Green Propellants

Green Propellants

Gilson da Silva (Instituto Nacional da Propriedade Industrial (INPI), Brazil)
Copyright: © 2018 |Pages: 15
DOI: 10.4018/978-1-5225-2903-3.ch008
OnDemand PDF Download:
$30.00
List Price: $37.50

Abstract

Friendly or green compositions are being sought in many kinds of applications, such as fertilization, building materials, energy generation, and so on. Thus, this classification (green) can be established after the subjection of the compound to a thorough toxicity study. The research for low toxicity and no damage to the environment has stimulated the development of specific investigation lines in many areas. Inevitably, the criteria for safe handling, sensitivity and, mainly, specific impulse (efficiencies) of propellant compositions is still superior compared to ecological appeals. Nowadays, however, the solid or liquid propulsion, as aerospace as military, has already compounds to efficiency and eco-friendly characteristics. Thus, the chapter proposed will show a review in the energetic materials area, aiming at the most promising materials to be used as oxidizers and combustibles in a green propulsion system.
Chapter Preview
Top

Introduction

The research for low toxicity and no damage to the environment has stimulated the development of specific investigation lines in many areas. Inevitably, the criteria for safe handling, sensitivity and, above all, specific impulse (efficiencies) of propellant compositions are still superior compared to ecological appeals. Nowadays, however, the solid or liquid propulsion, as aerospace as military, already has compounds to efficiency and eco-friendly characteristics. Thus, the chapter proposed will show a review in the energetic materials area, looking for the most promising materials to be used as oxidizers and combustibles in a green propulsion system.

“Friendly” or “green” classifications are looked for in many kinds of applications, such as agro-chemicals, home appliances (that can save energy or use no toxic gas), automotive engine, and so on, representing a very promising market strategy. In some areas, the “green” classification can be done only after the toxicity study of the compound/composition showing a reduced risk for the mankind and/or the environment.

The acronym “GEMs” is used for an energetic material that shows “green” behavior. In this case, it should show high oxygen balances and halogen and metal-free nature (Rahn, 2010).

In a common liquid propulsive system by using the mixture of liquid oxygen (LOX) and hydrogen (LH), the main product of the reaction is very friendly, water. On the other hand, the reactants are dangerous and unstable substances, in which storage (tanks, pressurized system and valves) and manipulation need an elevated level of complexity and risks.

There is different kind of chemical propulsion (monopropellant or bipropellant) used for distinct proposes (launch or positioning) where the compound is in varied stage (solid, liquid or gas).

Nowadays, Hydrazine is the only liquid monopropellant widely used for the generation of hot gases, despite its high toxicity, volatile and carcinogenic properties that require extreme handling precautions, increasing the operational complexity (Gronland et al., 2006).

The propulsive system LOX/LH can be used as an example of a bipropellant propulsion, in which oxidizer and fuel liquids are injected, atomized, and mixed at the first zone of the combustion chamber (Silva, Rufino, & Iha, 2013). Another example using hydrazine is a hypergolic bipropellant, where the droplets of hydrazine and nitrogen tetroxide in liquid phase react spontaneously (Hawkins, Schneider, Drake, Vaghjiani & Chambreau, 2011).

In a solid propellant rocket systems (heterogeneous propellant), with a binder Hydroxyl-Terminated Polybutadiene (HTPB) or Glycidyl Azide Polymer (GAP), aluminum (fuel) and ammonium perchlorate (AP – oxidizer), the toxicity does not stay only in the hydrogen chlorine, aluminum oxide and aluminum chloride, which affect the environment around rocket launch sites, burning the vegetation around them, but also in the isocyanate-based materials (Sciamareli, 2010), used to cure the binder to obtain a thermosetting hybrid fuel grain, which is a carcinogenic and has negative reproductive effects, as well as in the perchlorate ions which may act as a teratogen and has adverse effects on the function of the thyroid gland (Ilyushin, Tselinsky & Shugalei, 2012).

In spite of the liquid bipropellants (e.g. LOX/LH) which generally offer higher specific impulse than liquid monopropellants, the bipropellant systems tend to be more complicated because of the extra hardware components (pumps, valves, tanks, connections, etc.) needed to make sure the proper amount of fuel is mixed with that of the oxidizer.

Unlike from the liquid propellant, which is injected from the external tank into the combustion chamber at the time of ignition, solid propellants are placed directly on it. The solid propellants system requires, normally, pyrotechnic charges to initiate the combustion, but pyrotechnic charges are susceptible to initiation by electromagnetic radiation or accumulated electric charge, increasing the accidental initiation risks of the solid rocket motor, according to the Department of Defense Interface Standard (2010).

Complete Chapter List

Search this Book:
Reset