Washington — The kind of shoot-or-get-shot-at pressure that triggered American obliteration of an Iranian civilian airliner in the Gulf is precisely what arms controllers are trying to avoid in the apocalyptic world of nuclear weapons. That kind of panic is known as ``crisis instability.'' It exists on the strategic nuclear level when the superpowers' best weapons are not only powerful, but also vulnerable - as they are now - and therefore confront national leaders with a ``use 'em or lose 'em'' situation in a crisis.
In such a situation - like that faced by Capt. Will C. Rogers III of the ultra high-tech but vulnerable Vincennes - the leader with his finger on the button, fearing that an attack could destroy his best weapons, might press his own button first.
And, like the Vincennes commander, he might find out too late that what he took to be an electronic signal of attack was really something quite different.
To avert that kind of tragic miscalculation, the negotiators at the Strategic Arms Reductions Talks (START) are trying hard to make both superpowers' weapons less vulnerable. That way, nuclear weapons could ride out a false alarm, or even an initial attack and still be available for a response if needed - and therefore ``deter'' that attack in the first place.
This sobering stalemate is known as the nuclear ``balance of terror.''
To pursue the Gulf analogy, if the Vincennes were able to survive a missile fired from what it thought was a fighter plane, it could have waited the extra minute to ascertain that there was in fact no threat. Catastrophe could have been averted.
The Gulf tragedy illustrates why one senior Pentagon official speaks so approvingly of the kind of rejigging of the Soviets' strategic ``force structure'' or mix of weapons that would be required under START. ``Let me be candid. What have we achieved?'' he asked. ``It's easier for us to restructure Soviet forces if we reduce'' the total numbers of strategic weapons, he declared.
The START draft accomplishes this, he stressed, and even adds ``incentives for them to continue'' restructuring in the direction of a safer world. His point was that the much heralded 50-percent strategic cuts called for in the draft treaty are only a means, not an end.
The end is to increase ``stability'' - to reduce the ``use 'em or lose 'em'' incentives to either side to launch a Vincennes-type ``preemptive'' strike in a crisis out of fear that the other side is itself about to strike.
START would perfect this, negotiators say, by reducing the hair-trigger vulnerability of strategic weapons - that is, by increasing their ``survivability'' and therefore the time a leader has to evaluate a threat before pressing the button.
To this end, a START treaty would cut the number of highly accurate Soviet warheads per US ``hard targets'' (and the number of accurate US warheads per Soviet cement-hardened targets) below the 2:1 ratio needed to ensure destruction.
The START treaty would also encourage both Moscow and Washington to shift away from their most powerful and vulnerable weapons - fixed, silo-based intercontinental ballistic missiles (ICBMs) - toward less volatile systems, such as submarine-based, bomber-mounted, and mobile land-based missiles.
Fixed land-based systems are the most volatile strategic weapons because they are extremely threatening - with up to 10 warheads on a single missile - but, like the Vincennes, vulnerable.
The vulnerability of any fixed (as distinct from mobile) basing mode arises from the new, increased accuracy of warheads in hitting any known geographical position.
In this context, the present Soviet deployments have made the United States especially nervous (and precipitated concern in the early Reagan administration about a ``window of vulnerability'') since some 58 percent of Soviet strategic warheads are now based on land in ``use 'em or lose 'em'' silos, according to the International Institute of Strategic Studies.
By contrast, only 16 percent of US warheads are based in fixed silos.
The START Treaty is therefore deliberately weighted to compel the Soviet Union to rectify this trigger-happy distribution, both by reducing the number of multiple warheads per missile - the Soviets would have to drop from their present 11,044 total warheads on 2,511 missiles to 6,000 warheads on 1,600 missiles - and especially by requiring a 50 percent cut in Moscow's unique ``heavy'' SS-18 missiles with 10 warheads each, down from today's 308 launchers and 3,080 warheads to 154 launchers and 1,540 warheads.
The net effect (depending on how the US deploys its own post-START strategic missiles) could be to reduce the current high ratio of accurate Soviet warheads to American ICBMs and force Moscow down to less than the crucial 2:1.
Under the 3,300 ``sublimit'' on ICBMs proposed by the United States, explains Mark Schneider, Director of Strategic Arms Control Policy in the Defense Department, the Soviet Union ``could not do double targeting.''
At present, by contrast they have enough accurate warheads for ``two-on-one targeting [that] can get 80 percent of US ICBMs.''
Robert G. Joseph, Deputy Assistant Secretary of Defense for Nuclear Forces and Arms Control Policy, adds that the United States has insisted in the START counting rules on penalizing the kind of vulnerable and threatening fast-flyers like ICBMs that require instant decisions and increase the risk of miscalculation.
This, he says, ``has the same effect of putting a greater emphasis on more stable systems that are less vulnerable, as compared with silo-based [ICBMs].''
If START is finally agreed on and compels Soviet restructuring toward more survivable systems Moscow would no longer have any incentive for a preemptive strike even in a crisis: any Soviet ``first strike'' would be foolish since it could not wipe out America's best weapons as at present, but would act only as a bee sting to trigger retaliation by the surviving American weapons.