Solar cell manufacturing using lunar resources

Conceptual rendering of a Blue Alchemist solar cell fabrication facility on the Moon. Credits: Blue Origin

Jeff Bezos’ new initiative called Blue Alchemist made a splash last month boasting that the team had made photovoltaic cells, cover glass and aluminum wire from lunar regolith simulant. This is an impressive accomplishment if they have defined the end-to-end process which (with refinements for flight readiness) would essentially provide a turnkey system to fabricate solar arrays to generate power on the Moon. The announcement claimed that the approach “…can scale indefinitely, eliminating power as a constraint anywhere on the Moon.” Actually, this may not be possible at first for a single installation as surface based solar arrays can only collect sunlight during the lunar day and would have to charge batteries for use during the 14 day lunar night, unless they were located at the Peaks of Eternal Light near the Moon’s south pole. But if scaling up manufacturing is possible, coupled with production of transmission wire as described, a network of solar power stations in lower latitudes could be connected to distribute power where it is needed during the lunar night.

Very few details were revealed about the design outputs of the end products (not surprisingly) in Blue Origin’s announcement, particularly the “working prototype” solar cell. An image of the component was provided but it was unclear if the process fabricated the cells into a solar array or if the energy conversion efficiency was comparable to current state of the art (around 21%). Nor do we know how massive the manufacturing equipment would be, how much periodic maintenance is needed or if humans are required in the process. Still, if a turnkey manufacturing plant could be placed on the Moon and it’s output was solar arrays sourced from in situ materials, it would significantly reduce the costs of lunar settlements by not having to transport the power generation equipment from Earth. This particular process has the added benefit of producing oxygen as a byproduct, a valuable resource for life support and propulsion.

Research into production of solar cells on the Moon from in situ materials is not new. NASA was looking into it as recently as 2005 and there are studies even dating back to 1989. Blue’s process produces iron, silicon, and aluminum via electrolysis of melted regolith, using an electrical current to separate these useful elements from the oxygen to which they are chemically bound. Solar cells are produced by vapor deposition of the silicon. The older studies referenced above proposed similar processes.

It would be interesting to perform an economic analysis comparing the cost of a solar power system supplied from Earth by a company focusing on reducing launch costs (say, SpaceX) with that of a company like Blue Origin that fabricated the equipment from lunar materials. Peter Hague has done just that in a blog post on Planetocracy using his mass value metric.

Hague runs through the numbers comparing SpaceX’s predicted cost per kilogram delivered to the Moon by Starship with that of Blue Origin’s New Glenn. At current estimates the former is 5 times cheaper than the latter. Thus, to best Starship in mass value, Blue Alchemist would have to produce 5kg of solar panels for every 1kg of equipment delivered to the Moon, after which it would be the economic winner. Siting a recent analysis of lunar in situ resource utilization by Francisco J. Guerrero-Gonzalez and Paul Zabel (Technical University of Munich and German Aerospace Center (DLR), respectively) predicting comparable mass output rates, Hague believes this estimate is reasonable.

Perhaps we should not get ahead of ourselves as Blue Origin’s timeline for development of their New Glenn heavy-lift launch vehicle is moving a glacial pace and one wonders if they have the cart before the horse by siphoning off funds for Blue Alchemist. Jeff Bezos is free to spend his money any way he wishes and definitely seems to be in no hurry.

Conceptual illustration of New Glenn heavy-lift launch vehicle on ascent to orbit. Credits: Blue Origin

But SpaceX’s Starship has not made it to space yet either and after we see the first orbital flight, hopefully as early as next week, the company will have to demonstrate reliable reusability with hundreds of flights to achieve economies of scale commensurate with their predicted launch cost of $2M – $10M. As SpaceX has demonstrated with it’s launch vehicle development process it is not a question of if, it is one of when.

Image of full stack Starship at Starbase in Boco Chica, TX. Credits: SpaceX

As both companies refine their approach to space development, will it be the tortoise or the hare that wins the mass value price race for the cheapest approach to power on the Moon? Or will each company end up complementing each other with energy and transportation infrastructure in cislunar space? Either way, it will be exciting to watch.

Mass value: metric for space settlement

Image credit: Richard Bizley, bizelyart.com / National Space Society

In a paper published in New Space last March, Peter Hague describes a figure of merit he developed to drive policy decisions to help accelerate space exploration and space settlement. The aim of the paper was to generate a single metric for every potential space mission on a common scale for comparison purposes. This ‘mass value’ is the amount of mass that would need to be placed in low Earth orbit (LEO) to perform the same mission using a baseline method. That method would use only storable propellants and Hohmann transfer orbits – no gravity assists, aerocapture, high energy propellants or ISRU.

This approach puts a price on all the add-ons which expand the mission beyond the baseline. One can then use a single normalized scale to calculate how much mass to LEO you would save by making propellant on Mars for example, or by taking advantage of a certain launch window to get a gravity assist.

A hands-off government entity could subsidize space expenditures at a flat rate per kg of mass value, confident they are promoting space development without having legislators involved in engineering decisions.

Aggregating all the missions by a nation, company, or other entity could be used to calculate an analogue of GDP for a space civilization. While this does not measure everything we care about – scientific merit, human occupation, etc – neither does GDP. It does capture the overall capability to move around the solar system; and as such, is as useful for charting our journey to becoming a Type II civilization on the Kardashev Scale as it is for analyzing individual missions.

Thanks to Peter Hague for the material in this post. We’ve heard a rumor that there may be a book forthcoming on the subject. Looking forward to it!