2. 外语
  3. A project likely to evolve in. the near or intermediate future is space tourism, a purely【B1】______ activity that would not have

A project likely to evolve in. the near or intermediate future is space tourism, a purely【B1】______ activity that would not have

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问题     A project likely to evolve in. the near or intermediate future is space tourism, a purely【B1】______ activity that would not have to rely on unpredictable government decisions. It would 【B2】______ put space operations on a much more solid, dependable footing and would enormously【B3】______  man’s space activity. While some people see space tourism as a【B4】______ multibillion-dollar business, difficult technical problems remain to be【B5】______  
    First, a manned reusable rocket like the Venture Star must be built. Then, a second serious problem must be【B6】______ : even today’s most-advanced space rockets are able to【B7】______  only about 2.5% of their launch weight into orbit-- a ratio that has hardly changed in the last 40 years. This fact is a result of the【B8】______ of material characteristics and chemical power sources, and【B9】______ .
    Today the price of a ticket to space would have to be at least ＄ 50 000. It is questionable【B10】______ . However, space tourism may become more attractive once space facilities are built【B11】______ .
【B4】
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