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[Trekkin]

If you want to use a counterweight, you need to move the cable -- or at least a cable (and then we have to worry about how to couple the lift cables to the support cables.) That means the cable cannot taper, which vastly increases the cable mass that must be maintained.

An energy only counterweight (work-recovery on descenders used to at least partly boost the energy input taken to move the risers - need not even be at the same time if there's a method of storage and discharge) would be not much more of a complication from a 100% 'fed externally' system. Given everything else.

You also need a station in the middle of the cable to switch from one counterweight to the other, since both ends of the elevator are pulled away from the middle, so now there's more mass and more hassle with vibrations up and down the cable.

Any cable not missing the opportunity (and/or constructive necessity) to have a geostationary station in the 'middle', from which both ends (the long length of cable to Earth and the probably shorter length of cable tied to sufficient counterweight to keep things just taught enough and act as an 'outflinging' station, for fuel-saving interpkanetary launches out of a trapdoor) dangle is going to be set up for roping-counterweights exactly as you say (up from/down to Earth, down out/up in from orbit), regardless of whether it actually does.

Well, true, but that's regenerative braking, not a counterweight. Most of the more serious proposals I've seen for doing this use it, actuator design permitting, to save on beamed power in the outbound case and broaden the set of permissible weather conditions in the inbound case, as most of them use beamed power to avoid having to run power down the cables.

Regarding stations on the cable: space elevators are not static structures. The lower terminus has to dodge storms, the upper terminus needs to handle orbital correction, and everything in between needs to be moved out of the way of space debris and satellites -- and that's just to keep the cable intact. If you want to stick a permanent crawler in the middle of that and absorb the additional complexity and expense of transiting things from one end of it to the other, that station is going to have to move with all of that, which does not bode well for keeping constant tension on the lift cables.

Re: Expanding our population

There is no need to. Labor can be done by robots, which don't require much living space. Scientific research could be done by augmented humans collaborating with intelligent AIs. There is no practical need to expand our population on Earth. Other planets? Maybe. But not Earth.

That's quite a claim, seeing as we have no such AI, no such augmentations, and significant gaps in what robots can do.

[WillowLuman]

Re: Expanding our population

There is no need to. Labor can be done by robots, which don't require much living space. Scientific research could be done by augmented humans collaborating with intelligent AIs. There is no practical need to expand our population on Earth. Other planets? Maybe. But not Earth.

Aye, it's less about numbers for numbers sake and more about becoming established in more than one place in the universe, so as to avoid extinction should something happen to one habitat.

[KittyTac]

Re: Expanding our population

There is no need to. Labor can be done by robots, which don't require much living space. Scientific research could be done by augmented humans collaborating with intelligent AIs. There is no practical need to expand our population on Earth. Other planets? Maybe. But not Earth.

That's quite a claim, seeing as we have no such AI, no such augmentations, and significant gaps in what robots can do.

But considering the rate of technological progress, I bet we will have most or all of those by the year 2150 or a bit later.

[Trekkin]

Re: Expanding our population

There is no need to. Labor can be done by robots, which don't require much living space. Scientific research could be done by augmented humans collaborating with intelligent AIs. There is no practical need to expand our population on Earth. Other planets? Maybe. But not Earth.

That's quite a claim, seeing as we have no such AI, no such augmentations, and significant gaps in what robots can do.

But considering the rate of technological progress, I bet we will have most or all of those by the year 2150 or a bit later.

Defending arbitrary assumptions by pulling numbers out of your ass doesn't make them more realistic. I really don't care what some layman "bets" other people will build for him, let alone by when.

Also, "the rate of technological progress"? Since when is that a meaningful concept, let alone a uniform rate?

[KittyTac]

Re: Expanding our population

There is no need to. Labor can be done by robots, which don't require much living space. Scientific research could be done by augmented humans collaborating with intelligent AIs. There is no practical need to expand our population on Earth. Other planets? Maybe. But not Earth.

That's quite a claim, seeing as we have no such AI, no such augmentations, and significant gaps in what robots can do.

But considering the rate of technological progress, I bet we will have most or all of those by the year 2150 or a bit later.

Defending arbitrary assumptions by pulling numbers out of your ass doesn't make them more realistic. I really don't care what some layman "bets" other people will build for him, let alone by when.

I was not talking about the present. It is quite obvious that we do not have any of that.

[Trekkin]

Re: Expanding our population

There is no need to. Labor can be done by robots, which don't require much living space. Scientific research could be done by augmented humans collaborating with intelligent AIs. There is no practical need to expand our population on Earth. Other planets? Maybe. But not Earth.

That's quite a claim, seeing as we have no such AI, no such augmentations, and significant gaps in what robots can do.

But considering the rate of technological progress, I bet we will have most or all of those by the year 2150 or a bit later.

Defending arbitrary assumptions by pulling numbers out of your ass doesn't make them more realistic. I really don't care what some layman "bets" other people will build for him, let alone by when.

I was not talking about the present. It is quite obvious that we do not have any of that.

Yes. It is equally obvious that you have provided no real justification to expect any of them, let alone all of them, by any specific date.

[WillowLuman]

Aight, let's take a moment and rethink and calm down. I sense an argument of the bad kind.

[Starver]

Regarding stations on the cable: space elevators are not static structures. The lower terminus has to dodge storms, the upper terminus needs to handle orbital correction, and everything in between needs to be moved out of the way of space debris and satellites -- and that's just to keep the cable intact. If you want to stick a permanent crawler in the middle of that and absorb the additional complexity and expense of transiting things from one end of it to the other, that station is going to have to move with all of that, which does not bode well for keeping constant tension on the lift cables.

Most plans (such as they are, still so speculative and requiring Handwavium production to get further) assume a bedrock-anchored base and engineering a way to resist any likely equatorial weather events. Those that don't may employ an oil-rig-like bottom-end (on land, I've seen Inverted World-like railtrack-crawlers, overlaid upon the suitably prepared terrain) to give 'wiggle', but it's a near glacial movement compared with the 'ideal' movement of hundreds of miles, to skirt to one side of a storm's predicted path, within a handful of days, of something likely much more massive than the loaded STS Crawler. For the bottom end, 'dodge' is an optimistic description of what could be done.

At the middle and top end, though, you can thrust the inverted-pendulum sideways (or 'bow' it by pushing on the middle and letting it flex) to avoid (known!) fly-by threats that might be more proximate than there is comfort for. Relatively quick reactions (apply some lateral thrust, perhaps even by applying electrodynamic potential against the Earth's magnetic field) compared with the low-end, but don't forget how fast (unpredicted) space-debris can hove into view.

Still, with all that, the tension is unlikely to change quite that much. Off-centering the ground 'anchor' and oppositely off-centering the far counter-weight terminus (the whole tethered structure crossing over the 'ideal' vertical) is likely to be the greatest over-stress, and on a 36Mm (to GEO) plus an additional fraction of that (to counterweight) the total angle of deflection from 'normal' is unlikely to be that great, with (non-linear, but nearly so) proportionate increase in tension_max across the structure surely being not beyond the in-built safety factor (which should probably already be calculated upon this most extreme of 'normal' operations the dodging north below to avoid a storm, whilst dodging 'south' above to avoid a NEO).


We also should probably do a lot of cleaning up of the current/near-future cloud of orbital debris, too, in laying the 'groundwork' for our tether. Everything up there is equator-crossing and, if not in the current orbit then almost all inevitably in a future one if it's stable enough, will cross any reasonable safety-zone presently imaginable.

(Beyond the requisite 20-Minutes-Into-The-Future already required for construction of the Beanstalk, it's anybody's guess what safety-factors, precautions and defenses will be both necessary and possible to implement.)

[Trekkin]

I mean, there's always the terrible NIAC Phase II study that assumed a series of mobile termini handing off the actual beanstalk end one to the other, or the even more terrible Analemma Tower that just asserts that the value of real estate rises forever with height and doesn't connect the bottom to the ground at all...yes, okay, point taken, the stationary termini are probably more grounded. Still, there's a lot of wobble in the cable, particularly if the crawlers cause any kind of oscillation -- and if they rise at all quickly, they will. My worry with the whole counterweight idea is that the lift cables might end up bowing the main support cable during all of this by exerting a force between the pulley and the crawler. If the cable bows and the counterweight drops, it's going to be slower to straighten out and thus lift the counterweight, is it not?

Regardless, you're right that this is all pointlessly speculative while the cable's still impossible. Then again, I like space fountains and those are almost impossible and very power-hungry.

[WillowLuman]

What about a magnetic rail launch? Perhaps a bit too G-strenuous for humans but still cheaper than rockets.

[Trekkin]

What about a magnetic rail launch? Perhaps a bit too G-strenuous for humans but still cheaper than rockets.

There are versions that can launch humans, but they need the end of the launch tube magnetically levitated out of most of the atmosphere at which point we're back to space fountains.

I wonder if the more achievable cargo-only versions aren't self-obsoleting though. At some point we presumably want to stop sending acceleration-tolerant bulk cargo like water into space and start getting it from space, and unlike a fountain/elevator the rail launcher can't help with deorbiting and reentry. The geometric constraints on cargo size are a worry as well.

[LordBaal]

Thanks Hugo, things were heating up and I don't see why, thought we were just trowing arguments for the sake of fun, not defending points of view with fanaticism, specially over highly hypothetical things.

[WillowLuman]

Just keep it chill y'all.

[Egan_BW]

What if they don't appreciate life beyond theirs? What if they don't recognize us as life by other kind of values or even by methodology? What if they don't care? Technological progression doesn't mean they can be "mean spirited" or simply don't care. Or worst what if they consider carbon based life/bipeds/creatures with only two eyes/whatever an affront to their Gods? Alien motivations probably could be really alien to us. They could come and kill off exactly half planet and then expect us to be grateful and join them in doing so to the next planet and bolt in horror when they see us trying to nuke their ships or something.

Because those who do not appreciate life and seek to destroy it will be at a natural disadvantage to those who value life, and seek to catalog and exploit it. Someday the civilization that hates all life that is not itself will come across a civilization with pets from a thousand different planets, and the xenophobes will get eaten by a swarm of adorable spiders. I just assume that what's most effective is what's most common, because being effective is useful to not being destroyed.

If all things that have two eyes is an affront to your gods, some day that bias will make you miss out on some advantage.

[Starver]

I mean, there's always the terrible NIAC Phase II study

I'm reading it, and my brain is melting!

Gasoline engines don’t work well in space where there is no air and wouldn’t have the required range

Overshot on the "not writing this just for technical people" ambition.

(Goes on to dismiss solar panels, then suggests using solar panels anyway, except without the 'solar'. That's me saying "without the 'solar'", the author still calls them that, potentially confusing the third-grader apparently being written for. Like with the diagram of the asteroid being mined for material, which features stick-men with picks on its surface. And what's "sulferic acid"? I'm already vitriolic about sulphur no longer officially being spelled with a "ph" since the '90s!)