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Advances in Gel Propellant Combustion Technology
Published in Debi Prasad Mishra, Advances in Combustion Technology, 2023
Manisha B. Padwal, Debi Prasad Mishra
Hypergolic liquid propellant systems include pairs of fuel and oxidizer like unsymmetrical dimethyl hydrazine ((CH3)2N2H2, UDMH) and red fuming nitric acid (HNO3, RFNA) and many other hypergolic combinations are known [3]. All these bipropellant combinations could be gelled separately and used, with a wide range of gellants to choose from [9]. Easy mixing is another feature of the development of hypergolic gel propellant. The requirements during mixing are not as stringent as cryogenic gel propellants though all essential handling and storage protocols for hypergolic liquid propellants must be strictly followed [10].
Applied Chemistry and Physics
Published in Robert A. Burke, Applied Chemistry and Physics, 2020
Hypergolic propellant combination used in a rocket engine is one whose components spontaneously ignite when they come into contact with each other. The two propellant components usually consist of a fuel and an oxidizer. The main advantages of hypergolic propellants are that they can be stored as liquids at room temperature and that engines which are powered by them are easy to ignite reliably and repeatedly. Although commonly used, hypergolic propellants are difficult to handle due to their extreme toxicity and/or corrosiveness.
Chemical Rocket Propellants
Published in D.P. Mishra, Fundamentals of Rocket Propulsion, 2017
Liquid-propellant rocket engines in spite of inherent complexities are preferred over the solid-propellant engines due to the added advantages (see Table 6.4) of liquid propellants. They have higher specific impulse and are capable of being throttled, shut down, and restarted easily. Liquid propellants consist of liquid fuel and liquid oxidizer and certain liquid additives. Several types of liquid propellants have been devised over the last six decades. Liquid hydrocarbons, liquid hydrogen, alcohols, and so on are examples of liquid propellants. Some of the examples of liquid oxidizers are liquid oxygen, nitric acid, and liquid fluorine. Liquid propellants can be classified based on the fuel–oxidizer arrangement, energy content, ignitability, and storability. Liquid propellants can be divided broadly into monopropellants and bipropellants. In liquid monopropellants, both fuel and oxidizer elements are located in the same molecular structure. Examples of monopropellants are hydrogen peroxide (H2O2) and hydrazine (N2H4). The monopropellant can be decomposed in the presence of a suitable catalyst into high-temperature and high-pressure gases. Monopropellants can be further divided into (1) simple and (2) composite. In simple monopropellant, fuel and oxidizers are contained in the same molecule. For example, methyl nitrate (CH3NO3) can be decomposed into CH3O and NO2. But the composite monopropellant consists of a mixture of oxidizer and fuel. For example, nitric acid and amyl acetate can undergo exothermic reactions to be used as composite monopropellant. In case of liquid bipropellant, fuel and oxidizer are mixed separately to have exothermic reactions. Liquid hydrogen and liquid oxygen are examples of liquid bipropellants. Based on the nature of ignitability, liquid propellants can be broadly divided into two categories: (1) hypergolic and (2) nonhypergolic. In case of hypergolic propellant, fuel and oxidizer when brought in contact will ignite spontaneously without any external ignition energy. Some hypergolic propellants are hydrogen–fluorine (H2/F2), hydrazine–nitric acid (N2H4/HNO3), unsymmetrical dimethyl hydrazine–nitric acid (UDMH/HNO3), and ammonia–fluorine (NH3/F2). Based on the energy contents, liquid propellants can be broadly classified into three categories: (1) low-energy, (2) medium-energy, and (3) high-energy propellants. Although the energy content of a propellant is dependent on the heat of combustion, in practice, this classification is based on the level of specific impulse. Let us now discuss the physical and chemical properties of certain liquid propellants.
Early Liquid and Gas Phase Hypergolic Reactions between Monomethylhydrazine and Nitrogen Tetroxide or Red Fuming Nitric Acid
Published in Combustion Science and Technology, 2019
Ariel T. Black, Michael P. Drolet, Timothée L. Pourpoint
Within the realm of rocket propellants, hypergolic propellants are fuel and oxidizer combinations that ignite spontaneously shortly after contact with one another, eliminating the need for an external ignition source. Capable of performing multiple thrust maneuvers and engine restarts, hypergolic propellant engines are extensively used in propulsion applications involving orbital maneuvering and attitude control. Unfortunately, the most commonly used hypergols are acutely toxic, carcinogenic, and difficult to handle, prompting investigations into less toxic, “green” hypergolic propellant alternatives (Pourpoint, 2007). While progress continues, no propellant combinations have yet been broadly adopted that result in comparable performance characteristics to traditional combinations comprising nitrogen tetroxide-based oxidizers and hydrazine-derived fuels.
Performance of neat and gelled monomethylhydrazine and red fuming nitric acid in an unlike-doublet combustor
Published in Combustion Science and Technology, 2018
Jacob D. Dennis, Jared D. Willits, Timothée L. Pourpoint
The possibility of increased safety and performance over current propellant technologies has led to research into gelled hypergolic propellants. Hypergolic propellants offer the unique benefit of rapid ignition upon contact eliminating the need for a dedicated ignition system and the gelling process reduces risks associated with these very reactive propellants. Potential safety improvements come through spill reduction during storage and handling, insensitive munitions compliance, reduced toxic vapor outgassing, and slosh reduction (Hodge, 1999). Gelled propellants could also offer high energy density when loaded with energetic materials. Rahimi et al. (2004) describe a number of applications that may benefit from gelled propellants including tactical missiles, attitude control systems, and launch or in-space propulsion systems. Research in the late 1990s and early 2000s focused on hydrazine and monomethylhydrazine (MMH) gelled with cellulose derived gelling agents, such as hydroxypropylcellulose (HPC) (Hodge, 1999; Kubal, 2010; Rahimi, 2004; Solomon, 2013). The majority of these studies also use particulate gelling agents, primarily fumed silica, to gel the oxidizer, either red fuming nitric acid (RFNA) or inhibited red fuming nitric acid (IRFNA).
Modeling Hypergolic Ignition Based on Thermal Diffusion for Spherical and Cylindrical Geometries
Published in Combustion Science and Technology, 2022
David A. Castaneda, Samuel Hassid, Joseph K. Lefkowitz, Benveniste Natan
The ignition mechanism in a rocket system is of great importance for its performance. Hypergolic propellants, i.e., propellants that ignite upon contact, present numerous advantages. Some of them include reliability and efficiency during ignition and very low ignition delay times. They allow rockets to be self-igniting, meaning that no external ignition systems are required (Sutton 2006). Most hypergolic systems use nitric acid or nitrogen tetroxide (NTO) as oxidizers, and hydrazine or hydrazide derivatives such as Monomethyl-hydrazine (MMH) and Unsymmetrical Dimethyl-Hydrazine (UDMH), as fuels. These combinations result in high performance and reliable ignition. However, they are toxic, corrosive, carcinogenic, and environmentally hazardous (Sutton and Biblarz 2017; Wright 1977).