Inflatable plugs to prevent subway floods

    An inflatable plug designed to prevent terrorist attacks could be used to help keep tunnels and subways from flooding.
    The flood-stopping plugs will be made using some of the same materials and processes that are used to make space suits. The plug will consist of three layers, which will help it maintain pressure, and will have a circumference slightly larger than the tunnel entrance, which will ensure a tight seal. It can be inflated using either air or water.