The curious 6 year-old sitting next to me asks "how do you build a rocket?" What kind of rocket? "A big rocket that flies".

(He came by when I was answering a question and he was very excited when I explained that this is a site is for asking questions when you're stuck and people from all over the world try to help and answer them.)

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    $\begingroup$ It is a nice "Space Technology Educator" question :-) $\endgroup$
    – peterh
    Jun 9, 2018 at 11:13

1 Answer 1


A rocket is a giant fuel tank, with an engine at the bottom, fancy pumps to push fuel into the engine (really fast, as much as a few tons of fuel per second), and a computer so it can fly correctly.

A rocket on TV is actually two rockets, a big rocket on the bottom, with a small rocket on top.

Both the big and the small rocket have powerful engines that burn the fuel and shoot the really hot exhaust out the back through those big nozzles. The engines can tilt a bit and that's what the computer uses to steer.

The walls of a rocket are thin so they aren't too heavy, but strong so they don't bend when they push through the air really fast. Most of the weight of the rocket is just fuel.

The job of the big rocket is to get the small rocket up above the atmosphere, and then turn and start to move sideways fast. Once it's empty, it disconnects because it's so heavy. That takes about three minutes.

The small rocket then speeds up even more so that the satellite in its nose cone will stay in orbit around the Earth once it's released. The rockets that took people to the moon actually used three rockets stacked on top of each other!

A rocket has lots of cameras and detectors and radios installed so its computer steers it properly, and so it can communicate with people back on the ground.

The big rocket also has a self-destruct device, so if it steers the wrong way, it can be stopped before it crashes into anyone.

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    $\begingroup$ I've made this a community wiki so that anyone can edit this, maybe just try to keep it simple though. Anyone can post a new answer as well, which would be ideal if you have a different approach. $\endgroup$
    – uhoh
    Jun 9, 2018 at 11:14
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    $\begingroup$ Thanks! He had a big smile on his face and I learned a lot too. $\endgroup$ Jun 9, 2018 at 11:51
  • $\begingroup$ CSM's engine was used for course corrections and Lunar orbita insertion, and it was on top of the saturn stack so that's a fourth rocket to get to the moon ;) (a fifth was used for lunar landing and a sixth for taking off, but they didn't and couldn't come off the stack, and weren't needed to get to the moon so not count them is OK) $\endgroup$
    – user20636
    Jun 9, 2018 at 13:28
  • $\begingroup$ @AnthumChris I'm glad you guys enjoyed it! By the way, as a followup to "...strong enough so they don't bend when they push through the air..." have a look at the question If not constrained by underpasses, etc., would Falcon 9 have been less of a flying noodle? and also Just how much can tall skinny rockets bend? (roughly, safely) and see a GIF of a rocket bending! $\endgroup$
    – uhoh
    Jun 9, 2018 at 17:12
  • $\begingroup$ @CamilleGoudeseune nicely done! $\endgroup$
    – uhoh
    Oct 7, 2020 at 4:12

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