Showing papers on "Propellant published in 1991"

Operational characteristics of the thermally choked ram accelerator

Abstract: Operational characteristics of the thermally choked ram accelerator, a ramjet-in-tube device for accelerating projectiles to ultrahigh velocities, are investigated theoretically and experimentally. The projectile resembles the centerbody of a conventional ramjet and travels through a stationary tube filled with premixed gaseous fuel and oxidizer at high pressure. The combustion process travels with the projectile, its thermal choking producing a pressure field which results in thrust on the projectile. The results of experiments with 45-75 gm projectiles in a 12.2 m long, 38 mm bore accelerator, using methane-based propellant mixtures, are presented in the velocity range of 1150-2350 m/s. Acceleration of projectiles with staged propellants and transitions between different mixtures are investigated and the velocity limits in several propellant mixtures are explored. Agreement between theory and experiment is found to be very good.

Device for delivering an aerosol

Abstract: A device for delivering an aerosol, comprising: a casing member (14), a valve stem (12), and a diaphragm (16), wherein the diaphragm comprises a thermoplastic elastomer comprising an ethylene/1-butene copolymer. Also disclosed are sealing members comprising such an elastomer and thermoplastic polymer blends, e.g., for use in sealing members of the invention. The devices of the invention are particularly useful with formulations containing 1,1,1,2-tetrafluoroethane or 1,1,1,2,3,3,3-heptafluoropropane as the propellant.

Liquid propellant inflator for vehicle occupant restraint apparatus

Abstract: To deploy an inflatable member, such as an occupant restraint safety bag in a motor vehicle, a liquid propellant is expelled from a storage reservoir into a reaction chamber through ports created at frangible pressure points in the reservoir wall and ignited by detonation of an explosive charge to generate a non-toxic, bag inflating gas by exothermic reaction

Experimental investigation of ram accelerator propulsion modes

Abstract: Experimental investigations on the propulsive modes of the ram accelerator are reviewed in this paper. The ram accelerator is a ramjet-in-tube projectile accelerator whose principle of operation is similar to that of a supersonic air-breathing ramjet. The projectile resembles the centerbody of a ramjet and travels through a stationary tube filled with a premixed gaseous fuel and oxidizer mixture. The combustion process travels with the projectile, generating a pressure distribution which produces forward thrust on the projectile. Several modes of ram accelerator operation are possible which are distinguished by their operating velocity range and the manner in which the combustion process is initiated and stabilized. Propulsive cycles utilizing subsonic, thermally choked combustion theoretically allow projectiles to be accelerated to the Chapman-Jouguet(C-J) detonation speed of a gaseous propellant mixture. In the superdetonative velocity range, the projectile is accelerated while always traveling faster than the C-J speed, and in the transdetonative regime (85–115 % of C-J speed) the projectile makes a smooth transition from a subdetonative to a superdetonative propulsive mode. This paper examines operation in these three regimes of flow using methane and ethylene based propellant mixtures in a 16 m long, 38 mm bore ram accelerator using 45–90 g projectiles at velocities up to 2500 m/s.

Extrudable gas generating propellants, method and apparatus

Abstract: A stable extrudable non-azide crash bag propellant composition for generating high quality nitrogen gas and a low temperature process for producing the same from an extrudable mass containing an effective amount of a cellulose-based binder.

Methods for manufacturing foamable metal bodies

Abstract: A method is described for manufacturing foamable metal bodies in which a mixture (17) of a metal powder (15) and a gas-splitting propellant powder (16) is hot-compacted to a semifinished product (19) at a temperature at which the joining of the metal powder particles takes place primarily by diffusion and at a pressure which is sufficiently high to hinder the decomposition of the propellant in such fashion that the metal particles form a solid bond with one another and constitute a gas-tight seal for the gas particles of the propellant. The foamable metal body can also be produced by rolling. In addition, a use of the foamable metal body (19) thus produced for manufacturing a porous metal body (21) is proposed.

Implantable infusion pump

Abstract: The invention concerns an infusion pump with a flexible medication container (10), a chamber (12) containing a CFC propellant gas which acts on the medication container, and a capillary tube (14) which acts as a choke. The invention calls for the propellant-gas chamber to be designed to accommodate a pressure of more than 2.5 bar over atmospheric and the propellant gas to be 1,2-dichlorotetrafluoroethane (C2Cl2F4).

Molecular structure of the ideal solid propellant binder

Abstract: A study has been conducted to investigate the relationship between binder molecular structure and the mechanical/rheological properties of solid propellants. Beginning with the mechanical property requirements dictated by the motor grain operating conditions as well as rheological constraints imposed by available processing technology, the approach taken was to work backwards to obtain the ideal molecular structure of a solid propellant binder. Structural/processing requirements were determined from the demands of three typical rocket motor applications: space transfer, launch vehicle/ballistic missile, and tactical air-to-air. Three general formulation approaches to meet the demands of these applications were considered. These include traditional composite and nitrate ester plasticized formulation approaches, in addition to a hypothetical all-binder propellant. For each of these three formulation approaches, a variety of polymer molecular characteristics were defined in terms of molecular weight, crosslink density, solubility parameter, chain stiffness, monomeric friction coefficient, volume fraction filler, and volume fraction plasticizer. Characterization data for ten polymeric binder systems are reported to show how their molecular architecture influences the resulting propellant properties.

Acoustic Boundary Layers in Solid Propellant Rocket Motors Using Navier-Stokes Equations

Abstract: The numerical solution of laminar, two-dimensional, compressible, and unsteady Navier-Stokes equations is aimed at a complete description of acoustic boundary layers that develop above a burning pro pell ant. Such acoustic boundary layers can be responsible for the so-called flow turning losses. They can govern the local unsteady flow conditions that are seen by the burning propellant to which it finally responds. In those respects, a complete understanding of such acoustic boundary layers is essential to improve existing solid rocket stability prediction codes. The full numerical solution of the Navier-Stokes equations incorporates into the analysis all the features of two-dimension al rocket chamber mean flowfield in a natural manner. After a standing wave pattern is established through forcing at a given frequency, a special Fourier treatment is used to transform the numerical results in a form directly comparable to available linear acoustic data. The presented results indicate that the acoustic boundary layer is substantially thinner than predicted by simplified models. Moreover, its acoustic admittance is found to vary significantly along the chamber, a result that is of major importance to stability predictions. Finally, the acoustic field is found to be rotational over a significant volume of the chamber.

Non-azide gas generant formulation, method, and apparatus

Abstract: Gas generating compositions or propellants are provided which comprise a non-azide fuel which is a transition metal complex of an aminoarazole Preferred transition metal complexes are zinc and copper complexes of 5-aminotetrazole and 3-amino-1,2,4-triazole, with the zinc complexes most preferred The propellant compositions also include a conventional oxidizer, such as potassium nitrate or strontium nitrate These compositions are useful for generating a nitrogen-containing gas for a variety of applications, especially for inflating air bags in automotive restraint systems, as well as other inflatable devices

Experimental investigation of velocity coupling in combustion instability

Abstract: An investigation has been conducted of the velocity coupling phenomenon reported in acoustically unstable solid-propellant rocket motors. An innovative simulation facility has been built using solid carbon dioxide as the simulated propellant. Acoustic disturbances are introduced over the dry-ice surface by means of a mechanically driven piston. Experiments have been conducted with dry ice located near both a velocity antinode and a velocity node. Mass flow rate and acoustic pressure measurements indicate the existence of a coupling mechanism, strongly dependent on the acoustic velocity amplitude, between the acoustic disturbance and the dry-ice sublimation process. Flow visualization and hot-film anemometry both show that the flow is turbulent near resonance. Transition to turbulence near a velocity node appears to occur at a smaller critical acoustic velocity amplitude than that near a velocity antinode. Some preturbulent instability has also been observed. Acoustically induced, turbulent forced convection is believed to be responsible for the increase in the sublimation rate of the dry ice (simulated burning of the propellant). Turbulence is believed to be one of the principal mechanisms in the velocity coupling phenomenon. An empirical correlation was developed which appeared to apply to the real propellant cases.

Effect of Boron Particle Surface Coating on combustion of solid propellants for ducted rockets

Abstract: Combustion behavior of B/MA/AP/HTPB fuel rich propellants containing different coated boron particles was studied with several diagnostic facilities such as windowed strand burner, CO2 laser ignition facility, rapid depressurization quenched device, thermal analyzer and micromotor static test. Materials selected for boron coating include LiF, Viton A and silane. Baseline propellant containing uncoated boron was also studied for comparison Results from windowed strand burner and static test show that LiF-propellant exhibits the most remarkable overall behavior. Ignition study indicates that LiF-propellant gives the shortest while Viton A-propellant gives the longest ignition time under the same heat flux. Moreover, mechanisms were proposed to elucidate the experimental results and the observed combustion phenomena.

Response of gravity level fluctuations on the Gravity Probe-B spacecraft propellant system

Abstract: Time-dependent computations have been performed to investigate the dynamical behaviors of fluid under a microgravity environment. A computer algorithm is introduced which can be used to simulate the fluid behavior in that environment, in particular the excitation of sloshing waves due to different gravity environments and rotation speeds. A suggestion on the proper handling and managing of cryogenic fluid propellant to be used in the Gravity Probe-B spacecraft propulsion is made.

Reorientation of Rotating Fluid in Microgravity Environment With and Without Gravity Jitters

Abstract: In a spacecraft design, the requirements of settled propellant are different for tank pressurization, engine restart, venting, or propellant transfer. The requirement to settle or to position liquid fuel over the outlet end of the spacecraft propellant tank prior main engine restart poses a microgravity fluid behavior problem. In this paper, the dynamical behavior of liquid propellant, fluid reorientation, and propellant resettling have been carried out through the execution of supercomputer CRAY X-MP to simulate the fluid management in a microgravity environment. Results show that the resettlement of fluid can be accomplished more efficiently for fluid in rotating tank than in nonrotating tank, and also better performance for gravity jitters imposed on fluid settlement than without gravity jitters based on the amount of time needed to carry out resettlement period of time between the initiation and termination of geysering.

Space electric propulsion plasmas

Abstract: Electric thrusters offer the promise of a substantial improvement in performance over that of conventional chemical rockets currently used in space propulsion applications. There are three basically different ways in which electrical power and propellant inputs might be combined to produce thrust: (1) propellant can be heated electrically and then expanded through a nozzle; (2) electromagnetic body forces can be applied to accelerate a plasma to the desired exhaust velocity; or (3) electrostatic body forces can be applied to accelerate charged particles. Electric thrusters are classified in accordance with the mechanism by which they induce thrust as electrothermal, electromagnetic, and electrostatic. The characteristics of plasmas in electric thrusters along these lines are considered. >

Launch vehicle performance using metallized propellants

Abstract: Metallized propellant propulsion systems are considered as replacements for the solid rocket boosters and liquid sustainer stages on the current launch vehicles: both the Space Transportation System (STS) and the Titan 4. Liquid rocket boosters for the STS were analyzed as replacements for current solid rocket boosters. These boosters can provide a liquid propulsion system within the volume constraints of a solid rocket booster. A replacement for the Space Shuttle Main Engines using metallized O2/H2/Al was studied. The liquid stages of the Titan 4 were also investigated; the Aerozine-50 (A-50) fuel was replaced with metallized storable A-50/Al. A metallized propellant is similar to a traditional liquid propellant. However, it has metal particles, such as aluminum, that are suspended in a gelled fuel, such as hydrogen, RP-1, A-50 or monomethyl hydrazine (MMH). The fuels then undergo combustion with liquid oxygen or nitrogen tetroxide (NTO). These propellants provide options for increasing the performance of existing launch vehicle chemical propulsion systems by increasing fuel density or specific impulse or both. These increases in density and specific impulse can significantly reduce the propulsion system liftoff weight and allow a liquid rocket booster to fit into the same volume as an existing solid rocket booster. Also, because gelled fuels are akin to liquid propellants, metallized systems can provide enhanced controllability over solid propulsion systems. Gelling of the propellant also reduces the sensitivity to impacts and consequently reduces the propellant explosion hazard.

Pressurised aerosol compositions

Abstract: There are disclosed pressurised aerosol compositions comprising a medicament, a hydrofluorocarbon propellant and a polyethoxylated surfactant, the compositions containing substantially no solvent, other than the propellant, capable of increasing the solubility of the surfactant in the propellant The compositions according to the invention are advantageous in that the solubility of the surfactant is such as to ensure good dispersion of the medicament and smooth operation of the aerosol valve

A method for the construction of a lunar transfer trajectory using ballistic capture

Abstract: The weak stability boundary (WSB) method for the design and optimization of lunar transfer trajectories is described. Considerable savings of propellant are shown over classical methods of orbit transfer such as the Hohmann transfer method. The savings in Delta V required of the spacecraft ranges from 100 to 200 m/s, which translates into a 5-10 percent reduction in spacecraft propellant for a science payload. Another advantage of the WSB method involves the utilization of low thrust propellant systems. Since the transfer trajectory is nearly completely ballistic, thrusting propulsive maneuvers may be performed over a long time duration.

System for the initiation of downhole explosive and propellant systems

Abstract: The present invention is included in an operating assembly for lowering into a wellbore on a wireline, tubular conveyance, or the like, or for use in a horizontal application, for initiating or setting off pyrotechnic, explosive, or propellant elements of that operating assembly, and comprises a firing head and an initiation assembly that are arranged for lowering into the wellbore, from a well head. The firing head provides for the extension of a striker plunger therefrom that travels into the initiating assembly to both arm it and to impact a piezoelectric device therein whose deformation generates an electrical current which fires an array of flashbulbs that excite a laser rod. The excited laser rod produces a laser beam that is passed through a fiberoptic cable or is split to pass through a plurality of fiberoptic cables to detonate initiation charges or to provide a cascading initiation of a number of initiation devices that each fire single or multiple pyrotechnic, explosive or propellant elements individually or in a cascading action.

Cartridge with flash tube

Abstract: A cartridge comprises a cartridge case having a bottom, a top, and a hollow interior, the top being open and receiving a projectile, and the hollow interior containing a propellant charge. A metal ignition tube extends from a primer cap on the bottom of the cartridge case for about one-third the length of the cartridge case. The metal ignition tube terminates in an open end. A detonating agent is contained within the metal ignition tube, but does not completely fill it. An empty channel is formed in the propellant charge and extends from the open end of the metal ignition tube to within proximity of the projectile. Preferably, the empty channel is constituted by a closed tube having walls made from a combustible material. When the cartridge is fired, a darting flame is produced in the metal ignition tube which passes through the open end unhindered into the empty channel, thereby igniting all of the propellant charge surrounding the channel practically simultaneously.

Flow visualization of a rocket injector spray using gelled propellant simulants

Abstract: A study was conducted at NASA-Lewis to compare the atomization characteristics of gelled and nongelled propellant simulants. A gelled propellant simulant composed of water, sodium hydroxide, and an acrylic acid polymer resin (as the gelling agent) was used to simulate the viscosity of an aluminum/PR-1 metallized fuel gel. Water was used as a comparison fluid to isolate the rheological effects of the water-gel and to simulate nongelled RP-1. The water-gel was injected through the central orifice of a triplet injector element and the central post of a coaxial injector element. Nitrogen gas flowed through the outer orifices of the triplet injector element and through the annulus of the coaxial injector element and atomized the gelled and nongelled liquids. Photographs of the water-gel spray patterns at different operating conditions were compared with images obtained using water and nitrogen. A laser light was used for illumination of the sprays. The results of the testing showed that the water sprays produced a finer and more uniform atomization than the water-gel sprays. Rheological analysis of the water-gel showed poor atomization caused by high viscosity of water-gel delaying the transition to turbulence.

Diclofenac preparations for topical use

Abstract: A diclofenac preparation for topical application which is packed together with a propellant gas in a compressed gas container and can be foamed from this through an atomiser with the aid of the propellant gas and delivered as diclofenac-containing foam is described.

Energetic Solid Fuels for Ducted Rockets (II)

Abstract: The combustion characteristics of variable-flow ducted rockets were evaluated in order to obtain optimum design parameters of the gas generators. The energetic solid fuels used for the gas generators were glycidyl azide polymer (GAP) with burning rate catalysts. The burning rate of GAP based energetic fuels was much higher than that of composite and double-base based fuel-rich propellants. The pressure exponent of the burning rate was high enough to obtain a wide range of variable-flow rat. Two types of combustion test were conducted: a semi-free jet and a direct connect flow. The pressure-time response in the primary combustor obtained by the use of a throttable nozzle was evaluated.

Solid-propellant-powered maneuvering system for spacecraft

Abstract: An improvement to a variable-pressure solid-propellant-powered maneuveringystem for spacecraft, enabling the system to operate for longer than one propellant burn time. At least two solid propellant gas generators are connected via a manifold to a plurality of nozzle valve clusters; at least one of the gas generators is connected to the manifold via a sequence valve which isolates that generator from the manifold until such time as it is desired to put that generator into operation.

Controlled fracture method and apparatus for breaking hard compact rock and concrete materials

Abstract: Hard compact materials, such as rock, concrete, et cetera, are broken by igniting an appropriately designed explosive or propellant charge placed within the hole or carried in a special charge-containing device with a short barrel which is inserted and sealed into a pre-drilled hole of particular geometry. One or more approximately cylindrical holes are drilled into the material to be broken by conventional drilling, such as used in the mining and construction industries. The holes have a relatively short depth to diameter ratio, being in the range of about 2:1 to 6:1, and preferably about 3:1 to 5:1. The holes are percussively drilled with microfractures in and around hole bottoms to provide fracture initiation sites at the hole bottoms so as to provide preferred fracture initiation roughly parallel to a free surface of material being excavated. The explosive or propellant charges may be any of several commercially available explosives or propellants, including standard military and commercial rifle powders and various recently developed liquid propellants. The propellant charges, whether solid or liquid, may be placed and ignited within a charge-containing device, which includes a short barrel inserted into the holes drilled into the material to be broken. The barrel of this device may be further sealed into the holes by a helical shim sealing method.

Rheology of solid propellant dispersions

Abstract: During processing, solid rocket propellants are particle suspensions which exhibit complex rheological properties. We discuss measurements of the properties of two typical solid propellants, HTPB and high energy. Despite their complexity in terms of particle shape and size distribution, these suspensions are shown to exhibit properties similar to those found in model systems. Of particular importance is the development of microstructure during shearing, which affects the ultimate performance of the rocket engine.