The purpose of maintaining an orbital outpost varies depending on the program. Space stations have most often been launched for scientific purposes, but military launches have also occurred. As of , one fully operational and permanently inhabited space station is in low Earth orbit: the International Space Station (ISS), which is used to study the effects of spaceflight on the human body as well as to provide a location to conduct a greater number and longer length of scientific studies than is possible on other space vehicles. China, India, Russia, and the U.S., as well as Bigelow Aerospace and Axiom Space, are all planning other stations for the coming decades.