This article was originally published at The Conversation. The publication contributed the article to Space.com's Expert Voices: Op-Ed & Insights.

For 24 hours a day, seven days a week since November 2000, NASA and its international partners have sustained a continuous human presence in low-Earth orbit, including at least one American – a streak that will soon reach 25 years.

When viewed in the history of spaceflight, the International Space Station is perhaps one of humanity's most amazing accomplishments, a shining example of cooperation in space among the United States, Europe, Canada, Japan and Russia. But all good things must come to an end.

In 2030, the International Space Station will be deorbited: driven into a remote area of the Pacific Ocean.

I'm an aerospace engineer who has helped build a range of hardware and experiments for the ISS. As a member of the spaceflight community for over 30 years and a 17-year member of the NASA community, it will be hard for me to see the ISS come to an end.

Since the first pieces of the International Space Station were launched in 1998, the station has been home to significant research accomplishments across domains that include materials science, biotechnology, astronomy and astrophysics, Earth science, combustion and more.

Astronauts performing research inside the space station and payload experiments attached to the station's exterior have generated many publications in peer-reviewed science journals. Some of them have advanced our understanding of thunderstorms, led to improvements in the crystallization processes of key cancer-fighting drugs, detailed how to grow artificial retinas in space, explored the processing of ultrapure optical fibers and explained how to sequence DNA in orbit.

In total, more than 4,000 experiments have been conducted aboard the ISS, resulting in more than 4,400 research publications dedicated to advancing and improving life on Earth and helping forge a path for future space exploration activities.

The ISS has proven the value of conducting research in the unique environment of spaceflight – which has very low gravity, a vacuum, extreme temperature cycles and radiation – to advance scientists’ understanding of a wide range of important physical, chemical and biological processes.

Keeping a presence in orbit

But in the wake of the station's retirement, NASA and its international partners are not abandoning their outpost in low-Earth orbit. Instead, they are looking for alternatives to continue to take advantage of low Earth orbit's promise as a unique research laboratory and to extend the continuous, 25-year human presence some 250 miles (402 kilometers) above the Earth’s surface.

In December 2021, NASA announced three awards to help develop privately owned, commercially operated space stations in low-Earth orbit.

For years, NASA has successfully sent supplies to the International Space Station using commercial partners, and the agency recently began similar business arrangements with SpaceX and Boeing for transporting crew aboard the Dragon and Starliner spacecraft, respectively.

Based on the success of these programs, NASA invested more than US$400 million to stimulate the development of commercial space stations and hopefully launch and activate them before the ISS is decommissioned.

Dawn of commercial space stations

In September 2025, NASA issued a draft announcement for Phase 2 partnership proposals for commercial space stations. Companies that are selected will receive funding to support critical design reviews and demonstrate stations with four people in orbit for at least 30 days.

NASA will then move forward with formal design acceptance and certification to ensure that these stations meet NASA's stringent safety requirements. The outcome will allow NASA to purchase missions and other services aboard these stations on a commercial basis – similar to how NASA gets cargo and crew to the ISS today.

Which of these teams will be successful, and on what timescale, remains to be seen.

While these stations are being built, Chinese astronauts will continue to live and work aboard their Tiangong space station, a three-person, permanently crewed facility orbiting approximately 250 miles (402 km) above the Earth's surface. Consequently, if the ISS's occupied streak comes to an end, China and Tiangong will take over as the longest continually inhabited space station in operation: It's been occupied for approximately four years and counting.

In the meantime, enjoy the view

It will be several years before any of these new commercial space stations circle the Earth at around 17,500 miles per hour (28,000 kilometers per hour) and several years before the ISS is deorbited in 2030.

So while you have a chance, take a look up and enjoy the view. On most nights when the ISS flies over, it is simply magnificent: a brilliant blue-white point of light, usually the brightest object in the sky, silently executing a graceful arc across the sky.

Our ancestors could hardly have imagined that one day, one of the brightest objects in the night sky would have been conceived by the human mind and built by human hands.

Today marks the 25th anniversary of the first astronauts to arrive at the International Space Station (ISS)!

Floating above Earth, the ISS is a symbol of global cooperation, scientific discovery and the relentless curiosity that drives us to explore the cosmos.

It's not just a home in space — it's a laboratory, a classroom and a proving ground for technologies that may one day take us to Mars and beyond. From growing lettuce in microgravity to studying the effects of long-term spaceflight on the human body, the ISS is a hub of innovation that's reshaping our understanding of life off Earth.

Whether you're a seasoned space nerd or just dipping your toes into the vacuum of space trivia, this quiz will challenge your knowledge and ignite your imagination about the ISS.

So buckle up, adjust your mental thrusters, and prepare for liftoff, you're about to take a spin through the fascinating world of the International Space Station.

Try it out below and see how well you score!

In 1979, NASA's first space station, Skylab, fell to Earth. The intention was for it to crash into the Indian Ocean, but it survived deeper into the atmosphere than anyone expected. Once it finally broke apart, pieces of the lab reached as far as western Australia. The largest pieces of debris landed near the town of Esperance. Pieces of metal were falling from the sky, so town leaders had to do something about it.

They issued NASA a $400 citation for littering. The debt went unpaid.

It was technically a humorous jab, and in 2009, a California radio host raised the funds to pay off the debt. But it highlights how Skylab's fate became something of a joke in the 1970s and how we let a space station fall to Earth without having a replacement waiting in the wings.

And here we are again, nearly half a century later, facing the potential demise of another space station, without having a replacement ready.

At least this time around, however, NASA has something approaching a plan: get someone else to build it.

Since the first modules of the International Space Station (ISS) went up in 1998, over 4,000 scientific experiments have been conducted there. They have investigated everything from the effects of long-term spaceflight on the human body to the development of novel materials that can only be designed in microgravity.

Most importantly, we've learned how to operate in space for extended missions — what protocols and procedures we need in place, what kinds of systems tend to go wrong and when, and all the other institutional know-how that it will take to make us a true spacefaring species.

NASA plans to send the ISS into Earth's atmosphere in 2030, and it has no plans for a replacement — at least, not directly.

Currently filling NASA's time and budget is the design of the Lunar Gateway, a smaller version of the ISS designed to orbit the moon and serve as a waystation for extended surface missions. While the Lunar Gateway continues to receive congressional backing, its political future remains uncertain because it's a part of the overall Artemis program, which may not make all of its intended goals.

Either way, NASA is largely leaving behind operations in low Earth orbit. Instead, the space agency has developed a competitive system, called the Commercial LEO Destinations program, to help spur private investment in a space station. The idea is that NASA will fund private companies to create their own stations and then become one of many customers that will rent out time and space on those stations. That way, NASA will not have to do the heavy lifting of creating another iteration of the ISS.

There are several competitors in this area, including Orbital Reef, a joint venture led by Blue Origin and Sierra Space; and Starlab, a joint venture between Voyager Technologies and Airbus. But the clear front-runner is Axiom Space, which is nearly finished with the first module of its Axiom Station.

Axiom plans to launch that module on board a Falcon Heavy rocket and attach it to the ISS in 2027, when the company will begin getting accustomed to the world of space station care and maintenance. Then, presumably before 2030, Axiom will detach that module from the ISS and continue building it out, with a goal of reaching twice the usable volume of the current station.

Axiom already flew private astronauts to the ISS in June, for a practice run of handling ground-crew communication and the operation of scientific experiments.

If Axiom Space or any of its competitors succeed, then we will indeed have another torchbearer for our continuous presence in low Earth orbit, although this time, it will involve many more partners than the venerable ISS. And hopefully, this early public investment will pay off big time as private companies find many commercial uses for low Earth orbit, such as zero-gravity hotels for space tourism or mini-factories for producing specialty materials.

NASA has already seen success with a similar program, the Commercial Crew Program, which spurred and financed the development of the Falcon 9 rocket and Dragon spacecraft, both of which now serve both private and government projects. With a little luck, they will avoid the fate of Skylab and the decades-long gap between that station's ignominious end and the launch of the ISS.

At 1:32 am local time, an astronaut aboard the International Space Station (ISS) captured a striking view of the Nile River glowing across Egypt.

What is it?

The Nile River, often called the "lifeblood of Egypt," is the longest river in the world, stretching around 4,130 miles (6,650 kilometers) from its source in East Africa to its delta on the Mediterranean Sea.

Here, the lights along the river show the urban development along its banks, from Minya to New Bani Sewf City, ending in the glowing metropolis of Cairo at the Nile delta.

Where is it?

This photo was taken from the International Space Station, orbiting 259 miles (417 km) above our planet in low Earth orbit.

Why is it amazing?

For millennia, the Nile's predictable annual floods deposited nutrient-rich silt on its banks, enabling agriculture to flourish in an arid landscape and giving rise to one of history's most enduring civilizations. Ancient Egypt's cities, temples and trade networks were all anchored to this ribbon of water, and its cultural significance continues today.

Images like this one show how the reliance on the Nile changes geographically, as photographs from the ISS over time show changes in urban development across the river system.

Want to learn more?

You can read more about the International Space Station and the importance of rivers like the Nile.

China is making final preparations to launch its first space lab module — a prototype for a future space station — this week, state media reported.

The unmanned Tiangong 1 ("Heavenly Palace") module was scheduled to lift off between Sept. 27 and 30, but a forecasted cold weather front has pushed the targeted launch date back to Sept. 29 or 30. The module will launch on a Chinese Long March 2F rocket from the Jiuquan Satellite Launch Center in Northwest China.

Tiangong 1 is designed to connect with three spacecraft, Shenzhou 8, Shenzhou 9 and Shenzhou 10, which will launch later. The maneuvers will mark China's first dockings in orbit, and are planned to be carried out robotically. [Photos: China's First Space Station]

"This is a significant test. We've never done such a thing before," Lu Jinrong, the launch center's chief engineer, told state news agency Xinhua.

China originally planned to launch Tiangong 1 earlier, but the liftoff was delayed when a Long March 2C booster, similar to the Long March 2F, failed to reach orbit. Chinese officials investigated the accident and recolved the issue before pushing forward with Tiangong 1 plans.

Experts say the achievement will be a huge step forward for China's fledgling space program, and an important advancement toward the nation's goal of building a 60-ton manned space station by the year 2020.

The module will also carry medical and engineering experiments onboard.

Engineers conducted a full ground simulation of launch on Sunday afternoon (Sept. 25). Workers have made more than 100 upgrades to the launch site, and more than 170 technical improvements to the Long March 2F rocket, in preparation for Tiangong's mission, Cui Jijun, commander-in-chief of the launch site system and director of Jiuquan Satellite Launch Center, told Xinhua. These include a new updated computer center and command monitoring system at the Jiuquan Satellite Launch Center, as well as new systems to increase Mission Control's ability to adapt to changes that may occur during the mission.

"[The launch site] has the full conditions to conduct the Tiangong 1 mission," Cui said. [How China's First Space Station Will Work (Infographic)]

After the United States and Russia, China is only the third nation to independently launch humans to orbit. China's first manned mission, Shenzhou 5, occurred in 2003, and was followed by two more manned missions in 2005 and 2008.

You can follow SPACE.com senior writer Clara Moskowitz on Twitter @ClaraMoskowitz. Follow SPACE.com for the latest in space science and exploration news on Twitter @Spacedotcom and on Facebook.

The buzz out of Beijing is that China's Tiangong 1 space lab may fly sooner than expected, perhaps soaring into space by this month's end.

That might be the case, according to China space watcher Gregory Kulacki, a senior analyst and China Project manager at the Union of Concerned Scientists (UCS). The Tiangong 1 module ("Heavenly Palace 1" in Chinese) is not China's actual space station — nor will it be a part of the planned Chinese space station, he said.

Rather, the 8-ton experimental prototype is designed as a test bed for the technologies China will need for its future space station program, including docking technology. [Photos: China's First Space Station]

Over the next two years, China is projected to launch three missions to the Tiangong I space lab. The third — and possibly second — mission is expected to carry Chinese astronauts to live and work on the Earth-orbiting facility.

Kulacki has observed that at 8 tons, China's Tiangong 1 is much smaller than the 80-ton U.S. Skylab launched in 1973, or even the 22-ton core module of Russia's Mir Space Station, which launched in 1986. Right now, the International Space Station has grown to tip the scales at 450 tons.

Looking ahead, China currently plans to complete its 70-ton space station in the early 2020s.

"Coincidentally, that is about the time that the ISS is scheduled to be decommissioned. If both those things happen, China's space station will become the de facto new international space station," Kulacki explained in a recent post on UCS's "All Things Nuclear" website.

China's space ambitions

Just what are the ripple effects stemming from China’s push forward in space station construction?  Turns out it may be a bit of a Rorschach test.

There are observers that see China's playbook in space, as on the Earth, as a bid to become a world strategic power, not just a regional power.

Indeed, space for China is one piece — a significant piece, but just one — of the puzzle they are assembling, some observers say. Others contend that, when the puzzle is complete, it has China as No. 1 in the world when it comes to space, with no one else in second place.

Yet other analysts put forward that China’s Tiangong 1 is no big deal, a modest increment in space prowess. And there are those that wager China’s foothold in Earth orbit has military meaning. That’s counteracted by specialists who see a new window for U.S.-China space cooperation.

“Some members of Congress may try to use China’s progress in human space flight as an excuse to criticize the Obama administration’s space policy. Some U.S. defense analysts are likely to claim the orbiting space lab has a military purpose,” said UCS’s Kulacki.

But in reality, Kulacki told SPACE.com, Tiangong 1 is just a small step forward along the same path the United States and the Soviet Union crossed decades ago.

"Neither country discovered any practical military advantage from putting people in space. There is no indication China's human space flight program is motivated by the pursuit of military objectives, but even if it is, space professionals in the United States and Russia already know it is a fool’s errand," Kulacki said.

China's steps in space

The launch of Tiangong 1 is another modest step forward in China’s slow-paced but forward-moving human space flight program. [How China's First Space Station Will Work (Infographic)]

That’s the outlook from John Logsdon, a leading space policy expert and professor emeritus of political science and international affairs at the Space Policy Institute within George Washington University’s Elliott School of International Affairs.

Logsdon said that the Chinese space module will provide the target for gaining rendezvous and docking capabilities. Doing so somewhat mimics what NASA did during the two-seater Gemini program 45 years ago — making use of an Agena target to hone piloting skills, he said.

"But while all of Gemini's rendezvous attempts were controlled by the onboard astronauts, the Chinese are first attempting to do the link up with no crew aboard the Shenzhou 8 spacecraft. If China is successful in demonstrating automated rendezvous and docking, that will be a significant achievement," Logsdon said.

Unlike Agena, Tiangong 1 is also a small pressurized module akin to the Soviet Salyut space station of the 1970s and 1980s, and is scheduled to host at least two crews for several week stays during the Shenzhou 9 and 10 missions.

"So it is also a first step toward the larger space station that China is planning ten years from now," Logsdon said. "So while Tiangong 1 is a meaningful step for the Chinese in their plans to achieve comprehensive human spaceflight capability, it is not a threat to U.S. leadership in on-orbit capability."

The 'so what' factor

Given a new milestone in China’s space program, how best to gauge what this may mean for the United States?

That’s a much harder question to answer, said Joan Johnson-Freese, professor of national security studies at the Naval War College in Newport, R.I.

"Frankly, I don't think it will have much impact in the U.S. beyond the usual core of space enthusiasts and supporters," Johnson-Freese said. "With the U.S. economy in the state that it’s in, people worried about jobs and 401(k)s … and people feeling that Congress is focused more on politics than fixing things … I don't think what the Chinese are doing in space will register or have much impact among those who could make a difference to the U.S. space program." 

Johnson-Freese added: "And another question is what difference would space supporters like it to make? Support for the James Webb Telescope? Start of a new exploration program?  Expediting the Commercial Orbital Transportation Services program? What are NASA’s priorities?"

Powerful political signal

There are several points to consider regarding the imminent lofting of China's Tiangong 1, suggested Dean Cheng, a research fellow at The Heritage Foundation’s Asian Studies Center in Washington, D.C.

"The most important point is that this is developing docking techniques and technology which, in turn, means precision controls for thrusters and the like, which has obvious military/anti-satellite implications," Cheng said.

In political terms, hurling Tiangong 1 into Earth orbit, Cheng said, is another reminder that China intends to be a space player for the foreseeable future, including the realm of human spaceflight.

Just as China's naval aircraft carrier was launched soon after they criticized the U.S. for spending too much on defense, undertaking the Tiangong/Shenzhou 8 mission at about the same time as the U.S. space shuttle program ends "is a powerful political signal that China is ascendant, and the U.S. is descending," Cheng said.

Asian space race under way?

Yet another reflection is the extent to which China's space station initiative is going to spur intra-Asian space competition, Cheng continued. By launching a Skylab-type vehicle — even if significantly smaller — China is, nonetheless, going to set records for Asians in space, he said.

"In some ways, this will underscore the extent to which China is ahead of India and Japan. This will be layered atop ongoing tensions among them: Beijing-Tokyo (the Senkakus/Diaoyutai incident of last year) and Beijing-New Delhi (ongoing tensions about border demarcations),” Cheng said.

With New Delhi indicating an interest in anti-satellite capabilities, Cheng noted that Beijing's ability to sustain people in space, and associated military technology benefits — not to mention the expansion of their Tianlian data-relay satellite network nominally needed for piloted space telemetry — will be a sign of China’s edge over India in space.

Cheng’s forecast: “I think the next decade, depending on everyone’s economic development, may well see a heating up of the Asian space competition.”

Space race memories

There are those hungry for a walk down memory lane to a 1960s-like "space race" — this time between the U.S. and China — a state of affairs that could fuel America's space esprit de corps.

That idea appears to be a non-starter, suggested Roger Launius, senior curator in the Division of Space History at the Smithsonian Institution's National Air and Space Museum.

The Chinese have only flown three piloted missions since 2003 "and there are really no aggressive plans that I have seen, although there has been some reporting in the media about the possibility of a piloted Chinese moon mission. How real that is, I think, is an open question," Launius said.

Absent a serious effort by the Chinese, Launius doesn't think too many American leaders will be too concerned about increasing American funding for human spaceflight.

"Of course, having said that, if China landed on the moon, went to Tranquility Base, picked up our flag, brought it back and sold it on eBay, I think Americans would be very excited," Launius suggested.

There seems to be "enormous opportunity," Launius said, and also some "real concern" in the emergence of China as a space power.

"The opportunity comes from an increasingly capable China that might be enjoined in the international effort to create a beachhead in Earth orbit and extend human presence beyond LEO. The cooperative possibilities are intoxicating as we consider a hopeful and peaceful future exploring and using space," Launius said.

"The other side of that coin, of course, is the national security aspects of space technology," he said. "The rising capability of China has made American national security leaders nervous."

Leonard David has been reporting on the space industry for more than five decades. He is a winner of this year's National Space Club Press Award and a past editor-in-chief of the National Space Society's Ad Astra and Space World magazines. He has written for SPACE.com since 1999.