The parachute container cover ejection separation is the first and foremost motion for the return capsule recovery system,which is related to the success of a recovery system.Adopting the computational fluid dynamics(...The parachute container cover ejection separation is the first and foremost motion for the return capsule recovery system,which is related to the success of a recovery system.Adopting the computational fluid dynamics(CFD)simulation and flight dynamics coupling method,the parachute container cover ejection separation is simulated.The rationality of the ejection separation speed and dynamic characteristics of the separation process is analyzed.Meanwhile,the influences of angle of attack,Mach number and ejection separation speed on the parachute container cover ejection are also investigated.Results show that the ejection separation speed design is reasonable.It has a certain design margin for parachute container cover to escape from the wake region,and to pull out the drag parachute completely.The results may provide a theoretical basis for recovery system engineering design of the lunar exploration project.展开更多
The reliability assessment of aircraft ejection separation systems is crucial for aviation safety,but traditional methods exhibit significant shortcomings in dynamic behavior modeling,rare event quantification,and bid...The reliability assessment of aircraft ejection separation systems is crucial for aviation safety,but traditional methods exhibit significant shortcomings in dynamic behavior modeling,rare event quantification,and bidirectional consistency verification of function and fault paths.This paper proposes an innovative GO-FTA-GERTS dual model that integrates goal-oriented(GO)methods,fault tree analysis(FTA),and graphical evaluation and review technique(GERT)networks.The core innovation lies in constructing a bidirectional logical interlocking mechanism between the GO success tree and the FTA failure tree,leveraging the dynamic state transfer characteristics of GERT to achieve mathematical equivalence verification of function paths and fault paths.Using a specific aircraft ejection subsystem as an example,the model demonstrates excellent accuracy in ultra-low failure probability calculations:the mean system failure probability calculated by the FTA-GERT network is approximately 5.26×10^(−10) per flight hour,meeting airworthiness standards.At the same time,Monte Carlo simulation and Welch’s t-test are also used to verify that the success probability of GO-GERT model is strictly complementary to the system failure probability calculated by FTA-GERT network.This novel model effectively addresses the limitations of static analysis,dynamic path quantification,and rare event evaluation,providing a new method for reliability analysis of critical aviation safety systems.展开更多
In view of the separation form of the separator from the back of the carrier upward and from the side of the carrier outward, separation-safety research is carried out by taking the separation of a cluster munition as...In view of the separation form of the separator from the back of the carrier upward and from the side of the carrier outward, separation-safety research is carried out by taking the separation of a cluster munition as an example. In previous wind tunnel free-flight tests, the similarity law of vertical, downward, moving submunition was used to design submunitions at different positions in different initial-velocity directions, which resulted in large discrepancies between wind tunnel test results and real flight. In a wind tunnel test, each submunition has an independent time-reduction ratio with respect to the dispenser. Even if the separation trajectory of a single submunition is accurate, there will be errors in the position of each submunition at a given time. Therefore, it is necessary to determine the time-reduction ratio between submunitions, and to modify the test results later. In order to ensure the accuracy of wind tunnel test results, the similarity law of a freeflight test in a wind tunnel is derived in this paper. The time-correction scheme to ensure motion similarity between submunitions is solved. Numerical simulation is used to simulate the separation of a wind tunnel test and real aircraft, and the motion parameters of different submunitions are solved. The results show that the new similarity laws derived for different types of submunitions can greatly reduce the errors caused by previous similarity laws. In addition to the case for the separation of a cluster munition, the similarity law can also be applied to the free-flight test design of wind tunnels for vertical separation and horizontal separation of other kinds of aircraft.展开更多
基金Supported by the Aeronautical Science Foundation of China(2012ZC52035)
文摘The parachute container cover ejection separation is the first and foremost motion for the return capsule recovery system,which is related to the success of a recovery system.Adopting the computational fluid dynamics(CFD)simulation and flight dynamics coupling method,the parachute container cover ejection separation is simulated.The rationality of the ejection separation speed and dynamic characteristics of the separation process is analyzed.Meanwhile,the influences of angle of attack,Mach number and ejection separation speed on the parachute container cover ejection are also investigated.Results show that the ejection separation speed design is reasonable.It has a certain design margin for parachute container cover to escape from the wake region,and to pull out the drag parachute completely.The results may provide a theoretical basis for recovery system engineering design of the lunar exploration project.
基金supported by Shanghai Central Guidance Science and Technology Development Fund(NO:YDZX20233100004008)National Natural Science Foundation of China(NO:T2441003).
文摘The reliability assessment of aircraft ejection separation systems is crucial for aviation safety,but traditional methods exhibit significant shortcomings in dynamic behavior modeling,rare event quantification,and bidirectional consistency verification of function and fault paths.This paper proposes an innovative GO-FTA-GERTS dual model that integrates goal-oriented(GO)methods,fault tree analysis(FTA),and graphical evaluation and review technique(GERT)networks.The core innovation lies in constructing a bidirectional logical interlocking mechanism between the GO success tree and the FTA failure tree,leveraging the dynamic state transfer characteristics of GERT to achieve mathematical equivalence verification of function paths and fault paths.Using a specific aircraft ejection subsystem as an example,the model demonstrates excellent accuracy in ultra-low failure probability calculations:the mean system failure probability calculated by the FTA-GERT network is approximately 5.26×10^(−10) per flight hour,meeting airworthiness standards.At the same time,Monte Carlo simulation and Welch’s t-test are also used to verify that the success probability of GO-GERT model is strictly complementary to the system failure probability calculated by FTA-GERT network.This novel model effectively addresses the limitations of static analysis,dynamic path quantification,and rare event evaluation,providing a new method for reliability analysis of critical aviation safety systems.
基金supported by the Advanced Research Fund for Weapons and Equipment Development of China。
文摘In view of the separation form of the separator from the back of the carrier upward and from the side of the carrier outward, separation-safety research is carried out by taking the separation of a cluster munition as an example. In previous wind tunnel free-flight tests, the similarity law of vertical, downward, moving submunition was used to design submunitions at different positions in different initial-velocity directions, which resulted in large discrepancies between wind tunnel test results and real flight. In a wind tunnel test, each submunition has an independent time-reduction ratio with respect to the dispenser. Even if the separation trajectory of a single submunition is accurate, there will be errors in the position of each submunition at a given time. Therefore, it is necessary to determine the time-reduction ratio between submunitions, and to modify the test results later. In order to ensure the accuracy of wind tunnel test results, the similarity law of a freeflight test in a wind tunnel is derived in this paper. The time-correction scheme to ensure motion similarity between submunitions is solved. Numerical simulation is used to simulate the separation of a wind tunnel test and real aircraft, and the motion parameters of different submunitions are solved. The results show that the new similarity laws derived for different types of submunitions can greatly reduce the errors caused by previous similarity laws. In addition to the case for the separation of a cluster munition, the similarity law can also be applied to the free-flight test design of wind tunnels for vertical separation and horizontal separation of other kinds of aircraft.
