ACARA (Availability, Cost, And Resource Allocation) is a program for analyzing availability, lifecycle cost (LCC), and resource scheduling for a system that undergoes periodic repair. It uses a combination of exponential and Weibull distributions to simulate the useful life of each system component. The replacement of each faulty component is simulated to optimize system performance, and yet comply with constraints on component production and available resources (resupply vehicle capacity, on-site spares, manpower, etc.) These constraints are defined by the user. ACARA evaluates the availability of the system at each capacity level based upon a system block diagram representation.
ACARA is capable of many types of analyses and trade studies because of its integrated approach. It can characterize system performance in terms of both state availability and equivalent availability (a weighted average of state availability). It can determine the probability of exceeding a capacity state to assess reliability and loss of load probability. It can determine the probability of failure for each component type during each period of system operation. ACARA can evaluate the effect of resource constraints on system availability and lifecycle cost. Results are presented in both tabular and graphical form.
ACARA incorporates a user-friendly, menu-driven interface with full screen data entry and uses a file management system to store/retrieve input and results. It can be run on "auto-pilot" mode to simulate a batch of scenarios with no user intervention.
ACARA was developed by a team of engineers at the NASA Glenn Research Center at Cleveland, OH. ACARA II is the revised and updated version of ACARA.