Labor Day Weekend for Astronauts: Space Toilet Cleaning and Exercise

American astronauts Doug Wheelock, Tracy Caldwell Dyson (center) and Shannon Walker, all NASA spaceflyers and Expedition 24 flight engineers, pose for a photo with an American flag while aboard the International Space Station during their summer 2010 mission. CREDIT: NASA

Astronauts aboard the International Space Station won't be throwing any burgers on the grill this Labor Day weekend, but at least they'll get the U.S. holiday off — after they clean the space toilet.

Monday is an official rest day for the space station crew, NASA spokesman Kelly Humphries said. The three Americans and three Russians aboard the station, however, won't get to shirk their space duties all day.

"There's always some routine housekeeping and maintenance to do," Humphries told SPACE.com. "Toilets need to be cleaned, the water recovery system needs to be checked — that sort of thing." [Graphic: The International Space Station Explained]

Space workouts and chores

The space fliers also will put in some serious time at the gym. Station crewmembers exercise for about 2.5 hours per day, six days a week to help stave off the deleterious effects of microgravity — which can include dramatic muscle atrophy and bone loss.

The station's gym includes a treadmill, a stationary bike and a weight-training machine that generates up to 600 lbs. (273 kg) of resistance using vacuum cylinders.

When all this is done, the astronauts will be able to relax before hitting the hay. And how do you wind down when you're zooming around the Earth at 17,000 mph (27,419 kph)?

"They'll look out the window," Humphries said. "It may be a movie day. If there's a big sporting event, we may uplink a feed to the station so they can watch it. It all depends on the crew."

Picking their holidays

Space station crews choose their days off together, before their missions begin, Humphries said. Since the station has an international flavor — and there's often pressing work to be done at odd hours — American astronauts don't always enjoy the same days off as their Earth-dwelling countrymen.

But Americans on the station do tend to observe the big holidays. Last year, for example, the crew took both Thanksgiving and Christmas off, celebrating with holiday feasts.

Humphries doesn't know if the astronauts will mark Labor Day in any way — with some sort of special holiday message, say, which they've done in the past.

"In terms of special recognition, often that's done on the fly," he said. "The crew often won't give much advance notice because they don't want to ruin the surprise."

When they get back to work, next week should be busy for the station's crew. The astronauts will prepare for the arrival of the Russian cargo vessel ISS Progress 39, which will deliver 2.5 tons of food, fuel and other supplies. Progress 39 should dock at the station Sept. 10.

• Why Is It Called Labor Day?
• Graphic: Inside and Out: The International Space Station
• Video Show: Life on the International Space Station