Tito during weightlessness training in a Russian Il-76 aircraft. Photo: Courtesy MirCorp/spaceadventures.com

NASA managers vowed today to continue efforts to convince their Russian counterparts not to launch U.S. millionaire Dennis Tito to the international space station next month, saying the would-be space tourist has not been properly trained and represents a clear safety threat to the multi-billion-dollar station and its crew.

But the Russians, who unilaterally signed a reported $20 million contract to launch Tito to the station, say he is, in fact, adequately trained and that they will launch him regardless of NASA's objections.

"They are going to learn very soon that we are absolutely determined to fulfill all terms of our contract with Tito in April," said a top RKK Energia official. "He signed all the paperwork, paid the money and we are going to do our part, no matter what they (NASA) think."

Senior NASA managers today refused to directly answer repeated questions about what the agency could do to prevent Tito from flying.

But if Tito eventually shows up - and that appears to be all but certain given the increasingly strident rhetoric in Russia - NASA will do nothing to block his entry into the space station or to restrict his movements once on board.

"We are concerned first and foremost about the safety of the station and its crew," said Mike Hawes, a senior station manager at NASA headquarters in Washington. "But in the end, we will not put the on-orbit crew in a position that is more difficult for them than already exists on the station."

Translation: Tito would have full run of the international station and would not be restricted to living in the facility's two Russian modules.

Tito originally contracted to fly to the Mir space station. But late last year, the Russians decided to end the Mir program and the Russians approached NASA about giving him a seat on a three-person Soyuz spacecraft scheduled for launch to the international station April 30.

The goal of the so-called "taxi flight" is to deliver a fresh Soyuz spacecraft to the station to replace the one currently docked to the outpost for use as a lifeboat. The crew bringing the fresh Soyuz up would ride back to Earth in the old one after a week or so aboard the station.

Soyuz spacecraft are only certified for six months in space. The one currently attached to the station was launched Oct. 31. Without a fresh Soyuz, the station's current crew - commander Yury Usachev, James Voss and Susan Helms - would have to return to Earth, leaving the outpost unmanned.

Hawes said NASA is not opposed to private citizens visiting the station at some point. The agency simply wants to develop a uniform set of training guidelines and medical protocols within a legal framework agreed to by all of the station's international partners.

NASA wants to ensure any visitor to the station is properly trained to handle potentially catastrophic emergencies and is thoroughly familiar with the operation of U.S. components.

Hawes said the Russians first approached NASA about the Tito flight in the November timeframe. Since then, the project's "multilateral coordination board" has been trying to develop a uniform set of guidelines.

There simply has not been enough time to work out all the details, he said. In the meantime, NASA, the European Space Agency, the Canadian and Japanese space agencies announced last week they unanimously opposed Tito's flight in April.

Hawes answers questions from reporters at NASA Headquarters today. Photo: Spaceflight Now/NASA TV

"This is an issue that involves all the partners in the program," Hawes said. "We will continue to work in the partnership to find a resolution to this problem.

"We have a number of training criteria that we believe are very important. We believe any visiting crew should have a certain level of training in the United States on the portion of the space station that are not Russian. We think for a civilian or a non professional, if you will, that's probably on the order of eight weeks."

In other words, NASA does not believe Tito can be properly trained in time for the planned April 30 launch, regardless of whether the legal and training guidelines are in place.

In addition, the pace of work aboard the station is so intense during this stage of initial setup and activation that Tito's mere presence would disrupt normal operations.

"The operational tempo aboard the international space station is extremely high," said William Readdy, a veteran shuttle commander who now oversees the shuttle program in Washington.

"The international partners were all concerned that the presence of even a thoroughly trained but non professional at this particular point in time would make nominal operations untenable and emergency operations even more dangerous," he said.

Another Soyuz taxi flight is scheduled for October. However, the Russians have already sold a seat on the October Soyuz taxi flight for the French astronaut Claudie André-Deshays and it is unclear whether Tito can be accommodated on that mission.

But by then, Hawes said, an agreement covering legal, medical and training requirements for station visitors could be completed and Tito could receive the training on U.S. systems that he needs.

"In principle, the partners have no objection to non-professional crew members flying to international space station," Hawes said. "It's just that the framework for that is still a work in progress."

In a confrontation Monday at the gates to the Johnson Space Center in Houston, Soyuz commander Talgat Musabayev and Yuri Butarin refused to enter for required pre-flight training when NASA representatives informed Tito a variety of issues had to be resolved first.

The NASA representatives offered to escort Tito and his bodyguard to the center's main headquarters building to meet with astronaut office representatives and lawyers to discuss his current status.

Hawes said today the Russians objected to being separated from Tito and departed the space center. A source said Tito and the cosmonauts were told earlier the businessman could not begin training until his legal status had been resolved.

They came anyway, the source said, bringing a news magazine reporter with them who was not identified in advance as a journalist.

In any case, the cosmonauts returned Tuesday and began their training without Tito.

Former astronaut Readdy defends NASA's position at today's news conference. Photo: Spaceflight Now/NASA TV

"Speaking from experience, I can't over-estimate just exactly what it takes to fly in space," Readdy said. "I can't over-emphasize the importance of training.

"Thus far, our successes on the international space station have made it look too easy on the surface and I can assure you, it's anything but. Spaceflight is still inherently risky. In fact, I'm reminded of several events that happened during the shuttle-Mir program where even with highly trained, professional cosmonauts and astronauts, the situation was such that it was nip and tuck for a while, the outcome was in jeopardy and they almost had to abandon the MIr space station."

William Shepherd, on his way back to Earth after serving as commander of the international space station's first full-time crew, expressed reservations early today about launching Tito in April.

"Our crew trained for over four years to get ready for our flight," he told a reporter. "The day will come when we'll have civilians and tourists up there, but it's not something you can enter into lightly.

"I think flying people such as Mr. Tito is a good idea, but I think NASA is also right in saying they need time to work with him to make sure that he's ready and I don't think they have it given the schedule that they're working right now."

Shepherd said the station "is a lot more complex than just the Russian pieces of it. I think that's part of why the NASA managers are having this discussion. I don't think the whole question is over yet."

Anatoly Zak contributed to this story from Moscow.