Don't overestimate those Soviet subs

The episode of a grounded Soviet submarine near a Swedish naval base has raised questions about Soviet intentions in Scandinavia and about prospects for nuclear arms control in Europe.

The Soviet submarine that was temporarily in the custody of the Swedish government is a diesel/electric boat of the ''Whiskey'' class. To clarify the role of this boat, it is useful to start with some background information on modern submarines. Military submarines generally fall into three classes: ballistic-missile equipped (SSB); other guided-missile equipped (SSG), usually anti-ship; and torpedo-equipped (SS). The latter are designed to hunt and destroy either surface ships (if equipped with antiship torpedos) or other submarines (if equipped with antisub torpedos).

A further designation, N, is given if a sub is propelled by a nuclear power plant (SSBN, SSGN, and SSN). Nonnuclear-powered submarines are driven by diesel engines with backup electric batteries for use when deeply submerged. Diesel/electric submarines cannot remain deeply submerged for weeks on end, as can nuclear-powered submarines. They are therefore useful mainly for operations near the home coast.

The ''Whiskey'' class was the first medium-sized SS built by the USSR after World War II. Today the USSR maintains a fleet of about 160 SSs of which about 30 to 50 are of this class. By comparison, the United States maintains only three old SS-class submarines, the rest of the US fleet being nuclear-powered and therefore more suitable to global operations.

The old ''Whiskey'' submarines are believed to be used by the Soviet Navy for training, intelligence-gathering, and bearing radars. Because of their limited range of operation, these subs do not constitute a threat to US ballistic-missile submarines, which are deployed in the deep-ocean basins of the Atlantic and Pacific.

The Baltic Sea is almost an inland lake. It is bordered to the east by the USSR, to the south by Poland, East Germany, and West Germany, to the west by Denmark and Norway, and to the north by Sweden and Finland. The only passage to the North Atlantic is through a narrow strait between Denmark's Jutland Peninsula and the Scandinavian Peninsula. Because of the obvious constraints of this geography, the Soviet Union does not deploy in the Baltic any of its strategically-important SSBNs.

The total active Soviet submarine deployment in the Baltic is: 6 ''Golf II''-class SSBs, each carrying 3 ballistic missiles, probably of the SS-N-5 type; 2 SSGs; and 20 SSs, including some of the ''Whiskey'' class.

The missiles aboard the ''Golf II'' SSBs are of an older design with a range of around 700 nautical miles. Newer strategic missiles have a range of 4,000 nautical miles. Because of this range limitation, the missiles aboard ''Golf II'' submarines can only be aimed against the European targets immediately surrounding the Baltic Sea. In strategic terms, these 18 or so missiles (only a fraction of which are at sea at any given time) represent a very small missile force, although this fact is little consolation to anyone living near one of these targets.

From all indications, the stranded submarine's mission was probably intelligence-gathering of some kind. The Swedish government was perfectly within its rights to demand a full explanation for a flagrant violation of recognized restricted territorial waters. To keep the matter in perspective, however, it should be remembered that many counties gather intelligence from within restricted areas of their opponents.

The interception of a Soviet intelligence-gathering vessel by a Scandinavian country which is not a NATO member should not be allowed to hamper negotiations for either a Nordic Nuclear-Free Zone or reductions of long-range theater nuclear forces by NATO and the Warsaw Pact. The grounding of a 25-year-old submarine that was (probably) spying is a much less urgent issue than the buildup of the large nuclear weapon systems which threaten the populations of Europe and the Soviet Union.

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