Exploring the High-Tech Frontier

• Share

(6 of 9)

KINETIC-ENERGY WEAPONS. They are simply objects like rockets, homing vehicles or even pellets fired at a missile, bus or warhead to destroy it by sheer impact. They are potentially effective at any stage from boost to re-entry, and can be fired either from the ground or from space. Their technology is well enough developed to make them available by the 1990s, much earlier than any of the beam weapons. Indeed, a terminal defense of sorts could be put into place right now. Main drawbacks: the range of kinetic-energy weapons is measured in hundreds rather than thousands of miles, and the top speed researchers are trying to reach for any projectile is about 25 miles per second. By laser or even particle-beam standards, that is slow, slow, slow.

Boost-phase interception would be carried out by low-orbit satellites firing rockets out of pods. A rocket would accelerate to the vicinity of a rising missile, then release a homing vehicle that would be guided by sensors and thrusters to a head-on collision with the missile. But as many as 20,000 rockets orbiting aboard many hundreds of satellites might be required to keep enough within range of Soviet launch sites at all times to fend off a full- scale missile onslaught.

For mid-course interception, batteries of ground-based rockets might be fired into the upper atmosphere. Each rocket would release a swarm of so- called smart rocks--vehicles powered by little thrusters and guided by tiny sensors--to hit warheads and decoys in space. An alternative is to fire the smart rocks out of devices called rail guns placed in orbit. The rail guns use a burst of electric current to accelerate the smart rocks along a rail. One problem is sheer numbers: immense swarms of smart rocks would be needed to hit warheads and decoys indiscriminately. The other option, picking out the warheads from the decoys, would require rocks that were not just smart but intellectual giants. They would have to be guided by tiny sensors sophisticated beyond any yet developed.

Terminal defense is easiest, technologically. Warheads, heated and slowed by friction with the atmosphere on re-entry to speeds of about two miles per second, could be tracked by airborne or even ground-based radar. They could be hit by interceptor rockets or pellets discharged by fragmentation bombs. But enough missiles would have to be destroyed in boost, and enough warheads in post-boost phase or mid-course, to keep the terminal defense from being overwhelmed. And then there is the problem of hitting the warheads high enough to minimize the effect of blast, fire and radiation on the ground.

The different technologies eventually would probably be used in combination. But, of course, the systems will develop at different speeds, assuming all or any prove feasible. Air Force Lieut. General James Abrahamson, who heads the Pentagon Strategic Defense Initiative Office, foresees a three-stage development: initial deployment of a "robust" defense, presumably relying mainly on kinetic-energy devices, to be started only if and when R. and D. indicates that a second and then a third generation of more sophisticated weapons will follow in not too many years.