\label{sec:dot_fus} In this section the DOT for the fuselage is presented, see Figure \ref{fig:DOT_FUS}. All subsystems are either attached to or integrated into the fuselage design. Hence, the fuselage depends greatly upon the various design options of the other subsystems.
Design option tree of the fuselage, with the non feasible options crossed out
\label{fig:DOT_FUS}
The following design options for the fuselage greatly influence the configuration of the final design:
Fuselage structural layout: There are 4 options: a monocoque structure with a conventional skin design, a monocoque with a sandwich type skin, a semi-monocoque or an internal frame. The choice for a particular structural lay out is inherently connected to the material choice of the fuselage. These options will greatly affect the final fuselage mass.
Open or closed cockpit: An open cockpit does not require an additional entry system like a door or opening canopy for the pilot, but does provide less protection. The need for an oxygen supply system will not have a large influence on the actual fuselage design. However, the alternative option of a pressurized cockpit in case of a closed cockpit design will largely affect the fuselage design both in complexity as well as in weight. Similarly, the option to have a windowless cockpit by replacing for example the window with a system of outside cameras and monitors greatly influences the complexity of the cockpit design, as well as the power and mass budgets \cite{nasawindow}\cite{airbuswindow}.
Cockpit location and pilot position: The location of the cockpit will affect all other mechanical and electronic interfaces with other subsystems. Furthermore, for a closed cockpit it would influence the location of the canopy or windscreen as well as a possible door or other hatches. Similarly the seating position of the pilot largely influences the required space in the fuselage, e.g. a large fuselage is required for a lying down position. However, a less inclined position does offer the pilot more protection against the effects of the high g-loads that he encounters during the race.
Based on the key requirements a small number of options can be eliminated from the design option tree of the fuselage. The two options that have been eliminated are crossed out in the DOT of the fuselage, given in Figure \ref{fig:DOT_FUS}. Although only the top level options are crossed out, all lower level options are connected to the this option are consequently also considered non feasible.
The options that are removed are:
Open cockpit configuration
No oxygen supply system
These options were both considered non feasible based on the key requirement that the aircraft is to have a service ceiling of five kilometers (Requirement ARA-MIS-012 MIS). At such a significant altitude an open cockpit would expose the pilot to severely decreased temperatures and oxygen levels \cite{altitude} \cite{temperature} \cite{pilotsafety}. Combined with cruise speeds in excess of 120 kmph, these condition would endanger the pilot. Hence, an open cockpit, as well as the option for a closed cockpit without any oxygen supply system are both considered non feasible.