Engineering is Awesome
This Giant Tube Stopper Will Plug Flooded Subways and Choke Off Gas Attacks 
Numerous metropolitan subway systems around the country include spans that pass under bodies of water. If one of those lines were to spring a leak, the resulting flooding could be catastrophic. The Department of Homeland Security might have developed the answer—a giant, inflatable tube plug.
Earlier this year, the DHS Science and Technology Directorate, led by Dr. John Fortune, working in conjunction with teams from Pacific Northwest National Laboratory, West Virginia University (WVU) and ILC Dover, successfully demonstrated the new Resilient Tunnel Project (RTP) system.
The RTP is a large inflatable cylinder 32 feet long and 16 feet wide. It’s designed to store in the tunnel’s ceiling, then descend and expand to seal that section of tunnel. The plug, filled at 17 to 25 psi, is strong enough to hold 35,000 gallons of water—enough to fill a medium-sized residential swimming pool. Local authorities would be able to remotely activate multiple plugs along the impacted line.
The RTP is constructed of three layers of material. The outermost layer, made of webbedVectran polymer fiber, provides the overall shape of the plug. The two inner layers are made of solid Vectran and polyurethane, respectively. They are designed to provide the actual seal—not just for the flood waters on the outside, but also the air and/or water used to inflate the device.

gizmodo

This Giant Tube Stopper Will Plug Flooded Subways and Choke Off Gas Attacks

Numerous metropolitan subway systems around the country include spans that pass under bodies of water. If one of those lines were to spring a leak, the resulting flooding could be catastrophic. The Department of Homeland Security might have developed the answer—a giant, inflatable tube plug.

Earlier this year, the DHS Science and Technology Directorate, led by Dr. John Fortune, working in conjunction with teams from Pacific Northwest National Laboratory, West Virginia University (WVU) and ILC Dover, successfully demonstrated the new Resilient Tunnel Project (RTP) system.

The RTP is a large inflatable cylinder 32 feet long and 16 feet wide. It’s designed to store in the tunnel’s ceiling, then descend and expand to seal that section of tunnel. The plug, filled at 17 to 25 psi, is strong enough to hold 35,000 gallons of water—enough to fill a medium-sized residential swimming pool. Local authorities would be able to remotely activate multiple plugs along the impacted line.

The RTP is constructed of three layers of material. The outermost layer, made of webbedVectran polymer fiber, provides the overall shape of the plug. The two inner layers are made of solid Vectran and polyurethane, respectively. They are designed to provide the actual seal—not just for the flood waters on the outside, but also the air and/or water used to inflate the device.

gizmodo