Video: How to get Water from Asteroids – Optical Mining

Most people interested in asteroid mining know companies like Deep Space Industries and Planetary Resources. Another company, Trans Astra, is less well known, but not less spectacular. Trans Astra does not seem to be backed by billionair entrepreneurs, nor does it run a sophisticated public relationships program or have a mission plan. It does however perform very tangible and credible field experiments with respect to resource extraction techniques. The company was started in 2015 by Joel Sercel, a talented engineer with a proven track record in innovation and deep interest in satellites and space missions.

One of Joels innovative plans to use “optical mining”, which harnesses the power of the sun to break rocks and release volatiles, such as water. This water can subsequently be used to fuel the mining vehicle or other space travelers (i.e. NASA, JAXA, SpaceX or commercial satellites beyond LEO), called the Asteroid Provided In-Situ Supplies (APIS) concept.

The idea is to capture relatively small asteroid in an enclosed bag, subsequently capturing and focusing sunlight which will heat up the asteroid enough to break it and release volatiles like water. In their field test, shown in the video below, this concept is proven to be very effective in breaking the rock, although relatively limited water is produced. The piece of rock on which the test runs is also very limited (compared to a typical asteroid), plus it is not clear how effective the condensation of the water is (much may still be in a gaseous phase).

Although the video looks promising their are several hurdles to be overcome when applied to space. First, identifying asteroids small enough to capture with a (inflatable) bag is very challenging. These small bodies are often only identified as NEO’s once they approach close to earth, after which it leaves a very short launch window to reach the asteroid (this was also one of the objective for Option A of NASA’s ARM Mission). Furthermore, it may be very difficult to get reliable information on the asteroids composition. Getting more space telescopes to help identify multiple targets for planned launch windows could mitigate this problem.

When a suitable asteroid is reached it’s spin may form the next problem. Small asteroids often spin relatively fast, causing problems for safe capture. Potentially the on-board solar beam system may be targeted towards the asteroid to reduce the asteroids rotation. Alternatively careful maneuvering of the spacecraft would be required to mimic the spin before capture. A Subsequent tightening of the bag and thrusting may then reduce the rotation.

It may however be preferable to maintain (or even increase) the rotation to to achieve a small outward ‘gravitational’ pull. This would allow removal of the broken asteroid fragments away from the solar beam. Subsequently this material could be captured from the outer limits of the bag for further processing. Also the volatiles would be expelled towards the sides of the bag or container, where they would condensate. Further spin could drive the water to a collecting point in the bag.

What Trans Astra is showing here is a strong proof of concept. With further field test and engineering for space this may be a very viable method for space mining. It’s certainly an interesting company to follow.