Why Do Rockets Curve When Launched Instead Of Going Straight Up?

When you were a kid, how did you think rockets worked? They blast off from a pad straight up, and then they're in space, right? The assumption makes sense — after all, straight up is where space is, and it seems like shooting straight up would be the fastest, simplest way to get there. However, as anyone who's actually watched a rocket launch can tell you, they do not fly straight up.

Rather, a launched rocket follows a distinct curve after it blasts off, gradually appearing to fly horizontally to us on the ground. It seems odd from our angle; surely just flying sideways wouldn't get you to space. The reality, however, is that curving the trajectory is the only way a rocket can hope to breach the bulk of the atmosphere into orbit. If a rocket did try to shoot straight up the way we assume, it would just fall right back down to where it was, possibly falling on top of something or someone.

You might think that a rocket's massive thrusters would be more than enough to get the craft beyond the atmosphere, but no matter how powerful they are, there's an equal or greater force working against them: gravity. Gravity would very much prefer that stuff on Earth stays on Earth, and as a rocket attempts to escape, it's constantly yanking down on the entire structure.

The rocket's thrusters are definitely powerful, more than enough to exceed the exerted force of gravity and fly upwards. This is why rockets are launched vertically, to generate as much downward thrust as possible. However, those thrusters are extremely resource-hungry, gobbling up fuel and power in record time. As soon as they start to lag, gravity will reassert itself, and quite violently. This is why a rocket can't escape to orbit on vertical thrust power alone — it'd never make it before the power starts to drop and gravity forcefully drags it back down to the launchpad with a violent crash.

If a rocket's thrusters aren't enough to escape Earth's gravitational pull and enter orbit, how does flying at an angle help? The important thing to remember is that "down" is not a universal direction. Gravity is always trying to pull us back toward Earth's center, but by curving a rocket's trajectory, we can use gravitational shifts to actually maintain a flight path out of the atmosphere. This is a maneuver commonly known as a "gravity turn."

The initial vertical launch of the rocket helps to get it through the thickest layer of the atmosphere, where both gravity and air resistance are still in full force. As it reaches the outer layers, the rocket begins to turn, gradually switching from vertical to horizontal thrust as it angles toward a line of orbit. Orbit isn't quite the same as full-on zero-gravity; when the rocket has reached a state of orbit, it's just far enough away that it's still technically being held by Earth's gravity, but because the force of gravity is weaker out there and the rocket is still carrying its launch momentum, gravity can't pull it toward Earth's center. Think of it like a toy plane that you're spinning around on a long rope. It's still attached to you, but because it's moving so fast, it maintains a horizontal ring around you instead of falling. Of course, this is all assuming that orbit is the goal, while something like an interplanetary launch would require a lot more work and planning like finding a perfect launch window.