An explosion last week of a rocket launching Soviet cosmonauts is the second recent hitch in Moscow's accelerating bid to assemble a permanently manned orbital complex.
A Soviet source, accurate in the past, told the Monitor that ''the rocket lifting the capsule exploded.'' The mishap, first reported in a Washington Post article from the United States citing intelligence sources, has yet to be mentioned publicly by Soviet officials or their news media. Neither this mishap nor one that occurred earlier this year involved loss of life.
The source said the announcement of the launch, planned for release late last Tuesday night in Moscow, had been shelved after the accident.
The capsule's crew had been due to dock with the Salyut-7 orbital station, which Soviet designers hope to make the core of a large modular space complex. This latest in the cylindrical Salyut series, launched last year, was briefly expanded this March by addition of a ''module' with its own propulsion, guidance , and life-support systems.
The source said that, despite some anxious minutes immediately after the disaster, the cosmonauts had escaped injury. ''Their capsule was fortunately lifted above the explosion and flames,'' the source said, and they had landed nearby.
Both he and Western experts here expressed no doubt the Soviets' space-complex program will continue despite the accident. But some slight delay could result, diplomats here predict.
They note the mishap is the second piece of unwelcome news for Kremlin space planners this year. In April, the first three-man crew sent to dock with the expanded Salyut-7 returned to Earth without having done so, apparently due to what have been nagging guidance hitches with the ''Soyuz'' capsule, the Soviets' workhorse transport craft.
An effort by another, two-man Soyuz crew did succeed early this summer. That crew is still aboard Salyut-7, although initial Soviet news reports said they were not planning a long stay. A Pravda article last Sunday, making no mention of the recent rocket explosion, said the Salyut's crew remains happy and healthy.
Meanwhile, the Kremlin campaign to assemble a module-by-module space complex manned by rotating crews seems gradually to be moving forward.
The module launched this spring, called Cosmos 1443, carried out a number of tests involving maneuvering of the expanded Salyut.
With the Cosmos docked to one end of Salyut, and the cosmonauts' Soyuz transport ship to the other end, the ''complex'' weighed some 50 tons. It was about 115 feet in length.
The Cosmos undocked in mid-August. Half of it, carrying various experimental equipment and photographs, parachuted to a soft landing on Soviet soil.
The other half, said to be carrying space refuse, continued orbiting independently for more than a month - its function and activity during that time not made clear by Soviet media reports - before a ''braking'' maneuver caused it to drop in altitude and burn up in the atmosphere ''over a prescribed area of the Pacific Ocean.''
Western experts here assume Moscow's immediate plans involve a further manned launch toward Salyut-7 in the wake of last week's aborted mission.
Thereafter, the experts suggest, the Soviets will likely launch a second ''module' along the lines of Cosmos 1443. A current concern for Soviet space planners seems to be perfecting the ability to maneuver an expanded Cosmos-Salyut-Soyuz complex, and then to add further modules as practicable.
''This complex (before the Cosmos' undocking) . . . was obedient to movements of the small (steering) stick'' on the Salyut, one of the two current crewmen said on Moscow radio several weeks ago.
''It is very difficult to control the (Cosmos-Salyut-Soyuz) machine,'' he said. ''But we manage it.''