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在近20年里,通过地面模拟试验的方法,对空间环境中材料的衰变已经进行了很多实验研究。但是由于缺乏专项的飞行实验,很少有可能在实验室结果与轨道环境中获得的真实衰变之间进行比较。地面试验中有一些明显的限制,例如由太阳产生的远紫外线辐射在地面上很难复现;还有对在这一领域中有关氧原子对表面的影响及模拟方法的有限的了解并不可靠。为了研究一系列材料在实际空间环境中的表现,并评估实验室模拟试验的有效性,设计了两次空中试验。第一次安排在LDEF卫星中,该卫星在低地球轨道工作5.5年之后已经回收。另一次是在飞行器外活动过程中安排在MIR空间站的外部,1.1年之后回收,由宇航员带回地面。此两次试验的目的都在于获得有关热控制涂层、聚合物、复合材料和光学元件的衰变的情报资料。将60种材料的大约200个试样曝露在低地球轨道环境条件中,实验室对它们在曝露前后的性能进行了测量。大多数试样在空间环境中保持在静置状态,有些试样在飞行期间维持在机械应力条件之下(聚合物薄膜受拉;复合材料受弯曲)。提供了4个相同的试样的几组试验,用来研究氧原子和紫外线辐射的叠加作用的影响,并将它们与单独受太阳紫外线辐射作用的试样进行了比较。结果获得了有关在轨道上形成的破坏机理的有价值的资料,并导致了更为有效的模拟方法,这些方法在今后将用来更好地预测航天器材料的特性。
In the past 20 years, a lot of experimental studies have been carried out on the decay of materials in the space environment through the ground simulation test. However, due to the lack of a dedicated flight experiment, it is less likely to make a comparison between the laboratory results and the true decay achieved in the orbital environment. There are some obvious limitations in ground tests such as the far ultraviolet radiation produced by the sun that is hard to reproduce on the ground and the limited understanding of the effects of oxygen atoms on the surface and modeling methods in this area is not reliable . In order to study the performance of a series of materials in real space environment and to evaluate the effectiveness of laboratory simulation tests, two air tests were designed. For the first time in the LDEF satellite, the satellite has been recovered after 5.5 years of working in LEO. The other was scheduled outside the MIR space station during an out-flight activity and was recovered after 1.1 years and brought back to the ground by astronauts. The purpose of both tests is to obtain intelligence on the decay of thermal control coatings, polymers, composites and optical components. About 200 samples of 60 materials were exposed to low Earth orbit environmental conditions and the laboratory measured their performance before and after exposure. Most of the specimens remain stationary in a space environment and some remain under mechanical stress during flight (the polymer film is pulled; the composite is bent). Several sets of four identical test samples were provided to study the effect of oxygen atoms on the superposition of UV radiation and to compare them to samples that were exposed to solar UV radiation alone. The results obtained valuable information on the failure mechanisms formed in orbit and led to more efficient modeling methods that will be used in the future to better predict the properties of spacecraft materials.