This paper presents an analysis of the observed combustion behavior of AN mixtures with different additives, fuels, and energetic materials. It has been determined on the basis of flame structure investigation by fine tungsten-rhenium thermocouples that the surface temperature of AN is controlled by the dissociation reaction of the salt occurring at the surface. Results obtained have indicated that the leading reaction of combustion of AN doped with additives proceeds in the condensed phase up to pressures of 20 -30 MPa. A reason for the inability of pure AN to burn is suggested and the role of additives in the combustion mechanism is discussed.

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Burn rate studies have been carried out on dinitramide salts of common formula of L-nHN(NO 2 )2, where n = 1 or 2; L = methylamine, guanidine, aminoguanidine, ethanolamine, diethanolamine, ethylenediamine, hexamethylenediamine, aniline, 3-nitroaniline, 2-toluidine, benzylamine, morpholine, piperazine, 3,5-dimethylpyridine, and 5-aminotetrazole. A specific region on the burning rate-pressure dependence characterized by either reduced pressure exponent or combustion instability has been found to be a peculiar feature of the combustion of most of the salts. Nevertheless, a comparison with similar salts of perchloric acid shows more stable combustion of dinitramide salts on the whole. All dinitramide salts including ADN have been concluded to have a common combustion mechanism which involves the condensed-phase reaction to give N 2 O and the corresponding nitrate and determines the burning rate at low pressures. Certain of the combustion peculiarities of dinitramide salts may be expected to be characteristic of ADN-based compositions too, with the obtained results useful in searching for approaches to prevent combustion instability. IntroductionAmmonium salt of dinitramide (ADN) is currently considered as one of the most promising substitute for the main oxidizer of composite propellants, ammonium perchlorate (AP) 1 ' 2 -3 . Unquestionable advantages of ADN over AP manifest themselves in possibility to produce higher-energy propellant compositions with no HC1 in the combustion products, what is very important from ecological standpoint. The use of ADN as a solid propellant oxidizer assumes a knowledge of combustion characteristics of both ADN itself and its mixtures with fuels. Investigations in mis field indicate that combustion behavior of ADN differs essentially from that of AP 4> 5 .At present a lot of organic derivatives of dinitramide have been synthesized and published 6 . Study of burning behavior of these compounds is believed to allow revealing not only combustion mechanism of dinitramide salts, their place among other energetic materials, but also elucidating combustion peculiarities of ADN-based mixtures if being considered as model compositions of molecular level of oxidizer-fuel premixing.

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