But even if the ice melts as fast as shippers hope ( and scientists fear ) , navigation is likely to demand strengthened hulls , higher insurance and extra training for crews , all adding to the costs .
It is also possible to design hulls that include air-trapping recesses a couple of metres deep .
同样还可以设计一种携带有长度在几米左右的锁气凹槽的船体。
This pod could help reopen orbits that are currently inaccessible to future spacecraft due to the amount of shredded metal and empty hulls of dead satellites floating around .