As long as thunderstorms in the area around Kennedy Space Center in Florida hold off, the space shuttle Atlantis should be able to start its 10-day mission, carrying five US astronauts and two Russian cosmonauts to a meeting in space over Siberia.
If the mission goes ahead, the shuttle astronauts will link with Mir, which has been orbiting Earth for nine years, and exchange two crew members and carry out joint scientific experiments for five days. The shuttle will bring back three crew now on Mir, including the US astronaut Norman Thagard, who has spent more than 100 days in space, a record for an American.
But where the brief meeting in July 1975 between Apollo and Soyuz seemed to herald a brave new era for space travel, the forthcoming link-up takes place against a background of swingeing budget cuts at Nasa, while the Russian space programme, saddled with ancient technology, struggles for funding,.
The docking is the first of 10 planned link-ups between US and Russian spacecraft, which have the longer-term aim of preparing for the assembly of the International Space Station, due to start in 1997 and be in flight by 2002.
Bringing together the craft, each weighing more than 100 tons, will be a precise task. The margin for error is three minutes, with 5cm tolerance in guiding the docking systems together. It promises to be spectacular. "When I look at the things that I've been able to do in my flying career so far, this is going to be the biggest thing I've done," said Navy Captain Robert "Hoot" Gibson, combat pilot, test pilot and, for the past decade, shuttle commander. "It's kind of like threading a needle."
Furthermore, if the take-off of Atlantis from Florida is delayed by more than five minutes, it will have to be held for another 24 hours for the link-up to happen at all. Yesterday the Kennedy Space Center said there was an 80 per cent chance that bad weather will delay the initial launch time, and a 70 per cent chance of a 48-hour delay.
Nasa will be hoping for a successful outcome. It has been attacked by Republican members of the House of Representatives over the size of its $30bn (pounds 19bn) budget, and there is still opposition to the space station's proposed $2.1bn funding.
In 1998, Nasa's budget will be cut to $13bn. But it estimates that Russian involvement in the programme will save the US $2bn in funding, making it worth the $400m that the US will pay Russia over the next four years for Russian space hardware, services and data.
"In effect, it's a merger of the US and Russian space programmes," John Logsdon, director of the Space Policy Institute at Georgetown University, Washington, says.
Rocket launches are seldom delayed at Russia's launch center in Kazakhstan because of weather, but the harsh winters can make work difficult. In 1994, the Russians had trouble getting a Mir supply ship to its fueling station because of 24 feet of snow.
"We actually had to dig a tunnel in the snow for a train which was carrying the vehicle," said Valery Ryumin, vice president of the shuttle-Mir program.
The joint experiments will use the low-gravity conditions of the spacecraft to investigate changes in body functions in space, and also conditions such as anaemia, high blood pressure, osteoporosis and kidney stones.Reuse content