Foreign Relations of the United States, 1977–1980, Volume IV, National Security Policy

173. Memorandum From Victor Utgoff of the National Security Council Staff to the President’s Assistant for National Security Affairs (Brzezinski)¹

Washington, February 8, 1980

SUBJECT

• M–X Basing Vulnerability

In response to your question as to which is less vulnerable—the racetrack or multiple holes—I think the sheltered road mobile basing system is less vulnerable overall, because it can be made as resistant to nuclear attacks as the multiple holes system, but is far less vulnerable to loss of missile location security.

Making the horizontal shelters of the road mobile system as resistant to nuclear attack as the vertical holes does cost more for several reasons.

First, the portions of any shelter that are exposed to the over-pressures produced by a nuclear blast must be particularly strong, and much more area is exposed to blast overpressure by the horizontal shelter.

Second, the suspension system used to isolate the missile from the ground motion associated with the blast is more complex for the horizontal shelter, and more “rattle space” is required—resulting in a bigger shelter.

The purpose of hardening the MX shelters is to make sure the Soviets would not find it advantageous to go to warhead placements and yields that would allow them to kill more than one shelter with a single weapon. Given this purpose, we have the choice of building somewhat softer shelters if we space them farther apart. In fact, at this point it appears that minimizing the cost of achieving an equally survivable MX basing system using horizontal shelters will mean going to somewhat softer but more widely spaced shelters than we would have used had we elected to go with the multiple hole system.²

1. Source: Carter Library, National Security Affairs, Brzezinski Material, Subject File, Box 43, Missiles: 10/79–3/80. Unclassified. Sent for information. Sent through Welch. A stamped notation indicates Brzezinski saw the memorandum.
2. Attached but not printed is a January 28 Evening Report from the NSC Defense Policy Coordination Cluster to Brzezinski. Next to the section on the M–X missile, Brzezinski wrote: “Which is less vulnerable: the ‘race track’ or the multiple holes?”