Strand Burning Rate Research Articles

High Volumetric Specific Impulse Composite Propellant Based on Terminally Functionalized Block Copolymers of Polybutadiene and ϵ‐Caprolactone

AbstractFor enhanced range, higher payload capacities and for miniaturized propulsion systems, today's strategic and tactical weapon system designers demand for higher density and specific impulse of the propellant. In order to enhance the density impulse of HTPB/DOA/RDX/AP/Al based composite propellant, studies have been carried to replace conventional HTPB/DOA binder system with hydroxyl terminated block copolymer of polybutadiene and ϵ‐caprolactone with NG as plasticizer. Total eight numbers of compositions were formulated with varying content of RDX. Both binder systems were compared in propellant compositions by evaluating various physical, thermal and ballistic properties. Various rocket performance parameters of each formulation were theoretically predicted by NASA CEC‐71 program and burning rate was measured in pressure ranges of 3‐7 and 7‐11 MPa by the acoustic emission technique. In addition, density, viscosity build up, calorimetric values, thermal decomposition and sensitivity parameters of each composition were also assessed and compared. In an outcome, it was concluded that HTBCP25/NG based propellant compositions enhance the density by 4.4–5 % and calorimetric values by 12–15 % as compared to HTPB/DOA based compositions. Strand burning rate data show enhancement of burning rate by 40–70 % at 7 MPa pressure in HTBCP25/NG based compositions. Impact and friction sensitivity data also revealed their utility in propellant compositions for future applications.

Effects of Nano-Sized Al on the Combustion Performance of Fuel Rich Solid Rocket Propellants

Several industrial- and research – type fuel rich solid rocket propellants containing nano-metric aluminum metal particles, featuring the same nominal composition, were prepared and experimentally analyzed. The effects of nano-sized aluminum (nAl) on the rheological properties of metal/HTPB slurries and fuel rich solid propellant slurries were investigated. The energetic properties (heat of combustion and density) and the hazardous properties (impact sensitivity and friction sensitivity) of propellants prepared were analyzed and the properties mentioned above compared to those of a conventional aluminized (micro-Al, mAl) propellant. The strand burning rate and the associated combustion fl ame structure of propellants were also determined. The results show that nAl powder is nearly “round” or “ellipse” shaped, which is different from the tested micrometric Al used as a reference metal fuel. Two kinds of Al (nAl and mAl) powder can be dispersed in HTPB binder suffi ciently. The density of propellant decreases with increasing mass fraction of nAl powder; the measured heat of combustion, friction sensitivity, and impact sensitivity of propellants increase with increasing mass fraction of nAl powder in the formulation. The burning rates of fuel rich propellant increase with increasing pressure, and the burning rate of the propellant loaded with 20% mass fraction of nAl powder increases 77.2% at 1 MPa, the pressure exponent of propellant increase a little with increasing mass fraction of nAl powder in the explored pressure ranges.

EFFECTS OF CL-20 ON THE PROPERTIES OF GLYCIDYL AZIDE POLYMER (GAP) SOLID ROCKET PROPELLANT

The microstructures and granularity distributions of HMX and CL-20 particles were analyzed. Three industrial and research-type GAP-based solid propellants containing CL-20 particles, featuring the same nominal composition, were prepared and experimentally tested. The effects of CL-20 particles on the rheological properties, energetic properties, and the hazardous properties of GAP-based solid propellants were investigated. The properties mentioned above were also compared to those propellants containing HMX. Also, the strand burning rate and the associated combustion properties of propellants were determined. It turned out that the GAP-based propellants containing CL-20 particles can be prepared and cast safely. GAP-based propellants containing CL-20 particles are more sensitive to impact and friction compared to propellants with HMX. However, the addition of CL-20 particles to the propellant formulation can increase the burning rate and affect the combustion behavior, when compared to the reference propellant.

Effects of Different Nano-Sized Metal Oxide Catalysts on the Properties of Composite Solid Propellants

ABSTRACTSeveral industrial- and research-type composite solid propellants containing different nano metric metal oxide catalysts (Fe2O3, Co3O4, CuO, and PbO) with similar nominal composition, were prepared and experimentally analyzed. The effects of different nano-sized metal oxide catalysts on the rheological properties and hazardous properties were investigated. The strand burning rate and the associated combustion flame structure of composite propellants were determined. The results show that the nano-sized metal oxide powders can be sufficiently dispersed in hydroxyl terminated polybutadiene binder. The propellant formulations containing nano metal oxide particles are sensitive to impact and friction except for the base propellant without nano-sized powders, which is less sensitive to friction as compared to the other compositions. The nano-sized metal oxide additives can affect the combustion behavior and increase the burning rate of propellants compared with the reference propellant composition.

Effects of Different Nano‐Metric Particles on the Properties of Composite Solid Propellants

AbstractSeveral industrial‐ and research‐type composite solid propellants containing different nano‐metric metal particles (such as aluminum, zirconium and titanium) with similar nominal composition, were prepared and experimentally analyzed. The effects of different nano‐metric powders on the rheological properties for metal/HTPB slurries and AP‐based composite propellant slurries were investigated. The strand burning rate and the associated combustion flame structure of propellants were determined. The energetic properties and the hazardous properties of propellants prepared were analyzed and the properties mentioned above were compared to those of a conventional aluminized propellant. The results show that aluminum powder can be sufficiently dispersed in HTPB binder. The propellant formulations containing nano‐metric particles are sensitive to impact and friction except for the base propellant with common aluminum powder, which is less sensitive to friction as compared to the other compositions. The nano‐metric additives can affect the combustion behavior and increase the burning rate of propellants compared with the common one (the reference propellant composition).

Erosive and strand burning of stick propellants. I - Measurements ofburning rates and thermal-wave structures

Burning-rate characteristics and thermal-wave structures of NOSOL-363 stick propellant under erosiveand strand-burning conditions were studied using a real-time x-ray radiography system, a strand burner setup, and fine-wire thermocouples. For the erosive-burning rate measurements, locations of instantaneous burning surfaces along the center perforation of a cylindrical propellant grain were determined by comparison of x-ray images obtained during a test and calibration images. The burning rates under strong crossflow conditions, deduced from the instantaneous burning-surface locations, were found to be much higher (up to 2.5 times) than the strand-burning rate of NOSOL-363 stick propellant. This study demonstrated that real-time x-ray radiography is a powerful and reliable tool for nonintrusive measurements of instantaneous burning rates in an optically opaque test chamber. From the strand-burning rate data and thermal-wave structures, a set of important thermochemical properties of NOSOL-363 stick propellant was deduced.

Mects of Low-Temperature Ammonium Perchlorate Decomposition on the Ballistic Properties of a CTPB Propellant

The objective of the subject work was to characterize the effect of the low-temperature condensed-phase decomposition (LTD) of ammonium perchlorate (AP) on the ballistic properties of a CTPB propellant. Propellants were prepared from three chemically altered AP oxidizers, differing widely in initial LTD rate, but having essentially identical particle size distributions. Other physiochemical properties of the propellants were maintained constant during processing. The three oxidizers were as follows, in order of increasing initial LTD rate: 1) AP cocrystallized with (NH4)2 HPO4, 2) recrystallized control, and 3) AP cocrystallized with KC1O3. Experimental evidence is cited for the probable absence of phosphate-induced catalysis of the high-temperature decomposition of AP. Despite a demonstrated tenfold spread in isothermal LTD weight loss rates of the special oxidizers used in the three propellants, these differences had no measurable effects on strand burning rate, critical P extinction characteristics, low-pressure deflagration limit, burning-rate temperature sensitivity, or ignition delay time.

A novel chemical system for generation of electron-rich gases

A unique, self-oxidized combustion system, consisting initially of a solid mixture, is described which burns to yield an all-gas plasma containing over 1015 (measured) or 1016 (calculated) electrons/cm3 at atmospheric pressure. The ingredients are tetracyanoethylene, hexanitroethane, and cesium azide, formulated to be stoichiometric to CO, N2, and Cs. The mixture is compacted to 1.6 gm/cm3 by pressing at 20,000 psi. The strand burning rate at 1 atm is 1.3 mm/sec and the pressure exponent is about 0.6 The flame temperature, calculated as 3660°K, was measured as 3520°K by the spectral-line-intensity method and 3000°–3100°K by the line-reversal method. In view of the radial nonuniformity of the plasma, the former value is considered more likely to be correct. Electron densities were determined both from measurements of individual spectral-line shapes (Stark-broadening) and by the Inglis-Teller series limit method. The two methods agreed with one another. Strands of 1.27-cm diam gave three or four times higher electron concentrations than strands of 0.79-cm diam; however, electron concentrations, while extremely high, were still below calculated values, even after the lowering of flame temperature below theoretical (because of heat loss) was considered. We believe that adequate time was available for cesium ionization, under our experimental conditions, but time was not adequate for complete oxidation of CN and CN− to CO and N2, so electrons were largely attached as CN− rather than free. Hence, longer residence times allowing a closer approach toward equilibrium should give even higher yields.