Showing papers on "Propellant published in 1970"

A model of composite solid-propellant combustion based on multiple flames

Abstract: A model describing the combustion of AP composite propellants has been developed. The model is based on a flame structure surrounding individual oxidizer crystals; the relationship between crystals and the binder matrix being evaluated statistically. Three separate flame zones are considered: 1) a primary flame between the decomposition products of the binder and the oxidizer, 2) a premixed oxidizer flame, and 3) a final diffusion flame between the products of the other two flames. Simple global kinetics are assumed for gas-phase reactions, and the surface decomposition of the propellant ingredients is assumed to be adequately described by simple Arrhenius expressions. The oxidizer decomposition is taken as being the over-all controlling factor in the combustion process. The results obtained show that the calculated surface temperature and the effect of oxidizer concentration predicted by the model are in agreement with observed experimental trends. The predicted effect of particle size is somewhat greater than observed experimentally while the temperature sensitivity is in excellent agreement with experimental data. The results of the calculations indicate a relatively strong exothermic reaction taking place at the propellant surface. Apparently the ammonium perchlorate (AP) partially decomposes exothermically in the thin surface melt previously reported in AP deflagration studies.

Stability of Longitudinal Oscillations with Pressure and Velocity Coupling in a Solid Propellant Rocket

Abstract: Of the various unstable motions observed in solid propellant rocket chambers, the most troublesome currently are those involving oscillatory motions parallel to the axis. Such instabilities are found to arise particularly in larger rockets using propellants which contain aluminum. The problem is formulated here in one-dimensional form and solved for the case of small amplitude standing waves. Both pressure and velocity coupling may be accommodated, although the proper description of the response function for velocity coupling is not yet known. In addition to several special cases, the stability boundary is discussed for a straight chamber having variable cross section. The influences of the mean flow field, the nozzle, particulate matter, and motions of the solid propellant grain are taken into account.

Deflagration rate, surface structure, and subsurface profile of self-deflagrating single crystals of ammonium perchlorate

Abstract: Pure ammonium perchlorate single crystal self deflagration, determining energy transfer mechanisms from pressure effects, combustion characteristics and subsurface profile

Surface structure of ammonium perchlorate composite propellants

Abstract: Burning solid ammonium perchlorate composite propellants surface structure observation to assess heterogeneous or subsurface reactions, using scanning electron microscope

Solid gas generating and gun propellant composition containing triaminoguanidine nitrate and synthetic polymer binder

Abstract: Solid gas generating and gun propellant compositions employing triaminogudine nitrate as a propellant ingredient in admixture with an oxidant and a suitable compatible binder material

Solid gas generating and gun propellant compositions containing a nitroaminotetrazole salt

Abstract: Solid gas generating and gun propellant compositions which employ certain nitroaminotetrazole salts such as guanidinium 5-nitroaminotetrazole, ammonium 5-nitroaminotetrazole and hydrazinium 5-nitroaminotetrazole as modifying ingredients in admixture with an oxidant and a suitable compatible binder material.

Role of scanning electron microscopy in the study of solid propellant combustion. III - The surface structure and profile characteristics of burning composite solid propellants

Abstract: Composite solid propellants surface structure and profile characteristics burning with various oxidizers and polyurethane binder by scanning electron microscopy

Stabilization of Aerosol Emulsions and Foams

Abstract: Synopsis--It is proposed that the INTERFACIAL REGION around PROPELLANT droplets in AEROSOL EMULSIONS stabilized with MOLECULAR COMPLEXES is polymo~ lecular and consists of alternating layers of oriented water molecules and bimolecular layers of the molecular complex. The molecular complex has a LIQUID CRYSTAL STRUCTURE and, since it is almost insoluble in either the propellant or aqueous phase, concentrates at the interface and stabilizes the emulsion by forming essentially a solid interfacial fihn in somewhat the same way as finely divided iuorgauic solids. This hypothesis is based upon the evidence that molecular complexes have liquid crystal structures in aqueous systems and that almost all aerosol emulsions and FOAMS are stabilized by substances which are practically insoluble in both the aqueous and propellant phases.

A survey of current developments in surface tension devices for propellant acquisition

Abstract: T task of a propellant expulsion system is to supply gas-free propellant on demand to spacecraft thrusters for the duration of the mission. For orbital spacecraft, which may experience periods of adverse or near zero-gf accelerations, the expulsion system must assure that all or portions of the propellants are in contact with the tank outlet; that gas is prevented from entering the tank outlet during thruster startup; that pressurization gas entrained in the settling propellant bulk does not enter the tank outlet; and that propellant vortexing, gas pull-through, and propellant slosh do not significantly reduce the system expulsion efficiency. Many types of positive propellant expulsion systems have been developed for orbital spacecraft, each with advantages and problems, as summarized in Table 1. Development of these devices usually centers on. mechanical testing in simulated prototype environments. Although performance of these devices has been good, the reliability concern of the mission planner increases when very long missions are considered because there are no established accelerated life testing techniques. Recent experience with capillary systems has shown that they satisfy expulsion system requirements as well as the desire for passive simplicity. Indeed, the question of long-

Vehicle safety device having an inflatable confinement

Abstract: An apparatus for use in a safety system utilizing an inflatable confinement means, stored fluid under pressure, and a propellant charge for the generation of a hot gas. Means are provided for storing fluid under pressure which has a fluid outlet. A propellant chamber is provided for receiving an ignitable hot-gas generating charge of propellant. Means are provided to seal said chamber from said stored fluid. The arrangement is such that upon development of a predetermined chamber pressure after ignition of propellant, the chamber is unsealed and the fluid outlet is opened to permit the stored fluid and hot gas from the burning of the propellant to exit through the outlet. Means are provided between the chamber and the fluid outlet to deflect the hot gas upon exit from the chamber in a direction away from the fluid outlet to mix with the fluid prior to exit.

The Interaction of Thermal Radiation and M-2 Double-Base Solid Propellant

Abstract: This paper reports the results of experimental and theoretical investigations into the effects of thermal radiation upon ignition and deflagration of M-2 double-base solid propellant. The values of the heat of reaction, the frequency factor and the activation energy in the Arrhenius expression describing the chemical reactions in the solid are determined by matching the numerical solutions of the mathematical model with three sets of experimental data. The effect of thermal radiation upon the propellant is only thermal. Theoretically the effect of thermal radiation on the burning rate is shown to be equivalent to an increase in initial temperature of the propellant only when the radiation absorption coefficient is small. For M-2 propellant, thermal radiation has insignificant effect upon the burning rate for a range of fluxes from 0 to 1.5 cal/cm2-sec.

Gas-generating apparatus

Abstract: Gas generator having a folded inflatable bag connected thereto, the generator having a plurality of pockets confining propellant. Electrical ignition devices ignite the propellant in two pockets first to release gas for deploying or partially expanding the folded bag. Propellant filled channels connect the two initially ignited propellant pockets to the remaining pockets for igniting the latter to release gas for inflating the bag to a desired pressure. A sublimable, vaporizable or decomposable powdered material capable of absorbing heat is provided in the device to absorb the heat produced by the burning propellant.

Investigations of the T-burner and its role in combustion instability studies

Abstract: Of several devices introduced to study combustion instability in solid rocket propellants, one, known as the "T-burner," has become the most widely used. With this device the response of a burning propellant to a small pressure disturbance can be measured. Such information is vital both to the understanding of unsteady combustion processes as well as to the assessment of the stability characteristics of solid rocket motors. Although the T-burner has been used for several years, several questions concerning the device have arisen and, for the most part, have remained unanswered. Moreover, little effort has been given toward showing the relevance of T-burner data to predictions of instability in rocket motors. The present investigations, comprising over 400 test firings in T-burners of various lengths and diameters, were undertaken with the major objective of gaining a better understanding of the T-burner itself in order to answer some of these unresolved questions. Another objective was to compare T-burner predictions of rocket motor instability with actual observations made in a previous study. Among the investigations was a comparison of several ignition procedures which showed clearly that a poor, uneven ignition can seriously affect the test results. Included among the ignition studies were tests conducted in transparent chambers to permit high-speed motion photography of the firings. These tests confirmed the common assumption that the T-burner is basically a one-dimensional device. Tests using burners of different diameters showed that although the acoustic losses of the T-burner are nearly independent of diameter, the limiting amplitude of the oscillations is strongly dependent on the latter. The dilemma raised by these observations was resolved by measurements which indicate that the heat transfer from the combustion gases to the burner wall is strongly dependent on the amplitude of the waves. From these measurements emerged a nonlinear description of the damping in the T-burner which accounts for both the behavior of the losses as well as that of the limiting amplitude. When two independent T-burner methods were compared, the results obtained were initially in very poor agreement. However, when the T-burner losses were assumed to be non-linear as mentioned earlier, excellent agreement was observed. Finally, the T-burner predictions of instability in rocket motors were in rather poor agreement with direct observations made in a previous study. Although this lack of agreement is not understood, it is doubtful in the light of the present investigations that the major error lies in the T-burner measurements, for these should be relatively accurate. Moreover, these results indicate the need for more comparisons of this type in order to determine the usefulness of the T-burner in predicting combustion instability in solid propellant rockets.

Laser ignition system

Abstract: A device for firing ammunition has a chamber in which the propellant is placed, the chamber communicating with a barrel or guide through which is projectile or missile is propelled by the propellant when it is ignited, there being a window through which laser radiation can be directed onto the propellant in the chamber, the window pressure sealing the chamber when the chamber is closed.

Method for producing burnable gases for thrust engines

Abstract: Burnable gases under pressure for operating engines such as thrust engines and particular rocket and ramjet engines are produced by arranging together two solid propellant charges, one of which comprises an auxiliary propellant charge having a high thermal efficiency and the other constituting a main propellant charge comprising a material of low heat of fusion and evaporation. The auxiliary charge is ignited by a fuse device and will burn off adjacent the main charge but shielded therefrom by a burn-off insulation. The burnable gases which are produced are directed by their own pressure through a gas duct into a combustion chamber where they are admixed with an oxidizer which may be supplied under the pressure force of the gases themselves.

Theory of Radiant and Hypergolic Ignition of Solid Propellants

Abstract: A model is formulated for radiant ignition of a solid propellant, accounting for in-depth absorption of radiation and surface reaction between solid fuel and gaseous oxidizer. Mathematical solutions are obtained in the limit of infinite absorption coefficient. From calculated surface temperature histories, several ignition criteria are compared. Conditions are established under which the choice of ignition criterion influences ignition time; it is shown that ignition times based on constant ignition temperature can be greatly in error at high heating rates. From the dimensionless parametric solutions, dependence of ignition time on oxidizer concentration, pressure and other quantities is extracted. At low pressures and equal solid and gas temperatures, oxidizer mass fraction and pressure affect ignition time only through their effect on oxidizer concentration, but at high pressure or under shock-tube ignition conditions, the additional effect of pressure on transport properties becomes increasing...

Solid 5-aminotetrazole nitrate gas generating propellant with block copolymer binder

Abstract: A solid gas generating propellant based upon 5-aminotetrazole nitrate as the oxidant component and utilizing a binder matrix of a block copolymer selected from the group consisting of styrenebutadiene-styrene and styrene-isoprene-styrene.

Boron-fuel-rich propellant compositions

Abstract: Fuel-rich propellant compositions, for use in air-augmented rocket propulsion, containing a high-energy fuel component in the form of finely-divided boron, wherein the boron is present in large excess of the amount oxidizable during combustion of the propellant. A major portion of the boron is ejected, largely as free boron particles, together with the combustion products of the propellant and is burned downstream of the propellant by ram air injected into an afterburner combustion zone. The propellant additionally comprises an organic fuel binder comprising an organic polymer, and an inorganic oxidizer salt, preferably ammonium perchlorate, in an amount at least sufficient to maintain stable combustion of the propellant at desired combustion chamber pressures. The propellant compositions may additionally contain small amounts of Mg, Al, or Zr metal as ballistic or afterburner combustion modifiers. Ejection of the boron is substantially improved by incorporating at least a portion of the boron in the propellant composition in the form of agglomerate masses or particles. Preferably the agglomerate particles are spheroidal and the finely-divided boron in the agglomerate particles is bonded together by a matrix of an organic polymer. From 0 to 100% of the oxidizer salt is admixed with the boron in the agglomerate particles. Inclusion of the oxidizer with the metallic fuel in the agglomerate particles provides a substantial increase in propellant pressure exponent, which is highly desirable in certain applications. The Mg, Al, or Zr metal modifiers when present, may be incorporated wholly in the organic fuel binder, wholly in the agglomerate particles, or distributed therebetween.

An investigation of the acceleration induced burning rate increase of nonmetallized composite propellants

Abstract: A model is developed which correlates the experimentally observed burning rates of composite nonmetallized propellants subjected to acceleration fields normal to the burning surface. The model attributes the increased burning rates to additional energy transfer to the propellant surface from the combustion of ammonium perchlorate particles retained on the propellant surface by the acceleration forces. A method for predicting, with limited experimental data, the burning rate of a propellant as a function of pressure and acceleration is described.

Composite solid-propellant ignition by radiant energy

Abstract: Ignition characteristics of representative composite solid propellants were studied using an arc-imaging furnace to provide a radiant energy source. The variation of propellant ignitability with formulation changes was found to be small provided the binder and oxidizer were fixed. The minimum initial pressure for which ignition will occur appears to be predominantly determined by the thermal decomposition characteristics of the binder component in ammonium perchlorate-based propellants. It is proposed that a key step required to achieve ignition is the establishment of a critical gas-phase reaction rate threshold adjacent to the propellant surface.

An investigation of combustion instability in hybrid rockets

Abstract: A simple analysis has been developed to describe the transition of hybrid rocket combustion from the diffusion-limited region at high pressure to the kinetic-limited domain at low pressure. Good qualitative agreement has been obtained with measured regression rate behavior in those operating regimes where surface effects such as excessive melting or charring do not occur.

Processing of crosslinked nitrocellulose propellants

Abstract: This invention relates to an improved process for crosslinking of nitrocellulose with an isocyanate to form a polymeric binder for a solid propellant grain. Gassing of the propellant grain is prevented, and reproducible propellant grains, with substantially void free properties, and having improved mechanical properties, are prepared.

Safety bag inflation system for vehicles

Abstract: A system for inflating a safety bag in a vehicle upon a collision, wherein additional energy is supplied to a volume of pressurized gas stored in a reservoir, the additional energy being supplied by controlled combustion of a propellant charge to produce combustion gases which admix with the pressurized gas. The mixture of gases thus flows to the safety bag to inflate the latter. Energy produced by combustion of the propellant is also used to open a sealed flow path to the safety bag.

Dynamic stability of cylindrical propellant tanks

Abstract: Cylindrical propellant tanks dynamic stability and parametric resonance, analyzing axial preload, liquid depth, top impedance and ullage pressure by Donnell theory

Coaxial injector for reaction motors

Abstract: A coaxial injector particularly suited for use in mixing liquid propellants within combustion chambers of reaction motors, characterized by a first annular orifice, of a fixed dimension, adapted to deliver liquid oxidizer in an outwardly diverging conical sheet circumscribed by a second annular orifice, also of a fixed dimension, adapted to deliver an outwardly converging conical sheet of liquid fuel, whereby the sheets are caused to experience momentum exchange at an annular intersection for thereby developing a homogeneous mixture sheathed within a layer of a fuel-rich mixture for cooling the walls of the associated combustion chamber, a feature of the injector being an integration of injector components into an all-welded, unitary structure having empirically established propellant mixing characteristics.

Numerical analysis of low-g propellant flow problems

Abstract: Numerical analysis of low-g fluid flow and heating problems encountered with liquid propellant storage and supply

Sodium azide gas generating solid propellant with fluorocarbon binder

Abstract: Gas generating solid propellant compositions which utilize sodium azide as a nitrogen source and are further comprised of a fluorocarbon binder material and a combustion catalyst of finely divided colloidal silicon dioxide and/or finely divided carbon black.

Strand size and low-pressure deflagration limit in a composite propellant

Abstract: The low-pressure deflagration limit, LPDL, has been determined for a composite ammonium perchlorate propellant over a range of pressures from 35 to 235 torr The independent variable was strand cross section area A linear relation was found between the LPDL and the inverse of the "hydraulic radius" of the strand It was thus possible to extrapolate and determine the low-pressure limit for a strand of infinite extent It can be argued that such an infinite strand is adiabatic A possible mechanism to explain a finite extinguishing pressure for an adiabatic strand is the lack of sufficient oxidant in the gas phase due to differences in the rate of change of fuel and oxidizer gasification rates with decreasing pressure I Introduction S OME time ago we attempted to examine the structure of the combustion zone above a strand of composite solid propellant by means of interferometry In order to increase spatial resolution we expanded the zone by burning propellant strands at subatmospheri c pressure in a chamber which could be continuously pumped and which was provided with windows for observation For reasons that we probably should have anticipated we fell somewhat short of our primary objective In the course of our experiments, however, we did obtain some data on the low-pressure deflagration limit, LPDL, for two composite propellant compositions In particular, we determined the dependence of LPDL on strand size It seems in order to record these results because they may provide some grist for the theorist's mills and shed

Reversible-emulsion aerosol system

Abstract: A PRESSURIZED WATER-IN-OIL EMULSION WHICH REVERSES TO A STABLE OIL-IN-WATER EMULSION AND CAN FOAM A FINITE TIME AFTER DISCHARGE FROM AEROSOL CONTAINER, COMPRISING TWO IMMISCIBLE LIQUIDS IN EMULSIFIED FORM, SAID EMULSION HAVING WATER IN THE DISPERSED PHASE, AND PROPELLANT BEING THE CONTINUOUS PHASE.