Key issues for the Japanese government regarding exploration and development of space resourcesby Akira Saito
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| Even if sufficient water ice is confirmed on the Moon, several issues remain before water ice can be used as water resources. |
However, although many studies based on remote sensing observation data have been reported, estimates of the amount of water ice present on the Moon vary widely due to differences in data analysis methods and other factors. In addition, no clear conclusions have been reached regarding its distribution and morphology. In other words, the extent to which water ice can be used as propellant is currently unknown. Japan has stated in its “Basic Plan on Space Policy” that “resource exploration will be conducted as part of scientific exploration activities beginning in the 2020s to determine the presence of resources on the lunar surface, including water resources, and to identify the potential for future use.”
Against this background, the Japan Aerospace Exploration Agency (JAXA) is planning the Lunar Polar Exploration Mission (LUPEX) in cooperation with the Indian Space Research Organisation (ISRO). The mission aims to obtain data on lunar water ice’s quantity and quality (distribution, state, morphology, etc.) to determine its availability for future exploration activities. Other countries have also planned similar missions (e.g., ISRO’s Chandrayaan-3, China’s Chang’e-6, and NASA’s Volatiles Investigating Polar Exploration Rover (VIPER) mission).
It is hoped that these missions will provide information on the quantity and quality of water ice on the Moon. However, even if sufficient water ice is confirmed on the Moon, several issues remain before water ice can be used as water resources.
To illustrate the issues, this article first summarizes the currently envisioned process for producing propellant from water ice. One possible method of extracting water from regolith is to mine the regolith and then extract the water in a plant. A technique called thermal mining, in which water is extracted by applying heat directly to the regolith without mining the regolith, is also being considered. After the water is extracted, hydrogen and oxygen are produced. The hydrogen and oxygen are then liquefied, placed in storage tanks, and loaded into a transportation vehicle to and from the Gateway and the lunar surface, or elsewhere.
In the case of regolith mining, dust could get into the machine’s working parts and cause it to malfunction. Thermal mining requires heavier equipment than regolith mining. In addition, there remain issues to be considered in other processes, such as the water extraction process.
| Developing lunar water ice as a resource only makes sense if there is a benefit to using lunar water ice over bringing propellant from the Earth. |
On the other hand, as mentioned above, Japan has enacted the Space Resources Act, and there is a growing demand to promote the development of space resources, including lunar water. Therefore, based on the above background, this article examines what important issues the Japanese government should consider in the future regarding the long-term exploration and development of space resources.
As mentioned above, in its “Basic Plan on Space Policy,” Japan has stated that “resource exploration will be conducted as part of scientific exploration activities beginning in the 2020s to determine the presence of resources on the lunar surface, including water resources, and to identify the potential for future use” and plans to conduct LUPEX to obtain water ice data. Therefore, in the future, it will be necessary to determine whether lunar water ice is sufficient as a resource, i.e., whether the development of water resources should proceed, based on the water ice data obtained through LUPEX.
This article will present some studies that have provided water content benchmarks to determine whether lunar water ice is sufficient as a resource.
It was assumed that a crewed exploration mission would be conducted once a year and that 75 tonnes of water for the mission would be generated and converted to propellant in one year. It was also assumed that propellant generation would be carried out by extracting water and producing propellant from the extracted water in a plant after mining and transporting the regolith. This study then calculated how the total launch mass varies with the presence or absence of a propellant generation plant, the number of crewed exploration missions, and the water content of the regolith. The results showed that when the water content of the regolith is greater than 0.5% by weight, the total launch mass with a propellant generation plant built on the Moon is lower than without it when the number of crewed exploration missions is four or more. In other words, in such cases, building a propellant generation plant is more efficient than not building one.
It was assumed that the process of generating 10 tonnes of water and converting it to propellant would be carried out during the period of continuous illumination in the polar regions, which is 225 days. It was also assumed that propellant production would be accomplished by mining the regolith, extracting and transporting the water, and then producing propellant from the extracted water at a plant. The study then calculated how the mass and power of the equipment involved in the above process would change depending on the water content of the regolith. The results showed that the transition in equipment mass and power between 1 and 2% by weight water content is more notable than the transition between 2and 10% by weight water content. Based on this result, this study concludes that 1% by weight is a threshold at which ISRU is unlikely. It should be noted that the reason for this result was analyzed as the size per unit exceeds the scalability limit to treat the amount of regolith required in the 1% by weight case, thus requiring multiple water extraction units, resulting in higher mass and power.
United Launch Alliance (ULA) has indicated a willingness to make a commercial deal of $500 per kilogram for 1,100 tonnes of propellant per year on the lunar surface. Based on this, it was assumed that 1,600 tonnes of water equivalent to 1,100 tonnes of propellant would be generated and converted to propellant during the year. It was also assumed that the propellant generation would be carried out in the following manner. First, sunlight is directed into a dome-like tent to heat the lunar surface directly, and the sublimated water is captured and refrozen by a cold trap connected to the tent. The refrozen ice is then transported to the plant to produce propellant. The study then calculated how the power of the equipment involved in the above process would vary depending on the water content of the regolith. The results showed that the power required to sublimate a given amount of ice increases exponentially as the water content decreases when the water content is less than 2% by weight, but when the water content exceeds 5% by weight, the power is relatively independent of the water content. Based on these data, the lower limit of acceptable water content was then determined to be 4% by weight.
Developing lunar water ice as a resource only makes sense if there is a benefit to using lunar water ice over bringing propellant from the Earth. Therefore, it is desirable to derive a benchmark by comparing the case where a propellant generation plant is constructed on the Moon with the case where no propellant generation plant is built, as in the JAXA study. Here, to use a benchmark obtained by JAXA’s method as a criterion for deciding whether or not to proceed with water resources development, it is necessary to understand the extent to which missions will be conducted in the future. However, it is difficult to predict how often missions will be conducted to which Japan’s propellant generation plant can contribute. Hence, even if the benchmark obtained by JAXA’s method can be used as a reference value, it will not be possible to judge the pros and cons of promoting the development of water resources based on this benchmark alone.
| The Japanese government should make a comprehensive decision on the pros and cons of promoting water resource development in the future based on the results of LUPEX. |
In addition, the assumptions regarding the production volume and details of the production process may change in the future, depending on the results of currently planned exploration, technological advances, and other factors. Furthermore, if sufficient information is obtained through exploration, then distribution and morphology can be considered, and it may be possible then to calculate a more appropriate benchmark. For this reason, this article will not discuss the details of the benchmark calculation but will instead examine other perspectives on the pros and cons of promoting water resources development. The perspective to be examined here is the perspective from which Japan decided to participate in Artemis. Specifically, the perspective of further deep space exploration such as Mars, the perspective of international competitiveness and presence, and the perspective of expanding a wide range of industries, including non-space fields. This article discusses the merits of lunar resource development from the above perspectives.
Suppose the potential for water resources is confirmed. In this case, it is expected that the development of technology to produce propellant by extracting lunar water to supply propellant to a transportation vehicle to and from the Gateway and the lunar surface or a lunar mobile vehicle would be promoted. If this technology is established for lunar exploration, it may be applied to further deep space exploration, such as Mars.
The technology to extract water from lunar regolith to produce propellant is important to ensure the sustainability of lunar and deep space exploration. Therefore, international cooperation in these exploration missions through this technology is expected to strengthen the international presence and provide a voice.
As mentioned above, there are many issues in the development of space resources, and it must be said that the extent to which the space resources development industry will expand is uncertain. However, the technology that makes up the propellant generation plant is expected to be applied to the hydrogen energy society on the ground. In other words, water resources development technologies can contribute to expanding a wide range of industries, not just the space sector.
In light of the above, the author believes that the Japanese government should make a comprehensive decision on the pros and cons of promoting water resource development in the future based on the results of LUPEX, taking into consideration the merits of promoting water resource development as described above, while calculating and referring to values related to water content as benchmarks, if necessary.
Next, this article examines the matters that need special attention when conducting future exploration and development.
Because countries other than Japan are also interested in lunar water ice, and because lunar water ice is unevenly distributed in the polar regions, if Japan conducts exploration or development, there is a possibility that Japanese activities and those of other countries will be conducted in adjacent locations. There is a risk of harmful interference when space activities are conducted nearby. In this regard, Article IX of the Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies (Outer Space Treaty) contains the following provision: “A State Party to the Treaty which has reason to believe that an activity or experiment planned by another State Party in outer space, including the moon and other celestial bodies, would cause potentially harmful interference with activities in the peaceful exploration and use of outer space, including the moon and other celestial bodies, may request consultation concerning the activity or experiment.”
Here, to hold consultations to avoid “harmful interference” as defined in Article IX of the Outer Space Treaty, information must be disclosed to determine the likelihood of harmful interference. Therefore, the author believes that the Japanese government should ensure that information about the contents, place, and period of Japan’s space activities is made available to the public so that other countries can determine whether there is a possibility of “harmful interference” between their activities and those of Japan.
Next, specific measures for the implementation of the above suggestion are discussed. In Japan, in addition to the Act on Launching of Spacecraft, etc. and Control of Spacecraft (Space Activities Act), the Space Resources Act applies to the exploration and development of space resources, except for those conducted exclusively as scientific research or for the purpose of scientific research. And the Space Resources Act requires that the business activity plan (purpose, period, place, methods, etc.) regarding the exploration and development of space resources be disclosed to the public, except in cases where disclosure may unjustly harm the operator’s interests. Therefore, the author believes other countries can determine the possibility of “harmful interference” by using such public information.
On the other hand, only the Space Activities Act applies to activities not covered by the above-mentioned Space Resources Act. Here, Article 34 of the Space Activities Act allows conditions to be attached to permission to manage satellites. And the author believes that the conditions for permission should include the reporting to the Japanese government of information related to the above-mentioned business activity plan (excluding information that would unjustly harm the interests of the operator if made public), on the assumption that such information will be made available to the public. This will allow other countries to determine, as in the case above, the possibility of “harmful interference.”
Article IX of the Outer Space Treaty also states that “States Parties to the Treaty shall pursue studies of outer space, including the moon and other celestial bodies, and conduct exploration of them so as to avoid their harmful contamination and also adverse changes in the environment of the Earth resulting from the introduction of extraterrestrial matter and, where necessary, shall adopt appropriate measures for this purpose.” It is expected that water resources development, even if in the demonstration and research phase, will have some impact on the lunar surface. Therefore, it is necessary to take measures to prevent “harmful contamination.” However, the specific content and level of “harmful contamination” of outer space to be prohibited under the Outer Space Treaty are not clarified in the Treaty.
| If Japan conducts exploration or development, there is a possibility that Japanese activities and those of other countries will be conducted in adjacent locations. There is a risk of harmful interference when space activities are conducted nearby. |
In this regard, the Committee on Space Research (COSPAR) has recommended since 2002 that the COSPAR Policy on Planetary Protection be widely disseminated to COPUOS and other international communities to become international standards. Considering this, a practical measure to prevent “harmful contamination” is to bring operators’ activities into compliance with the COSPAR Policy on Planetary Protection through an examination based on the Space Activities Act and the Space Resources Act.
COPUOS has also established a Working Group on the Legal Aspects of Space Resource Activities to develop recommended principles for space resource activities for the five years 2023–2027. The topics for the 2024 meeting include “the role of information-sharing in supporting space resource activities” and “environmental and socioeconomic aspects of space resource activities.” When these principles are organized in the future, Japan should implement activities with full consideration of the said recommended principles.
On the other hand, the content of the measures to be taken will vary depending on the nature of the mission and the activities of other countries. Therefore, specific measures should be adjusted based on these factors.
This article discussed how the pros and cons of promoting the use of water resources should be determined and what specific actions the Japanese government should take in conducting exploration and development. The author hopes that these activities will lead to a future of peaceful use of water resources.
JAXA. International Space Exploration Scenario (Draft) 2021. March 2022., (in Japanese)
Strategic Headquarters for Space. Policy, Government of Japan. Basic Plan on Space Policy. June 13, 2023., (in Japanese)
Makiko Otake et al. Introduction to Lunar polar exploration to evaluate the availability of water ice resources, Journal of Planetary Science Society of Japan. Planetary People – The Japanese Society for Planetary Sciences. March 25, 2019., (in Japanese)
Space Resource Development Laws Study Group. Nishimura Institute of Advanced Legal Studies Report by the Space Resource Development Laws Study Group. December 2016.
Julie E. Kleinhenz and Aaron Paz. Case Studies for Lunar ISRU Systems Utilizing Polar Water. ASCEND. November 2020.
George F. Sowers and Christopher B. Dreyer. Ice Mining in Lunar Permanently Shadowed Regions. New Space. December 16, 2019.
Dennis O’Brien. Debate and hopes for consensus at UN space resource meetings. The Space Review. August 7, 2023.
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