On March 18, 1965, cosmonaut Aleksei Leanov left his spacecraft during an orbit around the earth and became the first person to walk in space. In 1969, Neil Armstrong took the first human step on the moon. And in 1984, Bruce McCandless became the first "human satellite," using a Manned Maneuvering Unit to walk in space without being fettered to a spacecraft. All three men participated in what is...