Results for “Code Analysis” — Page 21

NASA NTRSDate not supplied

A Review of International Space Station Extravehicular Activity Micrometeoroid and Orbital Debris Risk

Nearly 300 spacewalks have been conducted over the last 25 years to support the construction and maintenance of the International Space Station (ISS). During the nearly 2,000 hours of extra-vehicular activity (EVA), crew wore extra-vehicular mobility unit (EMU) “spacesuits” to help mitigate hazards of the space environment including impacts from micrometeoroid and orbital debris (MMOD) particles. The National Aeronautics and Space Administration (NASA) conducts detailed EMU MMOD risk analyses as part of the ISS EVA review and approval process. This paper provides a general historical overview of the ISS EVA MMOD risks and the associated risk assessment process. The NASA Johnson Space Center (JSC) Hypervelocity Impact Technology (HVIT) Team produces the ISS EVA MMOD risk analyses using the Bumper MMOD risk analysis code in conjunction with detailed information about the EVA including crew member EVA work sites, crew translation paths, suit orientation, and durations. Detailed physical models of the EMU spacesuit and the ISS are included and tailored for each EVA analysis. Two types of MMOD risk are included: (1) Penetration, and (2) Catastrophic. Penetration risk is for any size leak in the EMU suit. Catastrophic risk is a subset of Penetration Risk and only includes penetrations that cause a 4mm diameter hole (or larger) in the pressure-maintaining “bladder” layer of the EMU suit. This size hole will exceed the ability of the EMU suit to compensate. The MMOD risk analyses also utilize the latest orbital debris environment and meteoroid environment models including additional transient factors to account for recent satellite break-ups and annual meteor storms. These additional factors and the associated increase in EVA MMOD risk are considered when scheduling EVAs to reduce EMU MMOD risk.

Dana M. Lear↗

NASA NTRSDate not supplied

A Review of International Space Station Extravehicular Activity Micrometeoroid and Orbital Debris Risk

Nearly 300 spacewalks have been conducted over the last 25 years to support the construction and maintenance of the International Space Station (ISS). During the nearly 2,000 hours of extra-vehicular activity (EVA), crew wore extra-vehicular mobility unit (EMU) “spacesuits” to help mitigate hazards of the space environment including impacts from micrometeoroid and orbital debris (MMOD) particles. The National Aeronautics and Space Administration (NASA) conducts detailed EMU MMOD risk analyses as part of the ISS EVA review and approval process. This paper provides a general historical overview of the ISS EVA MMOD risks and the associated risk assessment process. The NASA Johnson Space Center (JSC) Hypervelocity Impact Technology (HVIT) Team produces the ISS EVA MMOD risk analyses using the Bumper MMOD risk analysis code in conjunction with detailed information about the EVA including crew member EVA work sites, crew translation paths, suit orientation, and durations. Detailed physical models of the EMU spacesuit and the ISS are included and tailored for each EVA analysis. Two types of MMOD risk are included: (1) Penetration, and (2) Catastrophic. Penetration risk is for any size leak in the EMU suit. Catastrophic risk is a subset of Penetration Risk and only includes penetrations that cause a 4mm diameter hole (or larger) in the pressure-maintaining “bladder” layer of the EMU suit. This size hole will exceed the ability of the EMU suit to compensate. The MMOD risk analyses also utilize the latest orbital debris environment and meteoroid environment models including additional transient factors to account for recent satellite break-ups and annual meteor storms. These additional factors and the associated increase in EVA MMOD risk are considered when scheduling EVAs to reduce EMU MMOD risk.

Dana M. Lear↗

NASA NTRSDate not supplied

A Historical Overview of International Space Station Extravehicular Activity Meteoroid and Orbital Debris Risk

Nearly 300 spacewalks have been conducted over the last 25 years to help build and maintain the International Space Station (ISS). During the nearly 2,000 hours of extra-vehicular activity (EVA), crew members wear extra-vehicular mobility unit (EMU) “spacesuits” to mitigate hazards of the space environment including impacts from meteoroid and orbital debris (MMOD) particles. NASA includes detailed EMU MMOD risk analyses as part of the ISS EVA review and approval process. This paper provides a general historical overview of the ISS EVA MMOD risks and the associated risk assessment process. The NASA Johnson Space Center (JSC) Hypervelocity Impact Technology (HVIT) Team produces the ISS EVA MMOD risk analyses using the Bumper3 MMOD risk analysis code in conjunction with detailed information about the EVA including crew-member EVA work sites, crew translation paths, suit orientation, and duration. Detailed physical models of the EMU spacesuits and the ISS are included and tailored for each EVA analysis. Two types of MMOD risk are included: (1) Penetration, and (2) Catastrophic. Penetration risk is for any size leak in the EMU suit. Catastrophic risk is a subset of Penetration Risk and only includes penetrations that cause a 4mm diameter hole (or larger) in the inner “bladder” layer of the EMU suit. This size hole will exceed the ability of the EMU suit to compensate. The MMOD risk analyses also utilize the latest orbital debris environment and meteoroid environment models including additional transient factors to account for recent satellite break-ups and annual meteor storms. These additional factors and the associated increase in EVA MMOD risk are considered when scheduling an EVA to reduce EMU MMOD risk.

Dana M. Lear↗

NASA NTRS2003

Unbalance Response Prediction for Rotors on Ball Bearings Using Speed and Load Dependent Nonlinear Bearing Stiffness

Rolling-element bearing forces vary nonlinearly with bearing deflection. Thus an accurate rotordynamic analysis requires that bearing forces corresponding to the actual bearing deflection be utilized. For this work bearing forces were calculated by COBRA-AHS, a recently developed rolling-element bearing analysis code. Bearing stiffness was found to be a strong function of bearing deflection, with higher deflection producing markedly higher stiffness. Curves fitted to the bearing data for a range of speeds and loads were supplied to a flexible rotor unbalance response analysis. The rotordynamic analysis showed that vibration response varied nonlinearly with the amount of rotor imbalance. Moreover, the increase in stiffness as critical speeds were approached caused a large increase in rotor and bearing vibration amplitude over part of the speed range compared to the case of constant bearing stiffness. Regions of bistable operation were possible, in which the amplitude at a given speed was much larger during rotor acceleration than during deceleration. A moderate amount of damping will eliminate the bistable region, but this damping is not inherent in ball bearings.

Fleming, David P.↗

NASA NTRS1980

The Build System - Integration and management of large software avionic systems

The Build System comprises the software tools and procedures creating the flight memory load for the Space Shuttle Backup Flight System. The system has six functions: (1) configuration management, which insures that the memory load contains the proper modules, all clearly marked; (2) source translation, which translates the source code into a relocatable machine code; (3) module integration, which combines and assigns memory locations to all the object modules produced in source translation; (4) static code analysis, which verifies the integration process; (5) deliverables generation, which yields release documentation and deliverable items; and (6) release maintenance, which controls all system patches subsequent to release. Further developments will include more automation in the producing of patches from source-code updates and system requirements for tracking.

Mayer, J. T. B.↗

NASA NTRSDate not supplied

Predicted Performance Effects of Blade Elasticity on Testing of Rotors for Mars

The Rotor Optimization for the Advancement of Mars Exploration project (ROAMX) has designed and manufactured a set of rotor blades optimized for hover on Mars. These blades will soon be tested for hover performance in the NASA Ames Research Center Planetary Aeolian Laboratory, a large vacuum chamber capable of rotor testing at reduced pressures. To match the tip Mach numbers during this testing with the tip Mach numbers that would be experienced in the Martian atmosphere, the rotor will be spun faster in the vacuum chamber than it would be spun on Mars. While this accomplishes the goal of simulating the tip Mach numbers of Mars operations, the elevated RPM may have undesired consequences for performance, due to elastic deflections of the blades. The purpose of this paper is to use CAMRAD II, a rotorcraft comprehensive analysis code, to predict the effect on performance of blade elasticity at elevated RPM in the vacuum chamber environment. Results are presented for different thrust conditions and different rotor speeds, and comparisons are made between rigid and elastic blade predictions. Overall, the CAMRAD II analysis suggests that blade elasticity does influence rotor performance in the operating conditions of interest, although the effect is moderate enough to conclude that the PAL testing will be a good simulation of Mars operation.

Blade elasticity↗

NASA NTRS1980

PASCO: Structural panel analysis and sizing code, capability and analytical foundations

A computer code denoted PASCO which can be used for analyzing and sizing uniaxially-stiffened composite panels is described. Buckling and vibration analyses are carried out with a linked-plate analysis computer code denoted VIPASA, which is incorporated in PASCO. Sizing is based on nonlinear mathematical programming techniques and employs a computer code denoted CONMIN, also incorporated in PASCO. Design requirements considered are initial buckling, material strength, stiffness, and vibration frequency. The capability of the PASCO computer code and the approach used in the structural analysis and sizing are described.

Stroud, W. J.↗

NASA NTRS2001

A Program To Detect and Characterize Extra-Solar Giant Planets

This grant report highlights activity in the following areas: (1) Improvement in Precise Radial Velocity (PRV) analysis code; (2) Reanalysis of previous data; (3) Improvements to the AFOE (Advanced Fiber Optic Echelle) spectrograph; (4) Development of PRV capabilities for the Hectochelle; (5) Extra-solar planet studies; (6) Longer-term plans for the AFOE; (7) Completion and publication of the analysis of the transiting gas-giant planet HD 209458b.

Noyes, Robert W.↗

NASA NTRS2005

Preliminary Design of a Manned Nuclear Electric Propulsion Vehicle Using Genetic Algorithms

Nuclear electric propulsion (NEP) vehicles will be needed for future manned missions to Mars and beyond. Candidate designs must be identified for further detailed design from a large array of possibilities. Genetic algorithms have proven their utility in conceptual design studies by effectively searching a large design space to pinpoint unique optimal designs. This research combined analysis codes for NEP subsystems with a genetic algorithm. The use of penalty functions with scaling ratios was investigated to increase computational efficiency. Also, the selection of design variables for optimization was considered to reduce computation time without losing beneficial design search space. Finally, trend analysis of a reference mission to the asteroids yielded a group of candidate designs for further analysis.

Irwin, Ryan W.↗

NASA NTRS1982

A full potential inverse method based on a density linearization scheme for wing design

A mixed analysis inverse procedure based on the full potential equation in conservation form was developed to recontour a given base wing to produce density linearization scheme in applying the pressure boundary condition in terms of the velocity potential. The FL030 finite volume analysis code was modified to include the inverse option. The new surface shape information, associated with the modified pressure boundary condition, is calculated at a constant span station based on a mass flux integration. The inverse method is shown to recover the original shape when the analysis pressure is not altered. Inverse calculations for weakening of a strong shock system and for a laminar flow control (LFC) pressure distribution are presented. Two methods for a trailing edge closure model are proposed for further study.

Shankar, V.↗

NASA NTRS1996

Stress and Damage in Polymer Matrix Composite Materials Due to Material Degradation at High Temperatures

This report describes analytical methods for calculating stresses and damage caused by degradation of the matrix constituent in polymer matrix composite materials. Laminate geometry, material properties, and matrix degradation states are specified as functions of position and time. Matrix shrinkage and property changes are modeled as functions of the degradation states. The model is incorporated into an existing composite mechanics computer code. Stresses, strains, and deformations at the laminate, ply, and micro levels are calculated, and from these calculations it is determined if there is failure of any kind. The rationale for the model (based on published experimental work) is presented, its integration into the laminate analysis code is outlined, and example results are given, with comparisons to existing material and structural data. The mechanisms behind the changes in properties and in surface cracking during long-term aging of polyimide matrix composites are clarified. High-temperature-material test methods are also evaluated.

McManus, Hugh L.↗

NASA NTRS1980

Shockless airfoils for wings, compressors, and turbines

The major aspects of a code for the design of shockless airfoils in two-dimensional transonic flow are reviewed. The code is based on a method of analytic continuation into the domain of two complex characteristic variables, which makes it possible to associate a shockless airfoil with a given pressure distribution. This procedure is compared with another more direct method based on a two-dimensional analysis code that has had wide acceptance by the aircraft industry.

Garabedian, P. R.↗

NASA NTRS2006

A Three-Dimensional Unsteady CFD Model of Compressor Stability

A three-dimensional unsteady CFD code called CSTALL has been developed and used to investigate compressor stability. The code solved the Euler equations through the entire annulus and all blade rows. Blade row turning, losses, and deviation were modeled using body force terms which required input data at stations between blade rows. The input data was calculated using a separate Navier-Stokes turbomachinery analysis code run at one operating point near stall, and was scaled to other operating points using overall characteristic maps. No information about the stalled characteristic was used. CSTALL was run in a 2-D throughflow mode for very fast calculations of operating maps and estimation of stall points. Calculated pressure ratio characteristics for NASA stage 35 agreed well with experimental data, and results with inlet radial distortion showed the expected loss of range. CSTALL was also run in a 3-D mode to investigate inlet circumferential distortion. Calculated operating maps for stage 35 with 120 degree distortion screens showed a loss in range and pressure rise. Unsteady calculations showed rotating stall with two part-span stall cells. The paper describes the body force formulation in detail, examines the computed results, and concludes with observations about the code.

Chima, Rodrick V.↗

NASA NTRSDate not supplied

High-Fidelity Simulations of a Quadrotor Vehicle for Urban Air Mobility

High-fidelity computational fluid dynamics simulations have been carried out to analyze NASA’s quadrotor air taxi concept for urban air mobility. High-order accurate schemes, dual-time stepping, and the delayed detached-eddy simulation model have been employed. The flow solver has been loosely coupled with the rotorcraft comprehensive analysis code. The vehicle simulated is a six-passenger quadrotor for air taxi operations. The quadrotor has been simulated in hover and cruise, with flight conditions representative of an air taxi mission. Initially, the quadcopter vehicle is analyzed using low-fidelity tools. Then, a complete analysis using high-fidelity simulations of the quadcopter is performed in conjunction with collective pitch control. Airloads, wake geometry, and performance are studied and compared. A comparison between isolated rotors and complete vehicle simulations is presented. NASA’s quadrotor is one of NASA’s concept vehicles designed in support of aircraft development for vertical take-off and landing air taxi operations.

ARMD↗

NASA NTRS2003

Forward-Swept Fan Flutter Calculated Using TURBO Code

Flutter, a self-excited dynamic instability arising because of fluid structure interaction, can be a significant design problem for rotor blades in gas turbines. Blade shapes influenced by noise-reduction requirements increase the likelihood of flutter in modern blade designs. Validated numerical methods provide designers an invaluable tool to calculate and avoid the flutter instability during the design phase. Toward this objective, a flutter analysis code, TURBO, was developed and validated by researchers from the NASA Glenn Research Center and other researchers working under grants and contracts with Glenn. The TURBO code, which is based on unsteady three-dimensional Reynolds-averaged Navier-Stokes equations was used to calculate the observed flutter of a forward-swept fan. The forward-swept experimental fan, designed to reduce noise, showed flutter at part-speed conditions during wind tunnel tests.

Srivastava, Rakesh↗

NASA NTRS2000

Construction and Utilization of a Beowulf Computing Cluster: A User's Perspective

Lockheed Martin Space Operations - Stennis Programs (LMSO) at the John C Stennis Space Center (NASA/SSC) has designed and built a Beowulf computer cluster which is owned by NASA/SSC and operated by LMSO. The design and construction of the cluster are detailed in this paper. The cluster is currently used for Computational Fluid Dynamics (CFD) simulations. The CFD codes in use and their applications are discussed. Examples of some of the work are also presented. Performance benchmark studies have been conducted for the CFD codes being run on the cluster. The results of two of the studies are presented and discussed. The cluster is not currently being utilized to its full potential; therefore, plans are underway to add more capabilities. These include the addition of structural, thermal, fluid, and acoustic Finite Element Analysis codes as well as real-time data acquisition and processing during test operations at NASA/SSC. These plans are discussed as well.

Woods, Judy L.↗

NASA NTRS1985

A computer analysis program for interfacing thermal and structural codes

A software package has been developed to transfer three-dimensional transient thermal information accurately, efficiently, and automatically from a heat transfer analysis code to a structural analysis code. The code is called three-dimensional TRansfer ANalysis Code to Interface Thermal and Structural codes, or 3D TRANCITS. TRANCITS has the capability to couple finite difference and finite element heat transfer analysis codes to linear and nonlinear finite element structural analysis codes. TRANCITS currently supports the output of SINDA and MARC heat transfer codes directly. It will also format the thermal data output directly so that it is compatible with the input requirements of the NASTRAN and MARC structural analysis codes. Other thermal and structural codes can be interfaced using the transfer module with the neutral heat transfer input file and the neutral temperature output file. The transfer module can handle different elemental mesh densities for the heat transfer analysis and the structural analysis.

Thompson, R. L.↗

NASA NTRS1985

A computer analysis program for interfacing thermal and structural codes

A software package has been developed to transfer three-dimensional transient thermal information accurately, efficiently, and automatically from a heat transfer analysis code to a structural analysis code. The code is called three-dimensional TRansfer ANalysis Code to Interface Thermal and Structural codes, or 3D TRANCITS. TRANCITS has the capability to couple finite difference and finite element heat transfer analysis codes to linear and nonlinear finite element structural analysis codes. TRANCITS currently supports the output of SINDA and MARC heat transfer codes directly. It will also format the thermal data output directly so that it is compatible with the input requirements of the NASTRAN and MARC structural analysis codes. Other thermal and structural codes can be interfaced using the transfer module with the neutral heat transfer input file and the neutral temperature output file. The transfer module can handle different elemental mesh densities for the heat transfer analysis and the structural analysis.

Thompson, R. L.↗