
These 3 inch rockets are designed to be fired aft from a plane to eliminate the effect of forward motion. Allowing the signal to fall straight down. This is called retro-firing.
The rockets have the 3 inch Heads Mk 5 Mod 1 and use the Motors Mk 2 or Mk 3. With the Motor Mk 2, they weigh 4.8 pounds; with the Motor Mk 3, 4.6 pounds. They use the Launcher Mk 2.
Firing of the rocket motor initiates a delay train in the signal in the head, which delay sets ofT the flare 10 to 20 seconds later. The motor separates from the head during the free fall, and the signal hits the water and floats on it, burning from 10 to 15 minutes.
Nothing else to see.
OP 1664, Volume 1 - US Explosive Ordnance (1947)