What's the issue?

A common misunderstanding when considering space travel is to assume that there is a direct correlation between distance travelled and energy expended. Using this view, the difference between reaching Low Earth Orbit (LEO) ~400 km above the Earths’ surface and reaching the 1st Earth-Moon Lagrange point (EML1) point is massive, LEO is only 1.4% of the distance to EML1, however it accounts for 86% of the total energy required to reach EML1.

We'll avoid a detailed explanation of orbital mechanics here; the key point of interest is that by the time a payload is in LEO, the majority (~83%) of the required energy for its transportation to the lunar surface has already been expended. 

Since this expended energy is directly correlated with the mass of the payload, any means that reduces this payload mass or up-mass, is extremely important when it comes to considering the viability and cost effectiveness of a space mission.

Despite the high cost of transport to space, previous space missions have been designed to contain within their launch vehicle every required resource and piece of equipment for the entire mission, this includes: propellant, life support consumables, fuel cell reagents, tools, robotic components, etc. In 1985 Cutler and Krag wrote:

“If we continue to transport all needed materials from Earth, space activities in the 21st century will be as they are now - limited and expensive” 

As of 2019 they have proven to be correct. So what's the solution?

With launch costs being one of the predominant economic considerations in the viability of space missions, the reduction of launch vehicle mass and payload, often referred to as up-mass, is critical. One of the primary potential ways to reduce the required up-mass of a mission is to collect and/or generate the resources required for mission success from local assets. This use of in-situ resources is termed in-situ resource utilization or ISRU.

The utilisation of space resources for space missions can refer to a wide variety of things. Extracting oxygen from the lunar dirt has seen a lot of attention in past decades, as has creating strutures using lunar dirt as a construciton material via 3D printing or creating concrete or geopolymers. More recently water ice was confirmed to be present in some polar regions, so the extraciton of that has also seen a lot of interest. But by far the most technically challenging and yet game changing technology would be the extraction of metals from space native resources. The pursuit of which we call Astrometallurgy.

Extractive metallurgy on Earth refers to the processes used to turn an ore into a usable metal product. In space, the goal is the same. Astrometallurgical processes take planetary materials and turn them into useful resources. The challenge of course is that the conditions and environment in space make this a much more challenging prospect than the terrestrial counterpart.

We're still many years away from a full technical demonstration of astrometallurgy on the Moon, however the plans are already being made to that end. The end goal of research in this field is the efficient and cost effective extraction of metals from planetary sources for use in space. The processes we use to do so will be at the same time both very similar and yet wildly different to the way we do it on earth.

Many considerations go into the design and development of metal extraction purposes for use in space. How do you operate in low or no gravity? How does the vacuum in space affect the process? How can we make the processes more energy efficient? Can we make them fully autonomous or at least remotely operated? How do we design them so that maintenance is easy? How do we make sure we also extract the oxygen and not just the metal? etc.

Astrometallurgy is an exciting field within the broader ISRU chain. And while we don't have the solutions yet, we're well on our way to realising them.

So...

Watch this space.