Foreign Relations of the United States, 1981–1988, Volume XLIV, Part 1, National Security Policy, 1985–1988

23. Memorandum From the Special Assistant to the Under Secretary of State for Political Affairs (Courtney) to the Special Advisor to the President and Secretary of State on Arms Control Matters (Nitze)¹

Washington, undated

SUBJECT

• TRW Briefings on Superhardening, SICBM, and SDI

Following are my notes on the February 28 briefings at TRW in Los Angeles.

Superhardening

MX. [5½ lines not declassified]

The MX in a Minuteman (MM) silo will have the same rattlespace on the side and top-to-bottom as the smaller MM missile, because the MM cage is absent.

Ten launch control centers (LCCs) will control 100 MX missiles, as compared with MM, for which 5 LCCs control 50 missiles. The 10/100 arrangement is a better hedge against an SLBM attack.

In 1983 the President approved an MX program costing $16.6 billion (in 1982 dollars). The estimated actual cost at present is a shade lower, $16.5 billion.

Superhardening. Following is the silo damage radius for each of several silo hardnesses, assuming a one megaton burst:

Type of Silo	Hardness (psi)	Silo Damage Radius
MM	[column not declassified]	[column not declassified]
Superhard
Enhanced superhard

A useful measure of the value of alternative levels of hardening, in relation to warhead accuracies, is the “attack price,” the number of SS–18 equivalent missiles (assuming ten warheads per missile) required to attack and damage a silo with 90% confidence. The following chart summarizes the attack price estimates for varying levels of hardness and missile CEP.

	[column header not declassified]
CEP	[number not declassified]	[number not declassified]	[number not declassified]
450′	0.1	0.6	0.9
300′	0.1	0.3	0.4
200′	0.1	0.1	0.2

Thus, for example, for an SS–18 having a CEP of 450′, only one RV would be needed to destroy an existing silo with 90% confidence, but nine RVs would be required to damage an enhanced superhard silo with 90% confidence. The estimates in the table above exclude any survivability gains that would accrue from fratricide caused by closely spaced basing of silos. Calculations of fratricide effects for superhard silos arrayed in CSB will be completed in 6–9 months. (Comment: These will be the interesting calculations: if they show strong symbiosis between CSB and superhardening, it may be useful to reevaluate the concepts for SICBM basing, and indeed the marginal utility of the deploying SICBM versus more MX.

Past DNA estimates of crater size (never measured precisely in the past because potential hardness increases were not expected), so new estimates are being undertaken. A one megaton detonation might create a crater having a lip hard to 200–300,000 psi.

Superhard silos should be located in dry soil, but not rock or wet soil. Dry soil craters are smaller than wet soil craters. Craters in rock would be even smaller, but seismologists think rock would shear, destroying the silo. This hypothesis cannot be tested without using nuclear detonations, but scientists believe it is valid.

In small-scale tests engineers are trying to figure out where to put the steel. Radial steel appears to be better than hoop steel. Tests of the 24′ scale silo model had a 7–8% steel content.

Tests show that motions and stresses on a silo from a second detonation are less than those from the first, because the first one compacts the earth around the silo. But to compact earth as a construction technique in building silos would be too expensive.

Silos built at ground level tend to be pushed partially out of the ground by the first shot, thus making them vulnerable to a second. But this can be solved by building silos slightly underground, which will also help protect them against thermal and radiation effects.

The problem of source regioning EMP effects is also being examined.

Superhard silos are doing well in tests against motion effects. The MX is capable of withstanding [less than 1 line not declassified], and the SICBM can be designed without much difficulty to withstand [less than 1 line not declassified]. While fiber optic communications is adequate for peacetime communications with silos, antennae will be needed for wartime launch from airplanes and mobile LCCs.

Missile egress is a problem from surface bursts. Recently a successful test took place in which a multistage actuator pushed up a sleeve through debris, enabling the gas-driven cannister to surface into launch position.

SICBM

Gorman said the Scowcroft Commission timetable is what paces the SICBM program, not technology. If the MX were defeated today, an SICBM with modified AIRS guidance could be ready in about four-and- one-half years. But the current SICBM program has decelerators built into it. If the SICBM had to meet only the specifications of the Trident C–4 missile, it could be built for 25–30% less cost, but this wouldn’t be salable. At present the Air Force is looking at a stellar inertial and two ring laser guidance systems as possibilities for the SICBM. Guidance is one-half the cost of the SICBM.

A mobile launcher hardened to 30–50 psi deployed in an area of 2.5–4.0 sq. mi. would exact an attack price of one SS–18 warhead. A soft truck hardened to three psi deployed over an area of 100 sq. mi. would exact the same attack price. We learned from the MX experience that we cannot get public lands, or military bases being used for something else, as basing locales for a new ICBM.

A hard mobile SICBM, mounted on a vehicle capable of doing 30 mi/hr and based along a 1,000 mile perimeter enclosing a square could move up to 4 miles inside the perimeter to protect against a short-warning SLBM attack. This potential deployment area of 4,000 sq. mi. could be doubled if missiles could move either inside or outside the perimeter.

Cost Comparisons for Missiles and Basing Modes

Assuming that $16 billion has already been spent on the MX program, following are incremental costs (1982 dollars) for alternative 1989 basing options for both MX and SICBM:

Missile/Basing Mode	Incremental Cost
100 MX/100 Super/CSB	$16 billion
100 MX/100 Super/MM	16
100 MX/500 Super	30
500 SICBM/500 Super/CSB	49
450 SICBM/450 Super/MM II	44
500 SICBM/Hard Mobile	44
500 SICBM/Continuous Road Mobile	43

Procurement of an additional 100 MX missiles, beyond the first 100, would cost $3 billion (excluding basing costs).

The incremental cost for construction alone of 100 superhardened silos is about $35 million per silo, but total incremental cost (including, for example, electronics and communications hookup) is $150–200 million per silo.

The cost of an SICBM is one-half the cost of an MX, making the cost per warhead of the SICBM five times greater than for the MX.

SDI

Technologies. SDI requires advances in a number of technologies: microelectronics, advanced computers and netting, advanced radars and optical sensors, improved discrimination techniques, non-nuclear kill mechanisms, directed energy weapons, and improved space launch capabilities. Non-nuclear kill mechanisms are desirable both for political reasons and because they do not disrupt the battlefield environment.

Discrimination. Below 300,000 feet the Army has responsibility, and it has made a lot of progress. We have reasonable confidence also for boost phase discrimination technologies. In the last ten years, great gains have been made in optical sensors, especially for the terminal phase. We are now collecting optical data at Kwajalein on all missile flights.

Astrodome Defenses. What “miracles” are needed for us to be able to deploy an astrodome defense?

○ [less than 1 line not declassified] a feat especially difficult for kinetic energy weapons;

○ [less than 1 line not declassified] a difficult task, but one perhaps not so difficult as some believe since we [less than 1 line not declassified]

○ low-leakage mid-course discrimination (we have little data on mid-course flight, and almost none on false targets in mid-course).

[1 paragraph (9 lines) not declassified]

We need an aggressive program to collect data for SDI research, [1 line not declassified]

It will be hard to develop lasers for target kill.

Deployment of sensors for SDI could, by itself, enhance deterrence. For example, non-continuously mobile ICBMs need warning to be survivable.

[1 paragraph (4 lines) not declassified]

The nearest-term SDI layers are terminal and midcourse technologies being developed by the Army. It is quickest to deploy SDI “from the ground up.”

The concept of ground-based, blue-green lasers using mirrors in space is being considered for communications with submerged submarines.

The SDIO very much wants to keep the SDI program focused on long-term research, and not on a specific mission. But a very modest defense could be valuable against a highly-stylized Soviet attack.

At the end of the session, John Foster made a case for hard target terminal defense. He commented also that the U.S. may need a nuclear system in order to get an effective defense.

1. Source: Department of State, Ambassador Nitze’s Personal Files 1953, 1972–1989, Lot 90D397, March and April 1985. Secret. Copies were sent to Timbie and John Gordon (PM). A handwritten note at the bottom of the first page of the memorandum indicates that copies were also sent to Burt, Adelman, and Chain on March 28.