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For missions that involve launching satellites into sun-synchronous orbits, the load-carrying capacity can be improved by regulating the time distribution of different flight phases if a transfer orbit is planned. However, this will shorten the last burn time of the engines. This paper introduces the technologies to ensure a reliable engine restart after coasting when only a reduced level of propellants is left. The influence mechanism of different flight profiles on the carrying capacity is analyzed first. Then a joint simulation method integrating the attitude control and fluid dynamics is proposed that can accurately analyze the sloshing features of the cryogenic propellants and their influences under microgravity conditions. Finally, a guidance method is studied that eliminates the attitude deviations at the shutdown time of the first burn to suppress additional propellant sloshing during the follow-up coasting phase. The high-fidelity simulation system reveals the feasibility of a low level scenario, and with the action of the updated guidance method, the pressure drop can be controlled as needed and the sloshing can be well restrained, matching the existing pressurization ability and requirements for re-ignitions of engines. These technologies are applied in the successful launch of the LM-8/Y2 mission, in which the performance improvement is verified. • The performance improving mechanism by allocating times of flight phases is revealed. • A complete solution to a shallow startup under microgravity conditions is sorted out. • A high-fidelity joint simulation system with control/fluid dynamics is well modeled. • Innovative powered flight guidance is proposed to meet terminal attitude constraints. [ABSTRACT FROM AUTHOR]

Fuel tanks are a core component in satellites that manage the propellant. This study numerically analyzed the fluid transport with parallel guide vanes in a vane type surface tension tank. Flow3D was used to simulate fluid transport in microgravity in a scale model with 15% liquid filling rate with comparisons to experimental data. Then, the simulations were used to compare the leading edge climbing speed for various working conditions and the liquid volume below a specified cross section for various liquid filling rates, various numbers of vanes. The results show that the liquid climbing process on the guide plate in the plate tank can be divided into the liquid level repositioning stage after the gravitational force is suddenly removed and the stable fluid transport stage. Throughout the entire capillary flow stage, the liquid leading edge climbing rate is not related to the filling rate of the number of vanes and the fluid transport efficiency of a single guide vane is independent of the total number of vanes. [ABSTRACT FROM AUTHOR]

Iodine is considered as a feasible alternative to xenon as a propellant for electric propulsion systems, thanks to its good propulsive performance, high availability, and high storage density. However, as iodine is stored in solid state at ambient temperature, current state-of-the-art propellant management systems are not suitable to be used with it. Moreover, due to its high reactivity, iodine imposes requirements on material-compatibility, hindering the use of mass flow measurement and control systems typically used with other propellants. The architecture of a controlled iodine feeding system for low power (200 W class) ion and Hall effect thrusters is presented and the resulting prototype is described. It consists of a sublimation assembly whose temperature is used to control the tank pressure, a normally-closed ON-OFF valve, and a thermal throttle to perform the fine control of the mass flow rate. A 1D thermal-fluid model concerning the vapor generation in the tank, and its evolution along the different components is detailed. The thermal throttle model has been experimentally verified using air as a working fluid. The model results agree with the measurements of the verification tests in the hypothesis of the presence of an extended region at the entrance of the pipe where the laminar flow velocity and temperature profiles are not fully developed (known as entry flow region). Finally, the system is experimentally characterized and the model of the full system is calibrated using experimental measurements. The calibration shows that the thermal throttle flow presents an entry flow region, that the viscosity is correctly modeled, and that there is a difference between the measured tank temperature and the effective sublimation temperature.

The computational and experimental studies have been performed to investigate the hydrodynamic process of liquid propellant reorientation for the launch vehicle series fuel tanks in microgravity environment. The VOF method was used to simulate the free surface flow of gas-liquid. The process of the liquid propellant reorientation started from initially curved interface at low Bond number. The propellant reorientation flow procedure at high Bond number was obtained from numerical simulation and scale model experiment in drop tower. The numerical results agreed well with the experiments. The results can be used to adjust the engineering reorientation parameters. [ABSTRACT FROM AUTHOR]

A study of flow rate limitation in an open wedge channel is reported in this paper. Under microgravity condition, the flow is controlled by the convection and the viscosity in the channel as well as the curvature of the liquid free surface. A maximum flow rate is achieved when the curvature cannot balance the pressure difference leading to a collapse of the free surface. A 1-dimensional theoretical model is used to predict the critical flow rate and calculate the shape of the free surface. Computational Fluid Dynamics tool is also used to simulate the phenomenon. Results show that the 1-dimensional model overestimates the critical flow rate because extra pressure loss is not included in the governing equation. Good agreement is found in 3-dimensional simulation results. Parametric study with different wedge angles and channel lengths show that the critical flow rate increases with increasing the cross section area; and decreases with increasing the channel length. The work in this paper can help understand the surface collapsing without gravity and for the design in propellant management devices in satellite tanks. [ABSTRACT FROM AUTHOR]

Abstract: Experimental and computational studies have shown that a sufficiently strong magnetic field can influence a magnetically susceptible liquid. An improved simulation integrates an electromagnetic field model and incompressible flow model to predict fluid reorientation using realistic magnetic fields. Flow fields are presented incorporating several realistic magnetic fields to verify and validate the connectivity of the integrated models. Conclusions are drawn about the fidelity of the integrated simulation in modeling magnetically induced fluid flows. The simulation is used to model the application of magnetic positive positioning of LOX in a reduced gravity experiment utilizing a realistic magnetic field. Preflight experiment predictions of the performance of the magnetic field in reorienting LOX are presented and recommendations are made for future design. [Copyright &y& Elsevier]

Control of cryogenic propellant tank pressure during tank refueling and expulsion in low gravity is an important technical challenge to overcome for future long duration missions in space. One method proposed to control tank pressurization involves the use of jet-induced geysers. Two-dimensional computational models have been developed and used with limited success in previous efforts to predict geyser heights in microgravity. A three-dimensional flow simulation is used to model jet-induced geysers in reduced gravity. Geyser flows are commonly characterized by the presence of turbulent jets, transient flow, deforming free surfaces, and surface tension effects. As is the case for many turbulent flow applications, accuracy in simulating complex turbulent flows is critically dependent on the selection of a suitable turbulence model. The sensitivity of the simulation geyser predictions to a suite of popular turbulence models is assessed. Simulation results are compared to available experiment results. By expanding upon the work already completed, the model is used to simulate a broad range of cases within the experiment test matrix. Simulation results suggest the two dimensional simulation using the k- ε turbulence model provides the most accurate results for jet-induced geysers in reduced gravity when compared to available experiment data. [ABSTRACT FROM AUTHOR]

• Development of a compressible two-phase solver including phase change and conjugated heat transfer. • Successful verification of the solver with analytical solutions. • Accurate simulation of the pressure and temperature evolution of a cryogenic tank. • Analysis of the mass transfer at the free surface. Predicting the pressurant requirements is one of the key challenges for cryogenic propulsion systems. In this context, a numerical model to simulate the tank pressurization that considers evaporation and condensation phenomena was developed and applied. The novel solver combines a gradient-based phase change model with a weakly compressible multiphase solver of OpenFOAM based on the pressure implicit method with splitting of operator (PISO) algorithm. To maintain a sharp interface the mass source terms are applied to the cells adjacent to the interface. First, the model is validated against two analytical solutions: the one-dimensional phase change problem and secondly, the growth of a vapor bubble in a superheated liquid in the absence of gravity. In a second step, the validated model was applied to a cryogenic pressurization experiment. The measured pressure behavior could be confirmed with the numerical model being in a good approximation. With the numerical model further insights into the physical behavior could be achieved. The condensation and evaporation effects have a significant impact on the pressure development during and after the pressurization. The mass flows due to phase change occurring at the vapor-liquid interface depend on interface location and time. Directly at the wall, evaporation becomes dominant while condensation occurs at the center area of the liquid surface. [ABSTRACT FROM AUTHOR]

Abstract: Recent advances in magnet technology suggest that magnetic positive positioning of liquids may become a viable technology for future spacecraft systems. Preliminary simulation results for a subscale tank are presented which illustrate that a magnet of sufficient strength can retain liquid oxygen in an accelerating environment. Development of a new computational model for simulating equilibrium free surface shapes in the presence of a magnetic field is presented. Comparisons of equilibrium simulation predictions to known solutions for simple configurations support the conclusion that the computational model is suitable for continuing the investigation of magnetic propellant storage. Results obtained using the equilibrium simulation are presented to further demonstrate the feasibility of using magnetic retention to manage cryogenic propellants onboard spacecraft. [Copyright &y& Elsevier]

Iodine is considered as a feasible alternative to xenon as a propellant for electric propulsion systems, thanks to its good propulsive performance, high availability, and high storage density. However, as iodine is stored in solid state at ambient temperature, current state-of-the-art propellant management systems are not suitable to be used with it. Moreover, due to its high reactivity, iodine imposes requirements on material-compatibility, hindering the use of mass flow measurement and control systems typically used with other propellants. The architecture of a controlled iodine feeding system for low power (200 W class) ion and Hall effect thrusters is presented and the resulting prototype is described. It consists of a sublimation assembly whose temperature is used to control the tank pressure, a normally-closed ON-OFF valve, and a thermal throttle to perform the fine control of the mass flow rate. A 1D thermal-fluid model concerning the vapor generation in the tank, and its evolution along the different components is detailed. The thermal throttle model has been experimentally verified using air as a working fluid. The model results agree with the measurements of the verification tests in the hypothesis of the presence of an extended region at the entrance of the pipe where the laminar flow velocity and temperature profiles are not fully developed (known as entry flow region). Finally, the system is experimentally characterized and the model of the full system is calibrated using experimental measurements. The calibration shows that the thermal throttle flow presents an entry flow region, that the viscosity is correctly modeled, and that there is a difference between the measured tank temperature and the effective sublimation temperature. [ABSTRACT FROM AUTHOR]