PhD Defense by Konstantinos Milios

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Konstantinos Milios
(Advisor: Prof. Dimitris N. Mavris)

will defend a doctoral thesis entitled,

A Business Case Framework for the Evaluation of Hybrid-Electric Propulsion Architectures at the Conceptual/Exploratory Design Phase


Thursday, June 23 at 2:00 p.m.
Collaborative Visualization Environment (CoVE)

Weber Space Science and Technology Building (SST II)




Aviation related emissions have steadily been increasing over the past century, becoming a key contributor in global environmental emissions. With leading aircraft manufacturers predicting that the world’s passenger and freighter fleet will more than double by 2038, the world aviation industry is under immense pressure to meet the efficiency, performance, and environmental targets of the future. A new, revolutionary concept, capable of mitigating the impact of global aviation on the climate, is electrified propulsion-based aircraft configurations. In electrified aircraft, the traditional gas turbine is augmented with electrical components to increase system efficiency, and supplement fuel burning with electric power, thus decreasing fuel burn and emissions during flight. The electrification of the propulsion system has created a new class of propulsion system configurations and novel aircraft designs.

The introduction of a new electric powertrain to the existing propulsion system has created a series of challenges. Multiple energy sources are available to meet the system power requirements throughout the flight envelope compared to conventional fuel-only based vehicles. Electrified flight segments (eTaxi, takeoff boost, climb boost, etc.) can lead to large variations in total mission fuel burn depending on the amount and duration of electric power provided. However, large amounts of required electric power can lead to heavy energy storage systems, and therefore, a trade-off exists between the weight of the electrical powertrain and the reduction of mission fuel burn achieved. To make electrified propulsion systems commercially viable for mid- and long-range airplanes, operational, sizing, technological, and safety/certification challenges need to be addressed.

The present work proposes a business case framework for evaluating hybrid-electric propulsion architectures. Technical feasibility and financial viability of notional hybrid-electric concepts is concurrently quantified during the conceptual/exploratory design phase, in combination with uncertainty analysis associated with low maturity technologies and dynamic economic environments. This methodology enables a more accurate and holistic analysis (business case performance) to be conducted and better-informed decisions to be made, thereby increasing the probability of successfully developing and launching hybrid-electric propulsion systems in the next generation of aircraft.

The proposed framework applies a holistic approach to the evaluation of hybrid-electric propulsion architectures at the conceptual design phase. A technical framework was developed based on the Environmental Design Space (EDS) simulation tool capable of performing sizing, mission, and emission analysis of a hybrid-electric aircraft. As part of this framework, an energy storage system sizing process was modeled for determining the optimal electric powertrain design based on different operational modes of the electric system and power management strategies. A comprehensive cost model for hybrid-electric systems was developed and applied for calculating the financial performance of each notional concept. Technical and financial uncertainties associated with hybrid-electric propulsion systems were identified and their impact on the overall business case performance of each concept measured. Finally, the proposed business case framework is demonstrated using a multi-variable scenario-based analysis for determining the impact of external market factors (fuel prices, electricity prices, environmental policies, etc.) on the evaluation of hybrid-electric propulsion systems.



  • Prof. Dimitris N. Mavris – School of Aerospace Engineering (advisor)
  • Prof. Daniel P. Schrage – School of Aerospace Engineering
  • Prof. Jechiel I. Jagoda – School of Aerospace Engineering
  • Dr. Jonathan C. Gladin – School of Aerospace Engineering
  • Mr. Ralph H. Jansen – National Aeronautics and Space Administration


  • Workflow Status:Published
  • Created By:Tatianna Richardson
  • Created:06/13/2022
  • Modified By:Tatianna Richardson
  • Modified:06/13/2022