That kind of close work with an astronaut in orbit is a dream come true for scientists who want to see what happens when the gravity factor is removed, and for many experiments there is no other way to remove it. Drop towers and parabolic aircraft flights just do not offer enough time in microgravity, and experiment lockers on the space shuttle did not provide the continuity for the long-term laboratory work many experiments require.

The space station can solve that problem, and scientists, engineers and managers are starting to realize just what that might mean in terms of discoveries, applications and return on investment. After 10 years and at least $100 billion, NASA and its international partners are beginning to move beyond the transition from station assembly to station utilization and starting to do real work in space.

It has not been easy, and it is not finished. At present, the U.S. capacity on the space station is about 72% full, according to Julie Robinson, NASA's space station chief scientist. There are 58 bays in the multiuser express racks scattered through the station. Those are about half full and expected to reach 70% utilization in the coming year and a half, she says, comparing managing station resources to running a hotel.

“Other parameters like real estate are not completely full, because that provides opportunity for people to build a new piece of equipment that wouldn't maybe have been envisioned five years ago, and get that on orbit,” Robinson says.

It took so long to build the space station that at least a generation of young scientists largely went elsewhere with their careers. The next generation is finding a complex set of ISS players wrangling for position and priority. The five space agencies that make up the international station partnership must agree among themselves on priorities and, at the same time, reconcile their positions with their own diverse constituencies. Sometimes one experiment has several different constituencies.

Ferkul is principal investigator on the Burning and Suppression of Solids (BASS) experiment on which he works with Pettit and his crewmates. From its start in September 2011 until it closes out in March 2013, the BASS team will try to ignite 41 samples in the Destiny Laboratory Module's Microgravity Science Glovebox. They are applying a wire heating element to flat, spherical and candle-like samples to determine if and how they burn in microgravity with different oxygen flow rates, and how quickly they are extinguished in a nitrogen flow.

In addition to basic safety questions, such as how well Nomex burns in space and how to put out fires there—subjects of great interest to human spacecraft manufacturers and their potential passengers—the tests will gather a wealth of data on combustion in the absence of gravity that can be applied to terrestrial systems that use flame.

“We can refine the model and then apply it to terrestrial applications like engine combustors, furnaces, fire safety—a wide variety of combustion,” says Ferkul. “Even a fraction of a percent improvement in efficiency makes a big difference.”

All those different potential applications and the “stakeholders” who want them make it difficult to set priorities for using scarce station resources. Since the orbiting lab was completed, those problems have sometimes overshadowed the promise that the station is just beginning to show.

In practice, NASA and the Russian space agency, Roscosmos, keep track separately of how they use their station assets, dividing the six-member crew in half. On NASA's end of the station—home to the European, Japanese and U.S. laboratory modules—the three non-Russian crewmembers spend a collective average of 35 hr. per week on research. The rest of their time is spent on exercise to counter the effects of microgravity on their bodies, as well as station maintenance, operations and housekeeping, sleep and personal time.