บท 167: Chapter 245 The French Doomsday (15)
"Descend to an altitude of one thousand meters."
The commander's order in the air immediately sparked strong dissatisfaction among the other pilots. For bombers, descending to one thousand meters was already quite dangerous—no exaggeration, it was like stepping one foot into hell.
However, the airborne commander had no choice. Prior to departure, superiors issued a life-or-death command, instructing them to collide if necessary but to destroy the German pontoon bridge. In this pitch-black night, finding a target to collide with without being able to see clearly was impossible. They had to lower their altitude first to locate targets and then release the bombs.
Although filled with complaints, the pilots had to obey the order to descend. After all, no one wanted to bear the guilt of fleeing in the face of the enemy, a crime punishable by execution during wartime.
Suddenly, a pillar of light shot up, tearing through the darkness and heading towards the sky. Followed by a second, a third, a fourth...
When the light is weak, the pupils automatically adjust to enlarge, allowing more light to enter and improving visibility. However, the sudden strong light didn't give the pilots, who had been flying in darkness for a long time, a chance to adjust. Their eyes were nearly blinded, and everything appeared as a bright white blur.
"Damn! It's searchlights! Disperse immediately!" The airborne commander warned loudly, well aware that once covered by these lights, the intense artillery fire would follow.
As he spoke, the anti-aircraft positions on the ground had already begun intense firing. Although more advanced fire control radars were not yet in use, the existing anti-aircraft radars accurately marked the direction and altitude of the enemy aircraft, helping the anti-aircraft artillery units calibrate various design parameters in advance.
In anti-aircraft combat, the most effective method was to form a dense barrage, making it unavoidable for incoming enemy aircraft.
How to increase the density of the barrage? Before the introduction of proximity fuzes, there were only two ways. The first was to increase the firing rate of anti-aircraft artillery; the second was to increase the number of anti-aircraft guns when setting up air defense positions.
Because of this, every time an anti-aircraft unit engaged in air defense, the ammunition consumption was always a terrifying number.
During World War II, there were several types of fuzes used for anti-aircraft shells: impact fuzes, time fuzes/altitude fuzes, and proximity fuzes.
Impact fuzes were generally provided to small-caliber anti-aircraft guns. Since shells with impact fuzes had to hit airborne targets to be effective, hitting small, fast-moving targets in high altitudes was extremely difficult, if not impossible. Therefore, these impact fuzes were only given to small-caliber anti-aircraft guns used against low-altitude targets.
Time fuzes operated using an internal mechanism similar to a mechanical clock, powered by the elastic potential energy of a mainspring. There was a scale on the outside of the fuze representing the length of the delay. Before firing, the gun crew needed to observe and determine the height of the enemy aircraft, then calculate the corresponding delay time. A special wrench was required to adjust the fuze to the appropriate scale before firing. When the fired shell traveled the pre-set time, it would explode, causing damage to nearby targets.
The principle of altitude fuzes was similar to that of time fuzes. Before firing, the gun crew set the fuze for the desired burst height. Shells with these two types of fuzes were often fired by larger-caliber anti-aircraft guns.
If these settings were incorrect, even precise aiming wouldn't be effective due to premature or delayed detonation. Because of the limited chances of hitting the target, anti-aircraft guns using these two types of fuzes had to fire a considerable number of rounds in the area where the target might pass to increase the probability of hitting.
For example, during the Battle of Britain in World War II, the British anti-aircraft forces needed to fire 4,200 rounds of large and medium-caliber anti-aircraft shells to bring down one German plane. The cost of these anti-aircraft guns and the ammunition expenditure was probably several times the cost of downing an aircraft. The US 127mm dual-purpose gun, when using shells equipped with time or altitude fuzes, needed to fire 2,000 rounds to bring down one enemy aircraft.
Later, proximity fuzes emerged, eliminating the need for complex calculations. All that was required was to launch shells equipped with this type of fuze in the direction of the target. When the shell approached the target or when the distance between the shell and the target fell below the fuze's preset limit, the shell would automatically detonate, significantly increasing the efficiency of anti-aircraft guns. The 127mm dual-purpose gun, which needed to fire 2,000 rounds to bring down one enemy aircraft, only required an average of 500 rounds when using proximity fuzes.
This radio proximity fuze was developed by the UK based on radar principles. Later, the United States improved it, developing the Mk53 fuze, primarily used on 127mm anti-aircraft guns. Shells equipped with proximity fuzes would, after firing, have their safety devices disengaged, and the fuze would start electrification. The vacuum tube was made into a radio frequency circuit emitting electromagnetic waves at 180-220 MHz.
When approaching airborne targets, electromagnetic waves would reflect back. Due to the Doppler effect, a frequency shift of several hundred hertz would occur. At this point, the shell itself became an antenna receiving the reflected electromagnetic waves. After filtering and amplification, the waves underwent filtering and amplification. When the amplified current reached the threshold (indicating that the target was within the effective kill range), the detonation was initiated, completing the explosive process.
However, this fuze was limited by the electronic technology of the time. The U.S. military could only install it on 127mm anti-aircraft guns; smaller-caliber Bofors 40mm anti-aircraft guns and 28mm anti-aircraft guns could not use it.
In fact, during World War II, Germany also researched proximity fuzes. However, due to inadequate electronic technology, they never managed to develop a radio proximity fuze. Instead, they developed ineffective acoustical proximity fuzes, magnetic induction proximity fuzes, electrostatic proximity fuzes, and various other miscellaneous devices.
Among them, the principle and structure of the electrostatic proximity fuze were quite simple. It only required two dry batteries, a spark discharger, an electric igniter, and a fuze shell with an insulated electric stage. The electromotive force of the batteries was chosen to be slightly less than the discharge voltage of the spark discharger, and no current passed through the electric igniter before approaching the target.
As the shell approached the target, a potential difference would form between the electrodes and the fuze shell, feeding back into the electric circuit. Due to the presence of the potential difference, the voltage applied to the spark discharger lead would increase and proportionally grow larger as the target approached. When it reached a certain distance, the high-intensity static charge released by the target caused the total voltage of the spark discharger to reach a sufficient value for electrical spark discharge. This would finally actuate the electric igniter, igniting the explosive inside the warhead.
The ubiquitous principle of electrostatics, an ordinary electrostatic receiving circuit, could create a highly effective electrostatic proximity fuze. For objects like aircraft that generate thousands of static charges due to their movement, an electrostatic proximity fuze was perfectly suited.
However, it had a drawback: its sensing range was too short, far inferior to radio proximity fuzes, making it impractical. Yet, the German high command regarded this seemingly mediocre device as a treasure and insisted on installing it only on top-notch precision-guided munitions.
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