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

Planetary Exploration Using Biomimetics
An Entomopter for Flight on Mars
0.25
0.2
0.15
0.1 kg LH2, 0.138 m Dia. Tank
0.2 kg LH2, 0.176 m Dia. Tank
0.5 kg LH2, 0.24 m Dia. Tank
1.0 kg LH2, 0.30 m Dia. Tank
1.5 kg LH2, 0.34 m Dia. Tank
2.0 kg LH2, 0.38 m Dia. Tank
0.1
0.05
0
0 0.05 0.1 0.15 0.2 0.25
Insulation Thickness (m)
Figure 3-157: Rate of Energy Loss Due to Boil-off of the Liquid Hydrogen
Most cryocoolers in production have capacities that are much greater than that shown in
Figure 3-157. The power consumption of these cryocoolers is also much greater than that provided
by the proposed Entomopter mission. State-of-the-art cryocoolers require between 2.5 kW
to 7.5 kW of power and provide cooling capacities of between 5 W and 18 W at 20°K. This is
much more than needed for this application. To get an estimate of the cryocooler power required
to meet the power demand shown in Figure 3-157, therefore, the output/power consumption of a
number of state-of-the-art cryocoolers was linearly scaled to the range shown in Figure 3-157.
This scaling was based on the performance average of all the cryocoolers examined. The resultant
cryocooler power requirement is shown in Figure 3-158. These power levels (shown in
Figure 3-158) are achievable and realistic for the proposed Entomopter mission and justify the
use of liquid hydrogen as a means of storing hydrogen for this mission.
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Phase II Final Report