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Space Elevator

(neal.fun)
1773 points kaonwarb | 2 comments | | HN request time: 0s | source
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jvanderbot ◴[] No.45643427[source]
Very cool. One thing I wish was better shown: space is close, it's just hard to go up. Our liveable breathable atmosphere is razor thin compared to the size of earth.

In most cases, 100km is less than the distance between sizeable metropolitan areas. It's a day long bike ride. Air runs out less than a bus ride across town. A 15k jog/hike would put you in the stratosphere. Those jet aircraft that seem so high are closer than that. Closer than your friends house or the local stadium probably.

Look at a map or globe with that in mind and everything feels so thin!

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messe ◴[] No.45643658[source]
> it's just hard to go up

Going up is the comparatively easy part, it's not exactly rocket science. Going fast enough sideways so you stay up there is the tricky bit.

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block_dagger ◴[] No.45646224[source]
It's NOT rocket science?
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Retric ◴[] No.45646256{3}[source]
You can reach space using air breathing jets. You can’t stay in space using air breathing jets.
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CobrastanJorji ◴[] No.45646750{4}[source]
I don't think there are any physics reasons why it'd be impossible, but certainly we can't do it with existing technology. You'd need an air breathing jet that could get a vehicle to go about five or six times faster than any current such engine has ever achieved (i.e. around mach 20-30), which is perhaps ridiculous, but I don't think it's necessarily impossible, just something we don't know how to do. There have been some (failed) efforts to get there, like the X-30.
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Retric ◴[] No.45647727{5}[source]
Basically when you cut thrust you must pass through that altitude again or escape orbit.

So either fire a rocket in space to circularize the orbit or reach more than Earth’s escape velocity 25,020 mph (11.186 km/s, 40,270 km/h) ~ Mach 32.6, due to some drag in air to thin for any kind of air breathing engine to work.

X-30 was aiming far lower ~Mach 20. Nuclear could make it more realistic than any form of chemical combustion. It might be physically possible using Hydrogen but you’re talking generating extreme thrust at vastly more extreme conditions than the space shuttle’s retry.

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1. LorenPechtel ◴[] No.45652448{6}[source]
Or go high enough to let the moon alter your orbit into one that doesn't hit the atmosphere.
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2. Retric ◴[] No.45656568[source]
Yea thus ‘Basically’ you can also escape earth’s orbit slightly more easily using the sun. However, none of this really helps much you’re still looking at more than escape velocity in atmosphere with a purely air breathing engine due to drag.