Why is it so difficult and costly to build a rocket which escapes Earths atmosphere?

Question

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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Answer 1

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.