10.6 ORBITER MAINTENANCE DOWN PERIOD/ ORBITER MAJOR MODIFICATION

¶During the Orbiter Major Modification process, Orbiters are removed from service for inspections, maintenance, and modification. The process occurs every eight flights or three years.

¶Orbiter Major Modifications combine with Orbiter flows (preparation of the vehicle for its next mission) and include Orbiter Maintenance Down Periods (not every Orbiter Maintenance Down Period includes an Orbiter Major Modification). The primary differences between an Orbiter Major Modification and an Orbiter flow are the larger number of requirements and the greater degree of intrusiveness of a modification (a recent comparison showed 8,702 Orbiter Major Modification requirements versus 3,826 flow requirements).

¶Ten Orbiter Major Modifications have been performed to date, with an eleventh in progress. They have varied from 6 to 20 months. Because missions do not occur at the rate the Shuttle Program anticipated at its inception, it is endlessly challenged to meet numerous calendar-based requirements. These must be performed regardless of the lower flight rate, which contributes to extensive downtime. The Shuttle Program has explored the possibility of extending Orbiter Major Modification cycles to once every 12 flights or six years. This initiative runs counter to the industry norm of increasing the frequency of inspections as systems age, and should be carefully scrutinized, particularly in light of the high-performance Orbitersʼ demands.

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¶Orbiter Major Modifications underwent a significant change when they were relocated from the Boeing facility in Palmdale, California, (where the Orbiters had been manufactured) to Kennedy Space Center in September 2002. The major impetus for this change was budget shortages in Fiscal Years 2002 and 2003. The move capitalizes on many advantages at Kennedy, including lower labor and utility costs and more efficient use of existing overhead, while eliminating expensive, underused, and redundant capabilities at Palmdale. However, the move also created new challenges: for instance, it complicates the integration of planning and scheduling, and forces the Space Shuttle Program to maintain a fluid workforce in which employees must repeatedly change tasks as they shift between Orbiter Major Modifications, flows, and downtime.

¶Throughout the history of Orbiter Major Modifications, a major area of concern has been their wide variability in content and duration. Columbiaʼs last Orbiter Major Modification is just the most recent example of overruns due to technical surprises and management difficulties. It exceeded the schedule by 186 days. While many factors contributed to this delay, the two most prominent were the introduction of a major wiring inspection one month after Orbiter Major Modification roll-in, and what an internal NASA assessment cited as "poor performance on the parts of NASA, USA [United Space Alliance], and Boeing."

¶While the Shuttle Program has made efforts to correct these problems, there is still much to be done. The transfer to Kennedy creates a steep learning curve both for technicians and managers. Planning and scheduling the integration of all three Orbiters, as well as ground support systems maintenance, is critical to limit competition for resources. Moreover, estimating the "right" amount of work required on each Orbiter continues to be a challenge. For example, 20 modifications were planned for Discoveryʼs modification; the number has since grown to 84. Such changes introduce turmoil and increase the potential for mistakes.

¶An Air Force "benchmarking" visit in June 2003 highlighted the need for better planning and more scheduling stability. It further recommended improvements to the requirements feedback process and incorporating service life extension actions into Orbiter Major Modifications.

¶Observations:

¶O10.6-1 The Space Shuttle Program Office must make

every effort to achieve greater stability, consistency, and predictability in Orbiter Major Modification planning, scheduling, and work standards (particularly in the number of modifications). Endless changes create unnecessary

turmoil and can adversely impact quality and safety.

¶O10.6-2 NASA and United Space Alliance managers

must understand workforce and infrastructure requirements, match them against capabilities, and take actions to avoid exceeding thresholds.

¶O10.6-3 NASA should continue to work with the U.S. Air

Force, particularly in areas of program management that deal with aging systems, service life extension, planning and scheduling, workforce management, training, and quality assurance.

¶O10.6-4 The Space Shuttle Program Office must deter-

mine how it will effectively meet the challenges of inspecting and maintaining an aging Orbiter fleet before lengthening Orbiter Major Maintenance intervals.