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. Last Updated: 07/27/2016

In U.S. First, Astronauts Take Spacewalk at Mir

SPACE CENTER, Houston -- Two shuttle astronauts performed an unprecedented spacewalk outside the Russian space station Mir on Wednesday, wearing jet packs just in case their lifelines broke.

It was the first spacewalk by Americans at Mir.

After extra precautions, astronauts Linda Godwin and Michael "Rich" Clifford floated out of Atlantis as the space shuttle and linked Mir soared more than 400 kilometers above the South Pacific. They had fallen a little behind because of problems with Clifford's spacesuit.

Because it was docked, Atlantis could not immediately dash after Godwin or Clifford if their tethers snapped. The jet packs were intended to propel them back to the safety of the Atlantis-Mir complex.

To facilitate a shuttle getaway in the unlikely event a tether broke and a jet pack failed, NASA ordered the hatches closed between Atlantis and Mir prior to the six-hour spacewalk. Godwin and Clifford also test-fired the tiny thrusters on their jet packs, inside the cabin, to make sure everything worked.

One of the jet packs was tested during a 1994 shuttle flight. The other has never been used in space before.

During the spacewalk, Godwin and Clifford planned to attach cosmic dust catchers, paint samples and other potential station materials to Mir and test tools designed to fit either U.S. or Russian spacesuits.

It's the kind of work that will be performed by spacewalkers at the future international space station.

Godwin and Clifford were under strict orders not to go beyond Mir's orange docking tunnel.

The last time NASA astronauts performed a spacewalk outside a space station was at Skylab in 1974 -- seven years before the first shuttle flight.