View from North America
Gallium arsenide solar cells power the Orion space probe. Photo; NASA
Dear Members,
I trust this missive finds everybody safe and well.
Polina and I have been chatting over several weeks and have come up with a great “theme” that we shall be following in The Crucible as the year progresses: The Space Race and Minor Metals. As she put it to me: “It looks like 2024 has the makings of being a space race year, and there are launches happening all around.” So, I thought I would kick things off with a quick look at that favourite metal of mine: gallium.
But, first I thought it worth noting that, as part of its continuing support of the critical minerals industry (and its Critical Mineral Strategy), the Australian Government has recently granted just short of A$22 million: ANSTO¹ – A$14 million; CSIRO² – A$5 million; and Geoscience Australia – A$2.7 million. This organization will, among other things, look at any opportunities there may be to establish a domestic gallium industry. (Perhaps a sensible good idea following last year tightened control over its exports of gallium and germanium).
Gallium in Space
Gallium Arsenide (GaAs)
For a number of years now GaAs solar cells (GaAs-based thin-film technology has been around now for over 50 years³) have been used in satellites. Not least because they are durable (in particular, resistant to gamma radiation), highly efficient (among other things, they have high spectral coverage) and lightweight. They have also been used in other space “objects” such as probes (the Venusian probe Akatsuki) and the Hubble telescope.
Going forward, some interesting opportunities, especially for further space use, could lie in combining concentrators with multi-layered GaAs cells, not least when it comes to miniaturization. As noted in the paper cited below: “Miniaturization of concentrators can be used (and already is used) in space technologies, where GaAs cells make the most sense in terms of their good resistance to radiation and their ability to withstand very high-temperature fluctuations.”
Gallium Nitride (GaN)
Hardly an exciting subject to most when it comes to space travel, power management is a space vehicle is, of course, of critical importance. Here, wide bandgap semiconductors like GaN continue to offer interesting opportunities, both in terms of enhanced efficiency and cost reduction. In addition to power capability (both microwave and DC), as with GaAs, GaN can offer not only high temperature (and frequency) operation, but also radiation insensitivity. And, in addition to proven reliability, in terms of the three most important elements in a space vehicle — SWaP: Size, Weight and Power efficiency — the weight and size of GaN power devices continue to offer some notable advantages.
However, when it comes to GaN in particular, what caught my eye back in December 2023 was a piece published by the European Space Agency (ESA) about its recently launched PVCC (Proba-V Companion Cubesat). (The agency had already published an interesting piece a number of years before entitled: “Improved gallium nitride recipe could spark space communication revolution” in which it described some recent advances in GaN technology what were “ … promising a five- to tenfold improvement in satellite signal strength and data rates”.)
The proof appears to be in the pudding! It turns out that, in addition to a GaAs X-band transmitter, the newly-launched satellite is also employing a second “high performance low recurrent cost” X-band transmitter, “compatible with data rates up to 100 Mbit/s”. This one using a new GaN RF power amplifier developed as part of the ESA’s GREAT2 (GaN Reliability Enhancement and Technology Transfer Initiative) project launched in 2008.
I think it is worth quoting directly from the latest ESA piece: “Gallium nitride has been described as the most promising semiconductor since silicon, capable of operating at much higher voltages and temperatures than comparable materials. As an additional advantage, GaN also possesses inherent resistance against the radiation encountered in space” And Andrew Barnes, overseeing ESA’s work in GaN: “In terms of communications for space, GaN offers a five- to ten-fold increase in communications power, while requiring no additional cooling systems”.
Finally, one exciting thing I read recently was about the use of gallium “in space” as a propellant in miniaturized Field Emission Electric Propulsion (FEEP) units, nanoFEEps, for orbital and attitude control of CubeSats. (See above.) While I know Morpheus Space, German company that manufactures these, used to use gallium, I don’t know if it still does. I couldn’t find information on anybody else developing such technology. But, if it does work (it’s used by the ESA), maybe we’ll see more mentions soon.
Over the coming months, we’ll look at the use, in space, of further minor metals and technologies associated with them.
In the meantime, though, from a snowy Cleveland Heights, Ohio, I remain, as always
Yours
Tom Butcher ©2024 Tom Butcher
Tom Butcher is Director of ESG at Van Eck Associates Corporation (“VanEck”). The views and opinions expressed herein are the personal views of Tom Butcher are not presented by or associated with VanEck or its affiliated entities. Please note that VanEck may offer investments products that invest in the asset class(es) or se-curities mentioned herein. This is not an offer to buy or sell, or a recommendation to buy or sell any of the securities/financial instruments mentioned herein.
¹ ANSTO: Australian Nuclear Science and Technology Organisation
² CSIRO: Commonwealth Scientific and Industrial Research Organisation
³ Papež N, Dallaev R, Ţălu Ş, Kaštyl J. Overview of the Current State of Gallium Arsenide-Based Solar Cells. Materials (Basel). 2021 Jun 4;14(11):3075. doi: 10.3390/ma14113075. PMID: 34199850; PMCID: PMC8200097
