A series of experiments have been conducted to study the failure behavior of columns and piles comprised of cohesive fine powders in 1 g as a proxy for those which might occur in the agglomerated asteroid structure composed of cm-m size pebbles and boulders in a microgravity environment. Initially symmetrical piles of fine powders, under gravitation or centrifugal stress, develop features similar to those observed on asteroids, such as slide planes and finer cohesive structures. Failure of cohesive columns of fine powders occurs by the nucleation and propagation of fracture planes. In some cases, forming steep cliffs, also reminiscent of features observed on asteroids. Correlation between observed column failure and numerical simulations has been demonstrated based on preliminary results. Microstructure and particle size distribution are shown to substantially determine the extent of cohesiveness. Enhanced cohesion was observed for specific ratios of larger particle intermixed with fine powders. We propose that the wide range of qualitative features and behaviors may reasonably represent those observed on asteroid features as the surface ages. This work has important implications for our understanding and preparation for future missions to NEOs.

This paper provides a detailed description of why molecular transport analysis is critical to mission success and a development overview for an augmented reality data visualization application used to effectively communicate the results. A small amount of contaminant accumulation on each optical element can cause unacceptable degradation of the optical train which is why contamination control is one of the most critical elements in the design and production of space telescopes. Effective communication of mission risk and the effect of operational maneuvers on contaminant transport is essential to project scientists, program managers, operations and contamination control engineers, and students entering the field. Intuitive tools to convey this information are sorely needed. Therefore, translating dry data sets into an augmented reality experience offers an excellent opportunity to enhance and improve communication of this information. The proof of concept demonstration for the augmented reality data visualization application presented in this work is a work in progress and this paper provides several lessons learned during development. Namely OpenTD in Thermal Desktop version 6.1 can be used as a means of automating the TD to Unity pipeline while preserving node information. Using virtual reality to develop AR interfaces can reduce development time, but the UI must be tested in VR with an AR environment in mind. Further development of this application could enable visualizing the effect of changing mission parameters on contamination transport during mission planning.

The kinetics of molecular transport of contaminant species is highly dependent on the distribution of desorption activation energies. Accurate measurements of these kinetics are essential to improving confidence in molecular transport modeling and setting appropriate beginning of life (BOL) cleanliness requirements. We present results that combine laboratory experiments with computer simulations to determine the distribution of effective activation energies for outgassing species from a urethane paint system and non-volatile residue (NVR) collected from an ISO Class 5 cleanroom contamination monitoring plate. Outgassing from samples of primer overcoated with urethane paint were analyzed with the temperature controlled quartz crystal microbalance thermogravimetric analysis (QTGA) technique during the final stages of vacuum baking; cleanroom NVR was also analyzed via QTGA. A computer model was developed to simulate the QTGA results. Data from the experimental QTGA were compared to the simulated QTGA to obtain a distribution of desorption activation energies for contaminant species. The interior of the Ozone Mapping and Profiler Suite (OMPS) science instrument is primed and painted with polyurethane/epoxy material. The distribution of activation energies derived in this study was incorporated in the molecular transport model of the OMPS science instrument, on the Suomi National Polar-Orbiting Partnership Satellite, yielding results that are consistent with the on-orbit optical performance data.

A molecular transport model for the Europa UV Spectrograph instrument has been developed to predict optical throughput over the course of the mission lifetime. At beginning of life, internal surfaces will be covered with a thin layer of non-volatile residue (NVR); after launch, contaminants from the electronics components will diffuse out of their parent materials, adding to the overall contaminant environment. The transport of these contaminants, and accumulation onto optical elements, is dependent on geometry, temperature, transport kinetics, and contamination process control during instrument build Quantitative thermogravimetric analysis (QTGA) was used to estimate the distribution of activation energies for desorption of contaminant from electronics, and that of NVR. An assessment of the effectiveness of different lengths and frequencies of decontamination cycles was performed, and a 12-hour decontamination sequence was effective at removing accumulated contaminant We found that the combined effects of temperature and view factors resulted in the curious result that whether the telescope aperture door was open or closed had insignificant effect on optics cleanliness. Allowing the door to be closed through much of mission life, in turn, protects the spectrograph from being contaminated by thruster plumes or contaminant from the spacecraft environment. Finally, a parametric analysis of the effect of activation energy distribution was performed. If a lower energy distribution, characteristic of electronics outgassing was used for NVR transport, the throughput margin would be reduced significantly, but the coverage would still be below that at beginning of life.

The air present in every spacecraft will vent during launch, so spacecraft hardware must be designed sufficiently to withstand the resulting pressure differences that develop as the external pressure decreases from that at sea level to negligible levels in about 2 minutes. Pressure differentials can be significant, especially for honeycomb panels within which air must travel through many small perforations in honeycomb cell walls to reach vent ports, and cases have been reported of honeycomb panels exploding during launch. Thus, work has been conducted at Ball Aerospace to not only model air venting from honeycomb panels, but also develop techniques to simplify the simulations. Predictions have compared well with pressure differences measured in a test panel during depressurization tests. The results provide confidence in the ability to predict pressure differences in honeycomb panels of any shape and cell size.

On October 28, 2011, the Suomi National Polar-orbiting Partnership (Suomi NPP) satellite launched at Vandenberg Air Force base aboard a United Launch Alliance Delta II rocket. Included among the five instruments was the Ozone Mapping and Profiler Suite (OMPS), an advanced suite of three hyperspectral instruments built by Ball Aerospace and Technologies Corporation (BATC) for the NASA Goddard Space Flight Center. Molecular transport modeling is used to predict optical throughput changes due to contaminant accumulation to ensure performance margin to End Of Life. The OMPS Nadir Profiler, operating at the lowest wavelengths of 250 - 310 nm, is most sensitive to contaminant accumulation. Geometry, thermal profile and material properties must be accurately modeled in order to have confidence in the results, yet it is well known that the complex chemistry and process dependent variability of aerospace materials presents a substantial challenge to the modeler. Assumptions about the absorption coefficients, desorption and diffusion kinetics of outgassing species from polymeric materials dramatically affect the model predictions, yet it is rare indeed that on-mission data is analyzed at a later date as a means to compare with modeling results. Optical throughput measurements for the Ozone and Mapping Profiler Suite on the Suomi NPP Satellite indicate that optical throughput degradation between day 145 and day 858 is less than 0.5%. We will show how assumptions about outgassing rates and desorption energies, in particular, dramatically affect the modeled optical throughput and what assumptions represent the on-orbit data.

Tenacious adhesion of dust to surfaces in the vacuum environment of space is a significant obstacle to exploration and scientific discovery on the Moon, Mars and asteroids. Mitigating particle adhesion is also costly and difficult during semiconductor or optics processing on earth. Over the last eight years at Ball Aerospace & Technologies Corp ( BATC), we have demonstrated the effectiveness of an ion beam process that dramatically reduces the adhesion of lunar simulant dust to quartz, glass, Kapton, Teflon and silicon surfaces in dry, ambient, and vacuum environments. Treated silver-coated Teflon coupons performed well in a space-simulated environment at NASA Glenn Research Center. Surface roughening on an Angstrom-level scale was found to correlate well with reduced adhesion, as did contact angle hysteresis. The large difference in advancing and receding contact angles reflects topological and/or chemical heterogeneity. Differences in contact charging are not believed to be major players in dust adhesion reduction. The physical basis of the dust mitigating properties of these modified surfaces is believed to be substantially due to nanometer scale differences between treated and virgin surfaces. Lastly, because this process does not add material, unlike a lotus-like coating or the work function matching coating, nor does it require power like the electrodynamic screen, it is particularly attractive for optical or thermal control materials that cannot tolerate coatings or where power is not available.

We are beginning a three-year effort to study regolith properties and processes on low-gravity, small asteroids by conducting analog experiments with cohesive powders in a 1-g laboratory environment. Our goal is to develop an improved understanding of the role of cohesion in affecting regolith processes and surface morphology of small Solar System bodies, some the targets of ongoing and proposed missions, and to quantify the range of expected mechanical properties of such regoliths.

Historical experience and previously published papers have shown that contamination sampling techniques influence the cleanliness results of spaceflight hardware. Programs rely on this data to show that derived or contractual requirements are met at delivery. Particle sampling using tape lifts and rinses was performed on the James Webb Space Telescope (JWST) Primary Mirror Segment Assemblies (PMSAs) hardware. Sampling was performed on identical hardware with both sampling techniques. The hardware was sampled at comparable stages of assembly which provided hardware with similar levels of particulate contamination. Results from the two sampling techniques are compared. In one technique, sampling was performed by rinsing (with a hand-squeeze bottle with low pressure) followed by a tape lift; the other technique used a tape lift only. The relationship of particle size distribution, types of particles, level of particle contamination, and particle removal rate by sampling technique are examined. Comparison of the particle sampling results provides a basis for interpreting results depending on sampling techniques. Improving the contamination engineer’s ability to interpret results is particularly useful when hardware configuration or surface finish dictate which sampling technique can be used. When one can choose the sampling technique, the results of this study can provide guidance on which technique is more appropriate depending on the circumstances. Results show that tape lifts remove more particles than low pressure rinses; furthermore that tape lift only is better than the combined operation of a rinse closely followed by a tape lift. Results also indicate that further work should be performed on different surface finishes, rinsing techniques, and particulate contamination levels.

Dust has been recognized as one of the greatest hazards in continued lunar exploration due to its tenacious adhesion to everything with which it comes into contact. Unfortunately, there is little known about the mechanisms of adhesion on widely varying surface types: van der Waals and electrostatic forces are the dominant forces under consideration here. Surface energy, roughness, mechanical properties and electronic properties are all known to contribute to the adhesion characteristics. An optimal solution to mitigate dust adhesion would be to identify the dominant components of the adhesive force and to reduce that force by surface modification. In this study, an ion beam process was used to modify (treat) the surfaces of three dramatically different materials spanning the range of conductor (black Kapton), semiconductor (silicon), and insulator (quartz). Adhesive forces between less than 25μm JSC-1 lunar simulants and these virgin/treated surfaces were measured in vacuum using a centrifugal force detachment method. We found that JSC-1 particles adhered less to treated silicon and quartz surfaces, correlated with a reduction in van der Waals force due to a reduced surface energy. The large reduction in adhesion for treated black Kapton is mainly due to the large decrease in the electrostatic (image) force that results from reduced contact charging. Materials in space and on the lunar surface will be directly exposed to high-energy ultraviolet radiation prior to being covered by dust, so the UV irradiation effects on surface adhesion were also examined. Both virgin and treated quartz surfaces are most affected by the UV-irradiation, showing dramatically increased adhesion.

We have developed surface chemical modification processes which when applied to a variety of surfaces renders the surfaces resistant to particulate contamination. Chemically modified surfaces are shown to shed particles at a dramatically higher level as compared to native surfaces. This is demonstrated on a variety of surfaces that include optics, polymers, metals and silicon. The adhesive force between lunar stimulant particles (JSC-1AF) and black Kapton is measured to decrease by 95% when the black Kapton surface is chemically modified. The chemical modification process is demonstrated to not change the surface roughness of a smooth silicon wafer while decreasing particle affinity. The optical properties of chemically modified surfaces are reported. The surface modification process is robust and stable to aggressive cleaning. The particle shedding properties of chemically modified surfaces are retained after simulated extraterrestrial vacuum ultra-violet light exposure and temperature excursions to 140 degrees C. This technology has the potential to provide a robust passive particle mitigation solution for optics, mechanical systems and particle sensitive applications.

We have formed ultrathin metal films with nanometer-scale features by metal shadowing of two-dimensional protein crystals followed by fast atom beam milling. In this process, the metal overlayer is formed into a screen consisting of hexagonal arrays of 10 nm size holes with a 22 nm periodicity. Thin films of Ti, Ta, Pt, Pt/C, Pt/Ir, Pt/Ir/C, Va, Cr, Ni, Ag, Zr, and Nb show dramatic differences in their response to this method of nanotexturing. Evaluation of film morphology by transmission electron microscopy before and after milling reveals a correlation between microstructural characteristics and the features of the nanostructures formed by different metals. The dominant factor for determining the uniformity and quality of the formed nanostructure is a thin film which is amorphous or very fine grained after milling. Overall pattern uniformity and individual hole boundaries which are smooth and round are necessary for optimal patterning. Crystallization and grain growth seem to negatively affect patterning quality, resulting specifically in extensive bridging between holes which generally have irregular boundaries.

We have examined the structure of S-layers isolated from Sulfolobus acidocaldarius using atomic force microscopy (AFM) and transmission electron microscopy (TEM). From the AFM images, we were able to directly observe individual dimers of the crystal, defects in the crystal structure, and twin boundaries. We have identified two types of boundaries, one defined by a mirror plane and the other by a glide plane. This work shows that twin boundaries are highly structured regions that are directly related to the organization of units within each crystal domain. Projection maps from TEM images have shown that there are significant differences in the final average maps has allowed us to relate high magnification views obtained by AFM to the relatively high resolution information obtained by electron microscopy and image processing.

Atomic force microscopy has been used to measure the surface profile of a periodic array of 10-nanometer (nm)-diameter holes fabricated by fast-atom beam milling of a smooth graphite surface in which a 3.5-nm-thick titanium oxide screen was used as a mask. The nanostructured titanium oxide mask was itself derived from a protein crystal template. Pattern transfer from the biological crystal to the metal oxide film and finally to the graphite substrate was accomplished entirely by parallel processing.

We have produced nanometer scale patterning (nanostructures) by metal shadowing of two-dimensional protein crystals (S-layers), followed by milling with ions or fast atoms. In this parallel process, the metal overlayer is formed into a metal screen consisting of hexagonal arrays of 10 nm size holes with a 20 nm periodicity. We have studied the time evolution of the milling process, and temperature effects. Nanostructure formation may be due to preferential sputtering of the troughs relative to the crests of the metallized S-layer. The effect of temperature on pattern formation indicates that thermal diffusion is also important.

The growth of quartz into amorphous silica has been observed for the first time at atmospheric pressure. Ion implantation and ion channeling techniques were used to create and monitor the thickness of a surface amorphous layer on a quartz crystal. The growth rate at an (0001) surface is consistent with extrapolations of earlier measurements of the growth rate at higher pressures and temperatures.

The production of small (5–200 nm) spheres of silicon and germanium from their melts by electrohydrodynamic atomisation (EHD) was previously reported [1]. We have examined the formation of amorphous and crystalline phases in such spheres. Analysis of electron diffraction data reveals that the smallest spheres are amorphous, with a tetrahedrally coordinated covalent random network structure, rather than being either very fine grained polycrystals or configurationally frozen metallic liquids. The formation of the semiconducting amorphous and crystalline phases is considered in terms of a competitive classical nucleation analysis, and good agreement is found for the relative proportion of each phase as a function of sphere size.