Developing Sustainable Spacecraft Water Management Systems

It is well recognized that water handling systems used in a spacecraft are prone to failure caused by biofouling and mineral scaling, which can clog mechanical systems and degrade the performance of capillary-based technologies. Long duration spaceflight applications, such as extended stays at a Lunar Outpost or during a Mars transit mission, will increasingly benefit from hardware that is generally more robust and operationally sustainable overtime. This paper presents potential design and testing considerations for improving the reliability of water handling technologies for exploration spacecraft. Our application of interest is to devise a spacecraft wastewater management system wherein fouling can be accommodated by design attributes of the management hardware, rather than implementing some means of preventing its occurrence

Enhanced Simulation of Partial Gravity for Extravehicular Activity

Prior studies of human locomotion under simulated partial gravity have hypothesized that energy expenditure is increased in lunar gravity, as compared to that of Mars. This may be due to subjects having to expend excess energy for stability and posture control in the lower gravitational field. The physiological cause of this suspected ‘‘wasted energy’’ during locomotion in low gravity remains to be determined. This paper outlines factors to be considered for these analyses and enhancements to the simulation method that will enable assessment of inertial stability and associated metabolic cost. A novel simulation technique is proposed for assessing the effects of inertial rotation and variable mass on stability, metabolic cost, and biomechanics using a modified weight relief harness to simulate partial gravity. Peer review of this article was completed in 2005, but the print version was not published on its original schedule. This article represents the first publication of the work originally submitted to JHPEE

Gene Expression Profiling of Islet Cell Subtypes

Abstract Pancreatic endocrine cells are co-located into clusters called the islets of Langerhans that are comprised of glucagon producing alpha cells, insulin secreting beta cells, somatostatin generating delta cells, and other cell types. Type 1 diabetes results from an autoimmune process in which autoreactive T cells destroy the insulin producing beta cells, requiring the patient to inject insulin to regulate their blood glucose levels. Thus far, attempts to cure diabetes via islet transplantation have been limited by insufficient donor supply, inconsistent isolated islet quality, continued autoimmunity, alloimmune rejection, and limited beta cell regeneration. Diabetes research has focused on preventing the autoimmune response, promoting stem cell to beta cell differentiation, and defining the factors that influence beta cell proliferation. Islet research, in turn, has been limited to whole islet studies since, isolating the islet cell subtypes has not been possible. Using a method recently developed for mouse islet cells (Pechhold et al. Nat Biotechnol. 2009 Nov; 27(11):1038-42), that uses intracellular hormone staining and flow cytometry, we are able to sort human islets into populations uniquely expressing glucagon, insulin, or somatostatin. Further, we have developed a human gene array to measure candidate gene expression using a quantitative nuclease protection assay (qNPA). This technique uses 50 base oligomers that specifically recognize RNA from each gene of interest, overcoming limitations caused by the harsh conditions required for intracellular staining. We report gene expression analysis for specific hormones and transcription factors expressed in each islet cell population. We are further modifying this technique to study nonhuman primate islets, and investigate the specific proteome and miRNA profiles for individual islet cell populations. The goal of these studies is to characterize the genetic differences between the islet cell populations and understand which factors control beta cell regeneration and proliferation. We have shown that we can purify adult human islets into individual cellular populations. This is the first step in understanding the genetic and environmental components that regulate increased beta cell proliferation and beta cell mass. In the absence of full-length mRNA for RT-PCR or next generation sequencing, the qNPA technique provides candidate gene expression profiles for these cells

Spacecraft Design Considerations for Piloted Reentry and Landing

With the end of the Space Shuttle era anticipated in this decade and the requirements for the Crew Exploration Vehicle (CEV) now being defined, an opportune window exists for incorporating 'lessons learned' from relevant aircraft and space flight experience into the early stages of designing the next generation of human spacecraft. This includes addressing not only the technological and overall mission challenges, but also taking into account the comprehensive effects that space flight has on the pilot, all of which must be balanced to ensure the safety of the crew. This manuscript presents a unique and timely overview of a multitude of competing, often unrelated, requirements and constraints governing spacecraft design that must be collectively considered in order to ensure the success of future space exploration missions

Observational Constraints on Submillimeter Dust Opacity

Infrared extinction maps and submillimeter dust continuum maps are powerful probes of the density structure in the envelope of star-forming cores. We make a direct comparison between infrared and submillimeter dust continuum observations of the low-mass Class 0 core, B335, to constrain the ratio of submillimeter to infrared opacity (κ_(smm)/κ_(ir)) and the submillimeter opacity power-law index (κ ∝ λ–β). Using the average value of theoretical dust opacity models at 2.2 μm, we constrain the dust opacity at 850 and 450 μm. Using new dust continuum models based upon the broken power-law density structure derived from interferometric observations of B335 and the infall model derived from molecular line observations of B335, we find that the opacity ratios are ^κ_(850)_κ_(2.2) = (3.21 - 4.80)^(+0.44)_(-0.30) x 10^(-4) ^κ_(450)_κ(2.0) = (12.8-24.8)^(+2.4)_(-1.3) x 10^(-4) with a submillimeter opacity power-law index of β_(smm) = (2.18-2.58)^(+0.30)_(–0.30). The range of quoted values is determined from the uncertainty in the physical model for B335. For an average 2.2 μm opacity of 3800 ± 700 cm^2 g^(–1), we find a dust opacity at 850 and 450 μm of κ_(850) = (1.18-1.77)^9+0.36)_(–0.24) and κ_(450) = (4.72-9.13)^(+1.9)_(–0.98) cm^2 g^(–1) of dust. These opacities are from (0.65-0.97)κ^(OH5)_(850) of the widely used theoretical opacities of Ossenkopf and Henning for coagulated ice grains with thin mantles at 850 μm

An experimental and theoretical study of transient negative ions in Mg, Zn, Cd and Hg

A range of experimental and theoretical techniques have been applied to the study of transient negative ions (resonances) formed in electron scattering from the Group II metals Mg, Zn, Cd, and Hg at incident electron energies below the first ionization potential. A wealth of resonance structures have been observed and from the experimental observations and theoretical information, classifications are proposed for some of these negative ion states

Developing Abrasion Test Standards for Evaluating Lunar Construction Materials

Operational issues encountered by Apollo astronauts relating to lunar dust were catalogued, including material abrasion that resulted in scratches and wear on spacesuit components, ultimately impacting visibility, joint mobility and pressure retention. Standard methods are being developed to measure abrasive wear on candidate construction materials to be used for spacesuits, spacecraft, and robotics. Calibration tests were conducted using a standard diamond stylus scratch tip on the common spacecraft structure aluminum, Al 6061-T6. Custom tips were fabricated from terrestrial counterparts of lunar minerals for scratching Al 6061-T6 and comparing to standard diamond scratches. Considerations are offered for how to apply standards when selecting materials and developing dust mitigation strategies for lunar architecture elements

Validation of Proposed Metrics for Two-Body Abrasion Scratch Test Analysis Standards: In Principle, Any Scratch Can Be Analyzed by This Method

Abrasion of mechanical components and fabrics by soil on Earth is typically minimized by the effects of atmosphere and water. Potentially abrasive particles lose sharp and pointed geometrical features through erosion. In environments where such erosion does not exist, such as the vacuum of the Moon, particles retain sharp geometries associated with fracturing of their parent particles by micrometeorite impacts. The relationship between hardness of the abrasive and that of the material being abraded is well understood, such that the abrasive ability of a material can be estimated as a function of the ratio of the hardness of the two interacting materials. Knowing the abrasive nature of an environment (abrasive)/construction material is crucial to designing durable equipment for use in such surroundings

Validation of Proposed Metrics for Two-Body Abrasion Scratch Test Analysis Standards

The objective of this work was to evaluate a set of standardized metrics proposed for characterizing a surface that has been scratched from a two-body abrasion test. This is achieved by defining a new abrasion region termed Zone of Interaction (ZOI). The ZOI describes the full surface profile of all peaks and valleys, rather than just measuring a scratch width as currently defined by the ASTM G 171 Standard. The ZOI has been found to be at least twice the size of a standard width measurement, in some cases considerably greater, indicating that at least half of the disturbed surface area would be neglected without this insight. The ZOI is used to calculate a more robust data set of volume measurements that can be used to computationally reconstruct a resultant profile for detailed analysis. Documenting additional changes to various surface roughness parameters also allows key material attributes of importance to ultimate design applications to be quantified, such as depth of penetration and final abraded surface roughness. Data are presented to show that different combinations of scratch tips and abraded materials can actually yield the same scratch width, but result in different volume displacement or removal measurements and therefore, the ZOI method is more discriminating than the ASTM method scratch width. Furthermore, by investigating the use of custom scratch tips for our specific needs, the usefulness of having an abrasion metric that can measure the displaced volume in this standardized manner, and not just by scratch width alone, is reinforced. This benefit is made apparent when a tip creates an intricate contour having multiple peaks and valleys within a single scratch. This work lays the foundation for updating scratch measurement standards to improve modeling and characterization of three-body abrasion test results