What is ISRU and how can it help humanity explore the solar system?
Let’s look to the future. Not 100 years, not 50, but 10; to humanity's first permanent extraterrestrial settlement.
This lunar village will serve as the starting link in what will be a very long chain. A chain that supports a new economy and the final frontier - a chain that makes exploring the depths of the universe possible.
This is the first test. Can we learn to utilize the resources available to us in space? Can we free ourselves from our reliance on our mother planet?
For now, we remain like a dog on a leash, exiled to the corner of our yard.
We came to the moon with structures that unfold like origami. With the help of robotics, we put together a new settlement like a game of high stakes Lincoln logs. We have some of Earth’s best and brightest scientists here, all working together to build the foundation for a fuel depot. We will harvest volatiles from craters on the dark side of the moon. We will create fuel from the frozen molecules in the lunar regolith.
Before long, we will have a full fleet of reusable spacecraft that roam the outer reaches of the earth’s atmosphere, re-fueling the constellation of satellites that orbit the planet, and making a pretty penny doing so.
But, this is not our goal. We dream of a deep and infinite space whose treasures lie far beyond our wildest dreams. The only way this goal is achieved is by creating a strong and flexible infrastructure for us to build upon, to iterate and to start again.
Here we stand on the crest of the first wave, I see the second on the horizon and I gape in awe. I can only imagine what the third will bring.
Historically, human space missions to the International Space Station (ISS) and the Moon have been nearly entirely dependent on Earth resources. All fuel, materials, and food must be supplied from the surface with the crew, and replenished over time for long-duration missions. Space habitats like the ISS are designed to re-use resources through air replenishment, CO2 processing, and wastewater recycling, capabilities that are essential to a functioning life support system in space. As we lay our eyes on more distant destinations, our tether to terrestrial resources must be reduced or cut entirely.
In-situ resource utilization (ISRU) refers to the harnessing of local natural resources at mission destinations to enhance the capabilities of human exploration. ISRU technologies reduce dependency on external resources and bring space habitats one step closer to closed ecological systems that can be self-contained and self-sustaining environments.
It is important to note, however, that future settlements practicing ISRU may seek economic benefits through the trade of resources. Beyond a closed ecosystem, ISRU will take in-space manufacturing, re-fueling, and habitat constructions to unprecedented levels. Space ecosystems can be divided into their biotic (living) and abiotic components (non-living) the same as a terrestrial ecosystem. ISRU is primarily applied to the abiotic components of space ecosystems: light, atmosphere, water, and geology.
Sunlight is a commonly-used resource, both on Earth and in space, through the deployment of solar panels which are arrays of photovoltaic cells that convert the energy of light directly into electricity. Satellites and habitats in orbit rely on sunlight as a main source of energy for their missions. Future lunar missions (like the Artemis program) will rely on solar panels to provide electricity that will power their habitats, infrastructure, and machinery. Unfortunately, solar energy utilization becomes more difficult the further away you are from the Sun. Deep space exploration will certainly use up any solar energy available and so other energy sources will be needed (ex: heat generated from Jupiter’s third largest moon, Io).
The greatest potential for ISRU in creating an extraterrestrial atmosphere is on our planetary neighbor, Mars. The Martian atmosphere consists of 95% carbon dioxide, 3% nitrogen, and 2% argon; it has a density equal to 1% of Earth’s atmosphere at surface level. CO2 can be used as feedstock for rocket fuel production by converting it to methane. Rocket propellant can also be created from the resources available, which will be essential for the long-term survival of a Martian settlement (return to Earth, or venture further into deep space).
Life, as we know it, cannot survive long without available liquid water. Humans in space need a reliable source of water in order to conduct affairs. Other applications for water include growing food, production of oxygen, and most industrial processes. For water chemically bound to regolith, solid ice, or permafrost, a sufficient heat source can be used in the recovery. Where there is some atmosphere, water can be extracted directly using WAVAR, a water-vapor adsorption reactor.
Geological resources on the Moon have the potential to unlock our expansion into the cosmos. Lunar settlements will need their construction materials to come from lunar sources. For example, lunar soil can provide protection from radiation and micrometeoroids. The soil’s regolith is chemically composed of silica (45%), alumina (15%), lime (12%), iron oxide (14%), magnesia (9%), and other metals (5%). Oxygen from regolith can also be a source for rocket propellant oxidizer;it is poor in carbon and nitrogen, but rich in metals and atomic oxygen. Volatiles (chemicals that can be easily vaporized) from permanently-shadowed craters may provide methane, ammonia, carbon dioxide, and carbon monoxide.
Developments over the next few decades will increase the feasibility of combining lunar and Earth-sourced space manufacturing to remove current design limitations especially regarding mass, energy, and signals. The lunar surface is also home to bombardments of helium-3 from solar winds. Also, fusion studies have proposed that helium-3 may provide us with safer fusion reactors.
There are dozens of companies developing ISRU technologies that will contribute to a thriving space economy, and today we will highlight just one. Helios is an Israeli startup focusing on developing technologies to extract oxygen from the lunar regolith, providing an essential rocket fuel oxidizer for space explorers.
Their technology has a potential to reduce the cost of future space activities on the Moon and beyond. Because nearly 50% of the lunar regolith mass consists of oxygen, Helios is focusing on their key product, a Molten Regolith Electrolysis reactor (MRE). Lunar regolith is melted and electrolyzed to separate the abundant oxides into oxygen and various metals (iron, aluminum, titanium, and more). For more information, check out our interview with Helios founder Jonathan Geifman, posted on our website.
How would an abundant supply of fuel on the moon help humanity become multi-planetary?
Supplying lunar oxygen to LEO for refueling reusable rockets could eliminate the need for carrying oxygen to conduct Entry/Descent/Landing (EDL), thereby increasing the payload capacity to LEO.
ISRU will decrease the mass of fuel/materials that need to be shipped to orbit/lunar surface/Mars, allowing for both smaller payloads and greater % of payload mass allocated to other uses; ISRU will help reduce the cost of space travel overall. Fully operational ISRU will be essential to an efficient supply chain and logistics for any future space economy. This allows the space economy to be more inelastic to supply chain disruptions on Earth. For example: Earth shortages in key materials will not affect lunar habitat if ISRU is in place.
The space industry recognizes the importance of ISRU in the future of the space economy, but the science and applications are still at the research & development phase. By applying commercially-driven economic incentives, humanity is more likely to succeed in developing a burgeoning space economy.
If ISRU can make space cheaper, commercial players will dedicate their resources . . .and they already are. Until it becomes economically viable governments will be the initial customers but space exploration is virtually impossible if missions are tethered to terrestrial resources; the application of ISRU concepts is the only way we can successfully live off-planet.
Like our ancestors before us, we are driven to explore the unknown, to satisfy our appetite for new knowledge and technology, and increase prosperity for humanity. As we unhook the dog leash and peer upwards, we take our first steps towards a flourishing mankind that lives amongst the cosmos.
Sources
https://nap.nationalacademies.org/read/26482/chapter/6
https://www.nasa.gov/mission/in-situ-resource-utilization-isru/