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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

Reliability Assessment Of Conceptual Launch Vehicles

Planning is underway for new NASA missions to the moon and to MARS. These missions carry a great deal of risk, as the Challenger and Columbia accidents demonstrate. In order to minimize the risks to the crew and the mission, risk reduction must be done at every stage, not only in quality manufacturing, but also in design. It is necessary, therefore, to be able to compare the risks posed in different launch vehicle designs. Further, these designs have not yet been implemented, so it is necessary to compare these risks without being able to test the vehicles themselves. This paper will discuss some of the issues involved in this type of comparison. It will start with a general discussion of reliability estimation. It will continue with a short look at some software designed to make this estimation easier and faster. It will conclude with a few recommendations for future tools.

Bloomer, Lisa A.↗
NASA NTRS1988

NDE detectability of fatigue-type cracks in high-strength alloys: NDI reliability assessments

This program was conducted to generate quantitative flaw detection capability data for the nondestructive evaluation (NDE) techniques typically practiced by aerospace contractors. Inconel 718 and Haynes 188 alloy test specimens containing fatigue flaws with a wide distribution of sizes were used to assess the flaw detection capabilities at a number of contractor and government facilities. During this program 85 inspection sequences were completed presenting a total of 20,994 fatigue cracks to 53 different inspectors. The inspection sequences completed included 78 liquid penetrant, 4 eddy current, and 3 ultrasonic evaluations. The results of the assessment inspections are presented and discussed. In generating the flaw detection capability data base, procedures for data collection, data analysis, and specimen care and maintenance were developed, demonstrated, and validated. The data collection procedures and methods that evolved during this program for the measurement of flaw detection capabilities and the effects of inspection variables on performance are discussed. The Inconel 718 and Haynes 188 test specimens that were used in conducting this program and the NDE assessment procedures that were demonstrated, provide NASA with the capability to accurately assess the flaw detection capabilities of specific inspection procedures being applied or proposed for use on current and future fracture control hardware program.

Christner, Brent K.↗
NASA NTRS1992

A probabilistic fracture mechanics approach for structural reliability assessment of space flight systems

A probabilistic fracture mechanics approach for predicting the failure life distribution due to subcritical crack growth is presented. A state-of-the-art crack propagation method is used in a Monte Carlo simulation to generate a distribution of failure lives. The crack growth failure model expresses failure life as a function of stochastic parameters including environment, loads, material properties, geometry, and model specification errors. A stochastic crack growth rate model that considers the uncertainties due to scatter in the data and mode misspecification is proposed. The rationale for choosing a particular type of probability distribution for each stochastic input parameter and for specifying the distribution parameters is presented. The approach is demonstrated through a probabilistic crack growth failure analysis of a welded tube in the Space Shuttle Main Engine. A discussion of the results from this application of the methodology is given.

Sutharshana, S.↗
NASA NTRS2010

Constellation Program (CxP) Crew Exploration Vehicle (CEV) Parachute Assembly System (CPAS) Independent Design Reliability Assessment

This report documents the activities, findings, and NASA Engineering and Safety Center (NESC) recommendations of a multidiscipline team to independently assess the Constellation Program (CxP) Crew Exploration Vehicle (CEV) Parachute Assembly System (CPAS). This assessment occurred during a period of 15 noncontiguous months between December 2008 and April 2010, prior to the CPAS Project's Preliminary Design Review (PDR) in August 2010.

Kelly, Michael J.↗
NASA NTRS2010

Constellation Program (CxP) Crew Exploration Vehicle (CEV) Parachute Assembly System (CPAS) Independent Design Reliability Assessment: Appendices - Volume 2

This document contains the Appendices to the report documenting the activities, findings, and NASA Engineering and Safety Center (NESC) recommendations of a multidiscipline team to independently assess the Constellation Program (CxP) Crew Exploration Vehicle (CEV) Parachute Assembly System (CPAS). The assessment occurred during a period of 15 noncontiguous months between December 2008 and April 2010, prior to the CPAS Project's Preliminary Design Review (PDR) in August 2010.

Kelly, Michael J.↗
NASA NTRS2018

MRI-based Quantification of Optic Nerve Tortuosity and Subarachnoid Space 3D Geometry: Reliability Assessment

In some astronauts, long-duration space flight results in ophthalmic structure changes such as optic nerve (ON) kinking, ON distention, and globe flattening. Assessment of the ON and ON sheath (ONS) may provide insight into the mechanisms responsible for ophthalmic structure changes seen in a subset of astronauts. Automated and manual methods were developed to quantify 3D ON/ONS geometry and ON tortuosity.

Rohr, Jesse J.↗