Dual deployment in model rocketry is where you eject two parachutes out o' t' rocket. Well, blow me down! A small one at apogee (the peak o' t' trajectory) so that t' rocket comes down quickly. Well, blow me down! But t' keep it from touchin' down too fast, matey, you pop out a big chute when t' rocket is close t' t' ground. Avast! T' use o' two chutes usin' this method prevents t' rocket from driftin' too far.