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

Planetary Exploration Using Biomimetics
An Entomopter for Flight on Mars
The C rating is a gauge of the current producing capacity and discharge time of the battery. At
1C the 930 mAh battery would produce 930 mA for 1 hour. At C/5 it would produce 186 mA for
5 hours, and at 2C it would produce 1,860 mA for 0.5 hour. It should be noted that as the discharge
time decreases, the overall capacity of the battery will also decrease.
Based on the estimated power consumption of the various systems, shown in Figures 3-168
through 3-170, the maximum power consumption is 3.5 W, and the total energy consumption for
a mission cycle is 3.1 W-h. An estimate of the required battery capacity is 100% of the total
energy required for the mission. This battery capacity allows the battery to provide power to the
systems when the array is offline (shadowed). This also provides a redundancy for supplying
sufficient power in the event the array fails. This requires a battery with 3.1 W-h of capacity.
Based on the battery data listed in Table 3-25, the battery mass would be 0.023 kg.
The overall system mass estimate for the array/battery system is listed in Table 3-26.
Table 3-26: PV/Battery System Mass Estimate
System Component
Mass (kg)
Solar Array 0.014
Battery 0.023
Contingency (50% for wiring, electronics, etc.) 0.037
Total System Mass 0.0555
It should be noted that the system mass shown in Table 3-26 represents values based on state-ofthe-art
components. With future advancements in these components, this may be significantly
reduced. Also any variation in the assumptions used to generate these numbers will also greatly
affect these results.
3.6.7 Thermoelectric Power Generation
The basic principle behind a thermoelectric power generator is that if two different metals, semimetals,
or semiconductors are joined at one end and separated along their length, a current will
be produced in each metal strip as long as there is a temperature difference between each side of
the junction. The configuration of a thermoelectric power generator is shown in Figure 3-181.
The heat source provides a high-temperature source from which heat will flow through the converter.
For the Entomopter application, heat can be generated either through the combustion of
the propellant or from an isotope heat source. A heat sink must also be used to dissipate the
excess heat and maintain the cold side of the thermoelectric generator at a temperature below
that of the hot side. It is this temperature difference that produces the direct current electrical
power. Thermoelectric generators can be made for power levels ranging anywhere from 10 -6 W
to 10 2 W. Semiconductor material is by far the best choice for the construction of a thermoelectric
generator. These materials can presently achieve efficiencies on the order of 5% to 10%.
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Phase II Final Report