Polaris B-3 Studies
During the 1962-1964 period strategic analysts postulated the Soviet defense would have an improved discrimination (radar) capability and a greater defense in depth with "SPRINT" type interceptors by the post-1967 period. Various advanced POLARIS preliminary design concepts were studied by LMSC to offset the perceived Soviet threat. In October 1962, the POLARIS A3a was offered. It was a 66 in. diameter missile versus the prior 54 in. missiles. Concepts included a large single warhead, a three-warhead system, and penetration system options compatible with the missile system's desired maximum range.
This was followed by various POLARIS B3 missile concepts. Various reentry system configurations were evaluated (e.g., a single warhead, a cluster of multiple warheads, an aerodynamic maneuvering warhead, a low-altitude terminal dash). These configurations were code-named B3D, B3H, B3E, etc. Finally in July 1963, Lockheed proposed a POLARIS B3D to counter the expected (1969 to 1970) increased defense against ballistic missiles. The POLARIS missile diameter would increase to 74 in. The SSBN launcher's inner tube sized for a 54 in. diameter missile would be removed and non-launchable seals (pads) would be installed directly to the outer tube to accommodate the B3D's 74 in. diameter. The missile range would be in the order of 2000 nm and it would have a three-warhead system along with Pen-Aids (PX). Deployment of the warheads and PX would be from a platform with a cold gas (nitrogen) control system for reentry system altitude control. This was the beginning of what later became a "Bus" for reentry deployment/targeting. The system as proposed had hard target effectiveness plus improved penetration capability and versatility against defended urban/industrial targets.
During this same time frame, the Air Force generated (1962) a requirement for a new reentry vehicle which would become known as the Mk 12. Development of this new payload was authorized in late 1963 with the Director, Defense Research and Engineering proviso that it be a joint Navy-Air Force development. During March 1964, the General Electric Company, Reentry Systems Division, was authorized to develop it for Minuteman and POLARIS.
In May 1964, Lockheed proposed another POLARIS B3 configuration; a 74 in. diameter missile. This would double the volume and weight capability for a reentry system when compared to POLARIS A3. The reentry system would consist of six Mk 12 type warheads plus Pen-Aids. The range would be 2000 nm. At this time, anti-submarine warfare (ASW) projections and forward-based tender support did not warrant a further increase in missile range. Investigations of the performance potential, therefore, focused on increased payload flexibility and improved defense penetration.
Guidance and controls were within the reentry system deployment platform with a warm gas reaction system for attitude control. The "Bus" had arrived it was called the "Mailman" concept. There were other new design concepts for the B3 (e.g., first and second stage glass filament wound motor cases with thrust termination on the second stage forward-facing thrust ports). Each motor had a single nozzle with fluid injection for TVC.
Later in October 1964, after conducting a B3 targeting study, Lockheed proposed a concept which extended the operation and flexibility of the "Mailman" concept by the use of modification kits for the deployment platform. The kits provided for changing six Mk 12's to four Mk 12's or twelve (new) small reentry vehicles and interchanging warm gas generators of the platform's attitude control system. This would vary the available energy source and provide single or multiple-targeting. This concept was "Flexi-flier."
Also during this 1964 time frame, Lockheed conducted a Large Ballistic Missile (LBM) study. With accuracy improvement forecasted for the Soviet ICBM system, the U.S. ICBM system's survivability came under question. Lockheed proposed a large two-stage, solid-propellant missile weighing approximately 602,000 lb with a range of 5,500 nm with multiple-reentry vehicles using advanced large payloads. The LBM would involve sea-basing, encapsulated in ocean depths down to 8000 ft. The Mk 17 RB, another Air Force-Navy potential development program, briefly came under consideration.
The Navy's role in strategic weapon systems was assigned to the urban/industrial targets, and the LBM concept was dropped. The proposed POLARIS B3 with Mk 12 RBs was primarily identified as a single-target weapon. Incorporating a multiple-target capability, with a large number of smaller RBs (a new Navy Mk 3 RB) resulted in vastly improved cost-effectiveness (low cost per target). This led to a designation change, B3 to C3.
The multiple-target capability was achieved by the use of a number of smaller RBs and the "Flexi-flier" concept (e.g., the equipment section acts as a "bus"). It has a gas generator, thruster valves and a control system which, after separating from the missile's booster system (rocket motors), provides an added velocity increment and maneuverability in space to position and separate RBs to separate independent targets. This Multiple Independently-targeted Reentry Vehicle (MIRV) capability provides the ability to deliver multiple RVs to a single target or to multiple targets. The impact of multiple RVs attacking more than one target from a single missile is described as the missile footprint. The RVs can be laid down in a downrange stick, a crossrange stick, or a combination of both. A single target attack with multiple RVs from a single missile poses a special design consideration. To prevent multiple RV kill by a single interceptor, the RVs must be spaced along the trajectory so that the distance between any two RVs at intercept, altitude is greater than the (statistical) lethal diameter of the interceptor. Interceptor lethal diameter is determined primarily by the RB hardness and the assumed conservative interceptor warhead yield.
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