The world's space agencies (at least those involved in the International Space Station) popped the Champagne corks this week to celebrate 20 years of continuous human occupation of the orbiting laboratory.
It is quite an achievement, although the figure for continuous human presence in orbit might have been even longer if a lack of funding and general decrepitude had not sent Russian Space Station Mir back to Earth shortly before the first 'nauts took up residence aboard the ISS.
The history of the ISS prior to the arrival of Expedition 1 is chequered. One of its origins was as Space Station Freedom, driven by a desire to reassert US space superiority in the face of the succession of Salyuts being lofted by the USSR. Where Russia's stations were crewed by three (aside for changeovers), Freedom would host six. It would feature a repair shop for satellites, laboratories from the US, Japan, and Europe, and even its own Crew Return Vehicle for evacuation when the Shuttle wasn't present.
Things didn't work out that way, and despite repeated redesigns the budget remained stubbornly high. Lofty plans were scaled back, and even then the entire project infamously escaped Congressional cancellation by a single vote. In the meantime, the USSR reached its own pinnacle with the modular Mir Space Station.
The collapse of the Soviet Union resulted in an opportunity for the beleaguered station. The Russians were invited to join the project and the Space Shuttle (and NASA astronauts) spent time at Mir.
Russia was also deposited squarely in the critical path for the revised space station design. It would be contributing two key modules: Zarya (aka the Functional Cargo Block), which handled power and propulsion; and Zvezda, which dealt with life support and, was initially planned for Mir 2, bore a distinct resemblance to the Salyut series of old. The US launched Node 1 (Unity) to connect the US and Russian segments together.
The first crew, consisting of NASA astronaut Bill Shepherd (on his fourth and last flight) as well as cosmonauts Yuri Gidzenko and Sergei Krikalev, arrived at the three module ISS on 2 November 2000 at 9:21 UTC. Gidzenko and Krikalev were both Mir veterans while Shepherd had only flown on the Shuttle.
Shepherd's first Shuttle mission was the infamous STS-27 in 1988, which suffered substantial damage to its heat shield during launch. He had also been on the STS-88 crew, which had carried the US Unity module to the ISS.
Expedition 1 marked the start of continuous ISS occupation, with the trio of 'nauts seeing the arrival of the first set of solar arrays and the US Destiny laboratories during their stint to March 2001. The first six expeditions stuck with the core crew complement of three (increasing during Shuttle visits and handovers) during assembly until the Columbia disaster removed the Space Shuttle from the equation and the crew had to be reduced to two from 2003.
It took until 2006 before the crew size was increased again and by the end of the decade the station was playing host to crews numbering six, the most that the two Soyuz lifeboats could safely return to Earth.
The station currently has three crew members, a figure that may increase to seven following a successful launch of four astronauts aboard the first operational mission of SpaceX's Crew Dragon later this month.
While the ISS crew is ostensibly an international affair, the lion's share of crew places has gone to the US, which has footed much of the bill of the outpost, and Russia. Agencies that have contributed modules, such as ESA and JAXA, have also flown astronauts while there has been the odd tourist or two over the years. Canonical's Mark Shuttleworth took a trip in 2002 and game developer Richard Garriott took his turn in 2008.
The current visitor count stands at 241 individuals, a figure that will inexorably rise before the eventual demise of the ISS in the 2028-2030 time frame.
The continuous occupation of the ISS for the last 20 years, with crews from very different international backgrounds and agencies, remains a heartening thing despite the occasional leak, iffy plumbing and patchy science when crew numbers drop. The station has weathered problematic resupply vehicles and fluctuating international tensions.
It is, however, unlikely to see another two decades before funding and the will to keep it in orbit dry up in the face of deeper space ambitions, which means a fiery and eventually watery end. ®
The ISS is well documented both in paper and digital form. John E Catchpole's The International Space Station: Building for the Future was a useful resource, as was Mike Mullane's Riding Rockets, which contains an account of the hair-raising STS-27 mission. Grujica S Ivanovich's Salyut: The First Space Station and David M Harland's The Story of Space Station Mir also provided useful accounts of Russian hardware prior to the ISS.