# Presentation: 170596

## Is lunar dust really a problem? 

- Bill Farrell
- Code 695

## Apollo Experience

*“**I think dust is probably one of our greatest inhibitors to a nominal operation on the Moon.  I think we can overcome other physiological or physical or mechanical problems except dust.”*
- 								*Gene Cernan*
*	**	**	**	**	**	**	**	**Apollo 17 Technical Debrief*

## The Apollo Experience : Lessons Learned for Constellation Lunar Dust Managementby Wagner 2006 

- Primary Source: Dust was brought into the Lunar Module during ingress after EVA.
- Lunar Module dust, dirt and debris contamination presented numerous challenges for several of the Apollo missions.
- The Apollo 12 crew observed that at 1/6-g the cabin atmosphere was excellent, however, after orbital insertion lunar dust filled the atmosphere and caused eye and nose irritation.
- The Apollo 14 crew observed little dust in the LM and cited no dust related problems.
-  The floor of the Apollo 15 LM was dirty.
- The Apollo 16 crew appears to have had the most difficulty with dust, citing the following: Velcro on the floor was caked with dust; crew feet, hands and arms were covered with dust that was transferred into the suit upon donning; the midstep was covered with dust; eye and mouth irritation; and, the cabin fan in zero-g did not appear to clean the atmosphere.
- The crew of Apollo 17 cited sinus and nostril irritation after EVAs, however, observed good cabin cleaning and atmosphere in 1/6-g.

## What do we really know about  lunar dust (D. McKay/JSC-NESC talk)

- Dust defined as particulates < 20 um [NESC conf, Jan 07]
- Considered “sharp” and “jagged” - lack of meteorological weathering
- Not immediately toxic – but long term exposure MAY lead to silicosis-like diseases (Hawk Nest Tunnel/auto-immune response)
- Agglutinates: micrometeroid-melted glasses with embedded sand and rocks (% used to derive age of region)
- The most chemically-potent grains may in the form of small spherical balls of reduced iron < 1 um (nanoparticles)

## Lunar Dust Movement

- Some fraction of the lunar dust moves
- Surface charged positive from photoemission on  dayside
- Charge negative from plasma currents on nightside
- Like-charged grains can then be levitated/lofted
- Creates a dusty-plasma
- Surveyor images (horizon glow)
- CM observations of light-scattered dust (glow and streamers) – Cernan sketches
- Up to 100 km near terminators

- Surveyor 6
- Image

- McCoy, 1976

## Stubbs et al. 2006

- Prior to 2006, static dust
- levitation in near-surface
- E-field considered only
- -Stubbs et al. demonstrated that
- Near-surface E-field can loft
- particles
- -Dynamic dust fountain model
- qE  > mg
- -In models, small grains can
- Get lofted to many 10s of km
- -Explain the CM observations of
- streamers

## Terminator High Energy “Dusty Sleet”

- Highly accelerated (100s of m/sec) dust has also been detected in this complicated terminator region by GSFC’s Apollo 17’s Lunar Ejecta and Meteorites surface package [Berg et al., 1976]
- Dusty Sleet – An EVA hazard?
- 1 Event per 2 minutes detected by LEAM
- Component especially relevant at Shackleton crater region
- Possibly related to large wake-related E-fields at the terminator [Farrell et al, 2007]

- [Farrell et al., 2007]

## Anthropogenically lifted Dust 

- The astronaut, moving equipment, and the dust will create and exchange  charged via contact electrification – triboelectricity
- The tribo-charged astronaut and tribo-charged dust grains will then experience increased attraction to each other.
- Dust adheres to space suit, carry into habitat
- Of concern to ESMD

## Nature of Dust Hazards

- Human Exposure –ranging from acute silicosis to skin irritation
- Degradation/destruction of life support systems- space suit connectors, air lock, filtration sys
- Degradation to flight systems – DL phase
- Degradation to deployed mechanical systems – bearings, gears, seals, lubricant usage
-  Degradation to science instrumentation – telescopic sensitivity

- Anomalous failures may be more important in determining exposure
- than nominal operations (Jeff Jones, NESC conf, Jan 2007)

## Who Cares About Dust? Wow! 

- Cx
- LADTAG
- ETDP
- NESC
- LPRP
- SMD
- NAC
- NAS

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- Technical concerns/application
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- Science at the moon
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- Centers also thinks that dust is of interest – each has some expertise
- Managing the managing groups is a problem unto itself

- Many concerned parties
-  for “the dust
- problem”..all have:
- differing stakes
- differing reasons to be interested
- differing interest in components

**Notes:**
Is the moon a good observatory? – NAS recommendations
Groups want to own dust problem, but if solved, solution wont help other group’s issues. 

## Constellation Program (CxP)

- CxP responsible for lunar flight system – human exposure, life support, flight system, mech sys
- Late Nov 06 meeting CxP Adv. Projects Office (Carlos Noriega)
- Don’t think dust is a “show-stopper”
- CxP antes in with an airlock at the LSAM entrance – vastly reduce dust in habitat
- Believes simple mitigation required for other systems...Brushes, felt on seals, cover alls
- In essence, CxP will spend $1-2B via airlock.

- Suit lock

- Primary Consumer!

## Lunar Airborne Dust Toxicity Advisory Group (LADTAG)

- Group that examined the acceptable dust load to keep shirt sleeve environment safe for astronauts
- Defined requirement of interior dust load of for < 10 um sized contaminants of LADTAG ~0.05 mg/m3 in the internal atmosphere
- Comparable to about 109 grains of 1 um in size in a ~ 300 m3 volume
- This load is now part of the  CxP Level II requirement
- Very conservative number relative to OSHA standard with OSHA~ 5-10 mg/m3 for non-silica
- Places a requirement on the CxP’s airlock system
- GSFC team demonstrated that the Apollo LEM dust load could easily have exceeded LADTAG standard by factor of ~100
- Apollo - Removal of dusty space suit within internal atmosphere very problematic!
- The LSAM air lock (donn suits in isolation)...reduce exposure, creates safe haven!

## Exploration Technology Development Program (ETDP)

- Parallel effort in ESMD to develop technologies for use in CxP...20 different target areas (thermal, comm)
- ETDP has $367M FY07, $2.7M for dust mitigation
- Currently incubating a number of technologies for dust mitigation both externally & in the air lock
- GSFC: System approach – look at ETDP mitigation technology in tandem with Cx’s airlock/dust isolation system

## Dust Entry Probability into the Lunar Surface Access Module (LSAM)Farrell, Stubbs, Vondrak 

- Nast(1-PLext) (T PLint ) < Nladtag
- Nast ~ 1013 grains – astronaut falls, covered 1um grains (peak PSD on suit a few microns)
- Apollo: T =1, Nast(1-0.5) (T *0.1 ) ~ 1012 which exceeds Nladtag ~ 108-9
- LSAM: airlock - T ~ 10-4, Nast(1-0.5) (T *0.1 ) ~ 108, less than Nladtag ~ 109
- So if airlock can create isolated environment for suit removal, may not need complicated external dust removal systems (ETDP)

## NASA Engineering Safety Center (NESC)

- After Columbia accident, NASA established in-house but independent safety center to assess safety of high-risk projects
- Oversight group.... independent to CxP
- NESC has identified lunar dust as a possible safety issue
- Ran a 3-day meeting in Jan 07 with 150 invited participants to identify possible hazards in 4 subject areas: Basic environment, mechanical systems, life support systems, human health
- Many issues raised...
-  The report still not released

## Science Mission Directorate 

- Focus on naturally
- lofted component

## National Academy of Science  The Scientific Context for Exploration of the Moon:Interim Report(2007)

- Understand processes involved with the atmosphere (exosphere) of airless bodies in the
-  	inner solar system.
- 		– Moon has a dusty plasma/neutral exosphere, driven from surface
- Determine the utility of the Moon for astrophysics observations
- –Dust obscuration
- Determine the utility of the Moon as a platform for observations of Earth.
- 		–Dust obscuration
- Determine the utility of the Moon as a platform for observations of solar-terrestrial
-  	processes.
- 		-Surface E-fields and moon-altered plasma affects
- 		-Dust obscuration

- Focus on naturally lofted component

## Conclusion

- Question: Is  lunar dust a problem?
- Yea! But it may be both a technical and sociological science problem
- Managing the divergent groups with oblique interests and identifying what is relevant to CxP and what is relevant to science...and who owns what risk.
- CxP- anted in the most $$ for dust mitigation with airlock system
- Should reduce internal dust load and susceptibility to silicosis-like symptoms.....vastly improve upon Apollo situation and could reach LADTAG load
- However, ETDP and NESC believes external dust hazards to life supp and mech sys may be greater than perceived....interesting dynamics: CxP, ETDP, & NESC
- New Question: Is a good air lock and a “safe place” from dust good enough? It will vastly reduce human exposure and protect internal life support systems...
- The science areas have a different take on dust focusing on natural components and the environment
- SMD wants to understand the basics of dusty plasmas and exosphere at the moon –part of their roadmap
- NAS wonders if the moon is a good observatory site or whether dust obscuration will limit the use of telescopes

## Our Future Lunar Astronaut?

- -The most healthy person
- may have the most severe
- auto-immune response to inhaled small dust...you
- want to be a little “unhealthy”
- -Jeff Spicoli’s lungs already exposed to numerous small
- particulates of questionable
- composition

- “Sure Dude...Ill go!”