Developed during World War II, the Habakkuk was used by British and Canadian forces as a way to introduce a new kind of aircraft carrier that would combat German U-boats in the Mid-Atlantic. The carrier would have been made of a material called Pykrete, which was a combination of wood pulp and water that, when frozen, could be molded and held up to melting temperatures far longer than ice. While a scale model of a Pykrete carrier was considered for a time, the project eventually fell out of favor for a variety of reasons and never truly reached fruition.
The Sun Gun
One of many strange and nearly impossible military projects the Germans worked on during World War II, the “sun gun” was a theoretical weapon that would have harnessed sunbeams in order to boil water sources and burn cities. According to the scientists who had developed the idea, a satellite would have been positioned in orbit with a mirror attached to it that would allow the focused sunlight to be directed at a target. Allied interrogators who spoke with the scientists at the end of the war reported that the Germans believed the project, should it have been undertaken, would have been completed in 50-100 years.
First tested in 2007, the Boeing YAL-1 was a prototype aircraft developed to house a laser system that could be used to destroy targets with concentrated bursts of energy. The project was tested for several years and the system successfully destroyed two test missiles during a 2010 test. Despite the successes, however, the project was eventually shut down as other, more effective options were being considered.