Discovery 2 was the uncompleted unseen counterpart of the Discovery 1. It was intended to be used in order to retrieve and return David Bowman and Frank Poole, from Discovery 1 back to Earth. The other three members of the original Discovery mission were to remain and study Jupiter and TMA-2. But due to complications initiated by the Discovery 1's computer HAL 9000, the entire crew of the original Discovery went dead or missing. With this lack of immediate need to complete the ship, Discovery 2 went uncompleted for nine more years. Eventually, Walter Curnow took charge of the reactivation and completion of the new vessel. However, this ship was eventually replaced by the already completed Cosmonaut Alexei Leonov, which was built by the Soviet Union.