Due to it's height and proximity to the equator, Mount Kenya has become a go-to in regards to African space elevators, but I'm wondering if another location within the Aberdare Range would be more accessible option. What do you all think?

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    $\begingroup$ I'm on the fence as to whether this is a duplicate of this question or not. On the one hand, none of the answers to it mention Kenya, but on the other hand, most of them list a number of criteria with which you could determine for yourself which is the better option. It's definitely closely related and will likely come in handy to you. $\endgroup$ – F1Krazy Oct 7 '19 at 15:19
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    $\begingroup$ @F1Krazy OP isn't asking about optimal location based on physics though, unless I'm misunderstanding the question he's asking about economics, which isn't really addressed in the other thread at all. $\endgroup$ – Morris The Cat Oct 7 '19 at 15:24

Mount Kingangop is much closer to Nairobi, and if you did the bulk of the construction on the west side of the mountain, it would also be much easier to minimize the ecological impact, since the eastern side of the Aberdares is all rainforest and generates a lot of Kenya's ecotourism. That's unlikely to stop being a Big Deal to Kenya even in a future setting. Both mountains are as close to being 'right on the equator' as you could want realistically.

Something you'd want to think about in either case is that this is not a tectonically stable part of the world. The Aberdares are part of the Great Rift Valley and Mt Kenya is an extinct volcano. Earthquakes are a hazard in either case.

Another issue of concern is that Mount Kenya provides most of the country's water, so massive construction in that area would have some potential concerns there as well.


Honestly, considering that the elevator already is just under 36 000 km long, the few extra kilometers you save by building on top of a mountain doesn't really matter one way or another. So I would advise anchoring it wherever it's easiest to build the ground infrastructure and best transport links to the base of the elevator. Neither of which are likely to be the case in the mountain ranges at all.

The elevator is nothing like a freestanding tower, it's a hanging structure that hangs from the geostationary orbit downwards. The anchor point on the ground does not take up any significant structural load off the elevator, so the question you're asking really is just whether you dangle down a 35,786 km elevator cable/structure (down to sea level) or a 35,781 km elevator cable/structure (down to Mt Kenya). The difference in engineering effort between those two scenarios for the elevator itself is practically a rounding error.

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    $\begingroup$ Well, the height isn't the most critical factor, but you DO want to anchor it to some very, VERY solid bedrock, and if you want very large, very solid chunks of solid bedrock to anchor something to, those are usually mountains. It's a good point though that it's not actually a PEAK you want, per se, but a mountainous plateau that would have the best combination of factors, now that I'm thinking about it. $\endgroup$ – Morris The Cat Oct 7 '19 at 16:15
  • $\begingroup$ Those 5 km are critical, not because they shave significant length off the tether, but because they drastically decrease the amount of atmosphere the elevator cars will need to travel through. Atmospheric drag is a major source of power consumption, and traveling below weather will also require a durable shell around the car, which adds mass. This extra mass can only be jettisoned when the car rises above the cloud layer. And remember, the lowest stretch of the cable will need to be insulated against weather, too. All in all, bypassing those first few km amounts to huge cost reductions. $\endgroup$ – Gilad M Nov 8 '19 at 12:19
  • $\begingroup$ @GiladM surely a space elevator car isn't particularly mass limited though? and power is easily dealt with by going slower? its not like we have to battle the rocket equation here $\endgroup$ – jk. Nov 8 '19 at 13:21
  • $\begingroup$ Well, yes and no. Your cable has to hold up the mass of the car as well as its own mass, so if the car is heavier, the cable has to be stronger - that is, wider - and the cable's width has to taper exponentially to support itself. So we're still battling exponential mass dependence by a different name. As for moving slowly, keep in mind the expense of building and maintaining a space elevator. You're going to want goods to go up as quickly as possible to capitalize on its period of operation. If the cars go twice as fast, you can send up twice as many over the elevator's lifetime. $\endgroup$ – Gilad M Nov 8 '19 at 18:47
  • $\begingroup$ @GiladM You don't have to go slow the whole way, just the few kilometers of thick atmosphere. Pretty much all designs have cars that climb the cable, rather than is pulled by it, so they aren't restricted to all be moving at the same rate, they can accelerate and decelerate as they move. $\endgroup$ – tylisirn Nov 9 '19 at 13:18

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