温度梯度对大口径反射镜热稳定性公差的影响

Influence of temperature gradient on thermal stability tolerance of large aperture reflective mirror

为了研究温度对大口径SiC反射镜镜面曲率半径和面形RMS值的影响,针对某空间相机2 m口径SiC主反射镜建立了有限元模型,分析了均匀温度场、轴向温度梯度以及径向温度梯度对反射镜曲率半径变化量和面形RMS值的影响程度和规律,通过理论分析和试验验证了仿真结果的准确性。结果表明:温度梯度对反射镜曲率半径和面形RMS值的影响远远大于均匀温度对其的影响,曲率半径变化对轴向温度梯度最为敏感,面形RMS值对径向温度梯度最为敏感。1℃轴向温度梯度引起的曲率半径变化比相同均匀温升引起的曲率半径变化量大48倍。±1℃径向温度梯度引起的面形RMS值可比相同均匀温升引起的面形RMS值大202倍。在确定反射镜热控指标时,必须考虑轴向温度梯度和径向温度梯度对稳定性公差的影响。

In order to investigate the influence of temperature on the radius of curvature and the RMS value of the large aperture SiC reflective mirror,a finite element model was established for a 2 m-aperture SiC primary mirror of a space telescope,and the effects of uniform temperature field,axial temperature gradient and radial temperature gradient on the radius of curvature and RMS of the mirror were analyzed.The accuracies of the simulation method and results were verified by experiment theoretical arithmetic.The results show that the influence of temperature gradient on the radius of curvature and the RMS value of the mirror is much greater than the effect of uniform temperature.The change of curvature radius is most sensitive to the axial temperature gradient,and the RMS value of the surface figure is most sensitive to the radial temperature gradient.The change in radius of curvature caused by the 1℃axial temperature gradient is 48 times greater than the change in radius of curvature caused by the same uniform temperature rise.The RMS of surface figure caused by the±1℃radial temperature gradient can be 202 times larger than that caused by the same uniform temperature rise.The influence of axial temperature gradient and radial temperature gradient on the thermal stability tolerance must be considered in determining the thermal control index of the mirror.