Flare
A flare was a small combustible rocket, similar to a firecracker, which was used to send a distress signal.

In 2267, Montgomery Scott compared Spock's jettison and ignition of the remaining fuel in the shuttlecraft  to sending up a flare. ()

See also 
Injector flare
Microfusion flare
 (weapon)
 (natural)
Solar flare
Warp flare

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