Q: What does the message *** ERROR: Singularity In Stiffness At *X.XXX" mean?
REV 7.00

A: This means there is a problem with the model you used for the structural analysis. In particular, it is reporting a singularity in the stiffness matrix at the referenced node. In general, there are two classes of singularity: local and global. The local ones are caused by stiffness mismatches between elements and the global ones are caused by not completely restraining the system; i.e. here the structural system can move without causing a change in load. This often happens when one has a simple "stick" model of a vessel. MOSES adds water springs to restrain the vessel, but since all the nodes are in a line you still get a rigid singularity in RX.