5 ms·

Cable to the Stars – The Skyhook [video]

83 points by doppp 7y ago

Richard_East 7y ago
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
- ClumsyPilot 7y ago
  Isaac Arthur's series is great!
- ur-whale 7y ago
  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 7y ago
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/
deleted 7y ago
[deleted]
sandworm101 7y ago
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.
- cma 7y ago
  With a one-time tolerance for some nuclear fallout to get it in place it could be done.
- wolfram74 7y ago
  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 7y ago
    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.
  - OnlineGladiator 7y ago
    The video covers this. For every vehicle it launches into orbit, it will also be used to decelerate returning ships back into the atmosphere - conserving its momentum. So it works in theory. I have a hard time imagining it work in practice.
- jspdown 7y ago
  That sounds incredibly expensive to send such mass, same for the cable looking at the current payload weight a ship can send (22,700 kg) [1] 1. https://en.wikipedia.org/wiki/Space_Shuttle 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
- shkkmo 7y ago
  If SpaceX hits their goals with Starship, this might become feasible. I would imagine that the economic viability of a spacehook will lag well behind having sufficient launch capacity to build one. > 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-starship-is-a-very-big-deal/ https://caseyhandmer.wordpress.com/2019/10/29/the-spacex-sta...
wiradikusuma 7y ago
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.
- anotheryou 7y ago
  not much different with a rocket, if you miss your target to e.g. sling around a planet for your return you're lost.
- ClumsyPilot 7y ago
  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 7y ago
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 7y ago
  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 7y ago
    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 7y ago
      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 7y ago
        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.
baby 7y ago
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!
theothermkn 7y ago
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.
rini17 7y ago
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.
77544cec 7y ago
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
tambourine_man 7y ago
How about acceleration? I find the concept fascinating, but would humans withstand it?
- ohiovr 7y ago
  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 7y ago
    Thank you
ohiovr 7y ago
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.

83 points by doppp 7y ago

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

ClumsyPilot 7y ago
Isaac Arthur's series is great!
ur-whale 7y ago
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 7y ago

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/

deleted 7y ago

[deleted]

sandworm101 7y ago

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.

cma 7y ago
With a one-time tolerance for some nuclear fallout to get it in place it could be done.
wolfram74 7y ago
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 7y ago
  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.
- OnlineGladiator 7y ago
  The video covers this. For every vehicle it launches into orbit, it will also be used to decelerate returning ships back into the atmosphere - conserving its momentum. So it works in theory. I have a hard time imagining it work in practice.
jspdown 7y ago
That sounds incredibly expensive to send such mass, same for the cable looking at the current payload weight a ship can send (22,700 kg) [1] 1. https://en.wikipedia.org/wiki/Space_Shuttle 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
shkkmo 7y ago
If SpaceX hits their goals with Starship, this might become feasible. I would imagine that the economic viability of a spacehook will lag well behind having sufficient launch capacity to build one. > 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-starship-is-a-very-big-deal/ https://caseyhandmer.wordpress.com/2019/10/29/the-spacex-sta...

wiradikusuma 7y ago

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.

anotheryou 7y ago
not much different with a rocket, if you miss your target to e.g. sling around a planet for your return you're lost.
ClumsyPilot 7y ago
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 7y ago

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 7y ago
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 7y ago
  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 7y ago
    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 7y ago
      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.

baby 7y ago

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!

theothermkn 7y ago

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.

rini17 7y ago

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.

77544cec 7y ago

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

tambourine_man 7y ago

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

ohiovr 7y ago
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 7y ago
  Thank you

ohiovr 7y ago

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.