The coalition’s members insist the scenario is a real threat, and not the plot of a Michael Bay movie or a Cormac McCarthy novel. They believe a single nuclear blast at 300-400 kilometers in altitude—about the height of the International Space Station—could take down all power in the U.S. Even an explosion just 30 kilometers up would take out the Eastern grid, which supplies three-quarters of the country’s power.

What happens post-detonation is not a pretty picture, Pry says: “You’d have massive industrial accidents. One hundred four nuclear reactors going Fukushima, spreading toxic clouds everywhere. Oil refineries burning down, oil pipelines exploding.… Airliners crashing down.”

That’s just day one. With no power, the country would lose transportation, our food would go bad and we’d lose the communication tools we’ve come to rely on. To envision what that would look like, just picture New Orleans after Hurricane Katrina, Pry says.

The coalition estimates that we’d lose up to 90 percent of our population within a year.