HOUSTON -- All but sidestepping the most pressing questions about the future of the International Space Station (ISS), senior U.S., Russian, European, Canadian and Japanese space officials presented on Tuesday what amounted to little more than a guided tour of 16-nation orbital outpost.

William Gerstenmaier, NASA's ISS program manager, and moderator of the panel discussion at the World Space Congress, came the closest of any of the panelists to addressing budget problems that plague the station.

"Funding is an issue for nearly every partner who must navigate through their unique political and economic environments." Gerstenmaier said.

Michail V. Sinelschikov, the head of piloted space programs at the Russian Aviation and Space Agency (Rosaviakosmos), hailed the ISS as "an important stepping stone on the way to expanding our own habitat."

Speaking through an interpreter, Sinelschikov said that while Rosaviakosmos' primary objectives for the ISS are scientific, the agency sees commercial ventures such as space tourism and show business as good ways to bring additional funding to the program.

He said Rosaviakosmos is still considering contributing several additional modules to the ISS, including two research modules and a multipurpose module, although he did not say how Russia would fund such a contribution.

By and large, the video presentations and speeches were exceedingly upbeat, depicting the station as a world class research facility that will achieve astonishing scientific breakthroughs benefiting life on Earth and prepare the way for humankind to venture far beyond.

NASA's chief scientist, astronaut Shannon Lucid, drew a comparison between the current state of space exploration and sailors some five hundred years ago who feared to venture far from the coastlines lest they fall off the edge of the Earth.

"Today we hug the rim of our planet with the ISS just as the sailors of old hugged the coastline," she said.

Once those explorers finally ventured far from the sheltering shore, she said, they learned the hard way about scurvy and other effects of vitamin C deficiency.

The space station, she said, has tremendous potential to show humankind what it needs to know about living and working in space before setting off on any deep space adventures.

"If the ancients would have had an equivalent facility, they would have know that vitamin C is essential to long sea voyages," she said.