Astronauts’ Device Defies Weightlessness : Space: Experiment moves blood to counter effects of no gravity. It may ease shuttle crews’ transition to Earth.

Two space shuttle astronauts defied the effects of gravity-free space Sunday, sealing themselves in a waist-high vacuum container that forced blood from the top of their bodies to their legs.

It is one of several medical experiments being conducted during the shuttle Atlantis’ nine-day flight to find ways to ease the body’s rough transition from space to gravity on Earth.

Mission specialist G. David Low was the first to slip into the white, sack-like device.

The vessel was closed tightly around his waist, and the pressure inside gradually was reduced, drawing blood into his legs until the stress on his heart was about the same as it would be if he were standing on Earth.

Shannon Lucid, a biochemist, recorded echocardiograph images of Low’s heart during the hourlong procedure, performed on the astronauts’ third day in orbit.

Scientists believe negative pressure on the lower limbs, in addition to increased fluid consumption, may improve astronauts’ readjustment to gravity after space flight. Astronauts often feel faint once back on the ground.

Shuttle pilot Michael Baker later climbed into the container for an hour of depressurization.

Baker had dreaded the thought of spending so much time in the container. In an interview before the flight, he described the operation:

“It’s basically a big can. You get in it. It has a seal in it. They have a hose you basically hook to the outside of the orbiter and it pulls the vacuum. . . . As you take more vacuum out of the can, you just kind of get pulled down into the can.”

Does it hurt?

“It’s not comfortable,” he said.

NASA officials, meanwhile, were trying to identify a mysterious object that floated beside the shuttle earlier in its mission.

The object, about five feet long and resembling a car bumper, was videotaped by the astronauts Saturday as it sailed along between the shuttle and the Earth.

A NASA spokeswoman told Reuters on Sunday the object was no longer visible from the shuttle. But the mystery remained.

The National Aeronautics and Space Administration believes the object was debris lost during the deployment of a communications satellite Friday. But the agency admits it does not know for sure what was out there.

Nearly identical objects have been seen on previous shuttle flights from which satellites were deployed, Flight Director Phil Engelauf said.

But Engelauf said at a Sunday press briefing at Johnson Space Center that NASA engineers are still scratching their heads over the object.