Actually that image perfectly represents the concept. To get to the moon they had to abandon puller rockets (like the one in the image), and use pusher rockets

Actually that image perfectly represents the concept. To get to the moon they had to abandon puller rockets (like the one in the image), and use pusher rockets instead. That isn't just a higher tree, that's completely re-imagining the way a rocket works. So "higher trees" might be a good way to learn how to re-engineer the idea so that you can get to the moon.