Shell 73 works ok if you give them a set velocity command to make them go straight down, like: _shell = "shell73" createVehicle [x,y,z]; _shell setVelocity [0, 0, -50]
Just make [x,y,z] whatever position you need. Also, make the setVelocity command have whatever values you want. Just make sure the z value is negative to make sure there is some downward velocity vector.