Ryan L. Kobrick and David M. Klaus

University of Colorado at Boulder, Boulder, Colorado

Kenneth W. Street, Jr.

Glenn Research Center, Cleveland, Ohio

Defi ning an Abrasion Index for Lunar Surface 

Systems as a Function of Dust Interaction 

Modes and Variable Concentration Zones

NASA/TM—2010-216792

October 2010
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Ryan L. Kobrick and David M. Klaus

University of Colorado at Boulder, Boulder, Colorado

Kenneth W. Street, Jr.

Glenn Research Center, Cleveland, Ohio

Defi ning an Abrasion Index for Lunar Surface 

Systems as a Function of Dust Interaction 

Modes and Variable Concentration Zones

NASA/TM—2010-216792

October 2010

National Aeronautics and

Space Administration

Glenn Research Center

Cleveland, Ohio 44135

Prepared for the

Lunar Dust, Plasma and Atmosphere: The Next Steps

sponsored by the University of Colorado

Boulder, Colorado, January 27–29, 2010
Acknowledgments

This research was supported by a NASA Graduate Student Researchers Program (GSRP) grant (NNX07AR55H) provided by the 

Dust Management Project, under the Exploration Technology Development Program. Test equipment and support were provided 

by the NASA Glenn Research Center. Additional support was provided by BioServe Space Technologies at the University of 

Colorado at Boulder (UCB) and the Achievement Rewards for College Scientists (ARCS) Foundation, Inc. The concepts within 

the paper were presented at the fi rst workshop on “Lunar dust, plasma and atmosphere: The next steps” held January 27–29, 2010 

at the Laboratory for Atmospheric and Space Physics, UCB. Anorthosite was provided by NASA GRC from the USGS. Prof. Joe 

Smyth (UCB) provided the ruby spinel and olivine samples.

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either expressed or implied, by the National Aeronautics and 

Space Administration.

Level of Review: This material has been technically reviewed by technical management. 

This report is a formal draft or working 

paper, intended to solicit comments and 

ideas from a technical peer group.
NASA/TM—2010-216792 1 

Defining an Abrasion Index for Lunar Surface Systems as a 

Function of Dust Interaction Modes and Variable 

Concentration Zones 

Ryan L. Kobrick and David M. Klaus 

University of Colorado at Boulder 

Boulder, Colorado 80309 

Kenneth W. Street, Jr. 

National Aeronautics and Space Administration 

Glenn Research Center 

Cleveland, Ohio 44135 

Abstract 

Unexpected issues were encountered during the Apollo era of lunar exploration due to detrimental 

abrasion of materials upon exposure to the fine-grained, irregular shaped dust on the surface of the Moon. 

For critical design features involving contact with the lunar surface and for astronaut safety concerns, 

operational concepts and dust tolerance must be considered in the early phases of mission planning. To 

systematically define material selection criteria, dust interaction can be characterized by two-body or 

three-body abrasion testing, and sub-categorically by physical interactions of compression, rolling, sliding 

and bending representing specific applications within the system. Two-body abrasion occurs when a 

single particle or asperity slides across a given surface removing or displacing material. Three-body 

abrasion occurs when multiple particles interact with a solid surface, or in between two surfaces, allowing 

the abrasives to freely rotate and interact with the material(s), leading to removal or displacement of mass. 

Different modes of interaction are described in this paper along with corresponding types of tests that can 

be utilized to evaluate each configuration. In addition to differential modes of abrasion, variable 

concentrations of dust in different zones can also be considered for a given system design and operational 

protocol. These zones include: (1) outside the habitat where extensive dust exposure occurs, (2) in a 

transitional zone such as an airlock or suitport, and (3) inside the habitat or spacesuit with a low particle 

count. These zones can be used to help define dust interaction frequencies, and corresponding risks to the 

systems and/or crew can be addressed by appropriate mitigation strategies. An abrasion index is 

introduced that includes the level of risk, R, the hardness of the mineralogy, H, the severity of the 

abrasion mode, S, and the frequency of particle interactions, F. 

Introduction 

Unexpected issues were encountered during the Apollo era of lunar exploration due to detrimental 

abrasion of materials upon exposure to the fine-grained, irregular shaped dust on the surface of the Moon, 

as catalogued by Gaier at the National Aeronautics and Space Administration (NASA) Glenn Research 

Center (GRC) (Gaier, 2007). With an aim of mitigating these problems on future exploration missions, 

the investigation of lunar abrasion issues falls under the Dust Management Project (DMP) initiative at 

NASA. One goal of the research being conducted within the DMP is to develop recommendations and 

standardized testing protocols for evaluating the impact of lunar dust abrasion on proposed surface system 

materials and operations. This paper describes the formation of lunar dust and historical abrasion issues; 

the lunar regions that define the mineralogy expected during exploration; the abrasion modes and 

interaction forces that cause wear in terms of two- and three-body abrasion severity; and the relative 
NASA/TM—2010-216792 2 

spacecraft exposure zones that determine the probability of dust interactions. These four major 

contributors to wear—hardness of the mineralogy, H, level of risk, R, the severity of the abrasion mode, 

S, and the frequency of particle interactions, F—can be synthesized into a non-dimensional abrasion 

index, introduced here, which is suggested as an aid for hardware designers and mission planners. 

Lunar Abrasion History 

Micrometeorite flux can be estimated for the surface of the Moon and is dependent on the EarthMoon alignment. The backside or far side of the Moon experiences a higher rate of impacts, which may 

result in different characteristic lunar regolith composition. A power law can approximate the average 

number of micrometeoroid impacts and size distribution. Micrometeoroid sizes range from 30 to 150 μm 

in radius with masses of 10–10 to 10–8 kg impact the Moon at speeds averaging 7 km/s (Colwell et al., 

2007). Lunar soil formation is primarily due to innumerable micrometeorite impacts forming everything 

from spheres to highly angular and irregular shape silicate glass particles (Taylor et al., 2005). 

Pulverization of the lunar materials creates small particles or causes agglutinate formation to occur which 

forms large conglomerate particles (or impact breccias). Pulverization can also completely melt the 

materials forming glass (Rickman and Street, Jr., 2008a). This process causes some mixing from region to 

region on the Moon, but in the absence of an atmosphere or any form of erosion or fluid motion, the 

particles are not sorted by size and they maintain their abrasive properties. More than a quarter of the soil 

is made up of agglutinates (fused soil), and only a small fraction are impact-generated glasses and 

breccias (Colwell et al., 2007). 

Various definitions are used by different groups to describe what size particles constitute “dust”. 

Lunar regolith occupies the upper several meters (in some cases up to 15 to 20 m) of the Moon and 

consists of unconsolidated rocks, pebbles, and dust over lunar bedrock (Colwell et al., 2007). 

Table 1 gives several definitions of lunar regolith types, and Table 2 shows the distribution of particle 

sizes in the lunar regolith. 

TABLE 1.—LUNAR REGOLITH DEFINITIONS 

Regolith 

type 

Maximum 

particle size 

Reference 

Soil <1 cm Colwell et al., 2007 

Fines <1 mm Colwell et al., 2007 

Dusta <100 mb Colwell et al., 2007 

<20 m Dust Management Project of NASA’s Exploration Technology 

Development Program (up to Aug. 2010) 

<10 m NASA’s Constellation Program (Plescia, 2008) 

<5 m Health-exposure programs (respiratory cutoff) a

Dust forms 10 to 20 percent of the bulk mass of lunar regolith (Taylor and Hill, 2005). b

Effective particle radius of 50 m. 

TABLE 2.—LUNAR REGOLITH PARTICLE SIZESa

Maximum particle size Distribution of regolith particle sizes, 

percentage of total particles 

<1.37 mm 95 

<60 m (thickness of human hair) 50 

<20 m 10 to 20 

<3.3 m 5 a

Plescia (2008) and Taylor and Hill (2005). 
NASA/TM—2010-216792 3 

The properties and composition of dust particles of less than 20 μm are not well known, as this 

portion of lunar samples was not well preserved, partially because the dust grains in that range adhered to 

the sample bags and were not removed for analysis. 

Determining an accurate material lifetime estimate for operations is critical, as it influences launch 

mass and failure modes. Specific effects of lunar dust on Extravehicular Activity Systems (EVAS) during 

the Apollo era were cataloged by Gaier (2007) who additionally pointed out that the severity of dust 

problems was consistently underestimated by ground tests. Specific concerns for astronauts on lunar 

Extravehicular Activities (EVA) included issues such as vision obscuration, false instrument readings, 

dust coating and contamination, loss of traction, clogging of mechanisms, abrasion, thermal control 

problems, seal failures, inhalation and irritation, excessive crew time being used to clean EVA suits and 

equipment, and electrical conductivity. Problems spanned the entire mission from before touchdown, 

when jet-blasted dust obscured vision leading to a landing that straddled a crater, to continuous eye 

irritation all the way back to earth. In one case, the Lunar Module landed straddling a small crater and 

was tilted 10o off normal; 11o off normal is where a ‘no lift off’ capability is determined. 

Specific to the focus of this paper, abrasion problems recorded from the Apollo missions by Gaier 

(2007) included: 

 Conrad and Bean’s suits worn though above the boot, including micrometeoroid protection layer 

and several layers of breached Kapton (DuPont) multi-layer thermal insulation; 

 Wear on outer layer of Mylar (DuPont) multi-layer insulation on boots; 

 Pressure failures; 

 Gauge dials scratched (Lunar Roving Vehicle unreadable on Apollo 16), and pitting. Schmitt’s 

visor sunshade so scratched he could not see in certain directions (Apollo 17); and 

 Apollo 17 astronaut glove covers were worn through after drilling cores on two (of three) EVA 

excursions. 

Lunar Regions 

Traditionally, the Moon has been categorized into two distinct regions: the basaltic-rich mare (plural: 

maria) and the anorthositic highlands as seen in Figure 1. The regolith is deeper in the older highlands 

than the maria. The maria contains dark basalts, while the lunar highlands have lighter-colored feldsparrich rocks (Colwell et al., 2007). Lunar topography can be further categorized into zones by 

geomorphological features such as impact craters and their respective sub features, including crater 

basins, crater rims, slopes, and central peak/rings. The significance of understanding lunar geology is that 

it is a predictor of the mineralogy to be expected during exploration in different regions, which therefore 

can be used to define localized effects that lunar dust may have on systems (Kobrick et al., 2008; Kobrick 

and Klaus, 2008). Regolith properties will also change with exploration frequency from a pristine native 

state to a perturbed surface changing the mineralogy and particle size and shape exposure. Most of the 

Apollo era samples were taken on the near side of the Moon (facing Earth) and therefore are primarily 

mare-based. The mare only covers 16 percent of the lunar surface area (Dunbar, 2007) leaving a wide gap 

in exploration knowledge of the fundamental lunar regions. 

Table 3 lists the significant lunar minerals, their reported Mohs hardness values, their approximated 

abundance, and chemical composition. Ideally as we collect data from the Moon in future missions, 

abundance and concentrating processes can be quantitatively addressed. Fundamental material properties 

indicate that a harder material will abrade a softer material. Experience has shown that the mineral 

friability and the material toughness (of the material being abraded) contribute to the wear interactions. 

The abundance of a given mineral directly relates to the frequency of interaction expected during a lunar 

mission. 
NASA/TM—2010-216792 4 

TABLE 3.—SIGNIFICANT LUNAR MINERALS 

[Rickman and Street, Jr., 2008A.] 

Mineral Mohs Percent Chemical composition 

Anorthite 6 Aa CaAl2Si2O8

Bytownite 6.0 to 6.5 Mb (Ca,Na)(Si,Al)4O8 

Labradorite 7 M (Ca,Na)(Si,Al)4O8 

Olivine 6.5 to 7.0 M (Mg,Fe)2SiO4

Fayalite 6.5 to 7.0 --- Fe2SiO4

Forsterite 6.5 to 7.0 --- Mg2SiO4

Clinoenstatite 5.0 to 6.0 M Mg2 [Si2O6] 

Pigeonite 6 M (Mg,Fe+2,Ca)2[Si2O6] 

Hedenbergite 6 M CaFe+2[Si2O6] 

Augite 5.5 to 6.0 M (Ca,Na)(Mg,Fe,Al,Ti)[(Si,Al)2O6] 

Enstatite 5.0 to 6.0 A Mg2[Si2O6] 

Spinel 7.5 to 8.0 mc MgAl2O4

Hercynite 7.5 to 8 m Fe+2Al2O4 

Ulvospinel 5.5 to 6.0 m TiFe+22O4

Chromite 5.5 m Fe+2Cr2O4

Troilite 4 td FeS 

Whitlockite 5 t Ca9(Mg,Fe+2)(PO4)6(PO3OH)

Apatite 5 t Ca5(PO4)3(OH,F,Cl) 

Ilmenite 5.5 m Fe+2TiO3

Native Iron 4.5 t Fe 

a

abundant 

b

major 

c

minor 

d

trace 

Data from the Moon Mineralogy Mapper, an imaging spectrometer on-board India’s Chandrayaan-1 

spacecraft, indicated spinel-rich deposits in the near side dark mantle. The strongest spinel signatures 

occurred as small concentrations on the scale of <1 km and were observed to be associated with small 

fresh craters and crater walls (Sunshine et al., 2010). Since spinels are the hardest minerals previously 

encountered on the Moon, deposits could be associated with a higher frequency of abrasive wear and 

higher exploration risk for material lifetime. 
NASA/TM—2010-216792 5 

When the abrasive hardness is similar to or larger than the substrate, the interactions approach 

polishing, and wear resistance improves by an order-of-magnitude. When the abrasive exceeds the 

substrate hardness, polishing will continue. Hardness is the resistance to localized plastic deformation 

(typically in the form of an indentation scratch). The traditional and earliest quantifiable method of 

measuring hardness is by a scratch test, which compares the ability of the substance to scratch or be 

scratched by a series of standard minerals, the Mohs Scale. With several standard test methods available, 

lunar dust hardness can be approximated (see Fig. 2 for scale comparison including commonly used or 

proposed space construction materials). In passing, it should be noted that hardness ranges occur for 

minerals due to compositional variation (e.g., Diamond), crystal orientation (e.g., Apatite) and 

environmental humidity. Hardness values may be significant for multiple investigations, specifically 

abrasion wear, as they can indicate how a material may react in a given environment. 

Another observation made during this research was that two minerals with similar hardness values, 

but different toughness values (ability to absorb mechanical or kinetic energy up to failure), produced 

significantly different wear levels. Toughness is the resistance of a material to fracture when stressed and 

can be quantified by the area under a stress-strain curve. Brittle materials include ceramics and minerals, 

whereas tough or ductile materials include metals and alloys like carbon steel. Materials like silica have a 

high hardness value but are brittle, resulting in less abrasivity than minerals with high hardness and 

toughness (Rickman and Street, 2008b). On the other hand, ceramic construction materials and coated 

materials also tend to be brittle resulting in failures that do not occur in metals. Further, manufacturing 

processes can lead to different surface hardening and surface finishes for metals. Work hardening also 

occurs for some metals altering the surface hardness, which also affects the toughness making it difficult 

to have a direct correlation between hardness and abrasive wear. 
NASA/TM—2010-216792 6 

Density of regolith is also important for exploration activities in the different lunar regions. 

Relative density increases with regolith depth, suggesting that the regolith becomes more compacted 

(Colwell et al., 2007). Because of the properties of density, void ratio, cohesion, and friction angles, 

crater rims are expected to be less dense (less than 50 percent) than their surrounding lunar terrain 

(Colwell et al., 2007). This is important for exploration activity operations as it may result in more 

dust leaving the surface as well as greater penetration into the soil. The density from actual missions 

was found to be higher than predicted, and the increase with depth was suggested to be primarily due to 

self-weight. Density estimations and calculations suggest that the soil on slopes is considerably weaker 

(Mitchell et al., 1972) or less dense due to the observed lower mechanical soil (or regolith) stability. 

Recent conference discussions regarding the results from NASA’s Lunar Crater Observation and 

Sensing Satellite (LCROSS) have indicated that the crater slope regolith where the LCROSS impacted 

had a lower density than expected. The term ‘fluffy regolith’ has been used to describe the density 

phenomenon. Density mapping analysis and mission architecture planning will need to consider that lunar 

regolith layering is not fully understood and may not be predictable with current data (Colaprete et al., 2010). 

Abrasion Modes 

The lunar science community identified the abrasive nature of lunar dust as one of the top five 

physical properties of interest. Abrasion’s importance was ranked as ‘high’ because it affects any material 

that moves or has a sealing surface. In the field of Tribology, abrasion is one of the four basic types of 

wear or physical mechanisms for material removal or displacement (see Fig. 3) (ASTM, 1997) and is the 

most severe and most costly form of wear (Budinski and Ives, 2005). Wear resistance is not a basic 

material property, but a system response of the material as a function of its use (ASTM, 1997). Abrasive 

wear occurs when a hard protuberance (asperity) on the surface of a material, or a hard, loose particle 

trapped between surfaces, plastically deforms, gouges or cuts the counter surface as a result of motion. 

The result is a series of grooves in soft material or surface fractures in brittle material. Additionally, with 

hard material this is often accompanied by the resulting formation of wear particles. Abrasion can be subcategorized by degree of freedom into two tribosystems; two-body and three-body wear. Two-Body 

abrasive wear occurs when hard particles or protuberances, which produce the wear of one body, are fixed 

on the surface of the opposing body (ASTM, 2005). A simplified example would be sandpaper against a 

surface. Three-Body abrasive wear occurs when loose particles are introduced or generated between the 

contacting surfaces (ASTM, 2005). For example, this occurs when sand is continually poured between two 

plates rubbing against each other. Two-body fixed abrasives are typically used for testing plastics, metals, 

ceramics, and composites, while three-body testing is used for all materials (Budinski and Ives, 2005). 

Degree of freedom influences the abrasiveness of a test, and generically two-body abrasion will 

produce significantly higher wear than three-body, because three-body particles have the ability to roll 

(two-body abrasive particles are fixed in orientation during wear). This may make two-body 
NASA/TM—2010-216792 7 

measurement easier to obtain since the wear would be more sizeable. The wear on a material is fairly 

constant when the abrasive is much harder than the material. For this reason, the material property of 

hardness can be used as an estimate of how much abrasion is expected between a pair of materials as 

previously stated. Each industry has developed custom tests that are specific to their environment and 

interaction type of wear. Some of these tests have become standards with ASTM International and 

relevant examples are listed in Table 4. 

Determining the appropriate test for various abrasive scenarios is an ongoing process. For space 

surface applications, additional methods are being developed to examine the fundamental modes of wear. 

The known spacesuit/spacecraft lunar dust contamination points combined with the Apollo era issues help 

define the modes of wear that need to be investigated. The two main modes of dust interactions occur 

when spacecraft, spacesuit, or robotic materials either come into direct contact with lunar dust (a twobody problem), or when dust is trapped between two surfaces in relative motion (a three-body problem). 

In the examples presented in Figures 4 and 5, it should be noted that wear could be occurring on all 

materials involved. Under categorization of wear, sliding and rolling are considered non-abrasive wear 

(Budinski, 2007), but for the purposes of defining interactions, rolling also coincides with rotation. 

TABLE 4.—SUMMARY OF RELEVANT ASTM STANDARDS 

FOR ABRASION TESTING 

Test name (abbreviated) ASTM standard Degree 

Loop abrasion test G 174 (replace G 65) Two-body 

Drum abrasion test G 132 Two-body 

Scratch test G 171 Two-body 

Plastic abrasion test (withdrawn) D 1242 Two-body 

Taber abraser D 4060 Two-body 

Abrasion by particle movement Nonstandard Tests Two-body 

Printer ribbon test G 56 Two-body 

Yarn test D 3108 Two-body 

Magnetic tape abrasivity test ----------- Two-body 

Rock abrasiveness by CERCHAR Method D 7625 Two-body 

Gouging abrasion with jaw crusher G 81 Three-body 

Dry-sand, rubber, wheel abrasion G 65 Three-body 

Wet-sand abrasion G 105 Three-body 

Taber with ancillary grit feeder F 510 Three-body 

Disk versus disk ----------- Three-body 

High abrasion test ----------- Three-body 

Wet high-stress abrasion test B 611 Three-body 

Chemo-mechanical planarizing ----------- Three-body 

Ball cratering test VAMAS Three-body 

Gas jet erosion test G 76 Three-body 

Abrasion resistance of textile fabrics D 3884 Three-body 
NASA/TM—2010-216792 8 

Although Figure 5 addresses interactions with two similar or different space construction materials 

interacting with dust, fundamentally it can be viewed as dust interacting independently on each surface 

with the same applied force. With this reasoning it would not be necessary to test multiple materials in the 

same abrasion test, but the independent results can be extended towards applications or scenarios that 

include two or more materials interfacing with dust. 

With the different abrasion-modes, relevant tests can be developed that utilize either a two-body or 

three-body apparatus relevant to the specific interaction and loaded accordingly with the appropriate 

normal force. The type of measurements will depend primarily on the test configuration, but will also take 

into account common practices of employing mass changes, volume loss measurements, and surface 

deformation evaluation, as applicable. 

The ASTM 171 Standard for scratch testing was determined to be the best practice for investigating 

the fundamental interactions of a single particle on a given material with a two-body test. The 

methodology, along with results, is extensively explained in previous papers by the authors 

(Kobrick et al., 2008, 2009, 2010a, 2010b, 2010c; Kobrick and Klaus, 2008). Figure 6 is a photograph 

of the standard diamond tip with 200 μm radius and 120o apex angle scratching aluminum (Al) 6061–T6. 

ASTM 171 prescribes running three scratch tests, with one width measurement each. With current 

technology, a complete 3–D profile of the surface can be generated and mathematically analyzed. The 

authors’ proposed new method generates three surface profiles per scratch that includes approximately 

480 cross sections each, totaling 4,320 cross sections per tip to specimen combination. 

A key finding during the investigation was that the ASTM G 171 Standard utilized scratch width the 

key measured variable, but this methodology neglected the volumetric differences within the scratch and 

surrounding area. The authors’ main suggested improvement to the current standard was to include an 

entire ‘Zone of Interaction’ (ZOI) to more fully characterize the abraded material. Figure 7 shows a cross 

section or a representative scratch indicating the ZOI boundary conditions, which were suggested to be 

three times the surface roughness (Ra). 

The standard scratch test normally uses a diamond stylus with an applied constant normal load as it 

translates over the specimen surface. Since lunar exploration activities will encounter a variety of 

mineralogy, but not including diamonds, custom tips were also investigated. Figure 8 shows a ruby spinel 

(MgOAl2O3, CU–Boulder #2348, from Kandy, Ceylon, Dana No. 7211) tip mounted in a custom holder 

for testing, chosen for its high hardness value. Other minerals tested included anorthosite (from U.S. 

Geological Survey, USGS, base materials of the NU–LHT highland simulant, source Stillwater 
NASA/TM—2010-216792 9 
NASA/TM—2010-216792 10 

TABLE 5.—THREE-BODY ABRASION TEST SUMMARY 

[Kobrick et al., 2010c] 

 Number of abrasive tests 

Material JSC–1AF JSC–1AF <25um Alumina Silica NU–LHT–2M 

6061 Aluminum 3 3 4 4 3 

1018 Steel 3 3 4 4 3 

1045 Steel 3 3 4 4 3 

PMMA 3 3 4 4 3 

Mine, MT), enstatite (from NASA GRC, source Mogok, Sagaing District, Mandalay Division, Burma–

Myanmar) and olivine (from CU–Boulder lab, source AZ) because of their higher abundance on the 

Moon and higher Mohs hardness values. Due to the friability of these minerals, they shattered under low 

normal loads creating secondary and tertiary scratches. These interactions were also indications that a 

simple scratch width did not suffice for describing abrasion interactions. Custom tips also add the 

complication of having different geometries and crystal orientations, so comparing results is currently 

only qualitative. 

A secondary study was conducted to investigate three-body abrasion with a modified tribotester and 

dry abrasives, based on ASTM Standard B 611 (Kobrick et al., 2010c). Standard abrasives of alumina and 

silica were compared to lunar simulants of JSC–1AF (mare region simulant) and NU–LHT–2M (highland 

region simulant) and are summarized in Table 5. The tests showed that each material tested (aluminum 

6061, steel 1010, 1018, and 1045, and PMMA) reacted similarly to the silica abrasive for softer materials 

and that the alumina abrasive showed more wear on all materials than the counterparts (Kobrick et al., 

2010c). Since alumina was demonstrated to be more abrasive than the simulants, systems could be tested 

using this common abrasive instead of a lunar simulant to yield a higher safety factor, but at the potential 

cost of unnecessarily overdesigning the system. Ongoing testing is investigating this approach with 

varying sizes of alumina particle sizes on the same material set. 

Spacecraft Dust Concentration Zones 

In addition to the specific mode of dust interaction, the spacecraft and surrounding environment can 

be subdivided into three fundamental dust concentration zones as depicted in Figure 9 ranging from 

(1) outside the habitat where extensive dust exposure occurs, (2) in a transitional area such as an airlock 

or suitport, and (3) inside the habitat or spacesuit with a low particle count. These zones can also be 

mapped to robotic systems as well, where the transitional zone boundaries could be at mechanical 

interfaces and the internal zones would be the circuit boards. These lunar zones can be used to help define 

dust interaction frequencies, characterize environmental risks to the systems and/or crew, influence 

material selection (based on location of part and exposure), or affect the operational protocols used during 

the mission architecture.

Defining the entry probability that a grain of dust will come in contact with an astronaut on an EVA 

and then comparing that data to actual field tests can be used as a means of validating a measure of 

effectiveness for various dust mitigation technologies and strategies. For example, the probability of dust 

grain entering the lander post EVA can be defined as Equation (1) (Hyatt et al., 2007). 

P = Pa (1 – PL

Ext) T PLInt (1) 

where Pa is the probability of a grain in the near-vicinity of an astronaut adhering to a spacesuit, PL

Ext is 

the loss probability of a dust grain external to the habitat in regular EVA activity or mitigation process, 

PL

Int is the probability of grain release from the suit internal to the habitat. The variable T is defined as the 

transmission coefficient of the internally released dust grain from the airlock to the habitable volume of 

the habitat (i.e., no airlock T = 1) (Hyatt et al., 2007). 
NASA/TM—2010-216792 11 

Probability approximations can be used in trade studies for selection of critical exploration systems 

such as solar panels, mechanical interfaces, and lunar lander airlock concepts. Other trade studies could 

include dust characteristics, material performance, material properties (such as flexibility), power 

requirements and mass allocation. 

The following list summarizes potential technologies/solutions that could help address dust contact 

prevention and/or removal (Belden et al., 1991; Calle et al., 2006; Harrington et al., 1990; Taylor et al., 

2005; Taylor and Hill, 2005; Walton, 2007). Some of these techniques were employed during the Apollo 

era, such as brushing, with mixed success. The purpose of this list is to demonstrate various dust 

mitigation options that have previously been investigated or proposed. The primary shortcoming with 

most of these approaches is that they jump directly to a solution without properly characterizing the 

interaction between the dust and the system that caused the problem in the first place. Some of the 

demonstrations have only been conducted with simulants while others that have used real lunar samples, 

which represent only specific lunar locations (e.g., most are mare samples) and not the bulk composition 

of the Moon. It should be pointed out that none of these studies have used dust in the same state of 

surface activation that will be experienced under actual lunar conditions. Selection of future landing sites 

will dictate the average particle size distribution and mineral composition that need to be investigated. 

1. Brushing—bristle, suction Styrofoam (Dow Chemical Company), cheese cloth 

2. Electrostatic—curtain, surface, passive suction, passive brush 

3. Jet —with shield, with surface 

4. Spinning—shield, surface 

5. Dust monitoring 

6. Chemical—suction 

7. Vibrating—surface, suction, blower 

8. Materials—Chromel-R woven into boots/gloves, abrasion-resistant silicone RTV–630 

soles/finger tips. 

9. Avoidance of PVC products 
NASA/TM—2010-216792 12 

10. Teflon (DuPont) over Gore fabric twill or composite Ortho fabric 

11. Cleaning—Nylon bristle brush (coarse grains), wet wipes, and zippers and seals cleaned and 

re-lubricated with Krytox (Miller-Stephenson Chemical Company, Inc.) oil and grease. 

12. Fluid—foams, gels, liquid and gas solutions 

13. Helmet visor “peel-offs” 

14. Lightweight coveralls 

15. Magnetic manipulation 

16. CO2 “snow” cleaning 

Abrasion Index Development 

For designing space exploration systems that will encounter dusty regolith, various known input 

parameters described above can be characterized and mathematically combined to create a nondimensional abrasion index (illustrated by the basic flow chart displayed in Fig. 10). The creation of an 

abrasion index can be used to improve the performance and reliability of exploration systems in the areas 

of: abrasive risk identification; specific mitigation strategies; mission design, such as landing location or 

field operations; hardware design; testing protocols in the laboratory; and material selection for surface 

systems. 

The next steps in defining a non-dimensional abrasion index would be to quantify the input variables 

as identified with appropriate scales and then assign weighted criteria to normalize each category so that 

they can be combined into a final, unitless value. The following discussion includes suggestions for input 

variables under each category covered in this paper for abrasion on materials, parts, or full systems. An 

abrasion index showing key variables is functionally described in Equation (2): 

 Abrasion Index = f (R, H, S, F) (2) 

where 

Abrasion index non-dimensional value quantifying the overall abrasion level 

R material, part or system risk to mission success 

H weighted average hardness value of localized mineralogy 

S severity of abrasion in terms of two- or three-body 

F the frequency of dust particle interactions 
NASA/TM—2010-216792 13 

The lessons learned from lunar abrasion and spaceflight history are that systems will each have 

unique component-level risks associated with functionality and operations. For example, a spacesuit glove 

seal would be considered to be a higher risk part than the portable life support system (PLSS) outer fabric 

layer. An abraded seal can lead to a pressure leak presenting direct astronaut safety concerns, but abrasion 

to the PLSS fabric may only reduce the amount of padding or potentially change the radiative properties 

of the material if dust becomes embedded. For an abrasion index, risk to mission success, R, is an 

important variable that must be systematically characterized. A high value would mean that the item is 

critical to the mission based on historical experience, ongoing data collection or testing. In our example, 

the glove seal would have a higher value than the PLSS cover. Other potential variables relating to lunar 

abrasion history could be measured by proximity to the outermost exposed surface or number of cycles 

expected. Material selection also relates to the system risk, as a soft aluminum with a low hardness value 

is prone to abrasion. 

Lunar regions determine the specific mineralogy that will be encountered by a surface system. The 

Moon-Sun-Earth alignment influences the degree of micrometeorite bombardment and radiation flux, 

which can be estimated with current data. The stability of the terrain (crater rims, slopes, and other 

geological features) will also influence the minerals expected to be displaced by exploration and 

interacted with each system. The key abrasive variable from lunar regions is the mineralogy hardness 

value, H, which can be measured using various hardness scales. The H-value expected in the location of 

exploration would be determined by a weighted average of hardness values and particle distribution (size 

and quantity). A high value means that the expected terrain encountered would have more abrasive 

particles. An example of a high H-value region is the spinel deposit regions mentioned previously in the 

paper. 

Modes of two- and three-body abrasion determine the severity, S, of expected particle interactions 

with materials and systems. A high value means that the interaction is expected to cause more wear under 

anticipated normal loads. This variable could also be binary, if a relationship can be established 

comparing two- to three-body abrasion. For example, S would be a multiplier in the abrasion index of the 

ratio of two- to three-body wear for a given system. 

A final variable category is dependent on the spacecraft dust zones and relates to the frequency, F, of 

particle interactions. A higher value implies more particles are expected to interact with the system. 

Additional variables could include the probability of interaction in each type of dust zone (based on 

Hyatt et al., work for dust entering a lunar habitat) and if mitigation strategies are used to reduce the 

particle count. Mitigation strategies could also be used in reducing risk R-values. 

In summary, assuming that the suggested non-dimensional index value is established to directly 

correlate with increasing potential for material wear (i.e., a higher index indicates a greater potential 

abrasive impact to the system), the four input parameters result in the following trends. Higher R, H, and 

F values would increase the abrasion index as follows. R is determined on a system-by-system basis as a 

function of the level of risk that is associated with excess abrasive wear on the component. A larger 

R-value implies greater functional criticality that would be impacted by abrasion. H and F are dependent 

on the operational environment in terms of the minerals present and the concentration that a given system 

is exposed to. An increase in either factor presents the potential for greater abrasion to occur. S is a 

function of the specific tribology effects dependent on how surfaces come into contact with dust in terms 

of interaction mode and loading profile. The value of S increases as classical two-body abrasion is 

approached, representing a worst-case scenario for particle interaction and resultant wear. Therefore, 

defining an abrasion index in this manner gives designers a systematic method for combining operational 

environment factors with system functionality to determine the overall effect of abrasion, which can then 

be used to predict expected lifetime and performance impacts. 

Additional variables can be added as deemed useful, with further work required to determine the most 

appropriate inputs for a given application. A complete abrasion index should ultimately include weighting 

criteria and a definition of how the variables relate, i.e., are they a weighted sum, or are some variables 

multiplied or divided by each other. This work presents the concept and lays a foundation for defining an 
NASA/TM—2010-216792 14 

abrasion index, with suggested potential relationships that can be used to quantify a single, nondimensional index value. 

Conclusions 

By characterizing the concerns of lunar abrasion encountered during the Apollo era, future 

exploration systems can be designed to reduce the potential risk of failure or undesirable degraded 

performance. Planning for abrasive interactions can help to ensure that field equipment is optimized for 

the environment it will be used in, taking into account the concentration and hardness of the mineralogy 

found in the desired exploration region. Terrestrial laboratory and industrial experience can also be used 

to compile analogous data needed to quantify the level of severity expected for the different interaction 

modes of abrasion under specified normal loads. The frequency of interactions can be added to predict 

expected life cycles of the components and systems to ensure safe and efficient operations. Combining 

these variables, a non-dimensional abrasion index value can be defined that takes all the above into 

account to aid with mission and hardware design and to ensure proper testing and material selection 

occurs. The next step in defining this index is to quantify the input variables, establish the appropriate 

relationships and weighting factors, and determine a suitable, relative index scale. 

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Defining an Abrasion Index for Lunar Surface Systems as a Function of Dust Interaction 

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14. ABSTRACT

Unexpected issues were encountered during the Apollo era of lunar exploration due to detrimental abrasion of materials upon exposure to 

the fine-grained, irregular shaped dust on the surface of the Moon. For critical design features involving contact with the lunar surface and 

for astronaut safety concerns, operational concepts and dust tolerance must be considered in the early phases of mission planning. To 

systematically define material selection criteria, dust interaction can be characterized by two-body or three-body abrasion testing, and subcategorically by physical interactions of compression, rolling, sliding and bending representing specific applications within the system. 

Two-body abrasion occurs when a single particle or asperity slides across a given surface removing or displacing material. Three-body 

abrasion occurs when multiple particles interact with a solid surface, or in between two surfaces, allowing the abrasives to freely rotate and 

interact with the material(s), leading to removal or displacement of mass. Different modes of interaction are described in this paper along 

with corresponding types of tests that can be utilized to evaluate each configuration. In addition to differential modes of abrasion, variable 

concentrations of dust in different zones can also be considered for a given system design and operational protocol. These zones include: (1) 

outside the habitat where extensive dust exposure occurs, (2) in a transitional zone such as an airlock or suitport, and (3) inside the habitat or 

spacesuit with a low particle count. These zones can be used to help define dust interaction frequencies, and corresponding risks to the 

systems and/or crew can be addressed by appropriate mitigation strategies. An abrasion index is introduced that includes the level of risk, R, 

the hardness of the mineralogy, H, the severity of the abrasion mode, S, and the frequency of particle interactions, F. 

15. SUBJECT TERMS

Abrasion; Lunar exploration; Lunar dust; Surface systems 

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