返回舱跨声速自由飞行的静动稳定性

采用运动自由度不受约束的风洞自由飞试验技术，研究大钝头、小升阻比的类"联盟号"返回舱在跨声速区自由飞行时的运动特性与气动特性规律。以单平面光路拍摄返回舱模型在风洞中自由飞动态运动过程图像，经图像自动判读获取其运动轨迹与姿态角，并以参数微分法对模型运动姿态角进行线性与非线性气动参数辨识，得到模型俯仰方向的静、动稳定导数系数。研究结果表明:采用线性与非线性气动参数辨识所获得的静稳定导数系数C_mα均小于零，在数值上差距不大；从非线性气动参数辨识结果看，返回舱静稳定导数系数的数值主要由线性项C_mα0决定，非线性项C_mα2α2所占比例较小；类"联盟号"返回舱静稳定导数系数的非线性较弱，可近似用线性气动模型进行辨识。在试验迎角范围内，返回舱的动稳定导数系数呈现出非线性性质，且在小迎角范围内由线性项决定，在大迎角范围内主要由非线性项主导。

Free flight static and dynamic aerodynamic characteristics for re-entry capsule at transonic speed

This paper studies the motion and aerodynamic characteristics of the re-entry capsule with stable fins at transonic speed by the wind-tunnel free-flight test in which the motion freedom is not limited. When the wind tunnel test model flights freely by the observational window, the high speed camera captures the motion image immediately by a single light path, and then the model motion trajectory and attitude angle can be acquired by image acquisition software. Finally, the pitching static and dynamic derivatives coefficient are derived by the parameter differential method from the recorded angular motion of the model of more than two cycles with the linear and nonlinear motion equations. The result shows that the static derivative coefficient C_mα obtained by the linear and nonlinear aerodynamic parameter identification is less than zero and the variation is not significant. From the results of nonlinear aerodynamic parameters identification, the value of static derivatives coefficient of the re-entry capsule is mainly determined by the linear term C_mα0, and the nonlinear term C_mα2α2 is relatively smaller. The nonlinearity of the static derivatives coefficient is weak, which can be approximated by the linear aerodynamic model. The dynamic derivative coefficient of the re-entry capsule is nonlinear in the range of experimental angles of attack. It is determined by the linear term in the range of small angle of attack, and dominated by the nonlinear term in large angle of attack.