Is lunar dust really a problem?

1. Is lunar dust really a problem? Bill Farrell Code 695

2. “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 Apollo Experience

3. The Apollo Experience : Lessons Learned for Constellation Lunar Dust Managementby 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.

4. 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)

5. 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 Lunar Dust Movement Surveyor 6 Image McCoy, 1976

6. 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 Stubbs et al. 2006

7. 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] Accelerated dust impacts detected by Apollo 17 surface package (from Berg et al., 1976). Terminator High Energy “Dusty Sleet” [Farrell et al., 2007]

8. 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 Anthropogenically lifted Dust

9. 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 Nature of Dust Hazards • Anomalous failures may be more important in determining exposure • than nominal operations (Jeff Jones, NESC conf, Jan 2007)

10. Who Cares About Dust? Wow! ---- Technical concerns/application ^ | | | | | | | | | | v Science at the moon ---- Cx LADTAG ETDP NESC LPRP SMD NAC NAS • Many concerned parties • for “the dust • problem”..all have: • differing stakes • differing reasons to be interested • differing interest in components • Centers also thinks that dust is of interest – each has some expertise • Managing the managing groups is a problem unto itself

11. 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. Constellation Program (CxP) Suit lock Primary Consumer!

12. 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 rLADTAG ~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 rOSHA~ 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!

13. 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 Exploration Technology Development Program (ETDP)

14. 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)

15. 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

16. Science Mission Directorate Focus on naturally lofted component

17. 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

18. 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 vastlyreduce 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

19. 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!”