Uncertainty analysis of propellant gauging system for spacecraft

This paper discusses the traditional concept of propellant gauging system based on the gas law method for estimating the amount of residual propellant mass in spacecraft and the effects of the uncertainty in the instruments on the predicted amount of propellant.Because for accurate determination of the remaining mission life of the satellite it is extremely essential to estimate the amount of propellant present in the propellant tank of the spacecraft at various stages of its mission life, it is important to study the extent to which the uncertainty in various instruments and other measured parameters affect the predicted amount of propellant. With Monte Carlo simulation, it is found that the accuracy with which the propellant quantity can be estimated is highly sensitive to the precision of the propellant tank pressure sensor. It is also found that the uncertainties in the propellant tank pressure sensor and the pressurant tank temperature sensor result in uncertainty as well as over prediction of the amount of residual

Configuration for Propellant Gauging in Satellites

Accurate propellant gauging is of prime importance insatellite industries. This paper explores the possibility of using a new propellant tank configuration, consisting of a truncated cone centrally mounted within a spherical propellant tank, to measure the amount of liquid propellant present within the tank. The liquid propellant present within the propellant tank orients itself in geometry by virtue of its dominant surface tension force in 0 g condition, which minimizes its total surface energy. This study reveals that the amount of liquid propellant present in the tank can thus be estimated by measuring the height of the propellant meniscus within the central cone. It is also observed that, for the proposed configuration, the precision of the estimated propellant fill-fraction increases towards the end of life of the spacecraft

Uncertainty analysis of propellant gauging system for spacecraft

This paper discusses the traditional concept of propellant gauging system based on the gas law method for estimating the amount of residual propellant mass in spacecraft and the effects of the uncertainty in the instruments on the predicted amount of propellant.Because for accurate determination of the remaining mission life of the satellite it is extremely essential to estimate the amount of propellant present in the propellant tank of the spacecraft at various stages of its mission life, it is important to study the extent to which the uncertainty in various instruments and other measured parameters affect the predicted amount of propellant. With Monte Carlo simulation, it is found that the accuracy with which the propellant quantity can be estimated is highly sensitive to the precision of the propellant tank pressure sensor. It is also found that the uncertainties in the propellant tank pressure sensor and the pressurant tank temperature sensor result in uncertainty as well as over prediction of the amount of residual

A technique for drop size control during throttling of a rocket engine

Experimental studies have been conducted on a new type of injector which can be used very advantageously in rocket engines designed for throttling applications. The aim is to keep the drop size constant for varying chamber pressures. The injector uses very small quantities of a gas to atomize a straight liquid jet before discharging into the combustion chamber. The concept is demonstrated over an eightfold variation of injector pressure drop. A feedback control system, which can regulate the air pressure with respect to the sensed chamber pressure, based on the input transfer function, so as to keep the drop size constant, is suggested. The transfer function is obtained from the experimental data. The major advantage of this injector is that it uses a very small quantity of gas, thereby limiting the weight penalty to a minimum. This system is much less complicated compared to variable area injector and cavitating venturi valves used for this purpose

Configuration for Propellant Gauging in Satellites

Accurate propellant gauging is of prime importance insatellite industries. This paper explores the possibility of using a new propellant tank configuration, consisting of a truncated cone centrally mounted within a spherical propellant tank, to measure the amount of liquid propellant present within the tank. The liquid propellant present within the propellant tank orients itself in geometry by virtue of its dominant surface tension force in 0 g condition, which minimizes its total surface energy. This study reveals that the amount of liquid propellant present in the tank can thus be estimated by measuring the height of the propellant meniscus within the central cone. It is also observed that, for the proposed configuration, the precision of the estimated propellant fill-fraction increases towards the end of life of the spacecraft

An Analysis of a Boundary Layer Diffusion Flame Over a Porous Flat Plate in a Confined Flow

A numerical analysis of the gas dynamic structure of a two-dimensional laminar boundary layer diffusion flame over a porous flat plate in a confined flow is made on the basis of the familiar boundary layer and flame sheet approximations neglecting buoyancy effects. The governing equations of aerothermochemistry with the appropriate boundary conditions are solved using the Patankar-Spalding method. The analysis predicts the flame shape, profiles of temperature, concentrations of variousspecies, and the density of the mixture across the boundary layer. In addition, it also predicts the pressure gradient in the flow direction arising from the confinement ofthe flow and the consequent velocity overshoot near the flame surface. The results of thecomputation performed for an n-pentane-air system are compared with experimental data andthe agreement is found to be satisfactory

A study on converging thin annular jets

An interesting feature of jets from liquid-liquid coaxial swirl atomizers used in bipropellant rockets or elsewhere is that the outer jet results in a tulip shaped liquid bulb even at operating pressure levels. In this context, experiments have been performed to study the discharge and tulip characteristics of annular jets through qualitative simulation of outer jet flow conditions at which tulip bulb prevails. It is shown that the discharge coefficient increases steeply with Reynolds number, a trend which is distinct from that of circular orifices. The range of flow conditions at which tulip bulb prevails decreases with the annular gap. If a swirl component is introduced into the annular jet, it alters the discharge characteristics and the tulip range with a tendency to form multiple tulips. Variation of tulip length for different annular gaps shows a common trend when plotted against liquid flow rate. The experimental data of tulip length agree reasonably with the theoretical model reported in literature

Transient Momentum and Enthalpy Transfer in Packed Beds at High Reynolds Numbers

An experimental study for transient temperature response and pressure drop in a randomly packed bed at high Reynolds numbers is presented.The packed bed is used as a compact heat exchanger along with a solid-propellant gas generator, to generate room-temperature gases for use in control actuation, air bottle pressurization, etc. Packed beds of lengths 200 and 300 mm were characterized for packing-sphere-based Reynolds numbers ranging from 0.8 x 10(4) to 8.5 x 10(4).The solid packing used in the bed consisted of phi 9.5 mm steel spheres. The bed-to-particle diameter ratio was with the average packed-bed porosity around 0.43. The inlet flow temperature was unsteady and a mesh of spheres was used at either end to eliminate flow entrance and exit effects. Gas temperature and pressure were measured at the entry, exit,and at three axial locations along centerline in the packed beds. The solid packing temperature was measured at three axial locations in the packed bed. A correlation based on the ratio of pressure drop and inlet-flow momentum (Euler number) exhibited an asymptotically decreasing trend with increasing Reynolds number. Axial conduction across the packed bed was found to he negligible in the investigated Reynolds number range. The enthalpy absorption rate to solid packing from hot gases is plotted as a function of a nondimensional time constant for different Reynolds numbers. A longer packed bed had high enthalpy absorption rate at Reynolds number similar to 10(4), which decreased at Reynolds number similar to 10(5). The enthalpy absorption plots can be used for estimating enthalpy drop across packed bed with different material, but for a geometrically similar packing