In October 1965, inspired by the success of Hughes' new towed-array passive sonar, LRO suggested a low-cost ocean reconnaissance ship (PR) built specifically for the surveillance and control of surface traffic.⁸ It would also be useful for augmenting convoy escorts and performing local ASW surveillance. It would need a light helicopter for surface surveillance; the same helicopter supplemented by lightweight torpedo tubes would suffice for ASW attack. LRO hoped to build reconnaissance ships in FY70-72.
Preliminary Design offered Scheme A(see table 12-5). It would be powered by two diesels geared to one shaft for cruising economically over a wide range of speeds up to 16 knots. Armament would consist of one lightw 3-inch/50 (a projected gun, controlled by a new Mark 87 director), two 0.50-caliber machine guns, two Mark 32 triple torpedo tubes (six torpedoes), and a six-round anti-ship missile launcher (eighteen surface-to-surface and twenty point-defense missiles; this was space and weight reservation only, since no missile had as yet been chosen). The Mark 87 director would double as an air-search radar, and the major surveillance sensor was a towed array backed up by an active, short-range, hull-mounted SQS-36 sonar. Stowage and maintenance were provided for a lightweight helicopter as well as starting and fueling space for a UH-2A. There would be sixty sonobuoys a d six helicopter-launched torpedoes. The projected complement was 10 officers and 150 enlisted men.
The design was austere with now margins for future growth. Still LRO considered it too large, suggesting that a regenerative gas turbine might save space and that joint weapons-handling and stowage might save space and manning. In February, LRO proposed the elimination of surface-to-surface missiles, and as compensation, the substitution of a lightweight 5-inch/54 for the proposed 3-inch/50. The BPDMS (Basic Point-Defense Missile System), using Sea Sparrow, would be retained with an eight-missile box launcher plus twelve reloads.
LRO also wanted alternative powerplants explored, for maximum speed of 20 to 22 or 25 to 27 knots at eight hours in addition to the desired basic endurance. Such burst speed would enable either an all-gas-turbine plant or at least a gas-turbine boost plant. Endurance speed would be at least 16 knots, with a long range of 9,000 nautical miles at 12 knots.
LRO listed draft characteristics in April 1966. The mission of the PR would be to assist in patrol, surveillance and control of ocean and coastal areas, and to conduct special reconnaissance missions. Operating individually, the PR would go on extended ocean patrols, but it would also have to be able to enter restricted waters and minor ports throughout the world. Individually or in conjunction with aircraft and additional ships, it would trail merchant and other craft and, if necessary, visits and search them. It would there for assist in blockade or quarantine.
The PR was not a pure patrol ship. LRO wanted it to be able to deal with anything smaller than a destroyer and even to control and support small surface ASW craft. As a result, the PR was close to a frigate in size and capability.
This resemblance was emphasized by analysis of the role of the towed-array ship in convoy protection. In the July, the PF (Patrol Frigate) designator, then being applied to small frigates built for Iran and Thailand under MAP, was applied to the towed-array ship. Design requirements now included SEAL support, increasingly important in Vietnam. Characteristics changed to show 100 rocket-assisted rounds out of 400 for the 5-inch, and the Mark 32 tubes were reduced to fixed twins, as in the contemporary Knox-class frigates, with eight reloads. The reloads could also be used by the helicopter. Required performance was altered to a sustained speed of 18 knots with the array streamed. Oddly, the desired endurance (with the array streamed) of 4,500 nautical miles at 16 knots did not quite correspond with that required of other US warships. Machinery was to be arranged to permit economical at 5 to 10 knots.
The patrol craft ancestry of the project was revealed in the requirement that the helicopter hangar be adaptable for use by beach jumpers, SEALs, or UDTs.
Table 12-5 list several attempts to reduce the size of the ship. In Scheme B, reserved space for surface-to-surface missiles was eliminated. In Scheme C, one diesel was replaced with a 25,000shp simple-cycle has turbine to provide a high short-term speed. One propeller shaft had to be added because otherwise tandem propellers might be needed to absorb the plant's considerable power. Scheme D employed four regenerative gas turbines for greater endurance. Finally Scheme E of early 1967 had a single gas turbine, which showed poor fuel economy at 12 knots. All of the gas-turbine designs indicated a prominent air intake atop the bridge.
Preliminary Design preferred Scheme C and presented a developed version in March 1967. It was armed with one lightweight 5-inch/54, a BPDMS launcher, aft, with twenty missiles, tow 0.50-caliber machine guns, and two twin Mark 32 torpedo launchers with twelve torpedoes; the boat would carry two 6,000-pound helicopters and be able to launch and land the UH-2A. It was also anything but LRO's small cheap super-Swift, and it died.
8. Hughes proposed a towed ocean surveillance array in February 1962. It's WQR-1 (XN-1) was tested off Hawaii on 30 May 1965, towed by the fleet tug Hitchiti (ATF-103) at up to 14 knots. It successfully detected a snorkeling submarine at one convergence zone and a surfaced submarine at an even greater range. Hughes promised ranges as great as 30 nautical miles at tow speeds of about 10 knots, and the array could be towed at up to 20 knots. This work ultimately led to some of the current tactical and surveillance arrays, such as those installed in the towed-array ocean surveillance ships (T-AGOS).
