Civil Engineering in Space

Consider the complex and expensive process of lifting materials into orbit and keeping them balanced against the grasp of earth's gravitational field. Just moving a pint of water into high earth orbit is estimated to cost over $15,000 US and takes months of multidisciplinary engineering. Currently there is no reason to believe similar factors will not apply for any inhabitable body in space for many years to come. From this standpoint alone, once hypothetical materials transportation to these large bodies has been accomplished it would make sense to keep them there, under control and under no circumstance wasted or discarded. This was a primary impetus for recently lifting a high tech urine recycling unit to the international space station, because $7,500 is a lot to pay for a one way rental on a cup of coffee.

But there are other subtle yet no less important reasons to think about sustainable extraterrestrial development. The present concern over man-made locally orbiting debris is a good example. Decades of near earth utilization has led to an orbiting cloud of now useless materials from collisions, failed placements, obsolescence, malfunctions, butter fingers, and fail-safe destruction (because rocket science doesn't incorporate “self recycle” mechanisms in vehicles and equipment, rather “self destruct and worry about cleanup some other time” mechanisms are typically employed).

Recovering this debris is not just a matter of sending a garbage scow scuttling around the orbital arena. These objects travel at different speeds, orbits, and directions, with sizes ranging from less than one centimeter to entire derelict satellites. And the orbital mechanics involved are not trivial, relative velocities alone can be tens of thousands kilometers per hour. The long term consequences of this buildup are constant monitoring and extrapolation to avoid further damage to equipment and astronauts attempting to do useful work. Currently prevention is one and possibly the only cure in this all too real scenario.

There was a time when earth's oceans were viewed as a vast, immutable repository for waste and excess. “Dilution,” as the saying went, “is the solution to pollution.” Time and knowledge has shown how misguided this view had been.

Neither should extraterrestrial endeavors view the infinite space environment as the infinite waste disposal. Even the extremely limited visits to the moon over the past 40 years have left an estimated 300,000 pounds of scientific instrumentation, memorials and memorabilia, excess equipment, and outright trash. Interestingly, there are no “cradle to grave” specifications for any off-earth materials, which has resulted in some political turmoil regarding international responsibilities for unused materials in space. Perhaps a few tried and tested terrestrial axioms should still apply:

1. What goes around, comes around. Never truer than in orbital dynamics.

2. Waste not, want not. Got it, own it, recover it, use it again.

3. Design with the end in mind. Decommissioning should be the start of something useful.

Getting these principles into extraterrestrial development planning is hopefully going to be an obvious choice.

For example, utilizing extraterrestrial water, minerals, gases and other resources should give more than a passing glance at waste generation and handling. A fairly realistic illustration of axiom #1 in this example would be an extractive mining development on a solar orbiting asteroid or planetoid. It may be convenient to simply eject tailings away from the asteroid as the extraction process progresses. As trivial as the amount of tailings may seem, the change in total asteroid mass from the ejected tailings and the extracted products can measurably change the orbital trajectory of the asteroid.

It could be argued that in the vastness of space, such small trajectory adjustments and debris are of no consequence assuming they are properly plotted and extrapolated. It could also be argued that same vastness leaves many possible extrasolar encounters and influences unaccounted for… which begins to appear as the start of another orbiting debris cloud, only much larger and with more dire consequences.

To help illustrate axiom #2 our unquenchable need for water can be used. Surprisingly, when water usage is modeled for extraterrestrial consumption in a closed system, the largest amounts are used for cleaning and not for drinking or cooking. Until adequate off-earth water resources are being utilized, even the lowly septic system becomes quite a sustainable design challenge for even the smallest habitation. This in fact may be the limiting factor in engineering anything close to a sprawling off earth metropolis, which partially explains the current emphasis on finding and utilizing extraterrestrial water in an efficient, cost effective manner.

For axiom #3 there are many far future applications like self healing polymers, memory metals, nanobots and the like which are targeted for use in self maintenance and reassembly, or even final disassembly into reusable materials. There are also present day and near future design applications as well; pavements, metals, wood, polymers, and other materials are constant targets of civil engineering re-purposing. Self servicing, automated repair systems and unlimited reuse of raw materials are also becoming the holy grail of sustainable engineering endeavors. Self healing coatings and flexible “poured stone” products are a reality today. Presumably combined terrestrial and extraterrestrial research efforts will eventually result in making the terms “trash”, “disposable” and “construction debris” avoidable anachronisms.

So while it takes cutting edge rocket science to get there, it will take sustainable civil engineering to live there.

Surviving a remote and possibly harsh environment in an extraterrestrial setting is a matter of being highly self-reliant. This means habitations, developments, and colonies should be considered “closed systems,” able to sustain themselves without external input. Please click the next section below to continue.