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MIT’s 2004 spring class in Space Systems Design investigated the design of extensible space system architectures. A central difficulty in this task was the shear complexity of the problem, and the lack of an established methodology to design system architectures.

An important result of the investigations was thus the methods developed to approach the problem, and the process by which “sustainability” could become central to design decisions. The end result was an iterative and holistic approach to the problem, which will hopefully inform future space systems architecture projects.

It should be stressed that not every aspect of the process described was completed rigorously during the semester. Rather, the process represents a way to integrate the lessons learned and eventually create a systematic architectural design. Of course every element of this process did not proceed in clear and neat steps. Most of the steps were iterative within themselves, and individual elements were re-worked as

The underlying goal of the design process was to develop an integrated strategy that could quantify how the system reacted to changes in the environment. Rather than

create a point design to accomplish a Moon or Mars expedition, the class wanted to demonstrate that various scenarios could be anticipated and addressed during conceptual design and, as importantly, that the elements designed to address these scenarios (which would likely make the system sub-optimal from a point-design perspective) could be justified quantitatively. A strategy includes various scales of Moon and Mars missions, robotic scout missions, and considers the program changes such as budget cuts and regulatory constraints.

Figure 7 illustrates the five step process arrived at to create the strategy. An important goal was the establishment of common operations and across manned Moon, Mars and potentially asteroid missions, as well as through stages of missions at each body.

Common elements defined baseline architecture forms and operations, from which options could be created to address specific missions and changing scenarios.

The first three steps in the process identify common forms and functions needed to explore the Moon, Mars and other destinations. Two teams conceived of staged Moon and Mars missions, and created matrices with functional requirements for each stage.

With these functional requirements, a simple Venn diagram captures the relationship of requirements between the Moon and Mars. An interesting feature of this part of the process involves the ability to identify how formal elements can be extracted from functional requirements based on commonality between Moon and Mars needs at

various levels. “Options” can be created to supplement the core needs, based on requirements outside of the intersection of the circles.

Functional Commonality Mapping thus revises the forms created to enable various Missions. The two teams must then return to the mission storylines and establish how and whether mission objectives can still be met with the revised forms, and alter staged missions accordingly. This iterative process can continue until a satisfactory level of refinement is achieved.

It was found that this iterative part of the process reveals key trades that need to be made with respect to commonality and architecture operations. Based on our designs, trades on issues such lander design, rover design, aerobraking capability, and operational capability processes such as the use of the Earth-Moon Lagrangian points, could not be solved by commonality mapping alone. The next step of the process is thus to evaluate the key trades revealed by the first three steps of the process.

In order to create a flexible strategy, however, it was important to evaluate these trades with consideration for the value of flexibility and robustness, not just optimality. Tool such as real-options, multi-attribute utility theory, and decision analysis, can be used to carry out the trades while preserving system flexibility, thus creating a rigorous development strategy and architecture.

Chapter 6 addresses how these tools can be used to evaluate strategic and technical options. The strategy includes staged deployment of Moon and Mars missions, with development options forming branches from the baseline mission. Ideally the aspects of the system designed early in the strategy will minimize the need for redesign if new directions in the strategy are taken.

As noted, the full strategy was not generated during this design course. Instead, various aspects of the process were addressed and tools were conceived to facilitate their design in later studies.

3. Knowledge Delivery: The Core of Exploration