Each artillery 21-cm rocket - designated as "21-cm Wurfgranate 42" - was a specially-designed projectile that externally mimicked traditional artillery ammunition. The slim nose cone provided the needed aerodynamic flow and the body was cylindrical in shape, leading to a cut-off base without any noticeable stabilizing fins. However, this external design was somewhat misleading for the warhead, normally contained in the nose cone assembly on an artillery projectile, was in fact fitted well-aft of the tip - the tip instead left hollow. The 14.3lb engine was fitted to the front of the projectile housing while twenty-two angled "venturi" were affixed to the projectile base to give it the needed spin stabilization during flight. These openings were set at 16-degree angles from axis and provided a clockwise "rifled" rotation or spin during flight. Some 22.4lbs of explosive made up the projectile's deadly payload - only high-explosive charged projectiles were ever produced for the Nebelwerfer 42 (no AP rounds were designed). However, special liner rails could be fitted inside of each launch tube to accept the 15-cm Wurfgranate 41 series rockets which, themselves, could be capped with high-explosive, smoke or even poison payloads. Additionally, rockets could be fitted with a delayed fuse or impact detonation as needed.
The firing action required the Nebelwerfer team to remove themselves from the direct vicinity of the readied launch tubes, finding cover wherever possible. When the firing order was given, a crewmember activated the launch plunger and the launch tubes responded, launching one rocket at a time in a predetermined launch order until all rockets were clear of the tubes (it is of note that the system could not single-fire individual rockets, only sets of rockets in this staggered launch fashion). The crew could then displace the projector to another location or reload fresh projectiles into each launch tube for another deadly salvo. A full salvo was unleashed in just eight seconds.
As can be expected, the Nebelwerfer 42 firing action was not without consequence; with each launched rocket there emitted a good amount of "back blast", stirring up a great deal of dust and debris while also producing smoke trails (from the rockets) in the process. This, in effect could supplying the weapon's general location to an observant enemy on the receiving end, opening the Nebelwerfer crew to a heavy artillery or like-rocket response in turn. Additionally, the rocket launch sequence provided a discernable level of noise that could be instantly recognized by the enemy, giving up the initiative to an extent. The enemy now knew the weapon type, ammunition being utilized and the approximate time for reloading. However, no one could discount the power of Nebelwerfer units as a whole, particularly when paired with other like-units or artillery, and its general effectiveness far out-weighed the battlefield dangers.
Along the East Front, Nebelwerfer systems were generally fielded alongside artillery systems for a one-two punch in support of German Army ground actions. Nebelwerfer 42s were issued in groups numbering six launchers with three groups per battalion organization and were fielded as independent brigades. Beyond the East Front, Nebelwerfer teams were unleashed against the Allies across North Africa, in occupied France and across fascist Italy, the latter after the 1943 Allied campaign.
Such was the power of the 21-cm Nebelwerfer 42, in fact, that the Americans captured intact specimens, sending them back stateside for evaluation; America generally lagged behind the other powers in design and production of similar rocket projectors. To this extent, the Americans outright copied the Nebelwefer 42 under the designation of "T36". Though this system was never placed into production, it served as a vital testbed for the US Army.
The German Luftwaffe also found value in the Nebelwerfer 42 rocket and designated it as the Werfer-Granate 21 ("WGr. 21", also "Bordrakete 21" - "BR 21") beginning in 1943. This version differed in utilizing a timed fuse with a larger warhead for affecting the large Allied bomber formations wreaking havoc on German war-making infrastructure through day and night sorties. These rockets were fitted into specially-designed single-launch, firing tubes to be utilized by German fighters, heavy fighters and dedicated "bomber destroyers".
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