Since ISS assembly of the station began, one of the necessary nuisances after a Space Shuttle Orbiter docked with the station was that the Shuttle crews couldn’t visit their friends inside the station right away.
The Orbiter’s docking port to the station was also their airlock to conduct spacewalks for ISS assembly and maintenance. So there were required changes in cabin and station pressures that required the Orbiter to stay sealed away for a time to complete any EVA work.
Complicating ISS work, the bulkier Shuttle EVA suits couldn’t be used with the only airlock at the time, in Zvezda.
Shuttle Atlantis would fix that issue by providing the station crews its first of three station EVA airlocks with the STS-104 mission, which launched on July 12, 2001.
The new airlock, named Quest, would provide resources for both Russian and American EVA spacewalks.
After Atlantis arrived on station two days after launch, the station and Shuttle crews exchanged some items before closing the hatch to allow the Orbiter’s cabin pressure to adjust for the coming day’s first spacewalk of the mission.
Quest consisted of two parts: An interior lock where space suits are stored and donned, and an outer lock where depressurization is made and where the spacewalkers leave and return.
Resources on the station were a premium, particularly the amount of air that is vented to space as part of an EVA. Quest was designed with external nitrogen and oxygen tanks that back-fill the station of any lost air to minimize that impact.
The first mission was simply to get Quest removed from the Shuttle’s payload bay. But rather than use the station’s robotic arm, this procedure was done by Canadarm2, installed on the previous assembly mission.
The Shuttle’s arm would be used by the spacewalkers on the first EVA crew, who stood on the arm using a foot platform, engaged in removing protective coverings on the airlock, seal covers for connections of the air replenishment tanks, and detaching Shuttle power from the airlock’s heaters used to keep the module at habitable temperatures before it was attached to the station.
Once the airlock was berthed, a final step on EVA #1 was to connect a power line from the airlock to the station.
The second and third EVAs would install one set of nitrogen and oxygen tanks. The second EVA was made through the Shuttle’s airlock, and installed the first two of four tanks.
The third and final EVA began from the new airlock, installing the last two tanks, covering up the now-unneeded grapple hooks, and installing additional handrails for future EVAs.
The next assembly mission was yet another station airlock–but this one would be installed in the Russian way: Through an clever modification of an unmanned spacecraft that normally carried pressurized cargo, fuel and air.
Next: Assembly 4R.