Why do missiles have fins, while modern space rockets don’t?
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A missile with fins flies a bit like a bird with tiny wings being pushed VERY hard. It can use its tiny wings to turn because it’s moving VERY fast so it’s little wings do more, like when you stick your hand out the car window when you’re going fast.
That’s not a good use of energy though, because if instead you can turn the thing pushing the missile very hard it will turn faster and more accurately. Then the best use of a fin is to keep it from turning *too* fast. Like when you balance a stick on your hand if you move your hand too fast it falls over, the fins keep the rocket motor pushing the missile from “pushing it over” where it would just spin in circles until it goes out, like those fireworks.
BIG missiles, like the rockets that go to space, are VERY heavy. The motors pushing them are very strong but they don’t get moving very fast right away. They also don’t really need to make sharp turns. Mostly they need to go almost straight up for a bit, and then make a gentle slow turn to line up going in a circle around the earth. Even though they get started slow they just keep going faster, but the amount of time they spend in the air is actually very short, and the time they spend in the air at a speed where a fin would be useful is even shorter. Since they’re so big and so heavy once they get going it’s pretty hard for them to turn anyway, and they only turn a little bit. They just don’t need fins.
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