EXECUTIVE SUMMARY
In 2019, the Technology Working Group (TWG) of the International Space Exploration Coordination Group (ISECG) established a Gap Assessment Team (GAT) for the topic of In-Situ Resource Utilization (ISRU). The ISRU GAT Assessment is intended to examine and identify technology needs and inform the ISECG on technology gaps that must be addressed in order to implement foreseen missions. Ultimately, this initiative intends to create international dialogue among experts and inform agency decisions when considering investments is specific exploration technologies, while identifying potential collaboration opportunities. The following sections are an executive summary of the main sections of the full report.
Strategic Knowledge Gaps Definition
To help ensure that plans for human exploration of the Moon would be successful, an assessment was made to determine the state of human exploration technologies and capabilities. Where insufficient knowledge and/or capability was found, a statement of need was created. From this effort, a list of what became known as Strategic Knowledge Gaps (SKGs) was created in three broad themes of exploration, of which ISRU is relevant to the first and third theme. Since then, the SKGs have been reviewed and used to guide and prioritize development and flight activities for human exploration of the Moon. At the start of this effort, the In-Situ Resource Utilization (ISRU) Gap Assessment team reviewed the last approved SKG list with respect to ISRU technologies, capabilities, and operations in four major resource function areas (polar water, solar wind volatiles, oxygen metals from regolith, and construction and manufacturing) and the overall operation of any ISRU capability. From this effort, a table was created that establishes the potential impact the SKG has on each of the 4 major resourcefunction areas and ISRU operations, how where the SKG will be closed, and when in the three-phase human lunar exploration architecture the SKG needs to be closed. The intent of this table (Table 3) is to allow decision-makers and developers to prioritize and plan the closure of these SKGs to achieve the desired ISRU capability and product.
ISRU Functional Breakdown and Flow Diagram
The identification, extraction, processing, and use of space resources will require a significant amount of technology, system, and capability development across a wide field of technical disciplines. The end-to-end process from resource identification to product delivery will also require a significant number of sequential and parallel steps. To ensure that all the technologies and processes have been properly identified and addressed throughout the end-to-end sequence from ‘prospecting to product’, the ISRU Gap Study team created two sets of tables/figures. The first set of tables examines the scope and breakdown of each of the three main ISRU capabilities examined in the study: 1) In-Situ Propellant and Consumable Production, 2) In-Situ Construction, and 3) In-Space Manufacturing with ISRU-derived Feedstock. For each of these three main ISRU capabilities, the major functions required to successfully implement the capability were defined and as well as the subfunctions associated with each of these major functions (depicted in Figures 3, 4, & 5). While these tables allow decision-makers and developers to define, address, and track past and on-going activities to successfully implement ISRU, the tables do not provide insight on how each of these functions and sulfunctions may influence or be influenced by other areas of ISRU. To provide this level of insight, an integrated ISRU functional Flow Diagram was created (Figure 6). The figure allows decision-makers and developers to understand where gaps or deficiencies may still exist in the end-to-end processes as well as allow for better understanding of interfaces for partnerships and solicitations.
ISRU in Human Exploration
In-Situ Resource Utilization (ISRU) involves any hardware or operation that harnesses and utilizes local or in-situ resources to create products and services for robotic, and human exploration and sustained presence, instead of bringing them from Earth. The immediate goal of ISRU is to greatly reduce the direct expense of humans going to and returning from the Moon and Mars, to build toward the self-sufficiency of long-duration crewed space bases used to expand science and exploration efforts, and to enable the commercialization of space. To achieve the greatest benefits of ISRU incorporation into mission architectures, other systems need to be designed around the availability and use of ISRU-derived products. Therefore, ISRU is a disruptive capability and requires an architecture-level integrated system design approach from the start. The most significant impact ISRU has on missions and architectures is the ability to reduce launch mass, thereby reducing the size and /or number of the launch vehicles needed, or use the mass savings to allow other science and exploration hardware to be flown on the same launch vehicle. From past studies and analyses, somewhere between 7.5 and 13.1 kilograms of propellant and rocket stages are needed to deliver every 1 kilogram to the lunar or Martian surface.
Therefore, the highest impact ISRU products that can be used early in human lunar operations are mission consumables including propellants, fuel cell reactants, and life support commodities.
Human Mars Surface Exploration
As was mentioned at the beginning of the section, Tables 6a, b, c, & d define a Mars human exploration architecture with a similar phased approach as being used for the Moon: Preparatory Missions, Pre-Outpost (“Boots on Mars”), Outpost Start (“build-up to sustainability”), and Sustained Presence. As with the human lunar exploration architecture, the Preparatory Phase has already started with several missions recently arriving on Mars and more orbiters and robotic landers planned for further science and resource understanding, in particular, understanding the “water cycle” and location, type, and amounts of surface and subsurface water and ice. Plans for the Pre-Outpost Phase vary from short duration stays on the Mars surface (30 to 90 days) to potentially 540 type day missions for Conjunction-class trajectories. For this phase, ISRU insertion will be based on enhancing mission capabilities or enabling mission capabilities if the mission need outweighs the risk.
A major issue for the first crewed surface missions is the crew ascent vehicle mass, and particularly the delivery of the amount of propellant needed for ascent. It is anticipated that at a minimum ISRU oxygen production (e.g. derived from the Martian CO2 atmosphere) for crew assent vehicle propulsion, and support and enhance life support oxygen buffer gases for the habitat and EVA will be utilized. Some demonstrations, and utilization of manufacturing and construction capabilities, most likely with Earth-supplied feedstock, will be performed as well to minimize risks for future missions. During the Outpost Start Phase, it is anticipated that the type, scale, and range of products for ISRU will increase. If water mining and processing and methane production wasn’t performed during the Pre-Outpost Phase, then it is anticipated that it will occur during this phase. ISRU demonstrations will be performed for full incorporation during the Sustained Presence phase. The Sustained Presence Phase will allow crew to stay for longer periods than a single Earth-Mars orbital alignment and begin to significantly reduce dependence on Earth and allowing infrastructure expansion.
Resource-Product-Application Assessment
The subject of ISRU covers a wide range of potential resources, products from these resources, and how these resources could be utilized in human exploration plans. The ISRU Gap Study team recognized early that not every option can be developed, that some might have a greater influence on mission cost and success than others, and that some might be needed earlier than others. In an attempt to trace how a potential resource could produce a possibly important product and how this product could potentially enhance or enable a mission-critical application or use, the team initially created two separate tables: a Resource vs. Product Table and a Product vs. User/Application table. For each table, the team attempted to assess both the impact the confluence might have on the architecture (high, medium, low, or not applicable) and when the human lunar exploration architecture might provide significant benefits (near-term, mid-term, or low-term). After each table was created, it was determined that integrating the two separate tables into one (Table 7) would provide decision-makers and developers a concise way to best understand this complex three-dimensional dependency, influence, and impact of potential resources to the applications that would utilize the products derived from these resources.
From this activity, the team determined that the highest impact ISRU products that can be used early in human lunar operations are mission consumables including propellants, fuel cell reactants, life support commodities (such as water, oxygen, and buffer gases) from polar resources (highland regolith and water volatiles in PSRs).
While not in the original scope of the study, evaluation of human Mars architecture studies and Table 7 suggest that there can be significant synergy between Moon and Mars ISRU with respect to water and mineral resources of interest, products and usage, and phasing into mission architectures.
Technology, Facility, and Simulant Portfolio
To assess the state of ISRU development and identify where more work is needed, the ISRU Gap Assessment team performed a comprehensive assessment of past and recent efforts to develop ISRU technologies, systems, and capabilities as well as the facilities and simulants that are needed to prepare these ISRU efforts for flight.
The technology assessment utilized the functional breakdown structure previously discussed. A table (Table 8) is included in the report which includes information on a portfolio of capabilities and developments for each function sulfunction and past/recent efforts from the participating countries government agencies in each of these areas. This table highlights that a significant amount of work is underway or planned for ISRU development across all the countries/agencies involved in the study, particularly in the areas of resource assessment, robotics/ mobility, and oxygen extraction from regolith.
The team recognized that to prepare ISRU for flight and future incorporation into human space exploration activities, the technologies, systems, and capabilities will need to be extensively tested on Earth under as realistic conditions as possible. Since lunar resources of interest are in or bound to lunar regolith, ISRU development requires facilities that can simulant lunar vacuum and temperature conditions while also allowing for hardware to interact with and or process lunar regolith simulants. Facilities with these capabilities are unique since once regolith has been added to a vacuum chamber, it will most likely not meet the cleanliness levels required for most other system flight hardware verification and acceptance testing. Therefore, the team performed an assessment to determine what 1 facilities currently exist or are in development planned), 2) what environmental simulation capabilities they cover, and 3) what size of hardware can they accommodate that can support ISRU environmental testing. Table 9 in the report provides information on the status and capabilities of each country’s/government agency’s environmental facility capabilities. While engineered ambient test facilities were included in this assessment, natural analogue test locations were not. While it appears that each country/space agency has access to research and component/subsystem size test facilities that can accommodate regolith dust and lunar vacuum/temperatures, there are a limited number of large system-level facilities that exist or are planned.
Lessons learned from hardware operation on early robotic and human exploration missions to the Moon showed that the success or failure of the hardware was greatly influenced by the simulant used to mimic lunar regolith in pre-flight testing. As knowledge of lunar regolith has increased, the ability to adequately replicate important aspects and characteristics of lunar regolith has increased, thereby increasing the likelihood of successful operation. Unlike other surface hardware and systems that try to avoid or mitigate interaction with lunar regolith, ISRU hardware and systems must interact with regolith on a continuous basis over months and years of operation. To successfully develop ISRU capabilities, it is recognized that a large amount of lunar regolith simulant will be needed and that different characteristics of the regolith will be important depending on the processes and technology being developed. For this reason, the ISRU Gap Assessment team performed an assessment of the state of existing Moon and Mars simulants as well as the potential availability for on-going and planned development efforts. Table 10 in the report provides a top-level understanding of Moon/Mars simulants for each country/government agency involved in the study. The assessment of simulants shows that 1) while simulants are available for development and testing, greater quantities and higher fidelity simulants will be needed soon, especially for polar highland-type regolith, and 2) selection and use of proper simulants is critical for minimizing risks in development and flight operations.
It should be recognized that while the technology, facility, and simulant assessments were as comprehensive as possible, the inputs may not be all-inclusive. Therefore, sections were added to allow each country /government agency to provide further information about their specific activities and plans for ISRU development.
Gap Assessment
As the name implies, the ISRU Gap Assessment team was chartered to assess the state of the art for ISRU technologies, systems, and capabilities, and to define the remaining work (gaps) that will need to be performed and completed to finally achieve the desired end-goals for ISRU incorporation into human lunar and Mars exploration. To perform this task, the team utilized the highest priority/ impact ISRU products and applications,
In-Situ Resource Utilization Gap Assessment Report
the ISRU functional breakdowns, and information gathered in the Technology Assessment to provide decision-makers and developers an understanding of the remaining work that needs to be addressed in future efforts.
Because there are no firm requirements for ISRU products and systems, the gap assessment performed is meant to provide general information at the capability-level versus highly specific parameters that would be needed for a technology-level gap assessment. The reader is highly encouraged to examine closely the information provided in Table 8 since the table provides the greatest amount of information possible for technologies under consideration by each country government agency. The reader is also encouraged to examine the mission phasing and priority impacts for ISRU demonstrations and systems in Table 5a, b, and c Human Lunar Exploration -Phases, and Table 7 ISRU Resources, Products, and Applications to better understand the overall importance of closing different technology and capability gaps.
The following specific gap assessments were performed and a high-level summary is provided hereafter.
Destination, Reconnaissance, and Resource Assessment
A major objective for human lunar and Mars exploration is to be able to acquire and utilize in-situ resources to enable sustained surface operations and future commercialization of space. To achieve this objective, detailed knowledge of the location, type, and distribution of potential resources is needed to select outpost and mining locations, and develop technologies and systems to extract and process the resources. Therefore, the knowledge in the destination, reconnaissance and resource assessment, critical technologies, and data collection-management need to have crucial roles early in human lunar and Mars exploration plans. While information from Apollo missions and regolith samples and orbital science missions have provided excellent information on regolith properties and global understanding of resources, knowledge about polar regolith and resources, especially in Permanently Shadowed Regions (PSRs), is currently insufficient to eliminate or mitigate risk in site selection and mining technology development. The team assessment identified new efforts in refocusing technologies and instrumentation for lunar and Mars operations, and several missions to begin surface and deep assessment of resources are in development, especially to obtain maps of minerals on the lunar surface, surface topography and terrain features, or to understand the depth profile of water and volatiles. Almost all space agencies are working on instruments for physical geotechnical and mineral chemistry characterization of regolith. There is also strong interest in developing instruments and hardware for subsurface ice indirect and direct characterization. There is also strong interest in developing mobile resource exploration and autonomy.
While work on resource assessment physical, mineral, and watervolatile measurement instruments are underway, and new orbital and lunar surface missions are in development or planned, a focused and coordinated lunar resource assessment effort is needed. Resources characterization determines the interest to use instrumentation with specific performances, and in general, instrumentations with higher performances can be of help to better plan resource assessment and mining operations as well as potentially support direct landing within PSRs. Determine these constraints is basilar to support new efforts in refocusing technologies and instrumentation for lunar or Mars operations, several missions to begin surface and deep assessment of resources are in development, especially to obtain maps of minerals on the lunar surface, surface topography, and terrain features, or to understand the depth profile of water and volatiles.
Resource Acquisition, Isolation and Preparation
Once a resource has been identified, located, and characterized, the next step in achieving a product from the resource is the ability to extract/acquire, separate, and potentially prepare the gas or material for processing. Call Pim photosRequirements for resource acquisition, isolation, and preparation are linked to resource processing techniques. Technological challenges are linked to needs of resources acquisition, isolation, and preparation: long duration and high level of performances as excavate and analyse raw materials contents require optimized machines. The presence of contaminants from the extracted gas resources or accumulation of contaminants in regenerative chemical processing represents critical problems that need reliable solutions. Mobility operations, locomotion, and storage of tons of raw materials require an integrated plan of management and optimization. Robotic systems need to be able to work in hard conditions as in dusty environments and need to be endowed of Autonomy and localization systems through the appropriate integration of Al, sensors, and Communication & Navigation instruments. Some advanced technologies for the direct collection of gasses from Mars atmosphere and excavation of lunar regolith are already under development. There is strong interest in developing hardware for sample excavation of granular and hard /icy regolith. There is currently limited work on crushing, size sorting, and mineral beneficiation, most likely due to lack of firm requirements.
Resource Processing for Production of Mission Consumables
Through evaluation of potential resources, products, and applications for lunar exploration, the primary processes and products of interest are oxygen extracted from regolith and ice extracted from polar permanently shadowed regions. To achieve implementation of these processes/products into future missions, relevant environment simulating Moon and Mars environment conditions need to be used to demonstrate autonomous operations and multi-step processing: physical and chemical processes are well defined, these techniques require significant advancement before the incorporation into a mission demonstrator. Storage and managing systems for potential volatiles need to be validated also in Moon and Mars environmental conditions.
The assessment performed identified complementary and overlapping work on oxygen extraction and limited work on water extraction, mostly at demonstration scale. Water and carbon dioxide processing technologies for the Moon and Mars were mostly related to life support or terrestrial applications.
Resource Processing for Production of Manufacturing and Construction Feedstock
Bulk or refined regolith will be the main constituent for construction, and manufacturing until more refined feedstock is available. Regolith is also at the base of ISRU processing to extract useful gasses and water but also metals, which require complex reactant regeneration and metal separation steps in vacuum. Metal extraction processes requires generally also large amounts of power, necessary for both molten regolith electrolysis and molten salt electrolysis technologies. Resource processing to produce plastics typically require complex and multi-step methods, and also silicon production requires specific processes that need to be demonstrated for space applications. As with oxygen extraction from regolith, complementary and overlapping work exists on metal extraction at the demonstration scale, and most of the work is in the US and Europe.
Civil Engineering and Surface Construction
To make site habitable and functional starting from a site characterized by complex shape terrains requires the detailed evaluation of the natural shape, the soil characteristics, atmospheric conditions and winds (as in the Mars case), solar exposure conditions. Distances and road practicability from the relevant raw materials and establishment and maintenance of resource sites are also key factors. Regolith shielding is a possible idea for habitats but all the related elements to make them habitable are not simple: architecture design needs to address all the constraints imposed by the habitability and ISRU facilities. A significant radiation shielding needs to be realized for long, sustained human surface exploration activities. Long-term (months years) radiation exposure limits for crew currently do not exist to properly evaluate radiation shielding requirements. These are needed to properly evaluate Earth-based and ISRU-based shielding options. Specific manufacturing methods can be used as additive manufacturing that present relevant performance and a flexible approach but may limit the architectural opportunities. Brickmaking may represent another functional method for the realization of specific architectural sections and, at the moment, an appropriate combination of these two techniques needs to be developed to reduce their limits. While there is significant interest in terrestrial additive manufacturing construction development, development for space applications has been limited and primarily under Earth-ambient conditions. Most of the current work is focused in US and Europe, with an emphasis currently on additive manufacturing approaches.
In-Space Manufacturing
Some relevant technics used for In-Space Manufacturing for ISRU are using regolith with selective laser sintering method or stereolithography-based additive manufacturing. These technologies are under development or are already demonstrated but only in terrestrial laboratory, and techniques need to be verified in reduced gravity condition, as on the International Space Station (ISS). Metals and polymers additive manufacturing techniques have been implemented or are being developed also for application in microgravity, on the ISS. Also, subtractive manufacturing systems are currently being developed for the ISS. Application for ISRU-derived feedstock should be investigated for Moon and Mars missions. Process monitoring and part verification is a key field of activity for in-space manufacturing applications. Similarly, all the techniques and methodologies enabling the possibility to recycle ISRU-derived manufactured parts should continue to be investigated, as well as the impact of multiple recycling of the parts’ properties and material processability.
ISRU Flight Missions Planning
As with any new technology, before it can be utilized in a mission critical role for human spaceflight, it needs to undergo significant ground development and adequately demonstrate its life and performance in the actual mission environment. In the report, the ISRU Gap Assessment team outlines a phased development and flight strategy to increase confidence and decrease risk in the technologies and systems required to provide useful products in a mission-critical application. The approach for risk reduction of including ISRU elements in the surface exploration architecture may ultimately come down to the potential customers. Sufficient level of confidence to fly ground demonstrated systems or to undertake intermediate technology demonstration steps in advance of operational systems should be defined by the relevant users.
While a new international human lunar architecture is still in work, it should be noted that individual nations and space agencies are progressing with plans for new lunar orbital and surface missions. Many of these missions, as highlighted in Table 11 Approved and Planned ISRU-Related Flight Missions are in planning or already underway for flight this decade.
Partnerships and Private Sector Involvement
Partnerships are a well-established means of delivering more significant mission outcomes than could otherwise be achieved by a single agency or organisation. Therefore, a key benefit is to expand inter-agency collaboration, between space agencies and also with other key government agencies, to address the ISRU gaps outlined in this report while providing socio-economic benefits on Earth. A strategic approach to expanding collaboration can encompass the following key activities: coordinated planning; shared knowledge and insights; harmonisation of research agendas; specific joint-development projects for ISRU systems; and access to shared test facilities.
More recently, the role of the private sector has evolved across a vast range of space operations and is expected to have an even greater impact on the field of ISRU. To fully benefit from further commercial involvement, this report highlights a strategic approach to leveraging the capabilities of the private sector, including both new start-ups and from mature terrestrial industries such as the global mining, civil construction, resource, and manufacturing sectors. To realize the goals of ISRU, there is a need to recognize the benefits of adapting mature and modern terrestrial industry capabilities to advance space operations. At the same time, the application of newly-developed ISRU technologies can also deliver enhanced solutions for productivity gains and address common challenges (e.g. working in harsh, hazardous, and remote environments) for terrestrial industries.
