Giant in-space colonies like those depicted in these renderings by artist Don Davis –

– look fantastic and would clearly be places where many people would live if they existed today. The problem, of course, is that they do not exist and it’s difficult to convince people that it’s possible to ever build such gigantic habitats. But there are in fact ways to get from here to there.

When I fly into a big city and look out the window as the plane descends, I’m always amazed at just how enormous such places are. How could mere mortals create such a vast landscape of houses, buildings, skyscrapers, roads, bridges, harbors, and more? The answer, of course, is a city starts as a small settlement and over many decades the incremental efforts of thousands upon tens of thousands of people and their machines working in parallel day after day, year after year, create such massive metropolises.

Such a process can create cities in space as well. New Rome in orbit doesn’t have to be built in a day. We just need to get small “starter” settlements off the ground, so to speak.

That’s easy to say but what about the high cost of getting to space?

Fully reusable space transports like that being developed by SpaceX, Blue Origin, and other companies can bring down the  cost of getting to space by factors of 10-100. The cost of propellants is a less than a half percent of the cost of an orbital rocket launch. The rest of, say, the $60M cost of Falcon 9 goes for the vehicle, which currently is thrown away on each flight.

What about the detrimental effects of microgravity and radiation on human health?

Rotation of a habitat can provide artificial gravity and bulk materials such as water and structural metals can shield people in a habitat just as the atmosphere shields people on earth.

The toughest question is how to get started. When giant  habitats like those above were being designed in the 1970s, it was assumed that most of the material would be sent from the Moon. All of this would be paid for by huge investments from governments who would appreciate the construction of in-space solar power stations feeding energy via microwave to the earth.

Excavation activities on the Moon, space base solar power, and big government funding do not look likely to happen anytime soon, to say the least. Is there any other way to get space settlement underway?

Yes, it can still happen if the process can start small and pay its own way. Al Globus, who works as a contractor at NASA Ames Research Center in Mountain View, California, describes in a set of three documents listed below a plan for  small affordable space habitats in low earth equatorial orbit that will provide 1 g gravity and enjoy sufficient radiation protection for residents to live a healthy life. Space tourism will be a primary industry similar to the way many island economies on earth rely on tourism.

* Space Settlement the Easy Way, Al Globus and Stephen Covey, presentation at ISDC 2015, May 2015.
“This presentation shows how the results of the next two papers — “Space Settlement Population Rotation Tolerance” and “Orbital Space Settlement Radiation Shielding” — when combined suggest that small space settlements in equatorial LEO with little or no radiation shielding may be viable. Hopefully, this will be turned into a paper in the not-too-distant-future.”

* Space Settlement Population Rotation Tolerance, Al Globus and Theodore Hall, preprint, June 2015.
“This paper reviews the literature to find that space settlement residents and visitors can tolerate at least four, and proabaly six, rotations per minute to achieve 1g of artificial gravity. This means settlements can be radically smaller, and thus easier to build, than previously believed. Combined with the next paper on radiation shielding, the first space settlements can be two orders of magnitude less massive and closer to Earth than previous designs making launch from Earth practical.”

* Orbital Space Settlement Radiation Shielding, Al Globus and Joe Strout, preprint, May 2015.
“The major result of this paper is that settlements in low (~500 km) Earth ***equatorial*** orbits may not require any radiation shielding at all based on a careful analysis of requirements and extensive simulation of radiation effects. This radically reduces system mass and has profound implications for space settlement as extraterrestrial mining and manufacturing are no longer on the critical path to the first settlements, although they will be essential in later stages. It also means the first settlements can evolve from space stations, hotels, and retirement communities in relatively small steps.”

Globus answered questions about space settlements in a recent on line forum: A NASA Expert Is Here To Answer Your Questions About Orbital Settlements – Gizmodo.