自第一颗人造卫星史泼尼克发射以来，火箭推进剂在超过50年的时间内变化不多。
Rocket propellant has barely changed in the more than 50 years since the launch of the first artificial satellite Sputnik.
这项技术的使用最早出现在20世纪50年代，用于史普尼克3号人造卫星。
The technology was first used on the Sputnik 3 satellite in the 1950s.
向戈登·布朗，戴维·卡梅隆或者尼克·克拉格提问？现在你有个机会成为电视史的一部分。
Got a question for Gordon Brown, David Cameron or Nick Clegg? Now is your chance to take part in television history.
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