352 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
from downstream processes and upstream physical charac-
terisation. Beneficiation, both size classification and min-
eral enrichment, is a critical part of any application that
uses highly variable naturally-occurring mineral ores as a
feedstock, on Earth and in space. For example, in an ESA-
supported study, molten salt electrolysis was shown to have
extracted up to 96% of the oxygen contained in lunar rego-
lith simulant (Lomax et al., 2020) however, simulant was
screened at 53 µm and 1 mm to remove fine and coarse par-
ticles. In a study on the use of lunar regolith as casting mold
material (Baasch et al., 2021), it was noted that using regolith
particles in the size range 25–45 µm resulted better repeat-
ability and quality. There are many similar examples of appli-
cations of lunar regolith (or simulant) in which the size range
is controlled or restricted to enhance performance there
are currently no beneficiation technologies that can meet
directly the needs of these processes (Rasera et al., 2020), nor
that have been integrated directly into an upstream excava-
tion system or downstream extraction process.
Possible needs for size classification on the Moon are
given in Table 1, based on the available literature and cur-
rent knowledge. There is a lack of detail given by research
teams focusing on different uses of lunar regolith on their
“ideal” feedstock this is partly due to the low TRL of much
of the technology development and partly due to the use of
regolith simulants—terrestrial analogue materials designed
to match lunar regolith properties such as mineralogical
composition and particle size distribution. It should be
recalled that there is a limited amount of lunar regolith
that has been characterised on Earth from limited landing
locations.
Mineral Processing from Earth to Space
One of the challenges of translating mineral processing
to space is the lack of clear targets for the separations. On
Earth, the requirements of a typical mineral processing
circuit, for example for a copper ore, are set by the smelter
contract and by the feedstock grade and mineralogy. A tar-
get of 30% Cu in the final concentrate at a recovery of 85%
provides boundary conditions to the development of the
flowsheet.
For the ISRU case, there are no current targets, and
knowledge of the resource is limited. The main drivers
when considering technology for space are mass and power
requirements. Reliability in the space environment is also
important (e.g., temperature extremes, vacuum, radiation).
For equipment operating on the Moon, the lunar dust also
is a consideration.
Typical flowsheets for terrestrial physical separation
processes are given in Figure 2. The two flowsheets differ
depending on the ore type and the number of products,
with the flowsheet on the left showing a process with one
product and one waste stream, and that on the right show-
ing multiple products. The approach, number of stages,
and circulating loads is dependent on the feedstock and the
target grades of the product(s). For the space resources case,
the knowledge of the feedstock is limited, and the target
production quality is not specified. This gives rise to sim-
pler flowsheets (e.g., single pass). The trade-off is, however,
not related to grade and recovery, but instead is related to
complexity of the process and downstream impact.
While flowsheets for lunar resource processing are
likely to look significantly different to those of terrestrial
processing, the technology used to separate the regolith
will be different. Separations must be carried out under dry
conditions, with low gravity and under vacuum. The rego-
lith is abrasive and fine therefore, moving parts should be
minimized. Trade-offs between separation performance and
reliability and complexity must be carried out. For size clas-
sification, barrier methods cannot be included for separa-
tion of components such as ilmenite, moving parts should
be minimized. The decisions to be made on the process and
Table 1. Some lunar regolith additive manufacturing studies which used as-received lunar simulants, or limited the particle
sizes without explaining the reason.
Purpose
Lunar
regolith simulant
Particle Size
Preprocessing
Final Particle Size
Range Reference
Microwave sintering JSC-1A None Up to 1 mm Lim et al. (2021)
Lithography-based ceramic
manufacturing
EAC-1A Ground for 24
hours
0.02–0.20 mm Altun et al. (2021)
Sintering LMS-1 MGS-1 None Not specified Warren et al. (2022)
Laser melting EAC-1A None Not specified Ginés-Palomares et
al. (2023)
Wetting and melting
behaviour investigation
JSC-2 Not specified 50 µm Fateri et al. (2019)
Laser powder bed fusion HIT-L-1 Sieving 154 µm Wang et al. (2023)
from downstream processes and upstream physical charac-
terisation. Beneficiation, both size classification and min-
eral enrichment, is a critical part of any application that
uses highly variable naturally-occurring mineral ores as a
feedstock, on Earth and in space. For example, in an ESA-
supported study, molten salt electrolysis was shown to have
extracted up to 96% of the oxygen contained in lunar rego-
lith simulant (Lomax et al., 2020) however, simulant was
screened at 53 µm and 1 mm to remove fine and coarse par-
ticles. In a study on the use of lunar regolith as casting mold
material (Baasch et al., 2021), it was noted that using regolith
particles in the size range 25–45 µm resulted better repeat-
ability and quality. There are many similar examples of appli-
cations of lunar regolith (or simulant) in which the size range
is controlled or restricted to enhance performance there
are currently no beneficiation technologies that can meet
directly the needs of these processes (Rasera et al., 2020), nor
that have been integrated directly into an upstream excava-
tion system or downstream extraction process.
Possible needs for size classification on the Moon are
given in Table 1, based on the available literature and cur-
rent knowledge. There is a lack of detail given by research
teams focusing on different uses of lunar regolith on their
“ideal” feedstock this is partly due to the low TRL of much
of the technology development and partly due to the use of
regolith simulants—terrestrial analogue materials designed
to match lunar regolith properties such as mineralogical
composition and particle size distribution. It should be
recalled that there is a limited amount of lunar regolith
that has been characterised on Earth from limited landing
locations.
Mineral Processing from Earth to Space
One of the challenges of translating mineral processing
to space is the lack of clear targets for the separations. On
Earth, the requirements of a typical mineral processing
circuit, for example for a copper ore, are set by the smelter
contract and by the feedstock grade and mineralogy. A tar-
get of 30% Cu in the final concentrate at a recovery of 85%
provides boundary conditions to the development of the
flowsheet.
For the ISRU case, there are no current targets, and
knowledge of the resource is limited. The main drivers
when considering technology for space are mass and power
requirements. Reliability in the space environment is also
important (e.g., temperature extremes, vacuum, radiation).
For equipment operating on the Moon, the lunar dust also
is a consideration.
Typical flowsheets for terrestrial physical separation
processes are given in Figure 2. The two flowsheets differ
depending on the ore type and the number of products,
with the flowsheet on the left showing a process with one
product and one waste stream, and that on the right show-
ing multiple products. The approach, number of stages,
and circulating loads is dependent on the feedstock and the
target grades of the product(s). For the space resources case,
the knowledge of the feedstock is limited, and the target
production quality is not specified. This gives rise to sim-
pler flowsheets (e.g., single pass). The trade-off is, however,
not related to grade and recovery, but instead is related to
complexity of the process and downstream impact.
While flowsheets for lunar resource processing are
likely to look significantly different to those of terrestrial
processing, the technology used to separate the regolith
will be different. Separations must be carried out under dry
conditions, with low gravity and under vacuum. The rego-
lith is abrasive and fine therefore, moving parts should be
minimized. Trade-offs between separation performance and
reliability and complexity must be carried out. For size clas-
sification, barrier methods cannot be included for separa-
tion of components such as ilmenite, moving parts should
be minimized. The decisions to be made on the process and
Table 1. Some lunar regolith additive manufacturing studies which used as-received lunar simulants, or limited the particle
sizes without explaining the reason.
Purpose
Lunar
regolith simulant
Particle Size
Preprocessing
Final Particle Size
Range Reference
Microwave sintering JSC-1A None Up to 1 mm Lim et al. (2021)
Lithography-based ceramic
manufacturing
EAC-1A Ground for 24
hours
0.02–0.20 mm Altun et al. (2021)
Sintering LMS-1 MGS-1 None Not specified Warren et al. (2022)
Laser melting EAC-1A None Not specified Ginés-Palomares et
al. (2023)
Wetting and melting
behaviour investigation
JSC-2 Not specified 50 µm Fateri et al. (2019)
Laser powder bed fusion HIT-L-1 Sieving 154 µm Wang et al. (2023)