After nearly 12 years of development at a price of $100 billion, the International Space Station (ISS) is fully assembled, and the White House has agreed to keep the station operating until 2020 instead of 2016, as originally planned. But what to do with those extra four years? Researchers, scientists, and engineers are considering that question—while also dealing with the fact that the space shuttles that transport crew and cargo to the ISS will be retiring next year.

Jason Crusan, chief technologist in space operations at NASA, says the agency is working with its international partners to expand the use of the ISS now that researchers will have increased opportunities to conduct experiments in the station’s microgravity environment. Crusan discussed these ideas this week at the American Astronomical Society National Conference, International Space Station: The Next Decade, in Cape Canaveral, Florida.

The space station has two main functions: it serves as a national laboratory for scientific research and a test bed for new technologies. It is funded by the United States, Russia, the European Space Agency, Canada, and Japan, but a total of 59 nations have participated in or utilized research on the station.

About 50 percent of the ISS is used for scientific research, and typically there are between 40 and 50 experiments onboard. Many are biomedical experiments, including research on drugs and treatments for diseases. Microgravity has a significant effect on how cells behave and how materials and metals form, says Marybeth Edeen, manager of the ISS national lab at NASA. For example, scientists were able to develop a vaccine against salmonella food poisoning that is being examined by the U.S. Food and Drug Administration; there are drugs to treat prostate cancer that were tested on ISS in clinical trials; and the Japanese are moving forward on treatments for muscular dystrophy that were tested on the ISS. “You can do experiments on the station that you cannot do anywhere else,” says Julie Robinson, ISS program scientist at NASA.

Researchers are also using the ISS to test space-exploration systems and other technologies that can’t be fully understood until they are in orbit, says Crusan. For example, researchers are working on guidance, navigation, and control systems for satellites and spacecraft; advanced robotics to work on and repair orbiting spacecraft, and more efficient water-filtration systems. The entire space station itself serves as a test bed for life-support systems like power generation and recycling oxygen and water. Such technologies must be perfected if the Obama administration’s space goals are to be fulfilled: sending humans to an asteroid by 2025 and to Mars by the mid-2030s. NASA is authorized to spend $58.4 billion over the next three years to execute the administration’s plan, although the release of the money is dependent on a yet-to-be-passed appropriations bill. Crusan says that future technology projects on the space station like next-generation space suits and electric propulsion systems will be determined when the budget is set.

The last hurdle will be getting crew and cargo to the ISS once the space shuttles retire. Edward Mango, director of the commercial space transportation planning office at NASA, says that when the shuttles stop flying, the next U.S. vehicle will come from commercial companies like SpaceX and Orbital Sciences, and those vehicles will not be ready until at least 2015. Until then, the U.S. will rely on Russian, European, and Japanese vehicles. Russia will carry U.S. crews on at least two flights a year.

The ISS is an engineering marvel, says Robinson. “We want to be able to fully utilize it for the next 10 years.”