这些就是目前的原理，迄今为止，除了一些在低海拔的飞行测试，唯一的平流层测试是涉及一个按比例缩小拴在气象气球上的模型。
That is the theory, at least. So far, apart from some low-altitude test flights, the only stratospheric tests have involved a scaled-down version tethered to a weather balloon.
利用流体力学的相似原理，按一定的比例缩小构建出实物模型，这样可以节省试验费用和试验空间。
Finally using hydrodynamics similar principles and by reducing the proportion of a certain kind of model, which would save the cost of experiments and experimental space.
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