Nicole C. Jordan

Flexibility: a multi-disciplinary literature review and a research agenda for designing flexible engineering systems

Flexibility, despite its popularity, is not yet an academically mature concept – compared with optimality and robustness, for example. Flexibility is nevertheless recognised as a critical attribute of a system, a process, or an organisation; it is needed in order to cope with uncertainty and change, and implies an ability to change and adapt to a range of conditions. An interesting observation has been made that the concept of flexibility is today where the notion of quality was some 20 years ago, ‘vague and difficult to improve, yet critical to competitiveness’. In this paper, we review the concept of flexibility as discussed in a number of academic disciplines that have grappled with this concept, and highlight the major themes, challenges, and limitations in each case. We analyse flexibility in the context of decision theory, real options, manufacturing systems, and engineering design. We also provide a critical assessment of the use and abuse of the word flexibility in the technical literature. Finally, we propose a series of research questions that can help transform flexibility into a quantifiable engineering attribute and grow this concept to the level of maturity of optimisation and robustness in system design.

Balancing the Needs for Space Research and National Security in the ITAR

Current export control policies, drafted during the Cold War, require reassessment in light of fundamental changes in the international security environment. The interconnectedness of the global economy, brought about by new technologies that facilitate international collaboration and knowledge sharing, is challenging the American export control framework. Underlying is a tension between the needs for innovation, driven by the free exchange of ideas, and security needs, aiming to prevent potentially sensitive knowledge and hardware from falling into the wrong hands. Academic space research institutions are particularly affected by the International Traffic in Arms Regulations (ITAR) United States Munitions List, which controls broad categories of space systems. Many members of the academic community champion a reactionary approach whereby restricting research in a given area requires that a risk be demonstrated. This stands in contrast to the precautionary approach towards the proliferation of space technology embodied in the ITAR wherein the risk of technology transfer is mitigated through the liberal use of restrictions, controls and State Department oversight. Effective export controls must balance the benefits of requiring that certain technologies be used exclusively by certain U.S. interests with the danger of undermining future innovation. A notional model, supported by interviews and analyses, describes the longand short-term effects of ITAR upon national security. The notional model provides valuable insight into the dynamics of shortand longterm national security needs and the influence of export control on those needs. Further refinement of the model will allow the influence of potential changes in ITAR procedures to be evaluated and understood. The effects on national security of strengthening or relaxing components of export restrictions can be understood through an expansion of the model and by holding interviews with a variety of stakeholders involved in the innovation, legislation, and enforcement processes.

The Extravehicular Mobility Unit: case study in requirements evolution

Requirements are rarely static, and are ever more likely to evolve as the development time of a system stretches out and its service life increases. In this paper, we discuss the evolution of requirements for the U.S. spacesuit, the Extravehicular Mobility Unit (EMU), as a case study in the need for flexibility in system design. We explore one fundamental environmental change, using the Shuttle EMU aboard the International Space Station (ISS), and the resulting EMU requirement and design changes. The EMU, like most complex systems, faces considerable uncertainty during its service life. Changes in the technical, political, or economic environment cause changes in requirements, which in turn necessitate design modifications or upgrades. We make the case that flexibility is a key attribute that needs to be embedded in the design of long-lived systems to enable them to efficiently meet the inevitability of changing requirements after they have been fielded.

Development and Validation of a Multidisciplinary Spacesuit Model

In this paper, we develop a novel multidisciplinary spacesuit model. Many models exist for individual spacesuit subsystems, for example the thermal subsystem; however, no one model yet exists that incorporates all subsystems simultaneously. Although a partial understanding of the operation and performance of a spacesuit at the subsystem level can be attained using existing models, the spacesuit is a highly-interdependent, human-sized spacecraft, and an integrated model is needed to aid in the understanding, design, and operation of the spacesuit as a complex engineering system. First, we describe the overall operation of the model, then go into details of the four subsystems: thermal, structures, oxygen flow, and power. Next, we validate the model against the current U.S. spacesuit, the Extra-Vehicular Mobility Unit (EMU), at the system and subsystem level. This model is used in a companion paper to conduct multi-objective optimization. These results should prove useful in the design of the next-generation spacesuit.

Multi-Objective Optimization Approaches in Spacesuit Design

In this paper, we use a multidisciplinary spacesuit model developed in a companion paper and an N-Branch Tournament Genetic Algorithm to optimize spacesuit designs for a Mars environment. The spacesuit design is optimized to minimize mass, stowage volume, and pre-breathe time prior to a spacewalk, and to maximize spacesuit mobility. These four objectives represent the primary measures of utility for a spacesuit design. This paper describes both a framework and process for spacesuit optimization, and demonstrates a new multi-objective visualization method for this four-objective design challenge. We discuss the preliminary optimization results as they relate to spacesuit design considerations. This initial investigation suggests that the power and CO2 removal technologies have little impact on the spacesuit architecture, whereas suit hardness and suit pressure have a far greater impact. Often suit pressure and hardness are determined at the beginning of the design eort and these early choices greatly influence the overall characteristics of the spacesuit. These results should be useful in the design of the next generation of spacesuits.

Modularity in Spacesuit Design: Using Form-to-Function Mapping to Inform Design Choices

The purpose of this paper is to explore the means by which flexibility can be incorporated into the design of spacesuits. Because the design lifetime of spacesuits is on the order of decades, it is important that they be able to adapt to change in their requirements. Flexibility is defined as the ability for a system to meet changes in requirements after it has been fielded. We argue that one means of achieving flexibility is via modular design, defined as a one-to-one mapping between form and function. Through examination of the form decompositions and form-to-function maps of the U.S. Spacesuit, the Extravehicular Mobility Unit (EMU), it is apparent that the EMU’s architecture is highly integrated. Reorganizing the form decomposition of the EMU to group similar components leads to a more modular and thus flexible architecture. A similar technique could be used to evaluate proposed architectures for future spacesuits.

The Case for an Integrated Systems Approach to Extravehicular Activity

In this paper, we make the case for an integrated systems approach to the design and implementation of Extravehicular Activity (EVA). We define the EVA system as the set of hardware that enables EVA including the spacesuit, airlock, tools and mobility aids, as well as personnel and intangibles such as training, procedures, and software. In the context of planetary EVA, the system expands to include a rover, dust mitigation devices, and scientific instruments. The EVA system is in fact a complex, system-of-systems. The traditional approach to EVA system design optimizes each individual component, and may introduce inefficiencies into the system, generate logistics and supply management problems, and create hardware legacies that are hard to change and upgrade. We propose an integrated systems approach for advanced EVA system design that seeks to optimize the overall system, rather than just the individual pieces of hardware. The integrated systems approach also designs for uncertainty by anticipating change. By considering the complete system and allowing for change, the integrated systems approach incorporates both systems-of-systems thinking and spiral development. We examine the development of the Shuttle spacesuit and illustrate the challenges designers faced in adapting the suit to changing requirements. We conclude that due to the uncertain nature of exploration-class EVA, a system designed with the integrated systems approach offers significant advantages over the traditional design approach.