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Theseus
Even after both versions of the Perseus aircraft are deployed, table 2 suggests that there will remain a need for larger payload capability. Harvard and Aurora have investigated such an aircraft under the program name Theseus, an effort supported by the National Science Foundation [7] A variety of propulsion systems (including both fuel cells and internal combustion engines) and aspiration systems (including turbocharging and on board oxygen storage) were combined with state-of-the-art aerodynamic and structural models. The type of results generated by this study are shown in figure 7, results plotting achievable range versus gross take-off weight. In all cases, a "wall" is defined beyond which additional mass is entirely consumed by fuel and structure without producing any net performance benefit. The location of this wall, however, lies far beyond the performance of current systems. Figure 8 illustrates what a typical Theseus configuration might look like, while its performance is compared to that of the ER-2 in figure 9.

[[chart diagram]]
[[left axis] GTOW [kg] 1000. to 5000.]]
[[bottom axis] Range [km] x10^4 .0 to 3.0]]

Figure 7: Typical sizing results from Theseus design studies. For a given payload, adding additional gross weight initially results in rapid increasees [[increases]] in performance (here specified as range at an altitude of 20km). Eventually, however, additional increases in gross weight are entirely consumed by structure and the feul [[fuel]] to carry it and the design encounters a "performance wall." The effect of varying aspect ratio is shown.

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