Issue #4(14) 2017 Astronautics

Creating a viable cislunar economy

James Vaughan
James Vaughan
George Sowers Colorado School of Mines/Sowers Space Solutions, Denver, Colorado, USA

In the history of humankind there have been two major economic revolutions. First, the agricultural revolution of roughly 10,000 years ago transformed humans from hunter-gatherers to farmers. A new kind of farming lifestyle greatly increased the ability of human communities to capture energy and enabled a hundredfold increase in human population.

Then, some 300 years ago, came the industrial revolution which enabled the economic utilisation of energy locked in Earth for 300 million years in the form of fossil fuels, and with it a tenfold increase in human wealth and population.

The use of fossil fuels and the burgeoning human population has put tremendous stress on our planet and its climate

But the use of fossil fuels and the burgeoning human population has put tremendous stress on our planet and its climate. Furthermore, fossil fuels are limited and will eventually be depleted. Some view this circumstance with gloom and foresee an eventual collapse of society. Others are hard at work on the third great economic revolution - space and space resources.


Compared to the finite and increasingly depleted Earth, the resources available in space are essentially infinite. Development and exploitation of these resources will enable humankind to continue its trajectory of ever-increasing prosperity and well-being while preserving, or even enhancing, our unique home in the universe, Earth.

There are more than enough resources available just in the inner solar system to fuel the next economic revolution. For example, the energy output of the Sun is some 13 orders of magnitude greater than the current energy consumption of all humanity.

Water exists in great quantities on the Moon, in asteroids and on Mars. It has many uses including rocket propellant (when broken into hydrogen and oxygen). In other words, water is the oil of space but far more abundant than oil ever was on Earth. Similarly, just a few average sized metallic asteroids contain more metals than have ever been mined on Earth.

The potential of space resources is apparent. The challenge is how to get at them and what’s required is the infrastructure of a robust space economy. The first place to begin is cislunar space, the Earth, Moon and the immediate neighbourhood, including the region that contains near Earth objects (NEOs) or asteroids.

issue14-Figure-1-the-geography-of-cislunar-space-the-key-locations.jpgFigure 1: the geography of cislunar space, the key locations, Delta V between them and potential economic activities.

Free market power

There are more than enough resources available just in the inner solar system to fuel the next economic revolution

Creating a robust economy in space means harnessing the power of the free market. Competition in the free market spurs innovation leading to efficiency and growth. But the foundation of the free market is the consumer - and for the time being all consumers live on Earth.

The future space-driven economy needs to deliver value to consumers on Earth. Hence, the close environs of Earth, cislunar space, is where we must begin. The commercialisation of cislunar space leads to what had been dubbed the cislunar ‘econosphere’, an economic environment through which space resources can be developed and Earth freed from its resource constraints.

issue14-Shackleton-crater-near-the-south-pole-of-the-moon.jpgShackleton crater near the south pole of the moon. True illumination on the right. Color elevation contours on the left.

The geography of cislunar space determines the types of economic activities that might take place in various locations. The key locations are low Earth orbit (LEO), geosynchronous orbit (GEO), Earth-moon Lagrange point number one (EML1), low lunar orbit (LLO), the lunar surface or a near Earth object (NEO) or asteroid.

Of critical importance is the energy required to move from one location to another. A useful proxy for this energy is Delta V, the increment of velocity that must be added to a spacecraft to travel from one location to another. Figure 1 shows the relative locations in cislunar space, the delta V between the locations as well as some of the economic activities that might take place at key locations.

One of the first economically viable uses of resources in cislunar space will be propellant manufactured from water. There are several reasons for this. First, one of the most significant findings of space science of the last decades has been the abundance of water in the inner solar system. The permanently shadowed regions near the poles of the Moon harbour significant quantities of water in the form of ice.

issue14-the-advanced-cryogenic-evolved-stage.jpgThe advanced cryogenic evolved stage (ACES) will form part of a fully reusable in-space transport system.

Shackleton Crater is near the lunar south pole and not far from the Cabeus crater where a spent Centaur upper stage was crashed to examine the spectral content of the ejecta plume. Water content was measured in the 5-10 percent range. In addition, many asteroids, including NEOs, are thought to contain large quantities of water. And we believe there is water on Mars. Second, water has many uses in the space economy, but the most significant near-term use is as propellant. Water’s constituents, oxygen and hydrogen, when separated and liquified, are the most efficient chemical rocket propellants known. Finally, space sourced propellants can dramatically reduce the cost of every other activity in cislunar space.

To take full advantage of space-sourced propellant requires refuelable in-space vehicles. Nothing like this exists today but United Launch Alliance (ULA) is currently developing a new upper stage which will embody all the necessary features.

Called the Advanced Cryogenic Evolved Stage (ACES), it includes advanced technology eliminating the need for any fluid commodities other than liquid hydrogen and liquid oxygen propellants. In addition, ULA has perfected the technology and processes to transfer cryogenic fluids from one tank to another under space conditions.

ACES will debut as an upper stage in the early 2020s. When equipped with a landing kit, ACES can also function as a lander, enabling surface access to the lunar surface. The landing version of ACES is called XEUS.

It would be far better if one could devise a commercial business model that would build the infrastructure incrementally

Together, ACES and XEUS form the elements of a fully reusable in-space transportation system that can be fuelled by propellants mined from water found on the lunar surface or asteroids. With such a transportation system in place, we can imagine trade routes within cislunar space transporting raw materials from the Moon and asteroids to central distribution and manufacturing nodes like EML1, and then down into Earth’s orbit or surface.

Due to the enormous energy required to climb out of Earth’s gravity well, once manufacturing capability is established in space, only very high value, low mass items will be transported directly from Earth. Examples include people and microchips.

On the other hand, mass-less entities like photons have no problem with gravity. Hence, information will be a major export from Earth to cislunar space. This information will take the form of instructions and product designs for in-space manufacturing facilities as well as information to keep the cislunar economy humming along. Similarly, photons in a form readily converted into terrestrial electricity will be a major import from to Earth from cislunar space. This important aspect of the cislunar econosphere is highlighted below.

issue14-XEUS-the-ACES-stage-equipped-with-a-landing-kit.jpgXEUS, the ACES stage equipped with a landing kit.

The transportation architecture will be enabling for all other activities in cislunar space. However, the costs to emplace such an infrastructure are daunting. The easy answer is to assume that governments (taxpayers) can be persuaded to bear the expense. But it would be far better if one could devise a commercial business model that would build the infrastructure incrementally while returning profit along the way.

An example of such a business model was developed by ULA based on using space-sourced propellant to ferry satellites from low Earth orbit to geosynchronous orbit. Based on this model, ULA set a price for propellant at the EML1 node of US$1 million/ton. This price can now be used by the emerging space mining companies to refine their own business models. In addition, ULA’s analysis was used to derive requirements for a potential lunar mining facility in terms of mass, cost and efficiency.

Once a transportation infrastructure is in place, all other activities in cislunar space become much more economical. One of the most important activities for the cislunar econosphere will be providing energy to Earth. Worldwide energy consumption is currently on the order of 12.5 terra-watts valued at about US$7 trillion per year. Over 85 percent of this energy is supplied by fossil fuels in the form of oil, natural gas and coal. These resources are necessarily finite and will grow increasingly more expensive as reserves are depleted. Furthermore, use of these resources has harmful consequences for Earth’s environment and climate.

The assumptions are challenging and require the development and establishment of large scale space mining and manufacturing infrastructure

Use of solar power from space can alleviate issues of scarcity and environmental damage of fossil fuels. And unlike terrestrial solar and wind power, space solar power (SSP) is well suited for base load and requires a much less intrusive terrestrial footprint. At geosynchronous orbit, a solar power satellite will receive a daily solar power incidence of 32.8 kW-hr/m2. This compares to 7.5 kW-hr/m2 in June at my home in Colorado in the USA and just 2.5 kW-hr/m2 in December.

issue14-The-Solar-Power-Satellite-Alpha-concept.jpgThe Solar Power Satellite-Alpha concept. Solar energy is collected, converted to microwaves and beamed to Earth.

One concept for a two giga-watt SSP satellite - called Solar Power Satellite (SPS) Alpha - was developed by John Mankins under contract to NASA. It is a very large object, measuring 3 x 5 km and with a mass, if launched from Earth, of 12,000 tons. At today’s prices, just the launch costs would total U $320 billion - clearly unaffordable. However, if one can source most of the raw materials on the Moon, manufacture the components at EML1, and assemble it in place at GEO, the economics move into the realm of feasibility. All transportation is assumed to be provided by ACES and XEUS.

Given these assumptions, the business case is feasible and offers reasonable returns. The total non-recurring cost, as well as the development cost per kilowatt of capability, is comparable to a large scale nuclear powerplant and well within the resources of large commercial power companies.

The assumptions are challenging and require the development and establishment of large scale space mining and manufacturing infrastructure. But once established, this infrastructure can enable the construction of hundreds of solar power satellites, reducing and eventually eliminating our reliance on fossil fuels while enabling increased prosperity through inexhaustible, carbon-free, low cost energy.


Interest in developing the cislunar economy is expanding around the globe as companies and governmental agencies begin to realise the incredible potential of the next great economic revolution for humanity. The transportation system will be the first economically viable sector of the econosphere to be established, enabling everything that follows. The capstone will be space solar power, tapping into the enormous worldwide energy market and providing benefits to billions of people on Earth.

About the author

Dr George Sowers has 30 years of experience in the space transportation field working for Martin Marietta, Lockheed Martin and the United Launch Alliance (ULA). He recently retired from his position as Vice President and Chief Scientist at ULA where his team developed an architecture for fully reusable in-space stages fuelled by propellant mined, refined and distributed in space. Dr Sowers has now joined the faculty of the Colorado School of Mines as part of a newly created graduate programme in space resources. He holds a BS in Physics from Georgia Tech and a PhD in Physics from the University of Colorado. Dr Sowers is a fellow of the American Institute of Aeronautics and Astronautics (AIAA).

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