The WR-21 gas turbines drive General Electric alternators and were intended to lose output gradually when operating conditions deteriorated. The turbine and its Northrop Grumman intercooler had not been designed to work together, following the abandonment of an earlier French-system arrangement associated with Horizon. Their interaction could instead cause the turbines to trip in difficult hot-weather conditions. The original fit then provided only two two-megawatt diesel generators, although three or four generators had been considered. Four such diesels would have supplied eight megawatts, with the argument that this reserve would have made the public power-loss problem extremely unlikely. The later upgrade replaces the two generators with three three-megawatt units. Successive savings had removed headroom intended to let the ship cope when its machinery encountered problems.
Chapter · 46:21-50:24
Propulsion trouble and lost design slack
WR-21 turbines, mismatched intercoolers, and limited diesel generation left the Type 45 power system with less resilience than the ship could have had.