Begell House Inc.
International Journal of Energetic Materials and Chemical Propulsion
IJEMCP
2150-766X
9
4
2010
RADIATIVE IGNITION OF SOLID PROPELLANTS: A PRACTICAL APPROACH
285-304
10.1615/IntJEnergeticMaterialsChemProp.v9.i4.10
Franck
Cauty
ONERA
Yves
Fabignon
ONERA−The French Aerospace Lab, Palaiseau, France
Charles
Erades
ONERA−The French Aerospace Lab, Palaiseau, France
composite propellant
ignition model
radiative ignition
IR pyrometer
ignition delay
We were interested in studying solid propellant time-to-ignition determination from two perspectives. First, we experimentally determined the sensitivity of composite propellants to ignition by using CO2 laser radiation instead of the classical convective heat generator used at Onera for many decades. Second, we validated the propellant degradation data using a one-dimensional (1D) simulation model based on a classical relationship set. The setup and the associated measurement systems are described in detail in this paper. High-speed video images were obtained, and surface luminance temperature evolutions from optical-fiber pyrometers were determined. The results showed the inert heating of the sample, then the start of binder degradation, and upon ignition of a first ammonium perchlorate (AP) grain ("first light"), rapid rise of temperature to the stationary combustion level. We comment on the different ignition delay times corresponding to criteria and the physical process of the AP propellant grain ignition. The first AP grain large enough to propagate heat to other grains around it, and close enough to the surface, is the starting element of the ignition process. These experimental results were then compared to a 1D numerical simulation model. The solid propellant thermal and reaction parameters were determined from the literature values of the ingredients [AP, hydroxyl terminated polybutadiene (HTPB), and aluminum (Al)] and their mixture ratio. The model gives the surface temperature evolution and the burning rate variation from 0 to the stationary value. The experimental and numerical results showed that the pre-exponential factor of the Arrhenius law governs the delay time and the ignition surface temperature level.
RECENT ADVANCES IN HYBRID PROPULSION
305-326
10.1615/IntJEnergeticMaterialsChemProp.v9.i4.20
Brian
Cantwell
Stanford University and Space Propulsion Group, Incorporated, Sunnyvale, California
Arif
Karabeyoglu
Stanford University and Space Propulsion Group Inc., 39120 Argonaut Way, Fremont, California 94538, USA; Koç University, Rumeli Feneri Yolu, Sariyer, Istanbul, 34450, Turkey
David
Altman
Stanford University and Space Propulsion Group, Incorporated, Sunnyvale, California
rocket
hybrid
propulsion
paraffin
fuel
oxidizer
combustion
entrainment
The idea of the hybrid rocket is to store the oxidizer as a liquid and the fuel as a solid, producing a design that minimizes the chance of a chemical explosion. While the hybrid enjoys many safety and environmental advantages over conventional systems, large hybrids have not been commercially viable. The reason is that traditional systems use polymeric fuels that evaporate too slowly, making it difficult to produce the high thrust needed for most applications. Research at Stanford University and Space Propulsion Group (SPG) has led to the development of paraffin-based fuels that burn at regression rates 3-4 times that of polymeric fuels. Under the action of the oxidizer flow, the new fuels form a thin, hydrodynamically unstable liquid layer on the melting surface of the fuel. Entrainment of droplets from the liquid-gas interface can substantially increase the rate of fuel mass transfer, leading to a much higher surface regression rate than can be achieved with a conventional fuel. To demonstrate the use of these fuels, a series of scale-up tests using several oxidizers has been carried out on intermediate-scale motors. The data from these tests are in agreement with small-scale, low- pressure, and low-mass-flux laboratory tests and confirm the high regression rate behavior of the fuels at chamber pressures and mass fluxes representative of commercial applications. Recently, SPG has developed a new class of oxidizers based on refrigerated mixtures of N2O and oxygen. The mixtures combine the high vapor pressure of dissolved oxygen with the high density of refrigerated N2O to produce a self-pressurizing oxidizer with high density and good performance. The combination of these technologies leads to a hybrid rocket design with reduced system size and mass.
HIGH-FIDELITY PREDICTIONS OF THE EFFECTS OF PRESSURE AND PARTICLE SIZE ON AMMONIUM PERCHLORATE/HYDROXY- TERMINATED-POLYBUTADIENE PROPELLANTS
327-339
10.1615/IntJEnergeticMaterialsChemProp.v9.i4.30
Matthew L.
Gross
Naval Air Warfare Center, Weapons Division, China Lake, California 9355-6100 USA
Ephraim B.
Washburn
Naval Air Warfare Center, Weapons Division, China Lake, California 93555, USA
Merrill W.
Beckstead
Brigham Young University, Provo Utah USA
ammonium perchlorate
solid propellants
combustion modeling
energetic materials
flame structure
The complexities of the flame structure above an ammonium perchlorate (AP) and hydroxy- terminated-polybutadiene (HTPB) composite propellant have been elucidated, using a two- dimensional, detailed kinetic model. The model utilizes a vorticity formulation of the transport equations and includes mass and energy coupling between the condensed and gas phases, and a detailed gas-phase kinetic mechanism consisting of 37 species and 127 reactions. Numerical studies have been performed to examine particle-size and pressure effects on the flame structure above an AP/HTPB surface. The combination of AP with a binder/fuel results in a significantly enhanced burning rate relative to monopropellant AP, and this effect increases as AP particle size decreases. The modeled flame structure was found to be qualitatively similar to the Beckstead-Derr-Price (BDP) model. Three different combustion zones were predicted based on particle size: the AP monopropellant limit, the diffusion flame region, and the premixed limit. Calculations varying pressure further illustrate the dynamic nature of AP propellant combustion; as pressure increases, the premixed cutoff size decreases. Results are consistent with experimental observations and provide mechanistic insights into AP's unique combustion properties. Calculations show promise in predicting formulistic effects using high-fidelity models.
DETONATION CHARACTERISTICS OF NITROMETHANE DILUTED WITH NONEXPLOSIVE LIQUIDS
341-350
10.1615/IntJEnergeticMaterialsChemProp.v9.i4.40
Sergey Alekseevich
Koldunov
Institute of Problems of Chemical Physics RAS, Russian Federation
Alexander Victorovich
Ananin
Institute of Problems of Chemical Physics RAS, Russian Federation
detonation
liquid mixtures
concentration limit
electromagnetic method
This paper presents the results of an investigation of binary mixtures of nitromethane as a detonability liquid with the addition of the nonexplosive liquid ingredients methanol and nitrobenzene. An electromagnetic method for the registration of the particle velocity profile was applied. The record of detonation wave profiles with typical von Neumann spike enabled the determination of the Chapman-Jouguet state and the definition of a sufficient set of detonation characteristics. The detonation product pressure dependencies relative to the concentration of nonexplosive ingredients were obtained. The differences in the natures of the diluents became apparent in the degree of reduction of the detonation parameters when the percentage of nonexplosive liquid was increased. Some disagreements with the one-dimensional hydrodynamic detonation theory were noted.
CHARACTERIZATION AND COMPARISON OF TWO HYDROXYL-TERMINATED POLYETHER PREPOLYMERS
351-364
10.1615/IntJEnergeticMaterialsChemProp.v9.i4.50
Rodrigo
Caro
Quinetic SpA
John M.
Bellerby
Department of Applied Science, Security and Resilience, Cranfield University Defense Academy, Shrivenham, Swindon SN6 8LA
HTPE
IM
insensitive munitions
prepolymers
rocket propellant hinder
Composite rocket propellants with improved insensitive munitions (IM) characteristics can be produced using cross-linked hydroxyl-terminated polyether (HTPE) binders and are potential alternatives to hydroxyl-terminated polybutadiene (HTPB) compositions. Some characteristics of propellants based on the HTPE binder have been presented, but there has been no report on the comprehensive chemical characterization of the prepolymer. In this paper we report a preliminary study on the characterization and comparison of two different HTPE prepolymers, one synthesized in our laboratory and the other obtained from a commercial source. Analyses were carried out on the two materials to determine molecular weight, molecular structure, glass transition temperature (Tg), melting temperature (Tm), impurities, and viscosity. These properties were determined using a range of techniques, including size-exclusion chromatography (SEC), nuclear magnetic resonance (NMR) spectroscopy, differential scanning calorimetry (DSC), gas chromatography-mass spectrometry (GC-MS), and Fourier transform infrared (FTIR) spectroscopy.
REDUCTIVE DEBENZYLATION OF 2,4,6,8,10,12-HEXAAZAISQWURTZITANE
365-375
10.1615/IntJEnergeticMaterialsChemProp.v9.i4.60
Sergey V.
Sysolyatin
Institute for Problems of Chemical and Energetic Technologies, Siberian Branch,
Russian Academy of Sciences, Biysk, Altaikrai, Russia
Alexander I.
Kalashnikov
Institute for Problems of Chemical and Energetic Technologies of the Siberian Branch of the Russian Academy of Sciences, Biysk
Valeriy
Malykhin
Institute for Problems of Chemical and Energetic Technologies, Siberian Branch,
Russian Academy of Sciences, Biysk, Altaikrai, Russia
Irina A.
Surmacheva
Institute for Problems of Chemical and Energetic Technologies of the Siberian Branch of the Russian Academy of Sciences, Biysk
Gennady V.
Sakovich
Institute for Problems of Chemical and Energetic Technologies of the Siberian Branch of the Russian Academy of Sciences, Biysk
catalytic hydrogenolysis
debenzylation
hexaazaisowurtzitane derivatives
product composition
catalyst reuse
A high-pressure liquid chromatography-mass spectroscopy (HPLC-MS) study of the product composition from the catalytic hydrogenolysis of 2,4,6,8,10,12-hexabenzyl-2,4,6,8,10,12-hexaazaisowurtzitane (HBIW) and 4,10-dibenzyl-2,6,8,12-tetraacetyl-2,4,6,8,10,12-hexaazaisowurtzitane (DBTA) was undertaken. The hydrogenolysis of HBIW is observed in all possible directions. Debenzylation of DBTA in formic acid results in forming the mixture of 4,10-diformyl-2,6,8,12- tetraacetyl-2,4,6,8,10,12-hexaazaisowurtzitane (DFTA), 4-formyl-2,6,8,12-tetraacetyl-2,4,6,8,10,12- hexaazaisowurtzitane (FTA), and 2,6,8,12-tetraacetyl-2,4,6,8,10,12-hexaazaisowurtzitane (TA), the contents of which depend on the CHOOH concentration. In aqueous solutions of formic acid the process is complicated by hydrolysis of the amide groups. Some of the hydrolysis products keep the structure of 2,4,6,8,10,12-hexaazaisowurtzitane. Debenzylation of DBTA in mixtures of formic/acetic, formic/propionic, or formic/iso-butyric acids leads to the same mixed products. The procedure of palladium catalyst reuse in the two-stage reductive debenzylation of HBIW was developed and is presented.