To investigate the envelope radiation characteristic of stratospheric airship, three kinds of airship models with different dimensions (fineness ratio of 3, 4, 5) are selected. After establishing the thermal equilibrium equations of the selected models, the influence of the envelope radiation characteristic on the envelope and airship gas is first addressed to determine the optimal fineness ratio by considering the flight dynamics characteristics. Furthermore, the effects of envelope emissivity, envelope absorptivity, solar cells radiation characteristics, and typical envelope materials on the envelope radiation characteristics of airship are discussed in depth. The results show that: (1) With the assumption of same absorptivity and emissivity, the larger the fineness ratio of the airship, the smaller the diurnal temperature difference of the main helium gasbag, and the better the thermal characteristics of airship as well. When the envelope radiation characteristics vary, the temperature difference of main helium gasbag with a fineness ratio of 4 in one day is always less than 1 K, compared with the fineness ratio of 5. However, the temperature difference of main helium gasbag with a fineness ratio of 3 exceeds that with the fineness ratio of 5, and reaches its maximum of 6 K. Therefore, the fineness ratio of 4 is regarded as optimal by considering the floating constraints of low drag and high buoyancy. (2) In the case of higher long-wave emissivity and lower short-wave absorptivity of the envelope material and solar cells, the diurnal helium temperature difference is the smallest, and the thermal performance of the aerostat is better. (3) Among the five typical envelope materials, i.e., white Tedlar film, white PU film, silver-plated Teflon film, aluminized PET film, and white PVF film, the aluminized PET film is more conducive to controlling the helium temperature difference and reducing the volume change of gasbags. The aforementioned results can provide a theoretical basis for improving the thermal performance of stratospheric airships.

为了研究平流层飞艇的包络辐射特性，选择了三种不同尺寸（细度比为3、4、5）的飞艇模型。在建立所选模型的热平衡方程后，首先解决包层辐射特性对包层和飞艇气体的影响，结合飞行动力学特性确定最佳细度比。此外，深入讨论了外壳发射率、外壳吸收率、太阳能电池辐射特性以及典型外壳材料对飞艇外壳辐射特性的影响。结果表明： (1) 在吸收率和发射率相同的假设下，飞艇的细度比越大，主氦气袋的昼夜温差越小，飞艇的热特性也越好。当包层辐射特性变化时，细度比为4的主氦气袋一天内的温差始终小于1K，而细度比为5的主氦气袋的温差则小于1K。细度比为3时超过细度比为5，达到最大值6K。因此，考虑到低阻力和高浮力的浮动约束，细度比为4被认为是最优的。(2)在外壳材料和太阳能电池长波发射率较高、短波吸收率较低的情况下，昼夜氦温差最小，并且浮空器的热性能更好。(3)在白色Tedlar膜、白色PU膜、镀银Teflon膜、镀铝PET膜、白色PVF膜五种典型信封材料中，镀铝PET膜更有利于控制氦温差，降低气囊的体积变化。上述结果可为提高平流层飞艇的热性能提供理论依据。