Although the airship starts off flaccid , the helium and the ethane expand as it gains altitude .

尽管飞船松弛着就起飞了，氮气和乙烷随着海拔的增长逐渐膨胀变大。

And it has rejuvenated several industries , including petrochemicals , where ethane produced from natural gas is a feedstock .

这其中就包括石化产业，其原料之一就是从天然气中提取出的乙烷。

And since ethane has roughly the same density as air , the fuel in effect weighs nothing , further reducing the amount of helium needed to create buoyancy .

由于乙烷和空气的密度大体相当，燃料的重量没有什么多大的影响，进一步减少氮气的重量需要去产生浮力。

This is because air is pumped back into the tail envelopes as the ethane fuel is burned by the craft 's thrusters , and is also pumped into the tail and head during descent as the inner envelopes contract .

这是因为当飞艇推进器燃烧乙烷燃料时，空气从尾部的封皮灌入，而且同时当内层封皮缩小使飞船下降的时候，空气从尾部和头部灌入飞船。

In fact , many scientists believe that warming of the earth occurred at much higher levels than those seen today due to the presence of gases like carbon dioxide ( co 2 ) , methane , ethane or ammonia .

事实上，许多科学家认为：由于象二氧化碳、甲烷、乙烷、氨等气体的存在，当初地球上所发生的变暖情况比当今严重得多。