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.