"High-temperature," though, is a relative term. For pykrete, creep was a major problem at temperatures above about 3°F (-16°C). As a result, it was decided that the pykrete would need to be cast around a framework of steel reinforcement. Furthermore, a refrigeration system was needed. Refrigerant would be carried through a network of steel tubes embedded in the pykrete.
The final design for the iceberg ship would have measured approximately 2,000 feet in length and 300 feet in width. The ship would have displaced 2.2 million tons. By comparison, the US Navy's Nimitz-class supercarriers, the largest warships in existence today, displace 100,000 tons. The miles of tubing for the refrigeration system would have required more steel than would be needed to build many conventional aircraft carriers. The quantity of wood pulp required would have put a severe strain on the paper industry. Ironically, though the project was conceived as a creative response to resource shortages, building the ship as designed could have caused even bigger shortages.
The iceberg ship was never built. The increasing range of land-based aircraft; the construction of small, lightweight escort carriers by the US; and an agreement by Portugal allowing the allies to station aircraft in the Azores Islands turned the tide against the German submarines. A small prototype of the ship, built by unwitting conscientious objectors in the Canadian Rockies, now lies at the bottom of Patricia Lake, where divers can still see its network of refrigeration pipes.
What can engineers learn from this story today? The first and most obvious lesson is to consider creep, along with all other potential failure modes. Another lesson is not to lose sight of the big picture. The team working on this project seems to have viewed the objective as building a ship out of ice, while forgetting that the rationale for doing so was to save resources.
On the other hand, the research and development effort was not a total waste. The understanding of the thermal and mechanical properties of ice gained from this project has helped scientists studying the behavior of natural ice. Experience with pykrete helped spur development of fiber composites after the war. And today, researchers are using ice as a template to fabricate cutting-edge nanomaterials. Perhaps another lesson is that even a failed project can have a positive outcome.