# A Conceptual Design Methodology for e-VTOL Aircraft for Urban Air Mobility
## 4 Sensitivity Analyses for Design Space Exploration
### Future Powertrain Technology  
This section presents the results of the conceptual design of the _TiltOne_, with electric propulsion technology assumptions based on forecasts for the 2035 time horizon.  
Since the introduction of this type of aircraft is expected to occur gradually over the next few years, with a difficult introduction in the immediate future, it is reasonable to assume that more advanced powertrain technologies will be available. This assumption is also supported by the fact that a great effort is being made by the scientific community to speed up the development process, especially regarding batteries and electric motors [4; 5; 6].  
For the purposes of the study presented here, the reference values reported in Table 12 have been selected:  
Figure 13: \(W/S\) vs. \(T/A\) charts of battery mass (current technology) varying speed and range. Each plot shows a highlighted area, which identifies the design space compliant with the constraints.  
The most important effect of changing the assumptions on technological parameters is the strong reduction of battery mass, which is due to the increased BED values (doubled, if compared to today technology scenario).  
To quantify such effect, sensitivity analyses have been performed by varying the _TiltOne_ wing loading (_W/S_), between 70 and 110 kg/m\({}^{2}\), and disk loading (_T/A_), between 40 and 70 kg/m\({}^{2}\). Results are reported in Figures 14 and 15, where the cruise speed increases along the rows, and the design range grows along the columns. Each possible combination of \(W/S\) and \(T/A\) on the map represents a _TiltOne_ aircraft designed according to the workflow depicted in Figure 2.  
The values of the battery mass required for the _TiltOne_ design missions as _W/S_ and _T/A_ vary are shown in Figure 14, whose trends follow the descriptions already provided in the current technology scenario. For both \(W/S\) and \(T/A\) parameters, the lower battery mass required for the flight phases is reflected with a snowball effect on the whole aircraft mass.  
In Figure 15, the same trends already observed in the current technology scenario can be recognized. Among the quantitative differences generated by the different assumptions, it is worth emphasising the significant enlargement of the feasible design space, which is limited only by the minimum propeller clearance constraint. In fact, it is possible to notice that the wingspan and MTOW constraints are not even in the maps, since they are outside the explored design space; this also indicates that, with this level of technology, it would be possible to increase the potential of the _TiltOne_ in terms of transport capabilities.  
The lower weights of the configurations assessed in this phase compared to those described in Section 4.2 are clearly related to the better performance of the electrical equipment.  
To better understand the impact of the different assumptions on technology level, two solutions having the same \(T/A\) and \(W/S\) input are compared. As shown in Table 13 the \"future\" _TiltOne_ configuration has a significant MTOW reduction (\(-36\%\)), consequence of the higher energy density of the batteries, which reduces their mass by \(71\%\) and, consequently, the MTOW. Accordingly, the maximum continuous electric motor power is reduced (\(-36\%\)) since the same specific power is prescribed for both configurations. A reduction of MTOW generates an aircraft with smaller wingspan, which can result in less space-demanding vertiports and easier on-ground management of the fleet.  
Figure 15: _W/S_ vs. _T/A_ charts of MTOW (future technology) varying speed and range. Each plot shows a highlighted area, which identifies the design space compliant with the constraints.