Research On Optical Measurement Method Of Liquid Propellant Residue In Spacecraft Tank

The measurement of the remaining propellant in the spacecraft tank can predict the end-of-life time and give full play to the maximum economic benefits of the active spacecraft.Optical mass gauge sensor(OMGS)measures the energy attenuation of light in the medium and deduces the residual amount of the medium.This method has wide application range,high reliability and simple and reliable equipment.It is an important research direction of propellant residue measurement under microgravity conditions in the future.Aiming at the problems of too simple linear model and poor experimental accuracy in the optical measurement method of liquid propellant residue,based on the measurement principle of the optical measurement method of residue,a threedimensional optical absorption model of energy attenuation in the process of light propagation in three-dimensional medium is established,and the nonlinear relationship between the residue of propellant and the equivalent optical path length is proposed.By applying the three-dimensional nonlinear model of light absorption to propellant,the output radiation power under different residual conditions is obtained.The theoretical analysis shows that the attenuation and equivalent optical path length of light in propellant have a certain nonlinear relationship with the residual amount of liquid propellant;The spatial distribution of propellant has an influence on the measurement results of the optical measurement method of propellant residue,which can be ignored when the absorption coefficient is small;Because the light absorption coefficient is directly proportional to the medium density,the optical measurement method can measure the variable density medium,which can be applied in low temperature propellant.The improved optical measurement method of propellant residue reduces the systematic error brought by the model and improves the accuracy of the method,which lays a theoretical foundation for the application of optical measurement method in the measurement of propellant residue of on orbit spacecraft in the future.Aiming at the problem that the traditional optical measurement method of propellant residue does not consider the influencing factors such as propellant shape and position,a simulation system for optical measurement of propellant residue is built.Based on the principle of statistical average of sampling survey by Monte Carlo method,ray tracing by Monte Carlo method and Trace Pro software for different light wavelengths The radiation power output of the tank under the conditions of propellant filling rate,spatial distribution and inner wall reflectivity is simulated.The simulation results show that under different propellant spatial distributions,the output radiation power decreases with the increase of filling rate,and the decreasing speed gradually slows down;The influence of each influence parameter on the radiation power is highly consistent with the theoretical prediction.The light wavelength and inner wall reflectivity have the greatest influence on the measurement results,and the liquid surface shape has little influence on the measurement results;The dual wavelength comparison method can partially reduce the environmental disturbance and increase the effective range of optical measurement methods.It is found that when the light source and detector are symmetrically arranged and the filling rate is 0-36%,the measurement accuracy can reach ± 1%.In order to verify the theoretical model and simulation results,combined with photoelectric detection technology,a ground experimental platform for optical measurement of liquid propellant residue in spacecraft storage tank is designed and built.The ground experiment of optical measurement method is carried out and compared with the theoretical results.It is found that the predicted results of three-dimensional nonlinear model of optical measurement method are highly consistent with the experimental results.A specific algorithm for calculating the propellant residue using the detected radiation power is proposed.Various factors affecting the measurement accuracy in the measurement scheme design are analyzed.In order to improve the measurement accuracy,the selection index and specific selection of equipment in the optical measurement method scheme are defined.The scheme accuracy is evaluated combined with the theoretical process.The research of this paper is based on the actual needs of on orbit propellant residue measurement of spacecraft,focusing on a measurement method to deduce the medium quality by using the energy attenuation law of light in different media.The feasibility of the optical measurement method of propellant residue is verified by means of theoretical analysis,simulation and experimental verification,The measurement accuracy of the ground experimental system under the existing conditions is evaluated.This paper is an important supplement and active exploration of the existing residual measurement methods in China,and lays a certain theoretical and experimental foundation for the application of optical measurement methods in the measurement of propellant residual of on orbit spacecraft in the future..