Browse Topic: Solid propellants
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.
The scope of this SAE Information Report is to provide general information relative to the nature and use of infrared techniques for nondestructive testing. The document is not intended to provide detailed technical information, but will serve as an introduction to the theory and capabilities of infrared testing and as a guide to more extensive references.
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.
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.
The Space Station Integrated Kinetic Launcher for Orbital Payload Systems (SSIKLOPS), also known as “Cyclops,” deployed the largest satellite ever from the International Space Station (ISS) on November 28, 2014. The satellite, SpinSat, a Naval Research Laboratory (NRL)/Department of Defense Space Test Program (DoD STP) satellite, is pioneering the utilization of electronically controlled solid propellant thrusters as well as acquiring vital atmospheric density data. It is a spherical satellite 22 inches in diameter, weighing 115 pounds, and will remain in orbit for over two years.
The scope of this document is to provide a list of documents of types pertaining to the effects of oxygen on ignition and combustion of materials. Consolidating these references in one place makes it easier to find documents of this type as these references are difficult to locate.
Much of the available long-term storage test data has been reviewed and topically separated to enable the independent discussion of storage effects on fluids, seals, hydraulic components, and hydraulic systems. Comments are made in Section 4 concerning the applicability of the test results and regarding design practices for storability. Conclusions are drawn in Section 5 regarding inactive storage of hydraulic systems for at least a 7 year period.
WHILE SOME COMPANIES ARE CREATING HIGH ALTITUDE AIR AND GROUND LAUNCH VEHICLES FOR TAKING PRIVATE INDIVIDUALS INTO SPACE, COMPANIES SUCH AS XCOR AEROSPACE AND ARMADILLO AEROSPACE ARE ADDRESSING OTHER MARKET NEEDS IN THE PRIVATE SPACE FLIGHT INDUSTRY. WHILE COMPANIES such as Virgin Galactic and Space-X are creating high altitude air and ground launch vehicles for taking private individuals into space, companies such as XCOR Aerospace and Armadillo Aerospace, which builds hardware for its partner Space Adventures, are addressing other market needs in the private space flight industry. Space Adventures offers a “true” rocket experience with horizontal takeoff and landing with Armadillo Aerospace vehicles, and XCOR's Lynx hopes to have aircraft-like operations from any suitable spaceport. Each perceives that a market exists for its flavor of suborbital space travel and has located people willing to pay (and even wait) for a space experience.
While some companies are creating high altitude air and ground launch vehicles for taking private individuals into space, companies such as XCOR Aerospace and Armadillo Aerospace are addressing other market needs in the private space flight industry. While companies such as Virgin Galactic and Space-X are creating high altitude air and ground launch vehicles for taking private individuals into space, companies such as XCOR Aerospace and Armadillo Aerospace, which builds hardware for its partner Space Adventures, are addressing other market needs in the private space flight industry. Space Adventures offers a “true” rocket experience with horizontal takeoff and landing with Armadillo Aerospace vehicles, and XCOR’s Lynx hopes to have aircraft-like operations from any suitable spaceport. Each perceives that a market exists for its flavor of suborbital space travel and has located people willing to pay (and even wait) for a space experience.
Much of the available long-term storage test data has been reviewed and topically separated to enable the independent discussion of storage effects on fluids, seals, hydraulic components, and hydraulic systems. Comments are made in Section 4 concerning the applicability of the test results and regarding design practices for storability. Conclusions are drawn in Section 5 regarding inactive storage of hydraulic systems for at least a 7 year period.
Gas, for the purpose of this ARP, shall be defined as the gaseous product(s) resulting from the decomposition, dissociation, or combustion of liquid, or solid mono or bi-propellants. Where other gases such as heated N2, H2, H2O (steam), etc., which may have similar physical and/or chemical properties as the defined "gas", are used to effect testing economies, they may be considered as being included in this ARP.
The scope of this document is to provide a list of documents of types pertaining to the effects of oxygen on ignition and combustion of materials. Consolidating these references in one place makes it easier to find documents of this type as these references are difficult to locate.
Marshall Aerospace Vehicle Representation in C (MAVERIC) is a computer program for generic, low-to-high-fidelity simulation of the flight(s) of one or more launch vehicle(s) or spacecraft. MAVERIC is designed to accommodate multi-staged vehicles, powered serially or in parallel, with multiple engines, tanks, and cargo elements. Engines can be of jet or conventional rocket types, using either liquid or solid propellants.
A dual-pulse laser (DPL) technique has been demonstrated for generating laser-induced sparks (LIS) to ignite fuels. The technique was originally intended to be applied to the ignition of rocket propellants, but may also be applicable to ignition in terrestrial settings in which electric igniters may not be suitable. Laser igniters have been sought as alternatives to such conventional devices as electrical spark plugs and torch igniters for the following main reasons:
NASA narrows its search for a successor to the Space Shuttle. NASA is another step closer to defining the next-generation reusable space transportation system. The first review of the Space Launch Initiative (SLI), a NASA-wide effort defining future space transportation systems, has been completed, narrowing the field of potential candidates for a new space transportation system. Dependable, long-life engines, along with crew escape and survival systems, and long-life, lightweight integrated airframes are among the SLI's highest priorities. Each greatly impacts the program's bottom line of increased safety, reliability, and cost-effectiveness.
"Hybrisol" denotes a proposed rocket engine that would contain hybrid and solid-propellant parts within a single combustion chamber. ["Hybrid" as used here denotes a type of rocket engine in which a solid fuel is burned by use of a liquid or gaseous oxidizer and the flow of the oxidizer can be throttled to control the engine. Unlike conventional solid rocket propellants, a solid fuel for a hybrid rocket engine can be made relatively inert in the absence of the oxidizer and therefore presents little hazard of explosion or inadvertent ignition.] Inside a hybrisol rocket engine, there would be two concentric tubular energy-storage layers: an outer layer of conventional solid rocket propellant and an inner layer of solid hybrid fuel (see figure).
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