Commander Vladimir Kovalyonok and flight engineer Aleksandr Ivanchenkov established a new space-endurance record of 139 days.

The station operated in gravity-gradient stabilized mode between 24 and 26 June to avoid attitude control system engine firings which could cause interference with a 3-day smelting experiment using the Splav-01 furnace.

[3] Soyuz 30, with Pyotr Klimuk and the second Intercosmos participant, Mirosław Hermaszewski of Poland, arrived at Salyut 6 on 29 June.

Progress 2, the second uncrewed supply tanker to dock with a crewed space station, arrived at Salyut 6 on 9 July.

Experiments continued, with glass and semi-conductor tests done with the Kristall furnace, newly installed in the transfer tunnel leading to the rear docking port.

[3] The crew complained of headaches before realizing the carbon dioxide detectors had failed to alert them to change the air purifiers.

Their main mission was to retrieve material from the Medusa experiment, left on the station's exterior by the Soyuz 26 crew in December.

Supplies aboard the tanker included strawberries, onions, milk, 450 kg (992 lb) of air, 190 litres of water, fur boots, newspapers, film, letters and equipment.

It was the first tanker not to carry a fresh supply of propellant for the station, as Progress 2 had so recently replenished Salyut 6's tanks.

Progress 4 had 1,300 kg (2,900 lb) of equipment aboard, including air canisters, clothes, magazines and food.

[3] Towards the end of the mission, the cosmonauts noticed abnormal behavior with the station's engines and reported it to ground controllers.

After the residency was finished and Salyut 6 went back into uncrewed mothball mode for the next several months, ground crews studied telemetry data from the station to figure out what was wrong with the propulsion system.

Further use of the main engines could aggravate the leak and possibly ruin the entire propulsion system, including the attitude control thrusters.

As a result of this development, it was decided to not risk firing the main engines again for the remainder of the station's operating life.

With Salyut 6 limited to its attitude control thrusters, all orbital maneuvers from now on had to be carried out by visiting spacecraft.

The relatively good shape the crew were in was seen as a direct result of the hard exercise program carried out in the final days of the mission, and cleared the way for even longer flights.