Experimental Antisubmarine Rocket Launcher, firing all eight rockets during tests at Key West Naval Station, Florida, 14 August 1942. This appears to be a prototype for the later “Mousetrap” Anti-Submarine Warfare weapon.
In an experiment on 4 June 1942, U-511 went to a depth of fifteen meters, about fifty feet, and fired rockets. This was the first time this was done from a submerged submarine.
Below courtesy of Uboat net: uboat.net/boats/U 551 Rocket experiment
General notes on this boat
31 May 1942. During the summer of 1942, when under the command of Kptlt. Friedrich Steinhoff, U-511 took part in one of the most interesting experiments of the entire war. Steinhoff’s brother, Dr. Erich Steinhoff, was working at Peenemünde on the rocket program, and between them they arranged for U-511 to be used for rocket trials.
A rack for six 30 cm rockets was installed and extensive tests carried out. These concluded with the successful launch of rockets from a depth of 12m (40ft). These amazing tests failed to convince Dönitz’s staff of the merit of this innovatory weapon system, and it was not put into service. The rocket in question, the 30cm Wurfkörper 42 Spreng, was not advanced enough to target ships, but it might have been used to bombard shore installations such as oil refineries in the Caribbean. This idea was developed in late 1944 with a proposal for Type XXI electro boats to tow V-2 launchers which would attack shore bases. Neither the launchers nor the Type XXI boats became available before the war ended.”
Nonetheless, from the later summer of 1944 through the end of the war, Admiral King, Chief of Naval Operations and Commander-in-Chief US Fleet (the only man ever to hold both offices. Commander-in-Chief US Fleet was abolished after WW Two came to an end) and his staff were very concerned German Uboats might try and make rocket attacks on east coast cities in the US. We knew they had been experimenting with firing rockets from uboats. Certainly we and the British had been experimenting with this. But the Germans were far behind which was a relief.