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

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Chapter 3.0 Vehicle Design<br />

3.5 Fuel Storage and Production<br />

Table 3-13: Characteristics of Fuel Candidates (Continued)<br />

Fuel<br />

Characteristics<br />

RP-1<br />

Methane<br />

Propane<br />

Diborane<br />

RP-1 is a stable fuel developed <strong>for</strong> space applications. It is stable up to 370°C (700°F)<br />

and is compatible with all common metals, as well as meoprene, asbestos, fluorocarbons<br />

and epoxies. Its toxicity is comparable to that of kerosene. The liquid temperature<br />

range <strong>for</strong> RP-1 is within the operating range <strong>for</strong> the mission. However, the<br />

freezing point is at the estimated low temperature <strong>for</strong> the mission. To insure that RP-1<br />

doesn't freeze during the mission, some active thermal control would probably be<br />

required.<br />

Methane is stable and compatible with all common metals as well as neoprene, asbestos,<br />

fluorocarbon, and epoxies. It is essentially nontoxic. The main issue with it is its<br />

low boiling point. This would require it to be used as a gas or stored cryogenically.<br />

Due to the small volume of the proposed Entomopter, storing the fuel as a gas would<br />

significantly limit the flight duration. Also using it as a cryogenic liquid would greatly<br />

increase the mission complexity.<br />

Propane essentially has the same properties as methane. It is stable and compatible<br />

with all common metals, as well as neoprene, asbestos, fluorocarbons, and epoxies.<br />

The issues with its use are the same as those of methane.<br />

Diborane is a gas at room temperatures and will slowly decompose. At higher temperatures<br />

it decomposes rapidly. It is compatible with most metals and some organic<br />

materials. It has moderate toxicity. The issues with using diborane are significant. It<br />

would need to be stored as a cryogenic liquid in order to provide <strong>for</strong> sufficient mission<br />

duration as well as minimize the decomposition rate. Because of these issues it<br />

would not be suitable <strong>for</strong> the proposed Entomopter mission.<br />

Table 3-14: Characteristics of Oxidizer Candidates<br />

Oxygen<br />

Fluorine<br />

Oxidizer<br />

Characteristics<br />

Oxygen is highly reactive and nontoxic. It is noncorrosive and is very stable in storage.<br />

The main issue with its use is that it would be in the gaseous <strong>for</strong>m under the mission<br />

conditions. This will significantly limit the volume of oxygen which can be<br />

stored. Liquid oxygen can be used; however, this brings up significant issues regarding<br />

the storage and manufacture of a cryogenic liquid.<br />

Fluorine is highly reactive with almost any material. It can be stored in 18-8 stainless<br />

steel or copper but monel is preferred. It is very important that all materials that come<br />

into contact with fluorine are thoroughly cleaned so that there are no contaminating<br />

particles <strong>for</strong> the fluorine to react with. There are no nonmetallic materials which are<br />

completely unreactive with fluorine. It is also highly toxic and corrosive to body tissue.<br />

Like oxygen, it is a gas at mission temperatures. There<strong>for</strong>e, it would need to be<br />

stored cryogenically in order to be used in the mission.<br />

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