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

Chapter 3.0 Vehicle Design
3.5 Fuel Storage and Production
Based on the density of Inconel-718X (worst case), the RCM actuator with its internal components,
plus the reaction chamber and fuel tank is estimated to weigh 0.3 kg. From Table 3-2, a
reasonable fuel consumption rate is shown to be 0.011 kg/min. A ten minute flight with a 10%
fuel reserve would thus require 0.12 kg of fuel, or 120 ml if the fuel were Hydrazine. This would
therefore occupy 120 cm3 of fuel tank volume (about one quarter that of a cola can).
The weight of the RCM system plus a 10 minute fuel charge is on the order of 0.42 kg. Based on
Table 3-2, this would leave 1.08 kg for mission payload equipment.
The design space identified by Table 3-2 is not believed to be optimum, but instead is only an
example of one combination of flapping frequency, forward speed, fuel type, etc. A parametric
study to identify the boundaries of the design space is required before any determination of optimum
performance can be assessed. Table 3-2 serves to show that Mars Entomopter operation is
indeed possible with useful endurance and payload capacity. Nonetheless, it is still imperative
that as much weight as possible be removed from the Entomopter frame of reference and placed
on the refueling rover without loss of functionality.
3.5 Fuel Storage and Production
3.5.1 Introduction
A number of mission scenarios have been proposed as a means to establish how to best utilize
the capabilities of the Entomopter. From the evaluation of these missions, it became obvious that
to maximize the potential of the Entomopter, it would need to be used in conjunction with either
a lander or rover vehicle that would act as its base for communications, data and sample storage,
and refueling. The ability to refuel the Entomopter is a critical element of the overall capability
of the Entomopter and in providing a viable mission architecture. Without this capability the
Entomopter would provide very little science return, because it would not be capable of flight
for an extended period of time. There are two main approaches that can be taken to provide fuel
for the Entomopter during its mission. The fuel can be carried from Earth and stored on the base
vehicle or hydrogen can be brought from Earth, stored on the vehicle, and combined with elements
gathered from the environment to produce fuel. Ideally, it would be possible to collect all
the materials necessary to produce fuel on Mars from the soil or atmosphere. This would enable
us to essentially have an infinite mission duration limited only by mechanical failure. However,
based on the fuel and environmental survey, all practical fuels that can be used by the Entomopter
require hydrogen (which is not available on Mars). Therefore, the fuel chosen to be produced
on the surface is hydrogen peroxide, which is simple to make and can be constructed out
of the atmospheric gases with the addition of hydrogen.
Because either producing the fuel on the surface or transporting it from Earth requires a finite
supply of material from Earth (fuel or hydrogen), the determination of which method to utilize
will be based on which one provides the longest mission duration for a given amount of weight.
This is a critical determination because it will greatly affect vehicle propulsion system development
by dictating the type of fuel that can be utilized. If it is determined that carrying hydrogen
is more beneficial than a simple fuel such as hydrogen peroxide will be used. If it is determined
that carrying the fuel from Earth is more beneficial, then a more complex energetic fuel can be
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