What’s the motivator for a permanent human presence off-Earth? There have been many suggestions, most of them a bit cart-before-the-horse. Let’s have a look at a few historical suggestions that get recycled uncritically on the Web.
(1) “It’s a human imperative”
‘Wanderlust’. The desire to see over the horizon and seek fortune or failure on one’s own terms. We could get there using our feet, wits and ingenuity. That millennia long dispersal of tribal peoples, driven by the desire for new unoccupied territory, has been replaced by modern explorers who go for the sake of going. Such explorers want to go back home, if the journey doesn’t kill them. For example, Edmund Hillary didn’t want to relocate to the summit of Mount Everest. Most of the Solar System is colder and more desolate than anywhere on Earth. Sending robots in our stead, as our explorers, makes a lot of sense – for now. Eventually we will be able to go in person and maybe even remake those wastelands into something more hospitable. But for many space-minded people on planet Earth, there’s nothing to be gained by actually moving to the moons of Jupiter. High definition video and virtual reality are sufficient for most space-fans.
(2) Population Relief
Prior to the Demographic Transition – birth rates dipping lower than death rates, as they have for most countries – the ‘Population Explosion’ seemed inexorable. In the late 1960s and early 1970s, this led Gerard O’Neill to pose a class exercise to his physics students: what can we do about the Population Explosion? They very quickly imagined vast “Space Cities”, built from Moon-mined material, for what seemed reasonable prices using just 1970s technology. Exponential growth meant, so they argued, that more people would eventually be able to live “Off-Earth” than on it, allowing Earth to be gradually depopulated to half a billion or so, with most humans living in space. [Addendum: O’Neill’s 1974 paper “The Colonization of Space” makes this argument seem quite reasonable.]
But what’s the pay-off for people *currently* living on Earth? Why should they invest trillions to build O’Neill’s Space Cities? The argument was [from the 1975 NASA Ames Study] that the Space Colonists would build and sell Solar Power Satellites, and finance their Space Cities with the proceeds. Unfortunately the economics, using 1970s technology, just doesn’t make sense. One key step in constructing the first City (“O’Neill Island One”) was the establishment of a 2,000 person “Construction Shack” to then build the Space City. A single 10,000 person Space City masses about 10 million tonnes, while a Solar Power Satellite masses about 10,000 tons per gigawatt of power delivered to the ground. The number of Solar Power Satellites that could be made by a dedicated Construction Shack makes the Space City seem superfluous. Run as a commercial venture, the Construction Shack alone seems sufficient for building Solar Power Satellites.
Simply put Space Cities of the O’Neill variety are rather exotic housing estates. Of themselves, just like housing estates, they have no intrinsic resources or services that they can uniquely supply. If space commerce develops to the point that Solar Power Satellites can be made for prices competitive with ground-based energy sources, then Space Cities can begin to be contemplated, though exactly how they would be marketed is an exercise for the reader. The growing interest in “Sea-Steading” on Earth does suggest “Space-Steading” may follow, but like its maritime version, it’ll be as an elite retreat, not a relief valve for Earth’s masses.
(3) Space Mining
Asteroid mining makes a lot of sense, but needs an early market to give it a leg-up. For virtually everything used on Earth it’s easier to mine it on Earth than on an asteroid – for now. Advancing autonomous spacecraft, robotics and zero-gee manufacturing, make the prospect of commercially viable asteroid-mining for anything valuable enough closer than ever. However, one early market, presently targeted by actual Asteroid Mining companies (!) is bulk volatiles for use by other space activities (including proposed human activities.) A very early market is an in-space supply of topping-up propellant for use of the flotilla of satellites in geosynchronous orbit. Once 3-D manufacturing in zero-gee matures, satellites will be made-to-order in space, very likely from asteroidal materials. Small, low-mass specialty components will be shipped up from Earth, but any larger satellite structures that can be made-in-space will be.
What asteroid mining doesn’t presently need is a human presence on-site. Asteroid prospecting is only practical via large numbers of small autonomous space-craft, probably using the Cube-Sat concept as a base design. Actual space-mining, to remain commercially viable, will need clever machinery that doesn’t need a human presence. This doesn’t mean that humans can’t be “in the loop” and as activities move further away from Earth, the light-speed limit will likely mean some human presence will be required. However that’s not going to drive an en masse movement of humans off-Earth. It will likely stretch the limits of human tolerance of isolation and life-support. One could, analogically, compare such asteroid prospectors with the fur-trading trappers who pioneered much of the American wilderness long before the home-steaders and city-builders who eventually followed. With the ability to multiply labour that autonomous machinery implies, the need for vast numbers of space-miners doesn’t seem likely. In Australia the trend for mining has been away from building mining towns to operate mines, towards temporary camps to set-up increasingly autonomous mining machinery to actually operate the mine.
[Addendum: Weirdly, O’Neill makes this very point in 1974…
For comparison, automated mining and shipping in Australia now reaches 200 tons per man-year averaged over a town.
…only more so in the 40 years since.]
(4) Back-up For Planet Earth
Famously Elon Musk’s primary justification for establishing a human presence off-world (Mars being his personal choice) is to provide a ‘back-up’ for the human species, in case something wipes out all life on Earth. The asteroid impact caused extinction of the dinosaurs is commonly pointed to as an example of the kinds of world-shattering events that astrophysics and geology have made us aware of. However the frequency of such events is likely only every few megayears and it’s hard to relate that to a mere 10,000 years of human history, let alone the next decade or century.
However as consequences of such events are so extreme and their timing essentially random, there’s no reason why we shouldn’t start now. More subtle threats to our existence as a species exist, such as bad memeplexes (infectious ideologies), so our spread into space shouldn’t just stop at Mars. Since Mars has proven water, nitrogen and carbon dioxide resources, it’s a good first destination. Developing the means of getting people there, and then allowing them to survive and thrive, provides a good focus for all our human space activities. Mars also has surface gravity that is nearest to Earth’s of all the planets with an accessible surface. This is an underrated resource, as not just biology needs gravity. Many industrial processes are designed with gravity as an assumed resource.
Both Elon Musk & Robert Zubrin have argued for Mars as the goal, for now, and while there are many merits to their arguments, there’s something of a cottage industry in space medicine on decrying how nasty the Martian environment is. Whether that chorus of disapproval will shape future space policy remains to be seen.
(5) Because We Can
Ultimately this is the essence of any argument, since the desire to live on other planets isn’t entirely rational. The driven ambition that has seen thousands of applicants for the Mars One experience is one measure of how deep the feeling goes. I’m hopeful that it will sustain New Colonials on hostile worlds for billennia to come.