Potential of LoAD Ballistic Missile Defense System for Protecting the MX Missile System

C-PSAD-81-2: Published: Nov 12, 1980. Publicly Released: Nov 12, 1980.

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Under the Strategic Arms Limitation Talks II Treaty (SALT II), the possibility exists for an increased threat to U.S. land-based intercontinental ballistic missiles (ICBM) by the Soviet Union. To offset additional increases in this threat, the initial MX system could be expanded by deploying more MX missiles and shelters. If the threat continues, the Department of Defense (DOD) could either expand the MX system and defend the existing MX missiles with a ballistic missile defense system. To provide the option for defending U.S. intercontinental ballistic missiles (ICBM), the Army is conducting a preprototype demonstration of a ballistic missile defense system called the low-altitude defense (LoAD) system. The program's goal is to provide the capability for deploying LoAD soon after the preprototype demonstration is completed. Deploying LoAD would require terminating or modifying the Anti-Ballistic Missile Treaty, which sharply limits the United States' and the Soviet Union's development and deployment of ballistic missile defense systems.

The LoAD preprototype demonstration represents a major effort within the Army's ballistic missile defense program. The Army plans to fund LoAD by reducing other ballistic missile defense efforts and increasing its overall ballistic missile defense budget. One LoAD defense unit would be needed for each MX missile to be defended and would include radar, a data processor, and missiles armed with nuclear warheads. The MX basing mode is still uncertain, and basing modes under consideration may affect the LoAD configuration. MX deployment, to begin in 1986, is initially expected to include 200 missiles and 4,600 shelters. LoAD, if it can be developed to operate effectively, appears to be an economical way of assuring the MX survivability against threat levels exceeding constraints of SALT II. The validity of the LoAD cost advantage hinges on two major assumptions: (1) the Army and Air Force's cost estimates for each alternative are credible and (2) LoAD will be developed to operate effectively. However, the LoAD potential cost advantage over MX proliferation is substantial. Assuming a large increase in Soviet reentry vehicles, LoAD could lose its advantage only if its cost increased 167 percent while the MX cost remained constant. The projected threat which the Army is using to design LoAD is less severe than the threat projected in some intelligence assessments. Unless the Army adequately considers the more severe threat indesigning LoAD, it may not be a genuine option for assuring the MX survivability.

Matter for Congressional Consideration

  1. Status: Closed

    Comments: Please call 202/512-6100 for additional information.

    Matter: Congress should evaluate the Army's plans for developing LoAD and determine whether it concurs with the Army's plans for developing LoAD to meet a less severe threat than it may actually face.

Recommendation for Executive Action

  1. Status: Closed

    Comments: Please call 202/512-6100 for additional information.

    Recommendation: The Secretary of Defense should determine whether the assessment of the responsive threat to the LoAD's performance has used appropriate assumptions. GAO believes that the Army used and inappropriate assumption leading to the erroneous conclusion that LoAD would not be adversely affected by the threat.

    Agency Affected: Department of Defense


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