He entered the space program in 1958 as project engineer for the design of the Mercury spacecraft.

The Mercury spacecraft could hold only one astronaut and had limited capabilities.

The new capsule also needed to have more maneuverability than the Mercury spacecraft.

Twelve companies bid to build the Mercury spacecraft, an unusually high number for a $20 million contract, given the project's great prestige.

Because of their small size, it was said that the Mercury spacecraft were worn, not ridden.

There were five other manned missions using Mercury spacecraft.

He oversaw the development of the Mercury spacecraft and made the flight assignments for the first astronauts.

The Mercury spacecraft had now been qualified to carry a human into orbit.

The Mercury spacecraft was unmanned and carried no launch escape system.

The launch escape system saved the Mercury spacecraft from destruction.