a hinged lid at the bow of the container to access to a servicing platform and connect the container to the submarine to power it. They would prepare the warhead and fuel the missile with liquid oxygen, ethanol and sodium permanganate for the turbopump from fuel tanks located in the container. The missile was prepared for launch from a service room located beneath the missile chamber. The V-2 would have been guided by rails and the empty space would accommodate the ballasts. The exhaust jet was deflected 180° using collecting funnels so the jet could exit upward. This deflection would reduce the rocket thrust and its radius of action of a sea-based V-2 rocket, requiring the u-boat to come dangerously close to the coast. The armed missile would have been ready to launch 30 minutes after reaching its firing position. After the launch, the container could be abandoned or towed back to the base. Initial calculations showed at any one time, a U-boat could tow three submerged containers at periscope depth and at a speed of An attack on US targets would require a 30-day journey to the launching position at an average speed of . Type XXI U-boats, with a range of at surfaced and at submerged, were considered to be ideal submarines to perform such attacks on the US. Problems in the development of the V-2 delayed this project until November 1944. In January 1945, Dornberger submitted over a hundred detailed draft designs. A 300-ton prototype was built by Schichau-Werke GmbH. At the beginning of 1945, successful underwater towing trials were carried out with U-boat 1063. Although its design never reached the prototype stage, the Peenemünde engineers considered using the A-8 version of the V-2 rocket; this was a "stretched" variant that had a longer radius of action, and used nitric acid oxidizer and kerosene propellants pressurized with nitrogen if the losses of hydrogen peroxide could not be kept under 1% per day as planned. The A-8 variant called for -long containers weighing 500 tons. Under the code-name Projekt Schwimmweste ("Project Lifejacket"), confidential reports dated January 3, 1945, and January 19, 1945, indicate the Stetinner Vulkanwerft ("Vulkan Docks") was contracted to build three containers in Stetin by March 1945 and that four test firings with different firing configurations were planned. The evacuation of Peenemünde in February 1945 and the fall of Stettin to the Red Army in April