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Just as project NOBSKA in 1956 "steered" the U.S. Navy to a new generation of smaller solid-propellant POLARIS-type FBMs, so too STRAT-X/ULMS-I steered" the Navy to the next generation SSBN/FBM system. SECDEF Robert McNamara, on 1 November 1966, initiated a comprehensive study on U.S. ballistic missile performance characteristics required to counter potential Soviet strategic offensive forces and anti-ballistic missile proliferation in the time frame 1975 to 1985 - 90.

The study was conducted under the auspices of the Research and Engineering Support Division of IDA. The study was known as STRAT-X (for Strategic eXperimental). Based on a previous study done by the IDA earlier that year called PEN-X (for "penetration of enemy missiles, experimental"), the deliberately-nebulous title was concocted to prevent bias in the study toward any land-, sea-, or air-based system. Posting the likelihood that the Russians would deploy, in the future, extremely-powerful and highly-accurate ICBMs as well as an effective anti-ballistic missile system, McNamara's study requested appropriate countermeasures. The STRAT-X study was headed by General Maxwell Taylor, President of IDA. The "working" study group was headed by Fred Payne of IDA.

The "working" panel included executives from several major defense contractors and independent corporations. The Advisory Committee were mostly military men. RADM George H. Miller (OPNAV) and RADM Levering Smith, (SP-00)the Navy contingent on the STRAT-X panel, "representing both the [Naval Operations] staff and the 'hardware' side of the Navy"- participated, but Naval Reactors Branch, which furnished the nuclear power plans for all nuclear-powered Navy vessels, did not.

Candidate STRAT-X system concepts were evaluated for: (Primary) the ability to retaliate against a Soviet urban-industrial target and (Secondary) flexibility to perform selected counterforce and controlled-response missions.

STRAT-X investigated and reviewed over 125 different missile-basing systems for the purpose of finding the most efficient and survivable option, the only prerequisite being that the candidate system had to be unique in comparison with previous or existing platforms. Going into the study, the Air Force had lobbied for a replacement for the Minuteman ICBM, and it appeared initially as though the Air Force missile might be chosen, but the requirement for new ideas also worked in the Navy's favor.

Other than submitting an improved POSEIDON, the Navy STRAT-X study teams under Dr. Willie Fiedler of Lockheed proposed a different submarine concept called ULMS. After examining these and other alternatives that ranged from the sublime to the ridiculous (such as missile-firing submersibles, ICBMs carried on trucks, surface ships or barges, new bombers, seabed platforms (perhaps located in Hudson Bay)), the STRAT-X panel concluded in 1968 that the Navy's ULMS represented the least costly and most survivable alternative. Miller claimed the panel envisioned a "rather austere" ship with little speed and, consequently, a small nuclear power plant. The Navy supported the view that ULMS was to incorporate very-long-range missiles into submarines of rather conservative design, based on existing submarine technology. The proposed submarine would not necessarily be deep-diving and would carry more than sixteen missiles.

Upon completion of the DoD's STRAT-X Study, the Navy (SPO) continued its own studies of advanced undersea system concepts. Lockheed, General Electric, MIT, Sperry, and Westinghouse were all involved. Electric Boat was funded by Navships for interfacing submarine studies.

Subsequent to STRAT-X, the ULMS effort was continued by SSP at DDRE direction. The cost of concurrently developing a new submarine and missile was judged to be inconsistent with DoD funding and dedication. Since the submarine is the long lead item (seven years from funding to IOC), minimum subsystem changes were dictated for the new submarine.

The submarine design work subsequent to STRAT-X was directed along the encapsulated missile concept as opposed to the FBM concept of bare vertical launch from a fixed mount tube. RADM Levering Smith, PM- 1, stated that the encapsulated missile would be retained only if real merit could be established. Electric Boat was requested by CAPT Gooding (SP-20) to do a submarine feasibility study for both bare vertical and encapsulated stowage and launch of the LRC3 missile. Missile length and first stage diameter are dependent variables. Each concept was allowed to consider dimensions best suited to the stowage mode. The trend for vertical stowage was to make the missile short, and the trend for horizontal encapsulated stowage was to make it long until it hurts. The tradeoffs between launch mode concepts were conducted during CY 1968.

In January 1969, the contractors involved in the stowage mode studies presented their data -- while the ship people favored bare vertical, the missile people favored, and SSPO would recommend the traditional FBM bare vertical launch and stowage used on previous Polaris submarines.

Both Electric Boat (Groton, Connecticut) and San Francisco Bay Naval Shipyard (Mare Island (Vallejo), California) were requested to provide ULMS SSBN concepts. By December 1969, the ULMS team at Mare Island had developed three basic hull forms, concentrating their efforts on developing an external launch tube hull.

Two of the Mare Island designs, the "FISHBONE" and " D Frame " concepts, involve advanced pressure hull construction techniques. The FISHBONE concept, in the missile section, is configured to present a non-circular pressure hull. It was conceived to use the inboard half of the missile tube as the primary pressure hull in the missile tube section of the boat. The "D Frame" achieved a similar non-circular missile tube section by using a flat plate technique outboard of the missile tube as one portion of the hydrostatic hull.

The third concept, "TWIN TUBE," was Mare Island's preferred configuration. In this hull form, the missile tubes (located in the water) have port and starboard access tubes running fore and aft that provide access to the fore and aft part of the boat, as well as access to the missile tubes.

Four FBM hull configurations were offered by Electric Boat, one "external" (wet) tube design and three "internal" tube design: single hull, double hull, and oval hull. The three tube abreast oval hull design had a variant configuration, two tube abreast.

There were also studies made of tilting the launch tubes athwartship and/or fore/aft attitude. The athwartship angle was limited to something less than +10 deg from the vertical. The fore and aft angle could be varied quite a bit more (e.g. +90 deg possible but not practical). A 50 deg fore/aft tilt was studied. However there was a general disbelief in any merits of loading and launching on any line that was not in line with gravity (e.g., vertical).

These studies were evaluated and Lockheed issued a report on 9 January 1970. It stated that the FBM Weapon System has always accepted the classic, POLARIS-POSEIDON 2 x 8 columnar, vertically-tubed, missile zero pointing center, battery arrangement. The data indicated no significant advantages, insurmountable problems or even significant sensitivity to various arrangements. This points to the practical position of "why change," when we might, with some assurance, find the unk-unks [unknown unknowns] hidden within some other arrangement. It is these unk-unks that can react with negative synergism to create significant problems.

The report concluded then that the classic FBM battery arrangement should be maintained.

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