What does the term "signal missile" refer to?

The term "signal missile" refers to a small rocket specifically designed for signaling and communication purposes. These rockets are typically employed in scenarios where visual signals are required, such as in search and rescue operations or during military exercises to communicate messages over distances. They often produce bright flares or colored smoke to convey information visually.

In contrast, the other options describe different types of rockets or missiles that have distinct purposes. For instance, a type of rocket used for competition usually pertains to those designed for sport rocketry, focusing on performance in competitive settings rather than signaling. A missile used in military applications refers to weaponry intended for offensive or defensive operations, which is not the function of a signal missile. Lastly, a large rocket utilized for scientific research typically encompasses vehicles designed to carry instruments and payloads for exploration or experimentation, diverging from the smaller, communication-focused design of a signal missile.