Long ago, in a dreamier era, space stations were imagined as portals to the heavens. In the 1968 movie "2001: A Space Odyssey," the huge structure twirled in orbit, aesthetically sublime, a relaxing way station for astronauts heading to the moon. It featured a Hilton and a Howard Johnson's.

The international space station of the 21st century isn't quite as beautiful as that movie version, and it's not a gateway to anywhere else. It's a laboratory focused on scientific experiments. Usually there are six people aboard. When they leave, they go back home, down to Earth. Three came home Wednesday, landing in Kazakhstan.

A support diver is seen during a training exercise with astronauts inside the Neutral Buoyancy Laboratory at the Lyndon B. Johnson Space Center last month
A support diver is seen during a training exercise with astronauts inside the Neutral Buoyancy Laboratory at the Lyndon B. Johnson Space Center last month in Houston. Astronauts tapped for service on the International Space Station train under water at the laboratory. (Washington Post/Ricky Carioti)

The space station circles the planet at an altitude of about 250 miles. Faint traces of atmosphere exert a drag on it, so the station must be boosted regularly to stay in orbit. In the grand scheme of things, the space station simply isn't very far away. The station has a phone number with a Houston area code.

Advocates for human space exploration insist that NASA must think bigger, developing missions beyond Low Earth Orbit, into deeper space — perhaps back to the moon, or to an asteroid, and certainly to Mars eventually.

But NASA has been struggling for years to square ambitions with budgets. The space station is widely praised as an engineering marvel, but it didn't come cheap. The United States has poured close to $100 billion into the program and is contributing about $3 billion a year to the station's operation. Space policy experts warn that, without a significant boost in budget, NASA will not be able to keep running the station and simultaneously carry out new, costly deep-space missions.

Japanese astronaut Takuya Onishi is helped with entry into his Extra Vehicular Activity suit last month by EVA tech James Lemon, right, inside the Neutral
Japanese astronaut Takuya Onishi is helped with entry into his Extra Vehicular Activity suit last month by EVA tech James Lemon, right, inside the Neutral Buoyancy Laboratory at the Lyndon B. Johnson Space Center in Houston. Astronauts tapped for service on the International Space Station train under water. (Washington Post/Ricky Carioti)

The United States and its partners need to make a tough call: Keep the station flying? Or bring it down?

Boeing, the prime contractor, is trying to prove that the station's components can hold up through at least 2028. Three years ago, Congress extended funding for the station through 2020, and NASA's international partners — Russia, Japan, Canada and the European Space Agency — have made a similar commitment. But behind the scenes, NASA officials are working to persuade the White House to make a decision, pronto, to keep the orbital laboratory flying after 2020.

The alternative is to crash the massive structure into the South Pacific.

The decision needs to be made in 2014, said William Gerstenmaier, the top NASA official for human spaceflight.

A view of the Russian Zvezda Service Training Module inside the Space Vehicle Mock-Up Facility at the Lyndon B. Johnson Space Center in Houston. The
A view of the Russian Zvezda Service Training Module inside the Space Vehicle Mock-Up Facility at the Lyndon B. Johnson Space Center in Houston. The facility is home to a full-size mock-up of the International Space Station used for training. (Washington Post/Ricky Carioti)

Companies such as SpaceX and Sierra Nevada, which are competing for a NASA contract to carry astronauts to the station, need to know that their market isn't going to vanish in 2020, he said. Scientists, pharmaceutical companies and other organizations that do zero-gravity experiments also need to know soon whether "there's a horizon for the station beyond 2020," he said.

As the decision makers in the U.S. government discuss the fate of the orbital laboratory, they face tough questions about the future of NASA in a broader sense. The dean of space policy analysts, John Logsdon, former director of the Space Policy Institute at George Washington University, said of NASA: "It was not given a strategic purpose after Apollo. Why does it exist? What do you want to do?"

A helmet and gloves of an astronaut&apos;s Extra Vehicular Activity suit rest on the pool deck inside the Neutral Buoyancy Laboratory at the Lyndon B.
A helmet and gloves of an astronaut's Extra Vehicular Activity suit rest on the pool deck inside the Neutral Buoyancy Laboratory at the Lyndon B. Johnson Space Center in Houston, Texas. (Washington Post/Ricky Carioti)

Although it's true that the international space station (ISS) never strays far from Earth, cosmically speaking, it has the virtue of showing what life in space is really like. The PowerPoint version of space travel is always easier than the real thing. There are things that reveal themselves only in zero gravity.

"Stiction," for example — the way delicate materials stick together without gravity to tug them apart. There's no way to replicate that on Earth.

Dust has no urge to settle down, and so it clogs air filters faster than engineers had once anticipated. Bacteria grow in odd corners and crannies. Mysterious disks of zinc oxide have stopped up a water line, defying explanation.

In this photo taken in December 2006 by the space shuttle crew, astronauts Robert Curbeam (United States) and Christer Fuglesang (Sweden) work to attach a
In this photo taken in December 2006 by the space shuttle crew, astronauts Robert Curbeam (United States) and Christer Fuglesang (Sweden) work to attach a new truss segment to the International Space Station and begin to upgrade the power grid. (NASA)

In theory, equipment has its own storage space. But that's not how the place looks in real life. There are laptop computers everywhere and tools Velcroed to the walls. It's cluttered. New crews famously have to go on treasure hunts to find things that have vanished.

Mundane problems such as clogged filters and mold formation provide lessons for an eventual human mission to Mars. On a Mars voyage there would be no way to turn back halfway, so engineers have to understand in advance what could go disastrously wrong.

The Apollo model of spaceflight puts the emphasis on destination; the space station model puts the emphasis on simply living in space, in that alien environment.

"For folks like me, who consider Apollo a poor model for the future of human exploration, the ISS is the essential demonstration site and steppingstone for a sustained future in space with humans," senior NASA scientist Harley Thronson said.

Space is perhaps the most dangerous place that people have ever lived continuously. A stray pebble or piece of space junk could puncture the shell of the structure and lead to rapid depressurization. Day in, day out, ammonia is a concern. It is critical to the station's cooling system, but it is also highly toxic.

"Ammonia will kill you in one breath," said Chris Hadfield, perhaps the most famous astronaut of the 21st century.

Hadfield knows that most people aren't paying attention to the men and women passing by overhead. That's another striking feature of life in space: It's relatively anonymous. You can go around the world 16 times a day, but few of the 7 billion people down below will ever know your name.

Many astronauts do their best to connect to the earthlings. Astronauts tweet and update Facebook pages. A few months back, Hadfield made a humdinger of a music video — covering David Bowie's song "Space Oddity" — that has more than 17 million views on YouTube.

Hadfield also made videos about everyday life in space. Bodily fluids go in strange directions. Your vision blurs, your nose feels stuffy, and you lose your sense of taste.

Water is so dominated by surface tension that it can migrate around your scalp and over your face, as if seeking a hole to invade.

In zero gravity, a flame burns spherically — a ball of fire.

Experiments on the ISS have touched on fluid dynamics, crystal formation and changes in bacterial virulence. Next year, 20 to 60 rodents will come aboard as research subjects. And the astronauts themselves are under the microscope, revealing the effects of weightlessness and space radiation. NASA and the Russian Federal Space Agency plan to send astronauts to the ISS for an entire year, starting in the spring of 2015.

Astronauts talk about the transcendent experience of seeing the world without political borders, with the thin blue line of the protective atmosphere. Hadfield would often know where the station was over the surface, simply by checking out the color of the light shining up through the cupola, the nest of windows facing the planet. Usually the light would have a blue cast, from the ocean below. If orange, that would usually mean the station was passing over the Sahara. If red, that would be the signal of the Outback.

A typical work shift lasts 12 hours. Astronauts get one day off a week, a respite from the grind of chores and scientific experiments. Satellite TV reception in space is poor, oddly enough. Smoking and drinking are not allowed. Bodies deteriorate without gravity, and so the astronauts exercise constantly, at least two hours a day.

Astronaut Nicole Stott said she has never slept better in her life than she did in space. No pillow necessary. There are no pressure points on the body. A chronic pain in her arm simply disappeared forever. The only problem with space sleep is that the body naturally forms a zombielike pose, with arms dangling forward.

"It's kind of scary," she said.

Saturdays are cleaning days. Every surface is essentially a floor, gathering dirt, flakes of skin, stray drops of sweat and bits of food. (Jam has a diabolical tendency to launch itself off toast.)

"What come in really, really handy are baby wipes," astronaut Doug Wheelock said.

He also likes the Russian towels. They have a lot of texture, ideal for rubbing down a body. Without a shower, dead skin stays put and grows itchy.

"A towel with some texture on it is like heaven, because you can get all the dead skin off you," Wheelock said. "It feels so good, psychologically."

Astronaut Mike Fincke spent his down time reading science fiction, including the Arthur C. Clarke novel "2001."

Picture it: A man in a space station reading a novel about people on a space station. That closed a cultural loop.

"We take these dreams and make them real," Fincke said.

The international space station is another step in what space policy analyst Dwayne Day has called the Von Braun Paradigm, after Wernher von Braun, the German rocket scientist who, after World War II, came to America and became a leader of the U.S. rocket program.

In an influential series of stories in Collier's magazine from 1952 to 1954, von Braun and other space visionaries foretold an era in which human beings would conquer space. Von Braun imagined a steppingstone approach that included orbital flights, a space shuttle, a space station, a voyage to the moon and, finally, a human landing on Mars.

But the order of attack played out differently. The U.S. raced to the moon to beat the Soviets, who had their own lunar aspirations. NASA then wanted to build a space shuttle and a space station, but President Richard M. Nixon told the agency it couldn't do both. NASA went with the shuttle.

After aides mentioned to President Ronald Reagan that the Soviets had a space station, named Salyut, he decided that the United States needed one, too. In his 1984 State of the Union Address, he vowed to build a space station within a decade. "We can follow our dreams to distant stars, living and working in space for peaceful, economic and scientific gain," Reagan said.

Early estimates put the construction cost at $8.8 billion, but the government spent roughly that much simply designing the laboratory on paper while Congress debated whether to build it, said Howard McCurdy, an American University professor of public affairs and author of "The Space Station Decision."

The collapse of the Soviet Union created the final incentive to go forward. U.S. officials worried that Russian rocket scientists would go to work for rogue nations, spreading missile technology. In 1993, the United States and its allies brought the Russians into the fold for what would now be called the international space station. The international agreements ensured that the funds would keep flowing to the project despite changes in administrations and turnover in Congress.

Russia launched the first module in the fall of 1998. After more than 100 rocket and space shuttle launches to ferry components to orbit, and an astonishing 160 spacewalks, the orbital laboratory — as broad as a football field, including end zones — was finally finished in 2011. The ISS is modular, with one main truss lined with protruding elements and framed by symmetrical solar arrays, the whole thing rather insectoid, like something that would make a buzzing sound if a tiny version flew by your ear.

During a deployment of solar arrays in 2007, one of the arrays suffered a tear. Astronauts on the station and engineers in Houston scrambled to come up with a solution, pressed for time before the array disintegrated. In an emergency spacewalk, astronaut Scott Parazynski crawled to the remote end of a boom — farther from the air lock than any astronaut had ventured — and repaired the tear with makeshift "cuff links."

"It was definitely a Superman moment," said Mike Raftery, a top station official with Boeing.

A sociological truth has emerged from the international effort: American engineers are more likely to try to finesse a structure, to make it as lightweight and as efficient as possible, while Russians build things stout.

Mike Suffredini, the NASA program manager for the space station, said the station proves that in-orbit construction is possible, and he noted that no component has had to come back to Earth for retooling.

Said McCurdy: "It's one of the greatest engineering achievements in the history of the world. It ranks with the pyramids."

Logsdon, the policy analyst, said the station is a marvel, but he said it hasn't yet proved it was worth the investment. The science has been going full speed only for a couple of years, so it's too soon to make that judgment, he said.

"It's an awfully expensive engineering demonstration," Logsdon said. "If that's all it is, that's a hell of a price to pay."

Gerstenmaier, the NASA official in charge of human spaceflight, said of the station's cost: "We're in the process of proving now whether it's worth it or not. It's going to take a little while to see if these researchers will embrace this facility."

The ISS almost cost one human life. Italian astronaut Luca Parmitano nearly drowned in space this summer. The astronaut, who represents the European Space Agency, was spacewalking outside the station on July 16 when he felt water on the back of his head. It didn't seem to be coming from his water bottle. It didn't feel like sweat. And it was increasing — and migrating, around his head, into his ears, around his nose, doing all the strange things that water does in zero gravity.

Spacewalks are exquisitely choreographed and are not supposed to include surprises. The script for Parmitano's spacewalk ran to 72 pages. Astronauts go through a 500-step process simply putting on their spacesuits, which function like miniature spaceships, with elaborate life-support gear and an emergency jet pack. An astronaut on the ground will continuously talk to spacewalkers to ensure that they are feeling well, thinking clearly. But now here was Parmitano telling Houston that his helmet was filling with water.

Parmitano's account on his blog is harrowing:

"The water has also almost completely covered the front of my visor, sticking to it and obscuring my vision. . . . [T]he Sun sets, and my ability to see — already compromised by the water — completely vanishes, making my eyes useless; but worse than that, the water covers my nose — a really awful sensation that I make worse by my vain attempts to move the water by shaking my head. By now, the upper part of the helmet is full of water and I can't even be sure that the next time I breathe I will fill my lungs with air and not liquid."

He lost his sense of direction. Where was the air lock? He couldn't even see the handles the astronauts use for maneuvering. He tried to contact fellow spacewalker Chris Cassidy — all spacewalks are tandem operations, for precisely this sort of situation — but he couldn't hear him.

Then he recalled that his safety cable could be recoiled, and the gentle tug of that mechanism signaled the direction back to the air lock. He gradually felt his way there but still had to go through the laborious process of re-pressurization and reentering the station. NASA video captured the arduous efforts of Parmitano's crew mates as they removed his helmet and toweled up the rogue water.

NASA is still investigating where the water came from. Early evidence is that the spacesuit's cooling system malfunctioned.The incident illustrated the obvious fact that there is nothing routine about life in space — that even after nearly five decades of spacewalks, and even with elaborate safeguards, a failure mode could lurk within the American spacesuits.

As Parmitano put it on his blog: "Space is a harsh, inhospitable frontier. . . . The skills of our engineers and the technology surrounding us make things appear simple when they are not, and perhaps we forget this sometimes. Better not to forget."

Hadfield, who had left the ISS two months earlier, had a succinct description of what happened to Parmitano: "We just about killed him."

Hadfield came back to Earth in May, retired from the astronaut corps — he had been a Canadian government employee for more than three decades — and retreated to his summer cabin on an island in the St. Clair River, which flows out of Lake Huron between Michigan and Ontario.

He can stand on his dock and watch the space station pass overhead. When you're an astronaut, you keep track of it and know when it's going to be visible. The best views are shortly after sunset.

"The station suddenly glows yellow, red, then winks out dark," he said. "It's really dramatic on board, and it's really beautiful to see it from here. It just echoes within me."

Is there an aesthetic, even spiritual justification for spaceflight? So often, NASA officials describe the space station in practical terms, as a way of developing new technologies and expanding the economic sphere of the human race. But for someone like Hadfield, space travel offers humanity something that goes beyond any commercial or scientific utility.

"Station" — Hadfield often refers to it that way, as if it's a proper name — "is so much more than some remote laboratory where some small number of people and robots are doing something that no one knows about. Station is so much more than that. It is our first great human outpost in space. It is our way of seeing our world that's unprecedented in the history of the human species. It's an amazing platform for human self-discovery."

Conceivably, NASA could lease the station to some private, commercial operation, but it is hard to imagine who might want to take up the cost of operating it. And all spacecraft get tired and creaky with age. Space is a harsh environment. Metal fatigue is inescapable, due to the expansion of the structure as the station moves in and out of sunlight.

So even if the station's life is extended beyond 2020, it is coming down, eventually. NASA could try to salvage a piece here and there, but there are no plans to deconstruct it, so the controlled de-orbit will be a spectacular, fiery event. Too big to burn up completely, the station will crash somewhere in the open water of the South Pacific.

It will be perhaps the most expensive man-made object that human beings have ever intentionally destroyed. This vision of the future will sink to the bottom of the sea, ending another chapter in the history of what people used to call the Space Age.