Node_3_Trade_Study - NODE 3 LAUNCH-TO-ACTIVATION TRADE...

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NODE 3 LAUNCH-TO-ACTIVATION TRADE STUDY Scott Hutchins, The University of Alabama in Huntsville Paul J. Componation, The University of Alabama in Huntsville Abstract. A late change in International Space Station (ISS) operational constraints created a serious threat to the successful completion of a major space station assembly activity. This report demonstrates the methodology and results of a two-phase trade study evaluating several solution alternatives to this problem. In Phase 1, a trade study team developed a set of objective and subjective evaluation criteria and evaluated four alternatives using a Brown-Gibson decision model. The Phase 1 results indicated a second iteration focusing on the most important subjective criterion would be useful to obtain additional insight among the alternatives. Three remaining alternatives were reevaluated a Phase 2 effort and scored using the Rank Reciprocal method. The Phase 2 results were incorporated in a second iteration of the Brown-Gibson model, producing new insights and a clearer solution alternative recommendation to ISS decision-makers. This exercise provides a methodology and model for future trade studies. Key Words: Trade Study Methodology, Brown- Gibson, Rank-reciprocal Introduction. An actual Node 3 trade study for the issue described in this paper was initiated in late 2004, but soon placed on hold in the spring of 2005 due to ISS and Node 3 schedule delays related to the Space Shuttle Columbia accident. This paper uses the tabled Node 3 LTA assessment effort as a starting point to describe a logical, defendable trade process methodology. The results provide a realistic, requisite decision model representing the guidance and insight needed for ISS managers to decide a course of action on this or similar issues. The background, context, and technical constraints described are based on fact. The evaluation criteria and alternative evaluation score values attributed to the “LTA Team” are actually creations and estimates of the author based on available Node 3 information and technical data. Background. Node 3 is a major, human–rated element of the International Space Station (ISS). The cylindrically shaped, pressurized module provides additional docking ports for the ISS and also houses key avionics and life support systems. Node 3 is delivered to the ISS via the Space Shuttle with a scheduled launch in 2009. Node 3 has a specific operational procedure for its delivery and installation called the “Launch-to- Activation” (LTA) sequence: 1. Node 3 is launched in the Shuttle cargo bay. 2. Shuttle rendezvous and docks with ISS on flight day 3. Node 3 has LTA electrical connectors that allow Shuttle to provide power to Node 3 shell heaters during this flight phase. These heaters regulate the Node 3 structure temperature to prevent it from violating its thermal limits and “freezing” in the space environment. Other Node 3 electrical systems are not connected or active during this period. 3.
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This note was uploaded on 11/22/2009 for the course ISE 627 taught by Professor Componation during the Fall '08 term at University of Alabama - Huntsville.

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Node_3_Trade_Study - NODE 3 LAUNCH-TO-ACTIVATION TRADE...

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