RAS. Reliability Analysis for Phased Missions

The Reliability Analysis System, RAS, is an integrated package of computer programs for the quantification of fault trees. In particular, RAS has the capability of performing phased mission analysis. A phased mission is a task to be performed by a system during which the logic model and/or the component failure mode characteristics change at predetermined times. RAS is capable of finding minimal cut sets from fault trees and of calculating reliability characteristics for the basic events, the minimal cut sets, and the top event of a fault tree. In addition, mission cut set cancellation and four methods of bounding mission unreliability have been incorporated into RAS.