SEARCH · Search NASA

Results for “Unit Testing”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15

All sources NASA NTRS DOE OSTI

NASA NTRS1999

Design and Performance of the HESSI Cryostat

The High Energy Solar Spectroscopic Imager (HESSI) spacecraft, to be launched in July 2000, will be used to observe the Sun with the finest angular and energy resolutions ever achieved from a few keV to hundreds of keV. The spacecraft will use an array of nine germanium (Ge) detectors, each 7.1 cm in diameter and 8.5 cm long, operating at 75K. The detectors are mounted in a cryostat on a common cold plate, and cooled by a small Stirling-cycle cryocooler. This paper describes the design of the cryostat, special accommodations for the Ge detectors, interfaces with the cryocooler, and thermal performance of the engineering test unit.

Boyle, R.↗

NASA NTRS1998

Vacuum Plasma Spray (VPS) Forming of Solar Thermal Propulsion Components Using Refractory Metals

The Thermal Spray Laboratory at NASA's Marshall Space Flight Center has developed and demonstrated a fabrication technique using Vacuum Plasma Spray (VPS) to form structural components from a tungsten/rhenium alloy. The components were assembled into an absorption cavity for a fully-functioning, ground test unit of a solar thermal propulsion engine. The VPS process deposits refractory metal onto a graphite mandrel of the desired shape. The mandrel acts as a male mold, forming the required contour and dimensions of the inside surface of the deposit. Tungsten and tungsten/25% rhenium were used in the development and production of several absorber cavity components. These materials were selected for their high temperature (less than 2500 C) strength. Each absorber cavity comprises 3 coaxial shells with two, double-helical flow passages through which the propellant gas flows. This paper describes the processing techniques, design considerations, and process development associated with forming these engine components.

Zimmerman, Frank↗

NASA NTRS1999

Two-Phase Technology at NASA/Johnson Space Center

Since the baseline International Space Station (ISS) External Active Thermal Control System (EATCS) was changed from a two-phase mechanically pumped system to a single phase cascade system in the fall of 1993, two-phase EATCS research has continued at a low level at JSC. One of-the lessons of the ISS EATCS selection was that two-phase thermal control systems must have significantly lower power than comparable single phase systems to overcome their larger radiator area, larger line and fluid mass, and perceived higher technical risk. Therefore, research at JSC has concentrated on low power mechanically pumped two-phase EATCSs. In the presentation, the results of a study investigating the trade of single and two-phase mechanically pumped EATCSs for space vehicles will be summarized. The low power two-phase mechanically pumped EATCS system under development at JSC will be described in detail and the current design status of the subscale test unit will be reviewed. Also, performance predictions for a full size EATCS will be presented. In addition to the discussion of two-phase mechanically pumped EATCS development at JSC, two-phase technologies under development for biological water processing will be discussed. These biological water processor technologies are being prepared for a 2001 flight experiment and subsequent usage on the TransHab module on the International Space Station.

Ungar, Eugene K.↗

NASA NTRS2001

MC-1 LOX Pump Rotating Cavitation: Issue and Investigation

Leading edge tip deformation was noted on the LOX inducer from the component test unit at disassembly. The damage was in a location similar to a previous Fastrac water flow inducer failure. A team was formed to investigate the anomaly.

VanHooser, Katherine↗

NASA NTRS2002

Silicon Lightweight Mirrors (SLMS) for Ultraviolet and Extreme Ultraviolet Imaging Mirrors

Subtopic 01-S1.06 requires mirrors with a diameter of 0.5-2.4 meters, areal density less than 20 kg/sq m, a figure specification of 0.02-0.005 waves root mean square (rms) at 633 nanometers, a surface roughness 0.5-1 nanometers rms, and a midfrequency error of 1.0-2.5 nanometers rms for use in the infrared (IR) to extreme ultra violet (EUV) waveband. Schafer's Phase II objective is to use Silicon Lightweight Mirrors (SLMS), a novel, all-silicon, foam-core, lightweight mirror technology, to build three imaging mirrors for the Next Generation Space Telescope Near Infrared Camera (NIRCam) Engineering Test Unit: M0 (a flat), M2 (a concave sphere) and M3R (an oblate spheroid). The surface figure error specification for the NIRCam imaging mirrors is 8 nanometers rms (0.013 waves rms at 633 nanometers), equivalent to that required for ultraviolet (UV) and EUV mirrors, and this figure must be maintained at the 35 K operational temperature of NGST. The surface roughness required is 30 A rms since NIRCam operates in the visible to infrared (VIS/IR) (0.65-5 microns). We will produce mounts for mirrors M2 and M3R using the complementary thermally matched C/SiC material demonstrated by Schafer under another NASA SBIR, NAS8-98137.

Goodman, W. A.↗

NASA NTRS1995

Stress Prediction System

NASA wanted to know how astronauts' bodies would react under various gravitational pulls and space suit weights. Under contract to NASA, the University of Michigan's Center for Ergonomics developed a model capable of predicting what type of stress and what degree of load a body could stand. The algorithm generated was commercialized with the ISTU (Isometric Strength Testing Unit) Functional Capacity Evaluation System, which simulates tasks such as lifting a heavy box or pushing a cart and evaluates the exertion expended. It also identifies the muscle group that limits the subject's performance. It is an effective tool of personnel evaluation, selection and job redesign.

Source record↗

NASA NTRS2005

Multi-level Simulation of a Real Time Vibration Monitoring System Component

This paper describes the development of a custom built Digital Signal Processing (DSP) printed circuit board designed to implement the Advanced Real Time Vibration Monitoring Subsystem proposed by Marshall Space Flight Center (MSFC) Transportation Directorate in 2000 for the Space Shuttle Main Engine Advanced Health Management System (AHMS). This Real Time Vibration Monitoring System (RTVMS) is being developed for ground use as part of the AHMS Health Management Computer-Integrated Rack Assembly (HMC-IRA). The HMC-IRA RTVMS design contains five DSPs which are highly interconnected through individual communication ports, shared memory, and a unique communication router that allows all the DSPs to receive digitized data fiom two multi-channel analog boards simultaneously. This paper will briefly cover the overall board design but will focus primarily on the state-of-the-art simulation environment within which this board was developed. This 16-layer board with over 1800 components and an additional mezzanine card has been an extremely challenging design. Utilization of a Mentor Graphics simulation environment provided the unique board and system level simulation capability to ascertain any timing or functional concerns before production. By combining VHDL, Synopsys Software and Hardware Models, and the Mentor Design Capture Environment, multiple simulations were developed to verify the RTVMS design. This multi-level simulation allowed the designers to achieve complete operability without error the first time the RTVMS printed circuit board was powered. The HMC-IRA design has completed all engineering and deliverable unit testing. P

Robertson, Bryan A.↗

NASA NTRS2007

Detector Arrays for the James Webb Space Telescope Near-Infrared Spectrograph

The James Webb Space Telescope's (JWST) Near Infrared Spectrograph (NIRSpec) incorporates two 5 micron cutoff (lambda(sub co) = 5 microns) 2048x2048 pixel Teledyne HgCdTe HAWAII-2RG sensor chip assemblies. These detector arrays, and the two Teledyne SIDECAR application specific integrated circuits that control them, are operated in space at T approx. 37 K. In this article, we provide a brief introduction to NIRSpec, its detector subsystem (DS), detector readout in the space radiation environment, and present a snapshot of the developmental status of the NIRSpec DS as integration and testing of the engineering test unit begins.

Rauscher, Bernard J.↗

NASA NTRS1949

Performance of Axial-Flow Supersonic Compressor on XJ-55-FF-1 Turbojet Engine. I - Preliminary Performance of Compressor: Preliminary Performance of Compressor - 1

An investigation was conducted to determine the performance characteristics of the axial-flow supersonic compressor of the XJ-55-FF-1 turbo Jet engine. The test unit consisted of a row of inlet guide vanes and a supersonic rotor; the stator vanes after the rotor were omitted. The maximum pressure ratio produced in the single stage was 2.28 at an equivalent tip speed or 1814 feet per second with an adiabatic efficiency of approximately 0.61, equivalent weight flow of 13.4 pounds per second. The maximum efficiency of 0.79 was obtained at an equivalent tip speed of 801 feet per second.

Hartmann, Melvin J.↗

NASA NTRS2004

Software for Analyzing Laminar-to-Turbulent Flow Transitions

Software assurance is the planned and systematic set of activities that ensures that software processes and products conform to requirements, standards, and procedures. Examples of such activities are the following: code inspections, unit tests, design reviews, performance analyses, construction of traceability matrices, etc. In practice, software development projects have only limited resources (e.g., schedule, budget, and availability of personnel) to cover the entire development effort, of which assurance is but a part. Projects must therefore select judiciously from among the possible assurance activities. At its heart, this can be viewed as an optimization problem; namely, to determine the allocation of limited resources (time, money, and personnel) to minimize risk or, alternatively, to minimize the resources needed to reduce risk to an acceptable level. The end result of the work reported here is a means to optimize quality-assurance processes used in developing software. This is achieved by combining two prior programs in an innovative manner

Chang, Chau-Lyan↗

NASA NTRS2004

Software for Optimizing Quality Assurance of Other Software

Feather, Martin↗

NASA NTRS2012

Gravity and Extreme Magnetism SMEX

The Gravity and Extreme Magnetism SMEX mission will be the first mission to catalogue the X-ray polarisation of many astrophysical objects including black-holes and pulsars. This first of its kind mission is enabled by the novel use of a time projection chamber as an X-ray polarimeter. The detector has been developed over the last 5 years, with the current effort charged toward a demonstration of it's technical readiness to be at level 6 prior to the preliminary design review. This talk will describe the design GEMS polarimeter and the results to date from the engineering test unit.

Source record↗

NASA NTRS2013

Science Opportunity Analyzer (SOA) Version 8

SOA allows scientists to plan spacecraft observations. It facilitates the identification of geometrically interesting times in a spacecraft s orbit that a user can use to plan observations or instrument-driven spacecraft maneuvers. These observations can then be visualized multiple ways in both two- and three-dimensional views. When observations have been optimized within a spacecraft's flight rules, the resulting plans can be output for use by other JPL uplink tools. Now in its eighth major version, SOA improves on these capabilities in a modern and integrated fashion. SOA consists of five major functions: Opportunity Search, Visualization, Observation Design, Constraint Checking, and Data Output. Opportunity Search is a GUI-driven interface to existing search engines that can be used to identify times when a spacecraft is in a specific geometrical relationship with other bodies in the solar system. This function can be used for advanced mission planning as well as for making last-minute adjustments to mission sequences in response to trajectory modifications. Visualization is a key aspect of SOA. The user can view observation opportunities in either a 3D representation or as a 2D map projection. Observation Design allows the user to orient the spacecraft and visualize the projection of the instrument field of view for that orientation using the same views as Opportunity Search. Constraint Checking is provided to validate various geometrical and physical aspects of an observation design. The user has the ability to easily create custom rules or to use official project-generated flight rules. This capability may also allow scientists to easily assess the cost to science if flight rule changes occur. Data Output allows the user to compute ancillary data related to an observation or to a given position of the spacecraft along its trajectory. The data can be saved as a tab-delimited text file or viewed as a graph. SOA combines science planning functionality unique to both JPL and the sponsoring spacecraft. SOA is able to ingest JPL SPICE Kernels that are used to drive the tool and its computations. A Percy search engine is then included that identifies interesting time periods for the user to build observations. When observations are then built, flight-like orientation algorithms replicate spacecraft dynamics to closely simulate the flight spacecraft s dynamics. SOA v8 represents large steps forward from SOA v7 in terms of quality, reliability, maintainability, efficiency, and user experience. A tailored agile development environment has been built around SOA that provides automated unit testing, continuous build and integration, a consolidated Web-based code and documentation storage environment, modern Java enhancements, and a focus on usability

Witoff, Robert J.↗

NASA NTRS2011

Shooting the Moon

This story is about an unlikely NASA mission to the Moon. It was unlikely because it was started with far too little time and too-little money to complete. It was unlikely because it was able to take chances to accept risk of failure. It was unlikely because it was searching for the unthinkable: water-ice on the moon... Figure 1-1: LCROSS Mission. The mission of the Lunar CRater Observation and Sensing Satellite (LCROSS) was to investigate the possibility of water ice in craters on the Moon s poles. This is certainly an interesting scientific topic in itself, but I intend to focus on the compelling experience of managing the LCROSS Project in the context of this storied Agency. Perhaps most interesting are the implications this story has for managing any development effort, lunar or not, and working a balance to achieve success. NASA is by design a risk-taking agency within the US Government. It could be argued that NASA s purpose in the aerospace community is to take on the really big challenges that either the corporate world can t afford, are not yet profitable endeavors, or are just too risky for private corporations to entertain. However, expectations of the Agency have evolved. A combination of grim human tragedies and some very public cost and schedule overruns have challenged the public s and Congress s tolerance for risk-taking within the Agency. NASA, which is supposed to be in the business of taking risks to do bold, difficult things, has become less and less able to do so within its cost framework. Yet effectively replacing prudent risk management with attempts to "risk-eliminate" is completely unaffordable. So where does risk-taking fit within the Agency, or within private/corporate organizations for that matter? Where astronauts play there is clearly concern about risk. When an organization puts humans in harm s way, it is understandably going to take extra effort to assure nobody gets hurt. Doing so, of course, costs money - a lot of money to pay for labor and hardware which is attempting to assure nothing will go wrong. Sophisticated designs, with doubly- or triply-redundant systems, extensive testing to verify those systems, and numerous engineering test units built to learn and evolve a hardware design, all drive the cost and time required to implement. Human spaceflight is an expensive business because of the exceptional system complexity and levels of assurance required for human space travel. What about missions that do not involve human spaceflight? What about missions whose potential failure will not take a human life, whose costs are small and whose urgency and importance are limited by design? A portfolio consisting of this type of mission can be designed to be risk tolerant, not requiring large expenditures to guarantee against failure. With the money saved, the number of missions that can be executed within the portfolio grows, or the total cost of the portfolio can be reduced. The NASA LCROSS mission is a pathfinder example of a low-cost, quick turn-around mission which struck a balance on mission risk, while accomplishing big objectives, like defining how we understand the Moon.

Andrews, Daniel R.↗

NASA NTRS2013

Develop a Model Component

During my internship at NASA, I was a model developer for Ground Support Equipment (GSE). The purpose of a model developer is to develop and unit test model component libraries (fluid, electrical, gas, etc.). The models are designed to simulate software for GSE (Ground Special Power, Crew Access Arm, Cryo, Fire and Leak Detection System, Environmental Control System (ECS), etc. ~.) before they are implemented into hardware. These models support verifying local control and remote software for End-Item Software Under Test (SUT). The model simulates the physical behavior (function, state, limits and 110) of each end-item and it's dependencies as defined in the Subsystem Interface Table, Software Requirements & Design Specification (SRDS), Ground Integrated Schematic (GIS), and System Mechanical Schematic.(SMS). The software of each specific model component is simulated through MATLAB's Simulink program. The intensiv~ model development life cycle is a.s follows: Identify source documents; identify model scope; update schedule; preliminary design review; develop model requirements; update model.. scope; update schedule; detailed design review; create/modify library component; implement library components reference; implement subsystem components; develop a test script; run the test script; develop users guide; send model out for peer review; the model is sent out for verific~tionlvalidation; if there is empirical data, a validation data package is generated; if there is not empirical data, a verification package is generated; the test results are then reviewed; and finally, the user. requests accreditation, and a statement of accreditation is prepared. Once each component model is reviewed and approved, they are intertwined together into one integrated model. This integrated model is then tested itself, through a test script and autotest, so that it can be concluded that all models work conjointly, for a single purpose. The component I was assigned, specifically, was a fluid component, a discrete pressure switch. The switch takes a fluid pressure input, and if the pressure is greater than a designated cutoff pressure, the switch would stop fluid flow.

Ensey, Tyler S.↗

NASA NTRS2015

Heatshield for Extreme Entry Environment Technology (HEEET) Enabling Missions Beyond Heritage Carbon Phenolic

This poster provides an overview of the requirements, design, development and testing of the 3D Woven TPS being developed under NASAs Heatshield for Extreme Entry Environment Technology (HEEET) project. Under this current program, NASA is working to develop a Thermal Protection System (TPS) capable of surviving entry into Venus or Saturn. A primary goal of the project is to build and test an Engineering Test Unit (ETU) to establish a Technical Readiness Level (TRL) of 6 for this technology by 2017.

Venus↗

NASA NTRS2016

ISS Double-Gimbaled CMG Subsystem Simulation Using the Agile Development Method

This paper presents an evolutionary approach in simulating a cluster of 4 Control Moment Gyros (CMG) on the International Space Station (ISS) using a common sense approach (the agile development method) for concurrent mathematical modeling and simulation of the CMG subsystem. This simulation is part of Training systems for the 21st Century simulator which will provide training for crew members, instructors, and flight controllers. The basic idea of how the CMGs on the space station are used for its non-propulsive attitude control is briefly explained to set up the context for simulating a CMG subsystem. Next different reference frames and the detailed equations of motion (EOM) for multiple double-gimbal variable-speed control moment gyroscopes (DGVs) are presented. Fixing some of the terms in the EOM becomes the special case EOM for ISS's double-gimbaled fixed speed CMGs. CMG simulation development using the agile development method is presented in which customer's requirements and solutions evolve through iterative analysis, design, coding, unit testing and acceptance testing. At the end of the iteration a set of features implemented in that iteration are demonstrated to the flight controllers thus creating a short feedback loop and helping in creating adaptive development cycles. The unified modeling language (UML) tool is used in illustrating the user stories, class designs and sequence diagrams. This incremental development approach of mathematical modeling and simulating the CMG subsystem involved the development team and the customer early on, thus improving the quality of the working CMG system in each iteration and helping the team to accurately predict the cost, schedule and delivery of the software.

Inampudi, Ravi↗

NASA NTRS2015

Heatshield for Extreme Entry Environment Technology (HEEET) - Enabling Missions Beyond Heritage Carbon Phenolic

This poster provides an overview of the requirements, design, development and testing of the 3D Woven TPS being developed under NASA's Heatshield for Extreme Entry Environment Technology (HEEET) project. Under this current program, NASA is working to develop a Thermal Protection System (TPS) capable of surviving entry into Venus or Saturn. A primary goal of the project is to build and test an Engineering Test Unit (ETU) to establish a Technical Readiness Level (TRL) of 6 for this technology by 2017.

Carbon Phenolic↗