Repository logo

Browsing by Author "Wise, Daniel, committee member"

Now showing 1 - 4 of 4
  • Thumbnail Image
    ItemOpen Access
    Avoiding technical bankruptcy in system development: a process to reduce the risk of accumulating technical debt
    (Colorado State University. Libraries, 2023) Kleinwaks, Howard, author; Bradley, Thomas, advisor; Batchelor, Ann, advisor; Marzolf, Gregory, committee member; Wise, Daniel, committee member; Turner, John F., committee member
    The decisions made early in system development can have profound impacts on later capabilities of the system. In iterative systems development, decisions made in each iteration produce impacts on every future iteration. Decisions that have benefits in the short-term may damage the long-term health of the system. This phenomenon is known as technical debt. If not carefully managed, the buildup of technical debt within a system can lead to technical bankruptcy: the state where the system development can no longer proceed with its lifecycle without first paying back some of the technical debt. Within the schedule constrained development paradigm of iteratively and incrementally developed systems, it is especially important to proactively manage technical debt and to understand the potential long-term implications of decisions made to achieve short-term delivery goals. To enable proactive management of technical debt within systems engineering, it is first necessary to understand the state of the art with respect to the application of technical debt methods and terminology within the field. While the technical debt metaphor is well-known within the software engineering community, it is not as well known within the systems engineering community. Therefore, this research first characterizes the state of technical debt research within systems engineering through a literature review. Next, the prevalence of the technical debt metaphor among practicing systems engineers is established through an empirical survey. Finally, a common ontology for technical debt within systems engineering is proposed to enable clear and concise communication about the common problems faced in different systems engineering development programs. Using the research on technical debt in systems engineering and the ontology, this research develops a proactive approach to managing technical debt in iterative systems development by creating a decision support system called List, Evaluate, Achieve, Procure (LEAP). The LEAP process, when used in conjunction with release planning methods, can identify the potential for technical debt accumulation and eventually technical bankruptcy. The LEAP process is developed in two phases: a qualitative approach to provide initial assessments of the state of the system and a quantitative approach that models the effects of technical debt on system development schedules and the potential for technical bankruptcy based on release planning schedules. Example applications of the LEAP process are provided, consisting of the development of a conceptual problem and real applications of the process at the Space Development Agency. The LEAP process provides a novel and mathematical linkage of the temporal and functional dependencies of system development with the stakeholder needs, enabling proactive assessments of the ability of the system to satisfy those stakeholder needs. These assessments enable early identification of potential technical debt, reducing the risk of negative long-term impacts on the system health.
  • Thumbnail Image
    ItemOpen Access
    Leveraging operational use data to inform the systems engineering process of fielded aerospace defense systems
    (Colorado State University. Libraries, 2023) Eddy, Amy, author; Daily, Jeremy, advisor; Marzolf, Gregory, committee member; Miller, Erika, committee member; Wise, Daniel, committee member
    Inefficiencies in Department of Defense (DoD) Acquisition processes have been pervasive nearly as long as the DoD has existed. Stakeholder communication issues, funding concerns, large and overly complex organizational structures all play a role in adding challenges to those tasked with fielding, operating, and sustaining a complex aerospace defense system. As legacy defense systems begin to age, logistics and other supportability element requirements may change over time. While research literature supports the evidence that many stakeholders and senior leaders are aware of the issues and the DoD faces the impact those issues cause to mission performance, most research and attempts to improve the performance issues have been focused on high level restructuring of organizations or policy, processes, and procedures. There has been little research dedicated to identifying ways for working level logisticians and systems engineers to improve performance by leveraging operational use data. This study proposes a practical approach for working level logisticians and engineers to identify relationships between operational use data and supply performance data. This research focuses on linking negative aircraft events (discrepancies) to the supply events (requisitions) that result in downtime. This approach utilizes standard statistical methods to analyze operations, maintenance, and supply data collected during the Operations and Sustainment (O&S) phase of the life cycle. Further, this research identifies methods consistent with industry systems engineering practices to create new feedback loops to better inform the systems engineering life cycle management process, update requirements, and iterate the design of the enterprise system as a holistic entity that includes the physical product and its supportability elements such as logistics, maintenance, facilities, etc. The method identifies specific recommendations and actions for working level logisticians and systems engineers to prevent future downtime. The method is practical for the existing DoD organizational structure, and uses current DoD processes, all without increasing manpower or other resource needs.
  • Thumbnail Image
    ItemOpen Access
    Managing risk in commercial-off-the-shelf based space hardware systems
    (Colorado State University. Libraries, 2024) Herbert, Eric W., author; Bradley, Thomas, advisor; Sega, Ronald, advisor; Herber, Daniel, committee member; Shahroudi, Kamran, committee member; Wise, Daniel, committee member
    The space industry is experiencing a dynamic renaissance. From 2005 to 2021, the industry has exhibited a 265% increase in commercial and government investment [1]. The demand is forecasted to continue its upward trajectory by an added 55% by 2026 [1]. So, the aerospace industry continually seeks innovative space hardware solutions to reduce cost and to shorten orbit insertion schedules. Using Commercial-Off-the-Shelf (COTS) components to build space-grade hardware is one method that has been proposed to meet these goals. However, using non-space-grade COTS components requires designers to identify and manage risks differently early in the development stages. Once the risks are identified, then sound and robust risk management efforts can be applied. The methods used must verify that the COTS are reliable, resilient, safe, and able to survive rigorous and damaging launch and space environments for the mission's required longevity or that appropriate mitigation measures can be taken. This type of risk management practice must take into consideration form-fit-function requirements, mission objectives, size-weight-and-performance (SWaP) constraints, how the COTS will perform outside of its native applications, manufacturing variability, and lifetime expectations, albeit using a different lens than those traditionally used. To address these uncertainties associated with COTS the space industry can employ a variety of techniques like performing in-depth component selections, optimizing designs, instituting robust stress screening, incorporating protective and preventative measures, or subjecting the hardware to various forms of testing to characterize the hardware's capabilities and limitations. However, industrial accepted guidance to accomplish this does not reside in any standard or guide despite space program policies encouraging COTS use. One reason is because companies do not wish to reveal their proprietary methods used to evaluate COTS which, if broadcast, could benefit their market competition. Another is that high value spacecraft sponsors still cling to low-risk time consuming and expensive techniques that require the use of space hardware built with parts that have historical performance pedigrees. Keeping this data hidden does not help the space industry, especially when there is a push to field space systems that are built with modern technologies at a faster rate. This is causing a change in basic assumptions as stakeholders begin to embrace using parts from other industries such as the automotive, aviation, medical, and the like on a more frequent basis. No longer are COTS relegated to use in CubeSats or research and development spacecraft that have singular and limited missions that are expected to function for a brief period. This is because COTS that are produced for terrestrial markets are equally as dependable because of the optimized manufacturing and quality control techniques that reduce product variability. This increases the use of COTS parts in space hardware designs where until recently space programs had dared not to tread. But using COTS does come with a unique set of uncertainties and risks that still need to be identified and mitigated. Despite legacy risk management tools being mature and regularly practiced across a diverse industrial field, there is not a consensus on which risk management tools are best to use when evaluating COTS for space hardware applications. However, contained within technical literature amassed over the last twenty-plus years there exists significant systems engineering controls and enablers that can be used to develop robust COTS-use risk management frameworks. The controls and enablers become the basis to identify where aleatory and epistemic uncertainties exist within a COTS-based space system hardware design. With these statements in mind, unique activities can be defined to analyze, evaluate, and mitigate the uncertainties and the inherent risks to an acceptable level or to determine if a COTS-based design is not appropriate. These concepts were explored and developed in this research. Specifically, a series of COTS centric risk management frameworks were developed that can be used as a roadmap when considering integrating COTS into space hardware designs. From these frameworks unique risk evaluation processes were developed that identified the unique activities needed to effectively evaluate the non-space grade parts being considered. The activities defined in these risk evaluation processes were tailored to uncover as much uncertainty as possible so that appropriate risk mitigation techniques could be applied, design decisions could be quickly made from an informed perspective, and spacecraft fielding could be accomplished at an accelerated rate. Instead of taking five to ten years to field a spacecraft, it can now take less than one to three years. Thus, if effectively used, COTS integration can be a force multiplier throughout the space industry. But first, the best practices learned over the last few decades must be collected, synthesized, documented, and applied. To validate the risk frameworks discussed, a COTS-based space-grade secondary lithium-ion battery was chosen to demonstrate that the concepts could work. Unique risk evaluation activities were developed that took into consideration the spacecraft's mission, environment, application, and lifetime (MEAL) [2] attributes to characterize the battery's COTS cells, printed circuit board, electrical design, and electrical-electronic-electromechanical (EEE) performance, strengths, and weaknesses. The activities defined and executed included risk evaluation activities that included a variety of modeling, analyses, non-destructive examinations, destructive physical assessments, environmental testing, worst case scenario testing, and manufacturing assessments. These activities were developed based on the enablers and controls extracted from the data that was resident in the literature that was reviewed. The techniques employed proved quite successful in uncovering and mitigating numerous aleatory and epistemic uncertainties. The mitigation of these uncertainties significantly improved the battery's design and improved the battery's performance. As a result, the COTS-based battery was successfully built, qualified, and flown on a fleet of launch vehicles and payloads. The information that follows documents how the risk management frameworks were created, what influenced its architecture, and how these were successfully validated. Validating the COTS centric risk management framework was important because it demonstrated the risk management frameworks' utility to uncover uncertainty. It also proved that methods exist that can be readily employed that are not typically within the scope of traditional space hardware design and qualification techniques. This is important because it provides the industry a new set of systems engineering tools that can be employed to limit the impact of supply chain constraints, reduce reliance on expensive low-yield hardware procurement practices, and minimize the amount of obsolete hardware in designs which tend to constrain the space system hardware's performance. As a result, the techniques developed in this research start to fill a gap that exists in the space industry's systems engineering toolbox.
  • Thumbnail Image
    ItemOpen Access
    Prediction and mitigation strategies for the transient thermal performance of low thermal resistance microchannel evaporators
    (Colorado State University. Libraries, 2024) Anderson, Caleb Del, author; Bandhauer, Todd M., advisor; Venayagamoorthy, Karan, committee member; Windom, Bret, committee member; Wise, Daniel, committee member
    Microchannel flow boiling heat transfer offers an effective thermal management solution for high heat flux microelectronic devices such as laser diodes. The high heat transfer rates, nearly isothermal flow conditions, high surface area-to-volume ratios, and lower required pumping powers facilitate smaller component systems while more efficiently cooling devices and reducing packaging stresses associated with thermal expansion when compared with single-phase cooling systems. Although much study has been dedicated to optimizing steady state flow boiling performance, the typically highly transient operation of these microelectronic devices leads to unsteady spikes in heat flux and, subsequently, in device temperatures and may potentially exacerbate flow instabilities present at steady state. The low thermal capacitance of the package that often accompanies the low thermal resistance of microchannel evaporators increases the potential for device damage and failure since large temperature swings are more likely. Predicting and mitigating the transient response of a low thermal resistance microchannel evaporator is paramount to practical application as a thermal management technique. In this work, temperature, pressure, and flow visualization measurements during stepped heat loads on two, low thermal resistance, microchannel evaporators revealed the presence of severe vapor backflow, large temperature overshoots, and impacted flow dynamics at the onset of nucleate boiling (ONB) despite the stability and high performance of the device under steady state heating conditions. These overshoots were exacerbated with higher heating rates and reduced subcooling but were generally improved with higher flow rates. Applying a slower heating rate greatly improved the transient thermal response, reducing both peak temperature and vapor backflow. Channel and inlet orifice geometry were found to greatly impact the performance, with smaller channels and smaller orifice-to-channel restriction ratios resulting in intensified vapor backflow and temperature spikes, despite offering improved steady state performance. A computational model embedded in a reduced order design tool was created and validated with the experiments. Two separate models were created due to the different transient conditions observed between the two tested microchannel evaporators. The models allow predictive modeling of these evaporators to determine the impact of the transient heating behavior on microchannel evaporator devices. The effect of incorporating gallium-based, solid-liquid Phase Change Materials (PCMs) was studied semi-empirically by simulating the performance of a virtual test section with predicted properties of a microchannel evaporator combined with gallium and gallium-composite foam PCMs. Properties of the PCMs were estimated and used to predict the test section thermal response under a range of PCM volumes. Models assuming single phase performance were conducted initially and the resulting predicted heat rate to the fluid applied experimentally to the test section heater to determine the temperature response. It was found that the simulated addition of the PCM slightly reduced the ONB temperatures but did not affect the peak temperature experienced by the device. The applied heating rate, however, did not consider the increased thermal resistance to the refrigerant fluid during the transient vapor backflow regime. The effect was most pronounced in the PCMs with the largest exposed surface area and with thermal conductivity-enhanced PCM composites comprised of gallium infiltrated in a copper foam matrix. Additional PCM models utilizing the transient flow boiling model were subsequently run on a series of representative heat load test cases comparing the performance of a gallium-nickel and gallium-copper composite with similar dimensions to the earlier simulations. Key assumptions included the same ONB temperatures and vapor backflow conditions as the baseline cases without PCMs. The models predicted significantly lowered peak device temperatures due to the heat absorption into the PCM during the transient vapor backflow phase. The effect was dependent on the PCM thickness, latent heat, and thermal conductivity, reflecting trade-offs in material. In addition, peak temperature variability observed experimentally across multiple trials at the same nominal testing conditions was greatly reduced with the inclusion of a PCM.