Russian space officials decided they needed more time to make sure the more reliable Soyuz-FG type booster used to orbit Soyuz capsules and Progress freighters was still safe to fly.

Contaminated plumbing

Russian Space Agency chief Yuri Koptev said in a letter to NASA that metal contamination in the Soyuz rocket's hydrogen peroxide system triggered the series of events that lead to the Soyuz-U booster failing, Gerstenmaier said.

Russian media quoted Koptev as saying he didn't know the source of the contamination, but was exploring all possibilities from "a manufacturing defect to malicious intent."

"The Russians have inserted some additional tests and inspections down at the launch site to ensure that what occurred on the previous flight doesn't occur on this flight. So that's been accomplished and that looks good," Gerstenmaier said. "The Soyuz has been an extremely reliable launch vehicle, both in the unmanned and manned programs."

It is to take two days for the Soyuz-TMA spacecraft to reach the multinational complex, with docking set for 12 a.m. EST (0500 GMT) Friday.

The three-man crew will spend the next week delivering supplies, performing science experiments and preparing the older Soyuz-TM capsule for its return to Earth. Zalyotin, Lonchakov and DeWinne are to undock about 3:30 p.m. EST (2030 GMT) Nov. 9 and land in Kazakhstan less than four hours later.

Officials say that between the time the Soyuz taxi flight departs and the shuttle arrives, the Expedition Five crew of Valery Korzun, Peggy Whitson and Sergei Treschev must shift their work day so it begins about 11 hours later.

Based on a Nov. 10 shuttle launch, that would give the station occupants only two days to make the adjustment.

"We'd like to have another day in there to help with the crew sleep shifting, so that we have a fully rested crew when we get there with the shuttle," Gerstenmaier said.

Patient crew

Endeavour commander Jim Wetherbee told SPACE.com on Monday that his crew is ready to fly whenever NASA managers say it's time to go.

"I'm not sure I care when we launch," said Wetherbee, who will be making his sixth shuttle flight. "We'd be happy with the 10th. We'd be happy with the 11th, or any time this year, frankly. It's much tougher for the guests and the people who make travel plans to come and watch us launch."

Wetherbee said his chief goal was to return the current Expedition Five station crew from orbit by the end of the year.

"I guess I'm thinking probably the 11th is the date they might pick based on the Russian launch," Wetherbee said.

However, one technical problem remains a potential obstacle for the Endeavour mission to begin.

Engineers still are not sure why a set of back-up explosive charges did not fire as expected during shuttle Atlantis' launch from pad 39B on Oct. 7.

"So far they really have not found a smoking gun," NASA flight director Paul Dye said Monday.

The pyrotechnics help break apart the eight giant bolts that hold a shuttle to its launch pad. Although one set of charges did fire and allow Atlantis to safely launch, both sets are designed to detonate at the same time.

The fact that they didn't raised alarms and caused other problems with the computers that help monitor and control the operation, forcing controllers to perform several critical steps after launch that were designed to be automatically run by the computers.

Workers already have replaced a lot of wiring harnesses and electrical connectors at the launch pad and within the mobile launch platforms, as well as tested the electronics at pad 39A where Endeavour sits, Dye said.

"I think that there's a lot of confidence that that while we don't have a complete answer right now, they're going to have an answer or build some confidence in the system via testing between now and flight," Dye said. "We'll know more when we know more."