Tim Furniss/FLORIDA
Russian cosmonauts Anatoli Solovyov and Pavel Vinogradev will perform a 6h internal spacewalk in the connecting node/airlock of the Mir space station on 20 August, in an attempt to restore the station's electrical power to 70% of its normal output. Equipment to support the task arrived with the Progress M35 tanker on 7 July.
Solovyov and Vinogradev will be launched as planned aboard the Soyuz TM26 on 5 August - on the 200th manned spaceflight in history - and will now perform the major restoration work on the station instead of the current Russian residents, Vasily Tsiblyev and Alexander Lazutkin, who will return to Earth on 14 August.
The three-week commercial French science-research mission by Leopold Eyharts, who was also to have been launched on the TM26, has been delayed until early 1998 because there was not enough power available on the Mir to make the flight viable.
Tsiblyev, Lazutkin and US astronaut Michael Foale have been wrestling with problems on the Mir since 25 June, when a Progress tanker craft collided with the station's Spektr module, damaging one of its four solar panels and causing a leak which depressurised the module (Flight International, 2-8 July).
Tsiblyev and Lazutkin were scheduled to make the internal spacewalk, to install a new centre section to the airlock hatch leading into the Spektr module, allowing electrical cables from the module to be re-attached to the Mir's main power supply.
Tsiblyev became unwell, and it was decided that Foale would assist Lazutkin, but, on 17 July, while practising the spacewalk, one of the crew accidentally unplugged a cable leading to the main computer, causing a loss of attitude control and power.
Systems were restored a day later, using the thrusters on the attached Soyuz TM25 craft and the station's gyros.
Crew fatigue may have been a factor in the incident, and mission managers decided that the resident crew should ride out their mission with no additional stress.
Although the incident received widespread attention from the media, restoring attitude control has become almost a routine procedure. "I think the situation has been overdramatised," says Yuri Koptev, director-general of the Russian Space Agency.
These events "-are a graphic illustration of the kind of work we will have do, operationally, on the International Space Station [ISS]", says Frank Culbertson, manager of the Shuttle Mir programme. If it had not been for the collision incident, the "unplugging" would have received scant attention, according to Culbertson.
During the repair work, Solovyov, who is a veteran visitor to the Mir, and Vinogradev, will work in the unpressurised node of the station, leaning into the Spektr module, reconnecting cables and installing the drogue section in the original hatch.
Even with three of the Spektr's solar panels reconnected to the power supply, the loss of full-pointing capability to the Sun will reduce their capacity, says Culbertson, hence the target of 70% power - a 20% increase on the present output.
That will be enough to restore power to the attitude-control system and allow the Priroda and Kristall modules to become fully functional, Culbertson says.
After the repair has been completed, one of the cosmonauts may then inspect the interior of the Spektr, if time allows, says Culbertson, who adds that "-ground tests indicate that there are unlikely to be toxic chemicals in the module". There could be dangerous debris, such as splinters of shattered glass, however.
During the spacewalk, Foale will remain in the Soyuz TM27 craft. The TM's orbital module will remain opened to receive the spacewalkers if there is a serious problem which, at worst, could call for an immediate return to Earth.
Evacuation of the Mir would be a critical move as the 125t station would be uncontrollable and could rain debris on to land when it re-enters the atmosphere.
A planned controlled de-orbit over an ocean, planned for 1999 when the ISS is operational, will require the propulsion systems of two Progress tankers.
On 3 September, Solovyov and Vinogradev will conduct an external spacewalk to inspect the Spektr module to ascertain whether a repair can be made to its punctured hull. Plans will then be drawn up for a possible repair.
NASA is still determined to replace Foale with US astronaut Wendy Lawrence after she is launched aboard the Space Shuttle STS86/Atlantis from the Kennedy Space Center on 18 September for the seventh Shuttle Mir Mission. "There are no plans to delay September's mission," according to Culbertson.
During the mission, Russian Vladimir Titov and US astronaut Scott Parazinsky will conduct a spacewalk, which could be amended to include further inspections and possible repair work.
"We'll look at that closely, but it looks pretty difficult, given the configuration of the Mir and the training time," says Culbertson.
Foale will return with the rest of the Shuttle crew after the orbiter has completed a fly-around inspection of the station. Lawrence will be replaced by astronaut David Wolf in January 1998.
The Mir's problems contrast with Space Shuttle operations at Kennedy. Before the STS86 is launched, the STS85/Discovery mission will be flown on an Earth observation mission on 7 July.
Source: Flight International
