Subsystem Level Testing Research Articles

The Warm Electron Beam Ion Trap (WEBIT): An instrument for ground calibration of space-borne x-ray spectrometers.

The warm electron beam ion trap (WEBIT) at Lawrence Livermore National Laboratory is being developed as a pre-launch, ground calibration source for space-borne, high-throughput, high-resolution x-ray spectrometers, such as the x-ray imaging and spectroscopy mission Resolve quantum calorimeter. Historically, calibration sources for calorimeter spectrometers have relied on characteristic line emission from x-ray tubes, fluorescing metals, and radioactive sources. The WEBIT, by contrast, relies on emission from x-ray transitions in highly charged ions, for example, hydrogen-like and helium-like ions, whose energies are well known and whose line shapes are relatively simple. The WEBIT can create astrophysically relevant ions whose x-ray emission falls in the 0.3-12 keV science bandpass of Resolve and has a portable design advantageous for a calibration source. The WEBIT will be used to help calibrate Resolve's instrumental line shape and gain scale as a function of various operational parameters during both detector subsystem level testing and instrumental level testing.

The Modelling and Correlation Procedure for Assessment of Vibration Performance of a Heavy Commercial Truck

Application of mathematical modelling and numerical methods is a key element of optimum vehicle development process. Upfront CAE (Computer Aided Engineering) simulations of vehicle attributes are required to select designs that meet vehicle attribute targets and legal requirements. CAE is an attractive approach to predict and optimize the performance of the vehicle, and to make decisions in terms of attribute trade-offs before the vehicle prototypes are available. Even though there are many commercial software packages available, the task of correlation of the CAE model to vehicle test conditions is not a trivial task. In this paper, a systematic correlation methodology starting from subsystem level to full vehicle level is presented. Full vehicle correlation is demonstrated on Powertrain Idle NVH evaluation. Correlation results show that simulation model is highly correlated to the subsystem and vehicle level test data and, therefore it can be reliably used in the product development cycle.

Uncertainty Quantification of System Model Parameters with Component Level and Sub-System Level Tests

Uncertainty Quantification of System Model Parameters with Component Level and Sub-System Level Tests

Probability-informed testing for reliability assurance through Bayesian hypothesis methods

Bayesian inference techniques play a central role in modern risk and reliability evaluations of complex engineering systems. These techniques allow the system performance data and any relevant associated information to be used collectively to calculate the probabilities of various types of hypotheses that are formulated as part of reliability assurance activities. This paper proposes a methodology based on Bayesian hypothesis testing to determine the number of tests that would be required to demonstrate that a system-level reliability target is met with a specified probability level. Recognizing that full-scale testing of a complex system is often not practical, testing schemes are developed at the subsystem level to achieve the overall system reliability target. The approach uses network modeling techniques to transform the topology of the system into logic structures consisting of series and parallel subsystems. The paper addresses the consideration of cost in devising subsystem level test schemes. The developed techniques are demonstrated using several examples. All analyses are carried out using the Bayesian analysis tool WinBUGS, which uses Markov chain Monte Carlo simulation methods to carry out inference over the network.

Self-assembling wireless autonomously reconfigurable module design concept

Presently, most spacecraft are one-of-a-kind or few-of-a-kind creations, optimized for some particular task, and containing as much functionality as is feasible. While components or subsystems may be re-used from one spacecraft to the next, there is a high degree of customization, which leads to increases in testing and verification costs, along with reductions in reliability. The self-assembling wireless autonomous reconfigurable module concept proposes a set of small satellites which can perform the functionality of a large integrated system, but have the advantages of avoiding substantial up-front design cost, flexibility in the reconfiguration of the system, subsystem level testing capability, marginal cost benefits of large production runs, and ease of on-orbit subsystem repair and replacement. These small satellite modules can be reconfigured to execute a large variety of tasks, such as astronaut assistance or solar tracking. The modules use wireless communication, which minimizes hard interfaces between subsystems, and remaining structural interfaces are standardized and autonomous. Different modules, such as computer, attitude control and propulsion, work together to provide autonomy in sensing and mobility. A set of prototype modules have been constructed and tested for structural, electrical, data transfer, and general performance measurements. Results show full compliance with design requirements.

Technical and programmatic constraints in dynamic verification of satellite mechanical systems

The development and verification of satellite systems covers various programmatic options. In the mechanical systems area, spacecraft test verification options include static, shaker vibration, modal survey, thermoelastic, acoustic, impact and other environmental tests. Development and verification tests influence the provision of satellite hardware, e.g. the structural model, engineering model, flight model, postflight etc., which need to be adopted by projects. In particular, adequate understanding of the satellite dynamic characteristics is essential for flight acceptance by launcher authorities. In general, a satellite shaker vibration test is requested by launcher authorities for expendable launchers. For the latter the launcher/satellite interface is well defined at the launcher clampband/separation device, and the interface is considered conveniently as a single point at the centre of the clampband. Recently the need has been identified to refine the interface idealization in launcher/satellite coupled loads dynamic analysis, particularly in cases where concentrated satellite loads are introduced at the interface, e.g. platform support struts. In the case of shuttle payloads, which are attached directly to the shuttle, shaker vibration at a single interface is not meaningful. Shuttle launcher authorities require identification of the satellite dynamic characteristics, e.g. by modal survey, and structural verification can be demonstrated by analysis, testing or a combination of analysis and testing. In the case of large satellite systems, which cannot be tested due to the limitation of the vibration shaker test facilities, a similar approach can be adapted for expendable launchers. In such an approach the dynamic characteristics of the satellite system will be identified by the modal survey test, and detailed satellite verification/qualification will be accomplished by analysis supported by subsystem and component level tests. Mechanical strength verification is usually accomplished by the static/centrifuge test. Shaker vibration tests cover dynamic response and support subsequent functional tests, e.g. deployment of appendages. As a result, the unavailability of the shaker vibration tests will have distinct implications on the functional and satellite alignment tests, particularly in cases where such tests cannot be easily performed at component and subsystem level. Consequently, alternative test verification of the satellite system to the classical shaker vibration test will vary significantly from project to project. The feasibility and constraints of an alternative satellite shaker vibration test to classical satellite system shaker vibration will be considered for the verification/qualification of satellite systems. This paper will present the utilization of emerging technologies to enhance space systems while striving for a competitive edge in satellite applications by reducing the effort for the end-to-end system. The limitations in adequately representing vibroacoustic excitation of large payload units with random shaker excitation will be presented. The employment of shaker vibration advancements to cover modal survey tests will be presented. The considerations will be amplified with realistic application examples for satellites under development. The application details will cover a wide spectrum of underlying technical and programmatic requirements.

Overlay performance of x-ray steppers in IBM Advance Lithography Facility

This article describes the overlay performance of the Suss XRS200/3 synchrotron compatible x-ray steppers installed in the IBM Advanced Lithography Facility. The Suss XRS200/3 uses a video-based brightfield microscope alignment system. The overall performance of the stepper was described previously. This article will specifically focus on the test, optimization, and performance of the alignment system. In the Suss alignment system, the quality of optics and test methods of the optical assembly was a critically important factor in achieving the 110 nm overlay quoted previously. A detailed discussion is given on the selection and characterization of these alignment optics, along with the subsystem level tests used to ensure performance of the complete imaging assembly prior to and after installation on the main stepper body. The overlay test methodology and data obtained during the acceptance testing is also discussed in detail. The exposure testing was designed to measure a full range of performance of the stepper. Indeed, overlay ranged from 50 nm (mean plus three sigma) on the very best levels to in excess of 150 nm on the most difficult. Sensitivity of the alignment system to small film thickness changes was tested along with alignment precision as a function of alignment mark depth or signal contrast.

Ground Testing of the SNAP 10A/Agena Space System

The SNAP 10A/Agena Space System, developed under the joint direction of the Air Force Systems Division and the Atomic Energy Commission, is described with emphasis on the inter-relationship of the several subsystems and their integration with the Nuclear Power Unit. Development and refinement of the space system design by means of integrated subsystem and system level testing performed on a full-scale functional mockup of the spacecraft and payload is discussed with emphasis on the instrumentation and telemetry subsystems. The method of demonstrating electromagnetic compatibility of the space system is described, both as performed on the functional mockup and the flight vehicle proper. Final pre-flight system testing of the spacecraft, including the payload and payload simulator, up to the time of launch is discussed. Particular emphasis is placed on the discovery and resolution of problems that appeared only at the system level of testing and those that were the direct result of the uniqueness of the nuclear reactor payload. Integrating a nuclear power unit into a space vehicle and ground testing of the resultant system presented many typical aerospace system problems, but no truly new ones and certainly no insolvable ones. The technology resulting from the development of the SNAP 10A/Agena system is directly applicable to nuclear space systems in general. Subsequent nuclear power systems can be less experimental in nature and require less complex instrumentation and control, with a corresponding reduction in the complexity and time span of ground testing.