Fifty years ago, a Princeton physicist named Gerard O’Neill asked his students to help him come up with a plan for setting up settlements in space.

Just a few years later, O’Neill published the resulting vision for freestanding space colonies as a book titled “The High Frontier” — a book that helped inspire Amazon billionaire Jeff Bezos’ vision of having millions of people living and working in space.

Now the keepers of the “High Frontier” flame at the California-based Space Studies Institute are revisiting O’Neill’s original vision, with an eye toward updating it for the 21st century.

“The fact is, a lot has changed in the last half-century,” Edward Wright, a senior researcher at the Space Studies Institute, said today at the start of a two-day conference presented by the institute at Seattle’s Museum of Flight.

The experts and entrepreneurs attending this week’s meeting are surveying concepts that have spun off from the idea of O’Neill habitats, as well as NASA-led initiatives such as the moon-orbiting Gateway and the Artemis effort to send astronauts to the lunar surface by 2024. They’re also talking about strategies to turn O’Neill’s dreams of massive, enclosed space habitats — which some now see as stale fantasies — into economically viable realities.

“The biggest challenge for all of us in this room … is not engineering,” said John Blincow, a former airline pilot who is now president of the Gateway Foundation. “We’ve got brilliant engineers here. It’s economics.”

Blincow’s concept is a case in point: The Gateway Foundation’s Von Braun Rotating Space Station would be a 625-foot-wide space ring that looks as if it could roll right out of a scene from “2001: A Space Odyssey.” It’s meant to accommodate up to 400 people in low Earth orbit and offer amenities including restaurants, movie theaters and sports facilities.

Projected cost? $70 billion, Blincow says.

That sum may sound like a lot. But it’s less than the estimated $100 billion expense of building the International Space Station, which has the volume of a six-bedroom house. Bezos, the world’s richest individual, could cover the cost all by himself if he unloaded his Amazon stock all at once rather than selling it off a mere billion dollars’ worth at a time.

Bringing space costs down to earth

Visions of space settlement are getting a fresh look in part because of Bezos and other space-minded billionaires, such as SpaceX CEO Elon Musk and Virgin Galactic founder Richard Branson. SpaceX already has driven the cost of access to space down to levels that make the logistics of building orbital stations seem more doable, and Bezos’ Blue Origin space venture aims to do the same.

Al Globus, a longtime space settlement advocate whose resume includes a long stint at NASA’s Ames Research Center, figures that it would take 60 launches of SpaceX’s yet-to-be-built Super Heavy rocket to put the hardware for a 360-foot-wide rotating space station called Kalpana 2 into orbit. That’s a dramatic improvement over the tens of thousands of launches that NASA contemplated in the 1970s for a much more massive design known as the Stanford Torus.

Globus recommends starting even smaller. “A space hotel has requirements fairly similar to a space settlement,” he said. “So you can build a small hotel, which you could do with a single launch, and you could start gaining revenue. If your small hotel is successful, you build a bigger one.”

He argued that lower launch costs could bring the price point for space settlement closer to down-to-earth levels.

“If you take the most optimistic rumors floating around about the [SpaceX] Starship and so forth and so on, and you assume that the cost of the stuff and construction is no greater than the cost of transportation — which is a big if, by the way — then you can argue that it’d cost a couple about $5 million to move in,” he said.

Other concepts that won a share of the spotlight included “New Venice,” a multi-industry space outpost designed by University of Houston architect Suzi Bianco; and an expandable design presented by Skyframe Research’s Anthony Longman.

“We need to find an evolutionary approach so we can make it affordable,” Longman said. The Growth-Adapted Tensegrity Structures project, led by Texas A&M researchers and funded by the NASA Innovative Advanced Concepts program, calls for starting out with a small space station and gradually growing it into a rotating habitat capable of sustaining up to 8,000 people in Earth-level artificial gravity.

Where would the building materials for such space habitats come from? Some of today’s speakers talked up the prospect of harvesting resources from the moon or from near-Earth asteroids. Water ice is frequently mentioned as a key resource — not only because it can be melted down to slake a settler’s thirst, but also because it can be broken down into hydrogen and oxygen for rocket propellants.

“In that sense, water is the oil of space,” said George Sowers, a veteran space executive who is now an engineering professor at the Colorado School of MInes.

Dennis Wingo, CEO of Skycorp Inc., said the moon could yield resources ranging from regolith for building materials, to helium-3 for future fusion fuel, to sapphire for semiconductor substrates and high-quality glass. “There starts to be different things you can do,” he said.

Buzzing about blockchain and AI

But some of the hurdles to space settlement are still just as high as they were when O’Neill and his students came up with their “High Frontier” vision 50 years ago.

“We haven’t figured out how to privately or publicly finance long-term, high-risk, capital-intense projects,” said Chris Lewicki, co-founder of ConsenSys Space. He learned the truth of that last year when his Redmond, Wash.-based asteroid mining company, Planetary Resources, ran into financial trouble. After months of uncertainty, the company’s assets were acquired by ConsenSys, a blockchain studio.

Lewicki isn’t yet ready to unveil the business plan for ConsenSys Space, but he hinted that blockchain’s built-in security features could help overcome some of the financial hurdles. “What’s interesting there is the way that it allows you to connect disparate things in a more understandable way, in a more traceable way,” he said, “so that you could, for example, create a financial investment share community around a shared project.”

Blockchain wasn’t the only buzzworthy concept from the tech industry that came up today: To build a new home beyond Earth, space settlers will need all the help they can get from artificial intelligence, said Phil Metzger, a planetary scientist with the Florida Space Institute at the University of Central Florida.

“We can’t leverage ourselves more if we have to do everything, if we have to control all of the machines,” he said. “The key to making this all work is artificial intelligence and machine learning — having smarter machines so that we have more machines per person managing them.”