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A library of computer programs for antenna feed system design and analysis is described, with emphasis on instructions for using the programs. The programs cover a large spectrum of feed design problems, from primary feed pattern synthesis to the far-field pattern of the main reflector, including analyses of structural distortions.
Consistent and reliable preprocessing, conveyance, and reactor in-feed systems, particularly for low-cost waste feedstocks, remains a major technical challenge for the emerging Bioeconomy. By identifying critical biomass attributes and connecting them to flow and conversion behavior, science-driven system designs can address these often-overlooked solids handling challenges. The Wonderful Company (TWC) is the world's largest almond and pistachio grower, generating 250,000 dry tons/year of waste material including hulls, shells, and wood (>5 million tons/year industry wide in the U.S.). This project seeks to turn this environmental and economic liability into a sustainable and profitable resource, targeting conversion via gasification to syngas for electricity and bio-char, by addressing related material handling and feeding challenges. Based on optimized preprocessing strategies, bulk material flow, and thermal conversion properties, an overall system design will be developed. The methodology will be tested with FCIC's benchmark loblolly pine residues, to demonstrate the robustness of the overall approach and provide insight and guidance for future systems. The project will culminate in extended field trials to demonstrate an improved continuous feeding system with a commercial biomass-to-electricity gasifier vendor, and an economic analysis demonstrating a reduction in electricity production costs by maximizing on-stream time while minimizing preprocessing and CapEx costs.
An additively manufactured thrust chamber assembly was designed and printed using laser powder bed fusion. The NASA-developed material GRCop-42 was used for its high strength and high temperature characteristics. The combustion chamber and nozzle utilize regenerative coolant channels to achieve long duration hot fire tests. Design for additive manufacturing was used to create geometries not easily attainable with traditional machining. The thrust chamber assembly was post processed to ensure print quality and verify for testing. A feed system – encompassing all propellant lines, valves, sensors, and tanks – was designed and built to enable steady state, pressure regulated testing. Pressure transducers, thermocouples, and load cells were placed to enable measurements of the propellant properties and engine performance. Venturis and orifices were used throughout the system to control the flow rates to the thrust chamber. Aside from providing propellants, the feed system provides pressure using nitrogen, and purges the lines during shutdown. The design process for this testing platform is described. A testing campaign on the hardware will be conducted by the Akronauts Rocket Design Team at the University of Akron in Spring 2023.
An additively manufactured thrust chamber assembly was designed and printed using laser powder bed fusion. The NASA-developed material GRCop-42 was used for its high strength and high temperature characteristics. The combustion chamber and nozzle utilize regenerative coolant channels to achieve long duration hot fire tests. Design for additive manufacturing was used to create geometries not easily attainable with traditional machining. The thrust chamber assembly was post processed to ensure print quality and verify for testing. A feed system – encompassing all propellant lines, valves, sensors, and tanks – was designed and built to enable steady state, pressure regulated testing. Pressure transducers, thermocouples, and load cells were placed to enable measurements of the propellant properties and engine performance. Venturis and orifices were used throughout the system to control the flow rates to the thrust chamber. Aside from providing propellants, the feed system provides pressure using nitrogen, and purges the lines during shutdown. The design process for this testing platform is described. A testing campaign on the hardware will be conducted by the Akronauts Rocket Design Team at the University of Akron in Spring 2023.
Improved prototype space feeding system for Manned Orbiting Laboratory missions
Fourteen computer programs have been developed for antenna feed system design and analysis. The programs cover a large spectrum of feed design problems, from primary feed pattern synthesis to the farfield pattern of the main reflector, including analyses of structural distortions.
The use of solid iodine as a propellant in Hall-effect thrusters (HETs) is currently being investigated for small-satellite applications. CubeSats offer an inexpensive mode of access to space; however, they currently lack significant propulsion capability. A high specific impulse (I (sub sp)) propulsion system would permit a significant change in velocity, delta v, to be imparted for orbital maintenance, transfers, or de-orbit maneuvers. An electric propulsion system that uses iodine as a propellant has a number of advantages. It has an exceptionally high rho times I (sub sp) figure of merit (density multiplied by the specific impulse), meaning that it can achieve a large total delta v with a relatively low combination of propellant mass and propellant tank volume. Also, the propellant feed system operates at low pressures (a few psia at most), as opposed to the use of super-critical xenon stored at very high pressure. Low pressure operation can lower system mass while greatly reducing the risk of propellant tank rupture, making low pressure a vitally important property for propellants on secondary payloads like CubeSats, where risks must be minimized. The iSAT mission aims to demonstrate iodine-fed HET technology, flying it in space onboard a 12U 912-unit) CubeSat. In the iSAT propellant feed system (PFS), solid iodine is sublimed through heating to produce gaseous propellant that is conducted through tubing to the thruster and cathode. The sublimation process is governed by the iodine (I2) vapor pressure, which is shown as a function of temperature in figure 1. As gaseous I2 flows out of the tank, the gas pressure in the volume containing the solid iodine propellant is reduced until a balance between the flow of iodine out of the tank and the sublimation rate of solid iodine at the equilibrium gas pressure and chosen tank temperature is reached.
Flight-prototype ammonia-propellant storage and feed system using titanium tank with stainless steel plenum chamber
A reflex feed system is described for a dual frequency antenna such as one which transmits and receives both S and X band signals. The dichroic plate, normally employed for directing X band radiation away from the X band horn, is replaced by a flange about the opening of the X band horn.
Contiguous multiple beams are used to make use of the set of frequency bands at different beams at different geographical locations and achieve the most efficient use of precious frequency allocation. This is feasible only if the interference among cochannel beams is below some acceptable level, by carrier/interference (C/I) ratio. Individual beam patterns of very low sidelobes, which in turn necessitates narrow feed are required. A physically realizable solution to this problem entails either more than one reflector, more complicated optics, or breaking of each feed into a cluster of smaller elements, some of which would then be shared by adjacent beams. The latter, however, requires a complicated beamforming network (BFN) for the proper feeding of the elements. The feedpacking problem is not unique to reflector antennas and exists in lens type antennas as well. The BFN and associated problems are present in the phased array antennas and on a much larger scale. Poor scan capabilities are associated with reflector systems. The scan properties of offset fed reflector systems can be improved by choosing a very large focal length to parent reflector diameter ((F/Dp) ratio, which requires a longer boom to support the feed. In the case of reflectors with cluster feed arrangements, the scan capability for smaller F/Dp ratios is improved by proper adjustment of cluster element excitations. Such a system seems to be appropriate for up to 10 beamwidths scan. For a larger number of beams, systems with wider scan capabilities, such as phased arrays or phased array/reflector combinations, become more appealing.
Development and characteristics of low-noise multimode monopulse antenna feed system for use with microwave communication equipment
A prototype bismuth propellant feed and control system was constructed and tested. An electromagnetic pump was used in this system to provide fine control of the hydrostatic pressure, and a new type of in-line flow sensor was developed to provide an accurate, real-time measurement of the mass flow rate. High-temperature material compatibility was a driving design requirement for the pump and flow sensor, leading to the selection of macor for the main body of both components. Post-test inspections of both components revealed no cracks or leaking in either. In separate proof-of-concept experiments, the pump produced a linear pressure rise as a function of current that compared favorably with theoretical pump pressure predictions, with a pressure of 10 kPa at 30 A. Flow sensing was successfully demonstrated in a bench-top test using gallium as a substitute liquid metal. A real-time controller was successfully used to control the entire system, simultaneously monitoring all power supplies and performing data acquisition duties.
Propulsion for the Deep Space One (DS1) spacecraft is provided by a xenon ion engine. Xenon is stored in a supercritical state and is delivered as a low pressure gas to the thruster and two cathodes by a Xenon Feed System (XFS).
Very high power and low noise Cassegrain feed system for planetary radar in Deep Space Instrumentation Facility /DSIF/
Phase center position of field scattered from hyperboloid subreflector in asymmetric Cassegrain antenna feed system
Parabolic antenna properties generated by dual band circularly polarized focused two channel monopulse feed system, discussing tracking data from helicopter, Apollo 8 and Cassiopeia A
Propulsion for the Deep Space One (DS1) spacecraft is provided by a xenon ion engine. Xenon is stored in a supercritical state and is delivered as a low pressure gas to the thruster and two cathodes (called the main cathode and neutralizer) by a Xenon Feed System (XFS).
Criteria for design, fabrication, inspection, and servicing of liquid fluorine propellant feed system components