There are many types of products and systems that have lifecycles longer than their constituent parts (specifically COTS - Commercial Off The Shelf parts). These lifecycle mismatches often result in high sustainment* costs for long field life systems (e.g., avionics, military systems, etc.) due to part obsolescence problems. While there are a number of ways to mitigate obsolescence, e.g., lifetime buys, aftermarket sources, etc., ultimately systems are redesigned one or more times during their lives to update functionality and manage obsolescence. Unfortunately, redesign of sustainment-dominated systems like those mentioned above often entails very large non-recurring engineering and system re-qualification costs.

Ideally, a methodology that determines the best dates for design refreshes, and the optimum mixture of actions to take at those design refreshes is needed. The goal of refresh planning is to determine:

When to refresh the design

Which obsolete parts should be replaced at a specific design refresh (versus continuing with some other obsolescence mitigation strategy)

Which non-obsolete parts should be replaced at a specific design refresh

Which parts should be functionally upgraded.

To address the refresh planning goals above, a methodology called MOCA (Mitigation of Obsolescence Cost Analysis) has been developed. MOCA determines the electronic part obsolescence impact on lifecycle sustainment costs for long field life electronic systems based on future production projections, maintenance requirements and part obsolescence forecasts. The methodology determines the optimal design refresh plan to be implemented during the system's lifetime in order to minimize the system's lifecycle cost.

For technology insertion decision making, MOCA uses a Monte Carlo/multi-criteria decision making hybrid computational technique in which a Monte Carlo is used to accommodate input uncertainties and Bayesian networks are used to make part upgrade decisions at design refreshes.

A case study is performed to demonstrate MOCA's capabilities on a NDU (Navigation Data Unit) that resides on a US Navy class of ships known as the LPD-17.

• Sustainment in this context means all activities necessary to: keep an existing system operational, and continue to manufacture and field versions of the system that satisfy the original and evolving requirements.