Influence of back electrostatic field on collection … particles fall down eventually due to lunar...

Levitated particles fall down eventually due to lunar gravity anddeposit on the exposed solar panels, lenses, etc.

Influence of back electrostatic field on collection efficiency of an electrostatic lunar dust collector1 Engineering School of Sustainable Infrastructure and Environment, University of Florida, Gainesville, FL, USA

2 Florida Solar Energy Center, University of Central Florida, Cocoa, FL, USAMotivation & Introduction

Nima Afshar-Mohajer1, Yatit Thakker1, Chang-Yu Wu1, Nicoleta S-Hickman2

҉ Increasing the applied voltage delays the observed deterioration inELDC performance (10 V vs. 5 V).

҉ There would be a peak in penetration graphs. The back e‐fieldstrengthens with time and prevents particles from not onlycollection but also penetration. This forms a cloud of particles andprevents both ELDC and solar panel from proper functioning.

҉ Suspension increases with time and its rate increases drastically at400/cm2 with ΔV = 5 V and at 550/cm2 with ΔV = 10 V.

http://www.nasa.gov/

References

Acknowledgement

1) Afshar‐Mohajer, N., 2011. Advances in Space Res, Vol. 48, No. 5, pp. 933‐942.2) Afshar‐Mohajer, N., 2012. J. of Appl. Phys., Vol. 112, No. 2, 0233053) Stubbs et al., 2006. Advances in space research, vol. 37, pp. 59‐66.4) Reitan, D. K., 1959. J. of Appl. Phys., Vol. 30, No. 2, pp. 172‐176.

Apollo 17 lunar dustPark et al., (2007)

http://www.cbc.ca/news

Effects of lunar dust deposition:1) Dimness of optical surfaces2) Damaging costly and sensitive equipment3) Deterioration of solar panel performance

The authors are thankful to the Space Research Initiative by the State ofFlorida (Grant No. 20040028). We appreciate all supports from SenthilArumugam and Dr. Curry, & DEM‐Solution Inc. for providing EDEM access.

Conclusions

Accumulation of solar‐based charges on thelunar regolith and repelling actions among thelike‐charged particles results in levitation of the particles metersaway from the lunar surface.

DEM modeling҉ For such a particulate system requiring electrostatic fieldcalculations, EDEM 2.4.2 (academic license) developed by DEM‐Solution Inc. was adopted.

in lunar environment is challenging, this research is embarked tostudy the effect of back e‐field due to the deposited chargedparticles on the ELDC’s efficiency.The objective of study is to optimizes ELDC utilization by findingthe best combination of the applied voltage and timing of platecleaning.

In hard vacuum condition ofthe lunar environment, theElectrostatic Lunar DustCollector (ELDC) wasdemonstrated to be a highlyefficient device to protect thesurfaces from the naturallycharged lunar dust.1, 2

However, collection efficiencyreduces with time because ofthe deposited chargedparticles on the ELDC plates.Since cleaning the ELDC plate

Particlediameter

20 µm (all)

Particle charge

1.11 × 10‐13 C

Particle Initial velocity

1.309 m/s

Time‐Step = 20% TR

1.76 × 10‐7 s

E‐field screening distance

10 mm

Particle concentration

Varying

Input data

҉ It was shown thatcollection efficiencyincreases linearly withthe applied voltage.1

҉ The e‐field isexerted by pointcharges assigned atthe center of sub‐plates (qi). The samee‐field applies to thesame set of chargesand this was kept asthe same within theentire simulations .

Results

ΔV = 5 V

ΔV = 5 V

ΔV = 5 V

ΔV = 10 V

ΔV = 10 V

ΔV = 10 V

҉ The following equation relates ELDC geometry to the applied voltage:Σqi = (ε0× A/D) × ΔV҉ Sensitivity analyses were conducted on both concentration of theincoming particles and density of the previously deposited particles.

҉Input data was extracted from the pertinent literature.3(a) Clean ELDC plate (b) Dirty ELDC plate

Factory for incoming Lunar dust Eddies due 

to back e‐field effect

Factoryfor

alreadyCollected

dust

No eddies

Two simulations in the presence and absence of previously lunar dust at thesame time‐step (the only difference is having 1600 #/cm2 at case (b))

Non‐Uniform e‐field → MATLAB 7.10 CodeAnalyzing EDEM output logs → Visual Basic code

Schematic of the ELDC operation