The year 1986 was notable for two big disasters, both of them attributable to human error and bureaucratic negligence at competing super powers: the Chernobyl nuclear accident in the Soviet Union and the explosion of the Space Shuttle Challenger in the United States.The journalist Adam Higginbotham wrote about Chernobyl in his 2019 book, “Midnight in Chernobyl.” Now he’s back, with a look at the American side of the ledger, in his new book, “Challenger: A True Story of Heroism and Disaster on the Edge of Space.” On this week’s episode, Higginbotham tells host Gilbert Cruz why he was drawn to both disasters, and what the Challenger explosion revealed about weaknesses in America’s space program.“There was certainly a lot of hubris and complacency that led into this accident,” Higginbotham says. “In complex decision-making processes like those leading to the Chernobyl accident and the Challenger disaster, those concerned with making the decisions start off with a series of extremely carefully governed and defined practices for what constitutes acceptable risk and normal behavior. And then gradually over time, they subtly and almost unconsciously expand what they deem to be acceptable without even realizing it."