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Viewing 61 to 90 of 36595
1990-07-01
Technical Paper
901266
E. Cantwell, T. Shenk, P. Robinson, R. Upadhye
A development project for a design workstation for advanced life-support systems (called the DAWN Project, for Design Assistant Workstation), incorporating qualitative simulation, required the implementation of a useful qualitative simulation capability and the integration of qualitative and quantitative simulations such that simulation capabilities are maximized without duplication. The reason is that to produce design solutions to a system goal, the behavior of the system in both a steady and perturbed state must be represented. We report here on the Qualitative Simulation Tool (QST), on an expert-system-like model building and simulation interface toll called Scratchpad (SP), and on the integration of QST and SP with more conventional, commercially available simulation packages now being applied in the evaluation of life-support system processes and components.
1990-07-01
Technical Paper
901273
N. Morozumi, H. Sakata, M. Komori, S. Oshima, K. Mimura, M. Furukawa, Y. Ishii, Y. Miyazaki
Toshiba, under contract to NASDA is studying two-phase fluid loops (TPFL) as a thermal management system for future space platforms. For these fluid loops, two types of volumetric pumps, a trochoid gear pump and a scroll pump, are being developed, because volumetric pumps are, among others, less sensitive to cavitation. Recently, we designed and fabricated a scroll pump for our 5kW heat rejection TPFL in order to achieve a continuous and quiet operation of the system, which is required for space use. This scroll pump has four scroll vanes, two fixed and two orbiting ones, to reduce pulsation of flow. This paper reports the performance test results of a bread board model (BBM). The trochoid gear pump completed up to the BBM level, is also designed under the same requirements for comparison. Component tests of the pumps are carried out prior to installation into the TPFL. As expected, the scroll pump showed weaker vibration and lower noise.
1990-07-01
Technical Paper
901274
M. D. Parfentley
The paper presents the results of the visual investigations of the working fluid vapour and non-condensible gaseous impurities interaction in low temperature heat pipe (LTHP) condensation zone. The effect of the transferred heat flow amount on the vapour and non-condensible gaseous impurity (NCG) separation is established. The obtained dependance allows to determine the minimal amount of the transferred heat flow from which the vapour and NCG will be dinamic mixed and the temperature profile will be simmetry in the heat pipe condensation zone. Water, ethanol, acetone, Freon-11 were used as the working fluid, while air, argon and helium as NCG.
1990-07-01
Technical Paper
901276
V. Ya. Sasin, I. A. Zelenov, V. G. Zuev, E. Yu. Kotlyarov
The mathematical model of capillary pump loop (CPL) with the capillary pump for a conditions of radiative heat removal in the condenser has been considered. The CPL calculation results of both functional characteristics are being analised with the presence of in flow heat from the outside sources and the influence of non-condensing gases and mass forces on the starting and dynamic characteristics of the installation. The heat transfer system is shown to possess controlling properties.
1990-07-01
Technical Paper
901267
Robert C. DaLee, Allen S. Bacskay, James C. Knox
This paper presents an updated overview of the Computer Aided System Engineering and Analysis (CASE/A)-ECLSS series modeling package. CASE/A is an Environmental Control and Life Support System (ECLSS) and Active Thermal Control System (ATCS) analysis and trade study tool developed primarily for VAX mainframe usage. The program was developed under NASA MSFC contract NAS8-36407 and is currently being used by MSFC and selected support contractors to support their Space Station Freedom WP-01 ECLSS preliminary design modeling activities. Many new additions and enhancements to the program have been incorporated since the first paper was presented on the topic three years ago. An extensive components verification program was completed to assure component modeling validity based on actual test data from the Phase II comparative test program recently completed at MSFC.
1990-07-01
Technical Paper
901268
Matthew Kolodney, Bruce C. Conger
A computer modeling tool is being developed for the detailed transient modeling of an Extravehicular Activity Atmospheric Control Subsystem (EVA ACS). An EVA ACS includes the astronaut, CO2 removal, moisture control, temperature control, and oxygen make-up components. This modeling tool will be used in trade studies evaluating competing components and subsystems to guide the selection and development of hardware for lunar and Martian missions. Several computerized modeling packages already exist, but no single program has all the capabilities needed. These capabilities include models of all EVA components on both steady-state and transient bases and sophisticated, general-purpose chemical process modeling capabilities.
1990-07-01
Technical Paper
901269
H. A. Preisig, Tae-Yeong Lee, Frank Little
Abstract: Based on the canonical decomposition of Physical-Chemical-Biological (PCB)-systems, a prototype kernel has been developed to efficiently model alternative life-support systems. It supports (i) the work in an interdisciplinary group through an easy-to-use mostly graphical interface, (ii) modularized object-oriented model representation, (iii) reuse of models, (iv) inheritance of structures from model object to model object, (v) model data base.
1990-07-01
Technical Paper
901281
H. S. Cullingford, W. P. Bennett, W. A. Holley, J. G. Carnes, P. S. Jones
The Controlled Ecological Life Support System (CELSS) Emulator is operational for computer simulations of integrated CELSS operations involving humans, plants, process machinery, and reservoirs while the development of new capabilities continues. The Version 2.0 of the CELSS Emulator has been implemented to specify events, view data during model runs, generate data sets, store libraries of results for further analysis, and also display plots of model variables as a function of time. This paper describes a five-year simulation of two mission scenarios consisting of 14 different “events” that could take place at a lunar outpost. The time-dependent status of the life support consumables was calculated in response to the two selected mission scenarios. This application demonstrates that complex sequences of events are reproducible for understanding of integrated mission operations.
1990-07-01
Technical Paper
901278
Hatice S. Cullingford, Steven H. Schwartzkopf
Past spacecraft life support systems have used open-loop technologies that were simple and sufficiently reliable to demonstrate the feasibility of crewed spaceflight. A critical technology area needing development in support of both long duration missions and the establishment of lunar or planetary bases is regenerative life support. The subject of this paper is an ongoing study for a conceptual design of a Lunar-Base Controlled Ecological Life Support System (LCELSS) to support a crew size ranging from 4 to 100. An initial description of the LCELSS subsystems is provided within the framework of the conceptual design. The system design includes both plant (algae and higher plant) and animal species as potential food sources.
1989-09-01
Technical Paper
892289
G. R. Saaris, R. D. Gilkey, K. L. Smit, E. N. Tinoco
The application of a three-dimensional transonic flow analysis method, TRANAIR, is explored from the point of view of a user. Detailed features of the program are outlined to give a better understanding of capability. Numerous results are presented to show some of the complex configurations which have been analyzed. In particular, examples are provided which show the application to turbofan engine installation on transport aircraft.
1989-09-01
Technical Paper
892287
David Lednicer
This paper reports on the analysis of several further canard configured aircraft using the VSAERO low-order panel method. Aircraft analyzed within include the Rutan VariEze, Defiant, Predator, Catbird and Triumph. In all cases VSAERO models of the complete aircraft have been used to calculate the aerodynamic performance of the aircraft. Comparisons of these results with flight test and wind tunnel data are included where data are available. Results presented herein show VSAERO to be reasonably accurate in predicting aircraft neutral point. Induced drag predictions tend to be inconsistent and future incorporation of a Trefftz Plane in VSAERO will probably rectify these problems. Overall, VSAERO is shown to be a useful tool for the aircraft design process.
1989-09-01
Technical Paper
892288
R. D. Gregg, R. W. Hoch, P. A. Henne
The incorporation of divergent trailing-edge (DTE) technology into the design of a derivative wing is pres ented. The structural constraints imposed by the derivative approach will be reviewed with respect to their impact on the wing design. The predicted drag and buffet characteristics, derived using a combination of computational fluid dynamics (CFD) and empirically developed methods, are compared to wind tunnel measured characteristics. Calculated and measured results show a significant improvement in the performance of the derivative wing due to the integration of DTE airfoil technology.
1989-09-01
Technical Paper
892298
Ray Hill, Tim E. Heller
A new rapid modeling system, Optical Fabrication, uses a high-powered steered beam visible wavelength laser and low-shrink photopolymers to create model parts. The system speed and accuracy of Optical Fabrication provides new opportunities for developing composite, injection molded, or investment cast parts and developing more efficient manufacturing processes.
1989-09-01
Technical Paper
892315
James L. Pittman
A scramjet exhaust simulation technique for hypersonic wind tunnel testing has been developed. Mixtures of Argon and Freon correctly match the inviscid simulation parameters of Mach number, static-pressure ratio, and the ratio of specific heats at the combustor exit location; this simulation is accomplished at significantly reduced temperatures and without combustion. An investigation of nozzle parametrics in a Mach 6 freestream showed that the external nozzle ramp angle, the cowl trailing-edge angle, an external nozzle flow fence and the nozzle static-pressure ratio significantly affected the external nozzle thrust and pitching moment as measured by the integration of surface-pressure data. A comparison of Argon-Freon and air exhaust simulation showed that the external nozzle thrust and pitching moment were in error by roughly a factor of 2 using air due to the incorrect match of the ratio of specific heats.
1989-09-01
Technical Paper
892314
Shivakumar Srinivasant, Charles R. McClinton, Pradeep S. Kamath
Abstract The numerical simulation of a three-dimensional turbulent, reacting flow through the entire Langley parametric scramjet engine has been obtained using a piecewise elliptic approach. The last section in the combustor has been analyzed using a parabolized Navier-Stokes code. The facility nozzle flow was analyzed as a first step. The outflow conditions from the nozzle were chosen as the inflow conditions of the scramjet inlet. The nozzle and the inlet simulation were accomplished by solving the three-dimensional Navier-Stokes equations with a perfect gas assumption. The inlet solution downstream of the scramjet throat was used to provide inflow conditions for the combustor region. The first two regions of the combustor were analyzed using the MacCormack's explicit scheme. However, the source terms in the species equations were solved implicitly. The finite rate chemistry was modeled using the two-step reaction model of Rogers and Chinitz.
1989-09-01
Technical Paper
892320
Robert C. Allen, Howard L. Schreyer
Knowledge of the force history is crucial for evaluating the performance of structures and mechanical components. Since direct force measurement is impossible or impractical in many cases, alternative methods must be used. For an elastic body, a method has been developed employing the equations of motion which provide an expression for the applied force as a sum of weighted accelerations (SWA). Since this method is relatively new, its sensitivity to errors caused by inaccurate accelerometer data, or poor gauge placement, must be characterized and well understood for simple structures before the SWA can be applied to large, complex structures. In this paper, these error sources are investigated independently through numerical simulations of a simple beam. The conclusion reached is that the predictive capability of the SWA is not significantly affected by small errors in the accelerometer data or non-Ideal gauge placement.
1989-09-01
Technical Paper
892313
David E. Hahne, James M. Luckring, Peter F. Covell, W. Pelham Phillips, Gregory M. Gatlin, John D. Shaughnessy, Luat T. Nguyen
Wind tunnel investigations were conducted as part of an effort to develop a stability and control database for an aerospace plane concept across a broad range of Mach numbers. The generic conical design used in these studies represents one of a number of concepts being studied for this class of vehicle. The baseline configuration incorporated a 5° cone forebody, a 75.96° delta wing, a 16°leading-edge sweep deployable canard and a centerline vertical tail. Tests were conducted in the following NASA-Langley facilities spanning a Mach range of 0.1 to 6:30- by 60-Foot Tunnel,14- by 22-Foot Subsonic Tunnel, Low Turbulence Pressure Tunnel, National Transonic Facility, Unitary Plan Wind Tunnel, and the 20 Inch Mach 6 Tunnel. Data were collected for a number of model geometry variations and test conditions in each facility. This paper highlights some of the key results of these investigations pertinent to stability considerations about all three axes.
1989-09-01
Technical Paper
892097
K. H. Luo, H. Daneshyar
The three velocity components and turbulence intensity were measured at the valve curtains around the two inlet valves of a four-valve s.i. engine with a pent-roof chamber. The measurements were made using hotwire anemometry in a steady-flow rig. Data were collected over a wide range of valve lifts and flow rates. The results show that the velocity profiles are strongly dependent on the valve lift and the surrounding geometry but almost insensitive to the flow rate. Flow separations are identified at certain azimuthal locations for large valve lifts. The turbulence intensity varies around the valve peripheries and across the valve gaps, as do the exit angles of the issuing flows. Their profiles are affected by flow separations from the valve seats and faces and by flow interferences between the two inlet valves. These detailed profiles can be used as boundary for multi-dimensional in-cylinder flow models.
1989-09-01
Technical Paper
892114
Yoshinori Yamaguchi, Masahiko Takesue, Takeshi Maruya, Takashi Nagashima
In this work, the connecting rod bearing seizures as one of the problems latent to the high-output, high-speed engines are investigated. Studies are conducted on the evaluation of anti-seizure properties of a single connecting rod bearing installed in the test rig as well as in commercial engines. As the results of the former study, the bearing wear is affected by the rod surface roughness (Rmax ) and the oil temperature (viscosity). Further, frequent metal to metal contacts of bearings are observed by the electrical measuring apparatus under higher temperature, and full load conditions. While in the latter, it is found the total heat generated of the bearing is the important factor affective to the bearing seizures, and can be analyzed by using PV value, rod surface roughness and oil viscosity.
1989-09-01
Technical Paper
892085
Rolf D. Reltz, Tang-wel Kuo
Multi-dimensional computations were made to assess the effect of crevice flows through piston-cylinder-ring crevices on combustion and engine-out hydrocarbon emissions. The computations were made using the KIVA code with a characteristic time combustion sub model that accounts for laminar kinetics and turbulent-mixing effects. The crevice-flow boundary conditions were specified using a phenomenological crevice-flow model. A central-ignition pancake-chamber engine was considered, and the effects of top-land crevice design and engine operating condition were examined. The computed peak cylinder pressure was found to be 6 to 8 percent lower in cases with crevice flow than without because the crevice flow reduced the effective in-cylinder charge mass by similar percentages during the main stages of combustion. However, the details of combustion were essentially unchanged by the crevice flow.
1989-09-01
Technical Paper
892089
S. Raghuma Reddy
Nomographs and an equation (shown below) have been developed for estimating the fuel vapor generation from a vehicle fuel tank as a function of fuel volatility (Read vapor pressure) and fuel tank temperature increase. where A, B, and C are the constants and are equal to 0.00817, 0.2357, and 0.0409, respectively, for gasoline at sea level; T1 and T2 are the initial and final tank temperatures, respectively, in °F; and RVP is the Reid vapor pressure of the fuel in psi. Nomographs were developed for estimating the effects of altitude, oxygenated fuels (10% ethanol blends), and tank pressure controls on tank vapor generation. The equation constants were also determined for gasolines at high altitude and for 10% ethanol blends both at sea level and high altitude. Since tank vapor generation is directly proportional to tank vapor space volume, the equation can be used for estimating vapor generation from any fuel tank.
1989-09-01
Technical Paper
892096
J. C. Kent, A. Mikulec, L. Rimal, A.A. Adamczyk, S. R. Mueller, R.A Stein, C. C. Warren
Intake-generated flow fields and subsequent combustion characteristics were studied respectively in a reciprocating piston water analog flow apparatus and in firing engines. Three 1.6L, I4, 4-valve engine cylinder heads were tested with and without one intake port blocked to generate six distinctly different inducted flow fields. Fluid velocity distributions and flow field structure (“zero mean motion”, “swirl”, and “tumble”) were determined at BDC of the induction stroke using 2-D or 3-D particle tracking velocimetry. Swirl ratios based on steady-flow data were also obtained. The burn duration for each case was determined from cylinder pressure data. The results show that burn duration decreased with increases in tumble or swirl strength. Previously observed correlations between burn duration and swirl hold if swirl is the major component of the large-scale motion.
1989-09-01
Technical Paper
892219
Chris Wolf, Barry Billman
This paper presents the results of several analytical studies performed to provide information on computed centerline operations using Microwave Landing System (MLS) Area Navigation (RNAV) equipment. These studies addressed several issues. These issues included factors effecting positional accuracy, use of elevation information, and computed signal quality. Analytical results were obtained with Monte Carlo simulation techniques which used the International Civil Aviation Organization's (ICAO) azimuth, elevation, and precision distance measuring equipment (DME/P), path following error specifications and signal degradations in Annex 10 to the International Standards, Recommended Practices and Procedures for Air Navigation Services. Data collection flights were performed at the Federal Aviation Administration (FAA) Technical Center in Atlantic City, New Jersey to validate the analytical results.
1989-09-01
Technical Paper
892217
Barry C. Scott, Tsuyoshi Goka, Jim Dargue
Two recent simulation studies examined the use of the Microwave Landing System (MLS) in the terminal area environment. In the first study, using models of the New York Terminal Areas, multiple scenarios involving Instrument Landing System (ILS) and MLS capabilities were simulated to evaluate air-traffic-control (ATC) procedures and to identify future efforts needed to ensure that ATC personnel will be able to facilitate the use of the MLS. The test disclosed several procedural issues that require further study and showed that an all-MLS environment significantly reduced controller workload. The second study examined MLS procedures for the San Francisco (SFO) Terminal Area and explored the operational feasibility of an offset azimuth radial approach to SFO runway 28R using basic mode MLS avionics.
1989-09-01
Technical Paper
892215
Ralph D. Sexton, Alan B. Jones, James H. Yates
. To develop obstacle clearance criteria and standards for MLS procedures development, the accuracy with which an aircraft can be flown along a defined approach path must be determined. Error modeling, simulator tests, and flight tests are used to determine the distributions of the flight paths about the specified approach paths. Isoprobability contours are derived from which obstacle clearance criteria are developed. The error models are also used in developing a collision risk model for use in evaluating the cumulative risk of an aircraft collision with an obstacle for specified aircraft performance and obstacle environment.
1989-09-01
Technical Paper
892210
Ric Abbott
Examples of the design concepts employed in the Beech Starship all-composite airframe are given; and the methods of material and structural cetification, including damage tolerance and adhesively bonded structures, are discussed.
1989-09-01
Technical Paper
892226
Edward V. Scicchitano, Thomas D. Yanik
This paper presents a basic guide of considerations for successful application of the integrated drive generator (IDG) to aircraft. Intrinsic to this guide is open communication and a close working relationship between the IDG supplier, buyer, and end-user. “Successful application” is defined as the interfaces which are optimized for and perform satisfactorily on the aircraft. This usually requires more than designing, developing, and qualifying the IDG or other subsystem to the design/procurement specification. The specification is typically a before-the-fact design document; it does not necessarily ensure interface with or satisfactory performance on the aircraft. Although the specification is what the supplier is contractually obligated to meet, the supplier and buyer must be willing to work together to make the IDG or other subsystem work on the aircraft, resulting in positive end-user experiences.
1989-09-01
Technical Paper
892224
Ridha Abid, Dennis A. Johnson
An investigation of the effects of turbulence models on the prediction of transonic wing flows is performed. The turbulence models used in this study are the equilibrium model of Baldwin and Lomax, and the original and modified models of Johnson and King. Comparisons with experimental data are presented which show clearly that the modified Johnson-King model works much better than the equilibrium model.
1989-09-01
Technical Paper
892238
H. Ammann, A. van der Schraaf
Abstract The paper outlines the behaviour of the Fokker 100 during its first year of commercial service with Swissair, the launch customer. Main design features are briefly discussed, together with selection criteria which prompted Swissair to become launch customer. Some aspects of crew training in relation to the introduction of glass cockpits are highlighted.
1989-09-01
Technical Paper
892237
Jacques Hege
CURRENT CONDITIONS ARE FAVORABLE FOR SUPERSONIC TRANSPORTS. STUDIES FOR A REPLACEMENT FOR THE CONCORD HAVE BEEN ON GOING FOR SOME TIME. THIS PAPER REVEALS THE PROS AND CONS OF DEVELOPING SUCH A REPLACMENT BASED ON PREVIOUS STUDIES.
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