Cable to the Stars – The Skyhook [video]
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> 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.
So it works in theory. I have a hard time imagining it work in practice.
1. https://en.wikipedia.org/wiki/Space_Shuttle
> The typical payload capacity was about 50,045 pounds (22,700 kg) but could be increased depending on the choice of launch configuration
> SpaceX clearly intends to build dozens of Starships. With an eventual flight rate of once per day per Starship, we’re looking at roughly a million tonnes to orbit per year. That exceeds the current launch market of about 500 T/year by a substantial margin. [0]
[0] https://caseyhandmer.wordpress.com/2019/10/29/the-spacex-sta...
If you typical rocket lifts 20T, you would built a small sky hook to lift like 1T, and use it to lift fuel and other consumables cheaply. That would bootstrap you to build larger one in the future
I think we are more-less capable of doing it currently.
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.
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.
I find the concept fascinating, but would humans withstand it?
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.
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.
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.
The satellites in these constellations are constantly maneuvering. There's no reason they couldn't easily avoid a sky hook with active correction.
> We would have to keep them all in one plane, probably to line up with the moon.
What keeps them from being synchronized? By moving counter-weights up and down the tether, you can adjust the rotation speed with no net expenditure of energy. So as long as there is a schedule such that skyhooks in different orbital planes are "horizontal" when crossing each other, you can actively maintain that schedule even as ships are extracting and depositing energy from the skyhook.
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