Canadian Land Mattress Multiple Rocket Launcher, Canadian War Museum, Ottawa, Ontario. The Canadian Land Mattress was a ground-based weapon named after its Naval equivalent. Based on the Z Gun Anti-Aircraft rockets, it was tested in the summer of 1944 and saw some action with British and Canadian troops, with mixed results. The Land Mattress was based on the 3-inch-diameter (76-mm) tube of the RP-3 or”60lb” rocket used as an air-to-ground weapon with Naval 5-inch shells as warheads, and consisted of a 16- or 30-tube launching system mounted on a towed carriage. The land version had an operational range of 8,000 yards (7.3km). Rounds were fired at a rate of 4 per second.