Leaving nuclear launch to computers?

The top-ranking Soviet scientist, saying American computers are not the only ones capable of triggering a false nuclear alert, maintains Moscow will be forced into a policy of launch-by-computer should new US missiles be deployed in Western Europe.

Anatoli Alexandrov, the president of the Soviet Academy of Sciences and a member of the Communist Party Central Committee, argued in an interview that this was the ''only way'' of coping with the new missiles' capability to reach Soviet targets more quickly than the existing US strategic force.

Elaborating on an earlier published statement implying Moscow would switch to a policy of automatic ''launch on warning'' of a US missile attack, he said:

''If you're talking about strategic weapons, they reach their target in about 30 minutes. During this time, some sort of decision can be taken. It is difficult, but it can be taken.''

''There could be communication between governments of opposing countries in case of an accident (in a computer report of an offensive launch), and thus one could avoid the introduction of retaliatory weapons.''

But Mr. Alexandrov maintained the new US missiles, earmarked for deployment beginning late next year, would cut flight time to ''about five minutes.'' He said there ''would no longer be sufficient time'' to leave the ordering of a counterstrike to human beings. ''It can be done only automatically'' once a signal of an attack is received, whether the report is ''true or the result of a technical fault.''

Asked whether the Soviet Union, like the US, had experienced an erroneous nuclear alarm due to computer malfunction, he replied: ''All machines, without exception, make mistakes. Sooner or later, they fail.''

Alexandrov said that, with this in mind, ''I think extremely important (President) Leonid Ilyich Brezhnev's proposal for limitation of European missiles. Further deployment constitutes a great threat.''

Alexandrov's contention that the new US Pershing II missile would reach Soviet targets in about five minutes is in keeping with figures mentioned in the official Soviet news media. Western experts, while agreeing the new projectiles would need to travel significantly less time than strategic missiles, cite a figure of about 14 minutes. The Western analysts say Soviet SS-20 nuclear rockets already in place can reach European cities in about the same time.

Talks in Geneva on limiting European-based nuclear forces are so far stalemated, with the Americans arguing the new missile deployment is needed to offset the Soviet SS-20s, while the Soviets say these rockets merely balance existing US and West European nuclear weapons in the European arena.