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An astronaut caution and warning system is described which monitors various life support system parameters and detects out-of-range parameter conditions. The warning system generates a warning tone and displays the malfunction condition to the astronaut along with the proper corrective procedures required.
Point defect formation associated with early stages of optical damage was observed unexpectedly in two, and possibly three, different optical materials subjected to short-duration space exposure. Three calcium fluoride, two lithium fluoride, and three magnesium fluoride samples were flown on Space Shuttle flight STS-46 as part of the Evaluation of Oxygen Interactions with Materials - Third Phase experiment. One each of the calcium and magnesium fluoride samples was held at a fixed temperature of 60 C during the space exposure, while the temperatures of the other samples were allowed to vary with the ambient temperature of the shuttle cargo bay. Pre-flight and post-flight optical absorption measurements were performed on all of the samples. With the possible exception of the magnesium fluoride samples, every sample clearly showed the formation of F-centers in that section of the sample that was exposed to the low earth orbit environment. Solar vacuum ultraviolet radiation is the most probable primary cause of the defect formation; however, the resulting surface metallization may be synergistically altered by the atomic oxygen environment.
A test of the second postulate of special relativity, the universality of the speed of light, using the ExTRAS (Experiment on Timing Ranging and Atmospheric Sounding) payload to be flown on board a Russian Meteor-3M satellite (launch date January 1997) is proposed. The propagation time of a light signal transmitted from one point to another without reflection would be measured directly by comparing the phases of two hydrogen maser clocks, one on board and one on the ground, using laser or microwave time transfer systems. An estimated uncertainty budget of the proposed measurements is given, resulting in an expected sensitivity of the experiment of delta c/c is less than 8xl0(exp -10) which would be an improvement by a factor of approximately 430 over previous direct measurements and by a factor of approximately 4 over the best indirect measurement. The proposed test would require no equipment additional to what is already planned and so is of inherently low-cost. It could be carried out by anyone having access to a laser or microwave ground station and a hydrogen maser.
We used quantitative electron-probe energy-dispersive x-ray microanalysis to localize endogenous Na, Cl, K, P, S, Mg and Ca in cryofixed and freeze-dried cryosections of the cap (i.e. the putative site of graviperception) and elongating zone (i.e. site of gravicurvature) of horizontally oriented roots of Zea mays. Ca, Na, Cl, K and Mg accumulate along the lower side of caps of horizontally oriented roots. The most dramatic asymmetries of these ions occur in the apoplast, especially the mucilage. We could not detect any significant differences in the concentrations of these ions in the central cytoplasm of columella cells along the upper and lower sides of caps of horizontally-oriented roots. However, the increased amounts of Na, Cl, K and Mg in the longitudinal walls of columella cells along the lower side of the cap suggest that these ions may move down through the columella tissue of horizontally-oriented roots. Ca also accumulates (largely in the mucilage) along the lower side of the elongating zone of horizontally-oriented roots, while Na, P, Cl and K tend to accumulate along the upper side of the elongating zone. Of these ions, only K increases in concentration in the cytoplasm and longitudinal walls of cortical cells in the upper vs lower sides of the elongating zone. These results indicate that (1) gravity-induced asymmetries of ions differ significantly in the cap and elongating zone of graviresponding roots, (2) Ca accumulates along the lower side of the cap and elongating zone of graviresponding roots, (3) increased growth of the upper side of the elongating zone of horizontally-oriented roots correlates positively with increased amounts of K in the cytoplasm and longitudinal walls of cortical cells, and (4) the apoplast (especially the mucilage) may be an important component of the pathway via which ions move in graviresponding rots of Zea mays. These results are discussed relative to mechanisms for graviperception and gravicurvature of roots.
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As the space population grows over time, persistent issues of human urbanism will eclipse within a historically short time the technical challenges of space exploration that dominate current efforts. Although urban design teams will have to integrate many new disciplines into their already renaissance array of expertise, doing so will enable them to adapt ancient, proven solutions to opportunities afforded by expanding urbanism offworld. This paper updates the author's original 1988 treatment of the subject.
Shergottites comprise most of the Martian meteorites and have a mafic to ultramafic bulk composition and a diversity of igneous textures [1].Olivine-phyric and poikilitic shergottites are sub-classes of shergottites and characterized by having a crystal cargo of large mafic minerals. Olivine-phyric shergottites have porphyritic textures of large olivinemegacrysts set in a fine-grained groundmass of pyroxene and maskelynite [2]. The poikilitic shergottites have assemblages of olivine chadocrysts poikilitically-enclosed by cm-sized pyroxene oikocrysts set in a coarse-grained groundmass of olivine and maskelynite [3,4]. The large crystal cargos in these samples are some of the first minerals to crystallize from their respective parent melts and have been extensively studied to understand shergottite petrogenesis. For instance, compositions of early-formed olivine and pyroxene in equilibrium with other phases (e.g. spinels) are used to establish depths, temperatures, and redox conditions of crystallization. There is increasing agreement that olivine megacrysts and poikilitic assemblages formed at or near the crust – mantle boundary (~85 km) before entrainment, ascent, and complete crystallization at or near the surface [1,3,4,6,7,8,9]. Additionally, linear olivine megacryst crystal size distribution (CSD)patterns and observations of polyhedral morphologies[8,9,10] are commonly interpreted to reflect steady-state crystallization under equilibrium conditions. However, oscillatory phosphorus zonation patterns in olivine from many samples indicate fluctuations in growth rates[10,12]. Recent studies measuring dendritic phosphorus zonation in terrestrial olivines [13] and experimental studies measuring how undercooling (undercooling is defined as the liquidus temperature minus the temperature being considered) controls changes in olivine morphology [14] have questioned the canonical view that large olivine megacrysts grow slowly and concentrically under equilibrium conditions. Here we present X-ray CT results from olivine-phyric and poikilitic shergottites that challenge the notion that early-formed minerals grew slowly under equilibrium conditions.
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The surfaces of the moon, Mars, and that of some asteroids are covered with a layer of dust that may hinder robotic and human exploration missions. During the Apollo missions, for example, lunar dust caused a number of issues including vision obscuration, false instrument readings, contamination, and elevated temperatures. In fact, some equipment neared failure after only 75 hours on the lunar surface due to effects of lunar dust. NASA's Kennedy Space Center has developed an active technology to remove dust from surfaces during exploration missions. The Electrodynamic Dust Shield (EDS), which consists of a series of embedded electrodes in a high dielectric strength substrate, uses a low power, low frequency signal that produces an electric field wave that travels across the surface. This non-uniform electric field generates dielectrophoretic and electrostatic forces capable of moving dust out of these surfaces. Implementations of the EDS have been developed for solar radiators, optical systems, camera lenses, visors, windows, thermal radiators, and fabrics The EDS implementation for transparent applications (solar panels, optical systems, windows, etc.) uses transparent indium tin oxide electrodes on glass or transparent lm. Extensive testing was performed in a roughly simulated lunar environment (one-sixth gravity at 1 mPa atmospheric pressure) with lunar simulant dust. EDS panels over solar radiators showed dust removal that restored solar panel output reaching values very close to their initial output. EDS implementations for thermal radiator protection (metallic spacecraft surfaces with white thermal paint and reflective films) were also extensively tested at similar high vacuum conditions. Reflectance spectra for these types of implementations showed dust removal efficiencies in the 96% to 99% range. These tests indicate that the EDS technology is now at a Technology Readiness Level of 4 to 5. As part of EDS development, a flight version is being prepared for several flight opportunities. The flight version of the EDS will incorporate significantly smaller electronics, with an expected mass and volume of 500 g and 350 cm(exp. 3) respectively. One of the opportunities is an International Space Station (ISS) experiment: Materials for International Space Station Experiment 10 (MISSE-10). This experiment aims to verify the EDS can withstand the harsh environment of space and will look to closely replicate the solar environment experienced on the moon. A second flight opportunity exists to provide an EDS to several companies as part of NASA's Lunar CATALYST program. The current mission concept would fly the EDS on the footpad of one of the Lunar CATALYST vehicles. Dust will likely deposit on the footpad through normal surface rover activities, but also upon landing where lunar dust is expected to be uplifted. To analyze the e effectiveness of the EDS system, photographs of the footpad with one of the spacecrafts onboard cameras are anticipated. If successful in these test flights, the EDS technology will be ready to be used in the protection of actual mission equipment for future NASA and commercial missions to the moon, asteroids, and Mars.
High-temperature, oxidation-resistant chamber materials offer the thermal margin for high performance and extended lifetimes for radiation-cooled rockets. Rhenium (Re) coated with iridium (Ir) allow hours of operation at 2200 C on Earth-storable propellants. One process for manufacturing Ir/Re rocket chambers is the fabrication of Re substrates by powder metallurgy (PM) and the application of Ir coatings by using electroformed deposition (ED). ED Ir coatings, however, have been found to be porous and poorly adherent. The integrity of ED Ir coatings could be improved by densification after the electroforming process. This report summarizes the testing of two 22-N, ED Ir/PM Re rocket chambers that were subjected to post-deposition treatments in an effort to densify the Ir coating. One chamber was vacuum annealed, while the other chamber was subjected to hot isostatic pressure (HIP). The chambers were tested on gaseous oxygen/gaseous hydrogen propellants, at mixture ratios that simulated the oxidizing environments of Earth-storable propellants. ne annealed ED Ir/PM Re chamber was tested for a total of 24 firings and 4.58 hr at a mixture ratio of 4.2. After only 9 firings, the annealed ED Ir coating began to blister and spall upstream of the throat. The blistering and spalling were similar to what had been experienced with unannealed, as-deposited ED Ir coatings. The HIP ED Ir/PM Re chamber was tested for a total of 91 firings and 11.45 hr at mixture ratios of 3.2 and 4.2. The HIP ED Ir coating remained adherent to the Re substrate throughout testing; there were no visible signs of coating degradation. Metallography revealed, however, thinning of the HIP Ir coating and occasional pores in the Re layer upstream of the throat. Pinholes in the Ir coating may have provided a path for oxidation of the Re substrate at these locations. The HIP ED Ir coating proved to be more effective than vacuum annealed and as-deposited ED Ir. Further densification is still required to match the integrity of chemically vapor deposited Ir coatings. Despite this, the successful long duration testing of the HIP ED Ir chamber, in an oxidizing environment comparable to Earth-storable propellants, demonstrated the viability of this Ir/Re rocket fabrication process.
ElectroDynamic (ED) Tethers can generate continuous low thrust in a low Earth orbit. An induced current running through the length of the tether reacts with the geomagnetic field to produce thrust. The amount of thrust scales with tether lens!th and current. The International Space Station (ISS) requires periodic reboost to maintain an approximately circular orbit t above the Earth. The baseline reboost method is a traditional bi-propellant rocket thruster and tankage system which must to be refueled via Soyuz / Progress or other launch vehicle. The estimated propellant costs associated with keeping ISS in the designated orbit over a 10-year life have been extremely high. The ED Tether would draw energy from the renewable ISS Solar Array electrical power system. Propulsion requirements for ISS vary depending on solar wind and other conditions. It is projected that a ED Tether could provide the majority of the required reboost thrust for ISS for a nominal solar year. For above nominal solar wind years the ISS would have to use the rocket reboost system, but at a greatly reduced level. Thus resulting in substantial cost savings, via the reduction in the number of Earth-to-orbit launch vehicle flights to the ISS that must bring reboost propellant. However, the purposes of this paper is to further Previous research on an ISS ED Tether and examine the operational and technical issues working against using a ED Tether on ISS. Issues such as Shuttle rendezvous and flight path concerns raise serious safety concerns and restrictions on tether use. Tether issues such as tether librations and off angle thrust raise concerns about impacts to microgravity payloads and the long-term effect on ISS orbital path and inclination. Operational issues such as peak power available to an ED Tether and allowable duty cycle may impose severe restrictions on tether design and ultimately limit the practicality of an ED Tether on ISS. Thus while at first glance the cost numbers appear to be strongly in favor of an ED Tether the limitations imposed by safety, operations and technical concerns may severely undermine the economic model. Possible Solutions to these problems have been investigated and proposed, however some items like off angle thrust are still being actively investigated for an adequate solution.
The development and maturation of the endolymphatic sac (ES) and duct (ED) were studied in the newt Cynops pyrrhogaster. The ES first appears as an oval capsule at the dorsal-medial tip of the otic vesicle at stage 39, about 11 days after oviposition. The ES consists of polymorphous epithelial cells with a minimum of cytoplasm. The intercellular space (IS) between the epithelial cells is narrow and has a smooth surface. At stage 44, the size of the ES increases as many vacuoles in the IS become filled. At stage 46, 18 days after oviposition, the ES elongates markedly and a slit-like lumen is found in the ES. The epithelium contains a few cell organelles which are scattered in the cytoplasm. The vacuoles in the IS are fused, which expands the IS. Two days later (stage 48), floccular material (endolymph) is present in the expanded lumen. The IS dilates and has a wide and irregular appearance. At stage 50, approximately 26 days after oviposition, the ES extends and expands significantly and crystals (otoconia) can now be seen in the widened lumen of the ES. The cytoplasm of the cuboidal epithelial cells contains an abundance of vesicles surrounded by ribosomes and Golgi complexes. Intercellular digitations are formed in the expanded IS. At stage 54, the ES forms a large bellow-like pouch. Numerous otoconia accumulate in the lumen. Free floating cells and cell debris can be seen in the lumen at this stage. The epithelial cells contain numerous cytoplasmic organelles which are evenly distributed in the cytoplasm. Granules are found in the apical and lateral cytoplasm. The IS is loose and displays a labyrinthine appearance. The primitive ED first appears as a connection between the ES and the saccule but no lumen is present inside at stage 39. At stage 46, a narrow lumen is formed in the ED, which corresponds to the formation of the ES lumen. At stage 50, as the ED extends, floccular material is seen in the lumen. At stage 54, the ED bears numerous microvilli on its luminal surface. Otoconia and endolymph are present in the ED. Tight junctions between the epithelial cells are formed at stage 46. A fully developed intercellular junctional complex is produced at stage 54. Based on the development of the ES and ED, the maturation of function of the ES and ED are discussed.
The International Space Exploration Coordination Group (ISECG) has chosen dust mitigation technology as a Global Exploration Roadmap (GER) critical technology need in order to reduce life cycle cost and risk, and increase the probability of mission success. NASA has also included Particulate Contamination Prevention and Mitigation as a cross-cutting technology to be developed for contamination prevention, cleaning and protection. This technology has been highlighted due to the detrimental effect of dust on both human and robotic missions. During manned Apollo missions, dust caused issues with both equipment and crew. Contamination of equipment caused many issues including incorrect instrument readings and increased temperatures due to masking of thermal radiators. The astronauts were directly affected by dust that covered space suits, obscured face shields and later propagated to the cabin and into the crew's eyes and lungs. Robotic missions on Mars were affected when solar panels were obscured by dust thereby reducing the effectiveness of the solar panels. The Electrostatics and Surface Physics Lab in Swamp Works at the Kennedy Space Center has been developing an Electrodynamic Dust Shield (EDS) to remove dust from multiple surfaces, including glass shields and thermal radiators. This technology has been tested in lab environments and has evolved over several years. Tests of the technology include reduced gravity flights (6g) in which Apollo Lunar dust samples were successfully removed from glass shields while under vacuum (1 millipascal). Further development of the technology is underway to reduce the size of the EDS as well as to perform material and component testing outside of the International Space Station (ISS) on the Materials on International Space Station Experiment X (MISSE-X). This experiment is designed to verify that the EDS can withstand the harsh environment of space and will look to closely replicate the solar environment experienced on the moon. A second flight opportunity exists to provide an EDS to several companies as part of NASA's Lunar CATALYST program. The current mission concept would fly the EDS on the footpad of one of the Lunar CATALYST vehicles. To determine the effectiveness of the EDS system, image analysis will be performed on the footpad before, during and after EDS activation. If successful in these test flights, the Technology Readiness Level (TRL) of the EDS will be raised to a sufficient level to be used in the protection of mission equipment for future NASA and commercial missions to the moon, asteroids, and Mars.
Lunar samples returned from the Apollo program motivated development of the Bence-Albee algorithm for the rapid and accurate analysis of lunar materials, and established interlaboratory comparability through its common use. In the analysis of mineral and rock fragments it became necessary to combine micro- and macroscopic analysis by coupling electron-probe microanalysis (EPMA) with automated stage point counting. A coarse grid that included several thousand points was used, and initially wavelength-dispersive (WDS) and later energydispersive (EDS) data were acquired at discrete stage points using approx. 5 sec count times. A approx 50 micrometer beam diameter was used for WDS and up to 500 micrometer beam diameter for EDS analysis. Average analyses of discretely sampled phases were coupled with the point count data to calculate the bulk composition using matrix algebra. Use of a defocused beam resulted in a contribution from multiple phases to each analytical point, and the analytical data were deconvolved relative to end-member phase chemistry on the fly. Impressive agreement was obtained between WDS and EDS measurements as well as comparison with bulk chemistry obtained by other methods. In the 30 years since these methods were developed, significant improvements in EPMA automation and computer processing have taken place. Digital beam control allows routine collection of x-ray maps by EDS, and stage mapping for WDS is conducted continuously at slew speed and incrementally by sampling at discrete points. Digital pulse processing in EDS systems has significantly increased the throughput for EDS mapping, and the ongoing development of Si-drift detector systems promises mapping capabilities rivaling WDS systems. Spectrum imaging allows a data cube of EDS spectra to be acquired and sophisticated processing of the original data is possible using matrix algebra techniques. The study of lunar and meteoritic materials includes the need to conveniently: (1) Characterize the sample at microscopic and macroscopic scales with relatively high sensitivity, (2) Determine the modal abundance of minerals, and (3) Identify and relocate discrete features of interest in terms of size and chemistry. The coupled substitution of cations in minerals can result in significant variation in mineral chemistry, but at similar average Z, leading to poor backscattered-electron (BSE) contrast discrimination of mineralogy. It is necessary to discriminate phase chemistry at both the trace element level and the major element level. To date, the WDS of microprobe systems is preferred for mapping due to high throughput and the ability to obtain the necessary intensity to discriminate phases at both trace and major element concentrations. It is desirable to produce fully quantitative compositional maps of geological materials, which requires the acquisition of k-ratio maps that are background and dead-time corrected, and which have been corrected by phi(delta z> or an equivalent algorithm at each pixel. To date, turnkey systems do not allow the acquisition of k-ratio maps and the rigorous correction in this manner. X-ray maps of a chondrule from the Ourique meteorite, and a comb-layered xenolith from the San Francisco volcanic field, have been analyzed and processed to extract phase information. The Ourique meteorite presents a challenge due to relatively low BSE contrast, and has been studied using spectrum imaging. X-ray maps for Si, Mg, and FeK(alpha) were used to produce RGB images. The xenolith sample contains sector-zoned augite, olivine, plagioclase, and basaltic glass. X-ray maps were processed using Lispix and ImageJ software to produce mineral phase maps. The x-ray maps for Mg, Ca, and Ti were used with traceback to generate binary images that were converted to RGB images. These approaches are successful in discriminating phases, but it is desirable to achieve the methods that were used on lunar samples 30 years ago on current microprobe systems. Curnt research includes x-ray mapping analysis of the Dalgety Downs chondrite by micro x-ray fluorescence and spectrum imaging, in collaboration with Kenny Witherspoon of IXRF Systems and Dale Newbury of NIST.