XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 337
Direct Water Extraction
Directly extracting a resource from an ore body is not a
new concept for terrestrial mining.23 A number of research-
ers have proposed direct extraction of water from a PSR
by relying on the properties of water at different pressures
and temperatures as previously discussed. The essence of
all these proposals is to raise the temperature of the icy
regolith to the point where the solid water (ice) sublimes
into a vapor state. The vapor is then captured by a pres-
sure retaining structure and then compressed or cooled and
loaded into liquid or solid water transportation vehicles. In
the concept illustrated in Figure 12, heat is transmitted to
the ore deposit by focused sunlight reflected from the rim
of the PSR crater.24
PROCESSING WATER BEARING ORE:
In the likely case where water is not directly extracted from
a lunar ice deposit, the excavated water bearing ore must be
processed to produce water. The water may then be used
for industrial purposes or human consumption, or fur-
ther processed by electrolysis into its component elements,
hydrogen and oxygen. Two fundamental methods for water
extraction have been investigated.
Controlling the temperature and pressure of icy rego-
lith to extract water has been discussed. Essentially tem-
perature and/or pressure of a quantity of water bearing ore
being processed is manipulated so that the physical state of
the water changes from a solid to a gas. The gaseous water is
then again worked on by controlled changes to temperature
and/or pressure to produce purified water either as a liquid
or solid.
As with most methods of ore processing the grain size
distribution of the material will affect the efficiency of the
process. Having a relatively small uniform grain size is desir-
able for liberating water from the regolith. However, this
will require crushing, grinding and sorting equipment and
the associated energy utilization. Figure 13 shows a NASA
experimental water extraction device using a “heated”
sloped auger with a fine-grained feed stock. This device is
similar to a terrestrial soil dryer.25
A water extraction process that is focused on minimal
energy utilization has recently been developed under NASA
Innovative Advance Concepts (NIAC) Grant.26 The pro-
cess and equipment are called Aqua Factorem and consid-
ers the ice included in the water bearing ore to be the same
as any solid mineral. A flow sheet for the extraction pro-
cess is shown in Figure 14. A series of electro-mechanical
extraction methods are applied to the icy regolith within
the PSR to break down the ore and sort out the grains solid
water. Processes include grinding, magnetic separation,
electrostatic separation, use of cyclone for gravity separa-
tion, etc.
The efficiency of water extraction from icy regolith is
dependent on multiple factors including, water content
of the ore, the need for crushing, grinding and sorting,
transportation and storage of ore and extracted water, and
availability of energy needed by the extraction process. The
most appropriate method will depend on all of these vari-
ables and more. The icy regolith deposit for each PSR will
probably be unique and require a bespoke water extraction
process.
MINE DEVELOPMENT:
Some fundamental information on icy lunar regolith and
the challenges associated with excavation and processing of
ice bearing ore has been presented. Although many gaps
in technology need to be closed before commercial mining
of PSR for water ice can take place, there are many non-
technical issues that need to be addressed.27 Establishing
an industrial facility on an extraterrestrial body will be
Figure 13. NASA water extraction device
Figure 12. Direct extraction of water within a PSR