Atlantis lifts off with Quest airlock; station finally has its own door to open space
By the summer of 2001, the International Space Station had a laboratory but no dedicated front door for spacewalks. On July 12, Space Shuttle Atlantis launched at 09:04 UTC on mission STS-104, carrying a 6.5-ton steel-and-aluminum chamber called the Quest Joint Airlock in its cargo bay. Over three spacewalks totaling sixteen and a half hours, astronauts Michael Gernhardt and James Reilly bolted the airlock into place and outfitted it with gas tanks and handrails. Quest became the station's main hatch to open space, usable by both American and Russian spacesuits.
Quest was built by Boeing at Marshall Space Flight Center, and its installation ended NASA's reliance on shuttle airlocks for station spacewalks, letting American astronauts exit directly from the ISS itself. STS-104 also closed out an era: it was the last shuttle mission flown with only five crew members. All succeeding missions had six or seven crew members, with the sole exception of the final mission, STS-135, which flew with four.
QWhat exactly did Atlantis's crew bolt onto the outside of the new airlock?
A spacelab pallet carrying four High Pressure Gas Assembly containers, essentially external tanks of compressed gas mounted to the airlock's exterior before it even reached the station. These tanks supplied the air and oxygen the Quest Airlock would need to repressurize after every future spacewalk, without which the module would have been a sealed shell rather than a functioning door to space. Astronauts had to install and connect this hardware by hand during the mission's spacewalks, working outside while the tanks were still attached to the pallet.
QWhy couldn't later shuttle missions match STS-104's crew size?
The physics of docking with an increasingly massive International Space Station left less margin for extra weight, and a shuttle full of astronauts, their supplies, and their gear adds up fast. STS-104 flew with five, the last mission ever to do so. Every flight after it carried six or seven astronauts, with a single exception: STS-135 in 2011, the shuttle program's final flight, which flew with just four.
QWhose spacesuits could actually use the new airlock?
Both American and Russian designs. The Quest Airlock was engineered to accommodate NASA's EMU suits as well as the Russian Orlan suits, making it a genuinely bilateral piece of hardware on a station built by two former space rivals. Before Quest existed, spacewalkers depended on whichever shuttle happened to be docked, which meant the station itself had no standing capability of its own. After STS-104, the ISS could support spacewalks in either suit design at any time, independent of which spacecraft was parked outside.
