A Soviet spaceship that splashed down in the Indian Ocean yesterday after less than 12 hours in orbit may have been the test of a new space-borne atomic weapon built to attack enemy aircraft carrier task forces in the Indian Ocean.

The North American Air Defense Command (NORAD) yesterday confirmed that the Soviet ship was launched from the cosmodrome at Kapustin Yar on the Volga River late Tuesday and splashed down in the Indian Ocean early yesterday about 360 miles south of the Australian-owned Cocos Islands. They are about 500 miles south of Jakarta and 2,900 miles west of Darwin in northern Australia.

The Australian Defense Department said the spaceship was recovered by a task force of seven Soviet naval vessels that had been in the area for the last two weeks. The Australian Navy had kept a close watch on the Soviet task force with an oceanographic ship and Orion surveillance aircraft.

The Soviet task force was reported to be made up of three space vehicle recovery vessels, a support ship, a space tracking ship, a Kara-class guided missile cruiser and a Kashin-class guided missile destroyer.

The task force is almost identical to one the Soviets used last June to recover a spacecraft identified simply as Cosmos 1374, which flew one orbit around the Earth before splashing down in the same region of the Indian Ocean.

U.S. space intelligence sources have said that Cosmos 1374 weighed about a ton and had no wings, but had a triple tail to stabilize its return to Earth. The tail also gave it some cross-range to enable Soviet controllers to bank its final flight to either the left or the right.

Some sources said that Cosmos 1374 was a test of a miniaturized version of the American space shuttle that had no military applications, but others argued that it is a space-borne nuclear weapons system targeted at the Indian Ocean. Those who argue that it is a shuttle test point out that the Soviet Union has signed the treaty banning nuclear weapons from space.

Those who contend that it could be a weapons test point to the fact that the Soviet ship was launched from Kapustin Yar, where nearly all Soviet military missile flights originate. A launch from Kapustin Yar takes a Soviet spaceship directly over India and out over the Indian Ocean, then around the northern tier of Europe and across the Soviet Union again where it can be tightly controlled from the ground.

Manned Soviet space flights have never been launched from Kapustin Yar. They are always launched from Tyuratam in Soviet Asia and land on Soviet territory in the western part of Soviet Asia. Unlike the United States, the Soviets do not make water landings and recovery of their manned spacecraft.

Of special concern to Soviet space watchers is the fact that the United States now uses the British-owned island of Diego Garcia in the Indian Ocean to warehouse supplies for its Rapid Deployment Force in the Persian Gulf in the event of war there. The U.S. and British navies are also more active in the Indian Ocean than they have been in the past.