"Clearly, with flight control facing a learning curve," space historian David Harland has said, "these arrangements were an experiment in their own right."[32] Yet, Kraft proved to be remarkably successful at passing on responsibility to his fellow flight directors—arguably too successful, as Gene Kranz found during his first shift handover on Gemini 4. As Kranz recalled, "He just said, 'You're in charge,' and walked out."[33]