United We Orbit
It's a story of spacecraft meets spacecraft.
- By James E. Oberg
- Air & Space magazine, January 1997
How a space docking feels can depend on which side of the interface you’re facing—whether you’re the docker or the dockee. But when the 100-ton shuttle Atlantis linked up with the 100-ton space station Mir in June 1995, neither crew had any doubt about what was happening.
Just before contact, with the two spacecraft perfectly aligned, the Atlantis crew had pushed a button to fire thrusters that gave them a last nudge into the Russian docking mechanism. For the shuttle astronauts, it was the noise of the thrusters more than anything that signalled their arrival at Mir. “You could hear the booming of the forward jets,” recalls Charlie Precourt, copilot of mission STS-71. The contact itself is “absolutely imperceptible,” says Kevin Chilton, who commanded the third shuttle-Mir docking mission nine months later. You know something’s happening from “all those cannons going off all around you,” but there was no bumping or jostling inside the shuttle cabin.
On the Russian side it was a different story.
The impact felt “like a big hug,” commander Vladimir Dezhurov recalls. “A real man’s hug.” The Mir began quivering, then calmed down. When the station finally stopped shaking, says Dezhurov, “we understood the docking had occurred.”
Over on Atlantis, where shock absorbers in the docking system dampened the force of impact, the mechanism “bounced like a baby carriage,” Precourt says, but the back-and-forth motion was too subtle to be sensed directly. “The only way we could tell there was any rebound at all was to look in the camera.”
The first orbital hook-up of U.S. and Russian spacecraft in two decades had come off without a hitch.
Docking has been part of the spaceflight repertoire for more than 30 years, and as often happens, NASA has made a complex and challenging operation look boring and routine. In practice it is anything but. Robert “Hoot” Gibson, who commanded Atlantis during the first shuttle-Mir mission, calls space docking “a cross between air-to-air refueling and a carrier landing.” When the two spacecraft are still at a distance, it seems easy. “But the closer you get, the tighter you control, and the smaller the allowable errors can be,” he says. With an unlucky combination of equipment problems and human error, things can go spectacularly wrong, and that’s reason enough to regard each space docking with apprehension and respect.
When Neil Armstrong completed the world’s first orbital docking, connecting his Gemini VIII capsule to an Agena target vehicle in 1966, his joy was soon overshadowed by a life-threatening out-of-control tumble that led to an emergency splashdown in the Pacific (the fault lay in a stuck thruster on the Gemini, not in the docking technique). On the very next flight, a shroud covering the target’s docking port failed to open fully, making docking impossible.