WASHINGTON — More than half of the nation’s aircraft carriers are not currently ready for deployment, as the massive ships sit off the Virginia coastline in various states of repair or testing.

The U.S. Navy has 11 aircraft carriers, more than any other nation. Six of them are currently docked off the Virginia coast and only one is ready to deploy. Another is undergoing maintenance on the Pacific coast. The hulking warships serve as mobile airbases at sea and can allow U.S. forces to fly into areas swiftly, without a complicated process of getting permission to set up on land in neighboring nations.

The carriers are supposed to be on a three-year schedule that rotates deployment, scheduled maintenance and repair, so that some carriers are always in strategic places at sea and others are ready for deployment, if a fast response is needed for a global problem.

Democratic Rep. Elaine Luria, a Navy veteran who represents Virginia’s 2nd congressional district in Hampton Roads, sees some of the carriers in base when she checks in on the Norfolk waterfront in her district. Luria is concerned the Navy is not keeping up with its schedule for the aircraft carriers.

“We have not been able to generate the deployable forces one would expect,” Luria said in an interview Friday with the Mercury. “You have 11 carriers, six of them are on the East Coast and only one can deploy and it is deploying late, I don’t think that is generating good deployment capability or surge capability to respond where we need to respond around the world.”

An Air Force engineer and his team are offering one idea in an era of school and workplace shootings -- a sturdy, portable, yet affordable door barricade.

Dayton-based S9 Engineering Technology Corp. last month completed a patent license for the commercial rights to the device -- dubbed the "Fortress" -- invented at the Air Force Research Laboratory (AFRL), which is headquartered at Wright-Patterson Air Force Base.

Co-inventor Matt Srnoyachki -- founder of S9 Engineering and a mechanical engineer in the AFRL's 711th Human Performance Wing -- brought a pair of the devices to a recent interview, easily holding them folded up in one hand.

Don't be fooled by the size of this "fortress." The military-spec invention is meant to be placed firmly between a door frame and a door's striker plate, securing a metal block that prevents intruders from pushing a door open. The metal block can be pivoted shut or opened easily from the inside.

Those who insert the device and lock it in place can flee to safety elsewhere, or simply move away from a closed door.

There aren't a lot of options in mass-shooting situations -- fight, flee or hide. No device in these scenarios can be completely foolproof, Srnoyachki acknowledges. The device does nothing for windows. And an armed intruder can still shoot into a locked door or attempt to smash that door open.

But Srnoyachki and his colleagues believe this device will delay almost any intruder -- giving first responders, teachers, students and others additional minutes.

"We've been researching active-threat situations since 2015," said Srnoyachki, who has worked for AFRL since 2011 as a contractor. "What we've learned is, these are very time-critical situations. And unless there's a motive behind the assailant, then he's going to try to get into the door for a moment -- then if he can't really get in, he's going to keep moving."

Srnoyachki said the invention has been tested against "just about every single portable travel lock, portable door lock that you can find on the market."

"We found deficiencies with all of them," he said. "We were either able to kick through them very easily; they were made poorly; they didn't fit in the doors that we commonly see."

This door lock is effective in "90 percent of the commercial door frames that we found, both industrial and household," he added.