Why do we have to fly rockets straight up and out of the atmosphere? Why can’t we fly a ship like a plane and just go higher and higher and higher, then rocket booster out past the exosphere. I know the air is thin way up there, so at the highest, tilt upwards and rocket boost
In: Engineering
Getting into space isn’t about getting high up. It’s about going really really fast horizontally so the arc of your trajectory causes you to continually miss the ground as the earth curves away from you. The only reason why rockets go up at all is because they want to get out of the atmosphere (or at least to the very thin parts of it) so drag doesn’t slow them down.
So flying up into the atmosphere doesn’t really help achieve this objective all this much, other than slightly reducing the initial drag force. Planes need air to provide lift. The higher go, the less they can lift, so the smaller the payload they can lift. So an aircraft very quickly becomes ineffective at lifting any sizable rocket up into the air. In theory air-launch can be more efficient than vertical launch for some smaller rocket sizes, so they have been attempted. But the margins are actually quite small. And the maneuver from horizontal to vertical often requires added aerodynamic surfaces to perform, which means the added drag and weight of these features offset the theoretical efficiency gains made. They just aren’t worth the added engineering complexity.
As it turns out, the best vehicle for lifting a small rocket up high above the ground is a bigger rocket. This is basically what a two-stage rocket is.
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