The demand for commercial aviation is growing at an annual rate of 4%, posing significant environmental challenges. Large-capacity aircraft designed for long ranges are often used on short-to-medium range routes, leading to inefficient fuel consumption and higher emissions. With a future market need for aircraft seating 211 to 300 passengers, there is a clear gap for such a passenger airliner. This report examines the feasibility of the X-300 EcoFlyer, a proposed short-to-medium range aircraft with reduced environmental impact. Designed to carry 300 passengers over 3000 km, the X-300 aims to achieve 25% lower CO2 emissions, 50% lower NOx emissions, and 20% lower noise emissions compared to the Airbus A320neo. The study covers aircraft functions, system design, performance analysis, manufacturing, sustainability, operations, logistics, business viability, and technical risks. The findings confirm the X-300 EcoFlyer's potential to meet future demands with lower environmental impact. Innovations include a noise-shielding fuselage, a water-injected turbofan engine, in-wheel electrical taxing, and an electrical environmental control system. Overall, the X-300 EcoFlyer represents a promising solution to the challenges facing the future of high-capacity air transport.

Given the enduring issues of human-induced climate change, the appeal of strategies aimed at reducing greenhouse gases has never been greater. CO2 is the most concerning greenhouse gas due to the large quantity already emitted into the atmosphere and the ongoing excessive emissions from anthropogenic activities. The transportation sector significantly impacts global warming, as all major transportation modes depend on fossil fuels. The principal fuel used in aviation is kerosene, which is a jet fuel derived from petroleum. Due to the environmental risks associated with petroleum-based fuels, synthetic kerosene is an appealing alternative that could aid the decarbonisation of the aviation sector. This research study aims to conduct a techno-economic analysis of synthetic kerosene, as a potential sustainable fuel for aviation. To address the excessive CO2 concentrations in the atmosphere, the process of extracting CO2 from the air, known as direct air capture, is investigated. A model is developed in Aspen Plus consisting of four main modules, namely direct air capture with NaOH sorbent and calcium looping, syngas production through the reverse water gas shift reaction, Fischer-Tropsch Synthesis and hydrocracking & distillation. There is a substantial gap in the literature concerning the utilisation of direct air capture technologies for synthetic fuel production, and this study aims to narrow this gap.

Aviation is an important contributor to anthropogenic climate change. As indirect greenhouse gases, nitrogen oxides (NOx = NO + NO2) add to the Effective Radiative Forcing (ERF) induced by aircraft emissions. This work addresses a better understanding of emission mitigation by investigating dependencies between engine parameters and emitted nitrogen oxides as a part of the campaign VOLCAN. In-flight near field measurements are conducted using the DLR research aircraft Falcon, chasing an Airbus A321neo equipped with CFM LEAP-1A engines featuring lean combustion through staged fuel injection. Nitrogen oxide concentrations are measured applying the well-established chemiluminescence method. Emission indices are quantified for different fuels including Jet A-1, Sustainable Aviation Fuel (SAF) and two SAF blends with different levels of aromatics. Four combustor inlet temperature settings are tested and staged (lean) combustion is compared to unstaged (rich) combustion. Emissions are measured for two different but technically identical engines, deviating in terms of exhaust gas temperature margin. As expected, results indicate no significant differences in emitted nitrogen oxides for the investigated fuels. Measurements confirm that nitrogen oxide emission indices increase exponentially with combustor inlet temperature. Due to the forced nature of the analyzed rich burn mode, a reduction in nitrogen oxide emissions through lean combustion cannot be confirmed. Based on presented data, a relationship between engine degradation and nitrogen oxides is likely. Near field observations agree with well-established far field measurements and lead to lower uncertainties. Preliminary results of the ECO-Demonstrator campaign are in line with VOLCAN measurements. The performed research is a highly valuable contribution to extremely rare empirical in-flight emission data. Established nitrogen oxide dependencies support technical decision making to reduce aviation’s climate impact.

The escalating concerns surrounding climate change underline the importance of examining greenhouse gas (GHG) emissions across various sectors, with aviation causing approximately 1.9% of the global GHG emissions in 2020. To this modest figure, the Dutch aviation industry acknowledges its share to the climate impact and has gone ahead to objectify it. It has been shown that there has been a 13% surge in the 2018 total GHG emissions, and of the emissions attributable to the Netherlands, a staggering 75% has been emitted beyond its border. Remarkably 95.3% of these beyond-Dutch border emissions are attributable to its aviation sector. This showcases how a localized issue can have global impact.

This research explores the area of military aviation emissions, focusing on the Airbus A330 MRTT operated by the NATO Multinational MRTT Unit (MMU). While commercial aviation adheres to emissions monitoring policies, military aviation is exempted from such obligations. This research adopts a certain approach, focusing not necessarily on the identification of the 'right' methodology but more on the selection of methods tailored to identified goals. The core objective is a sensitivity analysis of emissions and climate impact concerning aircraft design and mission parameters.
In collaboration with the MMU and the Royal Netherlands Air Force (RNLAF), this research uses real-world data for model validation. This research addresses key questions around design and mission parameters with the focus on engine performance modeling, emissions modeling and sensitivity analyses.

The report is structured into four chapters.
The first chapter discusses the literature and background of emissions in commercial and military aviation. The focus will be on the critical role of emission and that of climate impact modeling.
The second chapter outlines the methodology, overall emission model reviews and a climate impact evaluation using Average Temperature Response (ATR).
The third chapter includes the validations using flight data and an external software tool for the emissions validations. The last chapter shows the results and a comprehensive sensitivity analysis. The obtained results aim to collectively present insights for Airbus Defence & Space, towards the conceptual design phase of their new military aircraft. This research contributes to the broader prevailing dialog on sustainable aviation.

The need for more efficient aircraft has led to the conception of innovative engine configurations, such as the combined-cycle engine proposed by Delft University of Technology or the Water-enhanced turbofan developed by MTU and Pratt & Whitney. The evaluation of the potential benefits of these novel engine concepts requires detailed performance studies considering weight and drag penalties as figures of merit. At present, no weight estimation tools with sufficient level of accuracy and flexibility are publicly available, apart from WATE++, a tool developed by NASA. However, this software is subject to export control restrictions and cannot be used outside the USA. For this reason, the development of a new component-based preliminary engine design tool, "Weight EStimation of gas Turbine engines" (WEST), was started. The goal of WEST is to predict the weight of novel engine architectures with a reasonable level of accuracy, accounting for design parameters like turbine inlet temperature, overall pressure ratio, mass flow rate, and turbomachinery configuration, with a minimal set of geometry inputs specified by the user. A previous work demonstrated that WEST can effectively predict the weight of turbofan gas generators. As only the main components are modeled, the WEST estimates account for approximately 70-90% of the actual engine weight.

The capabilities of WEST were expanded in this study to allow for the design of small-scale turboshaft engines. To this purpose, a methodology to design radial compressor disks was implemented, and successfully verified against FEM results. Regarding the modeling of the complete turboshaft, it was found that the predictions of the tool account for only 60-70% of the actual engine weight. Such result was, however, expected, as WEST does not take into account the particle separator and the integrated gearbox, which may account for up to $30\%$ of the engine's total weight.

The aviation industry is shouting out its aim to reach ”net-zero carbon” by 2050. Nevertheless, air traffic is expected to grow up until then, and if fuel consumption is reduced by new technologies and aircraft, other sources of global
warming such as N Ox emissions and contrails are less considered. Therefore, the climate impact improvement of new technologies compared to older ones is not straightforward and requires a deep analysis. This work performs such an analysis via three steps: The selection of a new fleet to be compared with the actual fleet (2019), a comparison between the two fleets emissions via an Aviation Emission Inventory code, and a climate impact assessment with the tool AirClim. The new fleet analysed consists of the replacement of 14 old (entry in service before 2002) Airbus and Boeing aircraft with their new versions (entry in service between 2011 & 2018). The results show a reduction of 8.7% of fuel consumed by total aviation just by replacing the 14 old aircraft with the new ones. On the other hand, it leads to an 8.0% N Ox emissions increase. Nevertheless, the climate impact assessment concludes that this N Ox emissions increase lowers the surface temperature change due to aviation. This is explained by the strong influence of N Ox emissions location on its climate impact. Overall, this new fleet leads to a decrease in temperature change due to aviation in 2050 of 5.3 mK (-5.2%). This work gives important conclusions on the priorities that need to be set for the development of ’greener’ aviation technologies.

This report covers all major steps to establish an aviation emission inventory for 2019. This emission inventory is set up based on four consecutive steps. The first step is to gather all required data in the information model and this also includes some pre-processing of data to make it as complete as possible. The second step is to estimate the point performance of the aircraft at multiple waypoints along the trajectory based on the Base of Aircraft Data (BADA). This also allows for fuel consumption estimation. The third step uses the point performance data to estimate emissions under the respective flight condition. The last step addresses introduced uncertainties based on the different models. From a first principle perspective the uncertainty on a fleet wide scale (and for short and long haul flights) is found concerning the fuel consumption and various emission species (for example nitrogen oxides and carbon monoxide) using a Monte Carlo simulation.

The trajectory data is obtained from flightradar24 in which gaps were identified where the type of aircraft, origin airport or destination airport were missing. Complementing of the database is based around the provided flight numbers and call signs. Based on airline data a variety of assumptions is made relating to payload fraction (69%) and increase in flight distance (8%) compared
to the great circle distance. The trajectory is estimated using the rate of climb and descent provided in BADA. The emission model then uses constant emission indices, the boeing fuel flow method 2 (BFFM2) and the DLR method to compute all emissions according to:
• Constant emission index: carbon dioxide (corrected for emission index of carbon monoxide),
water vapor and sulfur oxide.
• BFFM2: carbon monoxide, unburned hydrocarbons and nitrogen oxides.
• DLR: black carbon emission.
The uncertainty analysis, finally, covers airline operational uncertainty, model uncertainty and engine aging uncertainty to find an average increase in fuel consumption of 4.2%. Due to the influence of fuel flow, other emission species are increased with a different fraction.

Due to computational limitations it has been decided to analyze one week, which will be representative of the entire year. Based on this analysis an annual fuel consumption of 272 Tg is simulated with corresponding carbon dioxide emission of 857 Tg. In addition, a nitrogen oxide emission of 5.3 Tg is found. All emission species are mainly emitted on the northern hemisphere on three geographical locations: north America, Europe and south-east Asia. The strongest recommendation is to include military flights and non-jet aircraft in the analysis (mainly turboprop aircraft). In addition, to decrease the dependency on data of a single week, it is advised to obtain more computational power to allow for analysis of multiple representative weeks preferably in both ICAO specified seasons.
Finally it is recommended to extend the uncertainty analysis to cover more individual uncertainties such as the uncertainty in cruise altitude (based on airline routing) and to find more research on the uncertainty of sulfur content in kerosene.

Concerned about rapidly rising temperatures, international institutions, nations, and companies worldwide examine how to reduce emissions in all economic sectors. Inside the aerospace sector, it is believed that hydrogen technology has the potential to be the best asset to fight global warming. This thesis aims to create and use a methodology to analyze climate implications and uncertainties of a powered hydrogen aircraft. Results are conclusive. Hydrogen aviation reduces surface temperature change by 67\% compared to kerosene aviation by eliminating carbon dioxide emissions, reducing contrail climate impact, and lessening nitrogen oxide emissions. When analyzing uncertainties related to hydrogen emissions and climate effects, the study has demonstrated that even the worst-case situation for hydrogen aircraft is advantageous compared to kerosene aviation.

This study analyses the feasibility of an engine architecture using bypass cooled cooling air as a method for reducing specific fuel consumption of current and future high bypass turbofan engines. As cooled cooling air reduces required turbine cooling massflow, a major source of loss in modern aeroengines, it is believed that the concept can improve engine efficiency. No extensive or explicit study on the merits of this concept has been performed, however.
Using the 0-D engine analysis software GSP, engine performance parameters at Take-Off and Cruise, such as, specific fuel consumption and (specific) thrust were evaluated against altering feed cooling air temperature by 0 to -300K and heat exchanger induced pressure losses of 0 to 8% in the bypass. This was done for two test cases; the Leap-1A engine (TOC OPR 50, CRZ BPR 11.1, TO FN 121kN) representing current conventional technology and GTF2050, a geared turbofan engine (TOC OPR 75, CRZ BPR 17.1, TO FN 174kN) with entry into service of 2050. For the Leap-1A engine the specific fuel consumption increased up to 1.9% at cruise and for GTF2050, the increase was up to 4.1%. It is shown that the change in fuel consumption is linear with the decrease in cooling fraction, as for both engines the specific fuel consumption increases by +0.34% per percent cooling air reduction.
With a reduction in cooling fraction, the exhaust pressure of the core increases, resulting in a higher thrust (up to 2.3%). It is shown that the optimal take-off bypass ratio for minimum fuel consumption shifts up, for the GTF2050 engine from 16.4 to 17.5.
Furthermore, scenario tests and an exergy analysis were performed to find that the impact of different mechanisms; the pressure loss in heat exchanger has minor impact on performance; change in turbine efficiency has small impact; the effect of changed turbine massflow and heat rejection into the bypass are the dominant phenomena.
It is concluded that as a method for reducing fuel consumption, cooled cooling air with the bypass as a heat sink is not feasible for conventional architectures even with extreme design parameters such as high OPR and BPR. Heat rejection to the bypass cannot be effectively utilised and no improvement in core efficiency from reduced cooling air can compensate. In the edge case where there is no heat transfer in cruise, there is an observed specific fuel consumption benefit of up to 4%. The achievable benefit will be lower, however, when accounting for installation penalties.
It is recommended to focus turbine cooling studies on the impact and feasibility of active cooling massflow control without heat rejection, investigate alternative heat sinks for cooled cooling air (e.g. cryogenic fuel), and only consider bypass cooled cooling air as last resort when up-flowing cooling
schemes is not permissible or ineffective.

With an increasing complexity of systems, systematic design space exploration is required for fair analysis and comparison of architecture design options. However, there is still a need for a benchmark problem to support the development & evaluation of optimization algorithms and system architecture design space modeling methods, and to educate stakeholders in system architecture optimization. The thesis focus lies on the creation of such benchmark problem with an application to aircraft jet engine design, which is subsequently tackled by developing an MDO tool using a system architecting approach with mixed-discrete and multi-objective capabilities. The tool was built with the open-source software pyCycle and OpenMDAO and can generate, analyze and compare different aircraft engine architectures on several disciplines including engine thermodynamic cycle analysis, weight, geometry, emissions and noise. Therefore, it is able to tackle the black-box, mixed-discrete, multi-objective and hierarchical nature of system architecture optimization problems.

Climate impact from aviation becomes increasingly important. The Flying-V is a promising concept with superior aerodynamic efficiency and lower weight, leading to lower fuel consumption and lower CO2-emission compared to a tube-and-wing aircraft like the A350. Climate impact from non-CO2 effects (NOx-emission, H2O-emission and contrails) depends on location and time of emission. Due to different design altitudes of the Flying-V and the A350, the impact from all effects have been assessed. At design conditions, the difference in climate impact is 1% in favor of the A350. The benefits of lower CO2- and NOx-emissions are trumped by increased impact from contrails. At identical conditions however, the Flying-V outperforms the A350 in both climate impact and fuel consumption. Also, lower altitudes showed substantially lower climate impact for both aircraft. It is recommended to redesign the Flying-V for lower altitudes and to operate existing civil aircraft at lower altitudes to reduce climate impact.