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# Ionic lifter Space Elevator

Use high-voltage ion wind to hold up your space rope
 (+2) [vote for, against]

The space elevator is a veritable Sci-Fi wet dream. The basic principle revolves around a satellite that doesn't revolve around. That is, you put a satellite not-quite in geostationary orbit and tie it to the Earth with a 36,000 km bit of string.

Now, once you've built this, you can merrily send things too and from Earth orbit with much less fuss than the rampant price gougers over at Baikonur. The tricky part of this system is getting a very strong string.

That really nice stuff you use for the parcels you care about, that gets you about 6 km before it breaks under its own weight. This is no good, so move to nylon, this only gets you about 28 km and that's with no cargo hanging off it or any side loads etc. Hmm, so you start doubling up on the string thickness. Some basic calculations suggest that by the time you get to the geostationary satellite you need 1518 fold thicker string just to hold up all the string. Again that is before any cargo or vehicle acceleration is added. It's actually not as bad as that, Gravity tends to drop off after a 1000km or so and that gets you a real boost, the string needs to be thickest at about 11,000 km out at something like 81-fold thicker than the base. So here's a partial solution.

Inspired by the ionic lifters mentioned in <link> I wondered what would happen if we held up the bottom of the space elevator with ion thrust? Imagine a constant source of uninterrupted power were available and this could be transmitted up the elevator cable to strategically placed ion thrusters. These could be controlled to damp oscillations and add extra force when cargo is moving up and down, most importantly however they could give the lower portion of the elevator a 0 effective weight. This saving can be subtracted from the necessary strength of cable above, which makes it lighter, making the cable above that lighter... exciting right?

So, instead of peak cable thickness being 81 fold thicker than base... I ran the numbers on a space elevator being held up by thrusters to about 30 km and its peak thickness is 80.49 fold thicker than base! A huge saving. I think we can essentially consider this nut cracked.

 — bs0u0155, Nov 13 2018

Lifters Stupidly_20high-altitude_20drone
[bs0u0155, Nov 13 2018]

Provisonal flight path : catteries coincidence https://drive.googl...o5WgHtQQ4XqgBRWpABc
[not_morrison_rm, Nov 14 2018]

 // Hmm, so you start doubling up on the string thickness.//

Uh, hold on just a millisecond. If you double up the string, you also double the weight of the string. So that can't be right.
 — MaxwellBuchanan, Nov 13 2018

 Hmmm, the problem might be ionic drives only work within the atmosphere, and the higher you go -> the thinner the atmosphere.

The easy solution would be BYO atmosphere. No one's going to miss a few cubic miles of nitrogen. Or get hydrogen balloon(s)
 — not_morrison_rm, Nov 13 2018

Depends on what sort of ionic thruster [bs] means. True ion thrusters are intended for use in a vacuum, but require a source of reaction mass.
 — MaxwellBuchanan, Nov 13 2018

 //ionic drives only work within the atmosphere, and the higher you go -> the thinner the atmosphere. //

That's why I'm only using them for the first 30 km where's there's at least a bit of atmosphere.
 — bs0u0155, Nov 13 2018

 ^Good thinking that entity...

 According to the internet (so it must be true) in (10- 1 kg/m3)

 At 0 metres* above sea level -> 12.25 numpty nunpt. At 30,000 metres above sea level -> 0.1841 numpty numpt.

 Which looks to me like a 66-fold drop in lifting, or 66 times more leccy to get the same "not falling out of the sky" experience.

 It can probably work, but the leccy bill is a going to be painful.

 * Do they employ some berk to lie on the ground with the altimeter?"

Bugger, forgot what I was going to say...it's me age
 — not_morrison_rm, Nov 13 2018

 //66-fold drop in lifting, or 66 times more leccy//

 Not necessarily. Why assume that lift is proportional to air density? There will be fewer molecules, and fewer molecules to entrain in ion stream, but those entrained molecules will likely be accelerated more.

I think.
 — MaxwellBuchanan, Nov 13 2018

 Rockets work on conservation of momentum; so if the reaction mass is reduced, the velocity must be proportionately increased for the same thrust.

But why are you all obsessed with such primitive methods ?
 — 8th of 7, Nov 13 2018

 //velocity must be proportionately increased// which can be straightforwardly accomplished by using a higher voltage to accelerate the ions. Current will depend on the number of ions, and will hence be proportionately reduced.

Howevertheless, a simpler way to accomplish the same thing would be to start by digging a 30km hole. Let the space- tether dangle down into it, then jam a scaffolding pole through the tether and prop it across the top of the hole. Hey presto, 30km of tether fully supported.
 — MaxwellBuchanan, Nov 13 2018

Incidentally, given that some animals are capable of generating a good few hundred volts (think electric eels), it's rather surprising that evolution hasn't yet given us an ionically-thrusted bat (or flying eel).
 — MaxwellBuchanan, Nov 13 2018

 No bats or eels, but we have experimented extensively with electrically-propelled flying cats.

The results are inconclusive, so testing continues whenever we can catch a fresh one, as so far it's turned out to be a single-use process.
 — 8th of 7, Nov 13 2018

Come to think of it, has anyone had a good look around the 30km level? I remember there was a lot of mystery about where eels go to breed.
 — MaxwellBuchanan, Nov 13 2018

 Ask NASA; the X-15 got up to those sorts of altitudes. We don't recall any mention of piscine life in the mission debriefs.

We'll have a look next time we're passing. It might be a seasonal thing, of course, like salmon runs and monarch butterfly migrations.
 — 8th of 7, Nov 13 2018

Yes, but if you comb through all the X-15 debriefs - and I do mean *all* of them - you will not find one single moment where the pilot says "there were no eels at 30k". I don't know about you, [8th], but I for one find that omission rather striking.
 — MaxwellBuchanan, Nov 13 2018

It's certainly highly suspicious that there's no evidence of a conspiracy ...
 — 8th of 7, Nov 13 2018

I'd wager that "eel" is mentioned WAY less than average in all NASA documentation. I think that says a lot.
 — bs0u0155, Nov 13 2018

Only if your average excludes X-15 pilots.
 — MaxwellBuchanan, Nov 14 2018

Wind beyond atmosphere? ... and maybe that can be done with a laser and a particle beam? The laser could heat up the air to make it less dense, creating a vacuum tunnel for particles.
 — Inyuki, Nov 14 2018

 //But why are you all obsessed with such primitive methods ?

 Because we're British, goddamit! If it isn't brass and powered by a stoker with flat cap, it's not proper technology.

I vote "Many cast iron busts of Isaac Newton being zapped downwards by railgun"
 — not_morrison_rm, Nov 14 2018

 //I think we can essentially consider this nut cracked//

[marked-for-tagline]
 — 2 fries shy of a happy meal, Nov 14 2018

 //"Many cast iron busts of Isaac Newton being zapped downwards by railgun"//

That's definitely the correct line of thinking.
 — bs0u0155, Nov 14 2018

 Yep,and the Borg chipped in with a provisional flight path.

 Oddly enough, it seems to follow a path that goes over every major cattery from the Chilton Hills to Folkstone.

Just one of them things, eh? Link.
 — not_morrison_rm, Nov 14 2018

 // a path that goes over every major cattery //

 Even ley lines have a Dark Side ...

 Some humans claim they can find water underground by the use of lengths of wire bent at a right-angle and then held out at forearm's-length over the area being searched.

We can definitely find cats above ground by the use of lengths of wire bent at a right-angle and held out at forearm's-length, then poked hard into shrubbery (just listen for the yowling).
 — 8th of 7, Nov 14 2018

//Some humans claim they can find water underground// I think we did this one.
 — MaxwellBuchanan, Nov 15 2018

 The succesful ones generally use a portable drilling tower and lots of lengths of steel pipe, after a survey using small explosive charges and arrays of geophones.

The bent wire and willow wand types aren't as reliable.
 — 8th of 7, Nov 15 2018

<walks away whistling nonchalantly>
 — 2 fries shy of a happy meal, Nov 15 2018

I can find water underground. I mystically look for those little metal covers in the pavement outside that have a W on them.
 — Ian Tindale, Nov 15 2018

 In less enlightened times, you might have been worshipped as a God, or possibly burnt as a witch.

 Probably not something you would want to take a chance with, though.

It might be wise to keep your Special Power a secret. It's unlikely you'd fit in as one of the X-men; skin-tight lycra doesn't suit you. Actually, there aren't many people it does suit, apart from Seven of Nine.
 — 8th of 7, Nov 15 2018

I'm tempted to do the Ironic lifter Space Elevator idea...why change the habits of a lifetime?
 — not_morrison_rm, Nov 15 2018

I'd tell you a time travel joke... but you didn't like it.
 — 2 fries shy of a happy meal, Nov 16 2018

 //has anyone had a good look around the 30km level?//

I'm not sure they need to. Various things keep falling out of the sky including birds, fish, frogs etc. These are clearly falling off the back of a space elevator. Weirdly, it's a female cult that's been dealing with aliens for millennia. In many ancient carvings there are depictions of humans meeting with aliens, and they are all carrying handbags. Since handbags are now commonplace, cult members now make up their faces to be shinier like their alien friends and wear the symbolic high (h)eels.
 — bigsleep, Nov 16 2018

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