The charter crew of the International Space Station should be in place by 1999. This pioneering team, including US astronaut and commander, Bill Shepherd, and Russian flight engineer Sergei Krikalev, will live aboard a lab under construction, and will, among other things, work to put the space house in order for the minions to come.

Perhaps the most exciting prospect for this groundbreaking crew, however, will be the chance to explore the natural world without the limitations of gravity. Virtually free from one of four fundamental forces of nature, they will be able to explore the universe in unprecedented ways. Already, researchers around the globe are planning investigations into everything from cancer and biomedicine to materials science and the stars.

An aquatic habitat is one of the research facilities planned for the International Space Station

One of the largest advantages offered by the ISS is the ability to perform truly long-term studies, previously difficult to impossible in the laboratory of space."The space station offers a unique advantage for a lot of different disciplines," says Ned Penley, Acting Manager of the Research Requirements and Disciplines Management Office at NASA. "The fact that we'll have a laboratory there which is a long term laboratory is a tremendous step toward doing iterative research in space. If the principal investigator on the ground sees something interesting in his laboratory, he can say, "Wow, let's look at that, let's change this or that parameter.

On the International Space Station, where gravity's effects are reduced many times, scientists will be able to observe aspects of fluid behavior difficult or impossible to "see" in normal gravity.

"When we do research with the shuttle, we can do that to just a small degree. We'll get the chance to change the conditions in an experiment once or twice a year at most. But with the ISS, we'll have the facilities --and the wherewithall-- to change an experimental parameter in real time, as we adjust our research plan and pursue those areas that are the most fertile at the time."

While no experiments have been formally scheduled by NASA -- that will have to wait until the facilities are closer to completion -- the agency and its partners have identified the priorities for microgravity research:

• Biotechnology: Gravity tends to have a deforming effect on the growth of protein crystals often used to make drugs as well as livings cells, the stuff of which human tissue is made. Researchers say that by studing cell growth free of gravity's influence, they should gain a deeper understanding of the natural forces at work within; tissue samples grown in space would be an invaluable research tool for testing medical procedures, while protein crystals may help the pharmaceutical industry create more effective treatments for viruses like AIDS.

  Research on protein crystals and the fundamental building blocks of life will enable scientists to develop new drugs and vaccines.

  "The National Institute of Health has said that protein crystal growth is the number one research tool that we'll be using in the next century," says astronaut Dan Bursch. "On Earth, gravity distorts the shape of the crystal, which invariably winds up with imperfections. In space, we can grow the crystals larger and purer and then bring them back to Earth.

  "I still remember a protein scientists were studying on one of my past flights --it was called alpha interpheron and was used in the treatment of cancer. The treatment has some bad side effects. If we understand the structure of the protein then we can alter the protein slightly and then synthesize it. We can make a whole new family of pharmaceuticals that can be used in the treatment of cancer, but without the bad side effects."

• Candle on Earth (left) burns hot and white; candle in space (right) burns blue.

  Combustion Science: 85 percent of the Earth's energy comes from complex combustion, or the burning of fuels. It only makes sense, of course, that gravity would distort the process, as is evident to anyone who has ever compared a candle burning on Earth and one in Zero-G. Gravity pulls heavier gases to the base of the flame, giving it an oblong shape. Soot from the burning wick is pulled downward and reignited, making the flame brighter and hotter. But in space, microgravity creates a hemispherical blue flame that is not nearly as hot. Without the gravity-caused distortion, scientists hope to learn enough about combustion to create more efficient burning processes. NASA estimates that even a 2 percent rise in efficiency will save the world economy over $8 billion a year.

• The crystals on the left were formed in Earth's gravity, while the one on the right was developed in microgravity during a shuttle mission.

  Materials Science: Experiments performed on the space shuttle have demonstrated that gravity has a tremendous effect on the formation of materials, impacting the size, shape, and structure of the crystals that comprise them. A microgravity experiment conducted on zeolite crystals, often used as filters, catalysts, and absorbents in the chemical process industry -- produced counterparts with a volume increase of 175 percent over crystals grown on Earth. Researchers trying to improve manufacturing processes have also been able test the impact of physical factors like surface tension once gravity no longer exerts an influence.
• The Impact of Long-Term Space Travel: It's no surprise that over the long haul life in space presents problems for people who have evolved under the specific conditions of planet Earth. Indeed, the experts liken weightlessness to long periods of bed rest. Muscles can atrophy, and astronauts must maintain strict exercise regimens to counteract the effect. Weightlessness can also damage the skeletal system, inducing an osteoporosis-like condition as bones shed calcium at an alarming rate. The shed calcium can cause ailments like kidney stones, and some researchers fear that after a particularly long journey, astronauts could be so damaged they could never return to Earth. Life in near-zero gravity affects the cardiovascular system as blood pools to the head, causing headaches and nasal congestion. Blood-cell production in the bone marrow can be slowed, compromising the immune system and causing anemia.

  French payload specialist Jean-Jacques Favier dons a headset for the COIS experiment, studying changes in the coordination of head and eye movements associated with adaptation to microgravity.

  Already, evidence indicates that humans do eventually adapt to new surroundings; crews who have been in space for shorter periods of time often fare worse than those who stay longer. Nonetheless, the true impact of long-term space travel has yet to be determined. And it seems obvious that studying our ability to endure space and developing treatments and health systems that work on high -- on the agenda for ISS scienctists -- must underpin any human impetus to reach distant planets and stars. Indeed, even a journey to planetary neighbor Mars would take two years, at best.

It is these and other areas of research that NASA believes justify the expenditures and risk involved in creating the International Space Station. There are still those who wonder why, with so many other pressing needs here on Earth, the worlds' governments would spend so many millions to stake their claim in the heavens. Once, the answer might have been national pride, or the inability to refuse a challenge delivered by nature. Now, it is that and much more.

"We get a lot of criticism, says Kelle Pido."Oh, it costs so much money, and that money could be put into AIDS research or that money could go here or there, but if people really knew the potential for the Space Station, they wouldn't complain."