The rocket need not carry people or any payload. It only needa to be big enough to escape earths atmosphere. Why is this so hard to accomplish?
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To escape Earth’s atmosphere means going *at least* 20km up.
So lets assume you can build a rocket, like say a firework (r1) that, without a payload, can get 200m up. That seems like it should be simple enough to achieve.
You then need to build a rocket (r2) that can carry that rocket up 200m before launching it
And a rocket (r3) that can carry that rocket up 200m
And so on, until you reach r10 and you’re launching a massive rocket from ground level in order to lift a slightly less massive rocket, and so on. And at any point if anything goes even slightly wrong the whole thing can explode.
> escapes Earths atmosphere?
Not really the hardest part. You can pile explosives under a manhole cover to do that (in fact they once did yeet one using a nuke but it vaporized due to heating before it left the atmosphere). Staying up in space is the asstastic part – you need to go fast enough sideways that you keep missing the entire planet as you fall. For low Earth orbit that’s about 7.5km/s-ish, so 27000km/h. You need a shitton of fuel to accelerate that much.
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Because rockets are complicated things.
First of all, they need to be pretty big because it takes a lot of fuel to go that high and that fast.
Second, being big means a lot of rocket parts can’t be made in your ordinary machine shop. You need specialized tools, machines, and expertise to make much of the rocket.
Third, they need to be light enough to fly, which means everything in there needs to be optimized. Which means a lot of engineering time and a lot of testing.
Fourth, rocket experiences extreme conditions in operation (heat, forces, vibration, …), which means it needs special materials, and again, special effort in terms of engineering and testing.
Fifth, there’s a bunch of complicated systems in there. Structures, mechanism, hydraulics, electronics, fuel systems… A bunch of stuff needs to work together to make the rocket fly, which again means a lot of engineering, a lot of testing, a lot of complexity during manufacturing.
Sixth, all of this requires an army of highly trained engineers and technicians gathered under dozens of companies with specialized knowhow who all put together their knowledge to make something that can reliably fly.
There’s probably many more reasons.
[https://www.youtube.com/watch?v=o0fG_lnVhHw&t=1697s&ab_channel=SmarterEveryDay](https://www.youtube.com/watch?v=o0fG_lnVhHw&t=1697s&ab_channel=SmarterEveryDay)
This video shows one small part of what it takes to make a rocket.
Btw., all of this assumes you want your rocket to do something useful in space. If you just want to send come fireworks above the atmosphere, that’s not all that difficult or expensive in the 21st century.
If you just want to go 100 Km up and nothing more, it isn’t that expensive. Its been done at least once by amateurs. If you want to do this expect to spend ~$100,000 and a few years.
If you are in the US, you will need approval from the FAA to launch your rocket. In order to do that you will have to convince them the odds of hurting someone is quite low. In practice this means you need a very large area with no people in it. This has been done by launching in the Black Rock dessert, and paying CSX freight not to run any trains across the dessert during your launch window. That is not inexpensive.
Most of the expensive rockets you see going up are going, at least initially, into low earth orbit. This is hard mostly because you need to be going about 8 km per second to avoid falling back down. It’s much easier to build a rocket that just goes straight up to the same height, at least around 300 km, and then falls back to earth. That requires roughly **20 times less** energy for the same payload weight but you’re only outside the atmosphere for a few minutes.
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