h a l f b a k e r yNot so much a thought experiment as a single neuron misfire.
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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.
Lifters
Stupidly_20high-altitude_20drone
[bs0u0155, Nov 13 2018]
Provisonal flight path : catteries coincidence
https://drive.googl...o5WgHtQQ4XqgBRWpABc
[not_morrison_rm, Nov 14 2018]
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Annotation:
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// Hmm, so you start doubling up on the string thickness.// |
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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. |
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Hmmm, the problem might be ionic drives only work
within the atmosphere, and the higher you go -> the
thinner the atmosphere. |
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The easy solution would be BYO atmosphere. No one's
going to miss a few cubic miles of nitrogen. Or get
hydrogen balloon(s) |
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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. |
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//ionic drives only work within the atmosphere, and the
higher you go -> the thinner the atmosphere. // |
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That's why I'm only using them for the first 30 km where's
there's at least a bit of atmosphere. |
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^Good thinking that entity... |
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According to the internet (so it must be true) in (10-
1 kg/m3) |
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At 0 metres* above sea level -> 12.25 numpty nunpt.
At 30,000 metres above sea level -> 0.1841 numpty
numpt. |
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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. |
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It can probably work, but the leccy bill is a going to
be painful. |
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* Do they employ some berk to lie on the ground
with the altimeter?" |
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Bugger, forgot what I was going to say...it's me age |
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//66-fold drop in lifting, or 66 times more leccy// |
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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. |
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Rockets work on conservation of momentum; so if the reaction mass is reduced, the velocity must be proportionately increased for the same thrust. |
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But why are you all obsessed with such primitive methods ? |
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//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. |
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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. |
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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). |
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No bats or eels, but we have experimented extensively with electrically-propelled flying cats. |
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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. |
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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. |
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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. |
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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. |
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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. |
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It's certainly highly suspicious that there's no evidence of a conspiracy ... |
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I'd wager that "eel" is mentioned WAY less than average in
all NASA documentation. I think that says a lot. |
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Only if your average excludes X-15 pilots. |
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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. |
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//But why are you all obsessed with such primitive
methods ? |
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Because we're British, goddamit! If it isn't brass and
powered by a stoker with flat cap, it's not proper
technology. |
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I vote "Many cast iron busts of Isaac Newton being
zapped downwards by railgun" |
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//I think we can essentially consider this nut cracked// |
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//"Many cast iron busts of Isaac Newton being zapped
downwards by railgun"// |
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That's definitely the correct line of thinking. |
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Yep,and the Borg chipped in with a provisional flight
path. |
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Oddly enough, it seems to follow a path that goes over
every major cattery from the Chilton Hills to
Folkstone. |
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Just one of them things, eh? Link. |
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// a path that goes over every major cattery // |
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Even ley lines have a Dark Side ... |
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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. |
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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). |
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//Some humans claim they can find water underground// I
think we did this one. |
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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. |
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The bent wire and willow wand types aren't as reliable. |
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<walks away whistling nonchalantly> |
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In less enlightened times, you might have been worshipped as a God, or possibly burnt as a witch. |
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Probably not something you would want to take a chance with, though. |
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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. |
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I'm tempted to do the Ironic lifter Space Elevator
idea...why change the habits of a lifetime? |
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I'd tell you a time travel joke... but you didn't like it. |
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