Prospecting – asteroid mining

It is time to invest in research that focusses on asteroid mining says Arunkumar Rathinam, PhD. candidate at the Australian Centre for Space Engineering Research (ACSER).

Asteroids are a memory of the formation of our solar system which makes their existence vitally important. Only a handful of devoted exploration missions have performed either a fly-by of an asteroid or an in-situ exploration (including rendezvous/touch-down or sample return missions). Various asteroid exploration missions are listed here. 

Of all the missions, HAYABUSA was the first to successfully bring samples of an asteroid back to Earth; currently, there are two other sample-return missions HAYABUSA-2 and Osiris-REX which are on a journey of further discovery.

Asteroids are classified into three main designations namely C-type, S-type, and M-type. About 75% of asteroids fall under the C-type category with carbon as prominent elements, around 17% of known asteroids fall under the S-type categorisation, with the prominent element being silicon. The remaining asteroids are grouped into M-type and a greater degree of unknown elements.

The physical composition of the known asteroids are mainly characterised from the observations that are either ground or space-based; they are based on three main parameters – albedo properties of the emitting surface, surface spectrum, and density. Asteroids with rich mineral deposits (including water) are considered a significant potential resource of raw materials, and are a good driver to continue to support space exploration activities. Even water extracted from asteroids can be used as rocket fuel and some asteroids with metal ore are considered worth more than the global economy.

Mining asteroids has elements of those ideas that develop from science fiction books. However, with recent engineering advancements and interests from the private organisations (such as deep space industries, planetary resources, etc.) it may soon become a reality.

As mining prospects gain interest, we need to overcome several engineering challenges and there will be a need to develop new technologies or adapt old ones. We will also need to consider the impact of working in a zero-gravity environment, the importance of regolith and rock mechanics, the need to shield against radiation, transportation of materials, the extraction process and handling dust particles, temperature and gradient cycles of asteroid surface and system thermal management.

Apart from the technical challenges, there also needs to be a feasible business plan and return on investment. While considering viable business models the key idea is In-Situ Resource Utilisation (ISRU) ( i.e. using the materials in the local environment) and how it facilitates the availability of the needed materials, such as water for future exploration missions. Currently, the economics of extracting resources from these small bodies, and bringing them back to Earth is not considered profitable. Whereas processing the resources in-situ and using these processed resources in space, rather than bring them to earth, is considered more economical. Water is considered a key resource, and extracting water on asteroids is much easier than processing metals. To extract precious metals in space new technology has to be developed to work under micro-gravity, whereas extracting water only requires heating ice-bound regolith and capturing the produced water vapour, making it reasonably feasible to achieve.

Small celestial bodies (including asteroids and comets) have a weaker gravitational field therefore close proximity navigation, of a spacecraft near an asteroid, needs extreme precision and careful planning. Exploration missions in the past have spent time characterising the asteroid’s surface and its parameters. The data was then processed at the control center in Earth and spacecraft is then kept in the loop for mission critical scenarios, however, in the future, the need for the spacecraft to be autonomous will increase. To be fully autonomous, the spacecraft needs be aware of its position, as well as the asteroid’s position and dynamics, at any given time. It should also be able to predict their future positions as well.

This seems easy on Earth, as we have a GPS or other positioning systems, combined with other inertial sensors to assist with navigation. But in deep space, it’s a risky business, with long round trip communication delay extending to ~20+ minutes, rigorous autonomous navigation is much needed.

Spacecraft should be able to use its navigation camera and other sensors to estimate its position relative to the asteroid, and it needs to be more robust, one wrong prediction and we could end up on collision course with the asteroid. With only one successful sample return mission from asteroids, spacecraft navigation is another area requiring more research.

As Australia readies to launch a national space agency, it should consider investing in research that focuses on developing future technologies, with asteroid mining being one such area where we are not far from rest of the pack.