Juan H. Agui and Dennis P. Stocker

Glenn Research Center, Cleveland, Ohio

NASA Lunar Dust Filtration and 

Separations Workshop Report

NASA/TM—2009-215821

December 2009
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Juan H. Agui and Dennis P. Stocker

Glenn Research Center, Cleveland, Ohio

NASA Lunar Dust Filtration and 

Separations Workshop Report

NASA/TM—2009-215821

December 2009

National Aeronautics and

Space Administration

Glenn Research Center

Cleveland, Ohio 44135
Available from

NASA Center for Aerospace Information

7115 Standard Drive

Hanover, MD 21076–1320

National Technical Information Service

5285 Port Royal Road

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Available electronically at http://gltrs.grc.nasa.gov

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

This report contains preliminary fi ndings, 

subject to revision as analysis proceeds.

Acknowledgments

This report would not have been possible without the contributions of the workshop presenters and attendees listed in the 

appendix. The workshop was held at the Ohio Aerospace Institute (OAI) and benefi ted especially from the help of 

Joyce Robertson, OAI’s Administrative Coordinator. Meeting arrangements were planned and carried out by

Juan Agui and Dennis Stocker with the help of Barbara Kakiris, Joshua Glemza, S. Lynn Mallinak,

Christine Gorecki, and Cynthia Rosenberger.
NASA/TM—2009-215821 1 

NASA Lunar Dust Filtration and Separations Workshop Report 

Juan H. Agui and Dennis P. Stocker 

National Aeronautics and Space Administration 

Glenn Research Center 

Cleveland, Ohio 44135 

Summary 

NASA Glenn Research Center hosted a 2.5-day workshop, entitled “NASA Lunar Dust Filtration and 

Separations Workshop” at the Ohio Aerospace Institute in Cleveland, Ohio, on November 18 to 20, 2008. 

The purpose of the workshop was to address the issues and challenges of particulate matter removal from 

the cabin atmospheres in the Altair lunar lander, lunar habitats, and in pressurized rovers. The presence of 

lunar regolith dust inside the pressurized volumes was a theme of particular interest. The workshop 

provided an opportunity for NASA, industry experts, and academia to identify and discuss the capabilities 

of current and developing air and gas particulate matter filtration and separations technologies as they 

may apply to NASA’s needs. A goal of the workshop was to provide recommendations for strategic 

research areas in cabin atmospheric particulate matter removal and disposal technologies that will 

advance and/or supplement the baseline approach for these future lunar surface exploration missions. 

1.0 Introduction 

NASA’s future lunar surface missions will be faced with the challenges posed by the effects of lunar 

dust. Recent NASA assessment studies of lunar dust effects suggest that contact with lunar dust will 

affect crew health as well as the stability and durability of sensitive equipment and instrumentation on 

long-duration missions. Concerns have been raised, based on experiences during the Apollo missions, 

about the health effects of the long-term human exposure to airborne lunar dust. In particular, incidences 

of respiratory and ocular irritation from the lunar dust were reported during these missions. For reference, 

the Biological Effects of Lunar Dust Workshop (Ref. 1) held in 2005 addressed in depth many of the 

health hazards of lunar dust. Recent data obtained at the NASA Glenn Research Center have shown that 

lunar dust has a significant fines fraction that may overlap with the range of particle sizes over which high 

efficiency filters are least efficient at capturing. Particles in this size range are categorized as the “most 

penetrating particle size” since they are the most likely to avoid being captured onto filter fibers by one of 

the three capturing mechanisms: Brownian diffusion, interception, and impaction. In addition to health 

effects, certain properties of lunar dust may also affect the nominal performance of equipment and 

instrumentation. In light of these effects, effective ingress infiltration barriers and removal and disposal 

technologies of lunar dust from the habitable environments will be of prime importance. 

Particulate filtration will serve as a primary approach for cleaning up the recycled air on lunar surface 

exploration missions by removing internally generated dust as well as the lunar surface dust introduced 

into the cabin. To meet the challenges of these missions, more capable filtration systems—likely 

supplemented with particle separation (from the gas phase) techniques—will need to handle both the 

longer duration missions and the load of lunar dust particles. Among the desired features of cabin 

atmospheric particulate filtration and separations technologies being sought are improved efficiency, high 

load capacity, low energy consumption, low mass and volume, and the ability to be regenerated. The 

workshop provided an opportunity to assess the compatibility of current technologies with some or all of 

these features, and to identify areas for further development. In addition, novel techniques and materials 

were discussed. 

To support this development, the Glenn Research Center is developing a testing facility to evaluate 

filter media and filtration and gas-phase separation technologies. The aim of the facility is to test for 
NASA/TM—2009-215821 2 

efficiency and practicality of filtering lunar dust under the constraints of exploration vehicle and cabin 

design. The facility will be available to test the technologies proposed by this workshop. 

A list of acronyms used in this report is given in Appendix A to aid the reader. 

2.0 NASA Programmatic Overview 

NASA’s Exploration Technology Development Program (ETDP) sponsored the NASA Lunar Dust 

Filtration and Separations Workshop. The ETDP supports the development and maturing of high-priority 

exploration technologies for NASA’s flight exploration programs addressed in several projects related to 

the characterization and mitigation of lunar dust effects for lunar surface missions. An important ETDP 

goal is to reduce the mass, volume, power requirement, crew time, and consumables required by a 

technology, thereby reducing the launch mass and resupply requirements. Additional technology 

objectives are to improve performance and meet new requirements. The general focus of the ETDP 

program is to mature the technologies required for human space exploration to a technology readiness 

level (TRL) of 5, where the technology has been tested and demonstrated in a relevant environment. 

There are two ETDP projects that have relevance to the topic of the workshop. The first is the Dust 

Mitigation and Control task under the Exploration Life Support (ELS) project which directly funds 

technology development for filtration of airborne lunar dusts and vacuum cleaning technologies. The 

other is the Dust Management project which conducts multidisciplinary research on the characterization 

of relevant lunar dust properties. 

The charter of the ELS project is to develop a suite of environmental control and life support system 

(ECLSS) technologies for use on human spacecraft for the Constellation Program. This includes the crew 

exploration vehicle (Orion), lunar lander (Altair), lunar outpost, and pressurized rovers. The objectives 

are to develop and mature life support systems technologies that fill capability gaps (enabling) and 

significantly improve the state of the art (substantially enhancing). This will lead to the development of 

efficient, safe, and reliable technologies with reduced resource requirements (mass, power, heat rejection, 

volume, crew time, and consumables). Under this project, the Dust Mitigation and Control task is 

responsible for development of the next generation air filtration systems for lunar surface systems, which 

are expected to improve in efficiency and performance while reducing the number of replacement units 

either through higher capacity or regeneration of the filter unit. This technology is expected to mature and 

be available by the vehicle’s Preliminary Design Review (PDR), with further development and refinement 

until the System Readiness Review (SRR), by 2013 and 2014, respectively. 

The ELS project will look to the broader scope Dust Management Project for help in determining 

some of the aerosol characteristics of lunar simulant dust. Comprising researchers throughout the Agency 

(with a strong Glenn component) and multiple outside collaborators, the Dust Management Project aims 

to be the “go-to” place for definitive answers on how physical properties of simulants relate to lunar 

regolith properties for verification of material and component performance of lunar equipment on the 

surface and in the habitat in order to reduce risk to mission safety, cost, and success. The project’s 

activities include high-quality and sophisticated measurements of some of the key properties of lunar 

dust. 

An indication of the importance of lunar dust issues to the Agency are the results of the last round of 

programmatic prioritization, in which the mitigation and filtration of lunar dust ranked high as a 

technology development area for lunar surface missions, which include the Altair lunar lander and outpost 

habitat. The Constellation Program Technology Prioritization Panel (TPP) identified several reasons to 

develop airborne particulate matter removal technologies as shown in Table I. 
NASA/TM—2009-215821 3 

TABLE I.—RELEVANT RESULTS OF CONSTELLATION PROGRAM TECHNOLOGY PRIORITIZATION PANEL (2008)a

ID Titleb Missionc Category 

105 Lunar Dust Filtration 

Need improved filtration methods for lunar dust. Control below SOA HEPA filtration is 

desired to protect crew per medical operations. Filtration to 0.1 m is desired. 

Lunar 

transport Critical 

594 Advanced Airlock/Suitlock with Dust Filtration 

Large number of EVAs (extravehicular activities) will require minimum gas loss suitlock 

that can depress and repress quickly and keeps suits in suitlock for dust mitigation. 

Lunar 

transport Critical 

627 Lander Dust Mitigation 

Materials and/or mechanisms that do not collect dust and do not abrade when in contact with 

lunar regolith and/or do not remove lunar regolith from surfaces. 

Lunar 

transport 

Highly 

desirable 

469 Lunar Dust Filtration 

Need improved filtration methods for lunar dust. Control below SOA HEPA filtration is 

desired to protect crew per medical operations. Filtration to 0.1 m is desired. 

Lunar 

surface Critical 

623 Dust/Regolith Mitigation Techniques within Habitable Cabin 

Approaches to prevent regolith/dust from entering the habitat from suits and instruments are 

required. A reliable system for collecting and removing regolith/dust from the habitat is also 

required. Extensive exposure to lunar dust can lead to respiratory problems. Includes dust 

characterization and establishment of human health standards. Dust-proof containers, 

filtering system, pumps are example technologies that need to be developed. Sensor/monitor 

of dust levels within the airlock and methods for dust removal (e.g., electrostatic methods, 

nitrogen air shower). 

Lunar 

surface Critical 

625 Dust Control/Remove Airborne Dust 

Technologies to remove airborne dust (down to submicron range) from cabin atmospheres 

without incurring high expendable filter resupply burdens. 

Lunar 

surface Critical 

a

Presented by Daniel Barta of NASA Johnson Space Center. 

b

SOA HEPA filtration is state-of-the-art high-efficiency particulate air filtration. 

c

Lunar transport = initial lunar missions (lunar lander); Lunar surface = extended lunar missions (outpost). 

3.0 Workshop Objectives and Management 

The objectives of the workshop were threefold. The first was to provide basic information exchange 

at the programmatic and technical level, in light of the diverse background and expertise of the 

participants. The second was to obtain an industry perspective on the problem at hand and solutions used 

in the field. The third objective was to obtain recommendations for strategic research and technology 

development. 

The management of the workshop is described here to provide a reference for any future follow-on 

workshop that may take place. The workshop was structured to produce a free exchange of ideas, problem 

solving, and team cooperation. Workshop attendees are listed in Appendix B. Because of the diverse 

audience background, the presentations were structured to provide high-level programmatic information, 

whereas the technical presentations were kept at a level appropriate for a general engineering audience. 

The splinter sessions were also organized to have a good mix of interaction between NASA researchers, 

managers, and filtration experts. 

The first day of the workshop and part of the morning of the second day was used for exchange of 

information through technical presentation. Most of the second day was devoted to splinter sessions. The 

participants were broken up into four groups and asked to probe and discuss ideas as well as provide 

recommendations on filtration and separations technologies. The third day was left for general discussions 

and for touring some of the Glenn facilities. 

4.0 Workshop Presentations 

There were 20 presentations made at the workshop (see App. C). They were subdivided into 

background information, filter testing, filtration technology, and Small Business Innovation Research 

(SBIR) presentation categories. The background information included programmatic presentations, 

presented in the previous section, which exposed the general audience to some of the priorities and 
NASA/TM—2009-215821 4 

tentative requirements for the spacecraft and habitats. Two of the presentations provided perspectives of 

lunar dust experiences during the Apollo missions. These highlighted that the missions were successful 

overall, but indications of dust contamination were quite obvious. The technology presentations provided 

a good level of detail on filters and particulate separations technologies, educating the NASA audience on 

some of the fundamentals, standards, and practices of state-of-the-art filtration. Some cutting-edge 

research and developmental technologies were highlighted in these presentations. Lastly, there were four 

SBIR presentations that showed promising prospects for exploration filtration systems. Some of the key 

information and points provided by the workshop presentations are presented here. 

4.1 Background Information 

Background information provided in the presentations included overviews of lunar dust properties, 

toxicology, hardware issues, the Apollo experience, and spacecraft airlocks and cabin air revitalization. 

The Apollo talks provided extensive perspective on the experience with lunar surface dust, and therefore a 

few lists of issues and recommendations from lessons learned are provided below. Recent NASA internal 

data and studies provided estimates of lunar dust entry into the spacecraft and standards for acceptable air 

quality that were highlighted in the presentations. 

4.1.1 Lunar Dust Properties 

Lunar regolith refers to the crushed (comminuted) lunar rock produced as a result of space weathering 

that led to the formation of a surface soil with particles that are 1 cm (no organic component is implied). 

The prime constituents are aluminosilicate and other silicate minerals that make up 90 percent by volume 

of lunar rocks. The lunar rock or soil is also comprised by up to 20 percent of various oxides that can 

potentially be tapped for oxygen extraction. The fine particle content of the lunar regolith is known as 

lunar dust and is categorized based on application: (1) Lunar dust involved in surface (external) 

operations has been defined as 20 m and (2) airborne (or respirable) lunar dust is defined as being 

10 m. There is therefore a departure in the use of the term “lunar dust” in the life support systems 

communities from the traditional use in lunar surface operations. 

Specifically, particles 10 m and below are expected to be readily entrained and aerosolized in the 

cabin airflow. As a cautionary remark, it should be mentioned that despite the 10-m cutoff for terrestrial 

aerosols, larger particles (10 m) may also become aerosolized in the lunar reduced-gravity 

environment. 

Lunar regolith dust particles—particularly the larger particles—also tend to have very irregular 

(nonspherical) shapes. Irregularly shaped particles tend to have larger surface areas and more angular 

(sharper) edges than regularly shaped particles. Larger surface areas provide increased surface 

interactions that can lead to larger net charged or reactive states of the particle. The sharper edges can 

contribute to particle abrasiveness. This irregularity is mainly due to micrometeorite impacts, which 

produce local melts and fracture the regolith particles. In contrast, recent scanning electron microscopy 

(SEM) images of very fine lunar dust particles (Ref. 2) do not tend to feature such irregular shapes. Also, 

particles derived from volcanic vent activities tend to be more spheroidal in shape. Given the different 

formation mechanisms, one would expect that lunar dust particles should exhibit a characteristic shape 

distribution. Indeed more data and analysis is needed to address this. 

Another property of lunar dust particles that merits attention is its reactive states. Multiple types of 

space events and conditions contribute to the excited energy states of the particles, including solar wind, 

solar flares, galactic cosmic rays, micrometeoroids, large thermal cycles, and ultrahigh vacuum. The 

result is the bombardment by high-energy particles onto the surface of particles, which produces charged 

and chemically active states that persist because the high-vacuum environment offers little passivation. It 

is unknown to what levels lunar dust will remain activated when introduced inside a pressurized 

environment with a finite humidity level. If there is little passivation, human exposure to activated lunar 

dust particles is potentially quite toxic. 
NASA/TM—2009-215821 5 

4.1.2 Toxicology of Lunar Dust 

A common thread through the technology needs presented in the previous section (Table I) is the 

protection of the crew from exposure to lunar dust particles. The known toxicological effects of dust are 

dermal irritation and penetration, ocular irritation and corrosion, and upper- and lower-airway injury. The 

respirable dust content refers to particles from 10 m down to 0.1 m. The lower-airway injuries are 

more critical, involving the smallest particles (1 m), which can provoke edema, inflammation, fibrosis, 

and possibly cancer. Particles less than 0.1 m are expected to pass through the airways undeterred and 

exhaled back out.1

 NASA’s Lunar Airborne Dust Toxicity Assessment Group (LADTAG) was formed to 

determine the toxicological effects of lunar dust. Based on the literature and studies, the LADTAG has 

recommended a permissible exposure limit (PEL) for lunar dust particles of 0.05 mg/m3

 for aerodynamic 

particle size range of 0.1 to 10 m (see also the Constellation Program Human-Systems Integration 

Requirements (HSIR) document, Ref. 3). Note that this a mass-based requirement, which is independent 

of particle size in the 0.1 to 10 m range, and therefore does not discriminate whether there are more 

particles closer to 0.1 m, (more penetrating) than at 10 m in size. 

The LADTAG is currently pursuing additional characterization and physiological studies to better 

assess the effects of long-term exposure to lunar dust. An area of particular interest is the reactivity of 

lunar dust and how it interacts inside the moisture-rich environment of the human pulmonary system. 

Their research agenda includes a study of activation and deactivation properties of lunar dust particles, 

which will lead to further studies on the reactivation and the process of passivation of dust particles. 

Pathological studies of exposure to lunar dust via inhalation (intratracheal and intrapharyngeal 

instillation), cell culture toxicity, and mechanical and chemical toxicity through cutaneous and ocular 

contact are also on the agenda. One of the nearer term objectives is establishing a 6-month PEL by 2010. 

4.1.3. The Apollo Experience and Lessons Learned 

The Apollo missions were highly successful, accomplishing six remarkable Moon landings in just 

over 3 years. However, they also pointed out the nuisances and problems associated with operating on the 

lunar surface. It is now well known that the lunar dust entered and floated everywhere in the lunar 

excursion module (LEM) during the microgravity portion of its ascent to the command module. The dust 

affected the crew’s physiology (eyes, nose, and ears), producing some mild to allergic effects. As a result 

the crew tended to keep their helmets on until they reached the command module. The crew also observed 

that the dust did not appear to be filtered from the environment through the LiOH air revitalization 

system. 

Apollo 17 Commander Gene Cernan made a notable quote that summed up his experience with lunar 

dust: 

“You have to live with it but you’re continually fighting the dust problem both outside 

and inside the spacecraft. Once you get inside the spacecraft, as much as you dust 

yourself, you start taking off the suits and you have dust on your hands and your face and 

you’re walking in it. You can be as careful in cleaning up as you want to, but it just sort 

of inhabits every nook and cranny in the spacecraft and every pore in your skin.” 

Apollo 11 Astronaut Buzz Aldrin made a brief appearance at the workshop. When asked about the 

lunar dust, he could not recollect any specific problems or issues regarding it. However, he noted that he 

was only there for a few hours. 

 

1 Dissenting opinion on this premise arose arguing that the diffusional particle transport mechanism, which dominates particles 

<0.1 m, can produce increased interactions and consequently, adhesion with surfaces (i.e., tissue and vessel walls).
NASA/TM—2009-215821 6 

The Apollo crew debriefings recount first-hand experiences during the missions in dealing with lunar 

dust. The list below provides some of the key solutions and shortcomings obtained from the debriefings. 

(These were taken directly from the presentation material.) 

What worked: 

(1) Thermal and micrometeoroid garment (TMG) and dust covers were effective in protecting 

portable life support systems (PLSS) and suit components such as regulator sense ports, sublimators, and 

oxygen purge system (OPS) actuators. 

(2) Scrupulous brushing did reduce dust brought into the LEM after extravehicular activities (EVAs). 

(3) Arranging airflow from the command module to the LEM decreased dust transfer after ascent 

docking. 

(4) Cabin filters did remove dust from command module atmosphere. 

What did not work: 

(1) Brushing for dust removal was time consuming and not fully effective. 

(2) Significant dust always reentered the LEM with suits, gear, and samples after EVAs. 

(3) Significant dust transfer from suit to crew and liquid cooling garment (LCG) occurred during 

doffing. 

(4) Any cavities and crevices in the floor accumulated dust that later became a problem. 

(5) Sealing issues and sticky mechanisms took place on the Moon and on return flights. 

(6) Filters in the command module required frequent cleaning in return flight. 

These experiences comprise the most direct and relevant demonstrations of mitigating practices and 

challenges. However, it should be noted that the Apollo missions were generally short, from a few hours 

to a few days, and therefore these solutions may not be the most feasible over longer mission periods 

where significantly more lunar dust accumulation is expected. 

Also presented during the workshop were a collection of photographs that showed the extent of lunar 

dust contamination on the Apollo hardware. There were many photographs revealing the numerous pieces 

of hardware that were contaminated with lunar dust, particularly in the suit loop connectors and lines and 

in the air ducts of the command module. Figure 1 provides a telling example of lunar dust contamination 

on the cabin return air duct in the command module, a critical piece of life support equipment. 
NASA/TM—2009-215821 7 

4.1.4 Impact on Hardware 

In addition to toxicological effects, the lunar dust can impact or adversely affect equipment and 

instrumentation. Dust in general can have consequences in a wide range of hardware components, 

specifically causing degradation of seals and valves, breakdown of lubricants, jamming of moving parts, 

and creation of flow blockages. A good analog to lunar operations are Arabian Desert aircraft operations, 

where multiple problems associated with dust have been reported. The following is a list provided during 

the presentations (Ed Hogdson, Hamilton Sundstrand) on the Arabian Desert operations, which seems to 

have strong relevance to what may be expected from the lunar dust during lunar missions: 

(1) Frequently blocks filters 

(2) Damages bearings—need to preclude dust from bearings 

(3) Minimizes fan starts and stops 

(4) Erodes heat exchanger coatings and fins 

(5) Accumulates in small-diameter passages of valves 

(6) Accumulates in unique locations as a result of significant pressure changes 

(7) Erodes coatings and material on fan rotor leading and trailing edges 

(8) Clogs small orifices and builds up in eddy current areas, resulting in coefficient of discharge shifts 

It was noted that the sand did not affect packed bed performance or conformal coated electronics and that 

accumulation in the tip clearance of fans was not an issue. 

Additional hardware problems associated with the ECLSS of Constellation lunar surface systems are 

envisioned to include 

(1) Fouling of lubrication 

(2) Dust accumulation on the valve seats yielding internal leakage 

(3) Contamination of moving parts of rotary or linear multiport valves 

(4) Significant bearing damage, requiring particle separation management 

(5) Dust trapping and bypassing in sliding seals at filter edges 

(6) Dust accumulation similar to the International Space Station (ISS), causing flow blockage 

(7) Air quick-connects either not being connectable, or leaking 

There were also several general recommendations offered for future missions: 

(1) Provide high-recirculation-rate air cleanup with high-speed fans and high-efficiency particulate air 

(HEPA) filters. 

(2) Provide air showers in airlock. There will be a need to determine the effects of low-density gas in 

1/6g. 

(3) Provide vacuum cleaner fans and HEPA filters. 

(4) Include air sensor block (sensor assembly) with robust filters to withstand depressurization and 

repressurization of the cabin and airlock. 

(5) Protect all direct openings to the cabin. 

(6) Provide dust protection on depressurization and repressurization valves. 

(7) Design ECLSS for dust robustness. 

(8) Adapt operational scenarios to accommodate dust. 

As implemented in cleanroom protocols, a series of dust barrier stages may be used to provide general 

dust suppression for the pressurized cabin environment. Three recommended stages of dust barriers 

provided by the Hamilton Sundstrand representative are provided below. 
NASA/TM—2009-215821 8 

(1) First dust barriers (bottom of ladder) 

-Cleaning suits and equipment 

-Pad on ground with brushes 

-Sticky tape or materials wipes 

-Magnetic or electrical wands 

-Other methods 

(2) Second dust barriers (airlock and platform at top of ladder) 

-Floor with sticky peel and/or magnetic coats 

-Partial airlock repress with air jets and depressurization vacuuming of surfaces 

-Part of full airlock depressurization gas captured in collapsible bag 

-More surface brushes, wipes, and wands 

-Vacuum cleaner 

- Narrow port with high suction capability (high pressure difference) for cleaning surfaces 

-Wide port with high flow rate for filtering airborne dust 

(3) Third dust barriers (airlock and cabin) 

-Filtration for 0.1 m 

-Forced airflow through hatch from Orion to Altair

-Particle counter for 0.1 to 10 m that must have a size separator at the inlet 

4.1.5 Airlocks and Cabin Air Revitalization 

The Apollo missions lacked an airlock on the LEM, which exacerbated the transfer of lunar dust into 

the module. In light of this, future lunar surface spacecraft will be equipped with airlocks to greatly 

reduce the amount of lunar dust that is tracked back in after an EVA. Additional dust barrier technologies 

and approaches can be used to further suppress dust infiltration. For example, suitlocks are an attractive 

approach where the suits are donned and doffed through an interface directly on the suit. Techniques and 

approaches to more effectively clean off the extravehicular mobility units (EMUs), or surface spacesuit, 

and EVA equipment right outside and inside the airlock such as electrostatic methods, and nitrogen 

showers will be significant enhancements to dust mitigation. To accomplish this, a sister task under the 

ELS project led by NASA Johnson Space Center is developing portable air cleaning and vacuum cleaning 

technologies that will aid in the abatement of lunar dust in the airlock. 

The dust inside the vehicle ultimately has to be removed by the onboard elements of the life support 

system. The cabin air is maintained by a set of atmosphere revitalization systems, which cleanse and 

maintain breathable air inside the crew cabin. For spacecraft atmosphere revitalization, there are needs to 

recover, recycle (e.g., dry and purify), produce, store, and distribute the atmospheric gases. This 

processing involves separation, such as physical adsorption, absorption, and particulate filtration. For 

particulate removal, filtration—including inertial- and field- (e.g., electrostatic-) directed separations—is 

the prime method used. A proposed approach to spacecraft filtration is a multistage filtration consisting of 

screen filters, an inertial filter, and a high-efficiency filter. Similarly, most filtration systems used in 

terrestrial applications, which are at least two-stage systems consisting of a prefilter and a high-efficiency 

filter. The prefilter typically is used to reduce the load on the high-efficiency filter. In the proposed 

concept, the prefilter will capture particles 800 m. The inertial filter will capture particles 5 m, and 

the final high-efficiency filter will capture 5 m. 

The Constellation Program has provided estimates of lunar dust infiltration into the pressurized cabin 

of 227 g/suit-EVA (derived). Of the lunar dust particles that enter the spacecraft, only particles below 

10 m are expected to become airborne. This constitutes only about 7 percent by mass of the lunar 

regolith. This is still a significant amount of contamination that will lead to high levels of airborne dust. 

Although the focus of the workshop was of the entry of lunar dust into the cabin, there will also be a 

generic, biologic component: internally generated dust. Table II summarizes the separate particulate PELs 
NASA/TM—2009-215821 9 

for both internally generated and lunar dust as well as biological matter. Just as on the ISS, particulate 

matter will be generated from background materials in the interior of the cabin and from biological 

matter, such as skin flakes, hair, and lint. The rationale for the lunar dust permissible limit has been 

provided in Section 4.1.2 on lunar dust toxicology. The remainder of the table mimics the ISS PELs for 

internally generated dust and biological growth. An issue regarding the two particulate matter 

requirements is that the lunar and generic dust will be indistinguishable to the filtration system. Therefore, 

the combined load of the lunar regolith and generic dust will have to be treated and maintained at the 

accepted LADTAG PEL of 0.05 mg/m3

 for the particle range of 0.1 to 10 m. As a result, the allowable 

dust load of lunar dust is actually more stringent than the PEL represents. 

TABLE II.—PARTICULATE REQUIREMENTS FOR LUNAR SURFACE SYSTEMS 

Type Requirement 

Internally generated particulate contamination 0.5 to 100 m aerodynamic diameter, 

0.2 mg/m3

0.3 mg/person-min 

Lunar dust contaminationa 0.1 and 10 m aerodynamic diameter, 

0.05 mg/m3

Bacterialb 1000 CFU/m3

1640 CFU/person-min 

Fungalb 100 CFU/m3

1640 CFU/person-min a

Limit under review, final by 2010. 

b

CFU is colony-forming unit. 

These permissible limits (Table II) and more details on them can also be found in the Constellation 

Program HSIR document (Ref. 3). 

4.2 Testing Concepts 

The testing phase is an important component of filter and separations technology development. 

Several presentations were provided in this area. Two of the presentations highlighted (1) the Lunar Dust 

Filtration Testing Facility being developed at the NASA Glenn Research Center and (2) industrial testing 

standards and methodologies used in current testing facilities. An overview was also provided of the lunar 

simulant development being led by the NASA Marshall Space Flight Center. Lunar simulant development 

is ongoing and continues to lead to higher fidelity soils and dust particles that can be used for testing. 

Lastly, the capabilities of reduced-gravity facilities as testing platforms were also provided. 

The Lunar Dust Filtration Testing Facility directly supports particulate matter filtration and 

separations technologies under the ELS project. The facility is designed with a closed-loop architecture 

that is capable of operating at reduced pressures of 8.3 psia for the Altair lunar lander and outpost habitat 

and 4 psia for pressurized airlocks. The facility also features variable flow rates up to 100 scfm (standard 

ft3

/min) without a filter, an internal particle delivery system, and multiple window and instrument ports. 

Instrumentation and diagnostics included in the facility are an orifice flow meter; differential, absolute 

and vacuum pressure transducers; optical particle detectors; laser light sheet imaging; high-speed 

imaging; and particle image velocimetry (PIV). 

A presentation on industry testing standards was provided by Dr. Hanley of RTI International. At the 

outset it was stated that industry standards apply to specific technologies and applications. When the 

application deviates from the baseline, the assumptions and protocols of the standard may not be valid. 

The standard used in industry is the American Society of Heating, Refrigerating and Air-Conditioning 

Engineers (ASHRAE) Standard 52.2 (Ref. 4). Many valuable guidelines and tips were provided for 

testing in the filtration facility. Chiefly, it was strongly suggested that qualification and control tests with 
NASA/TM—2009-215821 10 

standard well-characterized media be performed to verify the facility performance. As data is interpreted, 

it was cautioned that results should closely follow well-established filtration theory. It was also mentioned 

that testing in a relevant environment (or conditions), as is the case with the Lunar Dust Filtration Testing 

Facility, was a proper approach. 

An overview of the simulant development managed at Marshall was given. The chief activities are 

determining users needs, lunar dust characterization, finding sources and processes for simulant 

production, developing and characterizing simulants, and educating users on the handling of the 

simulants. The main properties being characterized are particle size distribution, particle shape 

distribution, and bulk density properties. These are precisely the properties that impact the measurement 

of irregularly shaped airborne particle or aerosols. Figures of merits are being established to provide an 

accepted comparison between granular assemblies of particles. The use of Glenn's new multistage axial 

cyclone was touted as a key piece of equipment for lunar simulant characterization research. This device 

can size classify particles from 10 m to 20 nm. 

Several key pieces of information are needed to gain confidence in the use of simulants in filter 

testing as they relate to particle measurements. The shape distribution of lunar regolith and simulant dust 

particles is considered critical information. Aerosol measurements are based on the assumption of 

spherically shaped particles. For particle size measurements using optical particle counters (OPCs), the 

index of refraction of these particles is needed. For calibration purposes, Glenn’s axial cyclone can be 

used to provide monodispersed particle samples of lunar simulant to perform a set of controlled 

calibration tests. Although use of OPCs for filter testing is widespread, it was suggested that consideration 

be given to mass-based measurements that relate better to the capturing mechanisms of filters. 

An overview of available reduced-gravity facilities to conduct research, demonstration, and testing 

was also presented. The Reduced Gravity Office (RGO) at Ellington Field, Houston, provides the C–9B 

aircraft to support conceptual development (TRL of 1 to 3) of components and systems and to support 

limited technology demonstrations and evaluations (TRL 5 to 6) of components and systems under 

planned operational environment (i.e., short-duration microgravity and partial gravity). Recently, the 

RGO has provided aircraft support through the privately owned ZERO-G aircraft. NASA Glenn also has 

two drop facilities: the 2.2-Second Drop Tower and the Zero Gravity Research Facility. These facilities 

provide engineering and technician support for hardware buildup. Interfaces ranging from video, analog 

data, and programmable logic control during the drop can be provided. 

4.3 Filtration Technologies 

The presentations ranged in scope from state-of-the-art technologies to developmental technologies. 

A good overview of the state-of-the-art high-efficiency filtration was given by Dr. Vijayakumar (Aerfil 

LLC). Applications of HEPA filters in tractor cabins were presented as relevant to spacecraft filtration. 

Developmental filtration media and technologies included ceramic filter and multistage or component 

cyclone separators. 

There is a lack of international consensus on the definition of high-efficiency filtration. In fact some 

of the standards are quite disparate: 

(1) European standard EN 1822–1 (Ref. 5): 85 percent 

(2) U.S. standard AHSRAE 52.2 (Ref. 4): 95 percent and higher 

(3) NASA (ISS) standard: 99.97 percent at 0.3 m (per MIL standard 282, 

Ref. 6) 

The ones most relevant to NASA’s exploration goals are the U.S. and NASA standards. NASA’s 

lunar missions can consider the industry best practice of 99.99 percent capturing efficiency as an initial 

target. 

The virtues of fibrous media filters in high-efficiency filtration were stressed. Invariably these are 

used in conjunction with a prefilter, to extend the life of the filter. The advantages are, first, that filtration 

takes place throughout the media (surface and depth). The particle loading or removal can range from 
NASA/TM—2009-215821 11 

very low to very high, based on configuration and application. Capturing occurs over a wide range of 

particle sizes down to ultrafines. Flow resistance, however, increases with efficiency as well as over time 

with the cummulative particle loading. Because fibrous filters are generally depth filters, particles are 

subjected to the three capturing mechanisms: diffusion, interception, and impaction. This simply implies 

that all particle sizes are captured, except in the range from 0.1 to 0.3 m where they are captured with a 

moderately lower efficiency (in the range of 99 percent and lower depending on filter face velocity). This 

not strictly the case for surface filters, which only capture particles larger than their pore size (or what is 

captured in the dust cake). 

Another advantage is that these filters are well characterized. In fact, the industry does an excellent 

job of characterizing the performance efficiency under standardized test conditions, which are sufficient 

to extrapolate to give performance and life estimates based on application. In particular, all HEPA filters 

are 100 percent tested before they go to market. A roll filter concept was introduced as a type of filter 

configuration that would provide extended filter life by periodic advancement of the filter media. This 

configuration could incorporate any of the filter media types presented in Table III. Potentially, the rolling 

process can be automated to reduce or eliminate crew maintenance time. Another configuration is a 

portable fan filter unit that can be used under circumstances where elevated levels of airborne dust are 

expected for localized and short-term filtration. 

 TABLE III.—FIBROUS MEDIA COMPARISON CHART 

Mediuma

 Property

Efficiency Capacity Thickness Mechanical Processability Typical filter 

usesb 

Fabrication 

Dry laid Very low Very 

high Thick Robust Easy Prefilter 

Spun bond Low High Various Robust Easy Prefilter, 

backing layer 

Melt blown 

Medium 

to 

high 

High Thick Robust, soft, and 

multilayer 

Easy except 

close pleat 

HVAC, 

appliance 

Glass 

blanket Medium High Thick 

Robust, dusty, 

and 

multilayer 

Easy except 

close pleat HVAC 

Material 

Cellulose Low High Moderate Robust and stiff Easy Engine, 

turbine 

Microglass 

Medium 

to 

very high 

Low Thin Delicate Hard HVAC, ULPA and 

HEPA 

PTFE Very high Very low Very thin Robust and soft Specialized HEPA and ULPA a

PTFE is polytetrafluoroethylene. 

b

HVAC is heating, ventilation, and air conditioning; ULPA is ultralow penetration air; and HEPA is high-efficiency particulate air. 

Fibrous filter media fabrication encompasses several web formation methods and fiber fabrication 

techniques, which include (in order of increasing efficiency): dry laid, spun bond, melt blown, glass 

blanket, cellulose, microglass, and PTFE (or Teflon (DuPont)). A summary of the different media types 

and their general uses are presented in Table III. Media selection is based on four main criteria: 

performance needs, cost benefit, filter design, and end use. “Performance needs” refers to the efficiency 

and capacity balanced against resistance. Typically, cost scales with efficiency. However, cost is not 

expected to be a real driver since NASA is expected to seek custom filter designs. Filter design and end 

use depend upon the application, which can range from prefilters to HEPA and ultralow penetration air 

(ULPA) filters. NASA’s final filter design for lunar surface systems will undoubtedly include the use of 

high-efficiency filters to capture all particles of concern to NASA, 0.1 to 100 m (see Table I), before 

entering the next segment of the life support loop. Note, however, that as stated above, particles below 

0.1 m should, in principle, all be captured by the fibrous filter because of the diffusional capturing 

mechanism. Another important factor that impacts performance is media velocity (Fig. 2). Efficiency 
NASA/TM—2009-215821 12 

decreases exponentially with increasing media velocity and increases significantly with decreasing media 

velocity. The key message is that fibrous filters can be configured to play a primary role in a multistage 

filtration system. 

The site construction industry offers another perspective on the use of air filters. Tractor vehicles 

operate in extremely dusty environments, relying on the cabin filters to provide the only protection 

against the environment. A three-stage filter stack, consisting of a prefilter, HEPA filter, and carbon filter 

is used in fresh air intake and recirculating modes. The American Society of Agricultural Engineers 

(ASAE) S525 standard dictates that the air intake filters should be 95 or 99 percent efficient at 3 m, with 

and without recirculation, respectively. It is important in this application to periodically inspect the seals 

around the filter stack. The seal is maintained by compressing the filter stack to ensure contact between 

the filter housing gasket and the supporting flange. Field data indicate that leaks in the filter stack can 

increase particle penetration by an order of magnitude. Recirculating the air, on the other hand, increases 

protection factors by an order of magnitude. 

Lesser known in air filtration, sintered porous metal filters offer features that cross the boundary 

between high efficiency and prefiltering efficiency. Typically used for high-pressure gas filtration, they 

have several advantages that make them attractive. These include a high-strength matrix, washability, 

high loading capacity, and a wide range of filtration efficiencies from prefiltration to high-efficiency 

filtration. However, they usually produce high pressure drops. Their rugged construction allows them to 

be easily backwashed for regeneration. A possible application for spacecraft could be as a prefilter. It 

should be noted that ceramic filters potentially offer similar advantages as the sintered porous metal 

filters. 

Lastly, Professor David Pui, Director of the Center for Filtration Research at the University of 

Minnesota, which is a consortium of filtration companies and academic researchers, presented the work 

being conducted at the Center. The Center is involved in a wide range of cutting-edge research topics, 

such as nanoparticle and nanofiber filtration, cabin air filtration, and multicomponent cyclone filtration. 

The concept of thermal rebound of nanoparticles was introduced, which although intriguing, is not 

thought to play a major factor in the filter efficiency. A nanofiber filter and cyclone combination was 

proposed as a concept for lunar dust filtration. 

4.4 Small Business Innovation Research Technologies 

Several principal investigators from active Small Business Innovation Research (SBIR) projects with 

ties to lunar dust filters and simulant development presented details of their work. These projects 

showcased the advanced developments funded by NASA, incorporating cutting-edge technologies. These 

technologies included carbon nanofibers, a novel electrospray technology for charging particle surfaces, 

and lunar simulant particle development. 

Connecticut Analytical Corporation presented a novel approach to electrostatically enhancing 

particulates. It relies on electrospray ionization, in which desorbed electrospray droplets exhibit a capacity 
NASA/TM—2009-215821 13 

to attract polar molecules and particulates from the surrounding air with a high degree of efficiency. This 

technology can be used to assist filtration capturing of particulates onto surfaces of conducting fibers and 

surfaces. Experimental demonstration by the company has shown that by using the electrospray 

technology, lunar simulant dust particles can be effectively scrubbed from the air. The technology offers 

extremely low power consumption, zero pressure drop, and no ozone production. 

Seldon Technologies presented their phase I work on the development of a fused carbon nanofiber 

filter using their patented Nanomesh filter medium for lunar dust filtration. The advantages of carbon 

nanofibers are their high fiber strength, large surface area that can be chemically functionalized, 

conductivity, and low flow resistance. Seldon’s carbon nanofibers also offer high aspect (length-todiameter) ratios, which reduces the chances for shedding of fibers from the matrix. The company is 

investigating the performance of two flow configurations: a flow-through and a cross-flow configuration. 

Results show that the flow-through configuration yielded an efficiency of 99.6 percent for particles in the 

size range of 0.3 to 0.5 m at elevated velocities of 12 m/min, but at significant pressure drops (i.e., 

450 Pa). In the cross-flow configuration an efficiency of 84 percent was achieved but at a pressure drop of 

only 5 Pa. Modified filter designs are being pursued to improve the performance and capacity of both 

filter configurations. 

Agave Biosystems is also developing novel carbon-nanofiber-based filter system for lunar dust 

filtration. The company grows the carbon nanofibers onto stainless steel meshes and arranges them in a 

stack with an emitter and a receiver mesh, to form a novel electrostatic device capable of capturing 

microparticles and nanoparticles. The multilayer design of carbon-nanotube- (CNT-) based filter 

significantly reduces the system footprint. Besides the advantage of its high surface area for capturing 

efficiency, the CNT elements are excellent conductors and make highly efficient field emission devices. 

The emitters charge the incoming particles, which are then collected with greater affinity onto the receiver 

mesh (last layer). Because of the geometric enhancement factors—greater than 1000 for nanofibers—

lower threshold voltages (~1 V/m) will be required to achieve field emission. In their next-generation 

devices, Agave plans to scale up their devices by incorporating multicomponent CNT stacks in parallel 

plate and concentric tube configurations. 

Orbital Technologies Corporation is developing high-fidelity simulants that better represent the 

agglutinate character and Fe0

- rich particles found in the lunar regolith particles. The company has 

produced several simulants based on earlier JSC-1a (Johnson Space Center Number 1a) and NU-LHT 

(NASA/USGS (United States Geological Survey)-Lunar Highlands Type) simulants. Characterization has 

shown striking similarities between these prototype simulants and the lunar regolith particles. 

5.0 Splinter Sessions 

The workshop provided an opportunity for in-depth interaction, exchange of ideas, and a 

brainstorming of ideas among the industry experts, NASA researchers, and NASA programmatic 

managers. The four topics on the agenda helped to provide focused discussion although there were some 

obvious overlaps between topics. The workshop participants were broken out into four groups based on 

their expertise and stake on these topics. The splinter session was conducted during most of the second 

day and included a report-out session. 

In addition to guidance given by the topic descriptions, the participants were also asked to discuss and 

address the following: 

(1) Identify objectives or requirements (e.g., higher efficiency of ultrafines). 

(2) Identify viable state-of-the-art technologies and discuss how they will address the needs. 

(3) Address knowledge or technology gaps. 

(4) Identify all viable research and technology areas and prioritize. 

(5) Develop a roadmap for technology development and implementation. 
NASA/TM—2009-215821 14 

The splinter sessions proceeded with the notion that the requirements for the lunar surface system 

vehicles were still not well defined, and therefore assumptions were made when needed. The following 

assumptions were considered. First with respect to the pressurized cabin, assumptions about the air 

handling rates were made based on cabin volume and the number of air exchanges. The lander cabin was 

approximated at 20 m3

 with a 15-m3 airlock. Five air exchanges are typical in terrestrial applications, 

which in this case would yield a total cabin flow rate of approximately 60 cfm. For reference, the ISS 

Destiny module total flow rate is driven by bacterial removal and can get as high as 232 cfm. Note that 

the Destiny module has a volume 3 times as large, which indicates that the volumetric flow rate 

requirements are actually similar. These air handling rates will vary based on spacecraft architecture and 

the requirements for cooling and mixing of gases of the breathable air. 

Another unknown was the airborne lunar dust loading conditions in the cabins due to EVA activities. 

From the presentation material it was assumed that about 227 g/suit-EVA with typical two-person EVA 

passes into the cabin. However, not all the dust particles become aerosolized, but rather only particles 

10 m and below, which amounts to only about 7 percent of the lunar dust, do so. This can still become a 

significant loading condition. An estimate of the airborne lunar dust loading condition amounting to about 

1.5 g/m3

 was recently derived by the ELS project Dust Mitigation and Control task (Jan. 2009). 

The conceptual paradigm for vehicle cabin air filtration used in the discussions was a multistage 

filtration system that will facilitate both performance and regeneration efficiency. The two main 

components will be a prefilter or bulk filter for the first stage and a high-efficiency filter in the last stage. 

Their applications were discussed separately because of the different requirements they entail. It was 

thought that even for portable filters and vacuum cleaners both technologies will play a role, although 

they may have different requirements or operational protocols than in vehicle cabin filtration in general. 

Finally, testing was thought to be a vital part in demonstrating and qualifying candidate filtration 

component and systems. 

Each of the sessions provided valuable information and recommendations. The High-Efficiency 

Filtration and the Bulk Filtration and Regeneration sessions provided more detail on the main filtration 

requirements. The other sessions built on or referred to these requirements and contributed other 

application specific requirements. Each session identified important gaps and provided sensible research 

and technology directions. Details from each of the individual session are provided in the next few 

subsections. 

5.1 High-Efficiency Filtration 

High-efficiency filters will be essential to maintaining a safe environment for the crew during lunar 

landing and outpost missions. The lunar dust that enters the pressurized cabin is thought to contain a 

significant amount of fines and ultrafines that will need to be filtered out. Decisions have to be made 

about the requirements for these filters, and about the most suitable type of filters and/or filter enhancing 

techniques and materials. For guidance, the currently established allowable particulate matter limit set by 

the Lunar Airborne Dust Toxicity Advisory Group (LADTAG) is 50 g/m3

. Effects regarding the 

properties (or currently known properties) of the lunar regolith dust on the capturing efficiency and 

longevity of the filter, as well as the impact on equipment (e.g., blowers and other air revitalization 

systems), should also be addressed. 

5.1.1 Requirements 

High-efficiency filters are expected to fill several needs in lunar surface systems. They will play the 

prime role in the capturing of fine and ultrafine particulates, thereby making their use indispensable where 

crew presence is involved. The PELs for these filters were given in Table II. They are listed here again for 

discussion: 

(1) For lunar dust particles (LADTAG PEL): 

0.1 and 10 m aerodynamic diameter 
NASA/TM—2009-215821 15 

(2) For internally generated dust particles (ISS PEL): 

0.5 to 100 m in aerodynamic diameter 

and/or 

0.3 mg/person-min in this size range 

(3) For bacterial particles (where CFU is “colony-forming unit”): 

1000 CFU/m3

and 

1640 CFU/person-min 

(4) For fungal particles: 

100 CFU/m3 

and 

 1640 CFU/person-min 

The first two requirements reflect the particulate requirements. Note that high-efficiency filters are 

sensitive to the penetration of the particles of sizes around the lower bound of these requirements. The 

implications of this are discussed and will be presented subsequently. The second two requirements 

regarding bacterial and fungal growth were adopted from the ISS requirements on biological 

contamination. Lastly, it was emphasized that the filters or dust mitigation methods employed in the 

airlock must be able to handle the intrusion of 227 g/suit-EVA (derived) of lunar dust. 

5.1.2 State-of-the-Art Technologies 

The PEL is mostly achievable by state-of-the-art high-efficiency filters. Thus this session provided 

much detail on fibrous filters. Their applications will be in the atmosphere revitalization systems, in 

vacuum cleaners and portable filters, and in supply lines of suit loops (suit loops will run at 2.810–3 to 

3.810–3 m3

/s (6 to 8 cfm) per person, 1.110–2 to 1.510–2 m3/s (24 to 32 cfm) total). Although highly 

efficient in most of the particle ranges, in the range of 100 to 300 nm the mechanism of diffusion tapers 

off while that of interception starts to ramp up, leading to a slight drop in efficiency in this range that is 

exacerbated by increasing flow face velocity. This range is coincidentally within the range of respirable 

particles that can affect the lower airway of the human physiology. It should be noted that there is no 

100 percent efficient filter, so it needs to be determined if this drop in efficiency can be contended with 

through operational parameters, filter design changes or filter capturing enhancements in order to meet 

the PEL. 

Fibrous filters are depth filters and as such the three capturing mechanisms—diffusion, interception, 

and impaction—propagate throughout the depth of the media, allowing for more capturing area and 

therefore higher efficiency. Microfiberglass is the dominant material for these, which is rated at a range of 

1 to 10 log reductions or (known in the industry as seven 9s or more technically as 99.99999 percent 

efficient) depending on configuration and flow face velocity. Its advantages are its simplicity and 

industrial track record, and that it can be scalable in size and performance. The disadvantages are that it 

can become consumed or loaded quite rapidly, depending on configuration and environment, and it is also 

susceptible to moisture. However, there are methods to engineer them to be moisture resistant. 

Some discussion was given on the effects of air handling rates. Consider that the LADTAG PEL is 

hourly based, with no peak requirements provided (currently). Modifying the flow rates will have 

competing effects. First, increasing the number of air exchanges an hour, thus increasing the flow rates, 

will tend to increase the capturing efficiency since the volume of air in the cabin is cycled through the 

filters more rapidly and more frequently. However, as stated above the filter efficiency decreases 

exponentially with increasing face velocity. Clearly, a trade study or assessment of hourly efficiency 

versus volumetric flow rates is required. 
NASA/TM—2009-215821 16 

It was emphasized that “we have the technology we just need to know how to package it.” In other 

words, state-of-the-art filters will do the job; they just need to be packaged in a system that is responsive 

to NASA’s long-duration filtration goals. Firstly, they have to be tailored to meet NASA’s requirements 

and needs; that is, the lunar dust PEL, the handling of lunar dust intrusion rates and cabin flow rates. 

Some of these requirements are tentative until more relevant data become available and may not be 

finalized until NASA’s first return to the lunar surface. Additionally, the filtration system will have to be 

packaged to meet the low-upmass, low-maintenance, and power requirements. Regeneration will be 

desirable, but it was stressed that high-efficiency fibrous filters are very difficult to regenerate. 

5.1.3 Knowledge and Technology Gaps 

Several knowledge and technology gaps were discussed. Methods for the safe removal, storage, and 

disposal of disposable filter elements will need to be developed. Note that both lunar regolith dust and 

generic particulate matter will be lumped together in the captured material in the cabin filtration system. 

Therefore a revised PEL for the combined matter, based on an analysis of the proportions of lunar and 

generic dust, may be needed. Estimates need to be derived for the weight and volume of filter systems, as 

well as for operational parameters such as power consumption, waste handling, crew involvement, and 

lastly cost. The additional effects of humidity on small particulate dust in the cabin atmosphere, which 

can cause clumping of particles, should be studied. The abrasiveness of dust, which can damage moving 

parts and shorten material life, including the filter element, also needs attention. Finally, modeling of 

spacecraft fan volumetric flow rates, filter system volume, and particulate removal performance and 

efficiency, are needed to help derive requirements. 

5.1.4 Viable Research and Technology Areas 

Viable technologies included those associated with the SBIR technologies. Carbon nanotubes (CNTs) 

may provide high loading capacity and high efficiency. In certain configurations they can also be 

regenerated, as is being considered by Seldon. An issue with CNT is the shedding of fibers off the 

webbing or fiber matrix. Seldon uses extremely long fibers (high aspect ratio) in their patented Nanomex 

filter media, which should preclude this effect. The electrospray work by Connecticut Analytical 

Corporation for charging the dust is also attractive as a way to enhance a filtration system by capturing 

through electrostatic attraction of charged particles. 

Several brainstorming ideas were also provided, mostly dealing with barrier technologies inside the 

airlock. The first was the idea of using an airlock electrostatic system, in which the suit is the cathode and 

walls or floor area is the anode, to drive off the dust from the suit. This must be considered as part of an 

overall spacecraft dust mitigation system. A few other operational concepts to mitigate dust in the airlock 

were also provided. To prevent dust from entering the cabin, the airlock pressure should be slightly 

negative with respect to cabin, including when the hatch is opened. This will ensure that the airflow 

between these volumes is always toward the airlock. A vacuum cleaning system for the airlock could 

simply be a hose connected to the outside vacuum of the lunar surface. In this case a system trade study 

against gas loss needs to be performed; it was emphasized that the direction of air circulation in general 

should be maintained in the direction from clean to dirty areas. 

5.1.5 Roadmap and Schedule 

Several priorities in the development of high-efficiency filters were identified. A multistage filter 

housing was envisioned. In this case, the filter housing will be the first development. Thereafter the 

replaceable filter elements can continue to be developed late in vehicle development since housings and 

specifications are fixed ahead of time. Correspondingly, there are two requirement developments: specify 

(1) the interface requirements between the housing and the air revitalization loop and (2) the interface 

requirements of the filter elements with the housing. Demonstration and proofs of concepts will be part of 

this roadmap. 
NASA/TM—2009-215821 17 

5.2 Bulk Filtration and Regeneration 

Lunar surface filtration systems will likely be designed as multistage systems. Prescreens and 

prefilters prior to the high-efficiency filter will likely be used. The particle size and mass fraction handled 

by the prestage bulk filters should be addressed. Regeneration, or cleaning of the filters, will be helpful in 

reducing the upmass and accumulation of filter elements during these long missions. The following 

questions will be addressed and discussed: 

(1) What filtration or separation techniques are most appropriate? 

(2) What level of regeneration makes sense? 

(3) How much power and downtime should be given to regeneration? 

(4) Are there any in-place or in-service regeneration systems that can be used? 

Keeping in line with the multistage filtration concept, the bulk filtration stage will be a key 

component in helping meet the requirements of the high-efficiency filter. Because it is the first stage of 

filtration, this prefiltration stage has to capture as much of the bulk particulate material as possible in 

order to protect and extend the life of the high-efficiency filter. The high-efficiency filter will capture the 

remainder of the particulate load to meet the PEL; therefore, the atmospheric particulate requirement for 

the bulk filter can be less stringent than the PEL. In this case, an interface requirement between the 

prefiltration and the high-efficiency filter should be established. Other major drivers for the bulk filter 

will be operational and maintenance optimization, as well as upmass constraints. 

5.2.1 Requirements 

Recommendations for requirements were that the bulk filter should possess 

(1) The ability to capture 100 percent of particles larger than 20 m, and most of the particles down to 

5 m 

(2) No expandable media 

(3) Extended (5-year) operational life 

(4) Less than 249 Pa (1 in. H2O) pressure drop 

(5) Requirement constraints for weight, power, and volume 

(6) Flow requirement (needed for full-scale test) 

(7) Minimal maintenance 

5.2.2 State-of-the-Art Technologies 

There are two main bulk filter options. One is a prefilter or precleaner where dust is collected by a 

more porous filter. Over time a dust cake eventually forms increasing the flow resistance, and the filter 

has to be cleaned or discarded. Although not usually performed as a common practice, these filters 

because of their higher porosity can potentially be regenerated. Screens are typically used for prefilters. 

These are simple filter structures that capture the larger bulk material and can be easily cleaned using a 

vacuum cleaner. However, they allow a significant amount of small particles through, which increases the 

particle load on the next stage of filtration. A good alternative may be the sintered metal or ceramic filters 

described in Section 4.3, “Filtration Technologies.” These filters are better at capturing the smaller 

particles and provide high loading capacity. 

The other technology option is an inertial filter, which could take the form of a cyclone filter, 

impingement plate, or baffle. A (sharp) bend or trap could serve the same purpose but may not be as 

effective. These devices are governed by the interception and impaction mechanism, and their theory is 

well established. These devices are very efficient at capturing particles above a specified cutoff size. The 

advantage of cyclones is that they can provide very large inertial force to separate out a larger range of 
NASA/TM—2009-215821 18 

particle sizes and densities. The larger the inertial force the lower the cutoff size of particles it can 

capture, that is, they capture down to a smaller particle size. They can also handle large amounts of dust, 

which makes them well suited for large industrial materials handling applications. The capturing 

efficiencies of cyclones are typically specified in terms of the d50 (the median cut point, or the particle 

diameter corresponding to the midpoint of the penetration curve) efficiency and can go down to single 

micron levels. However these devices typically produce relatively large pressure drops. 

Bulk filters may also be more amenable to regeneration since the bulk material is more loosely held 

by the filtration media or surfaces. Regeneration could either be performed in place or via some 

maintenance process where there is some physical removal of the dust, outside of the flow loop. The 

former is obviously more advantageous. As an example, the cyclone separator has the advantage of larger 

retention capacity, but if used in a collection cup/bag configuration, as is typical, the dust mass needs to 

be physically removed by someone, or through a mechanism when the system is offline, and discarded. 

Alternatively, screens or porous (e.g., ceramic and sintered-metal) filters can be regenerated in place 

through backflow and backflow pulsing. The backflow can potentially be vented outside. This raises the 

question of whether biological dust can be vented out onto the lunar surface as well. 

5.2.3 Knowledge and Technology Gaps 

Several knowledge and technology gaps were identified. First, there is a need to refine or generate 

alternate lunar regolith load models in order to better define the intrusion rate inside the pressurized 

volume. The Constellation-derived estimate may be overly conservative. A higher fidelity model of the 

intrusion rate will help better refine the expected airborne particulate concentration after an EVA. 

Another unknown is the future direction of the health standard. During the workshop there was talk of 

movements in the community for considering particle surface area as a standard for the measurement of 

permissible limits. A shift in the standard can strongly affect the technology now being considered.

For regenerative filters, methods for the capture, removal, storage, and disposal of collected 

particulates need to be developed. The regeneration method (e.g., whether reverse airflow or vacuum 

pulse) will require development and demonstration. Lastly, the effects of the lunar dust abrasion on the 

filter media life and filter life after repeated regenerations also need to be determined. 

5.2.4 Viable Research and Technology Areas 

In general, the consensus in this session was also that the technology exists. The challenge is to select 

the right combination that produces the desired performance. A proof of concept will be required to 

demonstrate feasibility and show that it can meet power requirements. A conceptual model was provided 

(Fig. 3). 

Several general research recommendations were provided. The first order of business should be to 

firm up requirements. This will facilitate an assessment of the trade space for the different filter 

technologies. Once the technologies have been narrowed down, their feasibility has to be shown through 

scaled and full-scale models and their performance demonstrated. At a more basic level, the 
NASA/TM—2009-215821 19 

effects of cohesion of the lunar dust and its adhesion to surfaces should be investigated. These areas of 

investigation will benefit from a facility that can serve as an airlock suitable for low-g aircraft. Also 

importantly, the facility should be able to simulate the reduced pressures that will be encountered in lunar 

surface systems. 

5.2.5 Roadmap and Schedule 

A list of priorities and schedule milestones were formulated. First, the requirements need to be firmed 

up, backed by relevant basic research. The Lunar Dust Filtration Testing Facility at Glenn Research 

Center should be finalized, and its performance and capabilities should be demonstrated. In the 

development, the top contenders in the trade space need to be established. From these, down selection to 

the top two is advisable. Detailed development can take place thereafter, which includes testing and 

evaluation, incorporating reduced gravity and low pressure. The final design should be ready for infusion 

into the Lunar Lander PDR in 2014. 

5.3 Portable Filtration and Vacuum Cleaning Systems 

Portable filtration and efficient dust removal is essential for the lunar lander’s habitable volume and 

outpost missions. Currently, there is no prevention or capture mechanism in place for dust mitigation. 

NASA Johnson Space Center is investigating current industry technologies and filtration systems to 

address dust removal in the habitable volumes and airlock. The following questions will be addressed and 

discussed: 

(1) What filtration and separation techniques are most appropriate? 

(2) What requirements should the vacuum cleaner consider (e.g., power, filtration, flow rates, air 

pressure, etc.)? 

(3) What are some methods to separate out internally generated particles from lunar dust? 

(4) Is there a conservative estimation on how much dust that can enter the airlock, and then how much 

that may enter the habitable volume? 

(5) Are there any existing technologies that can be utilized for capturing varying particle sizes in 

portable systems? 

The technology development objective here is a modified portable vacuum cleaner to filter air in all 

habitable volumes, including the airlock after represses, and in the pressurized cabins in Altair and Orion. 

The vacuum cleaner will need to capture varying-sized dust particles (from less than 0.05 m up to 

pebble-sized Moon rocks). The vacuum cleaner will have the ability to clean suits (via vacuum 

attachments, like stiff brushes), and mechanical hardware. 

5.3.1 Requirements 

A list of requirements was formulated:

(1) Lightweight unit 

(2) Short crew time for filter replacement and/or vacuum maintenance 

(3) Low power consumption 

(4) Filtration of airlock air to a determined counts per cubic meter, complete in 30 min to 1 h 

(5) Acoustics levels to be determined 

(6) Vacuum surviving repressurization and depressurization in airlock 

(7) Heat rejection to be determined 

(8) Resistance of unit to abrasion and sharp edges 

(9) Human factor considerations with donned suits, maintenance of the vacuum cleaner (filter change, 

use of attachments, etc.) 
NASA/TM—2009-215821 20 

An operational scenario (presented by H. Rotter of NASA Johnson Space Center) was adopted in 

which it takes an estimated 30 min for a crew member to enter the airlock from the lunar surface, 

repressurize the airlock, and doff the suits. It is envisioned that the use of a vacuum cleaner to clean the 

suits and filter the air before opening the hatch will reduce crew time waiting on complete airlock 

filtration. The Constellation Program assessment of 227 g of lunar regolith per crew member per EVA 

should be considered in the analysis for determining the requirement for the vacuum cleaner unit. 

5.3.2 State-of-the-Art Technologies 

It is assumed that current state-of-the-art vacuum cleaning technologies will play a role in the 

spacecraft vacuum cleaning and portable filter development. The state-of-the-art technologies for highefficiency and bulk filtration as described in the two preceding sessions will also apply to this 

development. In addition, any breakthroughs and future directions in these technologies will be 

considered.

5.3.3 Knowledge and Technology Gaps 

A few knowledge and technology gaps were identified. First, the type and amount of power that will 

be available to the vacuum cleaner in each vehicle (airlock, Altair, Orion, etc.) should be determined. 

While this will drive the power consumption requirement for the vacuum cleaner, it may in turn indicate 

necessary system power allocations on the spacecraft. Secondly, more guidance on the toxicology 

requirements is needed. For example, will there be different requirements for short-term versus long-term 

exposure? The short-term exposure is particularly relevant in the airlock. Therefore better guidance is 

needed on the requirements for particle counts in the airlock before the hatch to the cabin is opened 

relative to the pressurized cabin.

5.3.4 Viable Research and Technology Areas 

Two areas of research were provided. The first called for computational fluid dynamics (CFD) 

modeling analysis to calculate the quantity of particles in the air and how long they take to settle in 1/6g 

environment—based on the known 1g environment. The other is in the area of testing and the 

development of a potential airlock simulator. The simulator would be used to properly test and 

demonstrate vacuum cleaners as well as portable filters and their prototypes (whether as a single or 

separate units) in a relevant environment. 

5.4 Testing and Measurement 

Filters and filtration concepts for lunar dust should be tested in a relevant environment that simulates 

the conditions of the pressurized cabin in a lunar lander or habitat. Decisions have to be made about the 

testing and measurement methods that will be needed to assess the performance of lunar dust filters; in 

particular, about the testing protocols and standards (or modified standards) that should be followed. One 

should also consider how to use simulants that mimic the properties of lunar dust in a testing scenario. 

Some thought should also be given to the types of sensors needed—or that need to be developed—to 

monitor the performance and status of filtration systems. 

The prime objective for testing and associated measurement is to characterize and quantify the 

performance of selected filter technologies. However, some important details remain unresolved. For 

example, the filter efficiency targets have to be set. This is dictated by several performance variables such 

as flow rates, volume size to be cleaned, and acceptable cleanliness levels. These variables were discussed 

in preceding sections. Another important performance parameter is the allowable range of pressure drops 

across the filter element. Because the performance of filters depends on particle size and also because the 

toxicity of lunar dust is also size (or size range) dependent, a dosimetry metric(s) (performance vs. 

particle diameter) may be required. These performance variables translate into test parameters and impact 

the overall test matrix for any filter element. 
NASA/TM—2009-215821 21 

5.4.1 State-of-the-Art Technologies 

The industry standard for testing is the ASHRE 52.2 (Ref. 4), which provides a reasonable framework 

for what is envisioned to be needed. These standards, particularly within the last decade, reflect more 

recent advances in instrumentation, and increased attention to ultrafines. It was the assessment of the 

industry experts that Glenn’s measurement capabilities are current and adequate. NASA’s filter test 

facility is reasonably generic and appears suitable for the tasks at hand. 

The existing industry standards address the majority relevant issues. These include 

(1) Aerosol generation 

(2) Mixing 

(3) Sampling 

(4) Data interpretation 

(5) Data sufficiency 

The participants did not perceive any significant issues affecting test and measurement arising from 

(1) simulant versus regolith or (2) 1g versus 1/6g. 

5.4.2 Knowledge or Technology Gaps 

It was recognized that some knowledge gaps still exist regarding dispersal and transport in situ (i.e., 

What will the filters actually see?). Evolving requirements due to the ongoing lunar surface system 

development (Altair, lunar habitat) are also anticipated. Therefore it was questioned how good the filter 

needed to be in quantitative terms at this point. Although terrestrial testing is appropriate and useful, onorbit and in-transit assessment and performance validation is also important.

Regarding Glenn’s testing facility, it was recognized that certain test objects may not fit directly into 

our test facility. Other questions that arose were “What materials should we use for full-load efficiency 

tests?” and “What margins of excess are appropriate for each test parameter”? It was noted that lunar dust 

is not the only material the filters will see. There is generic dust composed of biological matter and 

degradation of material in the cabin, as well as larger debris—especially in transit (i.e., microgravity). 

Recommendations were given for procedural testing. Emphasis should be placed on challenge particle 

(particles used for filter testing) dispersion in the facility flow. There will be a need to verify uniformity 

and concentration from the challenge particle dispersion mechanism. Particularly, attention should be 

given to verify and calibrate all measurements, particularly at low pressure. In general, frequent zero 

count checks should be performed. These checks will help in assessing the extent and frequency of the 

cleaning of the facility that will be required. They may also aid in determining if cleaning methods as part 

of testing need to be improved or modified. The low pressure conditions should also be given special 

attention as it may affect other testing conditions or measurements. 

As a starting point, the tests should consist of replicating prior data for known reference filters at 

standard test conditions. The results should be compared with manufacturer’s performance data. The use 

of independent testing labs is advisable. Once verification is satisfied, one can proceed to lower pressure 

testing. It is emphasized that theory should guide data interpretation (data should make sense). The 

general attitude of “inherent skepticism” (Are my observations reasonable?) should be adopted. Also the 

role of other potential effects (e.g., humidity) should be investigated. 

5.5 Splinter Session Summary 

Each session contributed much insight on the particulate matter permissible limits, filter technology 

and design, and operational practices. It was felt that the particulate requirements still need to be firmed 

up, backed by relevant basic research. Also several assumptions need to be verified, in particular the lunar 

dust intrusion rate. A higher fidelity model of the intrusion rate will help better refine the expected 

airborne particulate concentration after an EVA. Estimates need to be derived for the weight and volume 
NASA/TM—2009-215821 22 

of filter systems, as well as for operational parameters such as power consumption, waste handling, crew 

involvement, and lastly cost. Methods for the safe removal, storage, and disposal of filter elements should 

be included in this assessment. Dust properties such as abrasiveness, particle cohesion, adhesion to walls, 

and effects of humidity were considered important. The consensus of the industry participants was that 

the current state-of-the-art technology is adequate to develop filtration systems for lunar surface systems. 

A multistage filtration concept was adopted, which included a prefiltration stage, an intermediate 

filtration stage if needed, and a final high-efficiency filtration stage. It was also their assessment that 

Glenn’s Lunar Dust Filtration Testing Facility appears adequate and appropriate for evaluation of 

developed filtration systems. The uniformity and concentration of dispersed challenge particles, 

calibration of instrumentation, and tests with known reference filters was deemed critical in filter testing. 

Several suggested research and technology areas included nanofiber filters using carbon nanotubes, 

electrospray particle charging, sintered metal and ceramic filters, three-stage filtration with an 

intermediate cyclone separator, and an airlock simulator for testing vacuum cleaning systems. 

Report Summary 

The 2.5-day NASA Lunar Dust Filtration and Separations Workshop was held in Cleveland, Ohio, 

in November 2008 to share requirements, technical knowledge and knowledge gaps, and research 

concepts for lunar dust filtration and separations technologies. There were a total of 32 participants. 

Roughly half were from industry or academia, and most had strong research and development credentials 

in filtration technologies. NASA participants included managers, researchers, and technologists from 

Glenn Research Center, Johnson Space Center, and Marshall Space Flight Center. The workshop featured 

19 presentations plus 4 splinter sessions to discuss concepts for future research. In the end, it was felt that 

the workshop met and even exceeded the intended goals. 
NASA/TM—2009-215821 23 

Appendix A 

Acronyms 

Below is a list of acronyms used in this report: 

ASAE American Society of Agricultural Engineers 

ASHRAE American Society of Heating, Refrigerating, and Air-Conditioning Engineers 

CFD computational fluid dynamics 

CFR Center for Filtration Research 

CFU colony-forming unit 

CNT carbon nanotube 

ECLSS environmental control and life support system 

ECS environmental control system 

ELS Exploration Life Support (project) 

EMU extravehicular mobility unit 

ETDP Exploration Technology Development Program 

EVA extravehicular activity 

HEPA high-efficiency particulate air 

HSIR Human-Systems Integration Requirements (document) 

HVAC heating, ventilation, and air conditioning 

ISS International Space Station 

JSC-1a Johnson Space Center Number 1a 

LADTAG Lunar Airborne Dust Toxicity Assessment Group 

LCG liquid cooling garment 

LEM lunar excursion module 

NU–LHT NASA/USGS-Lunar Highlands Type 

OPC optical particle counter 

OPS oxygen purge system 

PDR Preliminary Design Review 

PEL permissible exposure limit 

PIV particle image velocimetry 

PLSS portable life support systems 

PTFE polytetrafluoroethylene 

RGO Reduced Gravity Office 

SBIR Small Business Innovation Research 

SEM scanning electron microscopy 

SOA state of the art 

SRR System Readiness Review 

TMG thermal and micrometeoroid garment 

TPP Technology Prioritization Panel 

TRL technology readiness level 

ULPA ultra-low penetration air 

USGS United States Geological Survey 

NASA/TM—2009-215821 25 

Appendix B 

Workshop Attendees 

The names and affiliations of the NASA Lunar Dust Filtration and Separations Workshop (November 

2008) participants are provided below: 

1. Juan H. Agui NASA Glenn Research Center 

2. Buzz Aldrin StarBuzz Enterprises LLC 

3. Joseph J. Bango Connecticut Analytical Corp. 

4. Daniel Barta NASA Johnson Space Center 

5. Erin Brach ESCG Jacobs 

6. George G. Chase University of Akron 

7. Da-Ren Chen Washington University 

8. James R. Gaier NASA Glenn Research Center 

9. Eric L. Golliher NASA Glenn Research Center 

10. Paul S. Greenberg NASA Glenn Research Center 

11. Nancy R. Hall NASA Glenn Research Center 

12. James T. Hanley RTI International 

13. Edward W. Hodgson Hamilton Sundstrand Corp. 

14. Mark Hyatt NASA Glenn Research Center 

15. Beatrice M. Iliescu Seldon Technologies 

16. Noreen Khan-Mayberry NASA Johnson Space Center 

17. Jeffrey R. Mackey ASRC Aerospace Corp. 

18. Marit E. Meyer Washington University 

19. Brian J. Motil NASA Glenn Research Center 

20. Ernest S. Moyer Retired from NIOSH 

21. Scott Munson Orbital Technologies Corporation 

22. Masami Nakagawa Colorado School of Mines 

23. Jay L. Perry NASA Marshall Space Flight Center 

24. David Y.H. Pui University of Minnesota 

25. Henry A. Rotter, Jr. NASA Johnson Space Center 

26. Kenneth Rubow Mott Corporation 

27. Christian M. Schrader BAE Systems 

28. Dennis P. Stocker NASA Glenn Research Center 

29. Kenneth W. Street NASA Glenn Research Center 

30. Joel S. Tabb Agave BioSystems 

31. Katherine P. Toon NASA Johnson Space Center 

32. R. Vijayakumar AERFIL, LLC 

NASA/TM—2009-215821 27 

Appendix C 

Workshop Presentations 

Listed below are the titles and presenters for the NASA Lunar Dust Filtration and Separations Workshop 

(November 2008) presentations. The affiliations of the presenters can be found in Appendix A. 

I. Background (on the challenges of lunar dust and need for filtration and separations) 

• Programmatic Context for Spacecraft Cabin Lunar Dust Filtration and Separation Technology 

Development (Daniel Barta) 

• Cabin Atmosphere Quality Maintenance Background and Requirements: The Challenge of Lunar 

Dust Infiltration (Jay L. Perry) 

• Apollo Command Module Environmental Control System (ECS): Design for Dust and Lessons 

Learned (Henry A. Rotter, Jr.) 

• Lunar Dust Filtration in an Historical and Exploration Systems Design Context (Hodgson) 

• Lunar Dust 101 (James R. Gaier) 

• Lunar Dust Toxicity: Human Health Concerns (Noreen Khan-Mayberry) 

• Lunar Dust & Simulant Characterization Activity at GRC (Kenneth W. Street) 

II. Testing 

• Lunar Simulant Development and Characterization (Christian M. Schrader) 

• Lunar Dust Filtration Testing Facility (Juan H. Agui and Nancy R. Hall) 

• Air Cleaner Test Methods: Capabilities and Shortcomings (James T. Hanley) 

• Reduced Gravity Testing Capabilities (Nancy R. Hall) 

III. Technologies 

• A Multi-stage Axial Cyclone for Dust Separation (Da-Ren Chen) 

• Filter Media, and Test Practices (R. Vijayakumar) 

• Environmental Tractor Cabs, Pressurizers and Filters (Ernest S. Moyer) 

• Use of Sintered Metal Filters in Gas Filtration Applications (Kenneth Rubow) 

• Research Highlights of the Center for Filtration Research (CFR) at the University of Minnesota 

(David Y.H. Pui) 

• Lunar Dust Filtration Using Electrospray Gettering (Joseph J. Bango) 

• Application of a Fused Carbon Nanomaterial Filter for Lunar Dust Abatement 

(Beatrice M. Iliescu) 

• Developing Lunar Dust Simulants (Scott Munson) 

• Carbon Nanotube Based Electrostatic Filters for Micro- and Nanoparticulate Lunar Dust 

(Joel S. Tabb) 
NASA/TM—2009-215821 28 

References 

1. NASA Lunar Science Institute: Biological Effects of Lunar Dust Workshop. NASA Headquarters and 

NASA Ames Research Center, Sunnyvale, CA, 2005. 

2. Greenberg, Paul S.; Chen, Da-Ren; and Smith, Sally A.: Aerosol Measurements of the Fine and 

Ultrafine Particle Content of Lunar Regolith. NASA/TM—2007-214956, 2007. 

http://gltrs.grc.nasa.gov/ 

3. Dory, Jonathan: Constellation Program Human-Systems Integration Requirements; Final Report. 

NASA CxP 70024, 2006. 

4. Method of Testing General Ventilation Air Cleaning Devices for Removal Efficiency by Particle 

Size. ANSI/ASHRAE Standard 52.2–2007, 2007. 

http://www.ashrae.org/publications/detail/14891#52-2 Accessed November 13, 2009. 

5. British Standards Institution: High Efficiency Air Filters (HEPA and ULPA) Classification, 

Performance Testing, Marking. BS EN 1822–1:1998, 1998. 

http://shop.bsigroup.com/en/ProductDetail/?pid=000000000001386856 Accessed November 13, 

2009. 

6. Department of Defense Test Method Standard: Filter Units, Protective Clothing, Gas-Mask 

Components and Related Products: Performance Test Methods. MIL–STD–282, 1956. 

http://www.wbdg.org/ccb/FEDMIL/std282.pdf Accessed November 12, 2009. 
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14. ABSTRACT

NASA Glenn Research Center hosted a 2.5-day workshop, entitled “NASA Lunar Dust Filtration and Separations Workshop” at the Ohio 

Aerospace Institute in Cleveland, Ohio, on November 18 to 20, 2008. The purpose of the workshop was to address the issues and challenges 

of particulate matter removal from the cabin atmospheres in the Altair lunar lander, lunar habitats, and in pressurized rovers. The presence of 

lunar regolith dust inside the pressurized volumes was a theme of particular interest. The workshop provided an opportunity for NASA, 

industry experts, and academia to identify and discuss the capabilities of current and developing air and gas particulate matter filtration and 

separations technologies as they may apply to NASA’s needs. A goal of the workshop was to provide recommendations for strategic

research areas in cabin atmospheric particulate matter removal and disposal technologies that will advance and/or supplement the baseline 

approach for these future lunar surface exploration missions.

15. SUBJECT TERMS

Particulates; Filtration; Lunar dust; Cabin atmospheres; Altair lunar lander; Habitats 

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