Papers by Keyword: Microgravity

Abstract: Satellites store and manage propellant by surface tension. A surface tension propellant management device (PMD) consists of a propellant refillable reservoir (PRR) for propellant storage and propellant acquisition vanes (PAVs) for propellant transportation. PRR is a key part of vane type surface tension tank (STT), and its storage performance determines the fluid management of vane type STT. In the present paper, a model test system was established and microgravity drop tower tests conducted based on experimental study of fluid storage and transportation behavior of PRR. Laws of fluid storage and transportation of PRR in microgravity environment were obtained. The test results show that two types of PRR both have good liquid storage capacity, and the double cone PRR exhibits good liquid storage capacity in lateral acceleration. A rational design of PRR can effectively store liquid and control liquid transportation velocity. The test results offer a guideline for optimization of new-style vane type PMD, and also provide a new method for fluid control in space environment.

Abstract: The operation of a mechanical machine may behave differently in various gravitational conditions. We compare the mechanical efficiency of a mass-spring system in three different gravitational conditions, namely hypergravity (2G), normal gravity (1G) and microgravity (0G) through parabolic flight. The simple system consisted of a mass load (18.92 g and 21.97 g) attached between two springs 6.91 N/m which make overall length 410 mm. The mechanical efficiency is justified by the decay of the oscillation amplitude of the attached load. Our result shows that the mechanical efficiency for the simple mass-spring system is better in lower gravitational condition.

Abstract: The common mass balance has limited use in any gravitational condition. In this paper, we describe the simple design of a mass balance which is independent to the gravitational condition. Based on the Hookes Law, the balance is constructed by attaching the object being measured in the middle of two fixed end springs. The mass of the object is deducted from the frequency of the mechanical oscillation of the object. The performance of mass balance has been tested using four different mass loads (ranging from 15.28 g to 27.50 g) in three different gravitational conditions (0G, 1G and 2G) during parabolic flight. Our field testing resulted in the independency of the oscillation frequency of the mass on the gravitational conditions.

Abstract: A numerical study based on VOF model has been carried out to investigate the dynamics of water droplet impact on solid surface in microgravity in comparison with that in normal gravity to discuss the differences of the extinguishing mechanism of water mist in different gravity level. Water droplets with different initial diameters and impact velocities were considered. The simulated results show that the deformation process in microgravity lags behind that in normal gravity. And it was also found that D_max and spread velocities are smaller in microgravity as the potential energy decreases and the time taken for a liquid droplet to reach its maximum spread has no obvious regularity. Hence, the effect of cooling the fuel surface and diluting fuel vapour with water mist in microgravity may be not as good as that in normal gravity.The critical impact Weber number for water droplet breaking up in microgravity is lower than that in normal gravity as the reduction of the value of Bond number, which may result in diluting fuel vapour with water mist in microgravity being more effective than that in normal gravity in some case.

Abstract: The advantages and disadvantages of the method of separating the liquid from the gas on orbit are analyzed aiming at the propellant resupplying on orbit. A new method named spiral gas-liquid separation is proposed here, which is much simpler and highly efficient. Supposing the hydrazine as the propellant, the flow process of two-phase flow is numerical calculated. The results shows that the separated liquid would acquire higher speed and it would take shorter time for the fluid field to be balanced if the inlet fluid speed is higher with a constant gas-liquid ratio at the inlet. The same would take place if the ratio of the liquid to the gas is higher with a constant inlet speed.

Abstract: This article studies on the effect of magnetic field strengths on the flow field in a liquid bridge under zero gravity. The mass conservation level set method is used to track the two-phase interface. The results show that inhibitory effect of additional axial magnetic field on thermocapillary convection within liquid bridge is obvious, and this kind of inhibitory effect increasing as the magnetic field strength is strengthened.

Abstract: From engineering actual conditions of single crystal grown by floating zone method, Navier-Stokes equations coupled with the energy conservation equation were solved on a staggered grid based on the half floating area physical model. The two-phase surface was captured by using the mass conserving level set method. The internal flow structure of flow field of high Pr number liquid bridge was studied under uniform magnetic field environment in microgravity, which is important to optimize the process of the crystal growth.

Abstract: In an unprecedented experimental investigation, a binary, a ternary and a four-component hydrocarbon mixture at different pressure have been studied in a nearly convection free environment to understand the thermodiffusion process. Experimental investigations of the mixtures have been conducted in space onboard the spacecraft FOTON-M3. The experiment objective was to measure the thermodiffusion coefficient for multi-component hydrocarbon mixtures. Then the experimental results have also been used to test a thermodiffusion model that has been calibrated based on the results of previous experimental investigations. Results showed a good agreement with current theoretical results except for the four-component system where discrepancies were found and discussed.

Abstract: Containerless solidification of 300 to 850 µm diameter droplets of PbSn eutectic alloy was achieved by using a 3m length drop tube, which is one of the most suitable and low cost option to provide a microgravity environment on the ground. Phase morphology and composition were investigated, respectively, by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). It was found that the microstructure of the droplets depends on their sizes, where in larger diameters (>500µm) consists of both regular lamellar and irregular structures, and on other hand, for the smaller ones (<500µm) the structure is only irregular with higher lead concentration.

Abstract: The vapor compression distillation assembly is a phase-change water recovery technology which will reclaim water from urine, whose evaporator is a rotating container involving boiling heat transfer. The production rate of the apparatus depend on the bubble detachment diameter. In the article, based on the force equilibrium of bubble, the bubble detachment diameter formula is obtained, in which, the flow velocity along axis is neglected because it is very slow. The formula is very significant to the design of the apparatus and other relative apparatus.