Research Needs in Electrostatics for Lunar and Mars Space Missions

The new space exploratory vision announced by President Bush on January 14, 2004, initiated new activities at the National Science and Space Administration (NASA) for human space missions to further explore our solar system. NASA is undertaking Lunar exploration to support sustained human and robotic exploration of Mars and beyond. A series of robotic missions to the Moon by 2008 to prepare for human exploration as early as 2015 but no later than 2020 are anticipated. In a similar way, missions to the Moon and Mars are being planned in Europe, Japan and Russia. These space missions will require international participation to solve problems in a number of important technological areas where research is needed, including biomedical risk mitigation as well as life support and habitability on the surface of Mars. Mitigation of dust hazards is one of the most important problems to be resolved for both Lunar and Mars missions. Both Lunar and Martian regolith are unique materials and completely different from the terrestrial soils that we are exposed to on earth. The total absence of water and an atmosphere on the moon and the formation of soil and fine dust by micrometeorite impacts over billions of years resulted in a layer of soil with unique properties. The soil is primarily basaltic in composition with a high glass concentration. The depth of the soil layer varies from a few meters in the mare areas (dark areas on the Lunar near side) to tens of meters in the highland areas (the lighter mountainous areas) and the particle size distribution of this dust layer varies widely with a major mass fraction less than 10 micrometer in diameter. The hard soil from the moon which has been extensively studied by several researchers showed clearly unique properties of Lunar soil. Apollo astronauts became aware of the potentially serious threat to crew health and mission hardware that can be caused by the lunar dust. As reported by McKay and Carrier the mass fraction of the lunar dust with particle diameter smaller than 20p.m probably represents up to 30% of the total mass of regolith. Apollo astronaut Dr. Harrison Schmidt reported that these fine dust particles were clinging to the Extra Vehicular Activity (EVA) suits and to the visors and were limiting the activity on the surface of the moon. The dust particles that were transported with the EVA suits into the lunar module floated throughout the cabin. Crews inhaled the dust particles and noted that they smelled like gun smoke, caused a chocking sensation in the throat and eye irritation. In addition,, some of the mechanical systems were not functioning well because of the dust deposition. It appeared that the dust particles are highly charged electrostatically and Dr. Schmidt noted that future successful Lunar missions will require appropriate dust mitigation technology for protecting astronauts from inhaling toxic particles and mission's life supporting equipment from contamination with the dust particles

The Electrostatic Environments of Mars and the Moon

The electrical activity present in the environment near the surfaces of Mars and the moon has very different origins and presents a challenge to manned and robotic planetary exploration missions. Mars is covered with a layer of dust that has been redistributed throughout the entire planet by global dust storms. Dust, levitated by these storms as well as by the frequent dust devils, is expected to be electrostatically charged due to the multiple grain collisions in the dust-laden atmosphere. Dust covering the surface of the moon is expected to be electrostatically charged due to the solar wind, cosmic rays, and the solar radiation itself through the photoelectric effect. Electrostatically charged dust has a large tendency to adhere to surfaces. NASA's Mars exploration rovers have shown that atmospheric dust falling on solar panels can decrease their efficiency to the point of rendering the rover unusable. And as the Apollo missions to the moon showed, lunar dust adhesion can hinder manned and unmanned lunar exploration activities. Taking advantage of the electrical activity on both planetary system bodies, dust removal technologies are now being developed that use electrostatic and dielectrophoretic forces to produce controlled dust motion. This paper presents a short review of the theoretical and semiempirical models that have been developed for the lunar and Martian electrical environments

Flexible Graphene-based Energy Storage Devices for Space Application Project

Develop prototype graphene-based reversible energy storage devices that are flexible, thin, lightweight, durable, and that can be easily attached to spacesuits, rovers, landers, and equipment used in space

Electrostatic Evaluation of the ARES I FTS Antenna Materials

Surface resistivity and volume resistivity data show all the tested non-metallic materials of the Ares I FTS antenna assembly to be insulative. The external materials (White foam, phenolic) should be able to develop a large surface charge density upon tribocharging with ice crystal impingement. Dielectric breakdown tests on the FTS antenna housing materials show that each of the insulative materials are very resistive to electrical breakdown. The thicknesses of these materials in a nominal housing should protect the antenna from direct breakdown from external triboelectric charging potentials. Per data from the Air Force study, a maximum external electric potential in the range of 100kV can be developed on surfaces tribocharged by ice crystal impingement. Testing showed that under operational pressure ranges, this level of exterior voltage can result in a potential of about 6 kV induced on the electrically floating interior antenna vanes. Testing the vanes up to this voltage level showed that electrostatic discharges can occur between the electrically floating vanes and the center, grounded screw heads. Repeated tests with multiple invisible and visible discharges caused only superficial physical damage to the vanes. Fourier analysis of the discharge signals showed that the frequency range of credible discharges would not interfere with the nominal operation of the FTS antenna. However, due to the limited scope, short timetable, and limited funding of this study, a direct measurement of the triboelectric charge that could be generated on the Ares I antenna housing when the rocket traverses an ice cloud at supersonic speeds was not performed. Instead, data for the limited Air Force study [3] was used as input for our experiments. The Air Force data used was not collected with a sensor located to provide us with the best approximation at the geometry of the Ares I rocket, namely that of the windshield electrometer, because brush discharges to the metal frame of the windshield periodically depleted any charge accumulated. The configuration of the Ares I antenna assembly does not include any exposed metals in the vicinity and the windshield data could not be used. Since the windshield sensor data was unusable, we decided that the Patch 2 location would provide us with a rough approximation to the Ares I antenna configuration and would give us an indication of the possible charging levels that would develop. This was the data that we used in this study. Whether these charging levels would be of the same order of magnitude as the actual charges developed by the Ares I traversing a cloud with ice particles is at this point unknown. An actual experimental test, requiring the acquisition of additional instrumentation, is strongly advised before a final recommendation can be formulated regarding the safe levels of electrostatic charging on the antenna housing. Thus the results of this study should be considered to be preliminary

Transparent Conveyor of Dielectric Liquids or Particles

The concept of a transparent conveyor of small loose dielectric parti cles or small amounts of dielectric liquids has emerged as an outgro wth of an effort to develop efficient, reliable means of automated re moval of dust from solar cells and from windows of optical instrumen ts. This concept is based on the previously reported concept of an e lectrodynamic screen, according to which a grid-like electric field is established on and near a surface and is moved along the surface p erpendicularly to the grid lines. The resulting electrodynamic force s on loose dielectric particles or dielectric liquid drops in the vic inity would move the particles or drops along the surface. In the or iginal dust-removal application, dust particles would thus be swept out of the affected window area. Other potential applications may occ ur in nanotechnology -- for example, involving mixing of two or more fluids and/or nanoscale particles under optical illumination and/or optical observation

Nearly Direct Measurement of Relative Permittivity

A recently conceived technique for determining the relative permittivity of a material sample at a given frequency is more nearly direct than are prior techniques that involve measurement of such related non-electrical quantities as the size, shape, and/or weight of the specimen. The present technique involves only measurement of two voltages at the frequency in question, followed by calculation of the ratio between the voltages. The technique requires two circuits a test circuit and a reference circuit that are identical except as described below. Each circuit includes a capacitor C1 connected in series with a much larger capacitor C2 to form a voltage divider (see figure). C1 is a parallel-plate capacitor. The top electrode of C1 is connected to an AC signal source of voltage Va at the frequency of interest. The top electrode of C1 is surrounded by a guard electrode that, in turn, is surrounded by a grounded electrode. The bottom electrode of C1 is connected to the top electrode of C2. The bottom electrode of C2 is grounded. The volume enclosed by the top, bottom, and guard electrodes of C1 constitutes a sample cell. A material sample, having relative permittivity k at the frequency of interest, is placed in the sample cell. The exact shape and size of the sample volume is not critical and can be chosen to fit the material sample. What is critical is that (a) C2 in both circuits be identical and (b) the sample cell in the test circuit have the same size and shape as that in the reference circuit, so that the capacitances of the two sample cells are proportional to the permittivities of their contents

Application of Glow Discharge Plasma to Alter Surface Properties of Materials

Some polymer materials that are considered important for spaceport operations are rendered noncompliant when subjected to the Kennedy Space Center (KSC) Standard electrostatic testing. These materials operate in stringent environmental conditions, such as high humidity. Treating materials that fail electrostatic testing and altering their surface properties so that they become compliant would result in considerable cost savings. Significant improvement in electrostatic dissipation of Saf-T-Vu PVC after treatment with air Atmospheric Plasma Glow Discharge (APGD) was observed and the material now passed the KSC electrostatic test. The O:C ratio on the surface, as monitored by X-ray Photoelectron Spectroscopy, increased from 0.165 tO 0.275 indicating enhanced oxidation, and surface contact angle measurements decreased from 107.5 to 72.6 showing increased hydrophilicity that accounted for the increased conductivity. Monitoring of the aging showed that the materials hydrophobic recovery resulted in it failing the electrostatic test 30 hours after treatment. This was probably due to the out-diffusion of the added Zn, Ba, and Cd salt stabilizers detected on the surface and/or diffusion of low molecular weight oligomers. On going work includes improving the long term hydrophilicity by optimizing the APGD process with different gas mixtures. Treatment of other spaceport materials is also presented

Electrostatic Evaluation of the Propellant Handlers Ensemble

The Self-Contained Atmospheric Protective Ensemble (SCAPE) used in propellant handling at NASA's Kennedy Space Center (KSC) has recently completed a series of tests to determine its electrostatic properties of the coverall fabric used in the Propellant Handlers Ensemble (PHE). Understanding these electrostatic properties are fundamental to ensuring safe operations when working with flammable rocket propellants such as hydrazine, methyl hydrazine, and unsymmetrical dimethyl hydrazine. These tests include surface resistivity, charge decay, triboelectric charging, and flame incendivity. In this presentation, we will discuss the results of these tests on the current PHE as well as new fabrics and materials being evaluated for the next generation of PHE

NASA Mars 2020 Rover Mission: New Frontiers in Science

The Mars 2020 rover mission is the next step in NASAs robotic exploration of the red planet. The rover, based on the Mars Science Laboratory Curiosity rover now on Mars, will address key questions about the potential for life on Mars. The mission would also provide opportunities to gather knowledge and demonstrate technologies that address the challenges of future human expeditions to Mars.Like the Mars Science Laboratory rover, which has been exploring Mars since 2012, the Mars 2020 spacecraft will use a guided entry, descent, and landing system which includes a parachute, descent vehicle, and, during the provides the ability to land a very large, heavy rover on the surface of Mars in a more precise landing area. The Mars 2020 mission is designed to accomplish several high-priority planetary science goals and will be an important step toward meeting NASAs challenge to send humans to Mars in the 2030s. The mission will conduct geological assessments of the rover's landing site, determine the habitability of the environment, search for signs of ancient Martian life, and assess natural resources and hazards for future human explorers. The science instruments aboard the rover also will enable scientists to identify and select a collection of rock and soil samples that will be stored for potential return to Earth in the future. The rover also may help designers of a human expedition understand the hazards posed by Martian dust and demonstrate how to collect carbon dioxide from the atmosphere, which could be a valuable resource for producing oxygen and rocket fuel

New NASA Technologies for Space Exploration

NASA is developing new technologies to enable planetary exploration. NASA's Space Launch System is an advance vehicle for exploration beyond LEO. Robotic explorers like the Mars Science Laboratory are exploring Mars, making discoveries that will make possible the future human exploration of the planet. In this presentation, we report on technologies being developed at NASA KSC for planetary exploration