Mark Kelly wrote, “Hey @ElonMusk, when you finally get the nerve to climb into a rocket ship, come talk to the three of us.” Musk had not replied to the senator as of the time of publication.

Kelly, D-Ariz., a retired astronaut, had challenged Musk to climb into a rocket ship by the time the social media spat concluded on Friday afternoon. “Hey @ElonMusk, when you finally get the ...