回复48楼:Why are they still useful in the satellite era?
According to defence and security analyst Professor Michael Clarke, the biggest advantage of spy balloons over satellites are that they can study an area over a longer period of time.
\"The advantage is they can stay in one place for a long time,\" he told Sky News.
\"Because of the way the Earth rotates, unless a satellite is over the Equator, you need three to five satellites going all the time to track the same spot.
\"These balloons are also relatively cheap, and much easier to launch than a satellite.\"
Will balloons continue to be used in future for spying?
Very much so, according to Professor Clarke.
Despite the wide use of satellite technology, countries including the UK are also focusing on the development and use of spycraft to operate in the upper atmosphere.
In August, it was announced the Ministry of Defence had agreed a £100m deal with US defence company Sierra Nevada to provide high-altitude unmanned balloons to be used for surveillance and reconnaissance.
这是英国天空台的解说。你可以看看。重点就是高纬度，无人，重点是inflatable。 你说的飞艇和气球都算吧。不是么？

来自留园官方客户端

......Aeroscraft之类的飞艇,有前途
无法控制方向的气球,有啥意义