deletions | additions       diff --git a/Chapters/6g.Power.tex b/Chapters/6g.Power.tex  new file mode 100644  index 0000000..4aeb41a  --- /dev/null  +++ b/Chapters/6g.Power.tex 
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\section{Power}  \label{sec:dot_power}  %Please do not forget to add new symbols to the nomenclature e.g.: \nomenclature{$t_{element}$}{Thickness coefficient of plate \nomunit{[$-$]}}  It was decided that the power storage and delivery cannot be ground supported but has to be independent. Therefore, the cable connection to the ground was mitigated, since it is not feasible.  Furthermore, nuclear powered options are also not considered any further, since they are deemed too harmful to the environment and violating the sustainable spirit of the aircraft design.  The next step, the design configuration, is influenced mainly by the choice of a single or distributed power source and whether a rechargeable or non-rechargeable system is selected. Thereafter, the type of storage system, batteries, fuel cells and others, are investigated and traded off.  diff --git a/Chapters/6h.ERS.tex b/Chapters/6h.ERS.tex  new file mode 100644  index 0000000..53662d3  --- /dev/null  +++ b/Chapters/6h.ERS.tex 
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\section{Energy Recovery System}  \label{sec:dot_ers}  %Please do not forget to add new symbols to the nomenclature e.g.: \nomenclature{$t_{element}$}{Thickness coefficient of plate \nomunit{[$-$]}}  The choice of energy recovery system depends on whether to replenish a battery or fuel cell. Different types of energy can be recovered. Kinetic energy could be recovered from braking during landing or when throttling down. Thermal energy can be recovered from battery and engine waste heat using thermoelectric generators which convert a temperature difference in current or a thermodynamic Rankine cycle. Electromagnetic energy could be recovered from the fields created by the engine and cabling.   Several non-feasible options are identified. Firstly managing potential energy is part of race tactics, not an energy recovery system. Secondly the technology to recover energy from electromagnetic fields only deliver a few microWatts, to small for practical use to recharge aircraft batteries.   \begin{figure}[htbp]  \centering   \includegraphics[width=\textwidth,height=\textheight,keepaspectratio]{Figures/DOT_energyrecoverysys_feas.png}  \caption{Design option tree for the energy recovery system.}  \label{fig:dot_ers}  \end{figure}  diff --git a/Chapters/6i.Configurations.tex b/Chapters/6i.Configurations.tex  new file mode 100644  index 0000000..bb7f7d7  --- /dev/null  +++ b/Chapters/6i.Configurations.tex 
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\chapter{Initial Aircraft Configurations Design Option Tree}  \label{sec:ACconfigurations}  Many design options were identified in the investigation of the design options for the different subsystems (see Sections~\ref{sec:dot_fus}~through~\ref{sec:dot_control}) which could lead to hundreds of possible designs. Since many of these designs would be similar or differ only in aspects that are not yet important for the current design phase, it was chosen to create a smaller number of designs that would cover only the main design choices. The choices that can easily be changed, such as the specific tail shape or the power source, are left open in the design configurations and are defined later when the subsystems are designed. Also, subsystems that have to be traded off against each other for individual cases, which will be done in further steps, are left open for changes at this point. Eventually eight concepts are considered in this section, which differ in wing location and configuration as well as in the way they are propelled.  The design option tree for configurations, that they are based on, is presented in Figure~\ref{fig:DOTconfigurations}.  \begin{figure}[htbp]  \centering   \includegraphics[width = \textwidth]{Figures/ConfigurationDOT.jpg}  \caption{Design option tree for the configurations, considering wing and propulsion configuration.}  \label{fig:DOTconfigurations}  \end{figure}  The design option tree shows that several options were discarded. It was decided to not consider too experimental designs but rather focus on configurations that can be analysed in practice. Therefore, the other options are not considered any further. Also, because of the main requirement of the design, the electric propulsion, non electric options are not considered. Additionally, the pusher and puller configuration was discarded for practical reasons, since this would require at least 2 engines and the aerodynamic effects would become very complex and the two design choices would cancel the advantages. The option of engines installed sideways on the fuselage was discarded since it would increase the roll inertia substantially and increase the structural complexity.  \subsection{Design Option 1}  This design is a flying wing. The configuration has wing tips as vertical stabilizers. The design is propelled by two propellers that are mounted in the wing. The battery can be placed in the middle to reduce the moment of inertia (MOI). The design is shown in Figure~\ref{fig:config_flywing1.1}~and~\ref{fig:config_flywing1.2}.  \begin{figure}[htbp]  \centering  \begin{minipage}[htbp]{0.4\textwidth}  \includegraphics[width = \textwidth]{Figures/11.pdf}  \centering  \caption{Top view of design configuration one}  \label{fig:config_flywing1.1}  \end{minipage}  \hfill  \begin{minipage}[htbp]{0.4\textwidth}  \includegraphics[width = \textwidth]{Figures/12.pdf}  \centering  \caption{Side view of design configuration one}  \label{fig:config_flywing1.2}  \end{minipage}  \end{figure}  This configuration is chosen for its aerodynamic efficiency and low drag. It can thus be very energy efficient. The heavy battery can be freely positioned so there is a lot of freedom when it comes to the centre of gravity (CG) position.   The disadvantages for this design are that the maneuverability is not very good, the lateral moment arm is quite small so the control surfaces should be very large and the MOI around the x-axis is very large. The design is structurally complex and it will also be rather difficult to fit everything within the thickness of the wing. Adding a canopy for the pilot, for example, would take away the advantage of a low drag. Additionally, the incorporation of the propellers will reduce the lift.  \subsection{Design Option 2}  The second design is also a flying wing, but with a pusher propeller installed in the back. Thus, the lift surfaces are not disturbed and a high efficiency is ensured. However, the design is still very complex since the flying wing is difficult to make stable and controllable. This negatively affects the maneuverability. Structural complexity results from the incorporation of the cockpit in the wing, possibly disturbing the aerodynamic performance.  This design is considered because of its efficiency and its improved L/D ratio compared to the others.  The design is shown in Figure~\ref{fig:config_flywing2.1}~and~\ref{fig:config_flywing2.2}.  \begin{figure}[htbp]  \centering  \begin{minipage}[htbp]{0.4\textwidth}  \includegraphics[width = \textwidth]{Figures/21.pdf}  \centering  \caption{Top view of design configuration two}  \label{fig:config_flywing2.1}  \end{minipage}  \hfill  \begin{minipage}[htbp]{0.4\textwidth}  \includegraphics[width = \textwidth]{Figures/22.pdf}  \centering  \caption{Side view of design configuration two}  \label{fig:config_flywing2.2}  \end{minipage}  \end{figure}  \subsection{Design Option 3}  The third configuration that was selected for consideration is a conventional design that is very similar to the aircraft used in Red Bull Air Races (RBARs) nowadays. It was chosen to compare the conventional configuration to the more experimental ones, as presented in the design options 1 and 2.  The design is shown in Figure~\ref{fig:config_conv3.1}~and~\ref{fig:config_conv3.2}.  \begin{figure}[htbp]  \centering  \begin{minipage}[htbp]{0.4\textwidth}  \includegraphics[width = \textwidth]{Figures/31.pdf}  \centering  \caption{Top view of design configuration three}  \label{fig:config_conv3.1}  \end{minipage}  \hfill  \begin{minipage}[htbp]{0.4\textwidth}  \includegraphics[width = \textwidth]{Figures/32.pdf}  \centering  \caption{Side view of design configuration three}  \label{fig:config_conv3.2}  \end{minipage}  \end{figure}  The design has a straight wing around the center of the fuselage and a fuselage mounted horizontal and vertical tail. The electric-motor is mounted in the front, featuring a pull-propeller.  It is expected that this design will perform well in the trade off, since similar designs are currently used in aerobatic races, but it may not be the most efficient option. The fuselage with canopy increases the drag and the puller propeller may reduce the efficiency of the wing as it disturbs the flow in front of it. The tail's efficiency is also reduced as it experiences downwash from the wing.  \subsection{Design Option 4}  This configuration is similar to the previous one, in the sense that it is based on the conventional aircraft configuration, with a main wing and a tail. However, the puller propeller was replaced by a pusher at the tail to decrease the flow disturbance over the wings. It has to be kept in mind that pusher propellers are less efficient than pullers.  The design is shown in Figure~\ref{fig:config_conv4.1}~and~\ref{fig:config_conv4.2}.  \begin{figure}[htbp]  \centering  \begin{minipage}[htbp]{0.4\textwidth}  \includegraphics[width = \textwidth]{Figures/41.pdf}  \centering  \caption{Top view of design configuration four}  \label{fig:config_conv4.1}  \end{minipage}  \hfill  \begin{minipage}[htbp]{0.4\textwidth}  \includegraphics[width = \textwidth]{Figures/42.pdf}  \centering  \caption{Side view of design configuration four}  \label{fig:config_conv4.2}  \end{minipage}  \end{figure}  The pusher propeller also adds design complexity to the configuration since the tail section of the fuselage, that is usually small and strong for resisting the tail loads acting on the fuselage, has to be strengthened and made larger to house the propeller.  \subsection{Design Option 5}  Concept five is also a conventional configuration. In contrast to design 3 and 4, this design features two puller propellers mounted on the wings. This allows for the incorporation of smaller engines and thus a higher propulsive efficiency. The complexity does not differ substantially from the other designs, since the structural complexity previously required for the fuselage is shifted to the wings. Additionally, the possible required increased thickness of the wings to house the engines may even reduce the weight. The L/D ratio may be slightly worse because of the flow disturbance through the propellers in front of the wings.  The design is shown in Figure~\ref{fig:config_conv5.1}~and~\ref{fig:config_conv5.2}.  \begin{figure}[htbp]  \centering  \begin{minipage}[htbp]{0.4\textwidth}  \includegraphics[width = \textwidth]{Figures/51.pdf}  \centering  \caption{Top view of design configuration five}  \label{fig:config_conv5.1}  \end{minipage}  \hfill  \begin{minipage}[htbp]{0.4\textwidth}  \includegraphics[width = \textwidth]{Figures/52.pdf}  \centering  \caption{Side view of design configuration five}  \label{fig:config_conv5.2}  \end{minipage}  \end{figure}  A critical downside of this design for aerobatics is the increased weight of the engines outboard of the center of the fuselage. This increases the inertia and thus slows down the roll rate. Therefore, aerobatic maneuvers, particularly in roll, cannot be performed as fast as in other configurations.  \subsection{Design Option 6}  This design is a canard configuration with the propulsion system mounted at the tail of the aircraft. A single propeller is used resulting in a pusher system. The wing is attached to the fuselage closely to the back  The design is shown in Figure~\ref{fig:config_canard6.1}~and~\ref{fig:config_canard6.2}.  \begin{figure}[htbp]  \centering  \begin{minipage}[htbp]{0.4\textwidth}  \includegraphics[width = \textwidth]{Figures/61.pdf}  \centering  \caption{Top view of design configuration six}  \label{fig:config_canard6.1}  \end{minipage}  \hfill  \begin{minipage}[htbp]{0.4\textwidth}  \includegraphics[width = \textwidth]{Figures/62.pdf}  \centering  \caption{Side view of design configuration six}  \label{fig:config_canard6.2}  \end{minipage}  \end{figure}  If the wing, propeller and energy source are located towards the tail of the aircraft, there is a mass concentration shifting the centre of gravity rearwards. Therefore, a low mass moment of inertia is a main characteristic of this aircraft resulting in improved pitch- and roll manoeuvrability. The canard will reduce the stability margin which is beneficial for aerobatic racing aircraft. Due to the aft position of the centre of gravity, the canard has a long arm and the manoeuvrability advantage becomes even more prominent.  There are some difficulties that arise in this design. The most prominent one is the danger of stall of the canard, resulting in the aircraft not being able to perform some aerobatic maneuvers. The aft propeller may result in insufficient clearance during take-off and landing. Other problems may arise from the need for cooling of the electric motor which is harder to reach with inlets and a smaller possible centre of gravity range.   Furthermore, visibility may be decreased due to the aft position of the wing. A canard configuration could also result in decreased visibility.  \subsection{Design Option 7}  This design differs from configuration 6 in the configuration of its propulsive system. It is still a canard configuration. There are two propellers. They are attached to the main wing of the aircraft and push the aircraft forward.  The design is shown in Figure~\ref{fig:config_canard7.1}~and~\ref{fig:config_canard7.2}.  \begin{figure}[htbp]  \centering  \begin{minipage}[htbp]{0.4\textwidth}  \includegraphics[width = \textwidth]{Figures/71.pdf}  \centering  \caption{Top view of design configuration seven}  \label{fig:config_canard7.1}  \end{minipage}  \hfill  \begin{minipage}[htbp]{0.4\textwidth}  \includegraphics[width = \textwidth]{Figures/72.pdf}  \centering  \caption{Side view of design configuration seven}  \label{fig:config_canard7.2}  \end{minipage}  \end{figure}  This design was added to the design options to decrease the problem of clearance arising from the large rotor in the back of the aircraft that was encountered in design 6. Also, the two rotors are more efficient since they are smaller and the air they see is only disturbed by the wings, not the entire fuselage.  The problem with this design is the maneuverability, particularly in aerobatic maneuvers. The two engines decrease the roll rate since they cause an increased inertia through the weight concentration outboards of the fuselage.  \subsection{Design Option 8}  Design configuration 8 is a biplane with a puller propeller. Biplanes have been quite popular for aerobatic aircraft, which is why it is considered as well to determine how it performs compared to the other configurations. The biplane has very good maneuverability characteristics, because of its low inertia, resulting from the shortened wingspan and the mass being centered close to the centre line of the fuselage. However, the drag also increases since another wing is added. The lift does not increase in the same way because of the two wings influencing each other negatively. Furthermore, it has to be noted that a second wing will add weight to the overall design.  The design is shown in Figure~\ref{fig:config_bi8.1}~and~\ref{fig:config_bi8.2}.  \begin{figure}[htbp]  \centering  \begin{minipage}[htbp]{0.4\textwidth}  \includegraphics[width = \textwidth]{Figures/81.pdf}  \centering  \caption{Top view of design configuration eight}  \label{fig:config_bi8.1}  \end{minipage}  \hfill  \begin{minipage}[htbp]{0.4\textwidth}  \includegraphics[width = \textwidth]{Figures/82.pdf}  \centering  \caption{Side view of design configuration eight}  \label{fig:config_bi8.2}  \end{minipage}  \end{figure}