More details on outer space etiquette:

...But orbital freefall -- which makes everything seem weightless on the space shuttle or international space station -- by necessity adds some extra twists. Most things have to be secured one way or another, including dental floss and fingernail clippings. And that's where the duct tape comes in handy.

[Former astronaut Tom] Jones said his usual routine would be to stick the floss, the slivers of fingernails and other detritus onto a snippet of sticky tape - then crumple up the tape, put it in a waste bag and seal the bag.

"You can't fly without duct tape or Velcro," said Mario Runco, a veteran of three shuttle flights.

Among the other tips:

* Drinks are generally contained in the kinds of foil pouches familiar to most third-graders on Earth - and the drink straws have to be clamped closed with clips when they're not being sipped from. Otherwise globules of sticky grape juice or orange juice can blurp out of the straw and float around. Jones admitted that he was guilty of this breach during one of his spaceflights, and was embarrassed to find that "our grape spots were still on the walls" of the shuttle interior months later.

* When you brush your teeth, you have to close your lips carefully around the brush, then spit the foam into a towel.

* The shuttle's zero-gravity toilet works by sucking down urine, or using ducted air to blow away solid waste. But because the air currents have to flow in just the right way, you have to make sure to "sit precisely on that seat" to get the proper seal, Jones said. In fact, NASA has a "rendezvous and docking trainer" on Earth so that astronauts can practice their toilet technique before their spaceflight, he said. "After some practice, you begin to get the feel for it, if you know what I mean," Jones said.

* Daily exercise is part of the routine - especially for a long-duration space station flight, because astronauts have to guard against losing bone or muscle mass in zero-G. But because there's no natural convection in freefall, air warmed by the heat of a workout tends to float like a cloud around exercising astronauts. And that leads to increased perspiration. You have to aim an air duct toward yourself to blow away the hot air, or wipe yourself down repeatedly with a towel. Whatever you do, don't let the sweat build up too much. "One false snap of the head, and you'll send a quart of salty water off in someone's direction," Jones said.

* Although the Skylab space station had an actual shower, today's shuttle and station crews bathe by rubbing themselves down with wet, hot towels, then applying some rinseless soap. Hair is washed by applying water to the head (surface tension keeps the water from floating away), then using rinseless hospital-style shampoo. Then you towel yourself off, perhaps putting your head under an air duct to help dry your hair. "If you use that on a daily basis, you'll never offend anyone," Jones said.