow airplanes would have inhibited its effective use.
C. The Wasserfall was expected to be both cheaper and more effective than ordinary flak for the results obtained. Only operational use could prove this point.
Recommendations: It is believed that an intensive study of the Wasserfall will yield much information on the principles and the use of a supersonic guided missile.
Details
Airframe
Type and Description: In overall appearance the Wasserfall resembles a half-size V-2 with small wings. The approximate dimensions are:
Length: 7,800 mm
Caliber: 880 mm
Wing Span: 1,890 mm
Tail Span: 2,500 mm
There are four small biconvex dorsal wings at the center of gravity to assist in making turns. In line with these wings are four stabilizing fins at the tail. Control surfaces are fitted on the stabilizing fins both in the air stream and in the gas stream of the jet motor.
Aerodynamic Characteristics: The Wasserfall is designed to catch, while traveling at a supersonic speed, a target having a velocity of 250 meters per second doing 2g maneuvers.
Essentially the missile travels at and is designed for supersonic speed. However, the transition from zero speed at launching to the supersonic range is not instantaneous and some additional control is desirable during this interval. This is supplied by the gas stream fins which are present for the first 5 to 15 seconds of flight. Once the supersonic range is reached the air stream fins supply sufficient control while the jet stream fins add a drag. Consequently they are jettisoned at that time.
The missile is designed to stand maneuvers up to 4.4g. The wings will support a light of 8,000 kg per pair to which the body, tail, etc, add about another 4,000 kg making a total lift of 12,000 kg.
The missile weighs about 3,500 kg at take-off, but the weight drops continually to about 1,500 kg by the time the fuel is exhausted. Thus at take-off the lateral acceleration should not exceed 3g, increasing to 4.4g as the fuel is consumed. To allow for this the control applied to the servo is made weak at first and is gradually brought up to its full power.
Wind tunnel tests of models made may be found in report No. UM 6013 dated February 1945 in the Goettingen documents. Evidence obtained at the wind tunnels at Kochel shows that at least six different shapes have been tried out to get the best aerodynamic results.
Design Data: The missile is fabricated from mild steel to the shape shown above. It may be broken down into the following parts:
1. Nose: contains the homing device (zielsuchendes Geraet) fuzes (Zuender) and explosive (Sprengstoff).
2. Nitrogen tank: (Druckluftbehaelter).
3. Visol tank: (Brennstoffhaelter).
4. Wings: (Fluogel).
5. Salbei tank: (Salbeibehaelter).
6. Control system: Mounted to rear of Salbei tank.
7. Tail: Supports motor (Brennkammer), tails (Flosse), air rudders (Luftruder), and jet rudders (Stahlruder).
Production Data: The following remarks apply to all parts of the missile. The only production was by the Electromechanische Werke at Peenemunde for the developmental testing. Estimates of this production range from 40 to 275 units.
Estimates were drawn up for the men, material, and space needed for the mass production of 5,000 monthly.
Propulsion System
Type and Description: A liquid jet motor drive is used with develops an 8,000 kg thrust for 45 seconds. The motor burns a self-igniting mixture of Salbei (nitric acid) and Visol (a hydro-carbon mixture) in a chamber with a venturi nozzle.
Characteristics:
Thrust: 8,000 kg
Total Impulse: 360,000 kg
Launching acceleration: 1.2 to 2.6 g
Final acceleration: Ca. 4 g
Fuel consumption: 41 kg/sec
Specific impulse: 180 to 195 sec.
Design Data: The general arrangement is indicated in the image at top. The foremost flask contains nitrogen at a pressure of 200-300 atmos. This flask is 8 to 13 mm thick and is not wire wound. The compressed gas passes through a reducing valve to 30 atmos and is used to force the liquids out of their storage tanks. This flask and the two storage tanks are made of rolled and welded steel.
The forward storage tank contains about 400 kg or 430 liters of Visol. Visol is a rather variable fuel according to the ingredients available or the intended use. A typical Visol mixture is: 40 percent isoprophyl alcohol; 40 percent vinyl ether; 2 percent water; 18 percent of four other ingredients including 1 percent of a dope to control the ignition delay time.
Visol is a contracted code name for vinylisobutylether. A Diesel oil may also be used in place of Visol.
The rear tank contains about 1,500 kg or 1,100 liters of the oxidant Salbei. Salbei is a mixture of 90 percent nitric acid (including 3 percent 2 water) and 10 percent sulfuric acid. No attempt is made to make the acid water free as it would be reabsorbed from the air before it was ever used. The sulfuric acid was added to prevent corrosion by the nitric acid of the steel available for the tanks.
As already mentioned, the fuel and oxidant were forced out be pressure. The fuel is removed through a swinging pipe hanging down in the tanks. As this pipe is subjected to the same acceleration as the fuel, its end is always covered by liquid. This design gives a lightweight removal system which removes practically the last drop of liquid although the liquids are being swished around in the tanks. It is said this system increased the maximum altitude obtainable by 4 kilometers over a pump arrangement that was tried.
Both fuel and oxidant are passed through a valving arrangement which introduces both liquids into the motor at the same time under full flow. Valves in the various pipelines are opened simultaneously by explosive charges. Just before each liquid enters the motor there is a diaphragm. These diaphragms stop the liquid until it has built up to practically full pressure at which time the diaphragm bursts and allows a full flow of liquid, from the start, to enter the motor.
The ratio of liquids by weight is Salbei to Visol from 5 to 1 up to 8 to 1 depending on the actual Visol mixture being used.
The Visol is fed directly to the nozzle head. The Salbei first apsses through the cooling jacket of the motor before going to the nozzle head. In some cases some of the Salbei is also injected through cooling holes into the combustion chamber. The two liquids ignite within 0.01 to 0.1 second after contact. An expansion ratio of 2.5 to 1 up to 3.9 to 1 is obtained int he motor. The gas exit velocity is approximately 1,850 meters per second.
Brennschluss (turning off of the motor) had not been settled. Provisions were made for several methods, which were:
1. Letting the motor use up all of the fuel.
2. Turning off the motor by radio signal.
3. Turning off the motor at a pre-determined velocity by means of an integrating accelerometer.
Intelligence and Control System
Type and Description: Many systems were tried or proposed which, although radically different in details, ar every similar in function. Three gyros are used to prevent oscillations about the three axes. Remote radio control is used to guide the missile toward the target. A homing device is to be used in the final part of the chase to guide the missile to within killing distance of the target. Finally a proximity fuze is to explode the missile. In addition there is a relay transmitter in the missile to enable the personnel on the ground to follow it.
Characteristics: The control system must be capable of guiding the missile very close to a target which is making 2g curves at a velocity of 250 meters per second.
Design Data
1. Rudders and Rudder Machines: In each of the four tail fins there is a pair of rudders in the air stream and the jet stream. Each pair of rudders is driven by one all-electric servo motor. The armature of the servo motor oscillates at 50 cycles a second to reduce the backlash to almost zero. Roll control is applied to all rudders.
2. Gyros: Three course gyros are used to prevent the missile from oscillating. The take-off cards on the gyros are positioned by the remote radio control to keep the gyros oriented with respect to the desired path.
3. Remote Control Radio Receiver: This unit receives command signals from the ground control station to direct the missile towards the target. The "Strassburg" E230V is employed as the receiver.
4. Relay Transmitter: A transponder triggered from the ground radar to indicate the angle of roll of the missile by measurement of the polarization of the wave transmitted is known under the code name "Reuse".
5. "Mischgeraet": An electrical computing device which receives signals from the control radio and the gyro, mixes these signals, and sorts them out for the various rudder motors.
6. Homing Device: A device to make the missile home in very close to the target. None had been sufficiently developed to test in the missile. It is a pre-requisite as the ground control is not sufficiently accurate to guide the missile close enough to the target to do damage.
7. Power Supply: Batteries, invertors, regulators, etc., to power the control systems.
8. Warhead, Fuze, Firing Circuit: About 305 kilograms of explosive were to be used. Of this, about 100 to 150 kg would be concentrated int eh nose. The remainder would be distributed through the body much in the form of primer-cord. This distributed charge was necessary to destroy the missile in mid-air as it would be used over friendly territory. The warhead was expected to have a destructive range of 40 meters.
9. Auxiliary Equipment: The Wasserfall required considerable ground equipment for the remote control. Equipment is required not only for the transmittal of control signals to the missile, but also to track both the missile and the target. The missile is guided so that it is always on the line between the target and the ground observer. Preferably, the tracking is done optically. In this case, the operator has only to keep the missile and the target lined up in the optical field. However, radar tracking must be provided for the many times that optical tracking will be inadequate. The radar tracking system and control system known as the "Elsass" consists of the following functional parts:
-Mannheim Radar - Radar set to track the target. It also measured the distance between the target and the missile.
-Rheingold - The Rheingold follows the missile and measures the roll position of the missile by determination of the angle of polarization of the signals sent out by the "Reuse" relay transmitter in the missile.
-Indicator - The indicator displays information obtained from the Mannheim and the Rheingold:
-Azimuth and Elevation of target and missile.
-Distance to target and missile.
-Roll position of missile.
-Kehl Control Transmitter - An operator sits before the indicator and by means of a joystick control keeps the missile in line with the target. This joystick controls the command signals sent out by the "Kehl" control transmitter to the "Strassburg" receiver in the missile. By this transmitter the operator may also fire a fuze in the missile when his indicator shows the missile is at the target.
Next Time: Rockets (Part 9)
Source: German Explosive Ordnance Vol. 1: Bombs, Rockets, Grenades, Mines, Fuzes & Igniters
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