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NASA NTRS2004

Molecular Microbial Analyses of the Mars Exploration Rovers Assembly Facility

During space exploration, the control of terrestrial microbes associated with robotic space vehicles intended to land on extraterrestrial solar system bodies is necessary to prevent forward contamination and maintain scientific integrity during the search for life. Microorganisms associated with the spacecraft assembly environment can be a source of contamination for the spacecraft. In this study, we have monitored the microbial burden of air samples of the Mars Exploration Rovers' assembly facility at the Kennedy Space Center utilizing complementary diagnostic tools. To estimate the microbial burden and identify potential contaminants in the assembly facility, several microbiological techniques were used including culturing, cloning and sequencing of 16S rRNA genes, DNA microarray analysis, and ATP assays to assess viable microorganisms. Culturing severely underestimated types and amounts of contamination since many of the microbes implicated by molecular analyses were not cultivable. In addition to the cultivation of Agrobacterium, Burkholderia and Bacillus species, the cloning approach retrieved 16s rDNA sequences of oligotrophs, symbionts, and y-proteobacteria members. DNA microarray analysis based on rational probe design and dissociation curves complemented existing molecular techniques and produced a highly parallel, high resolution analysis of contaminating microbial populations. For instance, strong hybridization signals to probes targeting the Bacillus species indicated that members of this species were present in the assembly area samples; however, differences in dissociation curves between perfect-match and air sample sequences showed that these samples harbored nucleotide polymorphisms. Vegetative cells of several isolates were resistant when subjected to treatments of UVC (254 nm) and vapor H202 (4 mg/L). This study further validates the significance of non-cultivable microbes in association with spacecraft assembly facilities, as our analyses have identified several non-cultivable microbes likely to contaminate the surfaces of spacecraft hardware.

microbial diversity MER 16S rDNA DNA microarray sp↗
NASA NTRS2006

A Comprehensive Assessment of Biologicals Contained Within Commercial Airliner Cabin Air

Both culture-based and culture-independent, biomarker-targeted microbial enumeration and identification technologies were employed to estimate total microbial and viral burden and diversity within the cabin air of commercial airliners. Samples from each of twenty flights spanning three commercial carriers were collected via air-impingement. When the total viable microbial population was estimated by assaying relative concentrations of the universal energy carrier ATP, values ranged from below detection limits (BDL) to 4.1 x 106 cells/cubic m of air. The total viable microbial population was extremely low in both of Airline A (approximately 10% samples) and C (approximately 18% samples) compared to the samples collected aboard flights on Airline A and B (approximately 70% samples). When samples were collected as a function of time over the course of flights, a gradual accumulation of microbes was observed from the time of passenger boarding through mid-flight, followed by a sharp decline in microbial abundance and viability from the initiation of descent through landing. It is concluded in this study that only 10% of the viable microbes of the cabin air were cultivable and suggested a need to employ state-of-the art molecular assay that measures both cultivable and viable-but-non-cultivable microbes. Among the cultivable bacteria, colonies of Acinetobacter sp. were by far the most profuse in Phase I, and Gram-positive bacteria of the genera Staphylococcus and Bacillus were the most abundant during Phase II. The isolation of the human pathogens Acinetobacter johnsonii, A. calcoaceticus, Janibacter melonis, Microbacterium trichotecenolyticum, Massilia timonae, Staphylococcus saprophyticus, Corynebacterium lipophiloflavum is concerning, as these bacteria can cause meningitis, septicemia, and a handful of sometimes fatal diseases and infections. Molecular microbial community analyses exhibited presence of the alpha-, beta-, gamma-, and delta- proteobacteria, as well as Gram-positive bacteria, Fusobacteria, Cyanobacteria, Deinococci, Bacterioidetes, Spirochetes, and Planctomyces in varying abundance. Neisseria meningitidis rDNA sequences were retrieved in great abundance from Airline A followed by Streptococcus oralis/mitis sequences. Pseudomonas synxantha sequences dominated Airline B clone libraries, followed by those of N. meningitidis and S. oralis/mitis. In Phase II, Airline C, sequences representative of more than 113 species, enveloping 12 classes of bacteria, were retrieved. Proteobacterial sequences were retrieved in greatest frequency (58% of all clone sequences), followed in short order by those stemming from Gram-positives bacteria (31% of all clone sequences). As for overall phylogenetic breadth, Gram-positive and alpha-proteobacteria seem to have a higher affinity for international flights, whereas beta-and gamma-proteobacteria are far more common about domestic cabin air parcels in Airline C samples. Ultimately, the majority of microbial species circulating throughout the cabin airs of commercial airliners are commensal, infrequently pathogenic normal flora of the human nasopharynx and respiratory system. Many of these microbes likely originate from the oral and nasal cavities, and lungs of passengers and flight crew and are disseminated unknowingly via routine conversation, coughing, sneezing, and stochastic passing of fomites. The data documented in this study will be useful to generate a baseline microbial population database and can be utilized to develop biosensor instrumentation for monitoring microbial quality of cabin or urban air.

microbial diversity↗
NASA NTRS2008

Western Aeronautical Test Range

NASA's Western Aeronautical Test Range (WATR) is a network of facilities used to support aeronautical research, science missions, exploration system concepts, and space operations. The WATR resides at NASA's Dryden Flight Research Center located at Edwards Air Force Base, California. The WATR is a part of NASA's Corporate Management of Aeronautical Facilities and funded by the Strategic Capability Asset Program (SCAP). It is managed by the Aeronautics Test Program (ATP) of the Aeronautics Research Mission Directorate (ARMD) to provide the right facility at the right time. NASA is a tenant on Edwards Air Force Base and has an agreement with the Air Force Flight Test Center to use the land and airspace controlled by the Department of Defense (DoD). The topics include: 1) The WATR supports a variety of vehicles; 2) Dryden shares airspace with the AFFTC; 3) Restricted airspace, corridors, and special use areas are available for experimental aircraft; 4) WATR Products and Services; 5) WATR Support Configuration; 6) Telemetry Tracking; 7) Time Space Positioning; 8) Video; 9) Voice Communication; 10) Mobile Operations Facilities; 11) Data Processing; 12) Mission Control Center; 13) Real-Time Data Analysis; and 14) Range Safety.

Sakahara, Robert D.↗
NASA NTRS2008

NASA Tech Briefs, October 2008

Topics covered include: Control Architecture for Robotic Agent Command and Sensing; Algorithm for Wavefront Sensing Using an Extended Scene; CO2 Sensors Based on Nanocrystalline SnO2 Doped with CuO; Improved Airborne System for Sensing Wildfires; VHF Wide-Band, Dual-Polarization Microstrip-Patch Antenna; Onboard Data Processor for Change-Detection Radar Imaging; Using LDPC Code Constraints to Aid Recovery of Symbol Timing; System for Measuring Flexing of a Large Spaceborne Structure; Integrated Formation Optical Communication and Estimation System; Making Superconducting Welds between Superconducting Wires; Method for Thermal Spraying of Coatings Using Resonant-Pulsed Combustion; Coating Reduces Ice Adhesion; Hybrid Multifoil Aerogel Thermal Insulation; SHINE Virtual Machine Model for In-flight Updates of Critical Mission Software; Mars Image Collection Mosaic Builder; Providing Internet Access to High-Resolution Mars Images; Providing Internet Access to High-Resolution Lunar Images; Expressions Module for the Satellite Orbit Analysis Program Virtual Satellite; Small-Body Extensions for the Satellite Orbit Analysis Program (SOAP); Scripting Module for the Satellite Orbit Analysis Program (SOAP); XML-Based SHINE Knowledge Base Interchange Language; Core Technical Capability Laboratory Management System; MRO SOW Daily Script; Tool for Inspecting Alignment of Twinaxial Connectors; An ATP System for Deep-Space Optical Communication; Polar Traverse Rover Instrument; Expert System Control of Plant Growth in an Enclosed Space; Detecting Phycocyanin-Pigmented Microbes in Reflected Light; DMAC and NMP as Electrolyte Additives for Li-Ion Cells; Mass Spectrometer Containing Multiple Fixed Collectors; Waveguide Harmonic Generator for the SIM; Whispering Gallery Mode Resonator with Orthogonally Reconfigurable Filter Function; Stable Calibration of Raman Lidar Water-Vapor Measurements; Bimaterial Thermal Compensators for WGM Resonators; Root Source Analysis/ValuStream[Trade Mark] - A Methodology for Identifying and Managing Risks; Ensemble: an Architecture for Mission-Operations Software; Object Recognition Using Feature-and Color-Based Methods; On-Orbit Multi-Field Wavefront Control with a Kalman Filter; and The Interplanetary Overlay Networking Protocol Accelerator.

Source record↗
NASA NTRS2009

Sensitive, Rapid Detection of Bacterial Spores

A method of sensitive detection of bacterial spores within delays of no more than a few hours has been developed to provide an alternative to a prior three-day NASA standard culture-based assay. A capability for relatively rapid detection of bacterial spores would be beneficial for many endeavors, a few examples being agriculture, medicine, public health, defense against biowarfare, water supply, sanitation, hygiene, and the food-packaging and medical-equipment industries. The method involves the use of a commercial rapid microbial detection system (RMDS) that utilizes a combination of membrane filtration, adenosine triphosphate (ATP) bioluminescence chemistry, and analysis of luminescence images detected by a charge-coupled-device camera. This RMDS has been demonstrated to be highly sensitive in enumerating microbes (it can detect as little as one colony-forming unit per sample) and has been found to yield data in excellent correlation with those of culture-based methods. What makes the present method necessary is that the specific RMDS and the original protocols for its use are not designed for discriminating between bacterial spores and other microbes. In this method, a heat-shock procedure is added prior to an incubation procedure that is specified in the original RMDS protocols. In this heat-shock procedure (which was also described in a prior NASA Tech Briefs article on enumerating sporeforming bacteria), a sample is exposed to a temperature of 80 C for 15 minutes. Spores can survive the heat shock, but nonspore- forming bacteria and spore-forming bacteria that are not in spore form cannot survive. Therefore, any colonies that grow during incubation after the heat shock are deemed to have originated as spores.

Kern, Roger G.↗
NASA NTRS2009

Partnership for the Revitalization of National Wind Tunnel Force Measurement Capability

Lack of funding and lack of focus on research over the past several years, coupled with force measurement capabilities being decentralized and distributed across the National Aeronautics and Space Administration (NASA) research centers, has resulted in a significant erosion of (1) capability and infrastructure to produce and calibrate force measurement systems; (2) NASA s working knowledge of those systems; and (3) the quantity of high-quality, full-capability force measurement systems available for use in aeronautics testing. Simultaneously, and at proportional rates, the capability of industry to design, manufacture, and calibrate these test instruments has been eroding primarily because of a lack of investment by the aeronautics community. Technical expertise in this technology area is a core competency in aeronautics testing; it is highly specialized and experience-based, and it represents a niche market for only a few small precision instrument shops in the United States. With this backdrop, NASA s Aeronautics Test Program (ATP) chartered a team to examine the issues and risks associated with the problem, focusing specifically on strain- gage balances. The team partnered with the U.S. Air Force s Arnold Engineering Development Center (AEDC) to exploit their combined capabilities and take a national level government view of the problem. This paper describes the team s approach, its findings, and its recommendations, and the current status for revitalizing the government s balance capability with respect to designing, fabricating, calibrating, and using the instruments.

Rhew, Ray D.↗
NASA NTRS2009

Ares V: A National Launch Asset for the 21st Century

NASA is designing the Ares V as the cargo launch vehicle to carry NASA's exploration plans into the 21st century. The Ares V is the heavy-lift component of NASA's dual-launch architecture that will replace the current space shuttle fleet, complete the International Space Station, and establish a permanent human presence on the Moon as a stepping stone to destinations beyond. During extensive independent and internal architecture and vehicle trade studies as part of the Exploration Systems Architecture Study, NASA selected the Ares I crew launch vehicle and the Ares V to support future exploration. The smaller Ares I will launch the Orion crew exploration vehicle with four to six astronauts into orbit. The Ares V is designed to carry the Altair lunar lander into orbit, rendezvous with Orion, and send the mated spacecraft toward lunar orbit. The Ares V will be the largest and most powerful launch vehicle in history, providing unprecedented payload mass and volume to establish a permanent lunar outpost and explore significantly more of the lunar surface than was done during the Apollo missions. The Ares V also represents a national asset offering opportunities for new science, national security, and commercial missions of unmatched size and scope. Using the dual-launch Earth Orbit Rendezvous approach, the Ares I and Ares V together will be able to inject roughly 57percent more mass to the Moon than the Apollo-era Saturn V. Ares V alone will be able to send nearly 414,000 pounds into low Earth orbit (LEO) or more than 138,000 pounds directly to the Moon, compared with 262,000 pounds and 99,000 pounds, respectively for the Saturn V. Significant progress has been made on the Ares V to support a planned fiscal 2011 authority-to-proceed (ATP) milestone. This paper discusses recent progress on the Ares V and planned future activities.

Sumrall, Phil↗
NASA NTRS2006

Aerocapture Technologies

Aeroassist technology development is a vital part of the NASA In-Space Propulsion Technology (ISPT) Program. One of the main focus areas of ISPT is aeroassist technologies through the Aerocapture Technology (AT) Activity. Within the ISPT, the current aeroassist technology development focus is aerocapture. Aerocapture relies on the exchange of momentum with an atmosphere to achieve thrust, in this case a decelerating thrust leading to orbit capture. Without aerocapture, a substantial propulsion system would be needed on the spacecraft to perform the same reduction of velocity. This could cause reductions in the science payload delivered to the destination, increases in the size of the launch vehicle (to carry the additional fuel required for planetary capture) or could simply make the mission impossible due to additional propulsion requirements. The AT is advancing each technology needed for the successful implementation of aerocapture in future missions. The technology development focuses on both rigid aeroshell systems as well as the development of inflatable aerocapture systems, advanced aeroshell performance sensors, lightweight structure and higher temperature adhesives. Inflatable systems such as tethered trailing ballutes ('balloon parachutes'), clamped ballutes, and inflatable aeroshells are also under development. Aerocapture-specific computational tools required to support future aerocapture missions are also an integral part of the ATP. Tools include: engineering reference atmosphere models, guidance and navigation, aerothermodynamic modeling, radiation modeling and flight simulation. Systems analysis plays a key role in the AT development process. The NASA in-house aerocapture systems analysis team has been taken with multiple systems definition and concept studies to complement the technology development tasks. The team derives science requirements, develops guidance and navigation algorithms, as well as engineering reference atmosphere models and aeroheating specifications. The study team also creates designs for the overall mission spacecraft. Presentation slides are provided to further describe the aerocapture project.

Keys, Andrew S.↗
NASA NTRS2008

Update on the Ares V to Support Heavy Lift for U.S. Space Exploration Policy

When NASA's Ares V cargo launch vehicle begins flying late next decade, its capabilities will significantly exceed the 1960s-era Saturn V. It will send more crew and cargo to more places on the lunar surface than Apollo and provide ongoing support to a permanent lunar outpost that will open the Moon to greater exploration, science and adventure than ever before. Moreover, it will restore the United States heavy-lift capability, which can support human and robotic exploration for decades to come. Ares V remains in a pre-design analysis cycle stage pending a planned Authority to Proceed (ATP) in late 2010. Ares V benefits from the decision to draw from heritage hardware and its commonality with the Ares I crew launch vehicle, which completed its preliminary design review (PDR) in September 2008. Most of the work on Ares V to date has been focused on refining the vehicle design through a variety of internal studies. This paper will provide background information on the Ares V evolution, emphasizing the vehicle configuration as it exists today.

Sumrall, John P.↗
NASA NTRS2009

Ares V: Game Changer for National Security Launch

NASA is designing the Ares V cargo launch vehicle to vastly expand exploration of the Moon begun in the Apollo program and enable the exploration of Mars and beyond. As the largest launcher in history, Ares V also represents a national asset offering unprecedented opportunities for new science, national security, and commercial missions of unmatched size and scope. The Ares V is the heavy-lift component of NASA's dual-launch architecture that will replace the current space shuttle fleet, complete the International Space Station, and establish a permanent human presence on the Moon as a stepping-stone to destinations beyond. During extensive independent and internal architecture and vehicle trade studies as part of the Exploration Systems Architecture Study (ESAS), NASA selected the Ares I crew launch vehicle and the Ares V to support future exploration. The smaller Ares I will launch the Orion crew exploration vehicle with four to six astronauts into orbit. The Ares V is designed to carry the Altair lunar lander into orbit, rendezvous with Orion, and send the mated spacecraft toward lunar orbit. The Ares V will be the largest and most powerful launch vehicle in history, providing unprecedented payload mass and volume to establish a permanent lunar outpost and explore significantly more of the lunar surface than was done during the Apollo missions. The Ares V consists of a Core Stage, two Reusable Solid Rocket Boosters (RSRBs), Earth Departure Stage (EDS), and a payload shroud. For lunar missions, the shroud would cover the Lunar Surface Access Module (LSAM). The Ares V Core Stage is 33 feet in diameter and 212 feet in length, making it the largest rocket stage ever built. It is the same diameter as the Saturn V first stage, the S-IC. However, its length is about the same as the combined length of the Saturn V first and second stages. The Core Stage uses a cluster of five Pratt & Whitney Rocketdyne RS-68B rocket engines, each supplying about 700,000 pounds of thrust. Its propellants are liquid hydrogen and liquid oxygen. The two solid rocket boosters provide about 3.5 million pounds of thrust at liftoff. These 5.5-segment boosters are derived from the 4-segment boosters now used on the Space Shuttle, and are similar to those used in the Ares I first stage. The EDS is powered by one J-2X engine. The J-2X, which has roughly 294,000 pounds of thrust, also powers the Ares I Upper Stage. It is derived from the J-2 that powered the Saturn V second and third stages. The EDS performs two functions. Its initial suborbital burns will place the lunar lander into a stable Earth orbit. After the Orion crew vehicle, launched separately on an Ares I, docks with the lander/EDS stack, EDS will ignite a second time to put the combined 65-metric ton vehicle into a lunar transfer orbit. When it stands on the launch pad at Kennedy Space Center late in the next decade, the Ares V stack will be approximately 381 feet tall and have a gross liftoff mass of 8.1 million pounds. The current point-of-departure design exceeds Saturn V s mass capability by approximately 40 percent. Using the current payload shroud design, Ares V can carry 315,000 pounds to 29-degree low Earth orbit (LEO) or 77,000 pounds to a geosynchronous orbit. Another unique aspect of the Ares V is the 33-foot-diameter payload shroud, which encloses approximately 30,400 cubic feet of usable volume. A larger hypothetical shroud for encapsulating larger payloads has been studied. While Ares V makes possible larger payload masses and volumes, it may alternately make possible more cost-effective mission design if the relevant payload communities are willing to consider an alternative to the existing approach that has driven them to employ complexity to solve current launch vehicle mass and volume constraints. By using Ares V s mass and volume capabilities as margin, payload designers stand to reduce development risk and cost. Significant progress has been made on the Ares V to support a plaed fiscal 2011 authority-to-proceed (ATP) milestone. The Ares V team is actively reaching out to external organizations during this early concept phase to ensure that the Ares V vehicle can be leveraged for national security, science, and commercial development needs. This presentation will discuss Ares V vehicle configuration, the path to the current concept, accomplishments to date, and potential payload utilization opportunities.

Sumrall, Phil↗
NASA NTRS2010

Update: Partnership for the Revitalization of National Wind Tunnel Force Measurement Technology Capability

NASA's Aeronautics Test Program (ATP) chartered a team to examine the issues and risks associated with the lack of funding and focus on force measurement over the past several years, focusing specifically on strain-gage balances. NASA partnered with the U.S. Air Force's Arnold Engineering Development Center (AEDC) to exploit their combined capabilities and take a national level government view of the problem and established the National Force Measurement Technology Capability (NFMTC) project. This paper provides an update on the team's status for revitalizing the government's balance capability with respect to designing, fabricating, calibrating, and using the these critical measurement devices.

Rhew, Ray D.↗
NASA NTRS2010

Field Analysis of Microbial Contamination Using Three Molecular Methods in Parallel

Advanced technologies with the capability of detecting microbial contamination remain an integral tool for the next stage of space agency proposed exploration missions. To maintain a clean, operational spacecraft environment with minimal potential for forward contamination, such technology is a necessity, particularly, the ability to analyze samples near the point of collection and in real-time both for conducting biological scientific experiments and for performing routine monitoring operations. Multiple molecular methods for detecting microbial contamination are available, but many are either too large or not validated for use on spacecraft. Two methods, the adenosine- triphosphate (ATP) and Limulus Amebocyte Lysate (LAL) assays have been approved by the NASA Planetary Protection Office for the assessment of microbial contamination on spacecraft surfaces. We present the first parallel field analysis of microbial contamination pre- and post-cleaning using these two methods as well as universal primer-based polymerase chain reaction (PCR).

Morris, H.↗
NASA NTRS2009

Modeling Guidelines for Code Generation in the Railway Signaling Context

Modeling guidelines constitute one of the fundamental cornerstones for Model Based Development. Their relevance is essential when dealing with code generation in the safety-critical domain. This article presents the experience of a railway signaling systems manufacturer on this issue. Introduction of Model-Based Development (MBD) and code generation in the industrial safety-critical sector created a crucial paradigm shift in the development process of dependable systems. While traditional software development focuses on the code, with MBD practices the focus shifts to model abstractions. The change has fundamental implications for safety-critical systems, which still need to guarantee a high degree of confidence also at code level. Usage of the Simulink/Stateflow platform for modeling, which is a de facto standard in control software development, does not ensure by itself production of high-quality dependable code. This issue has been addressed by companies through the definition of modeling rules imposing restrictions on the usage of design tools components, in order to enable production of qualified code. The MAAB Control Algorithm Modeling Guidelines (MathWorks Automotive Advisory Board)[3] is a well established set of publicly available rules for modeling with Simulink/Stateflow. This set of recommendations has been developed by a group of OEMs and suppliers of the automotive sector with the objective of enforcing and easing the usage of the MathWorks tools within the automotive industry. The guidelines have been published in 2001 and afterwords revisited in 2007 in order to integrate some additional rules developed by the Japanese division of MAAB [5]. The scope of the current edition of the guidelines ranges from model maintainability and readability to code generation issues. The rules are conceived as a reference baseline and therefore they need to be tailored to comply with the characteristics of each industrial context. Customization of these recommendations has been performed for the automotive control systems domain in order to enforce code generation [7]. The MAAB guidelines have been found profitable also in the aerospace/avionics sector [1] and they have been adopted by the MathWorks Aerospace Leadership Council (MALC). General Electric Transportation Systems (GETS) is a well known railway signaling systems manufacturer leading in Automatic Train Protection (ATP) systems technology. Inside an effort of adopting formal methods within its own development process, GETS decided to introduce system modeling by means of the MathWorks tools [2], and in 2008 chose to move to code generation. This article reports the experience performed by GETS in developing its own modeling standard through customizing the MAAB rules for the railway signaling domain and shows the result of this experience with a successful product development story.

Ferrari, Alessio↗
NASA NTRS2001

Stabilized NADH as a Countermeasure for Jet Lag

Current remedies for jet lag (phototherapy, melatonin, stimulant, and sedative medications) are limited in efficacy and practicality. The efficacy of a stabilized, sublingual form of reduced nicotin amide adenine dinucleotide (NADH, ENADAlert, Menuco Corp.) as a countermeasure for jet lag was examined. Because NADH increases cellular production of ATP and facilitates dopamine synthesis, it may counteract the effects of jet lag on cognitive functioning and sleepiness. Thirty-five healthy, employed subjects participated in this double-blind, placebo-controlled study. Training and baseline testing were conducted on the West Coast before subjects flew overnight to the East Coast, where they would experience a 3-hour time difference. Upon arrival, individuals were randomly assigned to receive either 20 mg of sublingual stabilized ADH (n=18) or identical placebo tablets (n=17). All participants completed computer-administered tests (including CogScreen7) to assess changes in cognitive functioning, mood, and sleepiness in the morning and afternoon. Jet lag resulted in increased sleepiness for over half the participants and deterioration of cognitive functioning for approximately one third. The morning following the flight, subjects experienced lapses of attention in addition to disruptions in working memory, divided attention, and visual perceptual speed. Individuals who received NADH performed significantly better on 5 of 8 cognitive and psychomotor test measures (P less than or equal to 0.5) and showed a trend for better performance on the other three measures (P less than or equal to .l0). Subjects also reported less sleepiness compared with those who received placebo. No adverse effects were observed with NADH treatment. Stabilized NADH significantly reduced jet lag-induced disruptions of cognitive functioning, was easily administered, and was found to have no adverse side effects.

Kay, Gary G.↗
NASA NTRS2004

Liquid-Crystal Thermosets, a New Generation of High-Performance Liquid-Crystal Polymers

One of the major challenges for NASA's next-generation reusable-launch-vehicle (RLV) program is the design of a cryogenic lightweight composite fuel tank. Potential matrix resin systems need to exhibit a low coefficient of thermal expansion (CTE), good mechanical strength, and excellent barrier properties at cryogenic temperatures under load. In addition, the resin system needs to be processable by a variety of non-autoclavable techniques, such as vacuum-bag curing, resin-transfer molding (RTM), vacuum-assisted resin-transfer molding (VaRTM), resin-film infusion (RFI), pultrusion, and advanced tow placement (ATP). To meet these requirements, the Advanced Materials and Processing Branch (AMPB) at NASA Langley Research Center developed a new family of wholly aromatic liquid-crystal oligomers that can be processed and thermally cross-linked while maintaining their liquid-crystal order. All the monomers were polymerized in the presence of a cross-linkable unit by use of an environmentally benign melt-condensation technique. This method does not require hazardous solvents, and the only side product is acetic acid. The final product can be obtained as a powder or granulate and has an infinite shelf life. The obtained oligomers melt into a nematic phase and do not exhibit isotropization temperatures greater than the temperatures of decomposition (Ti > T(sub dec)). Three aromatic formulations were designed and tested and included esters, ester-amides, and ester-imides. One of the major advantages of this invention, named LaRC-LCR or Langley Research Center-Liquid Crystal Resin, is the ability to control a variety of resin characteristics, such as melting temperature, viscosity, and the cross-link density of the final part. Depending on the formulation, oligomers can be prepared with melt viscosities in the range of 10-10,000 poise (100 rad/s), which can easily be melt-processed using a variety of composite-processing techniques. This capability provides NASA with custom-made matrix resins that meet the required processing conditions for the fabrication of textile composites. Once the resin is in place, the temperature is raised to 375 C and the oligomers are cross-linked into a high-glass-transition-temperature (Tg) nematic network without releasing volatiles. The mechanical properties of the fully crosslinked, composite articles are comparable to typical composites based on commercially available epoxy resins.

Dingemans, Theo↗
NASA NTRS2003

Atmospheric-Fade-Tolerant Tracking and Pointing in Wireless Optical Communication

An acquisition, tracking, and pointing (ATP) system, under development at the time of reporting the information for this article, is intended to enable a terminal in a free-space optical communication system to continue to aim its transmitting laser beam toward a receiver at a remote terminal when the laser beacon signal from the remote terminal temporarily fades or drops out of sight altogether. Such fades and dropouts can be caused by adverse atmospheric conditions (e.g., rain or clouds). They can also occur when intervening objects block the line of sight between terminals as a result of motions of those objects or of either or both terminals

Ortiz, Gerardo↗
NASA NTRS2012

Fabrication and Testing of CERMET Fuel Materials for Nuclear Thermal Propulsion

A first generation Nuclear Cryogenic Propulsion Stage (NCPS) based on Nuclear Thermal Propulsion (NTP) is currently being developed for Advanced Space Exploration Systems. The overall goal of the project is to address critical NTP technology challenges and programmatic issues to establish confidence in the affordability and viability of NTP systems. The current technology roadmap for NTP identifies the development of a robust fuel form as a critical near term need. The lack of a qualified nuclear fuel is a significant technical risk that will require a considerable fraction of program resources to mitigate. Due to these risks and the cost for qualification, the development and selection of a primary fuel must begin prior to Authority to Proceed (ATP) for a specific mission. The fuel development is a progressive approach to incrementally reduce risk, converge the fuel materials, and mature the design and fabrication process of the fuel element. A key objective of the current project is to advance the maturity of CERMET fuels. The work includes fuel processing development and characterization, fuel specimen hot hydrogen screening, and prototypic fuel element testing. Early fuel materials development is critical to help validate requirements and fuel performance. The purpose of this paper is to provide an overview and status of the work at Marshall Space Flight Center (MSFC).

Hickman, Robert↗
NASA NTRS2012

Antimicrobial Materials for Advanced Microbial Control in Spacecraft Water Systems

Microbial detection, identification, and control are essential for the maintenance and preservation of spacecraft water systems. Requirements set by NASA put limitations on the energy, mass, materials, noise, cost, and crew time that can be devoted to microbial control. Efforts are being made to attain real-time detection and identification of microbial contamination in microgravity environments. Research for evaluating technologies for capability enhancement on-orbit is currently focused on the use of adenosine triphosphate (ATP) analysis for detection purposes and polymerase chain reaction (peR) for microbial identification. Additional research is being conducted on how to control for microbial contamination on a continual basis. Existing microbial control methods in spacecraft utilize iodine or ionic silver biocides, physical disinfection, and point-of-use sterilization filters. Although these methods are effective, they require re-dosing due to loss of efficacy, have low human toxicity thresholds, produce poor taste, and consume valuable mass and crew time. Thus, alternative methods for microbial control are needed. This project also explores ultraviolet light-emitting diodes (UV-LEDs), surface passivation methods for maintaining residual biocide levels, and several antimicrobial materials aimed at improving current microbial control techniques, as well as addressing other materials presently under analysis and future directions to be pursued.

Birmele, Michele↗