Amid the recent discussion of SALT and the Soviet-American military balance, an important yet hardly mentioned development in the field of navigation may well have a major impact by the late 1980s on the strategic balance as well as on arms control efforts.
This new development, called NAVSTAR, is the US government program to provide accurate worldwide navigation to an unlimited number of users -- both civil and military -- via a constellation of 18 space satellites. Orbiting the earth at an altitude of about 12,000 miles, these satellites will regularly broadcast information on the time and their locations; by receiving and decoding the signals from any four of these 18, the user will be able to determine his location and velocity.
In contrast with all present navigational aids, NAVSTAR can be utilized anywhere on the globe -- on all continents, on all seas, in the air, and even in space. The expected accuracy for military use is about 50 feet in position and a tenth of a foot per second in velocity. With project completion by 1987, there will be numerous commercial and military applications for such worldwide positioning, including all civil air and sea navigation, air traffic control, military bombing missions, and missile guidance. This last application is certain to have important implications for the strategic military balance between the United States and the Soviet Union.
Since their first deployment 20 years ago, rockets that carry nuclear warheads have improved greatly in performance and accuracy. Within 30 minutes after receipt of the launch command, a modern long-range missile can deliver to intercontinental range its nuclear payload, striking three or six or ten targets spread out at distances of 100 miles apart, with an expected accuracy of about 200 yards. Such multiwarhead missiles are deployed by both the United States and the Soviet Union on land (intercontinental ballistic missile, ICBM), and at sea on submarines (submarine-launched ballistic missile, SLBM).
At present, submarine missiles are less than half as accurate as their land-based counterparts because of errors in initial position and velocity. However, missiles deployed on submarine can be hidden from the adversary in the vast oceans, as contrasted with the necessity of protecting the ICBM at known and fixed locations from the blast of a nuclear attack.
As long as the incoming weapon does not detonate too close to the concrete silo that houses the missile, the ICBM is secure. This ICBM protection is now being challenged by the increasingly accurate land-based missiles; it is very difficult to offer blast protection from a megaton-range warhead with 200-yard accuracy.
For a missile aided by NAVSTAR navigation during the first few minutes of flight, accuracy could improve significantly, to better than 100 yards. Moreover, in contrast with present inertial guidance, this improvement would be equally available to mobile sea-based as well as to land-based missiles.
NAVSTAR thus enters the picture in two ways. First, such a system will hasten the day of assured silo vulnerability, even to small warheads. Second, the US could gain an early and important capability -- a sea-based (and largely invulnerable) countersilo capability -- of great concern to the Soviet Union, particularly since the USSR bases a far greater fraction of its nuclear force on land than does the US.
This may reinforce present trends toward land-mobile ICBMs -- a deployment which may make more difficult the task of arms-control monitoring. Or the effect may be to hasten the process of both countries to move their nuclear forces to the relative safety of the sea -- a region where the US currently possesses a technological lead in detecting other submarines.
While the US now maintains a strong lead in NAVSTAR-related technology, the same capability should eventually be within the reach of the Soviet Union. This greater reliance on space systems, along with the inevitable advances in antisatellite warfare, will mark the expansion of the military battleground to space.