The year 1986 was notable for two big disasters: 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.