Platform Problem Aborts Launching of First Soviet Shuttle Mission

LEAD: The first launching of the Soviet space shuttle was aborted today, 51 seconds before the scheduled liftoff, when an emergency evacuation platform failed to separate from the rocket body and computer sensors shut down the launching, the official Soviet press agency Tass reported.

The first launching of the Soviet space shuttle was aborted today, 51 seconds before the scheduled liftoff, when an emergency evacuation platform failed to separate from the rocket body and computer sensors shut down the launching, the official Soviet press agency Tass reported.

The unmanned mission has been put off indefinitely, Tass said.

''Only after the cause of the malfunction is found, preparation for the launch will be started anew,'' Tass quoted Maj. Gen. V. Gudilin of the Soviet Air Force as telling Soviet journalists assembled in Kazakhstan. ''I think it is too early to tell when this will be done.''

''The period of time needed for this will hardly be a long one,'' he added. ''We are testing an utterly new and very elaborate system, and we must be prepared for such situations.''

The Soviet shuttle, named Buran (the Russian word for snowstorm), was shown on the evening television news every night last week.

Today's scheduled launching would have been the second known trial of the 2,000-ton Energiya rocket. The rocket was unveiled in a largely successful test in May 1987 and, with 170 million horsepower of thrust, is the most powerful rocket in the world.

As a result of the aborted countdown, Soviet technicians will have to remove more than 1,000 tons of fuel, including 150 tons each of supercooled, extremely volatile liquid hydrogen and liquid oxygen from the Energiya, Tass said.

If the launching of an American space shuttle had been postponed under similar circumstances, 51 seconds before liftoff, the delay would be at least 48 hours to allow for unloading of fuel, conducting systems checks and refueling.

The postponement of the launching today was clearly a disappointment to Soviet space officials. The postponement provided the third awkward moment for the Soviet Union's highly visible and highly successful space program.

In September the program of manned launchings to the orbiting Mir space station, largely controlled by the military, and the rival program of unmanned exploration run by the civilian Space Research Institute both suffered setbacks.

First a Soyuz spacecraft shuttling astronauts from Mir failed to complete a crucial firing of decelerating rockets and spent an extra day in space before landing safely.

Then the Space Research Institute's vaunted Phobos 1 probe, headed for Mars, began spinning aimlessly and powerlessly in space because of improper ground commands.

Soviet citizens seem little preoccupied with the success of the unmanned shuttle mission, although the space program is a source of great pride here, as shown by Moscow's huge statue of the first human in space, Yuri Gagarin.

While millions of Americans were transfixed by the launching of the space shuttle Discovery four weeks ago, Soviet citizens seemed pleased but hardly enthralled by the development of their own shuttle.

Still, when they heard the news of the indefinite postponement today, scores of Soviet and foreign citizens called the Soviet national television network and asked what had happened. In the early days of the space program, many problems, including some fatal accidents, were routinely withheld from the public.

The evening news correspondent for the program ''Vremya'' commented as he showed film of the rocket and shuttle on the launching pad, ''Here you can see - nothing has happened with Energiya and nothing with Buran.'' The report indicated the two vehicles would remain on the pad until the problem was discovered.

The Soviet shuttle was unveiled only a few weeks ago. Its purpose remains largely unclear, although on Friday the Soviets, by presenting the general who controls the program, Aleksandr A. Maksimov, in effect confirmed what almost all Western experts believed: that the shuttle program was a military operation.

Nicholas Johnson, a scientist at Teledyne Brown Engineering who follows Soviet space developments, said Friday in an interview from Colorado Springs: ''We've used ours for the repair of expensive satellites, but they don't have expensive satellites to repair. When they fail they just replace them.''

While it is widely assumed that Energiya and the shuttle can eventually ferry huge preassembled components into space, it is not clear what they will do for now. ''We certainly don't know what the Soviets have in mind for it,'' Mr. Johnson said. ''We're not perfectly certain the Soviets know what they have in mind for it.''

The Buran and another shuttle, Ptichka (for little bird) are near-twins of the American shuttles and work on largely similar principles. Though this mission is unmanned, Buran can carry as many as 10 people.

By FELICITY BARRINGER, SPECIAL TO THE NEW YORK TIMES