
Cable to the Stars – The Skyhook [video] - doppp
https://www.youtube.com/watch?v=dqwpQarrDwk
======
baby
kurzgesagt is my favorite youtube channel and I really wish we had more
channels like this so that people wouldn’t replace TV with youtube so easily.

I think education is the most important thing and for this reason kurzgesagt
is the only thing I’m donating to every single month.

If you too think education is the best way to make the world a better place
consider buying their super cool 2020 calendar or subscribing to donate
monthly:
[https://www.patreon.com/Kurzgesagt](https://www.patreon.com/Kurzgesagt)

I highly recommend watching pretty much all of their videos!

------
Richard_East
More info:
[https://en.wikipedia.org/wiki/Skyhook_(structure)](https://en.wikipedia.org/wiki/Skyhook_\(structure\))

Isaac Arthur:
[https://www.youtube.com/watch?v=TlpFzn_Y-F0](https://www.youtube.com/watch?v=TlpFzn_Y-F0)

~~~
ur-whale
Is it just me or the narrator has the same weird accent as the character Barry
Kripke in the Big Bang Theory tv show ?

------
luc4sdreyer
From the show notes[1]:

> It’s also interesting that certain designs, such as the one proposed by
> Moravec (1977), consider a tether whose rotation is chosen such that its
> instantaneous velocity when touching the atmosphere is minimized, and
> effectively zero at the tip during the moment of maximum extension into the
> atmosphere.

[1] [https://sites.google.com/view/sources-
skyhooks/](https://sites.google.com/view/sources-skyhooks/)

------
sandworm101
There is no free lunch. To be useful, skyhooks need to be much much heavier
than the stuff they throw around. Getting them up there, and servicing them,
is something beyond anything. Think of every launch ever in the history of
space. That, to biuld skyhook A.

~~~
wolfram74
Additionally, this one of the first times I've seen a description of the
skyhook that brings up what I've always been wondering about: Conservation of
momentum. Admittedly, since a skyhook would already be in orbit, it can use
much more efficient ion/plasma engines, but it will still need to re-boost
periodically. Especially since for a long time earth is going to be a net-mass
exporter.

~~~
anotheryou
Just send some stones from where you send your cargo in exchange than. Just
the payload of what rockets carry today is really not that much.

------
theothermkn
I think what bothers me most about this kind of paid fluff is that it fools
the viewer into thinking they've learned something worthwhile, when they've
only seen something pleasant. Another poster linked to a brief Wikipedia
article, and even it mentioned that the technology is nowhere near ready,
citing erosion by atomic oxygen as one concern.

What we have here is a glossed-up version of the simple observations that
spinning things spin, and "rolling" things move faster at the top than at the
bottom. The rest has been left as an exercise for the reader's active and
uninformed imagination. Don't fall for it.

FWIW, my guess is that exactly 0 tethers as described in the video will ever
play an important role in getting humans into space, for various reasons of
various veracity. But it's all guesswork, which is all any of us have. Oh, and
sign up for Brilliant.com.

------
ohiovr
Actually, chunky salsa problem for people aside, why couldn't this technology
be used for sweeping out space trash? Maybe waste management or Rumpky could
make a deal.

The teather could also be electrodynamic. By putting a current on it it can
push against the earths magnetic field like an electric motor. This can help
with momentum loss slinging trash into the atmosphere.

------
tambourine_man
How about acceleration?

I find the concept fascinating, but would humans withstand it?

~~~
ohiovr
Its not a stupid question. How do you go from 900 meters per second to 6.5
km/s in a few moments without being turned into chunky salsa?

~~~
tambourine_man
Thank you

------
wiradikusuma
What happen if the payload got slingshot off-course? Since it has no rocket on
its own (the reason to use skyhook), it could end up in the middle of nowhere.

~~~
ClumsyPilot
Sky hook gives it a boost to reduce delta-v requirements, you would still have
small engines for on -orbit maneuvering, like all usual satellites do.

------
sandworm101
Not mentioned in video: there can be only one. We couldnt have multiple 1000km
long objects on different orbital planes. Collissions would be inevitable.
These things change speed with every 'hook' event. Predicting collisions would
be extreemly difficult, and impossible to do in time to setup an avoidance.
And just give up on those 30,000+ unit sat constellations. Flies to the
flyswatter.

We would have to keep them all in one plane, probably to line up with the
moon. This would seriously limit thier use beyond orbits in that one plane.

~~~
kempbellt
I am picturing it being similar to a ferris-wheel. You could add more carts
(more hooks), allowing for more capacity.

But I'm also imagining a more sophisticated ferris-wheel, where you stick two
together (side-by-side), allowing for even more capacity.

Picturing it like spokes on a bicycle wheel might also help.

I wonder if there would be much need for more than one.

~~~
sandworm101
Except you cant. The rotation of one tether changes witg each hook event. No
two would ever be turning at the same rate. So you cannot bolt multiple into a
wheel system. You could certainly improve one, make it heavier/longer/bigger,
but it cannot have multiple strands.

~~~
kempbellt
[https://youtu.be/dqwpQarrDwk?t=360](https://youtu.be/dqwpQarrDwk?t=360)

Fair point, that would indeed be a problem.

This part of the video alludes to what I'm getting at. Granted, they are using
a moon as the weighted object, so rotation wouldn't be affected by hook
events.

I wonder how massive the weighted object would have to be to make rotation
changes negligible, or at least manageable.

~~~
sandworm101
Even with a moon, there would be considerable wobble. A strand lifing a ship
would slow down relative to the moon. The moons rotation would eventually
accellerate the strand back up to the moon's rotation rate, but there would be
considerable back-and-forth motion. Pick up too heavy a load and the strand
may start to wrap around the moon.

------
77544cec
There is much that is strange, but nothing

that surpasses man in strangeness.

He sets sail on the frothing waters

amid the south winds of winter

tacking through the mountains

and furious chasms of the waves.

He wearies even the noblest

of the gods, the Earth,

indestructible and untiring,

overturning her from year to year,

driving the plows this way and that

with horses.

And man, pondering and plotting,

snares the light-gliding birds

and hunts the beasts of the wilderness

and the native creatures of the sea.

With guile he overpowers the beast

that roams the mountains by night as by day,

he yokes the hirsute neck of the stallion

and the undaunted bull.

And he has found his way

to the resonance of the word,

and to wind-swift all-understanding,

and to the courage of rule over cities.

He has considered also how to flee

from exposure to the arrows

of unpropitious weather and frost.

Everywhere journeying, inexperienced and without issue,

he comes to nothingness.

Through no flight can he resist

the one assault of death,

even if he has succeeded in cleverly evading

painful sickness.

Clever indeed, mastering

the ways of skill beyond all hope,

he sometimes achieves brave deeds.

He wends his way between the laws of the earth

and the adjured justice of the gods.

Rising high above his place,

he who for the sake of adventures takes

the nonessent for essent loses

his place in the end.

May such a man never frequent my hearth;

May my mind never share the presumption

of him who does this.

Antigone, Sophocles

------
rini17
I fear that by the time this becomes feasible, the orbit will be too crowded
already with satellite megaconstellations. Surely the satellites will be
equipped with collision avoidance, but tether is bigger target than another
sat.

