G7a

The torpedo was set in motion by its own engine and kept the set course using the autonomous guidance system. An important source of operation of the torpedo systems was a tank with compressed air , which occupied about half the space inside a 7-meter steel hull.

When the torpedo was launched, its passage through the torpedo tube actuated a special switch and compressed air from the tank through a small pipe and a pressure regulator was fed into the combustion chamber. Passing through additional tubes, compressed air included other mechanical torpedo systems.

Inside the combustion chamber, a mixture of compressed air and fuel from an adjacent tank was ignited by a shock igniter similar to a spark plug . The hot gases from the combustion of fuel turned the chilled water finely atomized in the chamber into a gas-vapor mixture, which actuated the four-cylinder torpedo engine. The engine rotated two hollow drive shafts inserted one into the other, driving two torpedo propellers . The screws rotated in opposite directions to avoid the rotation of the torpedo around its longitudinal axis and it did not go astray.

Torpedo movement at the desired rate was provided using a gyroscope , the rotor of which was also rotated by compressed air at a speed corresponding to three predetermined torpedo speeds of 30, 40 and 44 knots . Sensitive to any deviation from the set course, the gyroscope included a small motor (servomotor), which changed the position of the corresponding rudders. The depth sensor and its servomotor kept the torpedo moving at the required depth by acting on the rudders of the dive.

The warhead on the first G7a type torpedoes had a relatively simple contact detonator . To protect the boat from a possible premature explosion of a torpedo, the detonator had an ingenious mechanism - a small screw rotated by the oncoming water stream brought the detonator into the firing position not earlier than the torpedo was removed from the boat to a distance of 30 meters.

Labor costs for the manufacture of such a torpedo ranged from 3,740 man-hours in 1939 to 1,707 man-hours in 1943 (for comparison, it took 1,255 man-hours to produce one G7e (T2) electric torpedo ).

Germany entered the Second World War, armed with two main types of torpedoes - combined-cycle G7a and electric G7e. Both torpedoes had their advantages and disadvantages. The main disadvantage of the combined cycle torpedo was the bubble trail clearly visible on the water, caused by the operation of the steam turbine unit. But the G7e torpedo, devoid of this drawback, had a small, in comparison with the G7a, range of about 3,000 meters. In addition, it was inferior to a combined cycle gas torpedo in terms of speed — 30 knots versus 45. Therefore, the standard set of Kriegsmarine submarines in 1939–1943 consisted of both gas-vapor and electric torpedoes.

Torpedoes manufactured before 1940 also had an unreliable gyroscopic device, which was responsible for controlling the depth of the torpedo. Therefore, after the first failures of this system, German submariners began to set the minimum depth of the torpedo to eliminate this drawback. Also, a contact-proximity fuse pi1 was causing a lot of trouble at the beginning of the war, and then many cases of failure of this fuse were recorded. Very often, torpedoes with a non-contact fuse detonated prematurely, which at least unmasked the submarine, or did not explode at all when passing under the target. The contact fuse was also not perfect - at contact angles with a target significantly different from 90 degrees, the torpedo simply ricocheted off the side of the ship. All these shortcomings were quickly eliminated, already after the Danish-Norwegian operation, the Kriegsmarine torpedo weapon reached a satisfactory level.

Since the fall of 1942, in connection with the increased effectiveness of the anti-submarine forces of the Allies, it became increasingly difficult for German submariners to attack the convoys of the Allies. The way out of this situation was the installation of directional guidance systems on torpedoes (FaT and LuT systems) according to the plan, in case the torpedo did not hit the target in the first direct section of the trajectory, then after passing through this direct section the torpedo began to maneuver according to the given programs, as a rule , "A snake." This system was first installed on a G7a torpedo and had a very high efficiency. The FaT II system that appeared later had two independent gyroscopes, which theoretically made it possible to launch a torpedo on a target, being at any position relative to the target's course. First, the torpedo overtook the target, then turned on its nasal angles, and only after that began to move “snake” across the course of the target’s movement.

Since 1943, the G7a torpedo began to be supplanted from the submarine ammunition by the more advanced G7e (T-III) electric torpedo, which was also much easier to manufacture. By the end of the war, only 2-4 G7a torpedoes were in the ammunition of German submarines.

The first German TZ1 magnetic fuses were of a static type, reacting to the absolute magnitude of the vertical component of the magnetic field, they simply had to be removed from service in 1940 after the Norwegian operation. They were triggered after the torpedo passed a safe distance even with slight waves of the sea, in circulation or with insufficiently stable torpedo travel in depth. As a result, this fuse saved a lot of British sailors from imminent death.

New non-contact fuses appeared in combat torpedoes only in 1943. These were Pi-Dupl magnetodynamic fuses, in which an induction coil was a sensitive element. Pi-Dupl fuses reacted to the rate of change of the vertical component of the magnetic field strength and to the change of its polarity under the ship's hull. But the response radius of such a fuse was 2.5–3 m, and for demagnetized ships (in 1943) it barely reached 1 m.

Only at the end of the war, the German Navy adopted a non-contact fuse TZ2 , which had a narrow response band lying outside the frequency ranges of the main types of interference. As a result, even along a demagnetized ship, it provided a response radius of up to 2-3 m at meeting angles with a target of 30 to 150 °. The minimum depth of the torpedoes with the Pi-Dupl and TZ2 detonators was 2-3 m, and at a depth of 7 m the TZ2 detonator had virtually no false positives due to sea waves. The disadvantage of the TZ2 was the need to provide a high relative speed of the torpedo and the target, which was not always possible when firing low-speed electric torpedoes.

The torpedo had the following specifications:

• Length - 7186 mm.
• Case diameter - 533 mm.
• Weight - 1528 kg.
• Speed ​​- there were 3 speed modes - 30, 40 and 44 knots .
• Range - 12,500 m at 30 knots, 7,500 m at 40 knots, 5,500 m at 44 knots.
• The weight of the combat charging compartment is 280 kg.
• Fuse - KHB Pi1 or KHB Pi1 8.43-8.44
• Type of fuse - contact non-contact

For German torpedoes the following designation was used:

• The first position is the diameter: F = 45 cm, G = 50 or 53.3 cm, H = 60 cm, J = 70 cm and M = 75 cm
• Second position - length: length rounded to whole meters
• The third position is the type of power plant: D = torpedo with "wet heating" (World War I), a = combined-cycle gas, e = electric, u = hydrogen peroxide

Thus G7a means: combined-cycle torpedo with a diameter of 53.3 cm, a length of approximately 7 meters.

Pre-war 533-550 mm torpedoes for surface ships ^[1]

• G7e

• M. E. Morozov, V. A. Nagirnyak. Hitler Steel Sharks. Series "VII" . - M .: “Collection”, “Yauza”, “Eksmo”, 2008. - 144 p. - ISBN 978-5-699-29092-5 .
• Translation from English by M. Ivanov. Wolf packs. - M .: "Terra Book Club", 1998. - 192 p. - ISBN 5-300-01699-3 .
• Campbell J. Naval weapons of World War Two. - Annapolis, Maryland: Naval Institute Press, 1985 .-- P. 403. - ISBN 0-87021-459-4 .

• Characteristics of German torpedoes on the site www.uboat.net