Which of the following is NOT a requirement for high power rocket launches?

In the context of high power rocketry, having a visible tracking system is not a universally mandated requirement, which makes it the correct choice for what is NOT required for high power rocket launches. The other requirements focus on ensuring safety and compliance with aviation regulations.

Launching rockets into clouds poses risks to both the rocket and existing aircraft, thus making it essential to avoid that scenario. Similarly, not hindering aviation safety is a core principle, as high power rockets must be operated in a manner that does not interfere with air traffic.

Although having an altimeter for altitude tracking is a highly recommended safety feature for monitoring rocket performance, it may not be mandatory depending on the jurisdiction or launch guidelines. In contrast, a visible tracking system, while beneficial, is not enforced in all contexts, hence it stands out as an option that does not have a strict requirement in this setting.