To understand what's it's like to make a long-duration voyage aboard the international space station, imagine taking a really long trip in a car. And then imagine never getting a chance to stop or step outside, even if your traveling companion is driving you up the wall.

"I don't care who you fly with, it could be your best friend, there are going to be times where you get on each other's nerves," said station astronaut Daniel Bursch, wrapping up a record 194-day stay in space. "That happens, and you find a way to deal with it, whether its exercise or be by yourself or work on a hobby."

Bursch, Carl Walz and Expedition 4 commander Yuri Onufrienko were launched to the station Dec. 5. They originally planned to return to Earth in May, but their flight was extended a month and a half to give ground crews time to develop plans to replace a faulty joint in the station's robot arm. That work will be carried out Thursday during a spacewalk by Franklin Chang-Diaz and Philippe Perrin.

Assuming an on-time landing aboard the shuttle Endeavour next Monday, Walz and Bursch will set a new U.S. space endurance record of 194 days. The old mark of 188 days, set by astronaut Shannon Lucid in 1996 aboard the Mir space station, was broken last night.

"It's certainly not something that we set out to do, to break a record like this," Bursch said today during a news conference. "We all miss our families, but we're all really happy everything's gone really well and we'll be happiest if we know folks on the ground are proud of what we've done."

Said Walz: "I agree with Dan, this wasn't something that we set out to do. But I think we were able to accomplish all of our objectives and more during our flight. It's been a little bit tougher on our families and we really have to thank them for hanging in there during this long flight. They've really done a great job and we're really looking forward to getting back to our families."

All three said they were also looking forward to eating pizza after six months in space.

"What about me? I want the same, maybe twice," Onufrienko said.

Bursch said the biggest challenge facing astronauts on long-duration voyages is psychological, not physical deterioration.

"Without a shadow of a doubt in my opinion, the biggest challenge would be mental and psychological, overcoming just being up here for that amount of time," he said.

"If you think about taking a family trip, whether it's with your spouse or with your family, and never getting out of the car, you can imagine some problems are going to crop up no matter how well you get along," he said. "If you think of it a lot like a marriage, in a marriage there are going to be problems, whether it's mis-communication or not enough communication, it's very similar to that."

Endeavour's landing time has changed by an orbit or so and it's now targeted for 1 p.m. Monday. Assuming that time holds up, Bursch and Walz will have logged 193 days 18 hours and 41 minutes off the planet.