The Multi-role Capsule as an Example of Function Based Requirement Generation
- Paper number
IAC-06-D3.3.04
- Author
Mr. Mark Hempsell, University of Bristol, United Kingdom
- Year
2006
- Abstract
Past work has outlined a concept study for a Multi-role Capsule that explores the potential capability of a small personnel transport system. However, the process by which the objectives and requirements were arrived was not fully explained. It used an approach based on a function orientated requirement generation process (as opposed to a mission orientated process) and is presented here as a case study for this unconventional methodology. By consideration of the overall infrastructure as a system of systems the function of a small crew space transportation system was identified. It was found that the driver was for a minimum number of system developments leading to a multi-role approach. Thus the function based objective for the Multi-role Capsule concept study was “to be the most flexible and capable crew space transportation system in current circumstances.” From this functional objective key performance parameters can be derived such as crew size, maximum mission velocity and operational lifetime (both active and in-space storage). Unlike in a mission based requirement generation approach there are no absolute values for these parameters as in most cases, such as crew size and maximum mission velocity more is always better. However the constraints placed on the system by other infrastructure elements mean that many of these performance parameters compete for the same resources such as volume and mass. To further complicate the process these constraints are also “fuzzy” because of the range of choices and also because many of the interacting infrastructure elements are ill defined. Thus following a functional objective route leads to soft performance targets, and soft interfaces and constraints. To resolve this uncertainty the methodology then uses feasibility designs to explore what is technically and financially possible and to establish the hard requirements for the formal requirement specification for use in the subsequent development phases in the conventional way. The value of a system meeting these requirements can then be assessed through exploration of its utility by consideration of its performance in various mission scenarios. If it can undertake sufficient missions to justify its development then the project can proceed confident that the system is both feasible and has real utility. It is shown in the case of the Multi-role Capsule that this approach has produced a viable specification for a superior system than would have been produced under the more conventional mission based requirement generational methodologies.
- Abstract document
- Manuscript document
IAC-06-D3.3.04.pdf (🔒 authorized access only).
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