Abigail Calzada

The term resource has both a geological and an economic component. It must exist in sufficient concentration to be useful and there should be indications that its extraction could be technically and economically feasible.

The helium-3 was one of the first elements proposed back in in the 20th century as an useful resource to be extracted to the Moon because its potential as nuclear fusion fuel. Surprinsingly, the nuclear physics community do not show the same excitement about helium-3 than that shown by the space community. In this post, I explain briefly the physics and prospects of the nuclear fusion using helium and the quantities of the element that can be found on the Moon.

Nuclear Fusion

During the nuclear fusion two light atomic nuclei collide to produce a single heavier one releasing energy in the process. This energy is generated because the mass of the product is less than the sum of the mass of the original particles, and because the mass-energy equivalence principle, part of extra mass is transformed into energy. This is the reaction that occurs in the Sun and all the stars. Current research is focusing on industrializing this process to have a sustainable energy source, avoiding pollution and contributions to the climate change.

The fusion reaction (Figure 1) happens in a vessel called tokomak. There, hydrogen isotopes deuterium (D) and tritium (T) are confined and heated in a plasma. To confine the plasma and maintain its stability a powerful magnetic field is used. The DT reaction produces helium-4, a neutron and energy. The energy produced is absorbed as heat within the reactor’s walls producing steam that through turbines and generators creating electricity.

The problem with DT fusion reaction is the neutron emission. Neutrons are considered radioactive contamination as they are life-threatening and very damaging for the surrounding materials. Because their lack of electrical charge, neutrons are very difficult to contain by the tokamak’s electromagnetic field and efforts on research for shielding materials are in development.

There are other fusion reactions that could generate energy without the dangerous neutron emission. In this reaction the helium-3 reacts with deuterium and emits helium-4, a proton and energy (figure 2). Protons emitted during this type of fusion are easier to contain by electromagnetic fields. Furthermore, the momentum energy of the protons interacting with the electromagnetic field in theory will result in direct net electricity generation making unnecessary to heat water to move any turbine.

And this is why the helium-3 is so interesting. It is clean and perfect, isn’t it?

Well, unfortunately, it is not that easy.

The DHe-3 fusion requires the two fuelling components to be mixed and despite the theory, in the practice some deuterium-deuterium reactions will happen. This will form some tritium and protons. Because deuterium reacts 100 times faster with tritium than with helium-3, the tritium will interact with the some of the existing deuterium, generating helium-4 and neutrons. So, this reaction is not as clean as claimed and still shielding for the reactor are required to avoid radioactive contamination.

But the main technical challenge for helium-3 fusion is the temperature. These temperatures need to be up to 4 times larger than those (already extremely high) needed for the DT reaction (figure 3). Furthermore, at those temperatures the plasma tends to lose lot of energy by two types of radiation: bremsstrahlung created when the plasma’s particles are slowed down, and synchrotron radiation created by the motion of the particles within the magnetic field. These two types of radiation are affected differently by temperature so the temperature in the reactor should be high enough but not too much, to reduce the bremsstrahlung and the synchrotron radiations. But even in that case, unlike the DT fusion, some radiation losses will happen.

Research on nuclear fusion is already favoring DT reactions over helium-3 for several reasons including isotopic reactivity and technical feasibility. This trend does not seem to change any time soon so, prospects on industrial nuclear fusion of helium-3 appears very far. Radioactive contamination is no doubt an important problem to solve, but it seems that many investigations on promising shielding materials are already working on it.

Fusion fuels

On the Earth, deuterium occurs naturally on the oceans with a deuterium to hydrogen ratio of 1.6 × 10^-4. For industrial and military purposes, the cheapest way to produce deuterium in bulk is separating the heavy water fraction contained in ordinary water using distillation, Girdler sulphide process, or other methods.

Tritium is a radioactive and rare isotope of hydrogen that virtually does not occur naturally on the Earth’s surface and only small traces can be found on the atmosphere. It is used to enhance the efficiency and yield of fission and thermonuclear bombs. As it does not occur naturally, it needs to be manufactured, being the most common method the neutron activation of Lithium-6 within a breeder blanket. For proposed nuclear fusion applications lithium-bearing ceramics pebbles are being developed for T breeding within a ⁴He-cooled pebble bed.

Helium-3 is a stable isotope existing in its current form since the solar system was formed. It exists both on the Earth’s atmosphere and on the mantle although their abundances are very low. On the atmosphere abundances are about 7.2 parts per trillion (ppt).  On the terrestrial mantle releases from deep-source hotspot volcanoes, mid-ocean ridges and around subduction zones suggest an approximately content ranging between 0.1 to 1 megaton.

Helium-3 can be created by decay of tritium. Actually to date, the principal source of helium for human applications is formed in nuclear weapons reservoirs. When the tritium used in the stored warheads decays into helium-3, reduces their efficienty and is constantly removed from the weapons reservoirs and marketed for other applications. International treaties such as the Treaty of Non-Proliferation of Nuclear Weapons (NPT) aiming to reduce the ready-to-use storage of nuclear warheads as well as the increasing demand of helium-3 for neutron radiation detectors and medical diagnostic technologies, has caused the diminishment of the already small stockpiles.

To summarize, on the Earth helium-3 in the atmosphere is tiny, the mantle is inaccessible, and humans produce very little to supply an increasing demand.

Lunar helium-3

My starting point is that it is not foreseen a large demand of helium-3 in the near or mid term for nuclear fusion. But I would like to write this section nonetheless for you to visualize the quantities of helium-3 present of the lunar regolith, and what would imply to extract it.

The amount of helium-3 in the lunar regolith is governed by 3 factors: solar wind implantation, maturity of the regolith, and ilmenite content. Because the lack of atmosphere or magnetic field, the elements carried by the solar wind, including He, can get implanted in the first µm of the regolith layer and incorporated into the existing mineral phases. The longer the regolith is exposed to the solar wind (maturity), the higher the amount of helium-3. The mineral ilmenite (FeTiO₃) present in the high-Ti basalts on the lunar maria appears to be remarkably good at retaining it. Once implanted, those ³He-bearing particles may have migrated to lower levels by regolith reworking thanks to impact processes. The higher lunar helium-3 abundances are expected to be found in mature regolith with high ilmenite contents i.e., high-Ti mare basalts.

Work done by Fa and Jin (2007 and 2010) using remote sensing and solar wind flux models, have estimated helium-3 lunar abundances to reach up to 20 parts per billion (ppb) in some maria (figure 4). However, this content was estimated using remote sensing techniques and models that includes many optimistic assumptions on ilmenite retention, outgassing and vertical mineral transportation. Measurements on Apollo samples from high-Ti regions have given much lower content (<10 ppb). In any case, Fa and Jin estimate a total content of 6.6 × 10⁸ kg in the entire Moon.

But

Helium-3 is not homogeneously distributed within the Moon and the most promising deposits because abundances and extension, would be the high-Ti basalts at Mare Tranquillitatis and Oceanus Procellarum (figure 4 delineated in white). Those two deposits combined would yield a mass of 2 × 10⁸ kg (20 ppb and 3 m depth; Crawford, 2015). 

There is no doubt that there are more helium-3 on the Moon than on the Earth, but it is far from being abundant. Direct deposit evaluations could be done in the entire regolith layer to understand its distribution with depth and sample measurements taken, but it is very unlikely that they will give us much higher concentrations that those estimated.  

The exercise I propose here is to estimate the rate of helium-3 extraction that will be required, to feed a nuclear fusion plant to provide energy to Germany.

To obtain 10 tonnes, it will be necessary to process an area of 221 km² of bulk regolith from Tranquillitatis or Procellarum to a depth of 3 m. I want to highlight that this is a very optimistic scenario. It is likely that the helium-3 is confined to the first cms of the regolith, in this case the area to be processed will increase significantly.

Operationally, this means it will be necessary to process 75 thousands of m³ of regolith per hour (!!) to get to 10 tonnes per year (undercalculated, probably would be more). This mass flow is probably impossible to achieve even in the most advanced mining processing plant.

Some would argue that still quantities required for other applications are much lower, so maybe there is still hope for the lunar helium-3 economy. However, because its scarcity, researchers have already started to investigate alternatives. For example, neutron detectors based on ¹⁰B and BF₃ and particle detectors like Medipix (Jakubek et al. 2006) are commercially available. In medical MRI devices, nitrogen can be used for cooling the scanner magnets and many gas chromatography laboratories are changing from helium to hydrogen because its lower cost.

Theres is only one case I coud imagine that maybe has some interest. During the processing of regolith for other resources, helium-3 can be released as by-product. In that case, maybe that tiny amount still can be used on the Moon or marketed somehow.

Bibliography

Crawford I. A. (2015). Lunar Resources: A Review. Progress in Physical Geography: 39(2) 137–167

Fa W and Jin Y-Q (2007). Quantitative estimation of helium-3 spatial distribution in the lunar regolith layer. Icarus 190: 15–23.

Fa W and Jin Y-Q (2010). Chinese Science Bulletin: 55, 4005-4009.

Jakubek J., Holy T., Lehmann E., Pospisil P., Uher J., Vacik J., and Vavrik D. (2006). Neutron imaging with Medipix-2 chip and a coated sensor. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment: 560 (1), 143-147.

Schmitt HH (2006) Return to the Moon. New York: Copernicus Books.

https://scipython.com/blog/plotting-nuclear-fusion-cross-sections/

Asturias is a region in North Spain with a long history in coal mining and the steel industry, and severely hit by the lasts economic crisis. However, Asturians are people that doesn’t give up easily, they are innovative and they have a deep understanding of technologies and the industry (thanks to the University of Oviedo and its amazing engineering, mining and sciences departments, as well as the international companies that choose Asturias to establish their research centers). Thus, Asturias offers a great environment for technology innovation, an amazing quality of life and well, Asturian food).

Asturias is currently looking to the future and exploring new opportunities. These are mostly linked to telecommunications and digitization, and take advantage of the capacities already developed in the region (5G and cybersecurity laboratories, public and open narrow band for IoT, among others). The Asturias’ public university (University of Oviedo) has also shown interest in innovation on space resources and technologies by creating the Institute of Space Sciences and Technologies and a new postgraduate program on Space Sciences and Technologies. This seems an interesting starting point to make Asturias an attractive location to develop NewSpace companies.

In this context, the Asturias’ Department of Science, Innovation and Universities is launching a Preliminary Market Consultation to create (1) a test bench for rocket engines and (2) a test bench for nanosatellites.

Test bench for rocket engines: Asturias is considering the creation of a mobile test bench for small rocket engines ( thrusts between 1 to 20 kg ), no larger than a ship container, with associated power supply and monitoring systems, and preferred using materials that promote circularity.

Test bench for nanosatellites: The challenge is to propose a mobile test bench for nanosatellites, again no larger than a ship contained and that includes: guidance control, solar and magnetic field simulators, vacuum environment, and thrust gauges.

All the information can be found here, unfortunately it is only in Spanish and they only accept proposals in Spanish. However, let me know if you have any question, maybe I can help.

Last 24th of September Europe celebrated the European Researches’ Night. I was invited to participate with a video about my experience as a woman in science. The project called En Profundidad (In Deep) was organised by Women in Mining and Industry Spain in collaboration with the Ilustre Colegio de Geólogos (ICOG Spanish National Geologists Association) and the ENGIE Project (Empowering girls to become the geoscientists of tomorrow).

I would like to share with you my video because I believe in the importance of showing women doing science but also in the necessity of speaking out about the challenges and drawbacks that thousands of women face in research everyday.

It is possible to watch the video in Spanish with English subtitles in YouTube.

I have never participated in a podcast before so when Vivek Dahiya invited me to participate in his Sci-IA Podcast I couldn’t say no. It was a very enjoyable experience. Viverk and I talked about the Moon, space exploration, the future, and even about philosophy!

Here is the youtube video if you want to see the complete interview (apologies about the dark illumination at the end, the light bulbs in my office decided stop working).

You also can listen this and many other episodes of The Sci-IA Podcast at Buzzsprout, Apple Podcast and Spotify Podcast.

Last Saturday I had the honour to be invited to participate as a keynote speaker and panelist in Space Generation (SG) Egypt’s first event ever: “Egypt’s Next Frontier“. I was very lucky to be surrounded by knowledgeable panelists from whom I learned a lot, and it was wonderfully moderated by Mina Takla, SG Egypt Program Lead and National Contact for Moon Village Association (MVA) Egypt. I must say that I enjoyed it greatly and I am sure that this is only the first of many SG -MVA events to come in Egypt. Egypt’s Next Frontier also gave me the perfect opportunity to learn more about the Egyptian Space Agency (EgSA) and their plans for this decade.

Egypt has already developed and launched many satellites and cubesats successfully. They also have a program called Egyptian University Cubesat (EUC) helping students to do their thesis on cubesat subsystems, raising awareness on space topics and establishing space laboratories in universities and schools. In the recent years EgSA is looking beyond launching satellites to promote research (emphasizing space medicine), increase diversity in the space sector, become an important contributor to international space policy, and develop space missions (including to the Moon!). They are also upgrading their capacity building and industrial facilities to support the growth of the commercial space industry. And not only that, by 2030 there are plans to send the first Egyptian astronaut to space.

EgSA has signed a MOU with the MVA-Egypt to organize public awareness and space outreach campaigns on social media, webinars with experts recognized worldwide, and develop smallsat mission proposals for EgSA to consider. This organization has over 40 volunteer Egyptian students and young professionals publishing high-quality articles in important conferences such as the International Astronautical Congress.

Last Saturday, I met some of the current and future Egyptian space professionals and I experienced their enthusiasm and commitment for space. It was a pleasure to hear about all the work they are doing and I can’t wait to hear more from Egypt’s space achievements.

EgSA: egsa.gov.eg

MVA: https://moonvillageassociation.org/

SGAC- Egypt: https://spacegeneration.org/regions/middle-east/egypt

Also, MVA and SGAC Egypt can be found on Facebook.

When I started my PhD I was expecting to develop a career in academia. To be honest, it didn’t seem to be many other options out there for a Doctor in Lunar Geology. As my PhD years were going by, I met more and more business people and engineers involved in what is called NewSpace, specifically lunar resource exploration companies. Most of those entrepreneurs, CEOs, and business developers I’ve met were people with admirable visions but it shocked me how many of them lacked of basic understanding of the lunar environment and its resources to make their businesses minimally realistic.

As a geologist, I was trained to work with the private industry. There is no oil, mining, civil engineering or construction company that does not have geologists playing fundamental roles. Why should resource exploration companies be different?

It’s not a secret that I was hired by ispace not many months after handing my PhD final thesis. I was, to my knowledge, the first lunar geologist hired full-time by one of these companies. Without any precedent, we had to came up with what should be my responsibilities and my everyday duties. Needless to say that for me it was very important to prove that there was a place for planetary geologists in NewSpace.

I doubt that there is anybody who knows more about the lunar environment, resources and surface than a lunar scientist. A good understanding of these three aspects of the Moon are critical for the success of your mission. A planetary scientist could contribute to the definition of the objectives, the payload and the landing areas of your mission, maximizing your exploration results and minimizing the risks.

Planetary researchers have, as any other professional group, their own jargon and expectations that could be similar or completely opposite to those of your company. Having a scientist will help you to translate that latest research article into plain language. A question that I’m always asked at the office when a new lunar article comes up is “Could you explain us this article and the implications that this new discovery could have for us?”

I also encountered many researchers with questions and concerns in certain aspects of NewSpace companies. This distrust is mainly caused by not considering scientists in the company’s communication strategy. Having a purely business pitch in a scientific space resources conference could be counterproductive if the speaker doesn’t have basic knowledge of the science and doesn’t take into account the characteristics of the audience.

Adding the perspective of a planetary scientist will also help you to identify needs that your company could solve and turn it into a profitable business area. Being a scientist requires skills such as observation, problem identification, creativity, proposal writing, and many others that are in demand when you want to develop an innovative business.

There are many ways how a planetary scientist could add value to a NewSpace company and there are many of them looking to get into the space resource industry. If you are interested in meeting some, I’d love to introduce you.

Thank you for visiting my website!

I’m Abigail Calzada and I’m very excited to finally share with you my new digital home.

I’ve been working in lunar science and lunar resources for more than 10 years, the last 4 in NewSpace company ispace, and after all these years I kept thinking what else I could do to promote the sustainable exploration and use of our Moon. During the past months on my maternity leave, I had the time to reflect on what type of project I would really enjoy and will contribute to that mission. And that’s how this website was born.

Here, you will find informative content centered on the science, technology and business that drives lunar exploration. But also, I will keep you informed about my attendance and participation in conferences, interviews and other events. I’m looking forward to share with you what I’ve been learning during all these years of commitment to space exploration. I hope you enjoy them and join me in this adventure.

Before I end this post, I want to give a big “thank you” to a group of women (and a man) that have been guiding me so I can shape all the ideas that were on my mind into this project.

We are going to the Moon, this time to stay. We are truly living inspiring times!