Helium‑3 from the lunar surface for nuclear fusion ?

Since 1969, the return of a human mis­sion to the Moon has never see­med so close. Although scien­ti­fic inter­est conti­nued to flou­rish, space pro­grammes had for many decades aban­do­ned it in favour of the Inter­na­tio­nal Space Sta­tion and mis­sions to explore the solar sys­tem. Domi­na­ted by the gro­wing com­pe­ti­tion bet­ween the Uni­ted States and Chi­na, the return to the Moon is now moti­va­ted by a desire to stu­dy and pos­si­bly exploit resources that can be found there.

Of these, helium‑3 repre­sents the most signi­fi­cant poten­tial in the field of ener­gy. This non-radio­ac­tive iso­tope is an ideal fuel for the ope­ra­tion of a fusion reac­tor ; it consists of fusing helium‑3 with deu­te­rium, with the advan­tage of not pro­du­cing neu­trons. Whil­st it is still in its expe­ri­men­tal stages, the abi­li­ty to contain such ener­gy in the reactor’s contain­ment cham­ber could make it a viable ener­gy source.

In Sep­tem­ber 2021 US com­pa­ny, Com­mon­wealth Fusion Sys­tems based in Mas­sa­chu­setts, announ­ced the crea­tion of a 20 Tes­la magne­tic field using a high-tem­pe­ra­ture super­con­duc­ting elec­tro­ma­gnet, which consti­tutes a remar­kable advance. From this pers­pec­tive, the extrac­tion of helium‑3 on the Moon could faci­li­tate the deve­lop­ment of this break­through technology.

As ear­ly as 1988, a NASA report on helium‑3 men­tio­ned the poten­tial of this iso­tope for use in a nuclear fusion reac­tor¹. Theo­re­ti­cal­ly, it offers seve­ral advan­tages com­pa­red to cur­rent nuclear power as an abun­dant, low-car­bon ener­gy and no nuclear waste tech­nique. On paper, its advan­tages make it a com­pe­ti­tive resource, while this iso­tope is use­ful for other appli­ca­tions inclu­ding cryo­ge­nics, quan­tum com­pu­ters and MRI lung ima­ging. Also, the Moon is its main reservoir.

For bil­lions of years, the action of solar wind has relea­sed high-ener­gy par­ticles, inclu­ding helium‑3, which has accu­mu­la­ted on the Moon in the absence of an atmos­phere. A rene­wable resource by defi­ni­tion, the iso­tope is regu­lar­ly depo­si­ted on the Moon’s sur­face under the constant acti­vi­ty of the Sun. Howe­ver, as Ian Craw­ford shows, the notion of the abun­dance of this resource must be wei­ghed up : the highest concen­tra­tion obser­ved in mea­su­re­ments car­ried out on samples is 10 parts per bil­lion (ppb), depen­ding on the mass, for an ave­rage concen­tra­tion of 4 ppb in the rego­lith layer².

As a pre­re­qui­site for the ins­tal­la­tion of a human base, many states (India, Rus­sia, Chi­na, Uni­ted Arab Emi­rates, etc.) are pre­pa­ring new lunar mis­sions in the coming years. By far, the Arte­mis pro­gramme, sup­por­ted by NASA, is the most suc­cess­ful at this stage for this plan­ned return. Along­side the Uni­ted States, many coun­tries such as Aus­tra­lia, Bra­zil, Ita­ly, Japan, and Luxem­bourg have joi­ned this ambi­tious pro­ject. Chi­na, toge­ther with Rus­sia, is also consi­de­ring the esta­blish­ment of a lunar base. Howe­ver, the spe­ci­fi­ca­tions for such an under­ta­king remain incom­plete for the time being, both in terms of the finan­cial resources and the tech­ni­cal arran­ge­ments to reach the tar­get set for 2030.

Clear­ly, a per­ma­nent ins­tal­la­tion requires the construc­tion and main­te­nance of infra­struc­ture through the use of local­ly avai­lable resources and the inten­sive use of robots. In this regard, the Aus­tra­lian com­pa­ny Luy­ten is loo­king to deploy 3D prin­ting tech­no­lo­gy to pro­vide on-site construc­tion solu­tions³. In other words, the aim is to imple­ment an arti­fi­cial lunar eco­sys­tem to faci­li­tate tra­vel to Earth. To achieve this ambi­tion, the French incu­ba­tor Tech­The­Moon, based in Tou­louse, is the first in the world dedi­ca­ted to deve­lo­ping a per­ma­nent set­tle­ment on the Moon⁴. Des­pite this emu­la­tion, the esta­blish­ment of a human colo­ny remains a dis­tant pros­pect. A recent NASA audit report points to cumu­la­tive delays in the Arte­mis pro­gramme, par­ti­cu­lar­ly in the deve­lop­ment and tes­ting of the lunar module, which de fac­to post­pones the mis­sion beyond 2024⁵.

Chi­na has demons­tra­ted a meteo­ric rise in its space acti­vi­ties hea­ding towards the moon – both eco­no­mi­cal­ly and tech­no­lo­gi­cal­ly. As a fun­da­men­tal step in the deve­lop­ment of its space pro­gramme, Chi­na sent its first probe into orbit around the Moon in 2007. Since then, the Chang’e 4 (2018) and Chang’e 5 (2020) mis­sions have made signi­fi­cant pro­gress in the know­ledge and stu­dy of data on the topo­gra­phy and com­po­si­tion of the soil. One of the objec­tives of these trips is to deter­mine the exact amount of helium‑3 present. To this end, the Bei­jing Research Ins­ti­tute of Ura­nium Geo­lo­gy (BRIUG) is mea­su­ring the content of helium‑3 in the lunar soil, eva­lua­ting its extrac­tion para­me­ters, and stu­dying the ground fixa­tion of this iso­tope. These advances also reflect Bei­jing’s ove­rall stra­te­gy to control ter­res­trial mine­rals and metals and their use.

Ove­rall, other coun­tries are fun­ding pro­grammes to ana­lyse the lunar soil, such as the future mis­sion of the first Emi­ra­ti rover sche­du­led for 2022⁶. With the help of the Japa­nese com­pa­ny Ispa­ce’s lunar lan­der, the ‘Rashid’ rover will stu­dy its geo­lo­gi­cal com­po­si­tion and pro­per­ties. These mis­sions will undoub­ted­ly help to assess its mining potential.

Scien­ti­fic mis­sions are bound to conti­nue over the next decade to conti­nue sur­veying rego­li­thic rocks in new lunar ter­ri­to­ries. This is an inva­luable piece of scien­ti­fic infor­ma­tion that reflects one of the foun­da­tions of the human space explo­ra­tion ; based on the pos­si­bi­li­ty of exploi­ting extra­ter­res­trial resources that appear to be unli­mi­ted. In any case, the deve­lop­ment of an extra-ter­res­trial mining indus­try entails invest­ment and infra­struc­ture constraints such that the deploy­ment of exis­ting rene­wable resources on Earth would remain less cost­ly. In fact, the ener­gy cost of lunar helium‑3 – from extrac­tion to use in a nuclear fusion reac­tor – would make it at most a rather mar­gi­nal contri­bu­tion to our long-term ener­gy needs.

While exis­ting tech­no­lo­gi­cal and finan­cial bar­riers osten­si­bly hin­der the launch of such a ven­ture out­side the Earth sys­tem⁷, sus­tai­ned research and deve­lop­ment poli­cies in seve­ral coun­tries are in this sense a way of kee­ping the pos­si­bi­li­ty open. All in all, this fea­si­bi­li­ty could be unra­vel­led when a tech­no­lo­gi­cal thre­shold is cros­sed that cor­re­lates with its eco­no­mic pro­fi­ta­bi­li­ty. Final­ly, cur­rent inter­na­tio­nal trea­ties do not pro­vide a poli­ti­cal and legal fra­me­work for mining acti­vi­ties on the Moon. In the mean­time, thought must be given to the sta­tus of the celes­tial object, which could ulti­ma­te­ly be like that of Antarc­ti­ca, by beco­ming a neu­tral space dedi­ca­ted to science.