Research

Environmental Impact of Aviation

A hot topic in aviation and aircraft design is improving the environmental impact of new and current aircraft.  The NASA Subsonic Fixed Wing (SFW) Project is focusing on reducing fuel burn, reducing nitrogen oxides (NOx) emissions, aircraft noise and aircraft performance.  Below is a figure showing a set of goals set forth by the NASA SFW Project in 2008 for future aircraft to meet.  Many companies and universities have conducted research on designing future, feasible aircraft designs that target the goals set forth by the SFW project.

Aircraft Allocation

The goals set forth by the SFW project are for individual aircraft; however, various international organization such as ICAO and IATA have set forth goals for the entire aircraft fleet and not individual aircraft.  A new aircraft could be produced that meets all of the SFW goals stated above, but the impact on the entire fleet from this aircraft may not be noticeable and not meet goals from ICAO and IATA.  Therefore, my research has focused on the creation of an allocation tool to assess how new aircraft concepts and aircraft technologies interact with current aircraft in the airline’s fleet.  By allocating the entire fleet, the new aircraft concepts and technologies are integrated into the fleet to maximize the given objective.  These objectives can range from minimizing costs or fuel burn or maximizing airline profit.  In order to create an allocation tool that is manageable, several assumptions and abstractions are made.  All of these abstractions and assumptions are discussed in the appropriate publications, but the levels of abstraction are nicely summarized in the figure below.

The results from the allocation tool can be used to assess NASA’s SFW goals.  In some key results, it was shown that the NASA SFW goal for the N+3 generation aircraft for fuel burn reduction (better than 75% reduction in fuel burn) is necessary to meet IATA’s goal for fuel burn in 2050.  The figure below highlights this key result by showing that if demand grows at a 2% annual rate from 2008 levels to 2050, than the IATA goal for fuel burn and CO2 emissions will be reached in 2050 if all aircraft in the fleet burn 75% less fuel than the aircraft of 2005.  This result published in my Master’s Thesis and Conference Paper AIAA 2010-9205.

Decomposition Approaches for Allocation

Currently, my PhD work is looking at expanding the allocation tool developed as part of my Master’s Thesis.  However, as the allocation problem grows in size, the computational complexity and required solve time also increases.  Therefore, the crux of my PhD research is exploring various ways to decompose the large single allocation problem into smaller allocations problems that are easier to solve.  Possible decomposition approaches are motivated by collaborative optimization, where one top level problem coordinates the smaller subproblems to ensure an optimal, feasible solution.  Some of the preliminary results from the decomposition described in the figure below were presented at the 2010 INFORMS Annual Meeting [Presentation].  While these preliminary results are promising, there is still plenty of research and work to be done.