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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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At least 145 records · Page 8

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NASA NTRSDate not supplied

Power System Human Machine Interfaces for the X-57 Mod II Aircraft

The transition from a Tecnam (Costruzioni Aeronautiche Tecnam srl) (Sapua, Italy) P2006T twin-engine aircraft into the fully electric X-57 Modification II (Mod II) configuration required the development of cockpit displays and controls to allow the pilot to properly monitor and interface with the research electric system. This paper describes the machine interfaces developed to interface with the X-57 Mod II traction battery system and the unique considerations of developing interfaces and monitoring tools for electric aircraft. The key design philosophy during the X-57 cockpit development was to retain or make minor modifications to the stock P2006T aircraft wherever possible and to use highly reliable commercial displays for monitoring of safety critical parameters. From these efforts, development of accurate estimates of battery state of charge and energy meters designed specifically for flight applications for future electric aircraft development is recommended.

James Reynolds↗

NASA NTRS1991

951 Gaspra - A pre-Galileo estimate of its surface evolution

An effort is made to quantitatively model the collisional environment and surface evolution of asteroid 951 Gaspra prior to the flyby of the Galileo spacecraft later this year. Gaspra's average intrinsic collisional probability is calculated to be 5.4 x 10 to the -18th/sq km per year with a root mean square impact velocity of 5.0 km/sec. The projectile population and impact strength for Gaspra are highly uncertain and a range of values is considered. Based on these models, Gaspra is unlikely to be a primordial object surviving from the beginning of the solar system. It is most likely a second or multiple generation fragment forming about 100 million yr ago. For a low impact flux, the crater size distribution directly reveals the size distribution of the impacting population. For a nonequilibrium surface, model-dependent isochrons for estimating the age of the surface are given. Lower limits are set by the model for Gaspra's age (about 1 billion yr) and flux for the case of a high impact flux producing an equilibrium surface.

Namiki, Noriyuki↗

NASA NTRS1983

Early estimation of resource expenditures and program size

A substantial amount of software engineering research effort was focused on the development of software estimation models. A measure of lines of code was derived based on the origin of the delivered code, L sub dev = N + E + 0.2 (S + O) (where L sub dev = developed lines of code, N = newly implemented lines of code, E = extensively modified lines of code, S = slightly modified lines of code, and O = old unchanged lines of code) that is substituted in the following equation H sub s = aL sup b (where H sub s = staff-hours of effort, L = lines of code, a = a constant, and b = a constant). The limitations of this model are discussed and some alternative estimation models that can be used earlier in the development process are proposed.

Card, D.↗

NASA NTRS1995

Advances in hypersonic vehicle synthesis with application to studies of advanced thermal protection system

This report summarizes the work entitled 'Advances in Hypersonic Vehicle Synthesis with Application to Studies of Advanced Thermal Protection Systems.' The effort was in two areas: (1) development of advanced methods of trajectory and propulsion system optimization; and (2) development of advanced methods of structural weight estimation. The majority of the effort was spent in the trajectory area.

Ardema, Mark D.↗

NASA NTRS1986

A study of fault prediction and reliability assessment in the SEL environment

An empirical study on estimation and prediction of faults, prediction of fault detection and correction effort, and reliability assessment in the Software Engineering Laboratory environment (SEL) is presented. Fault estimation using empirical relationships and fault prediction using curve fitting method are investigated. Relationships between debugging efforts (fault detection and correction effort) in different test phases are provided, in order to make an early estimate of future debugging effort. This study concludes with the fault analysis, application of a reliability model, and analysis of a normalized metric for reliability assessment and reliability monitoring during development of software.

Basili, Victor R.↗

NASA NTRS1989

Space shuttle propulsion estimation development verification, volume 1

The results of the Propulsion Estimation Development Verification are summarized. A computer program developed under a previous contract (NAS8-35324) was modified to include improved models for the Solid Rocket Booster (SRB) internal ballistics, the Space Shuttle Main Engine (SSME) power coefficient model, the vehicle dynamics using quaternions, and an improved Kalman filter algorithm based on the U-D factorized algorithm. As additional output, the estimated propulsion performances, for each device are computed with the associated 1-sigma bounds. The outputs of the estimation program are provided in graphical plots. An additional effort was expended to examine the use of the estimation approach to evaluate single engine test data. In addition to the propulsion estimation program PFILTER, a program was developed to produce a best estimate of trajectory (BET). The program LFILTER, also uses the U-D factorized algorithm form of the Kalman filter as in the propulsion estimation program PFILTER. The necessary definitions and equations explaining the Kalman filtering approach for the PFILTER program, the models used for this application for dynamics and measurements, program description, and program operation are presented.

Rogers, Robert M.↗

NASA NTRS2004

Physical Validation of TRMM TMI and PR Monthly Rain Products Over Oklahoma

The Tropical Rainfall Measuring Mission (TRMM) provides monthly rainfall estimates using data collected by the TRMM satellite. These estimates cover a substantial fraction of the earth's surface. The physical validation of TRMM estimates involves corroborating the accuracy of spaceborne estimates of areal rainfall by inferring errors and biases from ground-based rain estimates. The TRMM error budget consists of two major sources of error: retrieval and sampling. Sampling errors are intrinsic to the process of estimating monthly rainfall and occur because the satellite extrapolates monthly rainfall from a small subset of measurements collected only during satellite overpasses. Retrieval errors, on the other hand, are related to the process of collecting measurements while the satellite is overhead. One of the big challenges confronting the TRMM validation effort is how to best estimate these two main components of the TRMM error budget, which are not easily decoupled. This four-year study computed bulk sampling and retrieval errors for the TRMM microwave imager (TMI) and the precipitation radar (PR) by applying a technique that sub-samples gauge data at TRMM overpass times. Gridded monthly rain estimates are then computed from the monthly bulk statistics of the collected samples, providing a sensor-dependent gauge rain estimate that is assumed to include a TRMM equivalent sampling error. The sub-sampled gauge rain estimates are then used in conjunction with the monthly satellite and gauge (without sub- sampling) estimates to decouple retrieval and sampling errors. The computed mean sampling errors for the TMI and PR were 5.9% and 7.796, respectively, in good agreement with theoretical predictions. The PR year-to-year retrieval biases exceeded corresponding TMI biases, but it was found that these differences were partially due to negative TMI biases during cold months and positive TMI biases during warm months.

Fisher, Brad L.↗

NASA NTRS2019

Blind Validation Study of Parametric Cost Estimation Tool SEER-H for NASA Space Missions

One of the primary parametric cost modeling tools used by NASA and the aerospace industry to estimate the development and production cost of future spacecraft hardware is SEER-H by Galorath. To date, no independent validation of this tool for cost estimation of space missions has been reported in the literature. In the present validation study, cost estimators used SEER-H to estimate the cost of twelve different past NASA science missions. The estimators were prevented from knowing the actual cost of the missions in an effort to minimize cognitive biases. The point estimates of SEER-H had an average error of 23%, median error of -0.3%, and a standard deviation of 43%. Nine of the twelve mission's actual costs fell within the 80% confidence interval of SEER's probabilistic estimates. Several factors independent of SEER that may have affected the accuracy of the results have been identified and are discussed; these include: uncertainty in the technical data used for the estimates, the methods used to estimate uncertainty in spacecraft component mass and numbers of prototypes, and the experience of the estimators.

SEER-H↗

NASA NTRS2019

Improving Brightness Temperature Measurements near Coastal Areas for SMAP

The Soil Moisture Active Passive (SMAP) mission is designed to acquire L-band radiometer measurements for the estimation of soil moisture with 0.04 m3/m3 volumetric accuracy in the top 5 cm for vegetation with water content of less than 5 kg/m2. In regions near the coast or near inland bodies of water, the signal measured by the SMAP radiometer contains emissions from land and water, resulting in errors in the soil moisture estimation. In this paper, the effort to extract the brightness temperature (TB) according to the land fraction or water fraction (depending on the center of the footprint location) from the affected SMAP measurements was addressed. A single pixel correction algorithm was applied and its performance was evaluated over simulated data. A data-driven approach for the estimation of land and water TB for data correction was developed. The correction algorithm was then applied to real data and its performance was assessed over the SMAP soil moisture retrievals. We showed that the single pixel algorithm is an effective and computationally efficient algorithm for removing land or water TB contamination from the SMAP data.

Julian Chaubell↗

NASA NTRS2006

Studies in Software Cost Model Behavior: Do We Really Understand Cost Model Performance?

While there exists extensive literature on software cost estimation techniques, industry practice continues to rely upon standard regression-based algorithms. These software effort models are typically calibrated or tuned to local conditions using local data. This paper cautions that current approaches to model calibration often produce sub-optimal models because of the large variance problem inherent in cost data and by including far more effort multipliers than the data supports. Building optimal models requires that a wider range of models be considered while correctly calibrating these models requires rejection rules that prune variables and records and use multiple criteria for evaluating model performance. The main contribution of this paper is to document a standard method that integrates formal model identification, estimation, and validation. It also documents what we call the large variance problem that is a leading cause of cost model brittleness or instability.

data mining↗

NASA NTRS1994

Associated with aerospace vehicles development of methodologies for the estimation of thermal properties

Thermal stress analyses are an important aspect in the development of aerospace vehicles at NASA-LaRC. These analyses require knowledge of the temperature distributions within the vehicle structures which consequently necessitates the need for accurate thermal property data. The overall goal of this ongoing research effort is to develop methodologies for the estimation of the thermal property data needed to describe the temperature responses of these complex structures. The research strategy undertaken utilizes a building block approach. The idea here is to first focus on the development of property estimation methodologies for relatively simple conditions, such as isotropic materials at constant temperatures, and then systematically modify the technique for the analysis of more and more complex systems, such as anisotropic multi-component systems. The estimation methodology utilized is a statistically based method which incorporates experimental data and a mathematical model of the system. Several aspects of this overall research effort were investigated during the time of the ASEE summer program. One important aspect involved the calibration of the estimation procedure for the estimation of the thermal properties through the thickness of a standard material. Transient experiments were conducted using a Pyrex standard at various temperatures, and then the thermal properties (thermal conductivity and volumetric heat capacity) were estimated at each temperature. Confidence regions for the estimated values were also determined. These results were then compared to documented values. Another set of experimental tests were conducted on carbon composite samples at different temperatures. Again, the thermal properties were estimated for each temperature, and the results were compared with values obtained using another technique. In both sets of experiments, a 10-15 percent off-set between the estimated values and the previously determined values was found. Another effort was related to the development of the experimental techniques. Initial experiments required a resistance heater placed between two samples. The design was modified such that the heater was placed on the surface of only one sample, as would be necessary in the analysis of built up structures. Experiments using the modified technique were conducted on the composite sample used previously at different temperatures. The results were within 5 percent of those found using two samples. Finally, an initial heat transfer analysis, including conduction, convection and radiation components, was completed on a titanium sandwich structural sample. Experiments utilizing this sample are currently being designed and will be used to first estimate the material's effective thermal conductivity and later to determine the properties associated with each individual heat transfer component.

Scott, Elaine P.↗

NASA NTRS2015

ExMC Work Prioritization Process

Last year, NASA's Human Research Program (HRP) introduced the concept of a "Path to Risk Reduction" (PRR), which will provide a roadmap that shows how the work being done within each HRP element can be mapped to reducing or closing exploration risks. Efforts are currently underway within the Exploration Medical Capability (ExMC) Element to develop a structured, repeatable process for prioritizing work utilizing decision analysis techniques and risk estimation tools. The goal of this effort is to ensure that the work done within the element maximizes risk reduction for future exploration missions in a quantifiable way and better aligns with the intent and content of the Path to Risk Reduction. The Integrated Medical Model (IMM) will be used to identify those conditions that are major contributors of medical risk for a given design reference mission. For each of these conditions, potential prevention, screening, diagnosis, and treatment methods will be identified. ExMC will then aim to prioritize its potential investments in these mitigation methods based upon their potential for risk reduction and other factors such as vehicle performance impacts, near term schedule needs, duplication with external efforts, and cost. This presentation will describe the process developed to perform this prioritization and inform investment discussions in future element planning efforts. It will also provide an overview of the required input information, types of process participants, figures of merit, and the expected outputs of the process.

Simon, Matthew↗

NASA NTRS1974

Projection of school district enrollments

The objectives were to provide a better statistical basis for enrollment projections, to attempt to model the school district's enrollment, and to produce a single estimate of enrollment for each grade, grade group, and ethnic group, and for the total by year. Efforts were also made to provide error estimates for the projections, to design a simple, user-oriented computer program for use by school district administrators, and to work with real data from local school districts and aid them in making projections on an experimental basis. The study at Jet Propulsion Laboratory was concerned with projection methodology and production of a generally usable computer program.

Van Dillen, S. L.↗

NASA NTRS1994

The development and application of composite complexity models and a relative complexity metric in a software maintenance environment

A great deal of effort is now being devoted to the study, analysis, prediction, and minimization of software maintenance expected cost, long before software is delivered to users or customers. It has been estimated that, on the average, the effort spent on software maintenance is as costly as the effort spent on all other software costs. Software design methods should be the starting point to aid in alleviating the problems of software maintenance complexity and high costs. Two aspects of maintenance deserve attention: (1) protocols for locating and rectifying defects, and for ensuring that noe new defects are introduced in the development phase of the software process; and (2) protocols for modification, enhancement, and upgrading. This article focuses primarily on the second aspect, the development of protocols to help increase the quality and reduce the costs associated with modifications, enhancements, and upgrades of existing software. This study developed parsimonious models and a relative complexity metric for complexity measurement of software that were used to rank the modules in the system relative to one another. Some success was achieved in using the models and the relative metric to identify maintenance-prone modules.

Hops, J. M.↗

NASA NTRS1974

Feasibility study of common electronic equipment for shuttle sortie experiment payloads

A study was conducted to determine the feasibility of using standardized electronic equipment on the space shuttle vehicle in an effort to reduce the cost estimates. The standards for Nuclear Instrument Modules (NIM) and CAMAC electronic equipment are presented and described. It was determined that the CAMAC electronic equipment was more suitable for use with the space shuttle systems. Specific applications of the CAMAC equipment are analyzed. Illustrations of the equipment and circuit diagrams of the subsystems are provided.

Source record↗

NASA NTRS1987

Deconvolution of sea state parameters from altimeter waveforms

The paper reports on an on-going effort at the JPL to estimate the accuracy of ocean state parameters which have been obtained from the specular point probability density function (pdf) of the ocean surface. This pdf is obtained by the deconvolution of the return waveform of oceanographic altimeters such as Seasat, Geosat, or Topex.

Rodriguez, Ernesto↗

NASA NTRS1989

High-Altitude Turbulence For Supersonic Airplanes

Report reviews accumulated knowledge of atmospheric turbulence at high altitudes. Discusses characteristics of high-altitude turbulence and associated meteorological features, with emphasis on data obtained by flight research conducted in XB-70 and YF-12A prototype aircraft. Gives example of numerical simulation of gravity waves to illustrate potential contribution of such studies to understanding of atmospheric turbulence. Products of such efforts include ability to extend estimates of transient properties of atmospheric altitudes below 20 km to altitudes as high as 80 km for use in design and flight simulation of future advanced aerospace vehicles. Enables more accurate assessment of feasibility of remote sensors and computer systems aboard airplanes to process measurements into advanced warnings of turbulence.

Ehernberger, L. J.↗

NASA NTRS1990

A study of mass data storage technology for rocket engine data

The results of a nine month study program on mass data storage technology for rocket engine (especially the Space Shuttle Main Engine) health monitoring and control are summarized. The program had the objective of recommending a candidate mass data storage technology development for rocket engine health monitoring and control and of formulating a project plan and specification for that technology development. The work was divided into three major technical tasks: (1) development of requirements; (2) survey of mass data storage technologies; and (3) definition of a project plan and specification for technology development. The first of these tasks reviewed current data storage technology and developed a prioritized set of requirements for the health monitoring and control applications. The second task included a survey of state-of-the-art and newly developing technologies and a matrix-based ranking of the technologies. It culminated in a recommendation of optical disk technology as the best candidate for technology development. The final task defined a proof-of-concept demonstration, including tasks required to develop, test, analyze, and demonstrate the technology advancement, plus an estimate of the level of effort required. The recommended demonstration emphasizes development of an optical disk system which incorporates an order-of-magnitude increase in writing speed above the current state of the art.

Ready, John F.↗