Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Space Elevator

neal.fun

Post reply on HN
Print view View original

41–50 of 414 posts

Re: Space Elevator

#41

Post by pbmonster »

Yizahi wrote: post #37
tempestn wrote: post #8

TIL it's estimated that over 48 tons of meteors hit the atmosphere every day. Regarding actual space elevators though, while they're not sci-fi to the extent of something like FTL travel - ie. they're technically not physically impossible - they're still pretty firmly in the realm of sci-fi. We don't have anything close to a cable that could sustain its own weight, let alone that of whatever is being elevated. Plus,…

The problem with space elevator is not only the lack of material today, but also the fact that such elevator is an ultimate and very fragile weapons platform, you basically get stones up the well and then drop them on the enemy. Meaning that any authoritarian country would destroy it even before it is ever built. And sturdy enough space elevator after it's break at any high point would start falling down on the plane…

I don't see it. Why worry about a weaponized space elevator when stealth bombers, cruise missiles and ICBMs exist?

If the power building the space elevator wants to bomb you, you're going to get bombed.

Re: Space Elevator

#43

Post by Cthulhu_ »

Physkal wrote: post #19
_def wrote: post #7

The atmosphere of this reminded me of the game Outer Wilds

I was really disappointed not to see a sequel. No new games from the developers since.

Its development is really interesting, in that it was more a proof of a scientific paper to start with. Anyway one of their tweets from September 2024 indicates they're working on a sequel, despite their publisher (Annapurna, owned by Megan Ellison, daughter of Larry Ellison) having had some issues around then.

Re: Space Elevator

#44

Post by arethuza »

243423443 wrote: post #25
timonoko wrote: post #16

Giant Space Bola is much more attractive. It is a 10000 km string with capsules at both ends. It rotates in sync with earth so that the speed at meeting point is the same. You just hop in and end up in space without much effort. Because it is freely floating you can move it around to avoid meteor impacts and other such shit.

Did you read Seveneves by Neal Stephenson? In the second part of the book, they use this and related technologies.

I think those technologies are mentioned throughout the book - just at a much larger scale in the second part.

Re: Space Elevator

#46

Post by adwn »

tempestn wrote: post #8

TIL it's estimated that over 48 tons of meteors hit the atmosphere every day. Regarding actual space elevators though, while they're not sci-fi to the extent of something like FTL travel - ie. they're technically not physically impossible - they're still pretty firmly in the realm of sci-fi. We don't have anything close to a cable that could sustain its own weight, let alone that of whatever is being elevated. Plus,…

Almost all discussions around space elevators focus on the cable itself, how to manufacture and deploy it, and completely forget about the issues that would arise afterwards:

1) How do you attach the climber to the cable without affecting its structural integrity? By squeezing it really hard? A material that's optimized for longitudinal tension strength is probably not very tolerant of lateral compression.

2) How do you provide power to the climber? A regular electric cable can't support its own weight, so either you have to attach it to the climbing cable, or you have to make it from the same material.

3) Is it even worth it? The climber needs to cover a distance of ~36,000 km, so even at 200 km/h it takes 7.5 days from the bottom to geosynchronous orbit. How many climbers and what payload can the cable support at the same time? Refer to issue #1 regarding limits in speed and mass per climber.

The throughput in tonnes/day is absolutely abysmal in relation to the immense upfront infrastructure cost per elevator. Compare this to SpaceX's Starship, which is getting closer and closer to fully reusable 100 tonnes to orbit in minutes. Space elevators will stay science fiction forever, not because they're infeasible, but because they're useless.

Re: Space Elevator

#47

Post by delta_p_delta_x »

iberator wrote: post #20
cyode wrote: post #14

A beautifully executed project here, I bought Neal a coffee. What evolutionary advantage, I wonder, is there to Ruppell's griffon vulture flying at 11400 meters? edit: units

Feets are actually just fine in anything related to aviation.

> Feets are actually just fine

Non-SI legacy units have been grandfathered in and 'accepted for common use', but ICAO recommends that SI units should be used[1] (eventually). China and quite the majority of the ex-USSR, for instance, use metre flight levels[2].

There have been at least two aviation accidents and incidents relating to unit mis-conversions. This is two too many. As an SI absolutist, everyone should switch to SI or units purely derived from SI (so domain-specific stuff like parsecs, electronvolts, and binary prefixes, if appropriately symbolled are OK). It is an internationally-recognised, and nearly universal standard that permeates every aspect of human lives.

[1]: https://aerosavvy.com/wp-content/uploads/2014/08/an05_cons.p...

[2]: https://en.wikipedia.org/wiki/Flight_level#People's_Republic...

Re: Space Elevator

#48

Post by ta1243 »

What's really interesting is that a space elevator goes to Geostationary orbit by necessity. Getting to 100km vertically doesn't save as much as you might think when it comes to getting into orbit.

To get into a very low earth orbit from an equatorial launch pad at sea level you need about 9.2km/s of Delta-V

To get there from a 100km tall tower, you need about 8km/s of delta-V - about 85%.

Think about how much scrolling there was to get to 100km.

To get to the ISS you'd need to scroll 4 times further. Starlink and Hubble are another 100km beyond that.

You start having radiation problems if you spend too much time above 600km.

Aside from Apollo, the highest a human has been is about 1400km - 14 times more scrolling than this page.

To get to GEO would require scrolling over 25 times further than even that.

Post reply on HN