When It's Lost in Space, It's Really Lost

Veteran spacewalker Jim Reilly said it is quite tiring to work in a spacesuit. It may look like a big, fluffy marshmallow -- but it is really a small spaceship.

An astronaut on a space walk lost a tool bag like the one shown, when it slipped away from her.

(Gina Sunseri/ABC News)

"The thing that probably affects you more and makes you more tired is operating in a low vacuum, or low pressure," he said. "We are working inside of a suit that is pressurized at 4.3 PSI, so it is fairly rigid, so you have to learn how to do things differently. You just don't reach up and grab it like this, otherwise you will wear yourself out."

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NASA is tracking the lost tool bag to make sure it doesn't crash into the International Space Station or Endeavour. Flight controllers said it is orbiting somewhere near the space station and expect it to deorbit soon and burn up on re-entry through Earth's atmosphere.