Skyhooks & Rotovators

[@TripedalTroductions]

These videos can be a bit infuriating sometimes because the points made are so grounded in reality, so carefully thought through, and so well-explained that after the video is over I have to sit there and think "WHY HAVEN'T WE DONE THIS YET?!"

[@Barskor1]

Every time there is a radical shift in technology there comes political change and that scares governments.

[@danielhall271]

NASA has actually done some preliminary experimentation in that regard. They sent up a tether/satellite combo on the space shuttle. The idea was to deploy the satellite by tether from the space shuttle, the shuttle and tether would lose momentum and return to Earth while the satellite gained momentum. Mid-way through the process the tether deployment system jammed and NASA had to release both satellite and tether into space.

[@chasedaily8134]

I actually wish there were more calculations showing material capabilities and things like that. I think the length of the tether might be feasible, but if it isn't a completely rigid structure how will it respond to the forces at play? Also, what would the acceleration be from the spinning tether and could anyone survive that or would it have to be used only equipment. How much would the orbit degrade with frequent launches? Ion drives might not be enough to handle that. All in all, it is a cool video but it doesn't elaborate on the technical difficulties and actual math behind what would be needed. This all works in a digital 3D space, but I need some hard numbers before I know if it makes sense.

[@isaacarthurSFIA]

Oh the acceleration from spin is pretty high, we walk through some of those calculations next week in regard to spin gravity but as mentioned it's linear to length and square of angular velocity. One rotation per hour is 0.017 rad/s, two per hour would just be double, every other hour half. Pick a value, square it, multiply by half the length in meters. Divide that by 10 if you want gees. A 2000 km long one rotating around it's center once an hour would experience 30 gees at its tip, a 1000 km one doing the same 15 gees, but a 2000km one rotating once every 4 hours would experience just 2 gees, and a 1000k one 1 gee. We mostly contemplated once rotating no more often than once every 8 hours, so even one 8000 km long would only be 1 gee at that rate. Though that was all napkin math sans napkin so those numbers are fairly approximate.

[@TripedalTroductions]

Well, I'd guess that the acceleration would probably be whatever you want it to be, but the less acceleration you want, the longer the hook will need to be in order to conserve the most angular momentum. Or alternatively, make the weights at the ends larger and make sure your payload mass is significantly less than the moment of inertia of the skyhook, giving you more wiggle room for restoring momentum. If you haven't had a basic physics course with at least integral calculus, the real math and physics that Isaac is doing behind the scenes would probably be daunting to you, so I'm assuming that's why he only displays algebraic equations, to denote the general and important ideas in physics that are being employed in that particular situation, encouraging anyone who is curious to learn more by giving them starting points for independent research. I agree though. I think Isaac should include a "script" of mathematical proofs in the video description so the super nerds can follow along. Actually, given how professionally put together his videos are, he just may do that in the future!

[@josephmarchesi4168]

Anyone here from Kurzgesagt's Skyhook video?

[@FloofyTanker]

Me

[@ThanhLe-sn5xp]

Me too

[@mito._]

Aye!

[@sahinyasar9119]

Skyhook ( Rotating Type ) + The Skylon or Virgin Galactic = Age of space invasion and colonization

[@gamingchamp6728]

Me

[@theCodyReeder]

Man your videos are looking better and better!

[@DigGil3]

Yeah, at some point Isaac should make the spaceship art for PBS Space Time so they can stop stealing from EVE Online.

[@isaacarthurSFIA]

Thanks Cody! Amusingly just a couple minutes ago I hooked up a new monitor and realized with shock that the old one wasn't HD 1080p, so I was a bit taken aback at realizing I've never really seen my own videos before.

[@theCodyReeder]

What about using tethers to bring material back from space say platinum mined from an asteroid? no need for heat shielding! It would get it down to a speed that parachutes would work just fine! Also would dropping material speed up the tether? If so you could send down some to make up for the stuff you bring up.

[@DFASixMarbles]

That's correct! The velocity of an object returning to a hyperbolic trajectory's perigee from a high orbit around the sun would be very high, and that would be transferred to the tether. If a sufficient quantity of material were brought to earth rather than launched, the new problem might be: how do we slow down the tether? The tether would be very useful for putting an object on a hyperbolic trajectory to leave earth orbit, but there's nothing stopping us from climbing partway up the tether and disconnecting in earth orbit as well. This means the tether could be useful in deploying other launch systems! This would potentially reduce the cost of constructing a space elevator. Thoughts?

[@isaacarthurSFIA]

Yes, using them to slow stuff down does transfer its momentum to the tether too, so you can use it cut down on the speeds you re-enter at and regen the tether while you're at it. It's ideal on airless worlds where aerobraking isn't an option but it should help cut down on the shielding vehicles would need coming in, which is handy is you're shooting pods of precious metals home from the Belt etc.

[@kermanguy1877]

"Oh, there goes Bill." "Damn, another one?" "Yeah, last week it was Ted. Someone should probably figure out how to control the giant hook that pulls people into interplanetary space at some point."

[@itsfrankly4866]

Upvoted before actually watched. No regrets.

[@mycinematics8948]

It's funny, I do that same thing. It's the only guaranteed thing to happen during a Thursday.

[@isaacarthurSFIA]

I'm not complaining :)

[@Copo0604]

This is not Reddit

[@metalspider7735]

just an ordinary gamer do not insult a being above us all

[@sol029]

I do that because I know it'll be great and this way I can tell if I've been through it before. So many great episodes from Isaac!

[@gaiusjuliuspleaser]

If humanity ever builds a Cardio-Rotovator, we owe it to ourselves to call it the Perigee-Apogee Tether System. Or PATSy for short.

[@lazarus2691]

For the first few minutes i was like "But muh conservation of momentum!" And then you said you would address the issue, and you did. Thank you

[@isaacarthurSFIA]

Yeah the momentum issue being glossed over in the original was the biggest motivator for redoing it.

[@felixbodenstein4186]

Perhaps I missed the nuance of how you addressed this, but as I understand how you solve this problem, you're relying on very weak propulsion (rocket fuel defeats the purpose entirely), so using ion drives, which are far too weak to offset the regular launches of multi-tonne payloads. I'm seeing the same problem with using orbital rings as launch pads. every time you accelerate something along the ring in any direction, you need to account for momentum in the other direction.

[@milky_wayan]

yeah part of me really likes this idea but part of me is worried it's like a perpetual motion machine where the caveat is you need to keep adding energy to it. it maybe wouldn't be so bad if we were mining the moon for water and using some of the oxygen and hydrogen we extract to continually launch the tether back in place, right?

[@milky_wayan]

alright so I read into it and what he kinda forgot to mention for skyhooks is that you need either a very heavy station or perhaps a small asteroid as a momentum bank. This way it's orbit would decay very slowly and you could easily just lift it with ion engines every once and a while.

[@badbeardbill9956]

Yeah. It loses momentum, but the question is how much per year, and then you figure out how much needs to be added.

[@iamjimgroth]

I've fallen asleep to these videos so many times. I just love listening to the detailed information about space while drifting off. Makes for some awesome dreams. Of course the first time a video is viewed it's impossible to not pay attention! Thank you, Isaac. :)

[@crazyahhkmed]

Jim Groth I'm the same way . I put videos I've already watched for sleep, like Interstellar Colonization.

[@iamjimgroth]

Taiwanlight I see what you mean, but that was not my intention. :P

[@milky_wayan]

lol me too.. I love the channel to death but if I need to cure insomnia I put on one of the videos I've already seen and lie back.

[@HuntingTarg]

They're far from boring though - more like mentally mesmerizing. I think its fantastic, giving the subconscious something to chew on while the conscious takes a siesta.

[@EddyA1337]

I need stuff to listen to to sleep as well

[@terrynielsen4832]

This is one of the few presentations with music that enhances the message. Many KZbin videos have annoying soundtracks that make it hard to understand the message. I found this video while looking for info on how well a Falcon 9 first stage would work with a Rotovator. I've been waiting for more than 30 years for a company to build a rotovator system and go public so I could invest in it. I've been waiting for Spacex to go public also.

[@SarabandeGreens]

Yesterday was so hectic that I didn't get to do my traditional "get home from work on Thursday morning (The beginning of my work week) and put on Isaac Arthur's new video." routine. It was horrible! But hey, only one day late and definitely nothing short. I remember the treatment of Skyhooks earlier on the channel being disappointingly sparse, and I definitely remember that phase when you were trying to make short(er) videos. You're definitely unique enough to not need to follow the pattern of others on KZbin. Glad to see you revisit it with your usual care and depth. Oh, and still love how well your openings are timed and arranged, gets me every time!

[@isaacarthurSFIA]

Thanks Ellen, and yeah I really disliked the original, I'm trying to decide if I should delete it or redo all the links to it to the new version.

[@abz998]

$500 mill launch and setup for a single system. 10 tonne a day @ $100/kg = $3 billion in revenue over 10 years. Would expect the lifetime of the system to be over 20-30 years.

[@isaacarthurSFIA]

I wouldn't want make many guesses about that first generation's service time, but even if you could only do one 10 ton hook once a week for one year it would seem worth it.

[@deep_dive6699]

BFR might change the economics of the initial setup costs. If BFR can put 150 tonnes into orbit for a few million we now have a launch system capable of putting 3 tonnes into orbit per swing. If it is reboosted via electronic dynamic tethers it will be good to go in about 5 days. This would be a good satellite launcher however it might make more sense to launch it in several loads so it can fire ~15 tonnes into orbit per go so large assemblies could be constructed. Also assuming that we devote 50% of the mass put into space to more tethers into orbit we end up with a doubling period of 500 days, after ten years we could be putting 190,000 tonnes into orbit per year.

[@bentopalchemistfranklin7797]

I simply can't believe how undersubed this channel is Isaac... It's borderline criminal.... Your material is top notch!! I only discovered your channel about 2 months ago... Ended up watching all your videos within about a week lol... Also, I'm glad you decided to scrap the short video idea, your channel is the only one I've run across that goes past the surface of these ideas, and it's invaluable.... Those that can't handle a somewhat lengthy video on a topic weren't really that interested in the topic anyways... Personally I can't get enough and think you should throw some 5 hour marathon videos our way!! (I might not be serious about that last part........probably......)

[@AdarBlu]

Maybe not a video, since I doubt the time invested to create it would be justified by the number of views, but I would be interested in seeing a long form podcast ?once a month? with qualified co-hosts (an engineer, a physicists, etc.) to discuss a given topic at length.

[@martinkrehbiel560]

Had the same experience this January

[@isaacarthurSFIA]

Oh the video component is generally only 20-30% of the production time. But I probably will start showing up on some other channel's hangouts and podcasts inside the next month or so.

[@henrikmunkmadsen3190]

Make sure to tell us if/when it happens :)

[@fobusas]

Yeah, cross promotion is one of the best ways for good channels to gain subscribers. It's word of mouth on steroids.

[@starfyter87]

With minor aspirations of possibly being some level of sci-fi author, either illustrated or full on comic form, I find this concept incredibly interesting! Especially the idea of just "picking up" cargo from the surface by a rotating one, and using some form of station keeping. I bet it would look very unsettling to see for the first time; the hook descending nearly vertically, and just gingerly grabbing onto whatever was placed on the platform, and ascending back up nearly vertically again. Just the mental images alone that I got were very much worth watching/listening to this, thank you very much for creating these videos.

[@LuisEdGm]

Could the skyhook gather Ion thruster fuel from the planet atmosphere when the hook is going down if the planet has the appropriate air composition?

[@isaacarthurSFIA]

Huh... yes it probably could. I was going to say no but the exhaust velocity of the ions ought to be decently higher than the scoop speed. I was also going to say I figure someone must have thought of that already and ruled it out but we almost never consider the ion option because of the Electrodynamic tethering option. Well done, that may well be the first time anyone's thought of that Luis.

[@larrybeckham6652]

Reaction mass from the atmosphere. Ionization and acceleration from ET (Electrodynamic Tethering power). I like it! No solar panel to catch micrometeroids or drag upper atmosphere like the Space Station.

[@DrewLSsix]

Larry Beckham. where would the power for either the thrusters or the electrodynamic options come from if not solar? I mean there are other options but solar isnt a bad one.

[@larrybeckham6652]

Look up Electrodynamic Tether on Wikipedia - it generates power. It have been tested. Reaction wheels could affect the rotation of the Skyhook or ion thusters at the ends. Or both.

[@larrybeckham6652]

Well, I cannot disagree but not much xenon is available. You work what what's there, especially since the supply is so plentiful. Better to separate the O2 and cool in a cryotank and launch in to orbit for oxidizer and breathing. That will improve the economy for this Skyhook.

[@TheGamerLiam]

Issac Arthur, your content is easily some of the best and most fascinating on youtube! Keep it up!

[@GLTDubstep]

I spend all week looking forward to these. Absolutely incredible :)

[@tergav8312]

This has to be my favorite youtube series. While all the futurism stuff is very cool I love to see ways of getting into space that could be build in my lifetime

[@Alexrider02]

These animations add such a feeling of quality to the production. I'm excited to see what you have in store for the Life Support episode. I'd love to have some more intricate inspiration for ship designs in some sci-fi stories I'm working on. :D

[@valrond]

Enjoying weekly science with Isaac Arthur. Ready with my coffee and snack :D

[@blackhand7294]

Isaac thanks for all the videos you posted and continue to post. My favorite part is how you give longer videos than other scifi/astronomy/ space content creators. My pet peeve is when people make sensational videos with misleading titles and goofy graphics. You point out facts with a good mix of sci-fi and it makes it much more interesting.

[@CommieBastard-dj9ot]

Been binge watching this channel for the past 5 hours. Such good content! I'm really impressed

[@thelastneanderthal3257]

This is literally the only channel I ever subscribed to. No kidding.

[@gden130]

The Last Neanderthal. Me too. I recently subscribed to Colin Furze's channel, but yeah.. Isaac's, is pretty much one of the very few that deserve my subscription.

[@gden130]

The Last Neanderthal oh and JoergSprave's channel... that's pretty good too.

[@Jondiceful]

The Last Neanderthal you might also like PBS' SpaceTime. I think it was my love of Space Time that led KZbin to suggest this channel. And now I'm hooked!

[@omegasrevenge]

Someone get Elon Musk on the Skyhook bandwagon!!

[@condescendingonlineman2136]

No, we need him on the orbital ring train

[@WhatIsMisophonia]

One year later: Musk is just an over-rated business man and too focused on his pie in the sky vacuum tube transportation system and other pointless crap. Even the ability to softly land a rocket on a pad had already been accomplished before Musk, he just nudged it forward a bit. The man doesn't seem to match the hype, he's just good at generating hype.

[@EddyA1337]

hahaha I actually thought this while watching this episode

[@bobjoe109]

@@WhatIsMisophonia SpaceX is the first and only to land an orbital booster, now having done it dozens of times. They currently have the most powerful operational rocket, and are working on developing the absolutely amazing Starship/Super Heavy. Not to mention their launch costs are much cheaper than other launch providers. Tell me again how he's overrated?

[@barrygillis]

@@bobjoe109 The insecurity of the people defending his cult status pretty much gives it away.

[@HumpX]

The thing I admire about Isaac's vids is that he explains engineering concepts in a manner that is easy enough for the person of average intelligence to understand without resorting to insultingly simple childish analogies (Dr. Michu Kaku I'm looking at you).

[@corytracy8993]

Someone tell Elon Musk!

[@klausgartenstiel4586]

Cory Tracy i was thinking the exact same thing. his team probably has it on their drawing boards somewhere though. these guys are pretty rad.

[@martinkrehbiel560]

I commented the same thing :)

[@ixian_technocrat]

He's too busy with his dumb hyperloop.

[@martinkrehbiel560]

Faster transport isn't dumb. Sure it's less flashy than getting to space, but it is a worthy project in my opinion :)

[@loganmilliken2727]

GET THIS VIDEO TO ELON MUSK (i was already planning on saying that... caps were a necessity)

[@pembini913]

I have severely impaired hearing so I truly appreciate the closed captioning being included and updated with the script instead of the algorithm figuring out what is being said, and poorly at that so, thank you

[@2000johnwhite]

Great episode, I've binged watched nearly all of these will definitely be taking a second pass, and looking at things in more detail :-) While I'm no scientist, your channel has helped give me a grounding in the various concepts (I'm interested in them all) and for that I thank you...

[@isaacarthurSFIA]

You are very welcome :)

[@TheZabbiemaster]

Funny, looking at this, that thing has to be the size of africa in length

[@DrewLSsix]

TheZabbiemaster. it doesnt have to be, but it could be that long or longer.

[@pewheretic7967]

All these vids are perfect for a home-study group. Getting young minds (any mind) to discuss, question, debate, and get excited about using the grey matter between their ears is essential to further us along as a species. Every kid (I assume) has spent a few hours looking up into the sky and wondering. But they lose that sense of awe and curiosity too soon without some sort of fuel to keep them going. These vids are the spark that reignites that early wonder.

[@isaacarthurSFIA]

As a home-schooler myself, that's a very welcome remark.

[@TheyCalledMeT]

just rememberd this video after "kurzgesagt - in a nutshell" made a skyhook video recommended upard bound in general. gosh darn .. that intro music .. still gives me the chills

[@FloofyTanker]

Me

[@terrablader]

Btw you often mention speach imped. your voice is soothing and smart. Cant say that for most other youtubers.

[@myusername5]

Great video. Kareem Abdul-Jabbar would be proud.

[@dleddy14]

I'm reading Seveneves, which has brought me back to view this again, as Stephenson does use them in his book.

[@Leodeusrex]

thanks for always making awesome videos isaac ♥

[@isaacarthurSFIA]

Thanks for watching them!

[@heisnotlongbutthin]

i have been on youtube for a while now and i have never ever seen the like to dislike ratio your videos get. Quiet deserving i might add. Greetings from austria happy Arthur`s day

[@KT-ti9bk]

Isaac Arthur glad to see your channel growing. You deserve it man! Keep it up

[@prakadox]

This episode was all it could be. Awesome! Introducing new concepts I didn't know earlier - check - the cardio rotovator, the ladder of small rotovators. Big aha moments and smaller "that makes sense" moments. I'm surprised you mentioned that a skyhook is more expensive than an orbital ring. I will wait for the new orbital ring video to understand that as well. The skyhook could be an excellent vanity project for a country wanting to show off and bootstrap a new space era as well. Guys, look at this video and start creating one now!

[@isaacarthurSFIA]

More expensive in cost per kilogram launched, partially from the presumed premium since you are a bit bottlenecked as to how many hook you can have.

[@karimshebeika8010]

you are doing an amazing job, can´t thank you enough

[@sambeatty2312]

I have to do mechanical design Homework tonight but I've been binge watching your videos. Bravo sir, you've made the perfect distraction for aspiring aerospace engineers.

[@grahamwinchester7178]

another amazing video....arthur and his team are knocking things out of the park. this is my favorite show on planet earth :)

[@firstandlastname6194]

I love the whole concept. Like kinetic jump gates, rigid departure and arrival destinations but with the capability to propel you huge distances.

[@dionemoolman]

There’s another key way to keep it up: When an object goes up the skyhook, send down one with equal mass. It will give momentum to the hook while the upward one takes it away, leaving the system in equilibrium.

[@angelosasso1653]

Your growth rate regarding the channel is very nice, considering this isn´t mainstream at all.

[@canalcobrudo2959]

One day, i realy hope anybody make a Documentary of all your topics, and make the animations like the new Cosmos

[@wolf1066]

I was just thinking of the space debris issue regarding having vast tethers spinning around through orbital space then you mentioned that you're going to address it in a later video. Awesome. This is exactly why I subscribed to this channel.

[@FloofyTanker]

Saw this in my recommendations because of Kurzgesagt's Skyhook video

[@hudsondunn8385]

Eternal Goddess Diddo

[@erwinheinrichstromer1156]

Ha, me too

[@hansherrera8809]

This series is getting really interesting and trippy, looking forward to the next video. Cheers!

[@Belows682]

No please don't do short videos. Details all the way!

[@carsonalbrecht3215]

Great video! I remember making a presentation on EM tethers in university, but you did a far better job explaining them than I ever managed to.

[@gregstevens7520]

These are amazing videos, thank you for creating them. I'm so glad I found this channel!

[@andrewbenner6349]

Your face deserves to be on currency. This digital library you have amassed will allow our descendents to respect us. Thank you.

[@ferdinand7467]

But when the skyhook is losing momentum when picking up a spaceship, wouldn't it gain momentum when laying it down on the surface? So you'd just have to let it pick you up, complete the mission, let it lay you down, and it appears like nothing happened

[@bobcheadle985]

I literally never comment on videos but after watching several of yours fpr months now i feel obligated to let you know how wonderfully informative and high quality they are in both presentation and content

[@brbyington]

yessssss more Isaac Asi... er Arthur :D

[@isaacarthurSFIA]

I'm listening to an old Robot Novel audiobook of his right now :)

[@arcadiaberger9204]

My father served on SAC aerial refueling planes in the Air Force, and I've always had a special fondness for the technology - also a special respect for the dangers involved, since it's one of the most hazardous duties in the USAF. It's clearly high time to begin building experimental skyhooks and working out the kinks in them. After all, we still need to get those darn launch costs down!

[@CZY108]

How to get to space: Norm ppl: Uh, rocket? Scienctist: SPACE YEETER

[@Barnardrab]

The mass driver episode is the one I'm looking forward to the most. So far, this channel has glossed over that, favoring sky hooks and orbital rings instead. I'll be excited to learn more about the science and potential of rail gun technology.

[@enbygaming5996]

“But it could work on a place like the moon” *shows Ceres*

[@jorgepeterbarton]

Curweez?

[@amonal42]

3:42 Tether have to be wider not at the top, but at the from-where-it-pulled. In our case it is center. Center have to pull bottom to keep it from falling and pull top to keep it from flying away. The exact location of "center" is point that have orbital velocity. If we change reference system to matching our construction we would have to adjust for centrifugal force. In this system "center" is the "highest" point with zero "gravity" (centrifugal force cancel Earth gravity).

[@HuntingTarg]

I believe you mean the orbital centerpoint. In order to keep the orbital mechanics simple, the centerpoint of a rotovator's rotation must be the point along its length where its linear velocity matches the orbital velocity for that altitude. I agree that making that point the widest, not the 'outer' end, makes more sense to handle the dynamic stress.

[@FutureMatrioshkaBrain]

Watched this before kruzgesagt but I'm watching it again.

[@TheGreenLeaf92]

these videos are absolutely amazing. i'm not especially interested in the subject normaly, but the videos are writen brilliantly which not only makes it entertaining, but extremely easy to get a grasp on and understand. truely amazing job Isaac Arthur, i salute you.

[@kevincloinger3328]

you can still tapper it the thickest point is center.

[@DrunkenUFOPilot]

"this does raise safety issues though" - yeah, I'd like to see all the safety regulations that will be written when skyhooks become real.

[@bart8805]

Bible sized book of regulations

[@LunequeSilvaJunior]

In the "Turn A Gundam" anime series, there was a megastructure called "Zacktraeger" used to lift spaceships from high altitude to space. Now, watching this channel, I can see that it was in fact a skyhook. Nice!

[@Dylnsgames]

Wait so a skyhook isn't a massive fishing hook made for catching space whales?

[@rhorynotmylastname7781]

Just found this comment but this is a dope sci fi idea

[@strictnonconformist7369]

As a software engineer, I can see parallels between skyhooks transitioning to orbital rings or other things being similar to how programming language compilers are created: first in another language, and eventually using the language the compiler compiles, to write the compiler in, and then compile the compiler in the language the compiler is in. (Hope I didn't muck that up). The point is, you start with more expensive ways to create foundational technology and infrastructure towards what's hopefully cheaper, more efficient technology and infrastructure until you get what you need: you build tools to build tools, recursively, to get things done. This is what happened with the moonshot, is a lot of technologies needed to be developed to get to the ultimate goal, and it was done iteratively. So, if orbital rings or (eventually, when materials technology catches up) space elevators are cheaper to use to get things in and out of space, but the cost of skyhooks is cheap enough to get going and still a net win for costs (it harvests non-earth fuel to regenerate) and it's not as cheap as orbital rings, since nothing else seems to have been reasonably proposed for getting the mass required for orbital rings into orbit, why not use skyhooks until you have orbital rings, for being "cheap" to accomplish it? Otherwise, I can't see a cheap way using rockets to get enough material to build an orbital ring: even reusable rockets will still require a huge number of them. Never mind that even the most reliable rockets are not the safest when it comes to BOOM situations.

[@727Phoenix]

When I first learned of this years ago, I realized this is the most likely option to our current method of attaining orbit (after a few thought-experiments, just to be sure). I suspect the first incarnations will be incompatible with human cargo as it may generate too much gee forces on account of it being shorter. Or maybe not, now that you've addressed the shorter but faster-rotating problems of structural integrity, thank you very much. If I ever get to writing short stories or novels, it's resources like these that will be immensely valuable as I restrict myself to what's possible instead of anything approaching pure fantasy.

[@emmanuellegarcia847]

Imagine how humans get yeeeeted in to space.

[@carso1500]

Space trebuchet

[@unitedspacepirates9075]

2000 dirigibles with hotel suites, each connect with 500 feet of elevator cable. Allowing a single elevator from ground level to 100,000 feet where small rockets are launched to carry skyhook components, satellites, etc into orbit.

[@SALSN]

Absolutely love all your videos, I can't get over how interesting and thorough they are! Is Isaac Arthur your real name, or a pseudonym inspired by Isaac Asimov and Arthur C Clarke, or possibly something entirely different?

[@arandomzoomer4837]

I agree it is a very, I don't want to sound snooty when I say this but like, intellectual name. I mean the smart soundingness of a name has nothing to do with someone's actual intelligence, I was just noticing an air or feeling that arose from his name specifically.

[@LeDank]

Just found your channel and I'm super glad I did! Your in depth analysis and graphics are awesome!

[@VoytEngineering]

provide some links to patreon or your fan site, at the beginning of the videos. i know that your talent and presentations are exceptional! you can do this as a full time job or business venture. And thanks.

[@isaacarthurSFIA]

:) There's a link to patreon in every episode description, but I prefer to bring it up every few episodes at the end instead, figure its fresher in the mind at the end when the episode is done.

[@roberticvs]

I believe the rotovator was depicted in the novel "Seveneves" by Neal Stephenson. The spacefaring human race of the future had some astonishing tech utilizing orbital mechanics. This particular one was called "Thor", and it would pick up people off the ground in emergencies and fling them into a high orbit -- um ...safely, somehow. Never quite understood it until seeing this vid. Well done, Isaac Arthur!

[@Ballacha]

It didn’t catch on because of the lame name. To attract attention, it should should be renamed Space Yeeter

[@thezyreick4289]

Let Elon build it and that might become a reality. Then he'll make a special rocket called the yeet seat for public transport

[@mmeiselph7234]

F9 is moving around 2.3 km/s at stage sep, so it's not implausible to have a skyhook above serious atmospheric concerns that can capture a stage 2 craft entirely. The question becomes; what would the mass of such a system be? Likely multiples of the S2 mass, right?

[@Bastoto]

I know you're here after watching the kruzgesagt's skyhook

[@FloofyTanker]

Me

[@LibertarianLeninistRants]

damn, I subbed to Isaac for a year or so but never watched the skyhook video until today

[@CreeperDude-cm1wv]

Yee

[@tishaak2800]

How did you know?! @Austine Ochieng

[@AlexServirog]

I pretty much overlooked your first take on skytooks, very happy that you made this deeper version! Seems like there's a typo in credits, its says "Upward bound: Space Elevators Season 3, Episode 12" instead of Skyhooks. I'm not sure that you mentioned this question: What keeps skyhooks straight? For rotating hooks its easy, there's centrifugal force. But for stationary hooks made of flexible material like Kevlar things are different. Top end travels at speed higher then orbit speed at that height thus "wants" to escape, bottom end travels slower then orbit thus it's falling. This difference will keep tether tensioned and thus straight. P.S. intro/outro is awesome.

[@isaacarthurSFIA]

It's both, I decided I needed to number the episodes production-wise, this is the twelfth episode this year.

[@Mr.Roboto_]

So it yeets rockets into space for less the costs? Nice.

[@thureintun1687]

Why only 731k subs? I think KZbin needs to recommand this channel to more people who interest in everything astro-science. I think that is the case here because I got to see recommandation from this channel only now, even tho i've watch astroscience stuff and did sub-ed to almost every channels related to that subject, and this channel being running for many years . There are very good channels like NASA, PBS, Anton Petrov's, Scott's channel. and many more, but any of those is like this one where you have detailed discussion of the subjects like colonization, terraforming and human settlements of the future etc. i mean kinda like futuristic you know. This channel is now in my collection of space science channels with its own unique contents which doesn't like any others. Thanks Isaac !

[@jakejones5895]

How would we prevent space junk from cutting the tether though?

[@RandomPerson-zl6uz]

We can’t really, only the same way the ISS protects itself…

[@IgnemFeram01]

What's better than cooling off after command PT? Cooling off after command PT and watching one of Isaac Arthur's new videos.

[@Deathworg1]

Great video! When you pronounce circular "sorcular" Its freaking hilarious. Amazing video, wildly informative.

[@danielpalacios9969]

Glad to see someone discussing space tether systems again that are NOT space elevators. This is a very poorly known alternative to rockets with tremendous potential. Love the detail you put into your space tech videos. You might want to see a related You Tube video called Martian Rotovator Swing which shows how a martian spinning tether could launch a spacecraft. It's based on a Celestia Addon available at a webside called Celestia Motherload under fictional craft & stations.

[@TheNewMaxico]

great video! i understood all the things i previously didn't understand in the old skyhook video

[@isaacarthurSFIA]

That I am very glad to hear, I always felt in hindsight it give way to thin an explanation.

[@paxdriver]

Bad advice keeping it brief - so glad you listen to yourself and fans. Big ups man, thanks for another awesome video!

[@Nemesis_T_Type]

Can you make a topic about cleaning space debris?

[@isaacarthurSFIA]

:) I decided to do one a few days ago, there was a poll about the title [tentatively, "Space Trash"] over at the Channel's Facebook group.

[@Nemesis_T_Type]

That's great. I can't wait to watch it. I really hope there is a way to remove the debris out there. We can't risk losing access to space. This problem needs to be addressed soon because we can't build sky hook and space elevator if there is a danger of space debris destroying the structure.

[@romaingarriot5710]

Would it make sense to include debris recycle? collecting everything at the same point, listing each items in an online directory, so companies can pay and reserve them at a fraction of the price it would take to put this "material" into orbit...?

[@xassix]

Best Upward Bound episode yet. Crazy idea: Would an elastic tether, that can increase or shorten its lenght be an option?

[@russellbackstrom5056]

dude I've watched all your videos like 5x ..especially the simulation argument and Dyson dilemma now Thursdays are my favorite day.. heck sky hooks are probably my least favourite subject you have done so far. . and I still love this video.. oh and ya the new animations are dope... hey Issac I have a idea for a video.. how about one about what it will take for us to take the next step as a civilization on the K scale? I was thinking.. with all the crazy stuff that's been going on lately.. maybe video on our current state.. where we are going and where we need to go to get to K-1 .. I know you have covered it several times... but I was thinking something super in depth like u do now?

[@isaacarthurSFIA]

Hmm... perhaps. I wouldn't mind talking more about the Kardashev Scale, Russell, in that sort of sub-topic way, which is kind of what Ecumenopolis and Starlifting both were.

[@kiliank5040]

Just discovered this channel. Were have you been all my life Isaac?! Your videos are the best combination of interesting, entertaining and informative I have seen so far on KZbin. Keep up the amazing work!

[@blipmachine]

This technology is also useful for returning a mob boss from Hong Kong to the US when the Chinese won’t extradite a national under any circumstances.

[@lordbinkythebuffoon5465]

Yes at about mach 40 lol!

[@browerkyle]

I love hearing the phrase "get up to the necessary hooking speed." Great video as always! e: corrected the quote.

[@abz998]

Any papers on the atmospheric drag implications?

[@isaacarthurSFIA]

I think they talk about drag on the tip in the attached paper from Being on HASTOL but it's fairly straight-forward drag, with the obvious supersonic caveat.

[@Alexis-hx3yd]

Isaac, its time to get you on tv , if anybody in tv is watching, please get this guy his own series, we don't have a futurology series that I'm aware of, and Isaacs' style would fill the void brilliantly. We had "Tomorrows World" in the Uk and that finished over 30 years ago and it was wrong about most things. Apparently we should have settled on Mars 20 years ago.

[@alicewaweru5201]

Should deorbit vehicles to regain energy

[@Rykvp]

Or bring down to earth asteroid mining output

[@TheNonplayer]

stuff like this should be common knowledge, like given to elementary school children every other week or so just to inspire them with what we actually can/could do and how far we are in our age.

[@bobsenior9218]

Sky hooks mmm. Probably the cheapest most efficient way of getting flat earthers off our planet. Doesn't matter where they end up. The sun would do.

[@kaiserredgamer8943]

Can't believe one of the most efficient ways to quickly transport stuff across space was to sling them around on a giant trebuchet.

[@Jordan-vr7ip]

Whose here from Kurzgesagt?

[@bluekoolaidg1904]

Rewatching The whole upward bound series again. I love the intro... gets me hyped each time!!! Keep it up brothea!!

[@ye8438]

Ist jemand hier wegen Kurzgesagt

[@nawarelsabaa]

Viel mehr jetzt nach die englische Version 😂

[@feynstein1004]

Ja, ich 😂

[@oscargarciahinde4247]

Your videos are excellent! Brilliantly researched and presented. And I'm happy to see that you've stopped apologizing for your voice: it's always been fine and clear.

[@newestboi5120]

Who came from Kurzgesagt?

[@alexeveleigh6980]

My new favourite channel! Anyone that recognizes the value of the sky hook is a friend of mine!