The Concurrent Engineering Process 32

The primary goal of the CE process is to ensure that the study meets the customer requirements in an effective manner within the time and cost allocated. The process must make the best and most efficient use of the experts and their tools in creating a design. Careful planning is crucial in achieving these goals.

It is challenging to develop a process that is consistent and repeatable, but is also flexible enough to allow for changes needed during a CE session. As the members of a CE team typically vary across studies, it is important to have consistent processes in place to reduce the variation in the study output. It is not required that the process be the same across concurrent teams at different Centers, but it is necessary to be able to define the interfaces between the different teams during distributed collaborative design sessions, similar to interface agreements between subsystems in traditional projects.

A consistent step-by-step process is essential to reach a conclusion and finish a design in an allotted amount of time. The individual substeps differ in response to the needs and the makeup of the individual concurrent teams. However, the main steps are applicable to all concurrent teams. The following outline as well as the steps shown in Figure 7.2-2 capture, at the very top level, a representative process for a design sequence from the germ of an idea to the final

products. The details of each of the steps may vary between CE teams, but the main steps remain the same. The amount of time taken to complete a particular step or study can vary from days to weeks to months, depending on the level of detail of the study or the complexity of the mission.

7.2.4.2.1 Establishing the Scope

In order to make the most of the design team, it is essential to start the study with a solid problem definition. The team lead/study facilitator meets with the customer to understand the problem to be solved and develop the requirements for the design session. The team lead and the customer agree on the top level requirements, figures of merit, goals of the design study, required

products, study schedule, and any other engineering or study constraints. Each team has different products to offer. The products typically range from annotated presentations, CAD models, and spreadsheet summaries to a full text report. The level of effort, time to completion, and cost to the customer vary as a function of the scope and depth of detail of the desired analyses and products.

This is where the study planning and preparation activities are conducted, the stakeholder- provided data and the objectives and activity plan are reviewed, and the scope of the activity is finalized. A discussion is held of what activities need to be done by each of the stakeholders and the design teams. For example, for planning a mission design study, the customer identifies the mission objectives by defining the measurement objectives and the instrument specifications, as applicable, and identifying the top-level requirements. Due to the relatively short duration of the CE study, the preliminary work, which is required to enable the CE study but may take a long time, is performed by a subset of the CE engineering team before the start of the actual study. Typical long duration work items include flight dynamics analyses; entry, descent, and landing profiles; launch vehicle performance trajectory analyses; thrust and navigation analyses; and complex optical analyses. Those tasks must be identified in the planning meetings to enable the rapid flow of true CE in the study execution phase. The level of analysis in this phase is a

function of many factors, including the level of maturity of the incoming design, the stated goals and objectives of the engineering activity, supporting engineer availabilities, and scheduling.

7.2.4.2.2 Pre-Study Background Work

The amount of background work done prior to the CE session varies by team and by the type of mission being studied. In preparation for the study, team members typically review similar previous missions and perform all necessary early work, especially on the long lead items mentioned above. They may also discuss specific aspects of the mission with the customer to gain a better understanding of the higher level mission requirements and constraints.

7.2.4.2.3 Full-Team Concurrent Design Sessions

A design session is the physical or virtual meeting during which the members of the concurrent team gather to perform the analyses and information exchanges necessary to design a system collectively. The activities and outputs of the design session depend on the type of study being conducted and the level of conceptual maturity of the mission. Different teams develop their designs on different timescales, which are also a function of the amount of work done in real- time concurrent sessions versus independent work performed outside the CE sessions. The study products may vary from high-level mission feasibility studies aiming to determine if a concept is viable, to detailed convergent point designs, some based on high-level, even parametric

subsystem concepts, while others include very detailed system and subsystem designs as well as cost and schedule estimates based on detailed concept of operations and master equipment lists. During the design session, the concurrent design team works with the customer team to address

the desired level of fidelity. Ideally, designs (or a set of architectures for trade studies) are iterated either until full convergence is achieved or until they are determined to be infeasible. Convergence is usually driven by a combination of key parameters and constraints, which typically include, as a minimum, mass, power, cost, schedule, data, and launch vehicle constraints.

A typical activity or study begins with the customer presentation of the overall mission concept and instrument concepts, as applicable, to the entire team. Additional information provided by the customer / stakeholders includes the team objectives; the science and technology goals; the initial requirements for payload, spacecraft, and mission design; the task breakdown between providers of parts or functions; top challenges and concerns; and the approximate mission timeline. This information is often provided electronically in a format accessible to the

engineering team, and is presented by the customer / stakeholder representatives at a high level. During this presentation, each of the discipline engineers focuses on the part of the overall design that is relevant to his or her subsystem. The systems engineer enters the high-level system

requirements into the master systems spreadsheets or master database that is used throughout the CE process to track and document the evolution of the design. The data sources can be projected on large overhead displays as well as the CE team members’ individual screens to keep the entire team synchronized and the customer/stakeholders aware of the latest developments.

The engineering work is performed iteratively, with the team lead and systems engineer playing key roles to lead the process. Thus, issues are quickly identified, so consensus on tradeoff decisions and requirements redefinition can be achieved while maintaining momentum. The customer team actively participates in the collaborative process (e.g., trade studies, requirements relaxation, clarifying priorities), contributing to the rapid development of an acceptable product. Each discipline maintains a set of key parameters used to describe its design. Because of the interdependencies among the various subsystems, each discipline engineer needs to know the value of certain parameters describing other subsystems. These parameters are shared through the local CE information infrastructure network. Often, there are conflicting or competing objectives for various disciplines and tradeoffs must be conducted overarching several

subsystems. Such tradeoffs are typically defined and led by the systems engineer. The physical layout of the seating arrangement is designed such that subsystems which need to interact extensively with each other in tradeoffs and other matters are clustered in close physical proximity to facilitate communication.

Sidebars and Tag-ups

Two key aspects of a design session are the sidebar and the tag-up. These are critical in maintaining the flow of information and situational awareness across all team members. At times, more in depth discussions are needed than what is possible in the main CE room. A sidebar is the means of accomplishing that. A sidebar is a break-out session in which only a subset of the team participates to discuss a particular issue related to the study. When a sidebar is initiated, the participants physically move into a side room set aside for that purpose and conduct their discussions there. After the conclusion of the sidebar, its participants usually report back on the outcome of their discussions to the whole team at the next general session.

A tag-up is an all-team activity that is used to keep the entire team, as well as the customers and stakeholders, synchronized and up to date. Tag-ups are typically held once or twice per day in the main CE room during study sessions. At the tag-up, all team members focus on the front of the room, and only a single discussion is allowed. Team member take turns round-robin style to present the status of their portion of the design and briefly discuss any issues associated with it that are of interest to the whole team. Tag-ups are the primary means in the study to maintain overall situational awareness. Tag-ups also force subsystems to adopt a systems perspective relative to their designs. Tag-ups are implemented differently across various CE teams, but their purpose is the same for all.

7.2.4.2.4 Post-Session Documentation and Presentations

While there is a large variation in the post-design session activities between teams, all teams develop a product that documents the final design using a consistent template and also present that design to the customer. Products may include PowerPoint slides, text documents,

configuration drawings, trajectory files, various analysis results, and computer models, delivered both in presentations and in appropriate cyber formats.

Figure 7.2-2 Concurrent Engineering Process

Critical Issue: Process integration with joint studies

A key process issue arises when conducting a joint study between multiple CE teams because each team has somewhat different core capabilities and associated processes and operates on different timescales. It is essential for each team to have a good understanding of what the capabilities and processes are for each of the other teams as collaboration between teams becomes a common occurrence. This also means that standardized products and a consistent process are necessary within a team to be able to create the proper interfaces with other teams. Coordinating the different process timescales between teams is a challenge. For example, if one team does most of its design work in real time, and another primarily works out of session, collaboration between the two will be difficult. Changes will need to be made to the processes of the teams to ensure compatibility during distributed design sessions. In order to identify the process changes necessary to enable collaborative design, an understanding of the current processes and capabilities of the teams is needed.