How scientists examined the supersonic dynamic traits of the Tianwen-1 Mars Entry Capsule

The Tianwen-1 Mars entry capsule efficiently landed on the floor of Mars in southern Utopia planitia on May 14th, 2021 at 23:18 UTC. One of the largest challenges it confronted is {that a} typical blunt physique such because the capsule suffers dynamic instability in throughout supersonic journey. Investigating the unstable Mach vary of flight and confirming the design of the lander’s aerodynamic form and mass properties was key to realize the Mars entry. In a analysis paper not too long ago revealed in Space: Science & Technology, Haogong Wei from the Beijing Institute of Spacecraft System Engineering performed a ballistic vary check to seize the supersonic dynamic traits of Tianwen-1.

The blunt physique entry capsule of Tianwen-1 was programmed to unfold a trim tab at Mach 2.8 to trim the angle of assault in direction of 0° earlier than parachute deployment at Mach 1.8. However, transonic and supersonic dynamic traits of blunt physique entry automobiles are troublesome to calculate by numerical methods, as a result of transient and unsteady stream phenomena reminiscent of separation, reattachment, wake, and time-delay are exhausting to seize precisely. Therefore, researchers favor learning flight dynamics through floor testing strategies. There are three forms of checks, together with pressured oscillation, free oscillation, and free-flight. However, it’s troublesome to seize correct dynamic traits by pressured oscillation checks since this technique induces appreciable disturbance to the stream discipline. The free oscillation technique can solely be used to acquire the dynamic response in a single diploma of freedom, which is taken into account as a simplified free-flight technique. Thus, the free-flight technique, which displays the true dynamic traits of the dynamical mannequin, is an applicable different.

In this work, the authors performed a free-flight ballistic vary check in an effort to get hold of the static and dynamic aerodynamic traits of Tianwen-1 in trimmed and untrimmed configurations below typical supersonic situations and to confirm the numerical calculation outcomes of supersonic static and dynamic aerodynamic traits of the capsule. The checks have been carried out within the 200m Free-Flight Ballistic Range of China Aerodynamics Research and Development Center. The check medium within the chamber was air. The binocular measurement stations have been put in alongside the mannequin flight path, which might be calibrated and aligned to the worldwide base reference coordinate system earlier than the check. There have been two configurations of scaled check fashions: trimmed (with trim tab deployed) and untrimmed (with trim tab folded).

The identification algorithm of the aerodynamic parameters for the free-flight ballistic vary check was established first: The aerodynamic coefficients of free-flight scaled fashions have been derived by modified linear regression technique based mostly on place and perspective information. The Static and dynamic coefficients have been established below the idea of small angle linearization. Afterwards, the evaluation of the place and perspective, perspective oscillation, aerodynamic pressure, static and dynamic stability of the capsule have been made and the outcomes demonstrated that the ballistic vary test captures the perspective behaviors and aerodynamic traits of Tianwen-1 Mars entry capsule. The obtained pitch and yaw second coefficients have been used to debate the aerodynamic traits of the capsule. The capsule in trimmed configuration is dynamically unstable within the pitch and yaw instructions, whereas the untrimmed configuration is dynamically steady. In each circumstances, the capsule is statically steady in pitch and yaw instructions.

Provided by
Beijing Institute of Technology Press