NASA Scientific and Technical Aerospace Reports

defines the directions of maximum and minimum cost change. A simplified approximation of the PRICE H(TM)
production-production cost is used to generate this set of differential equations over [mass, complexity] space. The equations
are solved in closed form to obtain the one dimensional design-to-cost trade and design-for-cost spaces. Preliminary results
indicate that cost is relatively insensitive to changes in mass and that the reduction of complexity, both in the manufacturing
process and of the spacecraft, is dominant in reducing cost.
Author
Cost Analysis; Cost Effectiveness; Cost Estimates; Cost Reduction; Manifolds (Mathematics); Satellite Design
20040121075 NASA Langley Research Center, Hampton, VA, USA
Using Dynamic Sensitivity Analysis to Assess Testability
Voas, Jeffrey; Morell, Larry; Miller, Keith; [1990]; 25 pp.; In English; Original contains black and white illustrations
Contract(s)/Grant(s): NAG1-824; NAG1-884; No Copyright; Avail: CASI; A03, Hardcopy
This paper discusses sensitivity analysis and its relationship to random black box testing. Sensitivity analysis estimates
the impact that a programming fault at a particular location would have on the program’s input/output behavior. Locations that
are relatively \"insensitive’ to faults can render random black box testing unlikely to uncover programming faults.
Therefore, sensitivity analysis gives new insight when interpreting random black box testing results. Although sensitivity
analysis is computationally intensive, it requires no oracle and no human intervention.
Author
Electronic Equipment; Sensitivity Analysis; Failure
20040121109 North Carolina Agricultural and Technical State Univ., Greensboro, NC, USA
Integrated Human Factors Toolkit
Ntuen, Celestine A.; 2003 Research Reports: NASA/ASEE Fellowship Program; December 15, 2003, pp. P-1 - P-9; In
English; See also 20040121096; No Copyright; Avail: CASI; A02, Hardcopy
This study is focused on developing an assessment methodology for use in selecting appropriate human factors tools to
support task processing at Kennedy Space Center. Processes at ELV, Shuttle, and Station are used to validate the need for
human factors tool integration. The problem is analyzed fiom three complementary theoretical backgrounds: process
abstraction, workflow analysis, and requirement analysis. The approach presented departs fiom the traditional workflow
analysis in the sense that process absbaction inquiry and ontology are used to incrementally compile process information along
the continua of abstraction hierarchy. Also, unlike the classical task analysis that is often advocated for process modeling, we
use work domain analysis because it is robust to capture unanticipated events in time and space, typically, along the boundaries
of task processing. It is argued that by combining process abstradion inquiry and ontology, the building blocks for task
processes can be developed to cuntain dense information required to mimics the realism of task behaviors, including, for
example, actor-activity interactions, task state predictions, and the tools required to perform the tasks.
Author
Decision Making; Mathematical Models
20040121113
Development of Algorithms for Control of Humidity in Plant Growth Chambers
Costello, Thomas A.; 2003 Research Reports: NASA/ASEE Fellowship Program; December 15, 2003, pp. D-1 - D-13; In
English; See also 20040121096; No Copyright; Avail: CASI; A03, Hardcopy
Algorithms were developed to control humidity in plant growth chambers used for research on bioregenerative life
support at Kennedy Space Center. The algorithms used the computed water vapor pressure (based on measured air temperature
and relative humidity) as the process variable, with time-proportioned outputs to operate the humidifier and de-humidifier.
Algorithms were based upon proportional-integral-differential (PID) and Fuzzy Logic schemes and were implemented using
I/O Control software (OPTO-22) to define and download the control logic to an autonomous programmable logic controller
(PLC, ultimate ethernet brain and assorted input-output modules, OPTO-22), which performed the monitoring and control
logic processing, as well the physical control of the devices that effected the targeted environment in the chamber. During
limited testing, the PLC’s successfully implemented the intended control schemes and attained a control resolution for
humidity of less than 1%. The algorithms have potential to be used not only with autonomous PLC’s but could also be
implemented within network-based supervisory control programs. This report documents unique control features that were
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