Advisor: Dr. Dimitri Mavris

Milestone: PhD Thesis Final Examination (Defense)

Degree Program: Aerospace Engineering

Title: A Methodology for Evaluating Transformational Aircraft Using Non-Drop-In Energy Carriers from Aircraft and System-of-Systems Perspectives

Abstract: Aviation has committed to net-zero carbon dioxide emissions by 2050, and many of the transition pathways that show how this goal could be met rely in part on transformational aircraft powered by non-drop-in energy carriers such as liquid hydrogen. Because these aircraft are not yet fully defined and many of their technologies remain immature, the contribution they make in each pathway depends on assumptions about their vehicle-level performance and about the conditions under which they can enter commercial service. These assumptions differ widely between studies, and the reasons for the differences are often not visible. A comparative review of nine transition pathways shows three limitations. The pathways do not evaluate transformational aircraft on a common, traceable aircraft-level basis with the conventional aircraft against which they are compared. They represent performance uncertainty through discrete cases or scenarios rather than by propagating the uncertainty in the underlying energy-carrier technologies to the aircraft level. And while they list many actions stakeholders must take, they do not systematically identify and structure the requirements that commercial operation places on the wider aviation system. This dissertation addresses these limitations by formulating a methodology that assesses transformational aircraft from two complementary perspectives: that of the aircraft and that of the system of systems in which it is developed, certified, and operated. Two research areas are identified. The first, vehicle performance evaluation, has two parts. The first part formulates a conceptual aircraft design framework in which the storage and propulsion characteristics of the energy carrier are propagated through the affected disciplines and their feedback effects are resolved in the sizing loop, so that the transformational aircraft is sized on the same basis as its conventional reference. The second part propagates the uncertainty in energy-carrier technologies through a validated surrogate of this framework with Monte Carlo simulation, to quantify the resulting spread in vehicle-level performance and the technologies that drive it at a fraction of the cost of direct simulation. The second research area, enabling system evaluation, tailors mission engineering to derive the capabilities required across the life cycle of the aircraft and to assign them to enabling systems and responsible stakeholders, with traceable dependencies among them. The methodology is demonstrated on a liquid hydrogen, direct-combustion, tube-and-wing narrow-body aircraft at the 2050 time frame of the ICAO Long-Term Aspirational Goal study, which serves as the benchmark. Collectively, this research provides a traceable basis for the vehicle-level performance assumptions that transition pathways make for transformational aircraft, for the uncertainty around them, and for the enabling conditions that must be in place before such aircraft can enter commercial operation.

Date and time: 2026-11-20, 8:00 am

Location: CoVE

Committee:
Dr. Dimitri Mavris (advisor), School of Aerospace Engineering
Dr. Daniel P. Schrage, School of Aerospace Engineering
Dr. Graeme J. Kennedy, School of Aerospace Engineering
Dr. Richard A. Wahls, NASA (Retired)
Dr. Burak Bagdatli, School of Aerospace Engineering (Former)