Browse Topic: Solid propellants

Items (97)
Pulsed Microwave Plasma Instrumentation for Investigation of Plasma-Tuned Multiphase Combustion19AERP02_112/1/2019
Instrumentation developed to support the investigation of electromagnetic wave interaction with energetic materials and flames could help develop microwave-sensitive energetic materials that produce effects such as microwave ignition, acceleration of burning rate, extinguishment, and re-ignition. Air Force Research Laboratory, Arlington, Virginia Strategies to control solid rocket propellant regression rate require a robust throttling technique applicable to high performance propellant formulations. Currently, several methods to control and throttle either motors or subscale propellant strands exist, including chamber pressure control (e.g. pintle nozzles or rapid depressurization quench), infrared laser irradiation of the burning surface to increase burning rates, development of inherently unstable combustion chamber geometries (producing either local pressure or velocity perturbations), and electrically sensitive hydroxylammonium nitrate (HAN)-based formulations in which burning rate is controlled by a voltage potential. However, these techniques are limited in that they either can only be used with low flame temperature (low specific impulse) propellants, result in low propulsion system mass fraction (pintle), are only capable of producing a single perturbation, or are formulation specific. To gain control over a combustion process, combustion plasma enhancement has been demonstrated in electrothermal-chemical (ETC) launchers, in which solid gun propellant ignition flame spread, pressurization rate, and global propellant burning rate improvements were observed. With ETC enhancement, burning rate improvement of up to 35% is possible and further enhancement is speculated to be possible with higher solid loading. However, ETC launchers (e.g. capillary plasma generation) are capable only of single plasma injections or have limited volume.
Measuring Propellant Stress Relaxation Modulus Using Dynamic Mechanical Analyzer17AERP08_066/1/2017
New testing technique requires less material, gives more accurate results. Air Force Research Laboratory (AFMC), Edwards Air Force Base, California Structural analysis of solid rocket motors is challenging for several reasons, but the most important of these is the complex behavior of the propellant. The mechanical response of a solid propellant is time and temperature dependent. The complexity of the mathematical analysis of the propellant depends on the loading conditions, but for some loading situations, the linear viscoelasticity assumption is reasonable. In particular, linear viscoelasticity is perhaps the most appropriate material behavior description for use in the simulations of stresses related to storage conditions. Typically, simulations use a viscoelastic model in the form of a Prony series and a Williams-Landel-Ferry (WLF) equation. The parameters in these models are derived from stress relaxation experiments, making the stress relaxation experiment a key viscoelastic test, analogous to the tensile test for linear elastic materials. A typical set of stress relaxation tests is performed at several discrete temperatures that cover a range of temperatures anticipated by the fielded motor. At each of the selected temperatures, the specimen is deformed with approximately a single step in strain, which is then held constant for the duration of the test. While held at this constant strain, the stress decays over time due to relaxation of the rubbery elastomer. During this portion of the test, the stresses are measured, and the ratio of stress to applied strain is determined. This ratio is termed the stress relaxation modulus ER. Using time-temperature superposition, the set of curves at the various temperatures can be shifted horizontally relative to each other to form a master curve. The translation of the curves takes a specific mathematical form, viz., the WLF equation. From this master curve, the Prony series at any given temperature can be calculated, and the calculation can be incorporated into finite element analyses along with the WLF equation, making linear viscoelastic analysis of rocket motors possible.
Converting in-situ resources such as CO2, which is the main component of the Mars atmosphere, into methane for rocket propellants can significantly reduce the cost and risk of human exploration while at the same time enabling new mission concepts and long-term exploration sustainability. Methanation of CO2, also called a Sabatier reaction, is hence a key enabling technology required for sustainable and affordable human exploration of Mars.
Hall thrusters normally use Xe propellant, which is expensive and scarce in the solar system. The weight of Xe is such that typical Hall thrusters are limited in specific impulse to approximately 3,000 s. The objective of this program was to improve and demonstrate Mg Hall thruster systems. Mg is abundant in the solar system and has an atomic mass approximately one-fifth that of Xe, which means much higher specific impulse is achieved than with Xe at typical thruster operating conditions (power, voltage).
NASA missions employing mobility systems and other moving mechanical assemblies for application on Mars, the Moon, and in deep space depend on the reliable operation of these assemblies and their tribological components. Wet lubricants are sometimes used in space applications, but in order to avoid solidification, they often require active heating due to the extreme cold temperatures that are encountered. Dry lubricants, such as molybdenum disulfide (MoS2), are more commonly chosen for space mechanisms because they are not subject to the low-temperature limitations of wet lubricants while also providing superior lubricating properties. A major drawback of dry lubricants is low wear resistance that eventually leads to failure of the assembly as the lubricant is removed.
Standard Electrical and Logical Interface for Airborne Fuzing SystemsAS5716A (Current)12/3/2012
This interface standard applies to fuzes/fuzing systems (referred to as fuzing system hereafter) in airborne weapons that use a MIL-STD-1760 type interface. It defines the powers, the discrete signals and the serial data interface for the communications at the interface between the fuzing system and the remainder of the weapon, including the weapon control unit. The Class 1 interface is an electrical only interface that facilitates use of MIL-STD-1760 type platform store interfaces for the fuze to monitor intentional release and defines the fuze interface bus communications protocol to allow sending and receiving data from fuzing systems. Class 2 interfaces add a defined connector and additional interfaces to facilitate the exchange of compatible fuzing systems. Class 3 interfaces add further interface definitions to facilitate the exchange of AS5680A compatible fuzing systems components. The bus communications protocol provides a means by which the weapon may set mission parameters within the fuzing system main housing and in other devices external to the fuzing system main housing. The standard also defines the target detection signal to be provided by a target detection device external to the fuzing system. This standard does not address the mechanical interfaces to target detection devices or to other sensors that are external to the fuzing system main housing.
AS-1B Aircraft Store Integration Committee
This interface standard applies to fuzes/fuzing systems (referred to as fuzing system hereafter) in airborne weapons that use a MIL-STD-1760 interface. It defines the powers, the discrete signals and the serial data interface for the communications at the interface between the fuzing system and the remainder of the weapon, including the weapon control unit, for Class 1 interfaces. Future issues of the standard will provide for additional fuzing system related functionality defined as Class 2 and Class 3 interfaces. For future issues of this standard, the connector definition is contained in AS5680. This standard does not impose any safety requirements and does not supersede or replace any existing applicable safety standards.
AS-1B Aircraft Store Integration Committee
Membranes on Mars for In-Situ Resource Utilization Processes2004-01-23167/19/2004
The goal of this project is the development and characterization of synthetic membranes for the separation and purification of CO2 from the Martian atmosphere for in-situ resource utilization (ISRU) applications such as in-situ propellant production. Candidate materials should have high selectivity for carbon dioxide over nitrogen and argon, and a glass transition temperature of -40 °C or less to remain in rubbery state at low temperature for high permeance (flux/driving force). Membrane materials we identified include the rubbery polymers poly(dimethyl siloxane) (PDMS) and the copolymer poly(dimethyl, methylphenyl siloxane) (PMPS). Pure and mixed gas permeation experiments with CO2, N2 and Ar were performed with these membrane materials in the temperature range -25 to 21 °C. In experiments with the commercially available PDMS membranes, the pure gas CO2 permeability increases from 1932 Barrers to 2755 Barrers as the temperature decreases from 22 to -30 °C. The ideal CO2/N2 separation factor (ratio of pure gas permeabilities/permeances) increases from 7.5 to 17.5 over the same temperature range. However, in mixed gas experiments, the CO2/N2 separation factor for PDMS was much lower, increasing from 4.5 to 6 as the temperature decreased from 22 to -30 °C. Pure gas permeation results with PMPS membranes also show an increase in CO2 permeability from 1450 Barrers to 1650 Barrers as the temperature decreases from 21 °C to -10 °C for differential feed pressure of 20 psi. The CO2/N2 ideal separation factor increased from 12 to 27 over the same range of temperature. Unlike PDMS, the mixed gas CO2/N2 selectivities are nearly the same as the pure gas values. We will also present reasons for these differences and discuss the design of membrane modules.
Jha, PraveenWay, J. DouglasSrinivasan, AnanthMason, Larry W.
This SAE Aerospace Information Report (AIR) presents safety criteria for pneumatic type engine starting system design and component hardware. Included are safety criteria in design of both starter control valves and starters as well as in design of airframe control systems. Safety topics concern starter valve operation and material application, airframe controls and instrumentation installations and starter rotor integrity and containment.
AE-6 Starting Systems and Auxiliary Power Committee
Items per page:
1 – 50 of 97