A Lunar Space Elevator Could Be Built for $2B [pdf] | Hacker News Reader

A Lunar Space Elevator Could Be Built for $2B [pdf]

hou.usra.edu

From the paper, line 1:

> THE LUNAR SPACE ELEVATOR, A NEAR TERM MEANS TO REDUCE COST OF LUANR ACESS

Does instill confidence. Further recommended literature: can we space elevator? should we space elevator? https://www.youtube.com/watch?v=Z5aHMB4Tje4

somebody set up us the bomb

All your base

are belong to us

What you say!

At least we know humans wrote the paper. AI wouldn’t make such trivial mistakes.

The first drum computer with "real" drum sounds was the LinnDrum (OK, the LM-1 was earlier but it was short-lived and far too expensive). Could it replace human drummers? Well, when it was launched in the 80's I read about it in a magazine where the need for a "RHS" button (which supposedly stands for "real human shitty" or something similar) which introduces slight deviations from the mechanical precision which is inherent to digital machinery. Drum machines are simply too precise, they never miss the mark, always are exactly in time and with that lack "character". See that button as the opposite of a "quantise" function, something to introduce "character".

Nothing is keeping anyone from introducing a "RHS" switch for generative AI. Tune it to the way your favourite editor or writer messes up things and voilà, a paper written by a very non-human generative model which fools the reader into thinking it was written by one to whom errare humanum est comes natural.

The dial is called "swing" on modern drum machines, the LM-1 has "shuffle" but it is essentially the same thing: https://www.attackmagazine.com/technique/passing-notes/daw-d...

All caps disables spell check in Word as it might be an acronym. Best practice is to actually type normally then apply formatting later. Can display/print in all-caps using font formatting (font options "all caps").

I like to use Draft view for drafting (funnily enough) with formatting disabled ("use draft font in draft and outline views")

Terrestrial space elevators are unfeasible with known materials. A lunar elevator works with Kevlar. (No claims made for the validity of the article’s $2bn figure.)

You'd still need to climb the tether. How will you do that, with what kind of energy source? Rocket motors?

Solar cells, either on the ‘car’ riding up the tether or on the ground or in orbit, either beaming up/down power or with a ‘third rail’ on the tether.

> How will you do that, with what kind of energy source? Rocket motors?

The idea of an elevator is you only have to go up. With a rocket, you have to go both up and over.

Rockets would work. Solar power would be better—the 2 kW array (~100 sq ft) needed [1]is more than doable; you could use a smaller panel with batteries, too. Surface nuclear of the kind we’re already developing [2] might also make sense, though now you need lasers.

[1] https://www.niac.usra.edu/files/studies/final_report/1032Pea...

[2] https://www.space.com/nasa-moon-nuclear-reactor-project-firs...

Space cable car? It is only a marginal increase in costs to pull a second cable.

Microwave ion beam from the array of solar panels.

Isaac Arthur not being linked in any Futurology thread may be a criminal disservice in its own way, he is too valuable a light to not share with others.

He is the XKCD of all things in the Future.

Space Elevators & Orbital Tethers : https://www.youtube.com/watch?v=dc8_AuzeYKE

Lunar Space Elevators : https://www.youtube.com/watch?v=0g4TZbG2WsU

Could park a starship at Earth-Moon L1 and extend a cable toward the Moon which in between L1 and the Moon would pull itself down under its own weight. Starship would need to position itself on the Earth side of L1 to maintain center of mass of the Starship-cable system at L1. Once the cable reaches the lunar surface it can be anchored.

Not sure why it took 2 days for the penny to drop but obviously given a sufficiently strong cable can repeat this on the Earth-L1 side and end up with an Earth-Moon tether. Would be interesting to find out how close to earth a currently available cable + payload mass would reach before it breaks. The delta-v between LEO and the lower end of the tether should be small and an elliptical orbit should be able to rendezvous with it.

This URL (https://www.hou.usra.edu/meetings/newviews2018/pdf/6016.pdf) only shows a single page for me. Full paper at https://www.opsjournal.org/DocumentLibrary/Uploads/The_Lunar.... Skimming it, I can’t find how they arrive at that $2B number

Reference 5 is https://arxiv.org/abs/1609.00709

They are proposing a tether that’s about 300,000 km long and 48,000 kg mass, so 0.16g/m

Which seems very small.

Density is about the same as water, so the diameter is about 0.12mm which (for fishing line) has a breaking strain of about 10N. UHMWPE’s strength is about 6 GPa, so (0.00012)^2 * 6e9 is about 100N.

Hmm.

I seem to recall a space elevator's tether is extremely nonuniform. Eg- it might need to be 100meter diameter at ground level and barely more substantial than aether 3/4ths the way up, then expand out more.

It’s not a tower, so it’s the other way around. At ground level, the cable only has to hold up the weight of a car. At a kilometer of height, it has to hold up that car plus a kilometer of tether.

At (about; adding cars to the tether changes things a bit) geostationary height (in this case I guess that could be called lunastationary), forces on the tether start going upwards, and tether size can go down as you go further up.

See https://en.wikipedia.org/wiki/Space_elevator#Cable

Presently we can't even land a cat on the moon. The new US plan to get to the moon can only be described as fantastical.

It's pretty clear that a combination of the cold war ending, neoliberal brainrot and pollution has diminished our capacity below what is required for serious space enterprise.

The problem is that Serious Space Enterprise is very costly, ongoing, relative to the actual return on the operation. Not the invention of the tech to get you there. We've probably made most of what we'll get. In the sense of, "If there were a gold brick on Mars, would it make sense from the cost of the energy required to move the brick from Mars to some orbit and down to the surface of the Earth, versus the comparative energy required to go out, dig for, and refine the same quantity of the gold from the place we're just standing on right now?" manner, to be more specific.

Once you start thinking in that fashion, you can start asking yourself, "Exactly what object or material do I want to bring back from Mars, and could I do it more cheaply in, say, Minnesota?" Like in the way that once lab-made diamonds which are identical to mined diamonds and become cheaper, the mining is going to slow down unless the process is encumbered by tariffs, regulation, artificial constraints to preserve a business are imposed.

Echoes of PKD.

Reply on news.ycombinator.com