ORLANDO, Fla., Oct. 30 (UPI) -- The 20th anniversary Saturday of humans living aboard the International Space Station spotlights the global cooperation and scientific discoveries that benefit all people, according to astronauts and others involved in missions there.
NASA and space agencies around the world are using the milestone to underscore achievements in space since the end of deep-space crewed missions in the 1970s and the space shuttle program in 2011.
Those who participated in space station construction find it hard to believe it has been inhabited for two decades, former astronaut Michael López-Alegría said. He has been to the orbiting platform three times and was the last person to visit before permanent missions started in 2000.
"After so many years, it's still in very good shape," López-Alegría said. "The ISS is the most audacious and complex construction project ever undertaken in space. It's pretty amazing that everything fit together perfectly and it all works so well."
Without the space station, humanity may be lacking key knowledge about space radiation, microgravity effects on people and life-support systems for long-term space visits, López-Alegría said. And, he said, living in a relatively low Earth orbit is a crucial step toward missions to the moon and Mars.
"The space station is an integral part of space exploration," López-Alegría said. "We still haven't been able to build reliable life-support systems for a lengthy mission to Mars, such as carbon dioxide scrubbers to keep air breathable for long periods without replacements. The space station is the best place to test things like that."
During his missions to help build and command the space station, López-Alegría amassed 67 hours, 40 minutes on 10 spacewalks, a record for NASA surpassed only by Russian cosmonaut Anatoly Solovyev at 82 hours, 22 minutes during 16 spacewalks.
Cooperation with Russia
NASA and Russia cooperated on the space station project after the two nations operated orbiting laboratories -- the U.S. SkyLab, occupied for just 24 weeks with gaps between three missions, and Russia's Space Station Mir, occupied with two short gaps for 12 1/2 years.
NASA has had hundreds of people supporting the ISS program at different times, said Robyn Gatens, the agency's acting director for the space station, including mission controllers in Houston and Moscow.
The orbiting research complex, which spans the length of a football field, is equivalent to a five-bedroom home with a gym, two bathrooms and a 360-degree bay window -- the cupola -- that allows views of Earth. Large arrays of solar panels power its systems, while liquid propellant rocket engines keep it from losing altitude.
The space station, which cost more than $150 billion to build and costs NASA over $3 billion annually, flies at more than 250 miles above the Earth at over 17,000 mph.
More than 240 people from 19 nations have visited the space laboratory and living quarters, with over 100 nations sending research or educational projects.
"It's an amazing accomplishment, just the continuous presence on a complex international platform like this," Gatens said. "That we've been able to make it look easy when it's not is a tremendous feat."
The biggest research accomplishments on the space station have been related to health, medicine and materials, she said.
"We've learned a lot about bone loss and immune system depression with astronauts on board," Gatens said. "We've used that knowledge to better understand osteoporosis on Earth, and how cancer cells behave."
A mission aboard the space station in 2004 proved that astronauts could use sophisticated ultrasound equipment in space.
Retired astronaut Leroy Chiao, commander of that mission, became the first person to vote in a U.S. presidential election from space. Astronaut Kate Rubins also cast her ballot from the space station Oct. 22.
NASA also noted that the space station contributes to the study of the Earth's geology, oceans, farms and glaciers. Astronauts worked on improvements in growing vegetables in space, confirmation of beliefs about cosmic rays and a greater understanding of how fire behaves in space.
Recent research includes the construction of human tissue in microgravity, with a goal to build entire human organs.
The space station has provided many opportunities for dramatic, attention-getting spacewalks over the years. The longest one, by Jim Voss and Susan Helms at 8 hours, 56 minutes, took place as astronauts pieced it together in 2001. Astronauts Christina Koch and Jessica Meir conducted the first all-female spacewalk in October 2019.
Other highlights at the space station include astronaut Scott Kelly's year-long mission with Russian cosmonaut Mikhail Kornienko. They were launched March 27, 2015, and returned March 1, 2016. The lengthy stay was intended to allow study of Kelly's health during and after the mission to help prepare for deep-space exploration of the moon and eventually Mars.
Created in sections
Much of the space station was carried in sections from Florida by the space shuttle, which also ferried crews of five to seven people there on a regular basis. That meant more than a dozen people on board at times.
When the shuttle program ended in 2011, the smaller Russian Soyuz capsule -- launched from Russia's spaceport in Kazakhstan -- was the only way for people to reach the space station, two or three people at a time. But NASA plans to launch four astronauts to the space station in November aboard SpaceX's newly certified Dragon capsule.
The agency anticipates the space station will have a useful lifespan until 2030, although that date isn't necessarily firm, Gatens said.
"We've analyzed the life of the parts of the space station to 2028," she said "We're about to update that through 2032. ... So far, we don't see anything that is failing or wearing out."
Going forward, NASA wants private companies to build orbiting laboratories, living quarters or even space hotels.
Houston-based Axiom Space, for example, plans to launch a private module to attach to the space station by 2024. After that, Axiom wants to add more private modules, eventually separating them from the space station.
At some point, according to the space station's decommissioning plan, NASA will decide to repurpose parts of it or let it burn it up in the atmosphere and have any remaining chunks fall into the Pacific Ocean.