The Aerospace Corporation s Concept Design Center

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1 The Aerospace Corporation s Concept Design Center Joseph A. Aguilar Andrew B. Dawdy Glenn W. Law 2350 East El Segundo Boulevard El Segundo, CA ABSTRACT The Concept Design Center (CDC) developed by The Aerospace Corporation has enhanced support to its customers by providing a process for bringing together the conceptual design capabilities and experts throughout The Aerospace Corporation. The members meet as a group on an as-needed basis in a computer laboratory to create and evaluate conceptual designs in a synergistic and concurrent manner. The CDC consists of a number of teams, each of which focuses on a different segment of the mission. This paper will focus on the general characteristics of the CDC and on the Space Segment Team (SST) whose primary function is the conceptual design of the spacecraft. INTRODUCTION CONCURRENT ENGINEERING METHODOLOGY The Concurrent Engineering Methodology (CEM) is a collection of techniques, lessons learned, rules of thumb, algorithms, and relationships that have been developed for conceptual space system design. When applied, the CEM makes it possible to rapidly generate processes and tools that are customized to meet the specific requirements of a study. CEM based tools provide end-to-end linking of design parameters, iterative calculation capability, and connectivity to cost estimating relationships (CER) which make them ideal for conceptual design, technology insertion, and trade space exploration studies. These processes provide the capability to better understand the design, performance and cost impacts of the requirements trades necessary during the developmental phase of a program. EXPERIENCE The process and the tools developed with the CEM have been successfully applied to several programs, including: Space-based Infrared System (SBIRS) National Polar-orbiting Operational Environmental Satellite System (NPOESS) Integrated Space Technology Demonstration (ISTD) Operational Effectiveness & Cost- Comparison Study (OECS) Reusable Spacelift Concepts Study (RSCS) Each of these efforts successfully integrated design, evaluation, and cost estimation in a concurrent manner that provided unprecedented detail, trade capability, and cycle times. Based on the experience that The Aerospace Corporation has in implementing concurrent engineering processes, the Jet Propulsion Laboratory (JPL) contracted The Aerospace Corporation to develop CEM processes and tools for their Project Design Center (PDC). The PDC is a facility where proposal and preproject teams can assemble and work in a focused environment utilizing models developed by the PDC. The PDC s main user is The Advanced Projects Design Team, commonly known as Team-X, which is responsible for defining initial concepts for future JPL planetary exploration missions using faster, better, cheaper philosophies. Team-X wanted a process in which all of the major elements in a project (e.g. spacecraft, cost, operations, etc.) could be designed concurrently. The Aerospace Corporation, under contract to JPL, developed the Distributed CEM architecture for Team-X to use for its conceptual design and analysis work. The PDC concept has proven to be an extremely valuable resource at JPL. The Team X/Aerospace team was one of nine JPL process improvement teams to receive the 1997 TQM Redesign Award Medallion which recognizes process redesign to produce superior products and services. In addition to the TQM Redesign Award Medallion, Team X was also presented a NASA Group Achievement Award. NASA Group Achievement Awards are one of the highest classes of awards available to JPL employees and indicate that recognition from the highest echelons of NASA is being given to Team X s work. The publicity generated from these CEM and PDC efforts has increased interest in concurrent engineering techniques. Goddard Space Flight Center (GSFC) had approached The Aerospace Corporation and JPL s PDC to develop a similar

2 capability at their facilities. They eventually developed their own facility called the Integrated Mission Design Center (IMDC). TRW has built a conceptual design facility called the Integrated Concept Development Facility (ICDF), after having examined the CDC and PDC. The California Institute of Technology received assistance from JPL and The Aerospace Corporation in developing a CEM process for their engineering curriculum. Figure 1 shows some of the entities who are currently using the CEM developed by The Aerospace Corporation. Figure 2 Each row indicates the possible scope, or breadth, of the analysis. The first CDC team developed was the Space Segment Team (SST). It focuses on the lowest level in the diagram, that of conceptual space segment design. Conceptual design is defined here as the first attempt to define detailed spacecraft subsystem characteristics, performance, and cost. Other CDC teams that address the different levels of analysis presented in the diagram are also in development. Figure 1 The success of these techniques at JPL led The Aerospace Corporation to invest in the Concept Design Center (CDC) as a way to better coordinate these types of design and analysis activities within its Engineering and Technology Group. HISTORY OF CONCEPTUAL DESIGN WHAT IS CONCEPTUAL DESIGN? During the conceptual development phase of a program, there are many levels of analysis necessary to define the requirements leading to a successful procurement. At each, the proper degree of breadth is necessary to ensure that a systems understanding is maintained, while the appropriate depth is achieved to answer the desired questions without burdening the analysis with unnecessary detail and complexity. An analysis that would simultaneously consider Air and Space mission integration and detailed spacecraft thermal subsystem design would be inadvisable. Figure 2 provides examples of a hierarchy of different levels of analysis that could be performed during concept development. SEQUENTIAL DESIGN PROCESSES Development of the CDC SST has followed an evolutionary process at The Aerospace Corporation. Prior to 1993, conceptual design was primarily a sequential process driven by the customer s schedule. There were some disadvantages with the sequential design process. Team creation was informal, the right specialists were often not chosen, and results generated were not as accurate as they could have been. Since one person often could not start until the results from another person were completed, studies could not be performed rapidly. Opportunities for iteration were very limited as the time required to perform the first iteration left little time for subsequent iterations. To improve the design process the CEM was developed. CENTRALIZED DESIGN PROCESSES Initial development of the CEM in 1993 led to the generation of many centralized processes. With this design methodology a systems engineer gathers contributing information from the other engineers and assembles the data into a single spreadsheet based tool. This spreadsheet can then be operated by the system engineer to quickly design a spacecraft and perform trades. Several key benefits are gained through the Centralized Design process. Studies could now be accomplished in hours or days, instead of weeks or months. As all of the spacecraft systems were linked together, a change made to one subsystem affects others instantaneously. Trade

3 space exploration was greatly enhanced and specific technologies could be inserted and removed quickly to see their impact on the overall system. There are, however, shortcomings to the Centralized Design process. Without the presence of a subsystem expert, there is an inherent danger of misusing the tool. Though the systems engineer has familiarity with all of the subsystems, only a subsystem expert would know if a particular design parameter exceeded its limits. This process also takes away the sense of ownership that the subsystems have with regard to their models. (Experts may feel that the systems engineers want only their models and rules-of-thumb and once they get them, they will be excluded from the design process.) With the centralized tool limited to simple models, algorithms, and rules-of-thumb, much of the engineering detail is lost compared to the Sequential Design process. DISTRIBUTED DESIGN PROCESSES To overcome these shortcomings, the Distributed Design CEM was developed in early 1997 and was implemented in the Concept Design Center. This process brings all of the contributing design engineers together in a single location. Each engineer has a subsystem model that is linked to all of the other subsystem models. If one engineer changes the design parameters of a subsystem, the effect will be immediately seen by the others. A substantial number of benefits have been gained with this approach. First, bringing contributing design engineers directly back into the process has allowed the incorporation of more detailed models. Second, when one engineer changes a subsystem design, the impacts of that change are immediately felt by the other subsystems. Third, the models remain in the hands of the expert subsystem engineers. This encourages continued interest and participation by all team members, and engenders a sense of ownership that leads to expansion of the tools capability for uses outside the team environment. Fourth, and probably most important, the customer is closely involved in the entire process. The customers presence allows the subsystem engineers to ask questions as they naturally occur during the process. Assumptions can be modified based on the customer s feedback and major changes can be accommodated in real time. This provides the customer with more control over the direction of the design and allows them to make immediate changes based on intermediate design results. THE CONCEPT DESIGN CENTER WHAT IS THE CDC The CDC is made up of three key elements. First, it is a team that draws on the breadth of The Aerospace Corporation s engineering expertise. Second, it is a facility where the customer can interact efficiently with the team of experts. Third, it is a process for applying innovative design tools to produce quality results quickly. All of these elements yield a product that has better detail and consistency, is generated in a shorter amount of time, and is cheaper, by more efficient use of resources. The CDC SST brings together not only the spacecraft subsystem experts, but also other engineering experts that are not normally brought in during the conceptual design process, such as the software, ground, and cost experts. CDC SST TEAM The CDC SST team includes participants from across all engineering departments. Each CDC SST team member is chosen to represent the expertise and capability of their department. As department representatives, they are given the responsibility of developing the models for use in the CDC SST environment and participating in the design activities. They are also responsible for selecting and training additional representatives from their departments in order to ensure a continuing level of broad-based support for future CDC SST activities. The functional areas at The Aerospace Corporation participating in CDC SST development activities include: Propulsion Attitude Determination and Control Communications Command and Data Handling Electrical Power Thermal Structures Cost/Risk Ground Segment Payload Processing Astrodynamics Software Radar Payloads Electro-optical Payloads Systems Engineering The entire effort is coordinated by a systems engineer who is responsible for organizing the study in cooperation with the customer and for planning and conducting group activities.

4 CDC FACILITY Having all of the design engineers and the customer located in one room during the design process has many benefits. All of the subsystem engineers are seated around a conference table along with the customer s team to allow for an open exchange of ideas and information during the study. The subsystems are arranged so that those that have the more frequent interactions are located next to each other, allowing face-to-face interactions during the design process. Overhead projectors can display any of the computer monitors on a large screen to focus the group s attention to a specific subject. (Figure 3 shows a planned layout of the CDC.) Figure 3 With the customer present in the room, the team members are able to ask questions and get immediate answers that affect the design of the spacecraft. If the customer does not have the answers, he can hear the assumptions that will be made. Likewise, the customer can ask questions of the team to understand why the spacecraft is being designed the way it is. If the customer does not like the direction that the design is taking, he may immediately redirect it, thus avoiding unnecessary expenditure of design resources and time. THE CDC PROCESS The processes developed for the CDC enable the design experts to prepare their contributions simultaneously and in the presence of the other team members and the customer. This face-to-face interaction encourages involvement by all of the participants, including the customers. To facilitate interaction, the CDC utilizes personal computers and spreadsheet software to manage the sharing of information among the experts and to ensure consistency across the entire system design. A typical CDC study has three stages. The first stage consists of design study planning, the second comprises the CDC session or sessions, and the last involves the post-cdc session wrap-up activities. For study planning, the customer first meets with a CDC systems engineer to determine the scope of the study and generate a draft statement of work. The draft statement of work spells out the mission statement, study goals, trade space, estimated levelof-effort, and schedule. Each CDC team member has an opportunity to contribute to the draft statement of work and to begin to formulate questions about the mission. The next step is a CDC payload session meeting which includes the customer, CDC payload specialist, CDC systems engineer, and any other necessary team members that require advanced information about the mission. After this meeting any adjustment or development that needs to be made to the CDC models to accommodate the study will be made. Generally, this stage occurs over a 1 to 4 week period before the CDC session. The actual CDC session is where the entire team assembles with the customer to design the space segment. The team will be introduced to the customer and the mission. The customer will describe to the team the mission goals, needs, wants, and desires, and will then answer questions that arise during the session. The concurrent design process usually lasts several hours and design course corrections can be made along the way. Trades can be made that weren t planned or anticipated. As many follow-up sessions can be scheduled as are needed, but most studies to date have been completed in 2 to 3 sessions of 3 hours each. The post-cdc session activity typically consist of documenting the study for the customer. A report containing documentation from all of the subsystems is a standard output for each study. Each subsystem provides a subsystem/component level description of its conceptual design. Each subsystem representative documents his or her assumptions that were made during the study along with a detailed description of the designs. Additionally, comments on the risk areas and technical considerations of the subsystem will be noted. The cost section of the report provides not only a life cycle cost for the entire system, but also a cost-risk analysis. As the tools for each study are archived electronically, future studies can be conducted after the initial study in a timely manner. This allows the customer to examine other possible design configurations after having time to understand the previous ones. A subset of the CDC SST may be used to provide on-going support. For example, if trades in the power subsystem are required, the power subsystem expert can work with the customer outside of the CDC SST environment.

5 TOOLS Flexibility, ease of use, and connectivity were key factors in developing the tools for the CDC. Spreadsheet software, specifically Microsoft Excel, was selected as the environment for nearly all of the tools. The software is readily available, and most users are familiar with spreadsheets as opposed to programming languages such as C++, FORTRAN, or PASCAL. Modern spreadsheets are easy to use, very powerful, and very flexible. Flexibility is their primary strength in an environment where the tools need to be customized for each different spacecraft they are used to design. A designer can easily add a new formulas, spacecraft components, or design characteristics. This would not be the case if a more complex programming language was selected. The spreadsheets that the design engineers use serve as tools to assist them in the design process, much like an instrument assists a musician. The musician is the one who is determining what notes, rhythm, and tempo are being sounded. The instrument is just the mechanism that the musician uses to present his music. In a similar fashion, the spreadsheet-based design tools facilitate the design process by allowing the design specialists to contribute their experience, expertise, and creativity in a consistent and flexible manner. In fact, the CDC process can be compared to an orchestra where the systems engineer conducts all of the engineers who relate their talents through the spreadsheets. All of the subsystems are linked to each other through a local fileserver. Real-time verbal interaction among the engineers is a natural occurrence in this environment. Consequently, subsystem interactions that are not captured electronically are identified through real-time discussion and then documented. Figure 4 shows just a fraction of the interactions among the CDC SST subsystems. Having all of the subsystem representatives present with their design models allows for ideas and problems to be explored and solved immediately. This is a key factor that allows the design process to move quickly. Figure 4

6 MODELING METHODS Each of the subsystems within the CDC SST is sized using one or more of the following methods. The selection of components from a database is a common method. As an example, the attitude determination and control subsystem model employs a number of databases where different star trackers, reaction wheels, and sun sensors may be picked based on performance, mass, and power characteristics. Several subsystems use analytical relationships as a modeling method. For instance, the power subsystem will size the batteries based on an estimate of the performance for a specific technology captured as a W-hr/kg parameter. Some subsystems, such as thermal, will use an historical approximation, generating new design estimates based on past spacecraft properties (e.g. thermal mass fraction). The last method employs using detailed off-line simulations. The astrodynamics spreadsheet model relies on inputs generated from LIFETIME software to help determine the necessary V for the mission. ACTIVITIES A number of different space system design activities are well suited for the CDC SST. The first is the design of new space missions. The CDC SST can design a new spacecraft for a customer supplied payload design and conduct parametric trade studies to surface the key design and cost drivers. The CDC SST also has the capability of developing conceptual payload designs if a customer only has a notional payload concept. Block changes to existing systems that examine enhancements to existing spacecraft, and trade studies involving the proposed improvements can also be performed. Examining the system level impacts of advanced technology insertion is the third type of design activity that can be performed. The customer can see the effects of advanced technology in any area of the spacecraft on overall mass, power, cost, etc. This allows the customer to identify those key technologies which are necessary for a mission to be accomplished. Another activity that can be performed by the CDC SST is independent evaluation. A spacecraft design proposed outside of the CDC can be modeled in the CDC environment to provide each of the subsystem experts a structured and in-depth understanding of the proposed system. This allows for better evaluation of design consistency and the surfacing of potential risk issues. The CDC processes provide a powerful approach to solving a wide array of tasks involving conceptual spacecraft designs. OBSERVATIONS MEASURING CDC EFFECTIVENESS There are several metrics that can be used to validate the fact that the CDC produces results faster, better, and cheaper. The time it takes to produce a conceptual design for a spacecraft is much shorter than that experienced in past studies. Studies to produce a similar level of detail have historically taken several months to complete, and have involved an equivalent number of participants. By reducing the amount of time required, the resource expenditure can be reduced proportionally, Overall reductions of 50 to 75% have been observed. Alternately, since many activities can only be performed with limited resources and time, the CDC is capable of providing greatly enhanced detail for an equivalent resource expenditure. BENEFITS Several benefits for individual CDC SST members as well as the whole team have been observed. First, subsystem members are expected to be knowledgeable in all of the aspects of their discipline. If a customer is interested in a mission where new technology is required, the subsystems engineers will have an opportunity during the study to enhance their expertise in this area. Second, all of the subsystems engineers are gaining enhanced system level awareness. Previously a subsystem engineer would optimize their system without awareness of the impacts it would have on other spacecraft subsystems. Now the subsystem engineers immediately see how their design affects others. This leads to a new way of thinking in designing a subsystem that is optimal for the entire spacecraft. OTHER CDC TEAMS AND THEIR INTERACTIONS As was mentioned in the abstract, the CDC consists of a number of teams at The Aerospace Corporation. Figure 5 shows these teams. Figure 5

7 The Space Segment Team is the most developed of the CDC teams. Eleven design studies have been performed as of April The System Architecture Team focuses on architectural options for space systems. Constellation, performance, communications architecture, replenishment scheme, and utility are designed or evaluated for each architectural option. Several other teams are currently in development. The Ground Segment team will examine ground architecture trades involving facilities, personnel, communications, ground processing, and software. Several payload design teams are being formed to balance and trade payload subsystems in the electro-optical and communications arenas. CONCLUSION The Concept Design Center has proven to be a successful mix of concurrent design methodology and spreadsheet-based engineering design tools. Studies that previously required months to complete now can be completed in a matter of weeks. Having the subsystem experts directly involved in the conceptual design process provides for greater detail and credibility in the final product. All of these factors make the CDC very effective in performing system-level trades to determine the technical and fiscal impact of any design, quickly, thoroughly, and cost-effectively. Principal Investigator, a primary developer, and a key systems engineer for the CDC. He has developed new tools and techniques for design and evaluation of spacecraft, theater missile defense interceptors and ground systems. He has a Bachelor and Master of Science in Aeronautical and Astronautical Engineering from the University of Washington. Glenn W. Law is an Engineering Specialist in the VCD. He is actively involved in the development of spacecraft and launch vehicle conceptual design algorithms and models. He has worked on the development of the distributed CEM for the PDC at JPL, and has applied this process to the development of the CDC at The Aerospace Corporation. He has a Bachelor of Science in Aerospace Engineering from the University of Michigan and a Master of Science in Aeronautics and Astronautics from MIT. REFERENCES Jet Propulsion Laboratory Project Design Center, Goddard Space Flight Center Integrated Mission Design Center, University Consortium for Continuing Education BIOGRAPHY Joseph A. Aguilar is a Senior Member of the Technical Staff in the Vehicle Concepts Department (VCD). He has participated in many conceptual design activities as a principal and assisting systems engineer. He worked on establishing the distributed CEM for the JPL. The success of that venture led to the creation of the CDC with his participation. He received his Bachelor of Science in Aeronautical Engineering from the California Polytechnic State University at San Luis Obispo and his Master of Science in Industrial and Systems Engineering from the University of Southern California. Andrew B. Dawdy is an Engineering Specialist in the VCD with experience in spacecraft design and systems engineering. He has designed conceptual spacecraft to meet national defense needs. He is the