I'm looking for a summer intern who loves system reliability analysis to personally work with me on an exciting project. Many critics have claimed that distributed propulsion systems have much added complexity that will negatively impact maintenance cost and dispatch reliability. I have countered that claim saying that it depends on the comparative component complexities and part counts (especially critical parts that don't fail gracefully). There is no question that distributed systems have significantly more "design" complexity that take extra up front analysis, but as real world metrics capture the differences, my belief is that (if designed while taking dispatch reliability into account) that distributed propulsion will win.
A generalization of this thesis goes like this... while a single engine piston at the top system level appears to be a single component with a claimed reliability, there are actually hundreds of moving parts and the reliability of each sub-components depends significantly on the duty cycle, usage conditions, maintenance, etc. Often parts fail prior to the claimed reliability (and require periodic maintenance that takes the aircraft out of service, thus impacting availability/dispatch reliability). As a big singular component, the engine can't be easily replaced or serviced.
A distributed electric propulsion system has the opportunity to be designed to as a greatly simplified component. No gearbox, no cooling system, and the only moving part with that experiences contact are bearings, with no thermal cycling across the components (which are a major cause of life limits) as well as no combustion (which creates cyclic loading that stresses components). Such a propulsion system has dramatically fewer parts to fail, inspect or service, and the failure modes more graceful along with the size/installation of the propulsion unit enabling replacement in a matter of minutes without support equipment since each unit weighs less than 25 lb and is designed as a LRU. With Whisper, there are no decreases in efficiency at smaller propulsion sizes, with easier thermal management, and dramatically lower costs.
Others may view this as a simple buildup of sub-component reliability to establish the rolled up total propulsion system reliability. My perspective is that with the propulsion system changing so dramatically, that there's much more to understanding a more comprehensive, true dispatch reliability (and the resulting support logistics and maintenance programs that are impacted).
While there was an early NASA study performed by Boeing in this area, it was quite weak in many areas and didn't get into the complexities that could dramatically impact the end result. My hope is that as an industry we can get to analyses and logic flows that can build consensus. I'd appreciate recommendations for doing this analysis that brings in others perspectives, and if there's a student excited about this subject - please DM me.
