Rocket oxidizers

Noble Gas-Oxygen Compounds. Since the discovery in 1962 that the noble gases are not truly chemically inert, propellant chemists became intrigued with the possibility that they could serve as excellent carriers of oxygen (and fluorine) and thus generate a new family of chemical propellants. While the importance of this discovery to chemistry cannot be underestimated, so far it has not led to the preparation of new compounds as significant rocket oxidizers. 

Theoretical Basis. Heterogeneous fuels are suspensions of finely divided metals or metal compounds in appropriate liquid fuels and represent one approach for using the low molecular weight metals (and certain of their derivatives) that have high heats of combustion with typical rocket oxidizers. The theoretical basis for the interest in metal-containing fuels is discussed in the introduction. Glassman (16) showed that all... 

The performance of F2, OF2, and NF3 or N2F4 shows where the synthesis potential of rocket oxidizers is. 

The mixtures HNO3-N2O4 are highly corrosive and attack metals (steel, aluminium or chromium, nickel). Corrosion can be inhibited by the addition of fluorine compounds, notably HF or PF [1]. The addition of 0.7 wt% of HF reduces the corrosion by a factor over 100 and the mixture of 44% N2O4 and 56% HNO3 with 0.7-1.0% HF termed standard HDA is in current use as a rocket oxidant fuel. 

We do not know how much ozone may actually be present in a pressurized cabin of future aircraft, as other factors, such as heating of the air passing the compressor or contact with various substances, may destroy part of the ozone and use of oxygen masks would prevent inhaling of ambient air entirely still, the possibility of inhaling ozone exists. The use of ozone as a rocket oxidizer H) may add to such a possibility. 

M.R. Sanger, M. Molho, and W.W. Howard, Exploratory Evaluation of Filament-Wound Composites for Tankage of Rocket Oxidizers and Fuels, AFML-TR-65-381, Air Force Materials Laboratory, Wright-Patterson Air Force Base, Ohio (1966). 

R. Seltzer, Impact widening from explosion of Nevada rocket oxidizer plant. Chemical and Engineering News, August 8,1998. 

It is, therefore, our conclusion that the physiological dangers of working with fluorine as a rocket oxidizer have been greatly overrated, and conditions are definitely no worse than those encountered in working with many other present-day chemicals. 

It also has lubricating properties similar to graphite. The hydrides are easily oxidized with considerable energy liberation, and have been studied for use as rocket fuels. Demand is increasing for boron filaments, a high-strength, lightweight material chiefly employed for advanced aerospace structures. 

These alloys are of vital importance in the construction of modern aircraft and rockets. Aluminum, evaporated in a vacuum, forms a highly reflective coating for both visible light and radiant heat. These coatings soon form a thin layer of the protective oxide and do not deteriorate as do silver coatings. They are used to coat telescope mirrors and to make decorative paper, packages, toys. 

Polymer-based rocket propellants are generally referred to as composite propellants, and often identified by the elastomer used, eg, urethane propellants or carboxy- (CTPB) or hydroxy- (HTPB) terrninated polybutadiene propellants. The cross-linked polymers act as a viscoelastic matrix to provide mechanical strength, and as a fuel to react with the oxidizers present. Ammonium perchlorate and ammonium nitrate are the most common oxidizers used nitramines such as HMX or RDX may be added to react with the fuels and increase the impulse produced. Many other substances may be added including metallic fuels, plasticizers, stabilizers, catalysts, ballistic modifiers, and bonding agents. Typical components are Hsted in Table 1. 

Oxidizers. The characteristics of the oxidizer affect the baUistic and mechanical properties of a composite propellant as well as the processibihty. Oxidizers are selected to provide the best combination of available oxygen, high density, low heat of formation, and maximum gas volume in reaction with binders. Increases in oxidizer content increase the density, the adiabatic flame temperature, and the specific impulse of a propellant up to a maximum. The most commonly used inorganic oxidizer in both composite and nitroceUulose-based rocket propellant is ammonium perchlorate. The primary combustion products of an ammonium perchlorate propellant and a polymeric binder containing C, H, and O are CO2, H2, O2, and HCl. Ammonium nitrate has been used in slow burning propellants, and where a smokeless exhaust is requited. Nitramines such as RDX and HMX have also been used where maximum energy is essential. 

RocketPropella.nts, Liquid propellants have long been used to obtain maximum controUabiUty of rocket performance and, where required, maximum impulse. Three classes of rocket monopropellants exist that differ ia the chemical reactions that release energy (/) those consisting of, eg, hydrogen peroxide, ethylene oxide, C2H4O and nitroethane, CH2CH2NO2 that can undergo internal oxidation—reduction reactions (2) those... 

Oxygea difluoride is mainly a laboratory chemical. It has beea suggested as an oxidizer for rocket appHcations and has been used for small tests ia this area. 

Propellants and Explosives. Hydrazine fuels include anhydrous hydrazine (AH), monomethyUiydrazine (MMH), and unsymmetrical dimethyUiydrazine (UDMH) for military and space programs. These compounds are used mainly as bipropeUant fuels, ie, with oxidizers, in rockets such as the Titan, MX missile, and the Ariane (UDA4H7X30. Using oxygen or fluorine as the oxidizer, hydrazine is exceeded only by hydrogen in specific impulse, ie, kilograms of thmst developed for each kilogram of fuel consumed per second (196). 

Oxidizing Properties. Nitric acid is a powerful oxidizing agent (electron acceptor) that reacts violentiy with many organic materials (eg, turpentine, charcoal, and charred sawdust) (19,20). The concentrated acid may react explosively with ethanol (qv). Such oxidizing properties have had military appHcation nitric acid is used with certain organics, eg, furfuryl alcohol and aniline, as rocket propellant (see Explosives AND PROPELLANTS). 

Grade C, Type II is typical of Hquid oxygen used as a rocket propellant oxidizer. Particulate content is limited because of the critical clearances found in mechanical parts of the rocket engine. In addition to water, acetylene and methane are limited because, on long standing, oxygen evaporation could cause concentration of these combustible contaminants to reach hazardous levels. 

Because of the use of ammonium perchlorate as a soHd oxidizer for rocket propeUants, the thermal decomposition has been much studied (29—32). Three separate activation energies have been observed for AP decompositions an activation energy of 123.8 kJ/mol (29.6 kcal/mol) is found below 240°C of 79.1 kj/mol (18.9 kcal/mol) above 240°C and finally, of 307.1 kj/mol (73.4 kcal/mol) between 400—440°C (33,34). Below 300°C, the equation... 

Group 15 (VA) Perchlorates. Nitrogen perchlorates have been used as oxidizers in rocket propellants. Hydrazine perchlorate [13762-80-6] NH2NH2CIO4, and hydrazine diperchlorate, CIO4NH2NH2CIO4, have been investigated as oxidizers for propellant systems (60). Anhydrous salts can be... 

The perchloryl fluoride [7616-94-6] FCIO, the acyl fluoride of perchloric acid, is a stable compound. Normally a gas having a melting poiat of —147.7° C and a boiling poiat of —46.7°C, it can be prepared by electrolysis of a saturated solution of sodium perchlorate ia anhydrous hydrofluoric acid. Some of its uses are as an effective fluorinating agent, as an oxidant ia rocket fuels, and as a gaseous dielectric for transformers (69). 

The only a-ahoy of commercial importance is Ti—5A1—2.5Sn. This ahoy is weldable, has good elevated temperature stabhity and good oxidation resistance to about 600°C, and is used for forgings and sheet-metal parts, such as aircraft engine compressor cases because of its weldabhity. The ELI version of this ahoy is used in the cryogenic area of rocket engines. However, the ahoy is difficult to produce and has not been designed into more recent aerospace systems. 

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