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At least 1,225 records · Page 68
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Origin and development of ablator for Space Shuttle external tank

The Space Shuttle External Tank (ET) represents the largest element of the Space Shuttle transportation system. The ET is the fuel tank which contains cryogenic propellants, including liquid oxygen and liquid hydrogen. The task of providing a suitable Thermal Protection System (TPS) which is mass producible for the ET represented a challenge for the aerospace industry. The difficulties were compounded by stringent insulation and ablation requirements for the materials to maintain their integrity over a wide range of operating temperatures during prelaunch and ascent. Attention is given to the configuration of the Space Shuttle system, the configuration of the external tank, the initial ET TPS concept, TPS materials and processes concepts, design rationale, TPS materials structural considerations, material and processes development, development tests, material/process verification, and flight results.

Ronquillo, L.↗
NASA NTRS1996

A Normal Incidence X-ray Telescope (NIXT) Sounding Rocket Payload

During the past year the changeover from the normal incidence X ray telescope (NIXT) program to the new TXI sounding rocket program was completed. The NIXT effort, aimed at evaluating the viability of the remaining portions of the NIXT hardware and design has been finished and the portions of the NIXT which are viable and flightworthy, such as filters, mirror mounting hardware, electronic and telemetry interface systems, are now part of the new rocket payload. The backup NIXT multilayer-coated X ray telescope and its mounting hardware have been completely fabricated and are being stored for possible future use in the TXI rocket. The h-alpha camera design is being utilized in the TXI program for real-time pointing verification and control via telemetry. Two papers, summarizing scientific results from the NIXT rocket program were published this year.

Golub, Leon↗
NASA NTRS1998

The Global Coronal Structure Investigation

During the past year we have completed the changeover from the NIXT program to the new TXI sounding rocket program. The NIXT effort, aimed at evaluating the viability of the remaining portions of the NIXT hardware and design, has been finished and the portions of the NIXT which are viable and flightworthy, such as filters, mirror mounting hardware, electronics and telemetry interface systems, are now part of the new rocket payload. The backup NIXT multilayer-coated x-ray telescope and its mounting hardware have been completely fabricated and are being stored for possible future use in the TXI rocket. The H-alpha camera design is being utilized in the TXI program for real-time pointing verification and control via telemetry. A new H-alpha camera has been built, with a high-resolution RS170 CCD camera output. Two papers, summarizing scientific results from the NIXT rocket program, have been written and published this year: 1. "The Solar X-ray Corona," by L. Golub, Astrophysics and Space Science, 237, 33 (1996). 2. "Difficulties in Observing Coronal Structure," Keynote Paper, Proceedings STEPWG1 Workshop on Measurements and Analyses of the Solar 3D Magnetic Field, Solar Physics, 174, 99 (1997).

Golub, Leon↗
NASA NTRS2008

Experimental Evaluation of a Planning Language Suitable for Formal Verification

The marriage of model checking and planning faces two seemingly diverging alternatives: the need for a planning language expressive enough to capture the complexity of real-life applications, as opposed to a language simple, yet robust enough to be amenable to exhaustive verification and validation techniques. In an attempt to reconcile these differences, we have designed an abstract plan description language, ANMLite, inspired from the Action Notation Modeling Language (ANML) [17]. We present the basic concepts of the ANMLite language as well as an automatic translator from ANMLite to the model checker SAL (Symbolic Analysis Laboratory) [7]. We discuss various aspects of specifying a plan in terms of constraints and explore the implications of choosing a robust logic behind the specification of constraints, rather than simply propose a new planning language. Additionally, we provide an initial assessment of the efficiency of model checking to search for solutions of planning problems. To this end, we design a basic test benchmark and study the scalability of the generated SAL models in terms of plan complexity.

Butler, Rick W.↗
NASA NTRS2012

Color Choice is Everything - Impacts Color makes to the Lighting Environment

When contracts are let out to design multiple systems in a vehicle, it is a challenge to maintain integration between system leads. Designers on niche systems, like lighting and control panel design, often get caught up in the challenge of designing the light source or visual interface and fail to include time in their schedule to work with system architects on how their lighting system will be integrated. Additionally, behavioral scientists, industrial designers, and materials engineers get caught up with the materials and look of the system, but often fail to consider how the selection of their materials could affect the certification or performance of electronic devices like lighting systems. Additionally, computer modeling of the system architecture often assumes a perfect environment without the clutter of actual human use (dirt, stowage, crowding). As a result, lighting systems, and backlit displays run the risk of being overdesigned or under designed. Engineers making the assumption that because they have no input or there is no requirement on work surface reflectance, make the assumption that they can t count on good material choices and thus may install more lighting than is necessary. While having more lights may seem better, for a vehicle that is trying to conserve power, more lights may not be a good option. On the other hand, designers who made the opposite assumption and designed a lighting system that only produced just enough light, often wind up with a system that did conserve power, but didn t produce enough light. These situations are exasperated when the system starts to be used and the models are not perfect anymore. The lack of coordination and iterative design not only can impact lighting levels within an environment, but also can affect color perception. This is because, if materials do not represent a gradation of white or black, the material unevenly absorbs and reflects light at different wavelengths of the visual spectrum. The lighting designer may have built a light that meets light spectra requirements, but the eventual light reaching the human user may not be the spectra of light architects intended, if materials near the light source change the spectrum just by how much color is absorbed or reflected. With the recent findings concerning Circadian rhythm, where the spectra of light is extremely important for addressing crew sleep and wake cycles, system architects should pay considerable attention on the impact material choices have in changing the light spectrum in an environment. This presentation will show examples of how material choices impact the resulting illuminance, color spectrum, and power usage of an illuminated space. Its goal is to encourage system designers and planners to use more care in development of requirements and the verification of systems intended for the human visual interface.

Clark, Toni A.↗
NASA NTRS2008

Performance Testing of Yardney Li-Ion Cells and Batteries in Support of JPL's 2009 Mars Science Laboratory Mission

In 2009, JPL is planning to launch an unmanned rover mission to the planet Mars. This mission, referred to as the Mars Science Laboratory (MSL), will involve the use of a rover that is much larger than the previously developed Spirit and Opportunity Rovers for the 2003 Mars Exploration Rover (MER) mission, that are currently still in operation on the surface of the planet after more than three years. Part of the reason that the MER rovers have operated so successfully, far exceeding the required mission duration of 90 sols, is that they possess robust Li-ion batteries, manufactured by Yardney Technical Products, which have demonstrated excellent life characteristics. Given the excellent performance characteristics displayed, similar lithium-ion batteries have been projected to successfully meet the mission requirements of the up-coming MSL mission. Although comparable in many facets, such as being required to operate over a wide temperature range (-20 to 40 C), the MSL mission has more demanding performance requirements compared to the MER mission, including much longer mission duration (approx. 687 sols vs. 90 sols), higher power capability, and the need to withstand higher temperature excursions. In addition, due to the larger rover size, the MSL mission necessitates the use of a much larger battery to meet the energy, life, and power requirements. In order to determine the viability of meeting these requirements, a number of performance verification tests were performed on 10 Ah Yardney lithium-ion cells (MER design) under MSL-relevant conditions, including mission surface operation simulation testing. In addition, the performance of on-going ground life testing of 10 Ah MER cells and 8-cell batteries will be discussed in the context of capacity loss and impedance growth predictions.

MSL Rover↗
NASA NTRS2021

Vertiport Automation Software Architecture and Requirements

The purpose of Vertiport Automation Software Architecture and Requirements was developed to mature the Vertiport Automation System (VAS) described in the High-Density Automated Vertiport ConOps, into a set of artifacts that enable the development of a VAS prototype. The scope of document was to develop: (1) A VAS Software Architecture diagram that logically organizes VAS functionality into specific software components; (2) VAS Software Trade Study identifying existing commercial products and NASA research that can be used in part or with modifications to fulfill VAS functionality. (3) A set of VAS Functional Requirements which decompose the VAS concept into software functionality, including any interfaces and data flows needed; (4) A set of VAS Test Approaches describing a methodology for verification of the VAS Functional Requirements; and (5) An application user experience (UX) design study describing the general features needed in a VAS user interface.

Advanced Air Mobility↗
NASA NTRS1955

Aerodynamic Design of Axial-Flow Compressors. VII - Blade-Element Flow in Annular Cascades

Annular blade-element data obtained primarily from single-stage compressor installations are correlated over a range of inlet Mach numbers and cascade geometry. The correlation curves are presented in such a manner that they are related directly to the low-speed two-dimensional-cascade data of part VI of this series. Thus, the data serve as both an extension and a verification of the two-dimensional-cascade data. In addition, the correlation results are applied to compressor design.

Robbins, William H.↗
NASA NTRS2004

Spitzer Space Telescope in-orbit checkout and science verification operations

Spitzer Space Telescope, the fourth and final of NASA's great observatories, and the first mission in NASA's Origins Program was launched 25 August 2003 into an Earth-trailing solar orbit. The observatory was designed to probe and explore the universe in the infrared. Before science data could be acquired, however, the observatory had to be initialized, characterized, calibrated, and commissioned. A two phased operations approach was defined to complete this work. These phases were identified as In-Orbit Checkout (IOC) and Science Verification (SV). Because the observatory lifetime is cryogen-limited these operations had to be highly efficient. The IOC/SV operations design accommodated a pre-defined distributed organizational structure and a complex, cryogenic flight system. Many checkout activities were inter-dependent, and therefore the operations concept and ground data system had to provide the flexibility required for a 'short turn-around' environment. This paper describes the adaptive operations system design and evolution, implementation, and lessons-learned from the completion of IOC/SV.

space verification↗
NASA NTRS1995

The specification-based validation of reliable multicast protocol: Problem Report

Reliable Multicast Protocol (RMP) is a communication protocol that provides an atomic, totally ordered, reliable multicast service on top of unreliable IP multicasting. In this report, we develop formal models for RMP using existing automated verification systems, and perform validation on the formal RMP specifications. The validation analysis help identifies some minor specification and design problems. We also use the formal models of RMP to generate a test suite for conformance testing of the implementation. Throughout the process of RMP development, we follow an iterative, interactive approach that emphasizes concurrent and parallel progress of implementation and verification processes. Through this approach, we incorporate formal techniques into our development process, promote a common understanding for the protocol, increase the reliability of our software, and maintain high fidelity between the specifications of RMP and its implementation.

Wu, Yunqing↗
NASA NTRS2008

J-2X Abort System Development

The J-2X is an expendable liquid hydrogen (LH2)/liquid oxygen (LOX) gas generator cycle rocket engine that is currently being designed as the primary upper stage propulsion element for the new NASA Ares vehicle family. The J-2X engine will contain abort logic that functions as an integral component of the Ares vehicle abort system. This system is responsible for detecting and responding to conditions indicative of impending Loss of Mission (LOM), Loss of Vehicle (LOV), and/or catastrophic Loss of Crew (LOC) failure events. As an earth orbit ascent phase engine, the J-2X is a high power density propulsion element with non-negligible risk of fast propagation rate failures that can quickly lead to LOM, LOV, and/or LOC events. Aggressive reliability requirements for manned Ares missions and the risk of fast propagating J-2X failures dictate the need for on-engine abort condition monitoring and autonomous response capability as well as traditional abort agents such as the vehicle computer, flight crew, and ground control not located on the engine. This paper describes the baseline J-2X abort subsystem concept of operations, as well as the development process for this subsystem. A strategy that leverages heritage system experience and responds to an evolving engine design as well as J-2X specific test data to support abort system development is described. The utilization of performance and failure simulation models to support abort system sensor selection, failure detectability and discrimination studies, decision threshold definition, and abort system performance verification and validation is outlined. The basis for abort false positive and false negative performance constraints is described. Development challenges associated with information shortfalls in the design cycle, abort condition coverage and response assessment, engine-vehicle interface definition, and abort system performance verification and validation are also discussed.

Santi, Louis M.↗
NASA NTRSDate not supplied

Lean Model-Based Systems Engineering on the NASA High-Density Vertiplex Subproject

The High Density Vertiplex (HDV) subproject of NASA’s Advanced Air Mobility (AAM) project adopted Model-Based Systems Engineering (MBSE)in July of 2020, prior to subproject formulation. A small and lean team of HDV Systems Engineers(SE) are utilizing MagicDraw to execute NASA SE processes via MBSE. The SEs learned how to use MagicDraw from scratch and HDV is the first project for which the SEs have utilized MagicDraw. This paper will demonstrate project technical execution via MBSE, utilizing the digital elements built into the SysML (Systems Modeling Language). SysML provides a model-centric means of carrying out the NASA SE common technical processes by providing tools for complete system modeling, including requirements and interface management and design capture. The authors also leverage and extend SysML to perform other SE tasks, such as Verification and Validation (V&V)tracking. MBSE has two main purposes for HDV: 1) documenting the subproject’s logical architecture for distribution outside of the subproject, 2) capturing the subproject’s physical architecture in a single-source-of-truth for use by the subproject’s members. This paper details the challenges, lessons learned, and solutions that were encountered in implementing MBSE in the first iteration on a multi-iteration, full-lifecycle design, build, fly project.

Demetrios Katsaduros↗
NASA NTRSDate not supplied

Lean Model-Based Systems Engineering on the NASA High-Density Vertiplex Subproject

The High Density Vertiplex (HDV) subproject of NASA’s Advanced Air Mobility (AAM) project adopted Model-Based Systems Engineering (MBSE) in July of 2020, prior to subproject formulation. A small and lean team of HDV Systems Engineers (SE) are utilizing MagicDraw to execute NASA SE processes via MBSE. The SEs learned how to use MagicDraw from scratch and HDV is the first project for which the SEs have utilized MagicDraw. This presentation will demonstrate project technical execution via MBSE, utilizing the digital elements built into the SysML (Systems Modeling Language). SysML provides a model-centric means of carrying out the NASA SE common technical processes by providing tools for complete system modeling, including requirements and interface management and design capture. The authors also leverage and extend SysML to perform other SE tasks, such as Verification and Validation (V&V) tracking. MBSE has two main purposes for HDV: 1) documenting the subproject’s logical architecture for distribution outside of the subproject, 2) capturing the subproject’s physical architecture in a single-source-of-truth for use by the subproject’s members. This presentation details the challenges, lessons learned, and solutions that were encountered in implementing MBSE in the first iteration on a multi-iteration, full-lifecycle design, build, fly project.

systems engineering↗
NASA NTRS1995

The Specification-Based Validation of Reliable Multicast Protocol

Reliable Multicast Protocol (RMP) is a communication protocol that provides an atomic, totally ordered, reliable multicast service on top of unreliable IP multicasting. In this report, we develop formal models for RMP using existing automated verification systems, and perform validation on the formal RMP specifications. The validation analysis help identifies some minor specification and design problems. We also use the formal models of RMP to generate a test suite for conformance testing of the implementation. Throughout the process of RMP development, we follow an iterative, interactive approach that emphasizes concurrent and parallel progress of the implementation and verification processes. Through this approach, we incorporate formal techniques into our development process, promote a common understanding for the protocol, increase the reliability of our software, and maintain high fidelity between the specifications of RMP and its implementation.

Wu, Yunqing↗
NASA NTRS1998

Evaluation of the 29-km Eta Model: Objective Verification at Three Selected Stations - Part 1

This paper describes an objective verification of the National Centers for Environmental Prediction (NCEP) 29-km eta model from May 1996 through January 1998. The evaluation was designed to assess the model's surface and upper-air point forecast accuracy at three selected locations during separate warm (May - August) and cool (October - January) season periods. In order to enhance sample sizes available for statistical calculations, the objective verification includes two consecutive warm and cool season periods. Systematic model deficiencies comprise the larger portion of the total error in most of the surface forecast variables that were evaluated. The error characteristics for both surface and upper-air forecasts vary widely by parameter, season, and station location. At upper levels, a few characteristic biases are identified. Overall however, the upper-level errors are more nonsystematic in nature and could be explained partly by observational measurement uncertainty. With a few exceptions, the upper-air results also indicate that 24-h model error growth is not statistically significant. In February and August 1997, NCEP implemented upgrades to the eta model's physical parameterizations that were designed to change some of the model's error characteristics near the surface. The results shown in this paper indicate that these upgrades led to identifiable and statistically significant changes in forecast accuracy for selected surface parameters. While some of the changes were expected, others were not consistent with the intent of the model updates and further emphasize the need for ongoing sensitivity studies and localized statistical verification efforts. Objective verification of point forecasts is a stringent measure of model performance, but when used alone, is not enough to quantify the overall value that model guidance may add to the forecast process. Therefore, results from a subjective verification of the meso-eta model over the Florida peninsula are discussed in the companion paper by Manobianco and Nutter. Overall verification results presented here and in part two should establish a reasonable benchmark from which model users and developers may pursue the ongoing eta model verification strategies in the future.

Nutter, Paul A.↗
NASA NTRS1975

Lay out, test verification and in orbit performance of HELIOS a temperature control system

HELIOS temperature control system is described. The main design features and the impact of interactions between experiment, spacecraft system, and temperature control system requirements on the design are discussed. The major limitations of the thermal design regarding a closer sun approach are given and related to test experience and performance data obtained in orbit. Finally the validity of the test results achieved with prototype and flight spacecraft is evaluated by comparison between test data, orbit temperature predictions and flight data.

Brungs, W.↗
NASA NTRS1980

Retrofit and verification test of a 30-cm ion thruster

Twenty modifications were found to be necessary and were approved by design review. These design modifications were incorporated in the thruster documents (drawings and procedures) to define the J series thruster. Sixteen of the design revisions were implemented in a 900 series thruster by retrofit modification. A standardized set of test procedures was formulated, and the retrofit J series thruster design was verified by test. Some difficulty was observed with the modification to the ion optics assembly, but the overall effect of the design modification satisfies the design objectives. The thruster was tested over a wide range of operating parameters to demonstrate its capabilities.

Dulgeroff, C. R.↗