For the issues of attitude strong coupling and the increments of attitude errors of upper stage during multi-satellite disposing,a three-axis stability nonlinear attitude control algorithm via feedback linearization i...For the issues of attitude strong coupling and the increments of attitude errors of upper stage during multi-satellite disposing,a three-axis stability nonlinear attitude control algorithm via feedback linearization is presented.By the definitions of coordinates and the attitude angle during multi-satellite disposing,the attitude dynamics and kinematics equations with Euler angles described are built.And the equations are equivalently linearized based on feedback linearization theory.A three-axis nonlinear predictive control algorithm is designed and the system robustness is analyzed.An example of mathematical simulation is completed using the Matlab/Simulink environment.Simulation results showed that the control algorithm has good disturbance rejection,rapidity,stability and robustness.展开更多
Upper stage is an indispensable vehicle in the space transportation system.For its role in multi-satellite transportation area in China,the development of the Yuanzheng 3 upper stage was approved.The article introduce...Upper stage is an indispensable vehicle in the space transportation system.For its role in multi-satellite transportation area in China,the development of the Yuanzheng 3 upper stage was approved.The article introduces in detail the Yuanzheng 3 upper stage development requirements,task definition and systems as well as main features and performance including payload capacity and insertion accuracy for typical orbits,interfaces with satellites.The article also presents the development cycle of Yuanzheng 3 upper stage,which is divided into 3 stages including concept demonstration stage,prototype stage and flight proof stage.The Yuanzheng 3 upper stage,which will make its maiden flight in 2018,is capable of restarting more than 20 times,and operating for more than 48 hours.It is equivalent to mainstream upper stages in the world in terms of performance,such as restart times,in-orbit operation time,independent digital control system,and adaptable behavior for various tasks.Technologies tackled and accumulated in the development of the Yuanzheng 3 upper stage will lay a solid foundation for the development of future space transportation vehicles.展开更多
The paper describes the new pressurization system for the upper stage of launch vehicles and spacecraft and the flight test results of the vehicle which conform to the design of the system.
Improved liquid rocket engine cycles were proposed and analyzed via comparison with existing staged combustion and gas-generator cycles.The key features of the proposed cycles are regenerative cooling of thrust chambe...Improved liquid rocket engine cycles were proposed and analyzed via comparison with existing staged combustion and gas-generator cycles.The key features of the proposed cycles are regenerative cooling of thrust chamber by oxygen and subsequent use of this oxygen for driving one or two oxygen pumps.The fuel pump(s)are driven in a conventional manner,for example,using a fuel-rich gas-generator cycle.Comparison with staged combustion cycle based on oxygen-rich pre-burner showed that one of the proposed semi-expander cycles has a specific impulse only on 0.4%lower while providing much lower oxygen temperature,more efficient tank pressurizing system and built-in roll control.This semi-expander cycle can be considered as a more reliable and cost-effective alternative of staged combustion cycle.Another semi-expander cycle can be considered as an improvement of gas-generator cycle.All proposed semi-expander cycles were developed as a derivative of thrust chamber regenerative cooling performed by oxygen.Analysis of existing oxygen/kerosene engines showed that replacing of kerosene regenerative cooling with oxygen allows a significant increase of achievable specific impulse,via optimization of mixture ratio.It is especially the case for upper stage engines.The increasing of propellants average density can be considered as an additional benefit of mixture ratio optimization.It was demonstrated that oxygen regenerative cooling of thrust chamber is a feasible and the most promising option for oxygen/kerosene engines.Combination of oxygen regenerative cooling and semi-expander cycles potentially allows creating the oxygen/kerosene propulsion systems with minimum specific impulse losses.It is important that such propulsion systems can be fully based on inherited and well-proven technical solutions.A hypothetic upper stage engine with thrust 19.6 kN was chosen as a prospective candidate for theoretical analysis of the proposed semi-expander cycles.The newly-developed software RECS was used for the comparative analysis of engine cycles.展开更多
Objective To evaluate the decision process to perform staged or synchronous bilateral percutaneous nephrolithotripsy ( PCNL) in the treatment of bilateral upper urinary tract calculi. Methods Patients with an indicati...Objective To evaluate the decision process to perform staged or synchronous bilateral percutaneous nephrolithotripsy ( PCNL) in the treatment of bilateral upper urinary tract calculi. Methods Patients with an indication for bilateral PCNL were enrolled in the study展开更多
文摘For the issues of attitude strong coupling and the increments of attitude errors of upper stage during multi-satellite disposing,a three-axis stability nonlinear attitude control algorithm via feedback linearization is presented.By the definitions of coordinates and the attitude angle during multi-satellite disposing,the attitude dynamics and kinematics equations with Euler angles described are built.And the equations are equivalently linearized based on feedback linearization theory.A three-axis nonlinear predictive control algorithm is designed and the system robustness is analyzed.An example of mathematical simulation is completed using the Matlab/Simulink environment.Simulation results showed that the control algorithm has good disturbance rejection,rapidity,stability and robustness.
文摘Upper stage is an indispensable vehicle in the space transportation system.For its role in multi-satellite transportation area in China,the development of the Yuanzheng 3 upper stage was approved.The article introduces in detail the Yuanzheng 3 upper stage development requirements,task definition and systems as well as main features and performance including payload capacity and insertion accuracy for typical orbits,interfaces with satellites.The article also presents the development cycle of Yuanzheng 3 upper stage,which is divided into 3 stages including concept demonstration stage,prototype stage and flight proof stage.The Yuanzheng 3 upper stage,which will make its maiden flight in 2018,is capable of restarting more than 20 times,and operating for more than 48 hours.It is equivalent to mainstream upper stages in the world in terms of performance,such as restart times,in-orbit operation time,independent digital control system,and adaptable behavior for various tasks.Technologies tackled and accumulated in the development of the Yuanzheng 3 upper stage will lay a solid foundation for the development of future space transportation vehicles.
文摘The paper describes the new pressurization system for the upper stage of launch vehicles and spacecraft and the flight test results of the vehicle which conform to the design of the system.
文摘Improved liquid rocket engine cycles were proposed and analyzed via comparison with existing staged combustion and gas-generator cycles.The key features of the proposed cycles are regenerative cooling of thrust chamber by oxygen and subsequent use of this oxygen for driving one or two oxygen pumps.The fuel pump(s)are driven in a conventional manner,for example,using a fuel-rich gas-generator cycle.Comparison with staged combustion cycle based on oxygen-rich pre-burner showed that one of the proposed semi-expander cycles has a specific impulse only on 0.4%lower while providing much lower oxygen temperature,more efficient tank pressurizing system and built-in roll control.This semi-expander cycle can be considered as a more reliable and cost-effective alternative of staged combustion cycle.Another semi-expander cycle can be considered as an improvement of gas-generator cycle.All proposed semi-expander cycles were developed as a derivative of thrust chamber regenerative cooling performed by oxygen.Analysis of existing oxygen/kerosene engines showed that replacing of kerosene regenerative cooling with oxygen allows a significant increase of achievable specific impulse,via optimization of mixture ratio.It is especially the case for upper stage engines.The increasing of propellants average density can be considered as an additional benefit of mixture ratio optimization.It was demonstrated that oxygen regenerative cooling of thrust chamber is a feasible and the most promising option for oxygen/kerosene engines.Combination of oxygen regenerative cooling and semi-expander cycles potentially allows creating the oxygen/kerosene propulsion systems with minimum specific impulse losses.It is important that such propulsion systems can be fully based on inherited and well-proven technical solutions.A hypothetic upper stage engine with thrust 19.6 kN was chosen as a prospective candidate for theoretical analysis of the proposed semi-expander cycles.The newly-developed software RECS was used for the comparative analysis of engine cycles.
文摘Objective To evaluate the decision process to perform staged or synchronous bilateral percutaneous nephrolithotripsy ( PCNL) in the treatment of bilateral upper urinary tract calculi. Methods Patients with an indication for bilateral PCNL were enrolled in the study
