Wrapped in a blanket on his dad’s lap, Jiho watched the white rocket far in the distance.
“Dad, is that thing really going to fly today?”
“Yep, just a few more minutes. Do you know how a rocket actually gets up into the sky?”
“Not really. It’s just… strong?”
Dad laughed.
“Close enough. What actually happens is, the rocket blasts huge amounts of fire and gas straight down, and in return, it gets pushed straight up. Kind of like when you push water backward on a pool float, and the float shoots forward.”
“Oh, I’ve done that in the pool!”
“Exactly that. Scientists call it action and reaction. Push hard on something in one direction, and it pushes you back just as hard in the other.”
A voice crackled over the speakers. “T-minus ten, nine, eight…”
Jiho’s heart started pounding.
“But that rocket looks really heavy. How does something that heavy even lift off?”
“Good question. Most of a rocket is actually just fuel. Over 90% of its weight is fuel that’s going to burn up and disappear. As it climbs, it keeps burning that fuel away, so it gets lighter and lighter the higher it goes.”
“So once it’s all burned up?”
“Then what’s left is just the much lighter spacecraft part. That’s why the very first moment is the hardest, right when it’s still fully fueled and at its heaviest, lifting off the ground.”
“Seven, six, five…”
“Dad, how fast does a rocket have to go to reach space?”
“Really, really fast. About 28,000 kilometers per hour. Fast enough to cross an entire country in the blink of an eye.”
“Whoa.”
“It has to go that fast to beat Earth’s gravity and stop falling back down.”
“Three, two, one…”
The ground seemed to shake. Far away, a burst of white fire spread out, and the rocket slowly, so slowly, began to rise.
“It’s up! Dad, it’s really up!”
“See, all that fire pushing down so hard is exactly what’s lifting it up like that.”
The rocket kept speeding up, climbing through the sky, punching through the clouds, until it finally shrank to a tiny dot and vanished.
“Is it in space now?”
“It’s still speeding up this very second. In a few more minutes, it’ll be completely out of the atmosphere.”
Jiho kept staring at the sky long after the rocket had disappeared.
“I want to ride one of those someday.”
“Then remember what you saw today. The push, the lightness, the speed. Those three things together are exactly what carries a rocket all the way to space.”
“The push, the lightness, the speed — all three have to line up perfectly before a rocket can finally break free of the sky.”
Your Turn Now
Share with someone today what you remember.
- Why does a rocket rise when it blasts fire downward?
- What makes up most of a rocket’s weight?
- How fast does a rocket need to go to beat Earth’s gravity?
(Check when ready: 1. Action and reaction, pushing fire down pushes the rocket up by the same amount. 2. Fuel that mostly burns away. 3. About 28,000 kilometers per hour.)
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