what is the purpose of the international space station (iss)
International Space Station The ISS serves as a microgravity and space environment research laboratory in which crew members conduct experiments in biology, human biology, physics, astronomy, meteorology, and other fields.[11][12][13] The station is suited for the testing of spacecraft systems and equipment required for missions to the Moon and Mars.[14] The ISS maintains an orbit with an altitude of between 330 and 435 km (205 and 270 mi) by means of reboost manoeuvres using the engines of the Zvezda module or visiting spacecraft. It completes 15.54 orbits per day.[15]
Space Shuttle program The Space Shuttle program was the fourth human spaceflight program carried out by the National Aeronautics and Space Administration (NASA), which accomplished routine transportation for Earth-to-orbit crew and cargo from 1981 to 2011. Its official name, Space Transportation System (STS), was taken from a 1969 plan for a system of reusable spacecraft of which it was the only item funded for development.[1]