As the US Navy developed doctrine for amphibious operations in World War II, one thing it quickly learned was that there simply was never enough suppressive firepower available. The most famous pre-landing bombardment ships were the battleships, of course, with their massive 14” and 16” guns pummeling suspected positions for hours, even days before a landing. Of course, cruisers and destroyers hurled tens of thousands of shells upon beaches as well. And we’ve written about the smaller ships such as the LCS(L)(3) series.
When it comes to suppressive fires, quantity has a quality all its own. But naval guns are heavy, expensive pieces of equipment. And so, early on, the Navy turned to the humble rocket as a way to quickly boost its firepower. The first rockets in widespread use was the 4.5” Beach Barrage Rocket, or BBR.
A simple solid rocket motor on the back end of a 20 pound warhead, the BBR was fired from a simple metal rack. It had a very modest range of about 1100 yards, and wasn’t terribly accurate. But it could be carried in large numbers by even the smallest of ships and craft.
The BBR made its combat debut during the Torch landings in North Africa, and saw extensive use throughout the war. The Navy was generally happy with this simple weapon, but also wanted something with longer range, on the order of 5000 yards, or even 10,000 yards.
Rockets launched from the ground, and using fins for stabilization, are inherently somewhat inaccurate. While the wide dispersion of the BBR was tolerable given its maximum range, a rocket for longer range use would have to be more accurate. And so, the Navy tasked CalTech to develop a spin stabilized rocket. After initial efforts looking at a 3.5” rocket, CalTech soon developed a family of 5” rockets that were spin stabilized by slightly canting the exhaust nozzles of the rocket motor. A variety of warheads were available, such as smoke and illumination, but the two most used were “common” shells with high explosive warheads, one with a range of 5000 yards, and one with a smaller charge, but a range of 10,000 yards.
Among the first ships equipped with the 5” High Velocity Spinner Rocket (HVSR) were PT boats.
The Mk 50 launcher could be installed port and starboard aboard a PT just forward of the charthouse. Stored position had them inboard.
But for firing, they were traversed outboard, so the blast would not impact the relatively fragile wooden decks.
The Mk 50 was fixed in train- that is, the only fired straight ahead. It was, however, fitted for elevation. Varying the elevation of the launcher determined the range of the shot. Aiming was via a reflector gunsight at the helm. Mind you, a bobbing 80 foot boat wasn’t the most stable platform, but the rockets added considerable firepower to boats that already punched above their weight.
The biggest users of the 5” HVSR were the LMSRs, or Landing Ship, Medium, Rocket. The LSM, widely used in the Pacific in the second half of the war, was adapted to carry hundreds of rockets. Early iterations used 5” aircraft rockets on dozens of four rail launchers.
Later versions used the 5” HVSR. But the penultimate rocket ship was an LMSR with the Mk 102 automatic rocket launcher.
The Mk 102 was derived from the powered twin mount Bofors 40mm. A handling room directly below the mount fed rockets to the launcher. The 8 or 10 launchers on an LMSR were directed from a central gun director on the pilothouse.
The Navy was quite pleased with these ships, and kept them in reserve after World War II. They would see further service, even into the Vietnam war.
These ships were, however, wartime expedients, and suffered from some compromises that the Navy sought to overcome. For one thing, their magazines were above the waterline, and thus terribly vulnerable, as the ships were essentially unarmored. Further, the beaching hull meant that their top speed was quite limited. Of course, with a fleet of dozens of newly built LSMRs in reserve, and the war over, there simply wasn’t any money to design a better ship. But the Korean War changed that, making money quite available for a prototype. Laid down in 1952, the ultimate rocket ship wouldn’t be finished in time for that war. But the USS Carronade (IFS-1) would go on to serve in Vietnam for nearly four years. Armed with the slightly improved Mk 105 automatic rocket launcher, she and a handful of recommissioned LSMRs would provide call-fires and pre-planned fire support
Of course, no discussion on naval barrage rocketry would be complete without at least a passing mention of our national anthem. The Star Spangled Banner’s line about “…the rocket’s red glare…” refers to the Congreve rocket, used by the Royal Navy during its bombardment of Ft. McHenry.