In Rich Bishop's nightmare, someone flies a drone over Port Tampa Bay and drops an explosive device on a gas tank, causing massive destruction.Feeding this scary scenario is that law enforcement agencies already have received calls about drones over the port, said Bishop, a former strategic planner at U.S. Special Operations Command, speaking at a defense technology summit in Tampa this week."Imagine one of those drones was carrying a thermite grenade and dropped it on a gas tank," he said. "Right now, we don't have the ability to take one of those down."No immediate security risks arose with drones seen flying over Port Tampa Bay, said Mark Dubina, vice president of security for the port. Still, Dubina said, "in general, critical infrastructure has concerns of people flying drones over their facilities."The nightmare came true in Ukraine, where Russian drones dropped thermite grenades — generating a massive amount of heat — on a Ukrainian ammunition dump and forced the evacuation of 30,000 people, the British newspaper Daily Mail reported.Bishop, who now runs RAS-2, a Tampa-based defense contracting firm, said the military shares his concerns."I predict if not by the end of 2017, certainly by next year, unmanned aerial vehicles will become the No. 1 threat," said Bishop, leading a panel on drones at the Defense Technology Innovation Summit, running through today at the Tampa Convention Center. "The damage this can cause is tremendous."The proliferation of drones is a concern, with one report saying 19 nations already have armed versions of the unmanned aerial vehicles, said panel member Johnny Hester, a retired Army colonel who operated drones."The age of the armed drone has arrived," Hester said. Drones have been used by ISIS to kill and conduct surveillance on Iraqi forces, he said."My personal opinion is that we are not moving fast enough to counter this threat," said Hester, who now works at Obsidian Solutions Group, a Tampa defense contractor.There are no easy answers to counter drones, the panelists agreed. They asked for help from industry, academia and other innovators attending the summit.The military is looking at several options, said Army Col. Dawson Plummer, deputy chief of acquisitions for the Joint Improvised-Threat Defeat Organization.Plummer noted that his agency, once responsible for defeating improvised explosive devices, now has responsibility for doing the same with drones.In February, during a "hard-kill challenge," the military looked at a wide range of antidrone options, from directed energy devices like lasers to net guns, Plummer said.There are other methods, including finding and exploiting vulnerabilities in hardware and software to take over or crash a drone, said Anthony Cochenour, president of Hoplite Industries Inc. But even technology that's shown promise — like a system that can detect drones, determine if they are friendly, and blast them out of the air with lasers if not — has limitations.Such technology is extremely expensive and requires a great deal of energy to operate, said Scott Ramsey, senior research scientist at the Naval Research Laboratory.Local law enforcement could never afford them, said Bishop, the former SOCom strategic planner.And there is only so much law enforcement can do to counter drones, said Larry McKinnon, Hillsborough County Sheriff's Office spokesman.It's unclear how many reports of drones at the port have been made, but Hillsborough deputies responded to one call there about a small drone launched from a nearby park that accidently hit a boat in the channel."How do you stop someone who parks a car and puts a drone up in the air?" McKinnon asked. "You can't stop that anymore than you can stop someone shooting out of a hotel window."Contact Howard Altman at [email protected] or (813) 225-3112. Follow @haltman.