A model of a rocket capable of interplanetary exploration.
In this historical photo from the U.S. space agency, a 1963 model of a thermonuclear rocket capable of interplanetary exploration. The reactor was used to heat up liquid hydrogen for thrust similarly to traditional rocket engines. The large heavily shielded zone between the reactor and the crew cabin protected the astronauts from the radiation.
For more information browse the Plum Brook Facility Page.
Each weekday, SPACE.com looks back at the history of spaceflight through photos (archive).