American space officials said yesterday that the Soviet cosmonauts of Soyuz 25 failed in their mission because they overshot the orbiting Salyut 6 on Monday and were unable to make a second attempt at docking with the 20-ton space station.
That was the opinion of United States space officials, who felt that cosmonauts Vladimir Kovalenok and Valery Ryumin were forced back to earth because they did not have enough battery power in their two-man spacecraft to stay in space another 24 hours.
"We believe Soyuz 25 [did not have] solar panels to deliver extra electricity," said one U.S. space official at the Johnson Space Center in Houston. "We believe the spacecraft was on battery power to save weight, which meant the cosmonauts did not have the time to correct the navigational errors that forced them to overshoot Salyut."
The abortive flight of Soyuz 25 was the third time in a little more than three years that Soviet cosmonauts were forced back to earth because of a failure in the Soyuz navigational controls. The first was Soyuz 15 in August 1974 and the second was Soyuz 23 a year ago.
What apparently happened on all three Soyuz flights was that the spacecraft's navigating computer brought the cosmonauts to within 120 yards of the space station and then flew them in front of and at least 500 yeard above it.
At that distance, the cosmonauts cannot take over the spacecraft controls. They are literally at the mercy of the onboard computer, which is supposed to fly the scyuz to a prearranged rendesvous 100 yards directly behind the 20-ton space station where the cosmonauts take the controls for the first time.
So intricate are the complexities of celestial mechanics that the cosmonauts were unable to correct their position in time to make a second pass at the Salyuz. The Soyuz spacecraft was believed to be on battery power only, which meant that the cosmonauts had only a 48-hour electrical supply.
Often, the Soyuz spacecraft flies in orbit with two solar panels deployed to continually recharge its batteries, but on this flight the cosmonauts were believed to be carrying extra stores and supplies to put aboard the Salyut space station. The Salyut is fitted with solar panels, so that if Soyuz had docked with the space station it could have recharged its battiers through the Salyut.
U.S. space officials believe it will be some time before a second Soyuz crew leaves earth to dock with the Salyut 6. The last time a cosmonaut crew overshot a Salyut it was four months before a second crew repeated the attempt.