This spacecraft is being readied for a one-way mission to deflect an asteroid

In a clean room in Building 23 at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland, a spacecraft called DART was splayed open like a fractured, cubic egg. An instrument called a star tracker—which will, once DART is in deep space, ascertain which way is up—was mounted to the core, along with(…)