Abstract
A typical blunt body such as Tianwen-1 Mars entry capsule suffers dynamic instability in supersonic regime. To investigate the unstable Mach range of flight and to confirm the design of aerodynamic shape and mass properties, a ballistic range test was carried out aiming at capturing supersonic dynamic characteristics of Tianwen-1. Aerodynamic coefficients of free-flight scaled models were derived by modified linear regression method based on position and attitude data, while the dynamic coefficients were established under the assumption of small angle linearization. The static moment coefficients and dynamic derivatives were identified thereafter. Results show that models in untrimmed configuration are dynamically unstable at certain Mach numbers, whereas models in trimmed configuration are dynamically stable at other Mach numbers tested. Both trimmed and untrimmed configurations are statically stable in all testing cases.
Highlights
The Tianwen-1 Mars entry capsule successfully landed on the surface of Mars in southern Utopia planitia on May 14th, 2021 at 23 : 18 UTC
The results show that the maximum axial force on the capsule in untrimmed configuration appears near Mach 2.5 at around 0° of angle of attack, and the maximum axial force is 1.47; the pitch moment
The results shows that both static and dynamic derivatives of the untrimmed configuration in shot HX02 are negative, which indicates that both pitch and yaw directions of the untrimmed configuration are statically and dynamically stable at Mach 2.45 with small angle of attack
Summary
The Tianwen-1 Mars entry capsule successfully landed on the surface of Mars in southern Utopia planitia on May 14th, 2021 at 23 : 18 UTC. A free-flight ballistic range test was conducted in order to obtain the static and dynamic aerodynamic characteristics of Tianwen-1 in trimmed and untrimmed configurations under typical supersonic conditions and to verify the numerical calculation results of supersonic static and dynamic aerodynamic characteristics of the capsule. Transonic and supersonic dynamic characteristics of blunt body entry vehicles are difficult to calculate by numerical methods, since transient and unsteady flow phenomena such as separation, reattachment, wake, and time-delay are hard to capture accurately. There are three types of tests, i.e., forced oscillation, free oscillation, and free-flight. Blunt bodies, such as Tianwen-1 Mars entry capsule itself, are sensitive to disturbances in transonic and supersonic flows
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