What criterion must a launch site meet regarding maximum altitude?

The correct answer indicates that a launch site must be positioned at least one-quarter of the expected maximum altitude. This criterion ensures that the safety and operational integrity of the launch are maintained. It establishes a buffer zone that allows for the potential variability in the launch trajectory and atmospheric conditions, which can affect the actual altitude achieved during flight.

When a launch site is located at or above this threshold, it can help minimize risks associated with nearby populated areas or critical infrastructures. This requirement also aligns with broader safety regulations and oversight by agencies responsible for managing airspace and ensuring the safety of both the launch vehicle and any potential recovery operations.

The criterion provides a structured approach to site selection, promoting safe and responsible launch practices by ensuring that launch operations operate well within established safety margins.