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At least 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
NASA NTRS2023

The Effects of Off-Axis Loading on the Compression After Impact Strength of Quasi-Isotropic Face Sheet Honeycomb Core Sandwich Structure

This study presents experimental results of compression after impact (CAI) testing of aluminum honeycomb core sandwich structure with face sheets made of co-cured T1100/3960 quasi-isotropic carbon/epoxy when tested at +22.5⁰ and -22.5⁰ with respect to the 0⁰ fibers. In a previous study examining the CAI strengths of honeycomb sandwich structure, it was found that specimens had different CAI strengths, based on a [-45/90/+45/0]s layup, depending on whether they were tested in the 0⁰ direction (face sheet layup of [-45/90/+45/0]s) or 90⁰ direction (face sheet layup of [+45/0/-45/90]s). The CAI strength results showed that the specimens tested in the 90⁰ direction had a 19% drop in CAI strength compared to specimens tested in the 0⁰ direction. This was attributed to the 0⁰ load bearing plies in the 0⁰ direction specimens being “tucked in” at the center of the specimen thus providing more stability against microbuckling. This raised the question as to what CAI strength would specimens tested at +22.5⁰ (face sheet layup of [-22.5/- 67.5/+67.6/+22.5]s) and -22.5⁰ (face sheet layup of [-67.5/+67.5/+22.5/-22.5]s) have compared to specimens tested in the 0⁰ and 90⁰ direction. Results presented in this study show that the specimens loaded at +22.5⁰ and -22.5⁰ have a similar average CAI strength compared to the specimens loaded in the 0⁰ direction. The specimens loaded in the 90⁰ direction exhibit 16% lower average CAI strength. Additional specimens were tested in the +45⁰ direction to put the 0⁰ load bearing fibers on the outside of the specimen to see if this would decrease the strength as has been documented for undamaged strength. These specimens have average CAI strength values between the 0⁰ direction average CAI strength values and the 90⁰ direction average CAI strength values.

Sandwich structure↗
NASA NTRS1973

Simulator evaluation of display concepts for pilot monitoring and control of space shuttle approach and landing. Phase 2: Manual flight control

A study of the display requirements for final approach management of the space shuttle orbiter vehicle is presented. An experimental display concept, providing a more direct, pictorial representation of the vehicle's movement relative to the selected approach path and aiming points, was developed and assessed as an aid to manual flight path control. Both head-up, windshield projections and head-down, panel mounted presentations of the experimental display were evaluated in a series of simulated orbiter approach sequence. Data obtained indicate that the experimental display would enable orbiter pilots to exercise greater flexibility in implementing alternative final approach control strategies. Touchdown position and airspeed dispersion criteria were satisfied on 91 percent of the approach sequences, representing various profile and wind effect conditions. Flight path control and airspeed management satisfied operationally-relevant criteria for the two-segment, power-off orbiter approach and were consistently more accurate and less variable when the full set of experimental display elements was available to the pilot. Approach control tended to be more precise when the head-up display was used; however, the data also indicate that the head-down display would provide adequate support for the manual control task.

Gartner, W. B.↗
NASA NTRS1990

A real time neural net estimator of fatigue life

A neural net architecture is proposed to estimate, in real-time, the fatigue life of mechanical components, as part of the Intelligent Control System for Reusable Rocket Engines. Arbitrary component loading values were used as input to train a two hidden-layer feedforward neural net to estimate component fatigue damage. The ability of the net to learn, based on a local strain approach, the mapping between load sequence and fatigue damage has been demonstrated for a uniaxial specimen. Because of its demonstrated performance, the neural computation may be extended to complex cases where the loads are biaxial or triaxial, and the geometry of the component is complex (e.g., turbopump blades). The generality of the approach is such that load/damage mappings can be directly extracted from experimental data without requiring any knowledge of the stress/strain profile of the component. In addition, the parallel network architecture allows real-time life calculations even for high frequency vibrations. Owing to its distributed nature, the neural implementation will be robust and reliable, enabling its use in hostile environments such as rocket engines. This neural net estimator of fatigue life is seen as the enabling technology to achieve component life prognosis, and therefore would be an important part of life extending control for reusable rocket engines.

Troudet, T.↗
NASA NTRS1990

A real time neural net estimator of fatigue life

A neural network architecture is proposed to estimate, in real-time, the fatigue life of mechanical components, as part of the intelligent Control System for Reusable Rocket Engines. Arbitrary component loading values were used as input to train a two hidden-layer feedforward neural net to estimate component fatigue damage. The ability of the net to learn, based on a local strain approach, the mapping between load sequence and fatigue damage has been demonstrated for a uniaxial specimen. Because of its demonstrated performance, the neural computation may be extended to complex cases where the loads are biaxial or triaxial, and the geometry of the component is complex (e.g., turbopumps blades). The generality of the approach is such that load/damage mappings can be directly extracted from experimental data without requiring any knowledge of the stress/strain profile of the component. In addition, the parallel network architecture allows real-time life calculations even for high-frequency vibrations. Owing to its distributed nature, the neural implementation will be robust and reliable, enabling its use in hostile environments such as rocket engines.

Troudet, T.↗
NASA NTRS1992

Design of structure/control systems with transient response constraints exhibiting relative minima

Structural optimization problems involving dynamic behavior constraints often exhibit nonconvex design spaces. The direct application of a global optimization algorithm requires a large number of function evaluations which in term require a large number of dynamic structural analyses. This work presents a strategy aimed at finding the global optimum for problems with transient dynamic behavior constraints based on approximation concepts. The method consists of generating and solving a sequence of approximate problems using a global optimizer. The approximations are explicit and capture the inherent nonconvexity of the exact functions. A simple example problem is presented.

Sepulveda, A. E.↗
NASA NTRS2012

Ultra-Compact Motor Controller

This invention is an electronically commutated brushless motor controller that incorporates Hall-array sensing in a small, 42-gram package that provides 4096 absolute counts per motor revolution position sensing. The unit is the size of a miniature hockey puck, and is a 44-pin male connector that provides many I/O channels, including CANbus, RS-232 communications, general-purpose analog and digital I/O (GPIO), analog and digital Hall inputs, DC power input (18-90 VDC, 0-l0 A), three-phase motor outputs, and a strain gauge amplifier. This controller replaces air cooling with conduction cooling via a high-thermal-conductivity epoxy casting. A secondary advantage of the relatively good heat conductivity that comes with ultra-small size is that temperature differences within the controller become smaller, so that it is easier to measure the hottest temperature in the controller with fewer temperature sensors, or even one temperature sensor. Another size-sensitive design feature is in the approach to electrical noise immunity. At a very small size, where conduction paths are much shorter than in conventional designs, the ground becomes essentially isopotential, and so certain (space-consuming) electrical noise control components become unnecessary, which helps make small size possible. One winding-current sensor, applied to all of the windings in fast sequence, is smaller and wastes less power than the two or more sensors conventionally used to sense and control winding currents. An unexpected benefit of using only one current sensor is that it actually improves the precision of current control by using the "same" sensors to read each of the three phases. Folding the encoder directly into the controller electronics eliminates a great deal of redundant electronics, packaging, connectors, and hook-up wiring. The reduction of wires and connectors subtracts substantial bulk and eliminates their role in behaving as EMI (electro-magnetic interference) antennas. A shared knowledge by each motor controller of the state of all the motors in the system at 500 Hz also allows parallel processing of higher-level kinematic matrix calculations.

Townsend, William T.↗
NASA NTRSDate not supplied

Beyond BioSentinel: Iterative Development of Automated Microfluidics

NASA Ames has flown a series of Bio-CubeSats that performed biology experiments supported by automated fluidic systems. Since Genesat-1 in 2006, these payloads have increased in complexity and functionality, building upon previous successes, and applying lessons learned. BioSentinel was the most recent of this series, launched into heliocentric orbit onboard Artemis-1 in 2022. This presentation will discuss how the fluidic technology developed for these Bio-CubeSat missions, including the multi-layer polycarbonate manifolds at the heart of the BioSentinel BioSensor, have spurred the development of several additional projects. Most directly is the modified BioSensor that will be a part of LEIA, which will perform its Lunar biology experiment onboard a Commercial Lunar Payload Services lander. Several search-for-life manifolds have been designed to prepare samples from icy moons for downstream analyses. Two early career Polaris projects are developing fluidics to perform genetic sequencing on samples from multigenerational cell culture and to extract and quantify target miRNAs to support astronaut radiation health assessment. Improving the readiness of these systems has been accelerated by adopting the established flight heritage and microgravity-compatibility of the Bio-CubeSat fluidic hardware and designs, while focusing development efforts on the integration of novel functionalities and components.

microfluidics↗
NASA NTRS2002

Phylogeny and systematic position of Opiliones: a combined analysis of chelicerate relationships using morphological and molecular data

The ordinal level phylogeny of the Arachnida and the suprafamilial level phylogeny of the Opiliones were studied on the basis of a combined analysis of 253 morphological characters, the complete sequence of the 18S rRNA gene, and the D3 region of the 28S rRNA gene. Molecular data were collected for 63 terminal taxa. Morphological data were collected for 35 exemplar taxa of Opiliones, but groundplans were applied to some of the remaining chelicerate groups. Six extinct terminals, including Paleozoic scorpions, are scored for morphological characters. The data were analyzed using strict parsimony for the morphological data matrix and via direct optimization for the molecular and combined data matrices. A sensitivity analysis of 15 parameter sets was undertaken, and character congruence was used as the optimality criterion to choose among competing hypotheses. The results obtained are unstable for the high-level chelicerate relationships (except for Tetrapulmonata, Pedipalpi, and Camarostomata), and the sister group of the Opiliones is not clearly established, although the monophyly of Dromopoda is supported under many parameter sets. However, the internal phylogeny of the Opiliones is robust to parameter choice and allows the discarding of previous hypotheses of opilionid phylogeny such as the "Cyphopalpatores" or "Palpatores." The topology obtained is congruent with the previous hypothesis of "Palpatores" paraphyly as follows: (Cyphophthalmi (Eupnoi (Dyspnoi + Laniatores))). Resolution within the Eupnoi, Dyspnoi, and Laniatores (the latter two united as Dyspnolaniatores nov.) is also stable to the superfamily level, permitting a new classification system for the Opiliones. c2002 The Willi Hennig Society.

NASA Discipline Evolutionary Biology↗
NASA NTRS2023

Magma Ocean, Water, and the Early Atmosphere of Venus

The current state and surface conditions of the Earth and its twin planet Venus are drastically different. Whether these differences are directly inherited from the earliest stages of planetary evolution, when the interior was molten, or arose later during the long-term evolution is still unclear. Yet, it is clear that water, its abundance, state, and distribution between the different planetary reservoirs, which are intimately related to the solidification and outgassing of the early magma ocean, are key components regarding past and present-day habitability, planetary evolution, and the different pathways leading to various surface conditions. In this chapter we start by reviewing the outcomes of the accretion sequence, with particular emphasis on the sources and timing of water delivery in light of available constraints, and the initial thermal state of Venus at the end of the main accretion. Then, we detail the processes at play during the early thermo-chemical evolution of molten terrestrial planets, and how they can affect the abundance and distribution of water within the different planetary reservoirs. Namely, we focus on the magma ocean cooling, solidification, and concurrent formation of the outgassed atmosphere. Accounting for the possible range of parameters for early Venus and based on the mechanisms and feedbacks described, we provide an overview of the likely evolutionary pathways leading to diverse surface conditions, from a temperate to a hellish early Venus. The implications of the resulting surface conditions and habitability are discussed in the context of the subsequent long-term interior and atmospheric evolution. Future research directions and observations are proposed to constrain the different scenarios in order to reconcile Venus’ early evolution with its current state, while deciphering which path it followed.

Venus↗
NASA NTRS1986

Techniques for computing the discrete Fourier transform using the quadratic residue Fermat number systems

The complex integer multiplier and adder over the direct sum of two copies of finite field developed by Cozzens and Finkelstein (1985) is specialized to the direct sum of the rings of integers modulo Fermat numbers. Such multiplication over the rings of integers modulo Fermat numbers can be performed by means of two integer multiplications, whereas the complex integer multiplication requires three integer multiplications. Such multiplications and additions can be used in the implementation of a discrete Fourier transform (DFT) of a sequence of complex numbers. The advantage of the present approach is that the number of multiplications needed to compute a systolic array of the DFT can be reduced substantially. The architectural designs using this approach are regular, simple, expandable and, therefore, naturally suitable for VLSI implementation.

Truong, T. K.↗
NASA NTRS1991

Ultraluminous infrared galaxies

One of the major discoveries of the the IRAS all-sky survey was a population of sources having the bolometric luminosities of quasars, but where more than 90 percent of the luminosity emerges in the infrared. These objects, more numerous than quasars, are found exclusivly in interacting/merging galaxies that are extremely rich in interstellar gas. We have accumulated evidence that suggests that these systems are indeed quasars, obscured by many tens of magnitudes of extinction. We suggest that these Ultraluminous Infrared Galaxies are the formation stage of quasars, and that colliding galaxies, ultraluminous infrared galaxies, and quasars might be linked through an evolutionary sequence where the infrared bright phase is one in which the quasar is formed in the nucleus of a merger system, and is enshrouded in gas and dust, while the UV excess quasars are at the end state of quasar evolution where most of the enveloping dust cloud has been dissipated, and the quasar is visible directly.

Soifer, B. T.↗
NASA NTRS1999

Data Structure and Parallel Decomposition Considerations on a Fibonacci Grid

The Fibonacci grid, proposed by Swinbank and Purser (see companion abstract), provides attractive properties for global numerical atmospheric prediction by offering an optimally homogeneous, geometrically regular, and approximately isotropic discretization, with only the polar regions requiring special numerical treatment. It is a mathematical idealization, applied to the sphere, of the multi-spiral patterns often found in botanical structures, such as in pine cones and sunflower heads. Computationally, it is natural to organize the domain, into zones, in each of which the same pair, or triple, of "Fibonacci spirals" dominate. But the further subdivision of such zones into "tiles" of a shape and size suitable for distribution to the processors of a massively parallel computer requires very careful consideration if the subsequent spatial computations along the respective spirals, especially those computations (such as compact differencing schemes) that involve recursion, can be implemented in an efficient "load-balanced "manner without requiring excessive amounts of inter-processor communications. In this paper we show how certain "number theoretic" properties of the Fibonacci sequence (whose numbers prescribe the multiplicity of successive spirals) may be exploited in the decomposition of grid zones into tidy arrangements of triangular grid tiles, each tile possessing one side approximately parallel to the constant-latitude zone boundary. We also describe how the spatially recursive processes may be decomposed across such a tiling, and the directionality of the recursions reversed on alternate grid lines, to ensure a very high degree of load balancing throughout the execution of the computations required for one time step of a global model.

Michalakes, John↗
NASA NTRS2018

Interplanetary Trajectory Design for NASA's Common Probe Study

The Galileo Probe, Pioneer-Venus probes, and SPRITE concept all share a number of common characteristics. They all follow a similar entry and descent sequence, using an aeroshell to protect against entry environments, and parachutes to aid in extrusion and descent speed control of the descent vehicle containing the science instruments. The descent vehicles all contained similar instruments (e.g. mass spectrometers and atmosphere structure sensors), and data was either relayed back to a carrier spacecraft (Galileo Probe, SPRITE) or transmitted direct to Earth (Pioneer-Venus). Based on these similar characteristics, NASA initiated a study to investigate a “common probe' that might be designed to perform similar science in a variety of planetary environments. This concept would leverage a common aeroshell design, and descent vehicle designs that could be made as similar as possible (the primary exception being that Venus will require a pressure vessel due to the extreme pressures and temperatures seen in the lower portion of the descent). To support the Common Probe study, GSFC and JPL performed a series of interplanetary trajectory analyses to help develop the mission designs for Venus, Jupiter, Saturn, Uranus, and Neptune. Primary considerations in the trajectory modeling included: a maximum of 12-year time of flight (for outer planet destinations), generation of both steep and shallow entry trajectories to each destination (where steep and shallow resulted in approximately 150 g and 50 g peak deceleration during entry at each location), and consideration of the data relay. Gravity assists and trajectories with low delta-V requirements (typically much less than 500 m/s) were also incorporated into the design process to enable launch on existing vehicles such as the Atlas V.

Hughes, Kyle M.↗
NASA NTRSDate not supplied

Spaceflight Autonomous Multigenerational Microbial Sequencer in Support of Plant-Growth Systems

The CubeSat platform has proven successful in obtaining meaningful life science information when biological payloads are incorporated. Examples include: 1) the first-ever CubeSat with a biological payload, GeneSat-1, which demonstrated decreased growth rates for flight samples of Escherichia coli in low Earth orbit (Parra et al. 2008); 2) PharmaSat, demonstrated that Saccharomyces cerevisiae in the microgravity environment exhibits a significant level of metabolic activity even at high doses of applied antifungal (Ricco et al. 2011); 3) O/OREOS, which used Bacillus subtilis(bacteria) to demonstrate for the first time that microorganisms can be loaded in a dried, dormant form and then rehydrated and grown in orbit months after launch (Nicholson et al. 2011; Ehrenfreund et al. 2014; 4) the SporeSat payload, which investigated Ceratopteris richardii(fern spores) using lab-on-a-chip devices (BioCDs) and minicentrifuges to produce artificial gravitational forces in ground studies (Park et al. 2017), with demonstration of the BioCD and minicentrifuge in space; 5) EcAMSat, the first CubeSat to be directly deployed from the ISS for an experiment assessing antibiotic resistance of E. coli in the microgravity environment (Padgen et al. 2020); 6) BioSentinel, exposed a culture of yeast to galactic cosmic radiation (GCR) and solar particle events while in heliocentric orbit to measure the rate of double-strand-break repair using DNA-repair-deficient mutants. This effort measures the metabolic parameters of yeast in a deep-space environment compared to Earth ambient conditions using a 3-color LED detection system (Ricco et al. 2020; Padgen et al. 2021). We aim to expand this list to include a Spaceflight Autonomous Multigenerational Microbial Sequencer (SAMMS). SAMMS will allow for the genome level understanding of changes in growth and metabolic activity for any organism. While microbes are suitable for early studies in our proposed platform because of their small size, small and relatively less-complicated genomes, fast generation times, and relevance to life support systems; multicellular organisms can similarly be evaluated for their genetic response to the spaceflight environment. The Spaceflight Autonomous Multigenerational Microbial Sequencer (SAMMS) will enable autonomous sequencing of biological samples in plant production units, cislunar orbit and on the lunar surface to examine spaceflight effects (ie. radiation, altered gravity, reduced pressures) on plant and microbial genomes.On this team a Kennedy Space Center (KSC) space crop production and water systems microbiologist/molecular biologist works with a Johnson Space Center (JSC) International Space Station (ISS) microbial sequencing expert and an Ames Research Center (ARC) CubeSat Engineering team to convert an automated Oxford Nanopore librarypreparation and sequencing method to a fluidic CubeSat payload system. The Oxford Nanopore MinION sequencing platform has proven successful in the spaceflight environment onboard the ISS (Stahl-Rommel et al. 2021). Further long-duration spaceflight and exposure to high levels of radiation will cause genotypic effects in biological organisms that may affect their function. Monitoring the adaption of a population to the spaceflight environment and any subsequent beneficial mutations will allow for the harnessing of organisms best suited for use in life support systems. This will ensure that the selected life support-essential microorganisms maintain their intended specified function over generations of culturing in the relevant spaceflight environment without becoming hazardous to crew or spacecraft systems.

Aubrie E Orourke↗
NASA NTRS1997

Information transfer from peptide nucleic acids to RNA by template-directed syntheses

Peptide nucleic acids (PNAs) are uncharged analogs of DNA and RNA in which the ribose-phosphate backbone is substituted by a backbone held together by amide bonds. PNAs are interesting as models of alternative genetic systems because they form potentially informational base paired helical structures. A PNA C10 oligomer has been shown to act as template for efficient formation of oligoguanylates from activated guanosine ribonucleotides. In a previous paper we used heterosequences of DNA as templates in sequence-dependent polymerization of PNA dimers. In this paper we show that information can be transferred from PNA to RNA. We describe the reactions of activated mononucleotides on heterosequences of PNA. Adenylic, cytidylic and guanylic acids were incorporated into the products opposite their complement on PNA, although less efficiently than on DNA templates.

NASA Discipline Exobiology↗
NASA NTRS1972

Some new techniques for processing remotely obtained images by self-generated spectral masks.

An extension of a new technique that makes possible parallel, simultaneous processing of remotely obtained images is presented. The technique holds out promise for automatic onboard classification of data. The central feature involves the generation of binary masks, directly from the image, based on object reflectance data, that group objects into equivalence classes. These masks, called equivalence class masks, can be used in various logical combinations to isolate classes of objects with a priori known reflectance or radiance signatures. Experimental verification of the technique is furnished for simple scenes. A computational scheme, based on a sequence of integrated irradiance measurements on the image, that makes it possible to identify objects within an equivalence class is suggested.

Stark, H.↗
NASA NTRS1991

Image-based ranging and guidance for rotorcraft

This report documents the research carried out under NASA Cooperative Agreement No. NCC2-575 during the period Oct. 1988 - Dec. 1991. Primary emphasis of this effort was on the development of vision based navigation methods for rotorcraft nap-of-the-earth flight regime. A family of field-based ranging algorithms were developed during this research period. These ranging schemes are capable of handling both stereo and motion image sequences, and permits both translational and rotational camera motion. The algorithms require minimal computational effort and appear to be implementable in real time. A series of papers were presented on these ranging schemes, some of which are included in this report. A small part of the research effort was expended on synthesizing a rotorcraft guidance law that directly uses the vision-based ranging data. This work is discussed in the last section.

Menon, P. K. A.↗
NASA NTRS1995

LDEF Interplanetary Dust Experiment (IDE) results

The Interplanetary Dust Experiment (IDE) provided high time resolution detection of microparticle impacts on the Long Duration Exposure Facility satellite. Particles, in the diameter range from 0.2 microns to several hundred microns, were detected impacting on six orthogonal surfaces of the gravity-gradient stabilized LDEF spacecraft. The total sensitive surface area was about one square meter, distributed between LDEF rows 3 (Wake or West), 6 (South), 9 (Ram or East), 12 (North), as well as the Space and Earth ends of LDEF. The time of each impact is known to an accuracy that corresponds to better than one degree in orbital longitude. Because LDEF was gravity-gradient stabilized and magnetically damped, the direction of the normal to each detector panel is precisely known for each impact. The 11 1/2 month tape-recorded data set represents the most extensive record gathered of the number, orbital location, and incidence direction for microparticle impacts in low Earth orbit. Perhaps the most striking result from IDE was the discovery that microparticle impacts, especially on the Ram, South, and North surfaces, were highly episodic. Most such impacts occurred in localized regions of the orbit for dozens or even hundreds of orbits in what we have termed Multiple Orbit Event Sequences (MOES). In addition, more than a dozen intense and short-lived 'spikes' were seen in which impact fluxes exceeded the background by several orders of magnitude. These events were distributed in a highly non-uniform fashion in time and terrestrial longitude and latitude.

Oliver, John P.↗