Platinum group metals (PGMs) are among the most valuable resources in space mining, offering applications in electronics, catalysis, and aerospace. While PGMs are found in Earth's crust, their scarcity and the high cost of extraction make asteroid mining an attractive alternative. The Main Belt asteroids, located between Mars and Jupiter, contain abundant nickel-iron (Ni-Fe) alloys known as kamacite, which are rich in PGMs. However, extracting PGMs economically requires an innovative approach that minimizes energy consumption, maximizes metal recovery, and eliminates the need for costly material transport back to Earth.
In a paper by PJ Schubert, a vacuum distillation-based refining process for PGMs, integrated with a centrifugal separation system that operates within an in-situ maglev infrastructure. This method leverages asteroid microgravity, nuclear energy, and electromagnetic levitation to enable efficient large-scale metal extraction.
To extract PGMs, the asteroid metal is first broken apart using high-frequency impact hammers, which take advantage of the asteroid's extreme cold temperatures (~150 K) to make the metal brittle and easier to fracture. The shattered metal is then placed into large crucibles—heat-resistant containers designed to withstand extreme temperatures.
Since space is naturally a vacuum, heating the metal to the boiling point of nickel allows the lighter metals (nickel and iron) to evaporate, leaving behind the much heavier platinum. This process, called vacuum distillation, works without the need for complicated chemical treatments, making it a perfect fit for asteroid mining.
A key challenge in refining metal in space is keeping molten materials in place without Earth's gravity. To solve this, the crucibles are mounted on a magnetic levitation (maglev) track that encircles the asteroid. As the crucibles move along the track at controlled speeds, centrifugal force keeps the heavier platinum securely inside while the evaporated nickel and iron settle back onto the asteroid’s surface, forming a protective metal shell.
This setup not only refines the precious metals efficiently but also recycles the common metals, preventing waste and creating potential building materials for future space structures.
To power this refining system, a nuclear thermal reactor generates heat, ensuring continuous operation without relying on solar energy. The entire process can be automated, with robotic systems handling metal collection, processing, and refining, reducing the need for human presence in space.
Platinum is extremely valuable, selling for over $30,000 per kilogram on Earth. Mining asteroids directly in space eliminates the cost of transporting massive amounts of raw material, as only the refined PGMs need to be sent back. Additionally, the process creates a self-sustaining system, with reusable materials and energy sources that could support long-term space industries.
By developing this refining technology, asteroid mining could provide a steady supply of rare metals, supporting advanced electronics, space travel, and even the construction of off-world colonies.
The extraction of platinum from Main Belt asteroids is both practical and economically viable using vacuum distillation and centrifugal refining. By leveraging space’s natural vacuum, nuclear energy, and automated systems, we can efficiently mine, refine, and transport valuable metals, paving the way for a new era of space-based industries.