Astronauts face up to abandoning Mir

If the astronauts on board the Mir space station have had any time to reflect in the past three weeks, they might reassure themselves that this is not, yet, the worst disaster in space.

That unfortunate title belongs to the Challenger Space Shuttle, which blew up 73 seconds after its launch on 28 January 1986, killing the seven astronauts aboard. (Three US astronauts also died before leaving the ground, when the Apollo 1 module caught fire 10 minutes before it was due to take off on 27 January 1967.)

Nor, despite the darkness and cold, are the three men in the most remote location for a disaster; that dubious title goes to the occupants of Apollo 13, who were 200,000 miles from Earth on 13 April, 1970 when they radioed Houston to tell mission control, famously, "We've got a problem." By contrast, Mir is about 250 miles above the Earth.

And it has to be said that this is not the first time that things have looked desperate to occupants of Mir. In May 1990, two cosmonauts were reported "stranded" there by damage to their descent module; at least today's occupants have the Soyuz module as a lifeboat back to Earth. The 1990 problem was solved when an unmanned craft was sent out with a ladder to enable the men to carry out external repairs.

However, this is the longest-running crisis in space, and the exhaustion created among the crew means that the slightest error could be fatal. Although the name of the space station means "peace" in Russian, there has been very little of it for the three-man crew in the three weeks since a practice docking manoeuvre went wrong on June 25, causing the first space collision with a crewed spacecraft. The first 20 minutes after the accident were a terrifying scramble, as British-born Michael Foale, aged 40, heard the hiss of escaping air in the Spektr module where he lived and worked, and had to abandon it at top speed, helped by the captain, Vasili Tsibliyev, 43, and the flight engineer, Alexander Lazutkin, 39.

The blame for the original accident has not yet been placed, but Russian mission control is understood to feel that Commander Tsibliyev was at fault for having used an overloaded cargo module to practice the docking.

Since then, Commander Tsibliyev has developed a heart problem that ground- based doctors suggest is almost certainly stress-related. If the repair mission goes ahead, it has been decided that he will wait in the Soyuz escape craft, while Mr Foale undertakes the dangerous task of going into the darkened Spektr module, where he will have to reconnect the cables that were unhitched.

However, that spacewalk is now planned to occur on the night of July 24-25, and is still being rehearsed in swimming tanks (to reproduce weightlessness) on the ground by Russian technicians at Star City. The latest problems - which occurred when one of the crew accidentally pulled out a cable connecting to the main computer, oxygen generators and power systems - plunged the station to the bare minimum of power needed to keep running.

Mir was first launched on February 20 1986, intended to be a staging post for crewed flights to Mars "by the late 1990s". Instead, it suffered its first setback in April, 1987, when the Kvant astronomy module failed to dock as planned, necessitating a spacewalk to fix the problem.