Characterization of Lunar Dust for Toxicological Studies. II: Texture and Shape Characteristics

The morphology (shape and texture) of dust fractions of five Apollo lunar soils and a lunar dust simulant, JSC-1Avf, was studied using scanning electron microscopy. Shape (aspect ratio and complexity) of particles was described based on the two-dimensional projection images. The distributions of aspect ratio and complexity of particles are reported. It was determined that the Apollo lunar dust particles consist mainly of impact-produced glass, with complicated morphologies, extensive surface areas per grain, and sharp, jagged edges. Importantly, many grains contain elaborate vesicular textures, representing minute agglutinates. Dust simulant JSC-1Avf also has similar shapes as lunar dust, but differs in surface texture and area (smooth and nonvesicular). These data provide information for toxicity studies of lunar dust and for selecting a suitable lunar dust simulant.     

Some Comments on the Protection of Lunar Habitats against Damage from Meteoroid Impacts

The establishment of human habitats on the Moon and on Mars will require protecting them from the hazards of near-Earth and interplanetary space. In addition to solar radiation, another hazard to be faced by these habitats is the damage that can result from the high speed impact of a meteoroid on a critical structural component. Therefore, lunar habitats and their accompanying support facilities need to be designed with adequate levels of protection that will allow them to also withstand the damage that can result from a meteoroid impact. In this paper we discuss some approaches to shielding for lunar habitats, focusing on shielding that is intended primarily to provide protection against meteoroid impacts and on shielding approaches that use resources mined or extracted from the Moon. The Moon’s mineralogy is discussed and suggestions are presented for materials and material combinations that can be used to develop shielding for lunar habitats and which are comprised primarily or entirely of lunar materials. Several shielding mechanisms are also presented that could be effective against impacts by meteoroid particles having diameters on the order of that which are likely to strike a fairly large lunar habitat at least one or two times per year. The paper concludes with recommendations for continuing work in optimizing the design of meteoroid shielding for lunar habitats.     

Technical Requirements for Lunar Structures

The moon has recently regained the interest of many of the world’s space agencies. Lunar missions are the first steps in expanding manned and unmanned exploration inside our solar system. The moon represents various options; it can be used as a laboratory in low gravity, it is the closest and most accessible planetary object from the Earth, and it possesses many resources that humans could potentially exploit. This paper has two objectives: to review the current status of the knowledge of lunar environmental requirements for future lunar structures, and to attempt to classify different future lunar structures based on the current knowledge of the subject. The paper divides lunar development into three phases. The first phase is building shelters for equipment only; in the second phase, small temporary habitats will be built, and finally in the third phase, habitable lunar bases will be built with observatories, laboratories, or production plants. Initially, the main aspects of the lunar environment that will cause concerns will be lunar dust and meteoroids, and later will include effects due to the vacuum environment, lunar gravity, radiation, a rapid change of temperature, and the length of the lunar day. This paper presents a classification of technical requirements based on the current knowledge of these factors, and their importance in each of the phases of construction. It gives recommendations for future research in relation to the development of conceptual plans for lunar structures, and for the evolution of a lunar construction code to direct these structural designs. Some examples are presented along with the current status of the bibliography of the subject.     

Progression of permanent atrial fibrillation after atrioventricular junction ablation and dual-chamber pacemaker implantation in patients with paroxysmal atrial tachyarrhythmias

Control of the house dust mite allergen has received considerable attention owing to its importance in some allergic diseases. One aspect of dust mites and their allergen-carrying faecal particles that has not been reported on, which may have allergen control applications, is the electrostatic charge they carry in the natural environment. To promote tribo-electric charging, household dust containing dust mite allergen and live house dust mites are separately agitated while in contact with either polypropylene, nylon or earthed metal. The charged dust and mites are subsequently subjected to electrostatic separation and collection. Results for concentrations of the house dust mite allergen, Der p1, indicate that, when subjected to nylon, Der p1 carrier particles appear to be predominantly positively charged. Similarly, when subjected to polypropylene, Der p1 carrier particles also appear to be positively charged. Reduction of excess free charge by agitation against earthed metal does not appear to affect the observed charging characteristics, indicating that the positive charge may be bound or inherent in the Der p1 carrier particles. In contrast, house dust mites exposed to nylon appear to be generally charging negative, whereas mites exposed to polypropylene appear to be charging positive. The observed electrostatic characteristics of the mites and Der p1 carrying particles will be useful in the future development of electrostatic allergen control methods.     

电除尘电场不闪络的原因分析

研究电除尘器整流设备控制过程及电场内部粉尘粒子荷电情况,有助于设备维护及改造,改善并提高除尘器的效率。     

Design and Construction of Shielded Lunar Outpost

The construction of an outpost on the Moon in which humans can live and work for periods exceeding six months will require special countermeasures to adapt to the hostile environment present at the lunar surface. Various inherent dangers such as meteoroids, galactic cosmic radiation, solar proton events, and large thermal extremes will drive the design configuration of the outpost. Other considerations such as lunar soil mechanics, equipment performance, mass delivery, risk, reliability, and tele‐operability act strongly as constraints that shape and control the design alternatives. Analysis of these fundamental relationships have resulted in lunar civil engineering guidelines, which are unique to this domain, and these in turn have pointed to research areas needing further attention. A preliminary design is presented for a lunar outpost shelter. Additionally, the design methodology is explored, and early enabling technologies are identified to facilitate an understanding of lunar shelter designs from an integrated system standpoint.     

Dust formation in a BOF converter

Minimisation of waste and manipulation of residues to suit succeeding processes today is one of the steel works most important research areas. BOF dust is expensive to depose in landfills and difficult to recycle due to its zinc contents. The simultaneous loss of raw materials and cost increase makes it important to minimise the generation of dust. This can be done by employing better process control systems with regard to the mechanisms governing the generation. Four dust forming mechanisms can be considered in a converter: ejection of metal, ejection of slag, entrainment of charged material and vaporisation. In order to determine the importance of the four dust forming mechanisms and to characterise dust, with special emphasis to zinc, the off-gas from a 100-t BOF was sampled during twenty seven heats. The sampling equipment allows the sampling of both solid dust particles and vaporised elements. Samples from the first and the second part of blowing show significant differences both in chemical composition and in the origin of formation. The major dust formation mechanism is the ejection of metal and slag, respectively. Entrainment of solids plays an important role only during the first part of blowing. Vaporisation of elements from the bath is most important during the end of blowing. The formation of dust is influenced by process operation control, especially lance position, silica contents and time of charging of slag formers. Zinc is mostly found on the rim of ejected particles where a gradual transition of zinc oxide to zinc ferrite to iron oxide is found. At sampling temperatures of between 800 and 1000°C most of the zinc had already condensed.     

Characterization of Lunar Dust for Toxicological Studies. I: Particle Size Distribution

The particle size distribution (PSD) of lunar dust, the <20?μm portion of the regolith, was determined as an initial step in the study of the possible toxicological effects it may have on the human respiratory and pulmonary systems. Utilizing scanning electron microscopy, PSDs were determined for Apollo 11 (10084) and 17 (70051) dust samples, as well as lunar dust simulant JSC-1Avf. The novel methodology employed is described in detail. All measured PSDs feature a log-normal distribution having a single mode in a range 100–300?nm for lunar dust samples, but the lunar simulant has a mode at ～ 600?nm.     

The impact of aerosols on solar ultraviolet radiation and photochemical smog

Photochemical smog, or ground-level ozone, has been the most recalcitrant of air pollution problems, but reductions in emissions of sulfur and hydrocarbons may yield unanticipated benefits in air quality. While sulfate and some organic aerosol particles scatter solar radiation back into space and can cool Earth's surface, they also change the actinic flux of ultraviolet (UV) radiation. Observations and numerical models show that UV-scattering particles in the boundary layer accelerate photochemical reactions and smog production, but UV-absorbing aerosols such as mineral dust and soot inhibit smog production. Results could have major implications for the control of air pollution.     

Model for Granular Materials with Surface Energy Forces

In light of environmental differences (such as gravitational fields, surface temperatures, atmospheric pressures, etc.), the mechanical behavior of the subsurface soil on the Moon is expected to be different from that on the Earth. Before any construction on the Moon can be envisaged, a proper understanding of soil properties and its mechanical behavior in these different environmental conditions is essential. This paper investigates the possible effect of surface-energy forces on the shear strength of lunar soil. All materials, with or without a net surface charge, exhibit surface-energy forces, which act at a very short range. Although, these forces are negligible for usual sand or silty sand on Earth, they may be important for surface activated particles under extremely low lunar atmospheric pressure. This paper describes a constitutive modeling method for granular material considering particle level interactions. Comparisons of numerical simulations and experimental results on Hostun sand show that the model can accurately reproduce the overall mechanical behavior of soils under terrestrial conditions. The model is then extended to include surface-energy forces between particles in order to describe the possible behavior of lunar soil under extremely low atmospheric pressure conditions. Under these conditions, the model shows that soil has an increase of shear strength due to the effect of surface-energy forces. The magnitude of increased shear strength is in reasonable agreement with the observations of lunar soil made on the Moon’s surface.     

Electrostatic Cleaning System for Removing Lunar Dust Adhering to Space Suits

Removing lunar dust adhering to astronaut space suits is critically important for long-term lunar exploration. We are developing an automatic cleaning system that uses electrostatic force. It employs an alternating electrostatic field that forms a barrier on the surface of fabrics. In this study, we applied single-phase rectangular voltage to parallel wire electrodes stitched into the insulating fabric of space suits. By applying mechanical vibration and operating the system in a vacuum, we realized high performance: the cleaning rate exceeded 80%. Flicking out particles smaller than 10?μm in diameter that were trapped between fibers was difficult, but this system can perform preliminary space suit cleaning and save precious time for astronauts on the moon.     

Analysis of Lunar-Habitat Structure Using Waterless Concrete and Tension Glass Fibers

The studies reported in this paper were undertaken to evaluate the maximum use of lunar in situ resources for surface construction, such as a habitat structure for a permanent manned lunar base. This type of activity is well into the future, but there are possible near-term applications that could utilize in situ resources for protection from radiation of surface power reactors, solar flares, and micrometeorite damage. “Waterless” concrete made of sulfur, a by-product material of oxygen and carbon extractions, is a viable alternative to hydraulic cement. Sulfur–lunar regolith concrete is an ideal material for building structures on the moon. Its availability, high strength, and durability properties make it a very attractive candidate for the development of the first lunar-construction activities. Regolith-derived glass rebar and fiber can also be used with “concrete” made with in situ regolith. Development of such habitats pose tremendous challenges that can be met by the combination of innovative design with cutting-edge technologies that are appropriate for planetary surface habitats with multiple applications for Earth and beyond.     

Evolution of the vertebrate H1 histone class: evidence for the functional differentiation of the subtypes

BACKGROUND: Indoor suspended particulate matter (SPM) consists of many different types of particles, the vast majority of which are less than 2.5 microm in diameter. The question arises how these particles may contribute to asthma and respiratory symptoms. One possibility is that airborne dust particles act as carriers of allergens into the airways, as several allergens have been found to be associated with inhalable airborne dust particles. OBJECTIVE: We studied the presence of three different allergens on the surface of SPM, i.e. Can f 1 (dog), Bet v 1 (birch pollen) and Der p 1 (house dust mite). We also examined the ability of diesel exhaust particulates (DEP) to attach these allergens and Fel d I (cat) in vitro. METHODS: SPM was collected on polycarbonate filters and an immunogold labelling technique was used to detect the allergens on the particles. The specimens were examined in the backscatter mode of a scanning electron microscope. The same technique was used to examine the binding of the allergens to DEP, after exposing DEP to either crude allergen extracts or partly purified allergens. RESULTS: Both Can f 1 and Bet v 1 allergens were detected on the surface of the soot particles in SPM mixtures, although to a lesser degree than previously found with Fel d 1. Der p 1 (house dust mite), however, did not show any significant binding to SPM particles. Furthermore, DEP had the ability to adsorb all four allergens in vitro, although to a varying extent. CONCLUSION: Soot particles in airborne house dust may act as carriers of several allergens in indoor air. Furthermore, DEP has the ability to bind all the four allergens investigated under aqueous conditions in vitro.     

Dust formation in the arc heating of zinc-plated steel

Dust formation in the plasma-arc heating of zinc-plated steel in argon is studied, when the current is 170–190 A, the argon flow rate is 0.06 m³/h, and the pressure in the furnace chamber is 0.1 MPa. Zinc evaporates practically completely in the first 30 s of heating. The structure of the trapped zinc-bearing dust is heterogeneous: the particles are of different shape (spherical, acicular, or membranous particles), different size, and different composition. The composition of individual dust particles is analyzed on an iCAP 6300 spectrometer (Thermo Electron, United States). On that basis, their oxide composition is estimated by means of Terra software. The dust includes particles consisting of ZnO, Fe₂O₄, carbon, and pure iron. The results indicate that, in the plasma heating of zinc-plated steel, the zinc-bearing dust may be captured separately from the other dust in the initial smelting period.     

Lunar Structures Generated and Shielded with On‐Site Materials

Lunar base structures can be constructed in situ and∕or shielded using unprocessed or minimally processed lunar resources with technologies utilized in harsh terrestrial regions for the past four millennia. Single‐ and double‐curvature compression shell structures constructed using the techniques of building without centering can be applied on the lunar surface, where the low gravity and resultant small angle of repose allow for greater spans than under terrestrial condition. Suggested construction materials range from meteorites and lunar rocks to lunar adobe created from unprocessed regolith. Magma structures can be generated and cast based on natural formation, such as lava tubes and voids, using focus sunlight, microwave, plasma, and nuclear energy. Ceramic modules can be “thrown” on a centrifugally gyrating platform. These techniques integrate high‐tech and low‐tech construction methods of Western, Eastern, and Native American cultures, allowing for direct interaction with nature while working to economical and technical advantage by using primarily local lunar resources and human skills.     

Two-Dimensional Simulation of the Angle of Repose for a Particle System with Electrostatic Charge under Lunar and Earth Gravity

This paper presents a study of the angle of repose of a two-dimensional particle system under the Earth and Moon gravity fields. The particles interact with electrostatic forces in addition to friction. A two-dimensional discrete element method is used in this analysis with two particle shapes, circular and noncircular. The noncircular shape is constructed with overlapping pairs of disks. For the range of parameters studied, the angle of repose shows little sensitivity to gravity. The sensitivity to friction and electrostatic charges can be either significant or negligible, depending on the range of these values. For each contact friction, there is a threshold of electric charge on the particle such that the angle of repose suddenly drops to zero when the charge exceeds this threshold. The existence of this threshold, once validated in three-dimensional systems, may provide an opportunity to measure the electrostatic charges of the lunar dust in situ.     

Conceptual Design of Unpressurized Shelters on Lunar Surface

Three concepts for the shelters on the moon are presented here. It is envisaged that the first robots will land on the moon and start preparing sites for advanced bases and also for future human presence. These robots will encounter severe radiation and micrometeor hits when they are exposed to the lunar atmosphere. During the period of intense solar radiation these robots have to be temporarily sheltered, since shielding on the robots may not be adequate to protect the instruments. The construction of these shelters has to be performed with very little equipment support. This paper presents concepts and their feasibility analysis for the fabrication of shelters under such stringent constraints.     

Modeling of oxidation of molybdenum particles during plasma spray deposition

An oxidation model for molybdenum particles during the plasma spray deposition process is presented. Based on a well-verified model for plasma chemistry and the heating and phase change of particles in a plasma plume, this model accounts for the oxidant diffusion around the surface of particles or splats, oxidation on the surface, as well as oxygen diffusion in molten molybdenum. Calculations are performed for a single molybdenum particle sprayed under Metco-9MB spraying conditions. The oxidation features of particles during the light are compared with those during the deposition. The result shows the dominance of oxidation of a molybdenum particle during the flight, as well as during deposition when the substrate temperature is high (above 400 °C).     

Use of Explosives on The Moon

The utilization of explosives for excavation on the lunar surface is under serious consideration as a part of the design for construction of temporary and permanent bases. An excavation research program has shown that small‐scale explosives blasting in a lunar‐soil simulant will greatly reduce the digging forces required for scoop and dragline excavators. Some crater‐blasting parameters were determined for the lunar soil simulant at one Earth gravity and at 10 Earth gravities using a centrifuge. The size of the craters produced at 10 Earth gs matched those formed at one earth g by scaling according to the weight of the explosive. These data can be applied to explosive‐excavation problems such as habitat construction, burial of nuclear power sources, and the rapid construction of shelters remote from the main base to shield against solar‐flare activity.     

Surface Cleanliness Effect on Lunar Soil Shear Strength

Lunar soil consists of dry silty sand. Observations and measurements conducted during Surveyor, Apollo, and Luna missions indicated that the lunar soil is unusually cohesive. This is attributable to the fact that thick layers of adsorbed gases, which coat and lubricate soil particles on Earth, are absent in the ultrahigh vacuum on the Moon. “Surface cleanliness” is introduced as a new parameter for describing soils in different planetary environments. It is defined as the dimensionless inverse of adsorbate thickness on solid surfaces. By this definition, the ultrahigh vacuum on the Moon is associated with high surface cleanliness, while Earth's atmosphere is associated with low surface cleanliness. A model is developed to calculate surface cleanliness and its effect on shear strength in any planetary environment. Results obtained from the model compare well with data from previous ultrahigh vacuum and variable temperature laboratory experiments on Earth soils. It is shown that surface cleanliness is an important parameter with respect to lunar soil shear strength.