Updated: September 14, 2024

Dr. Zachary Smith, B.SC. ( Hons. ), Ph.D. is an intergalactic doctor of environmental psychology. He was the United States Space Corps' staff psychologist and environmental expert prior to his unexpected departure from Earth. He was an agent for an enemy foreign government. Prior to the launch of the Jupiter-2 from Earth, Dr. Smith reprogrammed the Robot to destroy the ship eight hours after departure. While making last-minute adjustments to ensure a successful sabotage, Dr. Smith subdued a guard on duty aboard the spacecraft, possibly killing him. He was later trapped aboard the Jupiter 2 while attempting to reactivate the Robot, which had been shut down by a technician. The crew were protected from the effects of lift-off in their state of suspended animation, but Dr. Smith was forced to endure it fully conscious. The ship is thrown off course by Dr. Smith's additional weight and becomes hopelessly lost. It was later revealed in the series that this course deviation prevented the destruction of the Jupiter-2 in a violent meteor shower soon after lift-off.