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Results for “Design Evaluation Criteria”

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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Design of a Vehicle Based Intervention System to Prevent Ozone Loss

This project was designed to be completed over a period of three years. Overall project goals were: (1) To understand the processes that contribute to stratospheric ozone loss; (2) To determine the best prevention scheme for loss; (3) To design a delivery vehicle to accomplish the prevention scheme. The 1994-1995 design objectives included: (1) To review the results of the 1993-1994 design team, including a reevaluation of the major assumptions and criteria selected to choose a vehicle; (2) To evaluate preliminary vehicle concepts and perform quantitative trade studies to select the optimal vehicle concept.

Cole, Robin↗
NASA NTRS1992

On the use of a three-dimensional Navier-Stokes solver for rocket engine pump impeller design

A 3D Reynolds-averaged Navier-Stokes Solver and a Fast Grid Generator (FGG), developed specially for centrifugal impeller design, were incorporated into the pump impeller design process. The impeller performance from the CFD analysis was compared to one-dimensional prediction. Both analyses showed good agreement of the impeller hydraulic efficiency, 94.5 percent, but with an 8 percent discrepancy of Euler head prediction. The impeller blade angle, discharge hub to shroud width, axial length and blade stacking were systematically changed to achieve an optimum impeller design. Impeller overall efficiency, loss distribution, hub-to-tip flow angle distortion and blade-to-blade flow angle change are among those criteria used to evaluate impeller performance. Two grid sizes, one with 10 K grid points and one with 80 K grid points were used to evaluate grid dependency issues. The effects of grid resolution on the accuracy and turnaround time are discussed. In conclusion, it is demonstrated that CFD can be effectively used for design and optimization of rocket engine pump components.

Chen, Wei-Chung↗
NASA NTRS1991

Application of multiple criteria decision methods in space exploration initiative design and planning

Fellowship activities were directed towards the identification of opportunities for application of the Multiple Criteria Decision Making (MCDM) techniques in the Space Exploration Initiative (SEI) domain. I identified several application possibilities and proposed demonstration application in these three areas: evaluation and ranking of SEI architectures, space mission planning and selection, and space system design. Here, only the first problem is discussed. The most meaningful result of the analysis is the wide separation between the two top ranked architectures, indicating a significant preference difference between them. It must also be noted that the final ranking reflects, to some extent, the biases of the evaluators and their understanding of the architecture.

Masud, Abu S. M.↗
NASA NTRS1972

Space Storable Propellant Performance Gas/Liquid Like-Doublet Injector Characterization

A 30-month applied research program was conducted, encompassing an analytical, design, and experimental effort to relate injector design parameters to simultaneous attainment of high performance and component (injector/thrust chamber) compatibility for gas/liquid space-storable propellants. The gas/liquid propellant combination selected for study was FLOX (82.6% F2)/ambient temperature gaseous methane. The injector pattern characterized was the like-(self)-impinging doublet. Program effort was apportioned into four basic technical tasks: injector and thrust chamber design, injector and thrust chamber fabrication, performance evaluation testing, and data evaluation and reporting. Analytical parametric combustion analyses and cold flow distribution and atomization experiments were conducted with injector segment models to support design of injector/thrust chamber combinations for hot fire evaluation. Hot fire tests were conducted to: (1) optimize performance of the injector core elements, and (2) provide design criteria for the outer zone elements so that injector/thrust chamber compatibility could be achieved with only minimal performance losses.

Falk, A. Y.↗
NASA NTRS1976

Zero-G Workstation Design

Zero-g workstations were designed throughout manned spaceflight, based on different criteria and requirements for different programs. The history of design of these workstations is presented along with a thorough evaluation of selected Skylab workstations (the best zero-g experience available on the subject). The results were applied to on-going and future programs, with special emphasis on the correlation of neutral body posture in zero-g to workstation design. Where selected samples of shuttle orbiter workstations are shown as currently designed and compared to experience gained during prior programs in terms of man machine interface design, the evaluations were done in a generic sense to show the methods of applying evaluative techniques.

Gundersen, R. T.↗
NASA NTRS1981

Interruption as a test of the user-computer interface

In order to study the effects different logic systems might have on interrupted operation, an algebraic calculator and a reverse polish notation calculator were compared when trained users were interrupted during problem entry. The RPN calculator showed markedly superior resistance to interruption effects compared to the AN calculator although no significant differences were found when the users were not interrupted. Causes and possible remedies for interruption effects are speculated. It is proposed that because interruption is such a common occurrence, it be incorporated into comparative evaluation tests of different logic system and control/display system and that interruption resistance be adopted as a specific design criteria for such design.

Kreifeldt, J. G.↗
NASA NTRS1990

Early surface habitation elements for planetary exploration missions

Rigid pressure vessel concepts appropriate for initial, crew-supporting exploration activities on planetary surfaces are discussed and compared. The problem of early exploration crew support is first bounded and outlined. The studied trade-space spans five crew sizes from 4 to 12, and three diameters of module structure from 4.4 to 10 m. Other considerations of gravity, orientation, structure and topology are also used as parameters. The paper illustrates application of a technique which uses interpolation across a field of point-designs to yield trade results. Methods to reduce the option set from 1480 to 30 are presented. Reproducible evaluation criteria are explained and applied, to enable selecting the most promising candidates. A final concept is synthesized for further study use, and presented via configuration drawings and weight statements. It is a 7.6 m diameter module, with two floors running lengthwise and a cross-sectioning pressure bulkhead. Versions for four, six and perhaps eight people can be landed fully integrated on the moon.

Sherwood, Brent↗
NASA NTRS1991

Alert generation and cockpit presentation for an integrated microburst alerting system

Alert generation and cockpit presentation issues for low-level wind shear (microburst) alerts are investigated. Alert generation issues center on development of a hazard criterion which allows integration of both ground-based and airborne wind shear detection systems to form an accurate picture of the aviation hazard posed by a particular wind shear situation. A methodology for testing of hazard criteria through flight simulation has been developed, and has been used to examine the effectiveness and feasibility of several possible criteria. Also, an experiment to evaluate candidate graphical cockpit displays for microburst alerts using a piloted simulator has been designed.

Wanke, Craig↗
NASA NTRS1991

Alert generation and cockpit presentation for an integrated microburst alerting system

Alert generation and cockpit presentation issues for low level wind shear (microburst) alerts are investigated. Alert generation issues center on the development of a hazard criterion which allows integration of both ground based and airborne wind shear detection systems to form an accurate picture of the aviation hazard posed by a particular wind shear situation. A methodology for the testing of a hazard criteria through flight simulation has been developed, and has been used to examine the effectiveness and feasibility of several possible criteria. Also, an experiment to evaluate candidate graphical cockpit displays for microburst alerts using a piloted simulator has been designed.

Wanke, Craig↗
NASA NTRS1966

Storable Propellant Combustion Instability Program at Lewis Research Center

An experimental program at Lewis Research Center investigates acoustical-mode combustion instability in liquid propellant rockets. One phase of this program is concerned with nitrogen tetroxide and a 50-50 fuel blend of hydrazine-UDMH. Effects on combustor stability and performance by variations in injection velocities, impingement angle and distance, amd thrust per element of triplet injectors were studied in a 10.77-inch- diameter cylindrical combustor at chamber pressures of 100 and 300 psia. Nominal thrust levels were 6700 and 20 000 pounds. Stability rating was accomplished by the use of various size RDX explosive charges to generate tangential pressure disturbances. The injection velocity effect correlated by using a ratio V(sub o)/V(sub f). Stability correlation with V(sub o)/V(sub f) resulted in a sharply humped curve with maximum stability at a ratio of 1.2. Performance decreased with increase in V(sub o)/V(sub f) after a maximum at 0.7, which agreed fairly well with the "uniform mixture ratio distribution" criteria of the Jet Propulsion Laboratory. Variation of impingement angle from 38 deg to 120 deg indicated that performance correlated with the absolute velocity ratio V(sub o)/V(sub f), but stability correlation appeared to be best with a velocity ratio using the radial component of the fuel injection velocity V(sub o)/V(sub fr). Impingement distances from 0.5 to 1.0 inch appeared to have only slight effect on stability and performance. Investigation of injector thrust per element for V(sub o)/V(sub fr) ranging from 0.8 to 2.8 yielded convex maxima curves. Acoustic liners were also tested to improve a liner design computer program, to obtain design criteria, and to develop flight-type liners. A marginally stable and spontaneously unstable combustor were used to evaluate linear configurations. All liners were effective in the marginally stable configuration, and only liners with large theoretical absorptivity were successful in the spontaneously unstable combustor.

Tabata, William K.↗
NASA NTRS2002

The SOFIA Aircraft and its Modification

The primary focus of this paper is to describe the challenges involved in creating this highly modified aircraft that carries a twenty ton telescope to the Stratosphere and then loiters at this desired altitude to act as the observatory "dome" or platform. When the aircraft has reached its nominal cruise condition in the stratosphere of Mach 0.84, a large cavity door opens (the dome opens), exposing a large portion of the interior of the fuselage containing the telescope optics, directly to the Universe. The breadth of topics covered in this paper includes; the relevant criteria and the evaluation process that resulted in the selection of a Boeing 747-SP, the evolution of the design concept, a description of the structural modification including the analysis methods and tools, the aerodynamic issues associated with an open port cavity and how they were addressed, the aero-loads/disturbances imparted to the telescope and how they were measured in the wind tunnel and extrapolated to full size. For completeness, this paper also provides a brief overview of the SOFIA project including the joint project arrangement between NASA and DLR, a top level overview of the science objectives and the resulting requirements, and finally the current project status.

Kunz, Nans↗
NASA NTRS2003

Process-Based Cost Estimation for Ramjet/Scramjet Engines

Process-based cost estimation plays a key role in effecting cultural change that integrates distributed science, technology and engineering teams to rapidly create innovative and affordable products. Working together, NASA Glenn Research Center and Boeing Canoga Park have developed a methodology of process-based cost estimation bridging the methodologies of high-level parametric models and detailed bottoms-up estimation. The NASA GRC/Boeing CP process-based cost model provides a probabilistic structure of layered cost drivers. High-level inputs characterize mission requirements, system performance, and relevant economic factors. Design alternatives are extracted from a standard, product-specific work breakdown structure to pre-load lower-level cost driver inputs and generate the cost-risk analysis. As product design progresses and matures the lower level more detailed cost drivers can be re-accessed and the projected variation of input values narrowed, thereby generating a progressively more accurate estimate of cost-risk. Incorporated into the process-based cost model are techniques for decision analysis, specifically, the analytic hierarchy process (AHP) and functional utility analysis. Design alternatives may then be evaluated not just on cost-risk, but also user defined performance and schedule criteria. This implementation of full-trade study support contributes significantly to the realization of the integrated development environment. The process-based cost estimation model generates development and manufacturing cost estimates. The development team plans to expand the manufacturing process base from approximately 80 manufacturing processes to over 250 processes. Operation and support cost modeling is also envisioned. Process-based estimation considers the materials, resources, and processes in establishing cost-risk and rather depending on weight as an input, actually estimates weight along with cost and schedule.

Singh, Brijendra↗
NASA NTRS1978

Toward a laminar-flow-control transport

Analyses were conducted to define a practical design for an advanced technology laminar flow control (LRC) transport for initial passenger operation in the early 1990's. Mission requirements, appropriate design criteria, and level of technology for the study aircraft were defined. The characteristics of the selected configuration were established, aircraft and LFC subsystems compatible with the mission requirements were defined, and the aircraft was evaluated in terms of fuel efficiency. A wing design integrating the LFC ducting and metering system into advanced composite wing structure was developed, manufacturing procedures for the surface panel design were established, and environmental and structural testing of surface panel components were conducted. Test results revealed a requirement for relatively minor changes in the manufacturing procedures employed, but have shown the general compatibility of both the selected design and the use of composite materials with the requirements of LFC wing surface panels.

Sturgeon, R. F.↗
NASA NTRS2002

TIES for Dummies 3rd Edition (Technology Identification, Evaluation, and Selection) Basic how to's to implement the TIES method

The TIES method is a forecasting environment whereby the decision-maker has the ability to easily assess and trade-off the impact of various technologies without sophisticated and time-consuming mathematical formulations. TIES provides a methodical approach where technically feasible alternatives can be identified with accuracy and speed to reduce design cycle time, and subsequently, life cycle costs, and was achieved through the use of various probabilistic methods, such as Response Surface Methodology and Monte Carlo Simulations. Furthermore, structured and systematic techniques are utilized from other fields to identify possible concepts and evaluation criteria by which comparisons can be made. This objective is achieved by employing the use of Morphological Matrices and Multi-Attribute Decision Making techniques. Through the execution of each step, a family of design alternatives for a given set of customer requirements can be identified and assessed subjectively or objectively. This methodology allows for more information (knowledge) to be brought into the earlier phases of the design process and will have direct implications on the affordability of the system. The increased knowledge allows for optimum allocation of company resources and quantitative justification for program decisions. Finally, the TIES method provided novel results and quantitative justification to facilitate decision making in the early stages of design so as to produce affordable and quality products.

Kirby, Michelle R.↗
NASA NTRS2013

A Tool for the Automated Design and Evaluation of Habitat Interior Layouts

The objective of space habitat design is to minimize mass and system size while providing adequate space for all necessary equipment and a functional layout that supports crew health and productivity. Unfortunately, development and evaluation of interior layouts is often ignored during conceptual design because of the subjectivity and long times required using current evaluation methods (e.g., human-in-the-loop mockup tests and in-depth CAD evaluations). Early, more objective assessment could prevent expensive design changes that may increase vehicle mass and compromise functionality. This paper describes a new interior design evaluation method to enable early, structured consideration of habitat interior layouts. This interior layout evaluation method features a comprehensive list of quantifiable habitat layout evaluation criteria, automatic methods to measure these criteria from a geometry model, and application of systems engineering tools and numerical methods to construct a multi-objective value function measuring the overall habitat layout performance. In addition to a detailed description of this method, a C++/OpenGL software tool which has been developed to implement this method is also discussed. This tool leverages geometry modeling coupled with collision detection techniques to identify favorable layouts subject to multiple constraints and objectives (e.g., minimize mass, maximize contiguous habitable volume, maximize task performance, and minimize crew safety risks). Finally, a few habitat layout evaluation examples are described to demonstrate the effectiveness of this method and tool to influence habitat design.

Simon, Matthew A.↗
NASA NTRS1972

A study of volatile contaminants in recovered water

The recovery and reuse of water during long term space flight is discussed. Particular attention was given to obtaining basic information on the volatile impurities in urine samples and in water recovered from urine by distillation. Data also cover laboratory distillation tests to determine the nature and extent of volatile constituents in the distillate and an evaluation of possible problems in distillation due to iodine used for control of microbial contamination. Efforts made to develop design criteria for distillation equipment to minimize the problems of volatile contaminants various methods which might be used for purification subsequent to recovery are included.

Mckee, H. C.↗
NASA NTRS1976

Optimal control of a low wing-loading STOL aircraft

Linear optimal quadratic control theory is applied to a low wing-loading STOL aircraft for ride quality and flight path following. Design criteria include minimum rms response to wind turbulence and desired transient response characteristics. Design techniques include proper choosing of design versus evaluation models, choosing appropriate performance index responses, and use of classical evaluation techniques. Results are obtained through a combination of frequency response shaping and gust observation. Effects of control rate and authority saturation are examined with a new rapid calculation of random input describing functions. Parameter sensitivity is also evaluated using a Liapunov type matrix equation.

Cunningham, T. B.↗