What is the maximum duration for intentional zero-G flight?

The correct answer indicates that the maximum duration for intentional zero-G flight is 5 seconds. This limit is primarily due to safety considerations and the physiological effects on the human body. In a zero-gravity environment, even brief exposure can lead to issues like disorientation and difficulty in control. Therefore, the duration is kept short to mitigate these risks while still allowing for practical applications in both training and experimentation.

Longer durations could increase the likelihood of adverse effects on individuals or complicate maneuvers in situations where precision is critical. Hence, the 5-second rule is a balanced approach that provides an opportunity for effective zero-G experiences without exceeding the safety threshold.