START: No Stop to New Arms

The Strategic Arms Reduction Treaty will not require the United States and Soviet Union to halt research on new weapons. Research continues in both countries on making fewer weapons that scientists say are more powerful and more difficult to detect. Among them:

Earth-Penetrating Weapon: Nuclear warheads dropped from planes or loaded onto missiles would burrow into the ground and explode. Originally targeted against hardened underground bunkers, it now would be used against missile silos or submarines. In tests, the warhead has exploded 3 feet to 13 feet below ground.

Maneuvering Re-entry Vehicle: Missiles carrying warheads would use guidance systems to accurately find targets rather than being pulled by force of gravity. MaRVs have had only limited testing.

Hypersonic glide vehicle: A high-speed warhead that would be boosted up on a rocket and glide toward its target through the Earth’s upper atmosphere. It avoids detection by antiballistic missile radars. The device could maneuver and swerve, swooping down on ships or missiles.

Microwave weapon: A third-generation nuclear weapon, it focuses a cone of energy released by a hydrogen bomb explosion over a battlefield. The energy creates interference with electrical systems and command and control centers, but limits damage to a specific area.

Nuclear shotgun: Firing pellets from tubes, it is designed for use in space to distinguish between real warheads and decoys.

Particle beam weapon: It would take a beam of electrons or protons and fire them at a target.

Small ICBM: Nicknamed Midgetman, this intercontinental ballistic missile is scheduled for deployment after 1997. It could be made mobile by deployment on trucks or rail cars.

Advanced cruise missile: The new generation of cruise missiles is stealthier than the current air-launched cruise missile. The Air Force plans to buy 1,000. A new version is in the planning.

X-ray lasers: A nuclear blast pumps killer laser beams. One more test for this weapon is planned for 1992 or 1993, after which it will be shelved. The weapon is designed to be deployed in space, part of the Star Wars defense system against ballistic missile attack. But all space-based offensive weapons are banned under the 1972 U.S.-Soviet ABM Treaty.