Robert Mueller

In-situ Resource Utilization (ISRU) and the future of commercial space

For this new Space Law article written by NASA Robert P. Mueller, let us look at In-situ Resource Utilization (ISRU) and the future of commercial space. Celestial bodies – including the Moon or near-Earth objects (NEOs) such as asteroids – are naturally forming objects found beyond Earth’s atmosphere. Many planets, moons and asteroids contain a rich diversity of inert physical substances such as metals, along with gases and water that could be used as energy sources and means to sustain human life as we venture deeper into space. Many of the metals found within the Moon and other celestial bodies are already scarce on Earth. One day, we may use them not only to construct equipment in space but transport them back to support terrestrial activities, employing on Earth the technologies developed to explore and mine resources in outer space.

In space exploration (the discovery and exploration of celestial structures in outer space by means of evolving and growing space technology), in situ (which means “in its original position or place” in Latin) resource utilization (ISRU) is the practice of collection, processing, storing and use of materials found or manufactured on other astronomical objects (the Moon, Mars, asteroids, etc.) that replace materials that would otherwise be brought from Earth.

According to NASA, “In-situ resource utilization will enable the affordable establishment of extraterrestrial exploration and operations by minimising the materials carried from Earth and by developing advanced, autonomous devices to optimise the benefits of available in-situ resources”. The three most-likely used celestial bodies in future In-situ Resource Utilization (ISRU) will be the Moon, Mars and asteroids.

In the context of ISRU, water is most often sought directly as fuel or as feedstock for fuel production. Applications include its use in life support either directly by drinking, for growing food, producing oxygen, or numerous other industrial processes. All of which require a ready supply of water in the environment and the equipment to extract it. Such extraterrestrial water has been discovered in a variety of forms throughout the Solar System, and a number of potential water extraction technologies have been investigated.

Today, many in the space community think that In-situ Resource Utilization (ISRU) is not ready for use in actual missions, however it is a fact that space resources are already being used in outer space today. Solar energy provides substantial capability to satellites in Earth orbit and on inter-planetary journeys. The orbits themselves are a resource as evidenced by the geo-synchronous orbital slots allocated by the International Telecommunications Union (ITU).

The Solar System contains vast amount of resources that dwarf the resources available on Earth. The pertinent question is: “Are these resources economically available?” Do they rise to the level of being classified as a “proven ore reserve” as defined by the Australian Joint Ore Resources Committee (JORC)? Commercial ventures that are evolving today need assurance that the resources are available as proven ore reserves in order to proceed.

The resources available in outer space are dependent on the destination. The Moon has a variety of resources, Mars has different resources and asteroids offer other alternatives. The common denominator in all the destinations are “volatiles” and specifically water. Water is the key to human survival and transportation in outer space. Water can be used for radiation shielding, life support, hygiene, and it can be used as propellant in the form of hydrogen and oxygen which can be electrolyzed from water using solar energy. The Moon has abundant oxygen available in the regolith covering its surface. One kilogram of regolith contains four hundred and twenty grams of oxygen in indigenous silicates. The regolith is also rich in metals: iron, aluminium, titanium, and magnesium can all be found in significant quantities in the regolith minerals. The bulk regolith itself can be used as an aggregate for lunar concrete. At the poles, emerging evidence indicates that water ice exists as well as other volatiles including methane, ammonia, hydrogen gas, carbon dioxide and carbon monoxide.

On Mars, the obvious resource is the ninety-five and a half percent pure carbon dioxide available in the atmosphere. Water is also available in the regolith as a sub-surface deposit. Gypsum sand dunes may contain up to twenty percent of water yield. Asteroids are diverse due to their history of early Solar System formation: taxonomy considerations result in over seventeen different classifications of asteroid types. The most interesting for In-situ Resource Utilization (ISRU) purposes are carbonaceous chondrites with up to twenty percent water content and the M-type metallic asteroids.

If these various ore bodies can be economically harnessed, then a viable source of off-Earth propellant may become available. The significance of this propellant is that it does not have to be launched out of Earth’s gravity well at a high energy cost, so space transportation will become affordable.

The initial customers for these resources will likely be the current actors in outer space: government agencies. As the Solar System is explored and technologies become more mature, then commercial entities will emerge to take advantage of the vast amount of Solar System resources. The sequence of resource utilization will be to use solar energy and favorable orbits such as the one used by the proposed NASA gateway orbital command module in a highly elliptical “near-rectilinear halo orbit”.

The next most important aspect of the lunar mission architecture is a safe landing. Due to rocket engine plume surface interaction, high velocity ejecta and cratering will pose a hazard, so it is very likely that landing pads will be necessary for safety reasons. This means that In-situ Resource Utilization (ISRU) construction with bulk regolith concrete is the next most likely product in the sequence of In-situ Resource Utilization (ISRU) development. As missions proceed and become routine, then ore deposits will be found and mined. At this point oxygen, water and metals will become the next resources to be exploited. If all these resources can be used at a cost less than that of launching the needed materials from Earth, then In-situ Resource Utilization (ISRU) will become a necessary and viable part of our enabling exploration technologies. This is what can be said concerning In-situ Resource Utilization (ISRU) and the future of commercial space.