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?!"
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.
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.
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.
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!
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.
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.
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?
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.
"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."
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.
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?
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.
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. :)
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.
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......)
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.
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.
This is one of the few presentations with music that enhances the message. Many RU-vid 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.
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.
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 RU-vid. 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!
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
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.
The Last Neanderthal you might also like PBS' SpaceTime. I think it was my love of Space Time that led RU-vid to suggest this channel. And now I'm hooked!
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
$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.
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.
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.
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.
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.
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.
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.
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.
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
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...
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.
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.
@@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?
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
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).
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.
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
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.
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!
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?
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.
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.
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
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.
:) 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.
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.
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.
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.
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
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 RU-vid. Keep up the amazing work!
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.
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?
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.
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.
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!
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.
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...?
Why only 731k subs? I think RU-vid 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 !
Very informative and nicely done videos, i subscribed and have been clicking like on every video i watch of yours, my only fear, running out of your episodes to watch! Thank you for all your time and work you put into these.
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.
i've been binge-watching your entire channel. love the content and your presentations, excellent work my friend. one note i'd mention as well- some love long episodes or lengthy looks into topics. i've introduced your channel to a group of friends and we're always looking for content to listen to while doing other tasks. i'd say, if you think (or other viewers) would prefer shorter videos you could also always cut a longer piece into segments. either way, keep up the great work!
You make a lot of interesting videos that make me feel really positive about space exploration in the future, but this is the first time I've genuinely gone "And just why is nobody making this right this moment?!'.
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!
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.
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!
