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All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Making & Breaking the Rules for DED Design

Design for Additive Manufacturing (DfAM) is widely used to describe design activities and guidelines employed in the creation of Additively Manufactured (AM) parts. Basic design rules for widely adopted processes like Powder Bed Fusion (PBF) are relatively understood including material performance, part size constraints, self-supporting angles, overhangs, wall thicknesses, and feature resolution. Complexity is often inherent with PBF using organically inspired solutions through generative design and topology optimization software to create designs that often cannot be realized via traditional manufacturing processes. The design rules for Directed Energy Deposition (DED) are less well known, and, in some cases, the lack of understanding is likely inhibiting broader application of the various DED processes. This presentation covers key design rules for DED fusion processes and elucidates opportunities like multi-material deposition and build approaches ranging from basic features to complex large-scale parts. Complementary to the opportunistic characteristics of DfAM for DED, Manufacture for AM (MfAM) encompasses the restrictive aspects of the manufacturing lifecycle with limitations due to bead width and wall thickness, self-supporting angles, surface texture, microstructural evolution, and residual stresses. AM enabled part design must always consider the entire value chain starting with incoming feedstock (e.g. plate, wire, or powder) and progressing through the printing process, post-processing (e.g. machining, inspection), and final system assembly. Key considerations, like the tradeoffs between feature resolution and build rate, for process and part selection and economic assessments will be discussed as DED is often traded against other AM processes. After highlighting typical DED design rules, we will also show how some of those rules can be broken via use cases and part designs that span the full spectrum of DED processes with examples of various DED part designs.

Additive Manufacturing↗
NASA NTRS1986

Towards a general object-oriented software development methodology

An object is an abstract software model of a problem domain entity. Objects are packages of both data and operations of that data (Goldberg 83, Booch 83). The Ada (tm) package construct is representative of this general notion of an object. Object-oriented design is the technique of using objects as the basic unit of modularity in systems design. The Software Engineering Laboratory at the Goddard Space Flight Center is currently involved in a pilot program to develop a flight dynamics simulator in Ada (approximately 40,000 statements) using object-oriented methods. Several authors have applied object-oriented concepts to Ada (e.g., Booch 83, Cherry 85). It was found that these methodologies are limited. As a result a more general approach was synthesized with allows a designer to apply powerful object-oriented principles to a wide range of applications and at all stages of design. An overview is provided of this approach. Further, how object-oriented design fits into the overall software life-cycle is considered.

Seidewitz, ED↗
NASA NTRS1998

Reuse Metrics for Object Oriented Software

One way to increase the quality of software products and the productivity of software development is to reuse existing software components when building new software systems. In order to monitor improvements in reuse, the level of reuse must be measured. In this NASA supported project we (1) derived a suite of metrics which quantify reuse attributes for object oriented, object based, and procedural software, (2) designed prototype tools to take these measurements in Ada, C++, Java, and C software, (3) evaluated the reuse in available software, (4) analyzed the relationship between coupling, cohesion, inheritance, and reuse, (5) collected object oriented software systems for our empirical analyses, and (6) developed quantitative criteria and methods for restructuring software to improve reusability.

Bieman, James M.↗
NASA NTRS2016

Buckling Design and Imperfection Sensitivity of Sandwich Composite Launch-Vehicle Shell Structures

Composite materials are increasingly being considered and used for launch-vehicle structures. For shell structures, such as interstages, skirts, and shrouds, honeycomb-core sandwich composites are often selected for their structural efficiency. Therefore, it is becoming increasingly important to understand the structural response, including buckling, of sandwich composite shell structures. Additionally, small geometric imperfections can significantly influence the buckling response, including considerably reducing the buckling load, of shell structures. Thus, both the response of the theoretically perfect structure and the buckling imperfection sensitivity must be considered during the design of such structures. To address the latter, empirically derived design factors, called buckling knockdown factors (KDFs), were developed by NASA in the 1960s to account for this buckling imperfection sensitivity during design. However, most of the test-article designs used in the development of these recommendations are not relevant to modern launch-vehicle constructions and material systems, and in particular, no composite test articles were considered. Herein, a two-part study on composite sandwich shells to (1) examine the relationship between the buckling knockdown factor and the areal mass of optimized designs, and (2) to interrogate the imperfection sensitivity of those optimized designs is presented. Four structures from recent NASA launch-vehicle development activities are considered. First, designs optimized for both strength and stability were generated for each of these structures using design optimization software and a range of buckling knockdown factors; it was found that the designed areal masses varied by between 6.1% and 19.6% over knockdown factors ranging from 0.6 to 0.9. Next, the buckling imperfection sensitivity of the optimized designs is explored using nonlinear finite-element analysis and the as-measured shape of a large-scale composite cylindrical shell. When compared with the current buckling design recommendations, the results suggest that the current recommendations are overly conservative and that the development of new recommendations could reduce the acreage areal mass of many composite sandwich shell designs by between 4% and 19%, depending on the structure.

Schultz, Marc R.↗
NASA NTRS2016

Design and Development of a Flight Route Modification, Logging, and Communication Network

There is an overwhelming desire to create and enhance communication mechanisms between entities that operate within the National Airspace System. Furthermore, airlines are always extremely interested in increasing the efficiency of their flights. An innovative system prototype was developed and tested that improves collaborative decision making without modifying existing infrastructure or operational procedures within the current Air Traffic Management System. This system enables collaboration between flight crew and airline dispatchers to share and assess optimized flight routes through an Internet connection. Using a sophisticated medium-fidelity flight simulation environment, a rapid-prototyping development, and a unified modeling language, the software was designed to ensure reliability and scalability for future growth and applications. Ensuring safety and security were primary design goals, therefore the software does not interact or interfere with major flight control or safety systems. The system prototype demonstrated an unprecedented use of in-flight Internet to facilitate effective communication with Airline Operations Centers, which may contribute to increased flight efficiency for airlines.

Merlino, Daniel K.↗
DOE OSTI2025

Designing a Framework for Solving Multiobjective Simulation Optimization Problems

Multiobjective simulation optimization (MOSO) problems are optimization problems with multiple conflicting objectives, where evaluation of at least one of the objectives depends on a black-box numerical code or real-world experiment, which we refer to as a simulation. Whereas an extensive body of research is dedicated to developing new algorithms and methods for solving these and related problems, it is challenging and time-consuming to integrate these techniques into real-world production-ready solvers. This is partly because of the diversity and complexity of modern state-of-the-art MOSO algorithms and methods and partly because of the complexity and specificity of many real-world problems and their corresponding computing environments. The complexity of this problem is only compounded when introducing potentially complex and/or domain-specific surrogate-modeling techniques, problem formulations, design spaces, and data acquisition functions. Here, this paper carefully surveys the current state of the art in MOSO algorithms, techniques, and solvers, as well as problem types and computational environments where MOSO is commonly applied. We then present several key challenges in the design of a parallel multiobjective simulation optimization framework (ParMOO) and how they have been addressed. Finally, we provide two case studies demonstrating how customized ParMOO solvers can be quickly built and deployed to solve real-world MOSO problems.

engineering design optimization↗
DOE OSTI2024

Enhancing the Functionality of a Hollow Scaffold Solid State Bioreactor via Computer Aided Design Optimization

The concern over greenhouse gases, methane (CH 4 ) and carbon dioxide (CO 2 ), is increasing rapidly. There have been strides to find solutions to this global issue but there is not a clear path to a successful end goal. The concentration of CH 4 and CO 2 in the atmosphere has increased significantly over the last 60 years, methane is a great source of concern due to its ability to trap a high amount of heat in the atmosphere. These greenhouse gases contribute to global warming which has caused changes in the environment, including the melting of ice caps, and altered weather patterns. Solutions for these pressing challenges have led to different avenues of methane mitigation one of which is the development of solid-state bioreactors. These reactors harness the power of biological species that have evolved to use methane as an energy source. The development and optimization of Hollow Scaffold Solid State Bioreactors (HS-SSBR) has become readily available due to the advancements in additive manufacturing technology and accessibility of computer aided design (CAD) software. With laboratory scale experiments, time and effort are of great importance. Enhancing the design of the HS-SSBR to create a more user-friendly interface, but also increase the functionality of the reactor. The reactor's design improvements focus on better dispersion of methane and circulation of media.

36 MATERIALS SCIENCE↗
NASA NTRS1978

Development of user guidelines for ECAS display design, volume 1

Experiment computer application software (ECAS) display design and command usage guidelines were developed, which if followed by spacelab experiments, would standardize methods and techniques for data presentation and commanding via ECAS. These guidelines would provide some commonality among experiments which would enhance crew training and flight operations. The guidelines are applicable to all onboard experiment displays, whether allocated by ECAS or a dedicated experiment processor. A brief description of the spacelab data display system characteristics and of the services provided by the experiment computer operating system is included. Guidelines concerning data presentation and layout of alphanumeric and graphic information are presented along with guidelines concerning keyboard commanding and command feedback.

Dodson, D. W.↗
NASA NTRS2015

Simulation and Measurement of Stray Light in the CLASP

We are planning an international rocket experiment Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is (2015 planned) that Lyman Alpha line polarization spectroscopic observations from the sun. The purpose of this experiment, detected with high accuracy of the linear polarization of the Ly􀉲 lines to 0.1% by using a Hanle effect is to measure the magnetic field of the chromosphere-transition layer directly. For total flux of the sun visible light overwhelmingly larger and about 200 000 times the Ly􀉲 line wavelength region, also hinder to 0.1% of the polarization photometric accuracy achieved in the stray light of slight visible light. Therefore we were first carried out using the illumination design analysis software called stray light simulation CLASP Light Tools. Feature of this simulation, using optical design file (ZEMAX format) and structural design file (STEP format), to reproduce realistic CLASP as possible to calculate machine is that it was stray study. And, at the stage in the actual equipment that made the provisional set of CLASP, actually put sunlight into CLASP using coelostat of National Astronomical Observatory of Japan, was subjected to measurement of stray light (San test). Pattern was not observed in the simulation is observed in the stray light measurement results need arise that measures. However, thanks to the stray light measurement and simulation was performed by adding, it was found this pattern is due to the diffracted light at the slit. Currently, the simulation results is where you have taken steps to reference. In this presentation, we report the stray light simulation and stray light measurement results that we have implemented

CLASP↗
NASA NTRS1997

Reuse of a Formal Model for Requirements Validation

This paper reports experience from how a project engaged in the process of requirements analysis for evolutionary builds can reuse the formally specified design model produced for a similar, earlier project in the same domain. Two levels of reuse are described here. First, a formally specified generic design model was generated on one project to systematically capture the design commonality in a set of software monitors on board a spacecraft. These monitors periodically check for faults and invoke recovery software when needed. The paper summarizes the use of the design model to validate the software design of the various monitors on that first project. Secondly, the paper describes how the formal design model created for the first project was reused on a second, subsequent project. The model was reused to validate the evolutionary requirements for the second project's software monitors, which were being developed in a series of builds. Some mismatches due to the very different architectures on the two projects suggested changes to make the model more generic. In addition, several advantages to the reuse of the first project's formal model on the second project are reported.

Lutz, Robyn R.↗
NASA NTRS2010

Optimization Testbed Cometboards Extended into Stochastic Domain

COMparative Evaluation Testbed of Optimization and Analysis Routines for the Design of Structures (CometBoards) is a multidisciplinary design optimization software. It was originally developed for deterministic calculation. It has now been extended into the stochastic domain for structural design problems. For deterministic problems, CometBoards is introduced through its subproblem solution strategy as well as the approximation concept in optimization. In the stochastic domain, a design is formulated as a function of the risk or reliability. Optimum solution including the weight of a structure, is also obtained as a function of reliability. Weight versus reliability traced out an inverted-S-shaped graph. The center of the graph corresponded to 50 percent probability of success, or one failure in two samples. A heavy design with weight approaching infinity could be produced for a near-zero rate of failure that corresponded to unity for reliability. Weight can be reduced to a small value for the most failure-prone design with a compromised reliability approaching zero. The stochastic design optimization (SDO) capability for an industrial problem was obtained by combining three codes: MSC/Nastran code was the deterministic analysis tool, fast probabilistic integrator, or the FPI module of the NESSUS software, was the probabilistic calculator, and CometBoards became the optimizer. The SDO capability requires a finite element structural model, a material model, a load model, and a design model. The stochastic optimization concept is illustrated considering an academic example and a real-life airframe component made of metallic and composite materials.

Patnaik, Surya N.↗
NASA NTRS1999

Comparison of Integrated Analysis Methods for Two Model Scenarios

Integrated analysis methods have the potential to substantially decrease the time required for analysis modeling. Integration with computer aided design (CAD) software can also allow a model to be more accurate by facilitating import of exact design geometry. However, the integrated method utilized must sometimes be tailored to the specific modeling situation, in order to make the process most efficient. Two cases are presented here that illustrate different processes used for thermal analysis on two different models. These examples are used to illustrate how the requirements, available input, expected output, and tools available all affect the process selected by the analyst for the most efficient and effective analysis.

Amundsen, Ruth M.↗
DOE OSTI2024

RetroTide v1.0

RetroTide is a retrobiosynthesis software tool, designed to guide the design of biological pathways to make valuable small molecules. It takes as input a desired small molecule chemical structure, and outputs a design for a polyketide synthase enzyme (PKS) that has the closest possible chemical structure, as accessible by PKS chemistry. It is developed as a Python software library, and internally performs a search of the PKS design space, while simulating the chemicals produced by each design.

Backman, Tyler↗
NASA NTRS1991

Safety

Software requirements, design, implementation, verification and validation, and especially management are affected by the need to produce safe software. This paper discusses the changes in the software life cycle that are necessary to ensure that software will execute without resulting in unacceptable risk. Software is being used increasingly to monitor and control safety-critical processes in which a run-time failure or error could result in unacceptable losses such as death, injury, loss of property, or environmental harm. Examples of such processes maybe found in transportation, energy, aerospace, basic industry, medicine, and defense systems.

Leveson, Nancy G.↗
NASA NTRS1997

The Design of Model-Based Training Programs

This paper proposes a model-based training program for the skills necessary to operate advance avionics systems that incorporate advanced autopilots and fight management systems. The training model is based on a formalism, the operational procedure model, that represents the mission model, the rules, and the functions of a modem avionics system. This formalism has been defined such that it can be understood and shared by pilots, the avionics software, and design engineers. Each element of the software is defined in terms of its intent (What?), the rationale (Why?), and the resulting behavior (How?). The Advanced Computer Tutoring project at Carnegie Mellon University has developed a type of model-based, computer aided instructional technology called cognitive tutors. They summarize numerous studies showing that training times to a specified level of competence can be achieved in one third the time of conventional class room instruction. We are developing a similar model-based training program for the skills necessary to operation the avionics. The model underlying the instructional program and that simulates the effects of pilots entries and the behavior of the avionics is based on the operational procedure model. Pilots are given a series of vertical flightpath management problems. Entries that result in violations, such as failure to make a crossing restriction or violating the speed limits, result in error messages with instruction. At any time, the flightcrew can request suggestions on the appropriate set of actions. A similar and successful training program for basic skills for the FMS on the Boeing 737-300 was developed and evaluated. The results strongly support the claim that the training methodology can be adapted to the cockpit.

Polson, Peter↗
NASA NTRS2003

Software for Automated Reading of STEP Files by I-DEAS(trademark)

A program called "readstep" enables the I-DEAS(tm) computer-aided-design (CAD) software to automatically read Standard for the Exchange of Product Model Data (STEP) files. (The STEP format is one of several used to transfer data between dissimilar CAD programs.) Prior to the development of "readstep," it was necessary to read STEP files into I-DEAS(tm) one at a time in a slow process that required repeated intervention by the user. In operation, "readstep" prompts the user for the location of the desired STEP files and the names of the I-DEAS(tm) project and model file, then generates an I-DEAS(tm) program file called "readstep.prg" and two Unix shell programs called "runner" and "controller." The program "runner" runs I-DEAS(tm) sessions that execute readstep.prg, while "controller" controls the execution of "runner" and edits readstep.prg if necessary. The user sets "runner" and "controller" into execution simultaneously, and then no further intervention by the user is required. When "runner" has finished, the user should see only parts from successfully read STEP files present in the model file. STEP files that could not be read successfully (e.g., because of format errors) should be regenerated before attempting to read them again.

Pinedo, John↗