Flash X-ray technique for recession measurements in ablating models.
Flash X ray unit with special film transport devices to obtain sequenced dynamic radiographs of ablating models during reentry simulation tests
Kassel, P. C., Jr.↗
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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Automated fabrication of back surface field silicon solar cells with screen printed wraparound contacts
The development of a process for fabricating 2 x 4 cm back surface field silicon solar cells having screen printed wraparound contacts is described. This process was specifically designed to be amenable for incorporation into the automated nonvacuum production line. Techniques were developed to permit the use of screen printing for producing improved back surface field structures, wraparound dielectric layers, and wraparound contacts. The optimized process sequence was then used to produce 1852 finished cells. Tests indicated an average conversion efficiency of 11% at AMO and 28 C, with an average degradation of maximum power output of 1.5% after boiling water immersion or thermal shock cycling. Contact adherence was satisfactory after these tests, as well as long term storage at high temperature and high humidity.
Thornhill, J. W.↗
Further laboratory studies and stratospheric flight of a mass spectrometer beam system
A gas expansion system combined with a mass spectrometer has been tested and flown successfully in the stratosphere. Through a sequence of orifices and high speed pumping, gas particles were formed into a molecular beam and analyzed by a sensitive mass spectrometer. During two balloon flights, vertical profiles of all major atmospheric constituents as well as O3, CO2, H2O and others were obtained. Gases such as AR38 and O16;O17 provided in-flight calibration standards. The sensitivity of the system was such that gases with mixing ratios of 10 ppb at an ambient pressure of about 10 mbar were detectable.
Mauersberger, K.↗
Operation and maintenance manual for a preprototype Sabatier carbon dioxide reduction subsystem
The manual delineates the procedures, precautions and necessary sequences of steps required to prepare the package for test, provide troubleshooting information and perform required maintenance by the operating crew. The manual is divided into five sections: Installation, Checkout, Operation, Failure Detection/Isolation and Maintenance.
Kleiner, G. N.↗
Array automated assembly task low cost silicon solar array project, phase 2
Analyses of solar cell and module process steps for throughput rate, cost effectiveness, and reproductibility are reported. In addition to the concentration on cell and module processing sequences, an investigation was made into the capability of using microwave energy in the diffusion, sintering, and thick film firing steps of cell processing. Although the entire process sequence was integrated, the steps are treated individually with test and experimental data, conclusions, and recommendations.
Olson, C.↗
Globular cluster luminosity functions
The use of luminosity functions in determining the helium content, age, and initial mass function of globular clusters, and in testing the stellar structure theory is reviewed. The main sequence turnoff and subgiant phases are examined. The Thomas (1967) peak in the luminosity function and the gap near the base of the giant branch of globular clusters found in the CM are discussed as probes of stellar structure. Research in the area of faint star photometry, dealing with the lower main sequence luminosity function and the interplanetary magnetic field is presented.
Demarque, Pierre↗
The growth of small cracks in 4340 steel
A semiempirical crack-growth model incorporating crack-closure effects has been used to predict crack growth rates and total fatigue life in notched specimens of 4340 steel having an initial defect typical of those previously noted in this steel upon subjection to both constant-amplitude and spectrum loadings. Model predictions for fatigue life are found to be in reasonable agreement with experiments and, in particular, the model was able to accurately predict total fatigue life for specimens subjected to the 'Felix/28' spectrum loading sequence on the sole basis of constant-amplitude test test results.
Swain, M. H.↗
Spacecraft command verification: The AI solution
Recently, a knowledge-based approach was used to develop a system called the Command Constraint Checker (CCC) for TRW. CCC was created to automate the process of verifying spacecraft command sequences. To check command files by hand for timing and sequencing errors is a time-consuming and error-prone task. Conventional software solutions were rejected when it was estimated that it would require 36 man-months to build an automated tool to check constraints by conventional methods. Using rule-based representation to model the various timing and sequencing constraints of the spacecraft, CCC was developed and tested in only three months. By applying artificial intelligence techniques, CCC designers were able to demonstrate the viability of AI as a tool to transform difficult problems into easily managed tasks. The design considerations used in developing CCC are discussed and the potential impact of this system on future satellite programs is examined.
Fesq, Lorraine M.↗
X ray attenuation measurements for high-temperature materials characterization and in-situ monitoring of damage accumulation
The scope of this dissertation is to develop and apply x ray attenuation measurement systems that are capable of: (1) characterizing density variations in high-temperature materials, e.g., monolithic ceramics, ceramic and intermetallic matrix composites, and (2) noninvasively monitoring damage accumulation and failure sequences in ceramic matrix composites under room temperature tensile testing. This dissertation results in the development of: (1) a point scan digital radiography system, and (2) an in-situ x ray material testing system. Radiographic evaluation before, during, and after loading shows the effect of preexisting volume flaws on the fracture behavior of composites. Results show that x ray film radiography can monitor damage accumulation during tensile loading. Matrix cracking, fiber matrix debonding, fiber bridging, and fiber pullout are imaged throughout the tensile loading of the specimens. Further in-situ radiography is found to be a practical technique for estimating interfacial shear strength between the silicon carbide fibers and the reaction bonded silicon nitride matrix. It is concluded that pretest, in-situ, and post test x ray imaging can provide for greater understanding of ceramic matrix composite mechanical behavior.
Baaklini, George Y.↗
EMU processing - A myth dispelled
The refurbishment-and-checkout 'processing' activities entailed by the Space Shuttle Extravehicular Mobility Units (EMUs) are currently significantly more modest, at 1050 man-hours, than when Space Shuttle services began (involving about 4000 man-hours). This great improvement in hardware efficiency is due to the design or modification of test rigs for simplification of procedures, as well as those procedures' standardization, in conjunction with an increase in hardware confidence which has allowed the extension of inspection, service, and testing intervals. Recent simplification of the hardware-processing sequence could reduce EMU processing requirements to 600 man-hours in the near future.
Peacock, Paul R.↗
Knowledge-Based Scheduling of Arrival Aircraft in the Terminal Area
A knowledge based method for scheduling arrival aircraft in the terminal area has been implemented and tested in real time simulation. The scheduling system automatically sequences, assigns landing times, and assign runways to arrival aircraft by utilizing continuous updates of aircraft radar data and controller inputs. The scheduling algorithm is driven by a knowledge base which was obtained in over two thousand hours of controller-in-the-loop real time simulation. The knowledge base contains a series of hierarchical 'rules' and decision logic that examines both performance criteria, such as delay reductions, as well as workload reduction criteria, such as conflict avoidance. The objective of the algorithm is to devise an efficient plan to land the aircraft in a manner acceptable to the air traffic controllers. This paper describes the scheduling algorithms, gives examples of their use, and presents data regarding their potential benefits to the air traffic system.
Krzeczowski, K. J.↗
Characterizing the Preturbulence Environment for Sensor Development, New Hazard Algorithms and NASA Experimental Flight Planning
During the grant period, several tasks were performed in support of the NASA Turbulence Prediction and Warning Systems (TPAWS) program. The primary focus of the research was on characterizing the preturbulence environment by developing predictive tools and simulating atmospheric conditions that preceded severe turbulence. The goal of the research being to provide both dynamical understanding of conditions that preceded turbulence as well as providing predictive tools in support of operational NASA B-757 turbulence research flights. The advancements in characterizing the preturbulence environment will be applied by NASA to sensor development for predicting turbulence onboard commercial aircraft. Numerical simulations with atmospheric models as well as multi-scale observational analyses provided insights into the environment organizing turbulence in a total of forty-eight specific case studies of severe accident producing turbulence on commercial aircraft. These accidents exclusively affected commercial aircraft. A paradigm was developed which diagnosed specific atmospheric circulation systems from the synoptic scale down to the meso-y scale that preceded turbulence in both clear air and in proximity to convection. The emphasis was primarily on convective turbulence as that is what the TPAWS program is most focused on in terms of developing improved sensors for turbulence warning and avoidance. However, the dynamical paradigm also has applicability to clear air and mountain turbulence. This dynamical sequence of events was then employed to formulate and test new hazard prediction indices that were first tested in research simulation studies and then ultimately were further tested in support of the NASA B-757 turbulence research flights. The new hazard characterization algorithms were utilized in a Real Time Turbulence Model (RTTM) that was operationally employed to support the NASA B-757 turbulence research flights. Improvements in the RTTM were implemented in an effort to increase the accuracy of the operational characterization of the preturbulence environment. Additionally, the initial research necessary to create a statistical evaluation scheme for the characterization indices utilized in the RTTM was undertaken. Results of all components of this research were then published in NASA contractor reports and scientific journal papers.
Kaplan, Michael L.↗
Life Test Approach for Refractory Metal/Sodium Heat Pipes
Heat pipe life tests described in the literature have seldom been conducted on a systematic basis. Typically one or more heat pipes are built and tested for an extended period at a single temperature with simple condenser loading. This paper describes an approach to generate carefully controlled data that can conclusively establish heat pipe operating life with material-fluid combinations capable of extended operation. Approximately 10 years of operational life might be compressed into 3 years of laboratory testing through a combination of increased temperature and mass fluence. Two specific test series have been identified and include: investigation of long term corrosion rates based on the guidelines contained in ASTM G-68-80 (using 7 heat pipes); and investigation of corrosion trends in a cross correlation sequence at various temperatures and mass fluences based on a central composite test design (using 9 heat pipes). The heat pipes selected for demonstration purposes are fabricated from a Mo-44.5%Re alloy with a length of 0.3 meters and a diameter of 1.59 cm(to conserve material) with a condenser to evaporator length ratio of approximately 3. The wick is a crescent annular design formed from 400-mesh Mo-Re alloy material hot isostatically pressed to produce a final wick core of 20 microns or less.
Martin, James J.↗
Crash Testing and Simulation of a Cessna 172 Aircraft: Hard Landing Onto Concrete
A full-scale crash test of a Cessna 172 aircraft was conducted at the Landing and Impact Research Facility at NASA Langley Research Center during the summer of 2015. The purpose of the test was to evaluate the performance of Emergency Locator Transmitters (ELTs) that were mounted at various locations in the aircraft and to generate impact test data for model validation. A finite element model of the aircraft was developed for execution in LSDYNA to simulate the test. Measured impact conditions were 722.4-in/s forward velocity and 276-in/s vertical velocity with a 1.5deg pitch (nose up) attitude. These conditions were intended to represent a survivable hard landing. The impact surface was concrete. During the test, the nose gear tire impacted the concrete, followed closely by impact of the main gear tires. The main landing gear spread outward, as the nose gear stroked vertically. The only fuselage contact with the impact surface was a slight impact of the rearmost portion of the lower tail. Thus, capturing the behavior of the nose and main landing gear was essential to accurately predict the response. This paper describes the model development and presents test-analysis comparisons in three categories: inertial properties, time sequence of events, and acceleration and velocity time-histories.
Jackson, Karen E.↗
The Random Transiter – EPIC 249706694/HD 139139
We have identified a star, EPIC 249706694 (HD 139139), that was observed during K2 Campaign 15 with the Kepler extended mission that appears to exhibit 28 transit-like events over the course of the 87-day observation. The unusual aspect of these dips, all but two of which have depths of 200 ± 80 ppm, is that they exhibit no periodicity, and their arrival times could just as well have been produced by a random number generator. We show that no more than four of the events can be part of a periodic sequence. We have done a number of data quality tests to ascertain that these dips are of astrophysical origin, and while we cannot be absolutely certain that this is so, they have all the hallmarks of astrophysical variability on one of two possible host stars (a likely bound pair) in the photometric aperture. We explore a number of ideas for the origin of these dips, including actual planet transits due to multiple or dust emitting planets, anomalously large TTVs, S- and P-type transits in binary systems, a collection of dust-emitting asteroids, ‘dipper-star’ activity, and short-lived starspots. All transit scenarios that we have been able to conjure up appear to fail, while the intrinsic stellar variability hypothesis would be novel and untested.
S. Rappaport↗
Simultaneous 100-kHz Acetone Planar Laser-Induced Fluorescence and OH* Chemiluminescence in a Linear Non-Premixed Detonation Channel
Reactant mixing and combustion are investigated in an optically accessible, self-excited linear detonation combustor. The mixing field is captured using 100 kHz planar laser-induced fluorescence (PLIF) imaging of acetone as a tracer in the fuel supply, while 100 kHz chemiluminescence imaging of excited-state hydroxyl (OH*) radicals simultaneously resolves the evolution of the detonation wave. Time sequences are acquired over multiple detonation cycles in each test, with acetone-PLIF images collected along multiple orthogonal planes to reveal the complex three-dimensional topography of the fuel distribution. The instantaneous and phase averaged acetone-PLIF images enable measurement of key fuel injection characteristics, such as the injector recovery time, fuel jet velocity, and refill height for a range of operating conditions. Instantaneous and phase-averaged measurements of acetone-PLIF with the time-coincident OH* chemiluminescence images also reveal a number key features, such as fuel stratification and weak detonation in the injector near field, incomplete combustion and deflagration behind the detonation wave, vitiation and deflagration of reactants ahead of the detonation wave, and fuel and oxidizer recovery time mismatch leading to combustion inefficiency. These measurements significantly enhance the ability to obtain detailed information on the intracycle and intercycle spatiotemporal evolution of the reactant refill process and its coupled effects on the detonation wave structure and propagation.
Propulsion↗
Flight Rule Design, Implementation, Verification, and Validation for the Psyche Mission
NASA Jet Propulsion Lab (JPL)’s upcoming mission Psyche will begin its journey to the asteroid (16) Psyche in late 2022 in an effort to better understand its origins and, in turn, better understand our own. Operating the spacecraft safely will require the dedicated efforts of a small team that understands the spacecraft’s operational constraints, as well as a set of powerful spacecraft models designed to catch command errors that can pose risks to mission success. One of the responsibilities of the operations team is to ensure adherence to a set of Flight Rules written by spacecraft and instrument experts that are designed to mitigate these risks. Psyche’s innovations in Flight Rule design principles and advancements in the tools and processes used to implement and check Flight Rules are discussed. A comparison of Psyche’s approach to Flight Rules to other JPL missions will provide lessons learned for future missions that must perform constraint checking during operations. Flight Rule development faces several major challenges. First, flight rule developers must work with Subject Matter Experts (SME) to write the rules in a way that captures the intent of the constraint in a straightforward, enforceable manner. Second, software implementers must correctly interpret flight rules into code so that it meets the original intent of the SME. Finally, a means must be provided for SMEs to validate flight rule implementations without requiring them to understand the underlying software. Innovative processes intended to efficiently close the loop between stakeholders and software developers are described, such as the use of test-driven development to provide stakeholders with easy-to-review implementations. New guidelines for flight rule writing, designed to address these challenges, are described for future missions to adopt and build upon. Psyche Mission System has a variety of new and heritage tools that improve in the Flight Rule validation and checking process. Psyche developed a powerful, new tool called RandSEQ and made significant improvements to Octopusjam, two valuable tools that aid the development of Flight Rule unit tests. Advancements in the models and processes for performing sequence validation with SEQuence GENerator (SEQGEN), the primary, high-heritage tool used for automated flight rule checks on Psyche, are described. The development of new software and the advancements to existing software put Psyche at the forefront of Flight Rule technology. All missions must perform detailed constraint checking, so a comparison of Psyche’s approach to some of these items to the approaches taken by other missions such as Dawn, M2020, and Europa Clipper is done, specifically to examine SME-developer communication, tools used, and development process. Lessons learned from this comparison will be provided.
Weise, Tim↗
BioNutrients-3: Precision Fermentation, Pasteurization, and Pathogen Detection - Towards Safe Fermentation and Production of Nutrients in Space
The BioNutrients (BN) project is developing a microbial manufacturing approach to supplement the NASA food system to address known nutrient degradation associated with long-term storage. BN uses synthetic biology to deliver high-value nutrients and therapeutics through genetic engineering of microbes and production of fermented food products like yogurt and kefir, in a fully dehydrated system. On-demand production of nutrients for human consumption requires rigorous safety protocols to ensure contaminants are not introduced during the fermentation process. The third iteration of the BN flight project, BN-3, further develops the BN project by investigating strategies for pathogen detection and pasteurization in microgravity. BN-3 will test the limits of pathogen detection using whole genome sequencing, standard microbial assays and the NASA Ames E-Nose, a volatile carbon nano tube-based sensor array, to detect unwanted microbes. BN-3 also expands on the number of nutrients produced in a single bioreactor to enhance efficiency of the system by combining production of B vitamins in conjunction with the carotenoids, beta-carotene and zeaxanthin. Serial production of food products through yogurt passaging, new updates to the fluorinated ethylene propylene bags to allow crew access via a straw, as well as use of a food safe pH indicator dye to indicate readiness of the food product, will further enhance the useability of this system. This presentation will provide status of the BN-3 flight project with the aim of advancing in-space biomanufacturing for on-demand microbially based food production for future space exploration.
Biomanufacturing↗