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

Planetary Exploration Using Biomimetics
An Entomopter for Flight on Mars
considered. The main restriction is that the fuel needs to be a monopropellant. This requirement
is based on reducing the complexity of the engine and fuel storage/feed system on the Entomopter.
Minimizing wing loading on the Entomopter is critical, so a fuel system with only one
tank and associated piping is highly beneficial.
3.5.2 Propellant Selection
The design of the Entomopter requires the generation and expansion of gas for the vehicle to
operate. This gas can be generated either by combustion, a catalytic reaction, or sublimation of a
material. The gas is necessary to drive the reciprocating piston that drives the wing motion.
However, it is also needed for various other aspects of the vehicle’s design, including ultrasonic
emissions for altimetry and obstacle avoidance, air bearings supply, and lift-augmentation blowing.
Because gas generation is an integral part of the operation of the vehicle, the power source
must be a fuel-based system.
Fuel selection will be based on the following criteria:
1. Ability of the fuel to meet the environmental conditions of the mission,
2. Ability of the fuel to provide the required amount of gas for the operation of the Entomopter,
3. and ability to make fuel on the Mars surface out of the indigenous materials present in
the atmosphere and soil.
The ideal fuel will be a liquid monopropellant. A monopropellant is desirable because it reduces
the complexity of storage and delivery systems for the fuel. Liquid form minimizes the storage
volume and provides for easier containment.
The operational constraints on the fuel require it to be capable of being stored for extended periods
of time (up to 2 years) with little or no degradation, and to be capable of withstanding the
deep space environment during transit as well as the environment on the surface of Mars. The
main environmental issue during transit and on the Mars surface is the temperature. Assuming
that there is no active thermal control or heating available, the fuel must be capable of withstanding
temperatures down to -40° C for extended periods of time. If the fuel can remain liquid
at these temperatures, this greatly simplifies the propellant delivery system as well as eliminates
the need for power- and weight-consuming heaters. This also reduces the overall risk of the mission
by eliminating a failure source occurring from improperly thawed fuel or a failed heater.
An overall list of potential fuels (and fuel oxidizer combinations) is listed in Table 3-10 [119,
45]. The ability to meet the requirements listed above will be evaluated, and each will be ranked
regarding their applicability for the mission.
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Phase II Final Report