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Technical Readiness

Using the material and energy resources of space could be a major game-changer for spaceflight. So why haven't we ever done it?

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Future industrial activity on the Moon -- science fiction? (Artwork by Pat Rawlings)

Space missions are commonly thought of as the ultimate in “high tech.”  After all, rockets blast off into the wild blue yonder, accelerate their payloads to hypersonic and orbital speeds and then operate in zero gravity in the ice-cold, black sky of space.  It requires our best technology to pull off this modern miracle and even then, things can go wrong.  Why would anyone believe that with high technology, sometimes less can be more – that we’re missing a bet by not utilizing current technology.   Like the intellectual tug of war involving man vs. machine, there also is a tug of war between proven technology and high-tech.  Creating these barriers and distinctions is nonsensical.  We need it all.  And we can have it all.

Point in question – in situ resource utilization (ISRU), which is the general term given to the concept of learning how to use the materials and energy we find in space.  The idea of learning how to “live off the land” in space has been around for a long, long time.  Countless papers have been written discussing the theory and practice of this operational approach.  Yet to date, the only resource we have actually used in space is the conversion of sunlight into electricity via arrays of photovoltaic cells.  Such power generation is clearly “mature” from a technical viewpoint, but it had to be demonstrated in actual spaceflight before it became considered as such (the earliest satellites were powered by batteries).

The reason we have not used ISRU is because we’ve spent the last 30 years in low Earth orbit, without access to the material resources of space.  Many ideas have been proposed to use the material resources of the Moon.  A big advantage of doing so is that much less mass needs to be transported from Earth.  The propellant needed to transport a unit of mass from the Earth to the Moon keeps us hobbled to the tyranny of the rocket equation – a constant roadblock to progress.  If it takes several thousand dollars to launch one pound into Earth orbit, multiply that amount times ten to get the cost to put a pound of mass on the Moon.

In the space business, new technologies tend to be viewed with a jaundiced eye.  Aerospace engineers in particular are typically very conservative when it comes to integrating new technology into spacecraft and mission designs, largely on the basis that if we are not careful, missions can fail in a spectacularly dreadful fashion.  To determine if a technology is ready for prime time, NASA developed the Technology Readiness Level (TRL) scale, a nine-step list of criteria that managers use to evaluate and classify how mature a technical concept is and whether the new technology is mission ready.

Resource utilization has a very low TRL level – usually TRL 4 or lower.  Thus, many engineers don’t think of ISRU as a viable technique to implement on a real mission.  It seems too “far out” (more science fiction than science).  Believing that a technology is too immature for use can become a self-fulfilling prophecy, a “Catch-22” for spaceflight:  a technology is too immature for flight because it’s never flown and it’s never flown because it’s too immature.  This prejudice is widespread among many “old hands” in the space business, who wield TRL quite effectively in order to keep new and innovative ideas stuffed in the closet and off flight manifests.

In truth, the idea that the processing and use of off-planet resources is “high technology” is exactly backwards – most of the ideas proposed for ISRU are some of the simplest and oldest technologies known to man.  One of the first ideas advanced for using resources on the Moon involve building things out of bulk regolith  (rocks and soil of the lunar surface).  This is certainly not high-tech; the use of building aggregate dates back to ancient times, reaching a high level of sophistication under the Romans, who over 2000 years ago built what is still the largest free-supported concrete dome in the world (the Pantheon).  The Coliseum was made of concrete faced by marble.  The Romans also built a complex network of roads, some which remain in use to this day; paving and grading is one of the oldest and most straightforward technologies known.  Odd as it may seem, sand and gravel building material is the largest source of wealth from a terrestrial resource – the biggest economic material resource on Earth.

Recently, interest has focused on the harvesting and use of water, found as ice deposits, at the poles of the Moon.  Digging up ice-laden soil and heating it to extract water is very old, dating back to at least prehistoric times.  This water could contain other substances, including possibly toxic amounts of some exotic elements, such as silver and mercury.  No problem – we understand fractional distillation, a medieval separation technique based on the differing boiling temperatures of various substances.  Again, this concept is not particularly high-tech as only a heater and a cooling column is needed (basically the configuration of an oil refinery).  Some workers have suggested that lunar regolith could be mined for metals, which can then be used to manufacture both large construction pieces and complex equipment.  Extracting metal from rocks and minerals is likewise very old, developed by the ancients and simply improved in efficiency over time.  Processes like carbothermal reduction have been used for hundreds of years. The reactions and yields are well known, and the machinery needed to create a processing stream is simple and easy to operate.

In short, the means needed to extract and use the material wealth of the Moon and other extraterrestrial bodies is technology that is centuries old.  Even advanced chemical processing was largely completely developed by the 19th Century in both Europe and America.  The “new” aspects of ISRU technology revolve around the use of computers to control and regulate the processing stream.  Such control is already used in many industries on Earth, including the new and potentially revolutionary technique of three-dimensional printing.  A key aspect of the old “Faster-Cheaper-Better” idea (one NASA never really embraced) was to push the envelope by relying more on “off-the-wall” ideas, whereby more innovation on more flights would lead to greater capability over time.

Nothing that we plan to do on the Moon involves magic, alchemy or extremely high technology.  Like most new fields of endeavor, we can start small and build capability over time.  The TRL concept was designed as a guideline.  It was not intended as a weapon eliminating possibly game-changing techniques from consideration or to carve out funding territories.  Attitudes toward TRL must change at all levels, from the lowly subsystem to the complete, end-to-end architectural plan.  A critical first step toward true space utilization and for understanding and controlling our destiny there is to recognize and take advantage of the leverage one gets from lunar (and in time planetary) resource utilization.

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About Paul D. Spudis
Paul D. Spudis

Paul D. Spudis is a senior staff scientist at the Lunar and Planetary Institute in Houston, Texas. His website can be found at www.spudislunarresources.com. The opinions expressed here are his own and do not reflect the views of the Smithsonian Institution or his employer.

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