What is the alternate launch site criterion?

The alternate launch site criterion is designed to ensure safety and compliance with regulatory standards during rocket launches. The correct answer specifies that the launch site should be no less than 1500 feet above ground level and should be no less than one-half the maximum altitude expected or granted by the FAA.

This criterion is significant because it establishes a clear minimum altitude needed to mitigate risks associated with air traffic and the launch itself. A height of 1500 feet is often chosen in practice to ensure that rockets have a safe clearance from ground-level obstacles and airspace concerns, while the stipulation of being no less than one-half of the maximum altitude expected helps in planning for recovery and potential drift of the rocket.

In contrast, the other choices present different altitudes or proportions that do not meet the safety margins or regulatory guidelines that have been established for rocket launches. For instance, lower altitudes would not provide sufficient safety margins, potentially risking interference with other aircraft, and varying maximum altitude criteria could further complicate launch planning. This makes the specified altitude and relation to maximum expected altitude in this option critical for safe operations.