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NASA NTRS1988

A performance/loss evaluation of SSME HPFTP turbine

An evaluation of component losses of the High Pressure Fuel Turbopump (HPFTP) in the Space Shuttle Main Engine (SSME) is performed using a mean-line prediction method. This is accompanied with an extensive review of loss correlations in the literature. The present prediction uses an existing gas path velocity triangle, real LH2 and H2O gas properties and loss correlations selected from the literature. The significant losses incurred in the HPFTP turbine include profile loss, secondary loss, and tip clearance loss. Results obtained from the present prediction are compared to those calculated from a quasi-three dimensional numerical analysis. Except for the clearance loss, the present loss coefficients are in general higher than their counterparts from the quasi-three dimensional analysis. The fact that the mean-line velocity data being unable to represent actual flow fields near the hub and the tip regions is largely responsible for the uncertainty involved in the present method. On the other hand, due mainly to the ad-hoc nature of the studies involved, the correlations currently available in the literature may not be suitable for accurate loss prediction of the particular rocket turbine in the SSME HPFTP. Further studies particularly in the areas of tip clearance loff, coolant loss, secondary loss, and their interactions are desirable. Fundamental phenomena concerning flow unsteadiness in wake shedding and turbulence are also important.

Chyu, Mingking K.↗

NASA NTRS1989

Advanced space transportation technologies

A wide range of propulsion technologies for space transportation are discussed in the literature. It is clear from the literature review that a single propulsion technology cannot satisfy the many mission needs in space. Many of the technologies tested, proposed, or in experimental stages relate to: chemical and nuclear fuel; radiative and corpuscular external energy source; tethers; cannons; and electromagnetic acceleration. The scope and limitation of these technologies is well tabulated in the literature. Prior experience has shown that an extensive amount of fuel needs to be carried along for the return mission. This requirement puts additional constraints on the lift off rocket technology and limits the payload capacity. Consider the possibility of refueling in space. If the return fuel supply is guaranteed, it will not only be possible to lift off more payload but also to provide security and safety of the mission. Exploration to deep space where solar sails and thermal effects fade would also be possible. Refueling would also facilitate travel on the planet of exploration. This aspect of space transportation prompts the present investigation. The particle emissions from the Sun's corona will be collected under three different conditions: in space closer to the Sun, in the Van Allen Belts; and on the Moon. It is proposed to convert the particle state into gaseous, liquid, or solid state and store it for refueling space vehicles. These facilities may be called space pump stations and the fuel collected as space fuel. Preliminary estimates of fuel collection at all three sites will be made. Future work will continue towards advancing the art of collection rate and design schemes for pumping stations.

Raj, Rishi S.↗

NASA NTRS1990

Tidal distortions in pairs of early-type galaxies

The authors are conducting an imaging survey of pairs of elliptical galaxies which has already produced interesting results. Some pairs present a common pattern of distortion interpreted in terms of tidal effects (Davoust and Prugniel, 1988; Prugniel et al., 1989). Other examples drawn from the literature (Borne and Hoessel, 1988; Colina and Perez-Fournon, 1990) share the same morphology. New cases and lists of the characteristics of 24 such systems. The authors' pairs are drawn from a sample of binary and multiple galaxies which has in turn been extracted from the CGCG, UGC (Nilson, 1973) and VV (Vorontsov-Velyaminov, 1959) catalogues. This sample includes that of Karachentsev (1972). It contains 1800 pairs, among which 700 are S - S or mixed morphology pairs. The authors are working on the remainder to produce a sample of close physical pairs of elliptical galaxies (they also include bulge dominated SO's since the morphological discrimination from ellipticals is often ambiguous, in particular for interacting galaxies). One of the interests of this work is to provide a sample selected on purely optical criteria, at variance with other works (e.g., Valentijn and Casertano, 1988). This will allow statistical studies of non-optical properties of these pairs (in particular radio emission). The authors have so far obtained charge-coupled device (CCD) images of 125 pairs with a 2m telescope and velocities' differences of 78 pairs were obtained using the 1.93 meter telescope of Observatoire de Haute Provence and from the literature. One is an optical pair (VV 190). Eighteen of our pairs present the morphological effect described in Davoust and Prugniel (1988): the external parts of each member are stretched in opposite senses in a direction rougly perpendicular to the pair axis. The proportion of 15 plus or minus 4 percent distorted pairs confirms previous estimates. Except for a few cases involving flattened galaxies with nearly aligned major axes which deserve careful detailed analysis (Prugniel, 1989), the apparent distortions do correspond to physical distortions. We have searched the literature for isophote maps showing this effect. In the survey of radio galaxies by Colina and Perez-Fournon (1990), 7 out of 20 pairs show this characteristic distortion.

Prugniel, Philippe↗

NASA NTRS1991

On the formulation of a minimal uncertainty model for robust control with structured uncertainty

In the design and analysis of robust control systems for uncertain plants, representing the system transfer matrix in the form of what has come to be termed an M-delta model has become widely accepted and applied in the robust control literature. The M represents a transfer function matrix M(s) of the nominal closed loop system, and the delta represents an uncertainty matrix acting on M(s). The nominal closed loop system M(s) results from closing the feedback control system, K(s), around a nominal plant interconnection structure P(s). The uncertainty can arise from various sources, such as structured uncertainty from parameter variations or multiple unsaturated uncertainties from unmodeled dynamics and other neglected phenomena. In general, delta is a block diagonal matrix, but for real parameter variations delta is a diagonal matrix of real elements. Conceptually, the M-delta structure can always be formed for any linear interconnection of inputs, outputs, transfer functions, parameter variations, and perturbations. However, very little of the currently available literature addresses computational methods for obtaining this structure, and none of this literature addresses a general methodology for obtaining a minimal M-delta model for a wide class of uncertainty, where the term minimal refers to the dimension of the delta matrix. Since having a minimally dimensioned delta matrix would improve the efficiency of structured singular value (or multivariable stability margin) computations, a method of obtaining a minimal M-delta would be useful. Hence, a method of obtaining the interconnection system P(s) is required. A generalized procedure for obtaining a minimal P-delta structure for systems with real parameter variations is presented. Using this model, the minimal M-delta model can then be easily obtained by closing the feedback loop. The procedure involves representing the system in a cascade-form state-space realization, determining the minimal uncertainty matrix, delta, and constructing the state-space representation of P(s). Three examples are presented to illustrate the procedure.

Belcastro, Christine M.↗

NASA NTRS1991

Linearized force representations for turbopump liquid annular seals

The analysis and the accompanying FORTRAN code, SEALPAL1, to simulate liquid annular seals with axial taper, Moody friction factors, and pre-swirl, are discussed. The output of the code includes all dynamic coefficients (stiffness, dampings, and inertias), leakage rate, torque, and horsepower loss. The computer code results were compared with five cases from the literature. The agreement was very good in almost all instances, except several predicted cross coupled stiffnesses were significantly lower than those appearing in the literature. This disagreement could reflect a theoretical or a programming error by the researcher or in the literature, or it could be a result of the difference in friction factor models or other assumptions employed.

Palazzolo, Alan B.↗

NASA NTRS1993

Space Science Laboratory Publications and Presentations

This document lists the significant publications and presentations of the Space Science Laboratory during the period January 1 - December 31, 1992. Entries in the main part of the document are categorized according to NASA Reports (arranged by report number), Open Literature, and Presentations (arranged alphabetically by title). Also included for completeness is an Appendix (arranged by report number) listing preprints issued by the Laboratory during this reporting period. Some of the preprints have not been published; those already published are so indicated. Most of the articles listed under Open Literature have appeared in refereed professional journals, books, monographs, or conference proceedings. Although many published abstracts are eventually expanded into full papers for publications in scientific and technical journals, they are often sufficiently comprehensive to include the significant results of the research reported. Therefore, published abstracts are listed separately in a subsection under Open Literature. The organizational code of the cognizant SSL branch or office is given at the end of each entry.

Moorehead, T. W.↗

NASA NTRS1994

Factors affecting the identification of phytoplankton groups by means of remote sensing

A literature review was conducted on the state of the art as to whether or not information about communities and populations of phytoplankton in aquatic environments can be derived by remote sensing. In order to arrive at this goal, the spectral characteristics of various types of phytoplankton were compared to determine first, whether there are characteristic differences in pigmentation among the types and second, whether such differences can be detected remotely. In addition to the literature review, an extensive, but not exhaustive, annotated bibliography of the literature that bears on these questions is included as an appendix, since it constitutes a convenient resource for anyone wishing an overview of the field of ocean color. The review found some progress has already been made in remote sensing of assemblages such as coccolithophorid blooms, mats of cyanobacteria, and red tides. Much more information about the composition of algal groups is potentially available by remote sensing particularly in water bodies having higher phytoplankton concentrations, but it will be necessary to develop the remote sensing techniques required for working in so-called Case 2 waters. It is also clear that none of the satellite sensors presently available or soon to be launched is ideal from the point of view of what we might wish to know; it would seem wise to pursue instruments with the planned characteristics of the Moderate Resolution Imaging Spectrometer-Tilt (MODIS-T) or Medium Resolution Imaging Spectrometer (MERIS).

Weaver, Ellen C.↗

NASA NTRS1993

Establishment of computerized numerical databases on thermophysical and other properties of molten as well as solid materials and data evaluation and validation for generating recommended reliable reference data

The Center for Information and Numerical Data Analysis and Synthesis, (CINDAS), measures and maintains databases on thermophysical, thermoradiative, mechanical, optical, electronic, ablation, and physical properties of materials. Emphasis is on aerospace structural materials especially composites and on infrared detector/sensor materials. Within CINDAS, the Department of Defense sponsors at Purdue several centers: the High Temperature Material Information Analysis Center (HTMIAC), the Ceramics Information Analysis Center (CIAC) and the Metals Information Analysis Center (MIAC). The responsibilities of CINDAS are extremely broad encompassing basic and applied research, measurement of the properties of thin wires and thin foils as well as bulk materials, acquisition and search of world-wide literature, critical evaluation of data, generation of estimated values to fill data voids, investigation of constitutive, structural, processing, environmental, and rapid heating and loading effects, and dissemination of data. Liquids, gases, molten materials and solids are all considered. The responsibility of maintaining widely used databases includes data evaluation, analysis, correlation, and synthesis. Material property data recorded on the literature are often conflicting, diverging, and subject to large uncertainties. It is admittedly difficult to accurately measure materials properties. Systematic and random errors both enter. Some errors result from lack of characterization of the material itself (impurity effects). In some cases assumed boundary conditions corresponding to a theoretical model are not obtained in the experiments. Stray heat flows and losses must be accounted for. Some experimental methods are inappropriate and in other cases appropriate methods are carried out with poor technique. Conflicts in data may be resolved by curve fitting of the data to theoretical or empirical models or correlation in terms of various affecting parameters. Reasons (e.g. phase transitions) must be found for unusual dependence or any anomaly. Such critical evaluation involves knowledge of theory, experience in measurement, familiarity with metallurgy (microstructural behavior) and not inconsiderable judgment. An examination of typical data compiled and analyzed by CINDAS shows that the thermal conductivity of a material reported in the literature may vary by a factor of two of more; the range of reported values increases as temperature increases reflecting the difficulty of high temperature measurements. Often only estimates of melt behavior are available, despite the importance of melt properties in modeling, welding, or other solidification processes. There may be only a few measurements available for properties such as kinematic viscosity, even for widely used materials such as stainless steel. In the face of such a paucity of existing data and in a national environment where too few new data are being generated it is nonetheless the responsibility of CINDAS to select and disseminate recommended values of a wide variety of thermophysical properties.

Ho, C. Y.↗

NASA NTRS1994

Space Sciences Laboratory publications and presentations, 1 January - 31 December, 1993

This document lists the significant publications and presentations of the Space Sciences Laboratory during the period January 1 to December 31, 1993. Entries in the main part of the document are categorized according to NASA Reports (arranged by report number), Open Literature, and Presentations (arranged alphabetically by title). Also included for completeness is an Appendix (arranged by report number) listing preprints issued by the Laboratory during this reporting period. Some of the preprints have not been published; those already published are so indicated. Most of the articles listed under Open Literature have appeared in refereed professional journals, books, monographs, or conference proceedings. Although many published abstracts are eventually expanded into full papers for publications in scientific and technical journals, they are often sufficiently comprehensive to include the significant results of the research reported. Therefore, published abstracts are listed separately in a subsection under Open Literature. The organizational code of the cognizant SSL branch or office is given at the end of each entry.

Moorehead, T. W.↗

NASA NTRS1995

Space Sciences Laboratory Publications and Presentations

This document lists the significant publications and presentations of the Space Sciences Laboratory during the period Jan. 1 - Dec. 31, 1994. Entries in the main part of the document are categorized according to NASA Reports (arranged by report number), Open Literature, and Presentations (arranged alphabetically by title). Also included for completeness is an appendix (arranged by report number) listing preprints issued by the laboratory during this reporting period. Some of the preprints have not been published; those already published are so indicated. Most of the articles listed under Open Literature have appeared in referenced professional journals, books, monographs, or conference proceedings. Although many published abstracts are eventually expanded into full papers for publications in scientific and technical journals, they are often sufficiently comprehensive to include the significant results of the research reported. Therefore, published abstracts are listed separately in a subsection under Open Literature. The organizational code of the cognizant SSL branch or office is given at the end of each entry.

Moorehead, T. W.↗

NASA NTRS1997

Space Sciences Laboratory Publications and Presentations: January 1 - December 31, 1996

This document lists the significant publications and presentations of the Space Sciences Laboratory during the period January 1 - December 31, 1996. Entries in the main part of the document are categorized according to NASA Reports (arranged by report number), Open Literature, and Presentations (arranged alphabetically by title). Also included for completeness is an Appendix (arranged by page number) listing preprints issued by the Laboratory during this reporting period. Some of the preprints have not been published; those already published are so indicated. Most of the articles listed under Open Literature have appeared in refereed professional journals, books, monographs, or conference proceedings. Although many published abstracts are eventually expanded into full papers for publications in scientific and technical journals, they are often sufficiently comprehensive to include the significant results of the research reported. Therefore, published abstracts are listed separately in a subsection under Open Literature. Questions or requests for additional information about the entries in this report should be directed to Gregory S. Wilson (ESO1; 544-7579) or to one of the authors. The organizational code of the cognizant SSL branch or office is given at the end of each entry.

Summers, F. G.↗

NASA NTRS1996

International Research Project on the Effects of Chemical Ageing of Polymers on Performance Properties: Chemical and Thermal Analysis

Work during the past six months has included significant research in several areas aimed at further clarification of the aging and chemical failure mechanism of thermoplastics (PVDF or Tefzel) pipes. Among the areas investigated were the crystallinity changes associated with both the Coflon and Tefzel after various simulated environmental exposures using X-ray diffraction analysis. We have found that significant changes in polymer crystallinity levels occur as a function of the exposures. These crystallinity changes may have important consequences on the fracture, fatigue, tensile, and chemical resistance of the materials. We have also noted small changes in the molecular weight distribution. Again these changes may result in variations in the mechanical and chemical properties in the material. We conducted numerous analytical studies with methods including X-ray Diffraction, Gel Permeation Chromatography, Fourier Transform Infrared Spectroscopy, Ultra- Violet Scanning Analysis, GC/Mass Spectrometry, Differential Scanning Calorimetry and Thermomechanical Analysis. In the ultra-violet analysis we noted the presence of an absorption band indicative of triene formation. We investigated a number of aged samples of both Tefzel and Coflon that were forwarded from MERL. We also cast films at SWT and subjected these films to a refluxing methanol 1% ethylene diamine solution. An updated literature search was conducted using Dialog and DROLLS to identify any new papers that may have been published in the open literature since the start of this project. The updated literature search and abstracts are contained in the Appendix section of this report.

Bulluck, J. W.↗

NASA NTRS1998

Space Sciences Laboratory Publications and Presentations

This document lists the significant publications and presentations of the Space Sciences Laboratory during the period January 1 - December 31, 1997. Entries in the main part of the document are categorized according to NASA Reports (arranged by report number), Open Literature, and Presentations (arranged alphabetically by title). Also included for completeness is an Appendix (arranged by page number) listing preprints issued by the Laboratory during this reporting period. Some of the preprints have not been published; those already published are so indicated. Most of the articles listed under Open Literature have appeared in refereed professional journals, books, monographs, or conference proceedings. Although many published abstracts are eventually expanded into full papers for publication in scientific and technical journals, they are often sufficiently comprehensive to include the significant results of the research reported. Therefore, published abstracts are listed separately in a subsection under Open Literature.

Summers, F. G.↗

NASA NTRS1995

Property-Based Software Engineering Measurement

Little theory exists in the field of software system measurement. Concepts such as complexity, coupling, cohesion or even size are very often subject to interpretation and appear to have inconsistent definitions in the literature. As a consequence, there is little guidance provided to the analyst attempting to define proper measures for specific problems. Many controversies in the literature are simply misunderstandings and stem from the fact that some people talk about different measurement concepts under the same label (complexity is the most common case). There is a need to define unambiguously the most important measurement concepts used in the measurement of software products. One way of doing so is to define precisely what mathematical properties characterize these concepts regardless of the specific software artifacts to which these concepts are applied. Such a mathematical framework could generate a consensus in the software engineering community and provide a means for better communication among researchers, better guidelines for analysis, and better evaluation methods for commercial static analyzers for practitioners. In this paper, we propose a mathematical framework which is generic, because it is not specific to any particular software artifact, and rigorous, because it is based on precise mathematical concepts. This framework defines several important measurement concepts (size, length, complexity, cohesion, coupling). It is not intended to be complete or fully objective; other frameworks could have been proposed and different choices could have been made. However, we believe that the formalism and properties we introduce are convenient and intuitive. In addition, we have reviewed the literature on this subject and compared it with our work. This framework contributes constructively to a firmer theoretical ground of software measurement.

Briand, Lionel↗

NASA NTRS1999

Space Sciences Laboratory Publications and Presentations: January 1 - December 31,1998

This document lists the significant publications and presentations of the Space Sciences Laboratory during the period January 1 - December 31, 1998. Entries in the main part of the document are categorized according to NASA Reports (arranged by report number), Open Literature, and Presentations (arranged alphabetically by title). Most of the articles listed under Open Literature have appeared in refereed professional journals, books, monographs, or conference proceedings. Although many published abstracts are eventually expanded into full papers for publication in scientific and technical journals, they are often sufficiently comprehensive to include the significant results of the research reported. Therefore, published abstracts are listed separately in a subsection under Open Literature. Questions or requests for additional information about the entries in this report should be directed to Gregory S. Wilson (ES01; 544-7579) or to one of the authors. The organizational code of the cognizant SSL branch or office is given at the end of each entry.

Summers, F. G.↗

NASA NTRS2000

Science Directorate Publications and Presentations

This document lists the significant publications and presentation of the Science Directorate during the period January 1-December 31, 1999. Entries in the main part of the document are categorized according to NASA Reports (arranged by report number). Open Literature, and Presentations (arranged alphabetically by title). Most of the articles listed under Open Literature have appeared in refereed professional journals, books, monographs, or conference proceedings. Although many published abstracts are eventually expanded into full papers for publication in scientific and technical journals, they are often sufficiently comprehensive to include the significant results of the research reported. Therefore, published abstracts are listed separately in a section under Open Literature.

Summers, F. G.↗

NASA NTRS2001

Science Directorate Publications and Presentations: January 1-December 31, 2000

This document lists the significant publications and presentations of the Science Directorate during the period January 1 - December 31, 2000. Entries in the main part of the document are categorized according to NASA Reports (arranged by report number), Open Literature, and Presentations (arranged alphabetically by title). Also included for completeness is an Appendix (arranged by page number). Most of the articles listed under Open Literature have appeared in refereed professional journals, books, monographs, or conference proceedings. Although many published abstracts are eventually expanded into full papers for publication in scientific and technical journals, they are often sufficiently comprehensive to include the significant results of the research reported. Therefore, published abstracts are listed separately in a subsection under Open Literature.

Summers, F. G.↗

NASA NTRS1994

A Study of High Altitude Hypersonic Flow-Field Radiation

This paper presents the results of the works carried out jointly at Stanford University and Ames Research Center under a grant from the Ballistic Missile Defense Organization (BMDO) (formerly the Strategic Defense Initiative Organization) to explain and understand the results of the two flight experiments, Bow Shock Ultra-Violet 1 and Bow Shock Ultra-Violet 2, carried out by the Organization. A portion of the material contained in this paper has been reported elsewhere in open literature. However, this paper provides (1) the details of scientific contents not available in those literature, (2) the links among those and the logical order of the efforts involved, and (3) some materials not contained in any open literature. The first author is responsible for execution of the work; the second author directed the work of the first author. In the two flight experiments mentioned above, the spectra of radiation in the ultraviolet wavelength range incident on the stagnation point of a blunt body were measured at the flight speeds of 3.8 and 5.2 km/sec over a wide range of altitudes. The results were compared first with the calculations made using the original version of the NEQAIR/STRAP codes written earlier by the second author. At low altitudes, the calculations agreed with the measurement. However, at high altitudes, the calculations underestimated the intensity of the radiation by several orders of magnitudes. A shock tube experiment was carried out at CALSPAN and a plasma-torch experiment was carried out at Stanford University to produce experimental data to help explain the discrepancy. In addition, the shock tube experiment at Ames Research Center carried out independently of the BMDO was also found to be relevant to this question. In this paper, several theoretical models are developed and calculations using the models were carried out to explain the results not only of the flight experiments but also of the CALSPAN, Stanford, and Ames experiments. The are: (1) the diffusion model for the rotational mode to explain the slowness of rotational excitation, (2) assignment of different vibrational temperatures and different relaxation rates for different molecules, and (3) the modification of the NEQAIR code to accommodate the new experimental data. This paper shows that the discrepancy between the flight data and calculation is smaller with the present model, but is still substantial.

Moreau, Stephane↗