Martian and Lunar Environment Test Apparatus Nicholas Vachon September 30, 2008

Topics Particle Characteristics Atmospheric Characteristics Experimental Chamber Next Steps

Particle Characteristics Martian Particles – Interested in mitigating particles ranging from µm – Chemical Composition

Particle Characteristics Martian Particles – Charged Particles Triboelectric charging Experiments with Martian regolith simulant have shown that triboelectric charging can reach potentials of + 10V. (Fibian et al. 2001)

Particle Characteristics Lunar Particles – Interested in mitigating particles ranging from µm – Chemical Composition

Particle Characteristics Lunar Particles – Charged Particles – C – Positive on the day-side Solar ultraviolet photons cause photoelectrons to be released from hydrogen rich compounds present in lunar regolith. – Negative on the night-side The flux of electrons form the solar wind is much higher than the corresponding flux of ions, resulting in a negative charge. (Hyatt et al. 2007)

Atmospheric Characteristics Martian Atmosphere – Chemical Composition

Atmospheric Characteristics Martian Atmosphere – Mean surface level pressure is 600 Pa (0.6 kPa) – About 0.7 percent of Earth’s atmosphere – Acoustic Characteristics The absorption of mid-level frequencies (500Hz) occurs times faster than on Earth. (Bass et al. 2001)

Atmospheric Characteristics Lunar Atmosphere – Chemical Composition – Approximately one trillionth the density of the Earth's atmosphere. (Stern et al. 1999)

Experimental Chamber Low Operating Pressure Vacuum pump – Martian » Will purge with CO2, before pressure is reduced. » CO2 alone may be sufficient for testing. – Lunar » The lowest pressure obtainable by the vacuum pump may be sufficient to reproduce the lunar environment. » KPa would be appropriate to match similar experiments Pressure vessel – Housing and all interfacing components will have to maintain a vacuum.

Experimental Chamber Low Operating Humidity Bottled gas such as CO2 should provide a low humidity environment. If needed, a desiccant may be used to lower the humidity further.

Experimental Chamber Control of Dust Particle Size Regolith stimulants are available. JSC Mars-1 Martian Regolith simulant has been used by others in charged particle experiments. (Fjbian et al. 2001) JSC -1 lunar Regolith simulant (McKay et al ) Target size nm Sieving may be required to obtain the target particle size.

Experimental Chamber Control of Dust Particle Size Martian Simulant Comparison (Allen, C et al.)

Experimental Chamber Control of Dust Particle Size Lunar Simulant Comparison (McKay et al. 1994)

Experimental Chamber Control of Particle Charge One of the more difficult aspects of the project. Nanoparticles are difficult to charge due to there small cross section. Ion-attachment method & photo-ionization method are two main processes used to charge particles. – Ion-attachment method uses field or diffusion charging processes to attach ions to particles. – Photo-ionization method uses photons emitted form UV light to ionize particles. » The charging efficiency strongly depends on particle compositions. » Photo-ionization is hard to implement due to free electrons recombining with positive particles. » Impurities in the carrier gas become ionized causing charging efficiencies to be unpredictable. – Ion-attachment method is less dependant on particle compositions and has a stable charging efficiency. (Chen et al. 1999)

Experimental Chamber Control of Particle Charge Unipolar and Bipolar Photo-ionization particle chargers are available. – Bipolar charges are more commonly used but have very low charging efficiencies on nanoparticles. – Unipolar chargers are well suited for nanoparticles – The aerosol used to carry the particles might contaminate the atmosphere simulated in the test chamber. (Chen et al. 1999) The use of a radioactive source to strip electrons from particles may be the best alternative.

Experimental Chamber Integration with Measurement Instrumentation – The test chamber must interface with the Micro PIV system. Integration with Dust Mitigation apparatus – Power and control circuits will have to interface through the test chamber. Integration with sensing/control Instrumentation

Next Steps – Create initial design of Test chamber and experimental apparatus. – Gather information about required electrical interfaces. – Determine if a circulating or stagnant environment is required. – Source components (vacuum pump, particle charger, pressure vessel, …)

References 1. S. Alan Stern (1999). "The Lunar atmosphere: History, status, current problems, and context". Rev. Geophys. 37 (4): 453– Bass, Henry; Chambers, James. “Absorption of sound in the Martian atmosphere”, J. Acoustic. Soc. Am., Vol. 109, No. 5, Pt. 2, May Fjbian, Krauss, Sickafoose, Horjnyi, Robertson. “Measurements of Electrical Discharges in Martian Regolith Simulant”, IEEE TRANSACTIONS ON PLASMA SCIENCE, VOI. 29. NO. 2. APRIL Allen, C.C. et al. “JSC MARS-1: MARTIAN REGOLITH SIMULANT”. Lunar and Planetary Science XXVIII 5. McKay, David S. et al. “JSC-1: A NEW LUNAR SOIL SIMULANT”. Engineering, Construction, and Operations in Space IV, American Society of Civil Engineers, pp , Chen, Da Ren; Pui, David Y. H. “A high efficiency, high throughput unipolar aerosol charger for nanoparticles”. Journal of Nanoparticle Research 1: , Hyatt, Mark et al. “Lunar and Martian Dust: Evaluation and Mitigation”. 45 th AIAA Aerospace Sciences Meeting and Exhibit 8-11 January 2007, Reno, Nevada. 8. Stern, Alan et al. “THE LUNAR ATMOSPHERE: HISTORY, STATUS, CURRENT PROBLEMS, AND CONTEXT” Reviews of Geophysics 3, 7, 4 / November 1999 pages