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.

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这个气球飞入平流层，并最终炸开。

The balloon soared into the stratosphere and eventually burst.

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目前对飞船只进行了一些低海拔的飞行测试，平流层的测试则仅仅是由气象探测气球负载着规模缩小的模型原型机来进行的。

So far, apart from some low-altitude test flights, the only stratospheric tests have involved a scaled-down version tethered to a weather balloon.

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