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Phase II Final Report - NASA's Institute for Advanced Concepts

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Chapter 3.0 Vehicle Design<br />

3.6 Power System<br />

3.6.3 Internal Systems<br />

The internal systems consist of any onboard computer as well as other internal systems used <strong>for</strong><br />

vehicle operation. These systems would include health monitoring, avionics, and flight control.<br />

Energy consumption by the internal systems through one mission cycle would be 1.0 W-h.<br />

Figure 3-170: Typical Internal Systems Power Profile <strong>for</strong> One Mission Segment<br />

3.6.4 Photovoltaic/Battery<br />

The photovoltaic (PV) system consists of a flexible thin film array mounted on the wings of the<br />

Entomopter with a rechargeable battery and battery-charge controller. The array supplies power<br />

directly to the loads and recharging the battery. The battery-charge controller monitors the rate<br />

and state of charge of the battery. The battery is used to supply power when either the array is<br />

inoperable (such as during the night period) or when the load requirements cannot be met by the<br />

array alone. A diagram of the system is shown in Figure 3-171.<br />

The sizing of each of the components depends on the load requirements as well as the available<br />

power from the solar array. Some candidate solar arrays and their characteristics are listed in<br />

Table 3-23 [293]. The type of PV array best suited <strong>for</strong> this application is the thin film array. Thin<br />

film arrays are very lightweight and flexible. They can be easily molded to the Entomopter's<br />

wing and should not affect the aerodynamic per<strong>for</strong>mance of the vehicle. Depending on the characteristics<br />

of the solar array chosen, it may be possible to use the array as the covering on the<br />

wing. This would reduce the structure mass of the vehicle, thereby reducing the impact of the<br />

PV array on the system. Thin film PV arrays are also very robust in their construction and<br />

present the greatest potential to withstand the acceleration/deceleration loads of the rapidly flapping<br />

wing. Because of these characteristics, only thin film PV arrays were considered <strong>for</strong> this<br />

application. Figure 3-172 shows the advancement in per<strong>for</strong>mance of thin film solar cells over<br />

the last 25 years.<br />

209

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