the suit in the Shuttle's airlock. The first Shuttle EVA was to occur on STS-5, but an electrical failure on the circulation fan forced the EVA to be cancelled. The first EVA of the new EMU finally occurred on STS-6 when Story Musgrave and Donald Peterson went out in the payload bay of the Space Shuttle Challenger and tested techniques to lower the launch cradle of a solid-fuel upper stage used to boost a Tracking and Data Relay Satellite (TDRS-A) into a geostationary orbit. Other EVAs followed on the Shuttle, notably those on STS-41-B (the first Manned Maneuvering Unit flight), STS-41-C (the Solar Max repair mission), STS-41-G (the first American EVA involving a woman), and STS-51-A (where two stranded satellites were retrieved and returned to Earth), but the majority of EMU uses occurred on the servicing missions of the Hubble Space Telescope. For those flights, two sets of EVA astronauts would venture out of the orbiter, thus requiring NASA to fly four sets of suits (along with repair parts). 41 EVAs using EMUs had been conducted out of the Space Shuttle airlock prior to the start of ISS assembly in November 1998. With the building of the ISS, Hamilton Sundstrand and ILC Dover refined the existing Shuttle EMU by making the suit modular. This allowed an EMU to be left on the ISS for up to two years and resized on-orbit to fit various crew members. The ISS EMUs also have increased battery capacity, the Simplified Aid For EVA Rescue (SAFER), improved cameras and radios, and a new caution and warning system. Another feature incorporated into the ISS suits is an additional battery to power heaters built into the glove, allowing astronauts to keep their hands warm during nighttime passages on each 95-minute orbit. Currently, the ISS EMUs and the Russian Orlan suits are used by crews of all nationalities on the International Space Station. The two EMUs are stored within the Quest Joint Airlock. Future use and replacement , NASA plans to use Exploration Extravehicular Mobility Unit (xEMU) system during Artemis program, derived from the spacesuit technologies used in the past. On June 1st, 2022, NASA announced it had selected Axiom Space and Collins Aerospace to develop and provide astronauts with next generation spacesuit and spacewalk systems to work outside the International Space Station, explore the lunar surface on Artemis missions, and prepare for human missions to Mars. Gallery