3.1 Background
In order to measure the capability of technologies and vehicle concepts to support or implement the preceding operations concept, some criteria must be provided against which the technologies and vehicle concepts may be relatively measured. The measurable criteria that follow were derived from similar criteria developed by the Space Propulsion Synergy Group (SPSG). A strategic, top-down approach was used. Beginning with the National Space Policy, a series of "Attributes" were determined. These were qualitative descriptions of "What" needed to be addressed in order to respond to the Space Policy.
Sub-attributes were also determined. For example, affordability has recurring and non-recurring costs as sub-attributes. The sub-attributes were weighted, prioritized by the need to improve that sub-attribute.
Because the qualitative attributes do not say "HOW", "Measurable Quality Characteristics" were determined.
For example, a couple of measurable criteria related to the attribute "Dependability" are "Number of potential leakage sources" and "Number of different fluids in a system."
The measurable criteria were then scored using a QFD process. For example:
In this way, the criteria "most related" to the attributes were determined and could be listed in prioritized order. The criteria end up weighted according to score.
The measurable criteria can then be used to evaluate efforts toward improving the attributes. The technology, for example, that scores well against all the criteria has the greatest likelihood of improving the higher level strategic attribute, because the criteria are so related to the higher level attributes.
A comprehensive discussion of launch vehicle attributes and systems consensus from nationwide contributors to the Space Propulsion Synergy Planning Support Working Panel is presented in Appendix-A. Scope of the input encompasses far more than propulsion.
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3.3 The Operability Criteria - Listed
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Edgar Zapata, NASA Kennedy Space Center
Shuttle Process Engineering Directorate, Fluid Systems Division