A human space mission must be designed around what people can perceive, endure and do.

Seats, displays, controls, suits, workload, life support, procedures and emergency options all shape whether a trained person can operate effectively inside the spacecraft.

• Can the crew understand the current state?
• Can controls be reached and used under load?
• What physiological stresses must be survived?
• Which tasks should remain human?
• What happens when automation fails?

Alan Shepard anchors the public lesson: the astronaut is a decision-maker and receiver inside the mission, not merely mass at the top of a rocket.