• nitroemdash@lemmy.wtf
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    18 hours ago

    At 99°C (210°F) the lift power of hot air balloon is 0.25 kg per m³. Pillars supporting a four kilometre long suspension bridge section are under 200 MN vertical load, or 20 million kg. The air balloon would have to be 80 million m³ large, or 534 m (⅓mi) in diameter.