// Set the speed of the bullet that was just shot
    private void setBulletSpeed(GameObject bullet, float speed)
    {
        linear_travel LT = bullet.GetComponentInChildren <linear_travel> ();

        if (LT != null)
        {
            LT.setSpeed(speed);
            return;
        }

        // seeking_missile starts with 0 velocity
        // sin_travel starts with fixed velocity
    }