Propelled by the power of black gunpowder, the "Wanjin Rocket" reaches a top speed of 150-250 meters per second after launch, starting from 30 meters per second, then drops down to 80-100 meters per second as air resistance increases and the propulsive force weakens.
This speed is just average—it's nothing like modern rocket artillery that all start at 800 meters per second; for example, the BM-30 "Tornado" launches at 850 meters per second. But in the Japan Middle Ages, this is more than enough. Firing from about three li away leaves Kinoshita Shichiro just ten seconds to react.
On land, ten seconds is enough time to pull off a lot of moves—you could even roll out eighteen variations of the "Lazy Donkey Rolling" trick. But at sea, ten seconds isn't enough for a ship to react at all; they can't even tilt their bow slightly.
