Chapter 1: How Rockets Really Fly

A gentle note: “rockets push against the air to move”

It is often thought that a rocket flies by pushing against the air, the way we push against the ground to walk. But rockets fly best in space, where there is no air at all. A rocket moves by pushing against its own gas: it throws gas backward, and the gas pushes it forward. It needs nothing outside itself to push against.

Story Time — The Weight of Every Gram

Karthik · near Sriharikota

Karthik, who had watched a launch as a younger boy, now visited Sriharikota on a school trip, older and full of questions. An engineer named Ms Rao showed the class a towering model of a rocket. “Why is it built in sections?” Karthik asked. “Why not one long rocket?”

Ms Rao smiled. “That is the best question a rocket engineer can ask. Most of what you see here is fuel — heavy, heavy fuel. Once the first section has burned its fuel, that empty section becomes dead weight. So we drop it.” She mimed releasing a stage. “Lighter now, the rocket climbs faster.”

“We fight for every gram,” she went on. “Every extra kilogram we carry needs more fuel to lift, and that fuel has its own weight to lift too. So engineers remove everything they can. A rocket is a machine built at the very edge of what is possible.”

Karthik thought about the balloon experiments of his childhood. “So it still just pushes gas down to go up — like a balloon?” “Exactly the same idea,” Ms Rao said, “but controlled with enormous power and great care. The gas leaves the engines faster than a rifle bullet.”

“And to leave the Earth completely?” Karthik asked. “It must reach escape speed — about forty thousand kilometres in a single hour,” she said. “Slower than that, and the Earth pulls it back. That is the mountain every rocket must climb.”

On the bus home, Karthik filled a page with sketches of staged rockets, each section falling away. He was no longer just a boy who loved to watch launches. He was beginning to understand them — and he wondered whether, one day, he might help design them.

Story Time — The Balloon and the Corridor

Diya · Mumbai

Diya's science club set a challenge: send a balloon the length of the school corridor using no hands, no batteries, nothing but the balloon itself. Diya remembered the balloon rocket she had made as a child and grinned.

She threaded a long string down the corridor, taped a straw to an inflated balloon, and let go. It shot forward — but stopped halfway. “Not enough,” she muttered. She tried a bigger balloon; it went further. Then she tried releasing the air through a narrower nozzle, and it flew fastest of all.

“Why did the narrow opening help?” a clubmate asked. Diya thought carefully. “The air came out faster and more forcefully. More push out the back means more push forward. It is thrust — the same thing that lifts a real rocket.”

Her teacher, watching, added a thought. “Notice something, Diya. Once the balloon empties, it stops pushing and simply glides. A real rocket is the same: its engines fire only for a short while. After that, it coasts, carried by the speed it has already gained.”

Diya recorded her results like a true engineer: balloon size, nozzle width, distance travelled. “A rocket,” she wrote at the top of her page, “is just a very serious balloon.” Her teacher laughed — because, in the simplest sense, she was not wrong.