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Space Elevator

(neal.fun)
1773 points kaonwarb | 3 comments | 20 Oct 25 04:42 UTC | HN request time: 0.003s | source
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jvanderbot ◴[20 Oct 25 13:03 UTC] 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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hinkley ◴[20 Oct 25 19:36 UTC] No.45648223[source]▶
In a parallel universe where Africa is covered by world powers, Mount Kilimanjaro would make a pretty good launch facility. Reduced rocket equation needs for being nearly 3 miles high. If you start in thinner atmosphere you need less fuel to punch through it. You’re also higher when you hit Max Q.

This is essentially what Scaled Composites and Virgin Galactic were trying to do with their cargo plane system, only you don’t have to worry about the ignition timing because you’re not in free fall.

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rozab ◴[20 Oct 25 19:51 UTC] No.45648416[source]▶
The most important feature of a launch site is having no populated areas downrange. Kilimanjaro would have Mombasa downrange.

I don't know of any launch sites significantly above sea-level, the marginal performance increase wouldn't be worth the logistical nightmare. It's easier to fly up a 747 than build a launch facility on top of a mountain.

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1. blueflow ◴[20 Oct 25 20:28 UTC] No.45648874[source]▶
> The most important feature of a launch site is having no populated areas downrange. Kilimanjaro would have Mombasa downrange.

This was part of the Plot of Halo: ODST, where fragments of the space elevator collapsed onto New Mombasa.

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2. hinkley ◴[20 Oct 25 21:28 UTC] No.45649604[source]▶
The description of a space elevator falling is rendered in horrific detail in Kim Stanley Robinson’s Mars trilogy.

Twice.

Because the only known material strong enough at the time was diamond, and diamond doesn’t ablate much when falling through atmosphere.

One of the early space elevator research companies specifically designed a cable that was made by stacking successive layers of material both to slowly increase carrying capacity by building the tether in iterative layers, and hoping it would ablate or at least reach a quick terminal velocity in the case of catastrophic failure.

It is undoubtedly the case that the senior staff on that project were familiar with the Mars trilogy.

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3. BizarroLand ◴[22 Oct 25 19:12 UTC] No.45673762[source]▶
I've often wondered if we could decrease the difficulty of a space elevator by a good bit by integrating magnetic levitation.

The base would need to be enormous and I'm sure the power draw would be insane, but being able to break the elevator cable into smaller lines and take the weight off of any individual strand might make it a touch more plausible without currently non-existent technologies.