M17 rocket launcher “WhizBang” named Arlene III, 1944
The 7.2-inch demolition rocket was developed in response to the need for a more powerful explosive charge for use against heavily fortified obstacles during World War II. Initially adapted from a Navy anti-submarine weapon, the first version, designated the T37, carried a 32-pound plastic explosive payload. Although the round weighed 61 pounds, it had a limited range of only 230 yards due to its maximum velocity of 160 feet per second. To improve this, a later variant, the T57, used a larger 4.5-inch rocket motor, extending the range to 1,200 yards.
Given that the demolition rockets were intended to be fired at relatively close range, armored rocket launchers were developed for use on tanks. The most widely employed version was the T40, which was eventually standardized as the 7.2-inch multiple rocket launcher M17. This launcher was mounted above the tank turret and carried 20 rockets arranged in two rows of ten on 90-inch rails. The launcher itself weighed 4,615 pounds and was protected by half-inch armor, designed to withstand small arms fire.
The M17 “Whizbang” launcher was controlled from inside the tank. An arm connected to the main gun allowed the crew to adjust the elevation from +25 degrees to -5 degrees, and the rockets could be fired individually or in a rapid ripple fire sequence at intervals of half a second. Additionally, the launcher could be jettisoned after firing to allow the tank to revert to normal combat operations. The M17 saw combat during the invasion of southern France and throughout the Italian campaign.
A modified version, the T64, was produced in limited quantities for use on armored engineer vehicles. It was similar to the M17 but featured changes to the firing panel and auxiliary equipment. It could handle different sizes of rocket motors, including 2.25-inch, 3.25-inch, and 4.5-inch motors.
Late in the war, the T73 multiple rocket launcher was developed as a more advanced system. It differed from its predecessors by carrying a single row of ten rockets on shorter 50-inch rails. The T73 offered better protection, with 1-inch armor on the front and sides and half-inch armor on the top and bottom, making it resistant to .50 caliber fire. Unlike the M17, it rotated with the turret but had independent elevation control, ranging from +45 degrees to -5 degrees, operated by an electric drive. The launcher was not attached to the tank’s main cannon and could be ejected by a hydraulic mechanism. Capable of firing at a rate of 2 rounds per minute, the T73 could accommodate rockets with various motor sizes and also had the option of firing 7.2-inch chemical rockets.