Russian scientists plan to shut the hatch Thursday on six men who will attempt to remain cooped up in a fake spaceship for 520 days - about the length of time it would take to get to Mars and back. During this odyssey of isolation, University of Pennsylvania professor David Dinges will be monitoring their sanity.

Dinges, a psychologist, psychiatrist, and sleep expert, will be testing out some high-tech interventions, including a kind of emotion-cam, designed to read the faces of the volunteers and assess whether they're exhausted, angry, depressed, or otherwise under stress.

If past long-duration missions are any indication, there will be trouble, Dinges said. While NASA doesn't want to publicize the ugly details, he said, there's plenty of evidence from Skylab, the International Space Station, and the Russian space station Mir that astronauts and cosmonauts can quarrel, sulk, rage, and go into space funks of all kinds.

The purpose of the simulation, called Mars 500, is to test various ways to flag problems and intervene before someone snaps.

On a real Mars mission, "you can't have a dysfunctional crew," he said. "A single human error can compromise the whole mission."

The mission will take place near Moscow and is being run by a Russian agency known as the Institute of Medical and Biological Problems. The six volunteers are all men in their late 20s to early 30s from Russia, China, France, and Italy.

The 17-month "journey" will include a mock landing that will take 30 days.

Dinges, who heads the only U.S. investigation connected to the project, described the mock ship as a network of interlinked Winnebagos - "definitely a cramped-quarters kind of environment."

The volunteers will not see any sunlight - an artificial situation that could alter their ability to work and sleep normally, he said.

A real mission would pose other dangers: Space radiation raises the risk of cancer and cataracts, while weeks of weightlessness can thin bones and shrink muscles.

Since it won't be leaving the ground, the Mars 500 mission can't study those problems, but psychological stress and interpersonal fighting may prove just as important, said Dinges, who is working through the Houston-based National Space Biomedical Research Institute.

Nobody has done anything quite like this before, he said. The closest anyone has come might be the great polar expeditions of the late 19th and early 20th centuries.

For example, in trying to drift over the North Pole, Norwegian explorer Fridtjof Nansen and his crew lived in a ship locked in the North Polar Ice for three years, he said. "That's a long time."

Dinges, who has a fascination with the heroic polar explorers, said they had their issues. On Nansen's expedition, "the crew hated him because he was seen as arrogant; the guy who walked over the pole with him hated him; and the doctor got addicted to morphine."

The Mars 500 mission will challenge people in ways that go beyond even the ordeal of Nansen's crew, Dinges said. Those men could at least get out of the ship and run around.

And on the International Space Station, he said, astronauts can get private consultations with psychologists on the ground to talk out whatever issues might trouble them.

On a Mars mission, such sessions might be interrupted for days or beset by delays as long as 20 minutes between attempts to communicate.

To make the simulation truer, the Mars 500 volunteers will also get only spotty communication with the outside world and suffer long delays.

Dinges said one of the biggest challenges for him would be dealing with the volunteers' natural reluctance to admit to problems. "These are professional people who are not always eager to embrace negative concepts about themselves," he said. "You can't just ask them what they'd like to do to the guy next to them," and expect to get the unvarnished truth.

That's one reason Dinges is using technology to go beyond simple self-reporting.

His emotion-reading webcams will use special software designed to detect various signs of trouble - whether it's debilitating fatigue from lack of sleep, desperate loneliness, or fury at crewmates.

He's also looking for a condition known as neurasthenia - a term that's not often used in the United States but that describes a type of depression characterized by loneliness and lack of drive.

The volunteers will also do something called a Psychomotor Vigilance Task (PVT) self-test, he said - a laptop-based task that Dinges designed to measure reaction times.

The volunteers' performance can indicate fatigue as well as attention problems and impulsivity, he said.

In addition, Dinges will be measuring the quality of sleep using wristbands with embedded accelerometers - indicating how much the wearer tosses and turns.

Sleep could be badly disrupted since the volunteers won't have anything like a normal day-night cycle. On polar expeditions, he said, many men lost track of time when the sun went down for six months. Back then, they wore windup watches that would slow down, and the men would become disconnected from the cycles of hours, days, and weeks.

That happened on a previous mock mission - just 240 days - also carried out near Moscow back in 1999.

For that mission, the crew was five men and one woman - a Canadian engineer who accused a Russian crewmate of sexual harassment.

The London Guardian reported that on New Year's Eve, the crew got wine and vodka "as a treat." The two Russians got into a "bloody fistfight," and one of the men then "dragged the female team member away from the cameras and tried to force his tongue down her throat."

This crew is all male - but nobody knows what will happen with a confinement this long. Just in case, the crew won't gett any alcohol this New Year's Eve, Dinges said.

Russians may have behaved badly on the last mock mission, but they lead the world in long-duration space flight. The current record is 438 days in 1994-95, held by cosmonaut Valeriy V. Polyakov.

Former astronaut Leroy Chiao said he believed that the lessons from Mars 500 could prove crucial to success on a real Mars mission. He recalls hitting an emotional and mental peak about halfway into his six-month mission on the International Space Station.

Then it got harder in part because he missed the natural world. "You're looking down at the Earth - seeing this great scenery, but you're not actually in it," he said. Some plants were on board, he said, but it wasn't the same as smelling real grass.

Most of Chiao's mission was spent with just a single cosmonaut, he said, and the two men got along extremely well. "It sounds kind of amazing," he said, but both were pretty easygoing.

A crew of six offers more potential for conflict.

Chiao said it's important to be mentally prepared for a long mission. While he was orbiting Earth, he said, NASA briefly considered extending his six-month mission to a year to sell his return seat and his Russian companion's on the Soyuz rocket to two space tourists.

Luckily, he said, mission control brought him down as originally planned.

He said he knew that not all crews were so compatible as his; astronauts that stay together for six months or more often return and never talk to one another. On Russian missions, he said, it's been reported that crew members were on the verge of killing one another.

He said he admired the courage of the people volunteering for the mock mission. In space, he got the luxury of floating weightless and the chance to photograph an ever-changing series of beautiful views of Earth.

A real Mars mission won't have those same photo opportunities, he said. The view of Earth will recede until it gets lost in the stars.