@@CupCakeArmy1 RE: "I was thinking about this, and was wondering if gravitational wave detectors count as the biggest lasers we have ever built." The Laser Interferometer Gravitational-Wave Observatory (LIGO) is a large-scale physics experiment and observatory to detect cosmic gravitational waves and to develop gravitational-wave observations as an astronomical tool. Two large observatories were built in the United States with the aim of detecting gravitational waves by laser interferometry. These can detect a change in the 4 km mirror spacing of less than a ten-thousandth the charge diameter of a proton. These lasers were built for sensitivity not power. The most powerful laser beam ever created has been recently fired at Osaka University in Japan, where the Laser for Fast Ignition Experiments (LFEX) has been boosted to produce a beam with a peak power of 2,000 trillion watts - two petawatts - for an incredibly short duration, approximately a trillionth of a second or one picosecond. References: en.wikipedia.org/wiki/LIGO www.ligo.caltech.edu/page/what-is-ligo theconversation.com/worlds-most-powerful-laser-is-2-000-trillion-watts-but-whats-it-for-45891#:~:text=The%20most%20powerful%20laser%20beam,trillionth%20of%20a%20second%20or www.sciencemag.org/news/2018/01/physicists-are-planning-build-lasers-so-powerful-they-could-rip-apart-empty-space
"Eleven-" - Oh, OK. Ain't much. "…thousand…" - Kilometers? OK, it's over. "…times…" - Oh, just a ratio? Maybe possible afterall? "…the size of the observable universe" - wat.
well for a space elevator, you need a station at 35.786 km height. So you would need to travel 35.700 km. to put that in relation, the ISS is only 400-440km high. That's a pretty long elevator.
well if we did manage to build a cable made of steel (obviously not)...aliens would have no problem locating our position and coming over to say hi. Alien: "Oh we just saw this huge arrow pointing to earth".
I think we should build a space escalator instead, for those of us who are claustrophobic. Plus, if it broke down, you could still use it, because it'd be space stairs.
Hey, yeah! We should just build a set of spiraling stairs up to the Clarke belt! Just make sure everyone holds onto the handrails and wears a spacesuit... :)
@@maxbuskirk5302 Just don't look down. Imagine if you trip and you just keep falling through the staircase all the way down, hitting all thousands of stairs.
"Every engeneer ever has waited their entire life for a problem where the solution was a gigantic laser" That line, my friend, is one of the best line ever written or thought of ! ! Great job ! !
I’m so grateful for your videos! I’ve always struggled understanding math and science but your videos make it so much easier to get a basic grasp on. Thank you!!
Megan Pham I appreciate this video too-you can tell he knows what he’s talking about because he doesn’t hide behind a lot of technical jargon. Also: he uses the terms “centripetal” & “centrifugal” correctly and explains the consequences of those forces correctly, which is a level of detail I don’t often see in videos about space elevators
I just want to say I really appreciate a guy of your intelligence and knowledge breaking these incredibly complex topics down and making them digestible for laypeople. For me at least, it really helps me see where I want to invest my time learning more about something.
I stumbled across your channel today and am hooked! I've been binge watching for a couple of hours and I am so so intrigued. Keep these fantastic videos coming!
Sorry to nit pick again, but in the paper you link regarding taper ratio, it actually defines taper ration as the ratio of cross-sectional areas. not diameter. Your estimate of the resulting diameters should actually be the square root of what you state. A 1 cm diameter steel cable would have to be 4e14 meters at GEO (about 1 ligthfortnight ;) A 1 cm diameter kevlar cable would have to be ~160 meters at GEO
Better not mention that a similar calculation done by someone (not me) who is familiar with the mechanics of elevators puts the diameter at the top as something like 2Km for a steel cable. That's the thing with physics - no matter how much you know or how good you are at the math its still horribly easy to get something wrong. The tiniest misstep like forgetting to factor in reducing gravity with height tends to make all the difference. The gravity at the orbital geo-lock point is of course zero by definition.. :)
My previous post says the top of the cable, its widest point is not there but somewhere at a midpoint. The reason that a steel cable ends up at anything like 2 Km wide in the middle is that 50,000 Km is very very very long for a steel cable.
That's why I'm a bigger fan of the rotational space elevator. Have a cable only about 1850 km long as opposed to 60,000 km. What you do is have the shorter cable in orbit and rotating such that the end closer to the Earth is moving slower than the top. The Ship flies up at less than half orbital speed, grabs on, and rides the cable until it is at the top and lets go. This does impact the orbit of the elevator but this can be contradicted by having ships make the return trip using the elevator. This also negates the need for a heat shield. The advantages are that the cable can be made from carbon fiber and the system does not require a climber.
Are you advocating for a thing dragging a cable through all the circumference of Earth, at surface level with all its irregularities, mountains and seas, natural reserves, cities and what-not (yes, there are several cities located right at the Equator too). I think the UN Security Council would not approve...
My story about the Space Elevator was published under my previous married name in 2005. I was thrilled. Arthur C. Clarke and Ray Bradbury were sponsors and the main impetus behind the contest was Bradley Edwards. I lost my only copy of "Running the Line: Stories of the Space Elevator." (Divorce and ex sold my books 😭 as he is a very mean thing). I caught him, but only got a little of my books. Anyway, I was inspired by the idea of a Space Elevator.
You are doing a great job bringing all of this materials to us that were once only for civil engineers. The way you present it makes it easy to understand. I work in electronics and have never been so interested in physics until I saw your channel. Keep on that track and definitely more and more people will come along to discover the fascinating world of physics.
The main problem with any Space Elevator design, which I've never seen addressed on TH-cam (although it has been discussed in other forums), is something you and almost everyone else is overlooking.It's not cable strength, or the weight it must hold.It's not how to power the lifter.The problem is that the tether could not possibly stand up to even a fraction of the electrical discharge it would carry as it passed through multiple plasma double-layers. It would essentially be like placing a conductor across the leads of a planet-sized capacitor. In the unlikely event it ever made it to the ground, it would disappear in a blinding flash of mega-lighting.
Hey Grady, Loving the direction of the channel so far. There's lots of science-y channels out there, but most keep it simple or avoid equations. I loved the "100 year flood" video precisely because you didn't shy away from the technicalities, and you touched on an uncommon topic; hydrology. I hope you won't be dumbing down future videos in favour of more views, I've come to find a lot of people are tired of the old pop-science format and are turning to channels such as yours and Ben's "Applied Science Channel" for content that intrigues and challenges them. Ben's got some very technical videos, yet his community is quite diverse and full of both professionals and laypeople. I know your hydrology video inspired an entire week of reading up on fluid mechanics and geology in my case! Same goes for this video: before I knew it, I was scrolling through my university's e-catalogue for books on the topic. I love it when youtube videos are capable of doing that, and I'm really glad I stumbled across your channel. Best of luck to you, and keep it up.
+Luka P Thanks, this is really kind. I am doing my best to strike a balance between good technical content and general tedium. My goal for the channel is to increase exposure to the field of engineering and make it more approachable, so that comes with some simplification of the content. Hopefully not too much though!
This was an amazing video. Yes, I've heard all the tv talkers say how wonderful it would be, but you really put the construction into perspective. Thank you.
One method to make friggin' lasers a feasible power delivery method is to split up the workload. Instead of having only a ground based laser, beaming up to the lift, have an extra one at the anchor, beaming down to the lift. Once the lift passes the point where the energy from the ground based laser becomes marginal, the top one becomes the primary deliverer. The top one also doesn't have to deal with atmospheric disturbances, giving it a larger effective range. As for how to power the top laser? The anchor needs to be heavy, right? Sounds like the perfect excuse to plant a large solar array up there.
Excellent plan, but you'd probably want either a nuclear reactor or hydrogen batteries up there as well. So your elevator doesn't stop/fall out of the sky at night.
I sort of like this idea, but the Solar implementation at the top looses me, as well as the break point for the laser. Starting with the laser break point(meaning the point where the elevator switches from Earth to the "space laser"). That specific point, would have to be almost outside the atmosphere to be really just economic enough to implement. Reason being, we would want the "space laser" to(as you also say) avoid distortion to get us up there the rest of the way, but also the break(or switch over) point would mean that there would have to be some power compensation(because of the "Earth laser's" distortion) before we reached the breaking point. That would also mean added weight to the lift, because(with current technology) circuitry involved to make a regulator which could handle the power load for that lift, would only add more weight causing yet again a power vs weight challenge. The idea of putting a solar array at the top, again involves the idea of both electrical power vs weight. A decent enough solar array capable of producing that kind of power to push a laser that pushes a cart up a cable, in addition to the to the distortion of the "space laser"(yes it still has some distortion in space, just not nearly as much as it would going through the atmosphere), would mean that you would need a LOT of panels to create that decent load. A lot of solar panels means a lot of flat usable space, which can be very hard to achieve especially when the counterweight needs to be certain mass which might not mean enough space for panels, in a realistic format.
And who says that it can only be one energy source. Why not eletrcal power from a wire to start and then a boost from a reusable rocket finished off with the Lazer from the top powered by a solar array. Then on the return Lazer to gravity.
In addition to the other answers, I would like to point out the havoc such a laser would cause on earth, were it to ever miss the panel (and part of the beam WILL miss, laser beams are not perfecty homogeneous tubes of light even in vacuum)
Grady, that was cool seeing a glimpse of you on one of your real life projects. I'm sure many of us engineers of other disciplines would love to hear about your work and maybe a little about a real project you are doing or have done.
I got stuck on the space elevator once. Good thing they gave us emergency parachutes and propulsion packs so that I could safely descend all 7320 stories back to Earth.
Another suggestion for improving the nanotube space elevator design: Wrap the cable in superconductive tape and put a circular current around the cables. They will produce a magnetic field along the length of the wires, so if they ever got broken by (say) an asteroid, the 2 ends of the cable would pull back together again like the 2 ends of a broken bar magnet. There is some evidence that nanotubes could be superconductive at room temperatures, so maybe we can put a current inside the cables themselves. A few million amps per meter should be enough. The field lines being mostly inside the cables and the direction being along the length of the cables, this wouldn’t stress the pods travelling up or down the cables.
Dear Grady, you actually revealed the engineering of the sky elevator, I thanks you a lot for such beautiful revealing the engineering connection of sky elevator , stay bless, thanks
They can be built tomorrow, but channels like these don't like practical solution for futurism problems. For something more down-to-earth, go to Isaac Arthur's channel and watch the videos about spaced towers and power satellites. (And yes, I do realize most of his video are about interplanetary and space stuff, when I said he's down to earth. Bad pun intended.)
Could you use the tether as an extension cord? Basically sending power through that material? It would work kind of like a street car except vertical :P
carbon nanotube is basically a superconductor. we could use the tethers travel through the atmosphere (friction) to generate electrical current. the climber could theoretically just draw power straight from the cable as it climbs, provided the structure used to grip the tether is conductive as well.
In order to have an electric circuit, you need two conductors, and thus two cables. And since they'd be whipping around in the atmosphere, they'd short out whenever they touched each other.
Hungry Guy not entirely true. you have one circuit, negative/ground at the base, positive end at the orbiting mass. the cable itself just allows flow, then the climber as two sets of grippers, negative and positive, basically just making a mobile flow gate with attached motor/control center.
I can't believe you didn't mention Arthur C. Clarke! You even mentioned the "Clarke Belt", but you didn't mention his novel "The Fountains of Paradise", which popularized the concept of the Space Elevator!
TO: Alvaro S. There's also Arthur C. Clarke's novel 3001: The Final Odyssey, which goes into great detail about a space elevator. He describes an Earth which has four space elevators that connect to an inhabited ring around the planet. The towers containing the cables are inhabited as well.
The tone and content of this video is a good demonstration of why I subscribe to this channel even though I'm not an engineer. Oh, and I think you have charm and are handsome. :)
The 1st thing is the climber, aka elevator. Batteries are becoming stronger and stronger with longer life times. By the time this could be developed, batteries just might be the solution to the power to get to station. As many batteries are rechargeable, we use the same principle that is used in electric cars. Applying the brakes feeds power back to the batteries. By the time the elevator got back to ground, it would be close to a full charge. I first read of this concept in a book by Arthur C. Clarke, "The Fountains of Paradise." They used 4 cables made of a super strong light weight material. The car rode up and down these cables using wheels with friction brakes. This isn't that different that how some elevators currently work. The story also has another story, or 2. I highly recommend this. As you noted, we are getting some materials that just might have the strength to begin giving this idea serious consideration.
+Practical Engineering Hey, just a nitpick, but at 2:18 you say "force of gravity", but show the equation for acceleration due to gravity, the term gotten when canceling out the little m's. Not a big mistake, just wanted to make sure you knew it was there!
+Matteo Mcdonnell Yeah I played a bit loose with terminology since the mass term cancels out in both equations. I take a bit of liberty with the rigor because I know no one's relying on me as a primary source for engineering education.
Why didn't you talk about space elevators on smaller solar system bodies. I know there has been talk about having the first space elevator be on the moon, because the lower mass/gravity means you don't need as strong of a tether that also wouldn't need to be as long, and the barely-there atmosphere of the moon wouldn't impede a power beaming system anywhere near as much. We would then take the infrastructure and what we learned from building the moon space elevator to work toward an Earth space elevator.
what practical purpose could a lunar moon elevator serve? The experience of building it would hardly justify the absurd expense, especially considering it would do little to simplify the construction of one on earth since the fundamental material demands would be so different. All the equipment and materials would first have to be flown to the moon, an enomous and unprecedented endeavor of itself
+charlesissleepy It would make sustaining a lunar base way cheaper over the long run, especially if you consider wanting to bring lunar material back to Earth in mass. I think you also underestimate how beneficial having a stepping stone to an Earth space elevator would be. Even if none of the developed technology crossed over (which is a bit of a ludicrous proposition), just from a fiscal standpoint of fundraising (particularly in the current socioeconomic climate), it is a far more likely path to actually get off the drawing boards than building an Earth space elevator first. Building a lunar space elevator offers far less risk, while still offering substantial reward if successful. And it is far more likely that whatever technologies, processes, and manufacturing techniques that were developed for a lunar space elevator, would almost certainly directly lead into what would be used for an Earth space elevator.
A lunar space elevator presents a very distinct set of engineering challenges.The moon has inadequate rotation to permit the construction of a space elevator of the same working principle as an earthling one and would have to use lagrange points instead. This means the tether would have to be considerably longer than on earth, 56,000 km on the earthfacing side. The lower mass and lack of atmosphere permit the use of a uniform diameter tether made of existing engineering materials, which clearly already sets it apart from on earth based design (and no research into CNT in massive scale). The tether itself would be massive (using the length and proposed cross section area of the ribbon i figure around 66 metric tons, very likely i bungled the math though) and very expensive both to produce and to convey into lunar orbit. All without much economic motivation, save perhaps He-3. Long-short I don't see it preceding an earth-based project, since any practical use it might have almost presupposes one on earth.
Since the Moon is tidally locked with one face permanently facing Earth, the only place where one would work would be on the far side of the Moon where any kind of centrifugal force would be found. Taking that into account, it wouldn't make much sense taking material to the Moon, landing it from orbit and then lifting the same material out of the Moon's gravity well up to a point where we could reach by simply extending the lunar orbital eccentricity to the point of meeting the same point in space where the counterweight would be. If you are looking for an economical, efficent and faster means of getting to any of the Lagrange points, it would make more sense to use the Moon for a slight slingshot boost to get you there. Now if you are looking for a means to move stuff to the lunar surface, then you may have a point. But for the counterweight to overcome the gravitational pull on it and the mass of the tether, the counterweight would have to be much much closer to Earth for Earth's gravitational force to pull on it with sufficient force to overcome all that lunar weight. I'm not sure what the math would work out to for all of this, but I could see it being done. One of the advantages of having the Earth's space lift's counterweight being beyond the Clarke Belt is that spacecraft launched from the counterweight would be able to put all that centrifugal force to use by merely undocking and being slung into space! It would be interesting to see if and how all that would work, essentially using minimal energy to move materials to the Lunar surface by this means.
Since the Moon is tidally locked with one face permanently facing Earth, the only place where one would work would be on the far side of the Moon where any kind of centrifugal force would be found. Taking that into account, it wouldn't make much sense taking material to the Moon, landing it from orbit and then lifting the same material out of the Moon's gravity well up to a point where we could reach by simply extending the lunar orbital eccentricity to the point of meeting the same point in space where the counterweight would be. If you are looking for an economical, efficent and faster means of getting to any of the Lagrange points, it would make more sense to use the Moon for a slight slingshot boost to get you there. Now if you are looking for a means to move stuff to the lunar surface, then you may have a point. But for the counterweight to overcome the gravitational pull on it and the mass of the tether, the counterweight would have to be much much closer to Earth for Earth's gravitational force to pull on it with sufficient force to overcome all that lunar weight. I'm not sure what the math would work out to for all of this, but I could see it being done. One of the advantages of having the Earth's space lift's counterweight being beyond the Clarke Belt is that spacecraft launched from the counterweight would be able to put all that centrifugal force to use by merely undocking and being slung into space! It would be interesting to see if and how all that would work, essentially using minimal energy to move materials to the Lunar surface by this means.
The biggest problem in my mind is how the heck we actually string up that cable. We would almost need anti gravity technology just to feasibly connect it, in which case we don't need the elevator. The best way I can think is lowering it from geostationary orbit to the earth, in which case we need to take unspeakable amounts of the most expensive stuff ever to high orbit. Anyone thought of what would happen if space junk or debris hit any part of that thing? What about being a terrorism target? What if it broke and literally fell from orbit slamming into everything and wrapping around the earth? What about trying to make such a long, continuous piece of material without breaking it down into smaller pieces to keep it strong. It is molecular in its connection.
Too long for regular wiring. It's the same reason power plants are spread out instead of all being in one place, cause you lose energy over longer distances. You could assume that room-temperature superconductors have been figured out as well as nanotubes, but even in that case, if each metre was only 10 grams, that's still thousands of tons, and then that old taper gets you again.
It needs to be a super conductor to not lose a lot of power from resistance. Or a lot of small energy sources along the cable, which would increase the weight.
Why is nuclear power not an option for the carrier? Wouldnt a mini nuclear reactor like the ones user on submarines produce far more power than a laserbeam?
+Bonta kun hmmmm fair point, obvs not with fusion but that's a long shot anyway isn't it ;) I still think it would be an option, it would be the best looked after reactor on the planet and short of the whole thing falling down I can't see why shit would hit the fan especially with the modern quality of reactors
+Bonta kun and maybe the craft could have a very lightweight payload? One that could be easily ejected if a problem occured? I mean although a lot of energy would be needed it wouldn't need to be like a full city reactor would it? I don't know how much the thing would weight
Hmmm well true just thinking about efficiency. I mean you get nuclear subs but maybe you're right and it wouldnt be worth the efficiency benefit for the huge weight. Still and interesting thought though ;) To be honest I would bet fusion is perfected before graphene but then again without graphene what would we build the thing out of in the first place! ahaha
Well, we already use small fission reactors on some satellites (probes actually) which are very light. And fusion is probably much closer than large scale nanotubes.
Pretty sure that is what he is referring to when he talks about extension cords (ie well due to resistance and such you wont have enough power left long before you reach even a quarter of the way)
@@GummieI Why not have a generator on the elevator? Not sure how feasible that is with how much fuel you would need but that is what immediately came to my mind
@Robert Ibey I am by no means an expert on this topic but generators are HEAVY, VERY HEAVY, I don't think most generators output enough power to lift themselves in the first place. Beside that generators still do need some kind of fuel to generate power in the first place, so what would said generator use as fuel? Wind? Well there are no wind when the elevator is in the space part of it, or maybe its just a day without any wind. Solar panels, what about on the earth part of the elevator journey and a cloudy day?
@@GummieI We can build fuel-based generators that can lift themselves off the ground WITHOUT needing a cable to climb, so this should definitely be doable.
I enjoyed this overview. This is apparently becoming a hot topic. I remember reading Arthur C. Clarke's book on the subject (yes, the same Clarke as the name for the geosynchronus orbit band), "The Fountains of Paradise". A couple of questions, First, I agree with Einar Gissurarson about having an SPS attached to the counterweight and splitting the power load. Why not make the tether conductive and use it to power the climber? Also, the counterweight could be quit far from the Clarke band so we could use it as a cheap method to launch Solar System ships. Also, I have read of two other methods for a space elevator. Clarke listed one in a different book (I think "The City and the Stars") which used a rotating tether/weight system so you wouldn't need a climber. I think Neil Stephanson used it in "Seveneves" as well. And Dr. Robert L. Forward wrote about a fountain of rings in Starquake. All of these have their own problems in terms of currently impossible engineering challenges. I think the largest challenge however is overcoming the character of the human race. We've seen just this century on the internet how something that can be massively useful gets abused or destroyed by a few individuals who want to smash things to see them smash, or to give them a short-term advantage, or to destroy the creators because of jealousy, spite or perversity. We're about to see it happened again, IMHO with the Internet Of Things (IOT) since the engineers continue to insist that because it's so useful, no one will want to misuse it. Again, I liked the explanation, it was concise and not difficult to follow.
you should check out the channel science and futurism with Isaac Arthur. he's got a couple of really good videos on this topic and many videos on related stuff. I'd love to see a collaboration between you two on something.
@@Hallowed_Ground How does that work? And why not put a small nuclear power station directly on the cabin? arxiv.org/ftp/arxiv/papers/1802/1802.07443.pdf
@@3gunslingers this. i scrolled so long to see someone suggest nuclear cabin. we have it in US Subs already. A micro reactor would provide all the power needed.
The problem with that would be that the electricity would just flow PAST the climber, as the tether needs to go past it uninterrupted. Also with a single cable you wouldn't have a closed loop for the current. So you'd need to use two cables that need to be insulated from each other. Either you'd get power from current that you let pass from one cable to the other, or one of the cables is a guiding cable and the other one is a pulling cable that you just reel in from the top. Which would mean that you'd need to accelerate 1000 cubic meters of carbon nanofibers per square centimeter of cable cross section at the climber. Or you could just send the current past the climber and transfer power by induction. You'd still need two cables in close proximity to in order to shield any stray fields , because else you'd have the biggest wireless power transmission antenna ever conceived. @Keyboard runner Having a nuclear reactor next to a structure that could wipe out a whole county if it would break due to ratiation damage does not sound smart. But a space elevator is such a crazy concept that that might actually be the smartest solution... After all, you only need radiation shielding on the side with the cable and passengers.
First, a geosynchronous orbit radius is necessary only for daily orbit periods. Shorter orbit radii are possible, but only for elevators tethered to rotational poles. Second, electric conductors embedded into the cable(s) can charge supercapacitors (or batteries) spaced periodically in the cable to serve as "filling stations" to refresh an energy cell in the elevator. A descending elevator releases energy which can be captured in reversible motor/generator, recharge the cable's cells, and power the electric grid until another ascent is needed.
What most people fail to realise about space elevators is that we don't need a fantastic supermaterial strong enough to hold the tension of the whole thing. We could use an active power structure instead, so it holds itself up with energy instead of strength. It's called a "space fountain". We could use this for super-long single-span bridges too. Grady really should check out active power structures! The space fountain also eliminates the power beaming problem, because you're already sending power up the entire thing in a near-vacuum (so no atmospheric losses). The question is whether we could lower the friction of the system enough to keep the energy costs low enough to be worthwhile.
An easy solution to beaming power to the climber is to beam it from the counterweight station. Most of the trip does not go through any atmosphere so there would be very little loss or diffraction once the climber goes above the densest portion. The climber could also receive power for the first part of the journey from a ground based system. The counterweight station could be powered by solar panels or a nuclear reactor. During initial construction, the carbon nano tube filaments should be manufactured in orbit and then lowered as it is made. Once the first elevator is made, any others would be much cheaper and easier to construct.
But if the cable were to be made out of carbon nantubes, and carbon nantubes turn out to be room temperature super conductors, that'd solve two problems at once. lots of ifs though.
@@IamGrimalkin Who needs room temperature superconductors? They just need to beat 36,000km of inevitably imperfectly focused laser. @Muh Face The temperature would vary depending on whether they're in the shadow of the Earth or directly exposed to sunlight, and even then not necessarily very hot depending on the specific properties that nanotubes in macroscopic structures wind up having (e.g. if able to be constructed with highly reflective surfaces they could stay cool even in direct sunlight).
Oddly enough that would be useful for observation purposes or it may make a gravitational slingshot a lot more controllable by making the distance from the planet rather precise so you might be able to calculate the exact power of the maneuver
When people quote the cost of sending something up a space elevator, they are only referring to the incremental cost. What EVERYONE neglects to talk about is the cost to put the tether in space. It won't be free, nor do I think it would even be possible and the cost would have to be amortized over all subsequent lifts.
Reading through the comments (well, the first few hundred at least!), I am reminded of two science fiction stories - but can't remember the title or author of either of them!! One is about a building which is being built to reach the sky and the lives of people building it and living on the various levels. It's fantasy, obviously, but it still illustrates wonderfully the size such a building would have to be and the distances and time involved in moving up and down it. (Spolier alert - they do actually reach the sky - and then break through it!) The other story I only have the faintest memory of, but I think in that one a space elevator (there might have been more than one) has lost its cable, which is now coiled all over the ground. When the people in the story find this cable (which is very thin, but supremely strong) they discover (the hard way) that it can cut through almost anything. If anyone reading this knows these stories please tell me! Ta.
The first story is probably "The Tower of Babel" by Philip Chiang. It's actually biblical science fiction, written as though someone from the late bronze age would write, with their understanding of cosmology. One of my favourites! The second story is probably "Ringworld" By Larry Niven, where they come across one of the broken cables whioch held up the shadow squares which, in the Ringworld, were used to create an artificial nicht and day sequence. The cables are very strong but obviously not unbreakable because it's lying there because it got broken! Maybe you should start to take notes when you read...
A few other important points: - The most practical way to power the elevator is to have large fuel tanks that get jettisoned, just like for a rocket, rather than using lasers. - If we're already assuming we can produce a graphene cable strong enough for a practical space elevator, we might as well assume we can pair it with a superconducting cable for power. - The minimal space elevator is far from getting things to orbit, as it doesn't directly impart velocity. - It would have to be much longer to allow things to accelerate via centrifugal force, and to gain more gravitational potential. - Vibrations along the cable and micro-meteorites are not to be underestimated. - Rockets are surprisingly efficient (around 10% for some orbits?). Given the huge upfront cost of space elevators, the long travel time, etc, it will take a while before they get competitive.
Yes, it is. It's fictitious. Sure, it seems real in a rotating frame of reference, but if you were to release the object from your tether It would not continue to travel in the direction of what seemed like a force, the object will fly tangentially not radially.
@@sebastiaomendonca1477 Engineers and Physicists have some disagreements on terminology. Physicists characterize everything to get a deeper understanding of reality while Engineers just need things to work, so they are often times intentionally ignorant of the underlying ideology of their language. Here's a good video from a Physicist's perspective. th-cam.com/video/zHpAifN_2Sw/w-d-xo.html
@@sebastiaomendonca1477 ye u'r an engineer too ;D They just need things to work. And it does work mathematically as a force. To a Physicist even Gravity is a fictitious force caused by spacetime curvature. It's a funny world.
3:45 I'm pretty sure that increasing the mass doesn't help solve the problem. True, the centrifugal force increases, but because gravity is w=m*g, the centripetal force increases as well. Because at the Clarke belt, the weight is equal to the centrifugal force, both scale by the same factor and there's still no room to add the tension by the tether. If the satellite is slightly beyond the Clarke belt, however, then increasing the mass still causes proportional increases in both radial forces, but because the slight difference to begin with, the absolute difference actually grows. Basically, increasing the mass can't compensate for adding a tether without being accompanied by a increase in altitude. I suspect that a captured asteroid is suggested as a possible counterweight because having such a high mass would cause the tension to be trivial compared to the high centripetal and centrifugal forces.
I would love for you to revisit this particular topic again I think the engineering would be quite intriguing if you include resistance of our atmosphere.
Well, it looks like multiwalled nanotubes are good electrical conductors, so the power problem is solved, just make 2 long cables out of carbon nanotubes around 1-2 meters apart and put the lifter between them, set up a few thousand volts potential difference between the cables and have the lifter run an electric motor from that. Ok, I know, the exact resistance of the cables will be critical, but also the gravitational force decreases with height, so you will need less current as you go up.
There is a small but significant thing I believe you may have overlooked. While discussing the taper ratio you mentioned how the line (at minimum) must support its own weight. To my knowledge you did not factor the weight of the tether into your calculations for the distance of geostationary orbit. I went and used the small scale carbon nanotube ultimate tensile strength and calculated the weight of the strand to be on the order of 1000's of tons (I used calculus to integrate the mass with respect to radius from the earth to find its actual weight not just its surface weight), which drastically affects the needed centripetal force to sustain orbit. This doesn't affect your conclusions at all, and if anything strengthens your argument, but it's an interesting and really fun problem.
The last paper had an assumption that the space elevator must be stationary, which is why they pick R_g to be geosynchronous radius. Technically the counter weight just need to maintain constant altitude, it does not need be geosynchronous. So technically R_g could be at any value, as long as the counter weight orbital velocity is sufficient to counteract gravity and we don't mind the elevator to not geosynchronous. If we shuffle the taper ratio equation in the last paper for a bit, we can estimate it as Ln(taper_ratio) ~= C * 1/(R_g^3). Which mean even use the worst example of steel, there would be no taper require if the R_g is roughly 3.2 times longer than geosynchronous orbit altitude. It seems way more feasible to just have 3.2 * R_gsync length of tether than a tether that taper to 10^33 times at the end. Assuming 14 gauge wire, at 3.2 * R_gsync length would roughly take 0.07 % of 2018 global steel production. It's pretty big amount but it's not an impossible amount. Certain Olympic stadium construction consume way more steel than that. But then this design would require the "tower" to be drifting at some velocity to compensate for the non-geosynchronous-ness. Nothing mention all the additional drag, vibration mode, increase travel time and a whole host of other issues. I guess you could have multiple counter weight satellites "baton pass" the tether between each other in order to let tether remain stationary. Or have some sort of mini-planetary-ring-world like counter weight to let the tether remain stationary.
![MV วิถีชีวิตใต้ - ผา อัยย๊ะ [Official MV HD]](http://i.ytimg.com/vi/nODlkOUu9B0/mqdefault.jpg)
"every engineer ever has waited their entire lives for a problem where the solution was a gigantic laser" - Truth.
Not me!😂
I was thinking about this, and was wondering if gravitational wave detectors count as the biggest lasers we have ever built.
@@CupCakeArmy1
RE: "I was thinking about this, and was wondering if gravitational wave detectors count as the biggest lasers we have ever built."
The Laser Interferometer Gravitational-Wave Observatory (LIGO) is a large-scale physics experiment and observatory to detect cosmic gravitational waves and to develop gravitational-wave observations as an astronomical tool. Two large observatories were built in the United States with the aim of detecting gravitational waves by laser interferometry. These can detect a change in the 4 km mirror spacing of less than a ten-thousandth the charge diameter of a proton. These lasers were built for sensitivity not power.
The most powerful laser beam ever created has been recently fired at Osaka University in Japan, where the Laser for Fast Ignition Experiments (LFEX) has been boosted to produce a beam with a peak power of 2,000 trillion watts - two petawatts - for an incredibly short duration, approximately a trillionth of a second or one picosecond.
References:
en.wikipedia.org/wiki/LIGO
www.ligo.caltech.edu/page/what-is-ligo
theconversation.com/worlds-most-powerful-laser-is-2-000-trillion-watts-but-whats-it-for-45891#:~:text=The%20most%20powerful%20laser%20beam,trillionth%20of%20a%20second%20or
www.sciencemag.org/news/2018/01/physicists-are-planning-build-lasers-so-powerful-they-could-rip-apart-empty-space
Material for the lanyard /elevator cable needs resistance to burning up in the atmosphere for every minute, second, days and years.
Satellite laser tracking engineers are living the dream
"Eleven-" - Oh, OK. Ain't much.
"…thousand…" - Kilometers? OK, it's over.
"…times…" - Oh, just a ratio? Maybe possible afterall?
"…the size of the observable universe" - wat.
Best
well for a space elevator, you need a station at 35.786 km height. So you would need to travel 35.700 km. to put that in relation, the ISS is only 400-440km high. That's a pretty long elevator.
The use of decimals threw me off for a moment.
Use a truss 50 feet wide or so.
well if we did manage to build a cable made of steel (obviously not)...aliens would have no problem locating our position and coming over to say hi. Alien: "Oh we just saw this huge arrow pointing to earth".
that will be the longest elevator music ever played if this ever gets built.
Earth's way of saying goodbye 👋
There's also the problem of shorting the ionosphere to ground.
Basically a carbon lightning rod.
"unlimited power" in evil voice
That's not a problem, it's a solution! Use that current to power the climber!
I really love how you say, "we are going to design a space elevator." Like we are a part of this with you.
I think we should build a space escalator instead, for those of us who
are claustrophobic. Plus, if it broke down, you could still use it,
because it'd be space stairs.
Hey, yeah! We should just build a set of spiraling stairs up to the Clarke belt! Just make sure everyone holds onto the handrails and wears a spacesuit... :)
How does this seems so stupid but extremely smart at the same time
Don't skip leg day
@@maxbuskirk5302 Just don't look down.
Imagine if you trip and you just keep falling through the staircase all the way down, hitting all thousands of stairs.
@@TempSlothy True, I thought this comment was idiotic but also sounds smart at the same time.
**Plays space engineers**
"You know, I'm something of a scientist myself."
Clang says otherwise
“I’m not a space engineer, but I’ve played one in a game”
“I’m not a space engineer, but I’ve played one in a game”
THANK YOU for using the terms centripetal & centrifugal correctly and using simple honest reasonable explanations to explain the physics involved!
It's nice to see someone break down the math into something readily understandable.
He didn't breakdown the math lol. Vector calculus is not fun
I cant believe its been almost 4 years since ive started following your channel. And how little ive done with my life since then
Now it has been 6 years ... did you finally do something?
@@AkaRyrye83 my ex girlfriend lol and I got promoted
"Every engeneer ever has waited their entire life for a problem where the solution was a gigantic laser"
That line, my friend, is one of the best line ever written or thought of ! ! Great job ! !
Here me out...
Gigantic,
Space,
*LADDER*
No power source needed.
what about starving to death?
just carry the food for a 1 year climb, what's the big deal?
@ Carrying the 35 tonnes worth of calorie dense food on your back for your life long journey.
@AlexNOSAM thicc ladder
@@OhSeeBarber you are THICC
I’m so grateful for your videos! I’ve always struggled understanding math and science but your videos make it so much easier to get a basic grasp on. Thank you!!
Megan Pham I appreciate this video too-you can tell he knows what he’s talking about because he doesn’t hide behind a lot of technical jargon. Also: he uses the terms “centripetal” & “centrifugal” correctly and explains the consequences of those forces correctly, which is a level of detail I don’t often see in videos about space elevators
I just want to say I really appreciate a guy of your intelligence and knowledge breaking these incredibly complex topics down and making them digestible for laypeople. For me at least, it really helps me see where I want to invest my time learning more about something.
I stumbled across your channel today and am hooked! I've been binge watching for a couple of hours and I am so so intrigued. Keep these fantastic videos coming!
Sorry to nit pick again, but in the paper you link regarding taper ratio, it actually defines taper ration as the ratio of cross-sectional areas. not diameter. Your estimate of the resulting diameters should actually be the square root of what you state.
A 1 cm diameter steel cable would have to be 4e14 meters at GEO (about 1 ligthfortnight ;)
A 1 cm diameter kevlar cable would have to be ~160 meters at GEO
Better not mention that a similar calculation done by someone (not me) who is familiar with the mechanics of elevators puts the diameter at the top as something like 2Km for a steel cable.
That's the thing with physics - no matter how much you know or how good you are at the math its still horribly easy to get something wrong. The tiniest misstep like forgetting to factor in reducing gravity with height tends to make all the difference. The gravity at the orbital geo-lock point is of course zero by definition.. :)
I'd love to see him respond to this.
"lightfortnight"
#respect
@@Lucien86 Bzzzzt!!!
Nope, it's just balanced by centrifugal force.
My previous post says the top of the cable, its widest point is not there but somewhere at a midpoint. The reason that a steel cable ends up at anything like 2 Km wide in the middle is that 50,000 Km is very very very long for a steel cable.
That's why I'm a bigger fan of the rotational space elevator. Have a cable only about 1850 km long as opposed to 60,000 km.
What you do is have the shorter cable in orbit and rotating such that the end closer to the Earth is moving slower than the top. The Ship flies up at less than half orbital speed, grabs on, and rides the cable until it is at the top and lets go.
This does impact the orbit of the elevator but this can be contradicted by having ships make the return trip using the elevator. This also negates the need for a heat shield.
The advantages are that the cable can be made from carbon fiber and the system does not require a climber.
Above the atmosphere is fine with me.
Are you advocating for a thing dragging a cable through all the circumference of Earth, at surface level with all its irregularities, mountains and seas, natural reserves, cities and what-not (yes, there are several cities located right at the Equator too). I think the UN Security Council would not approve...
My story about the Space Elevator was published under my previous married name in 2005. I was thrilled. Arthur C. Clarke and Ray Bradbury were sponsors and the main impetus behind the contest was Bradley Edwards. I lost my only copy of "Running the Line: Stories of the Space Elevator."
(Divorce and ex sold my books 😭 as he is a very mean thing). I caught him, but only got a little of my books. Anyway, I was inspired by the idea of a Space Elevator.
"Civil engineering is the best kind of engineering". pfft
Awesome video! one of my favorites :)
+jamdram ;)
+jamdram How...
Uncivilized
+Practical Engineering Thought you were a mechanical engineer looking at your other videos!
Mechanical is where it's at. We'll let him indulge in his delusions though ;)
Road networks, powerplants and sewage systems are nothing to laugh at. You owe most of your modern comforts to civil engineers.
You are doing a great job bringing all of this materials to us that were once only for civil engineers. The way you present it makes it easy to understand. I work in electronics and have never been so interested in physics until I saw your channel. Keep on that track and definitely more and more people will come along to discover the fascinating world of physics.
The main problem with any Space Elevator design, which I've never seen addressed on TH-cam (although it has been discussed in other forums), is something you and almost everyone else is overlooking.It's not cable strength, or the weight it must hold.It's not how to power the lifter.The problem is that the tether could not possibly stand up to even a fraction of the electrical discharge it would carry as it passed through multiple plasma double-layers. It would essentially be like placing a conductor across the leads of a planet-sized capacitor. In the unlikely event it ever made it to the ground, it would disappear in a blinding flash of mega-lighting.
it may even be like a thermo couple with diff chartges tempatatures build up voltages along the line.
Hey Grady,
Loving the direction of the channel so far. There's lots of science-y channels out there, but most keep it simple or avoid equations. I loved the "100 year flood" video precisely because you didn't shy away from the technicalities, and you touched on an uncommon topic; hydrology. I hope you won't be dumbing down future videos in favour of more views, I've come to find a lot of people are tired of the old pop-science format and are turning to channels such as yours and Ben's "Applied Science Channel" for content that intrigues and challenges them. Ben's got some very technical videos, yet his community is quite diverse and full of both professionals and laypeople.
I know your hydrology video inspired an entire week of reading up on fluid mechanics and geology in my case! Same goes for this video: before I knew it, I was scrolling through my university's e-catalogue for books on the topic. I love it when youtube videos are capable of doing that, and I'm really glad I stumbled across your channel.
Best of luck to you, and keep it up.
+Luka P Thanks, this is really kind. I am doing my best to strike a balance between good technical content and general tedium. My goal for the channel is to increase exposure to the field of engineering and make it more approachable, so that comes with some simplification of the content. Hopefully not too much though!
"Approximately France"... awesome. lol
I love the quality of your videos lately, keep up the amazing work and can't wait for more :*
This was an amazing video. Yes, I've heard all the tv talkers say how wonderful it would be, but you really put the construction into perspective. Thank you.
The space elevator? My childhood imagination since the space and stars fascinates me. i've been watching your vlogs. I love it.
4:29 You know it is getting serious when you bring wolfram alpha into it.
One method to make friggin' lasers a feasible power delivery method is to split up the workload.
Instead of having only a ground based laser, beaming up to the lift, have an extra one at the anchor, beaming down to the lift. Once the lift passes the point where the energy from the ground based laser becomes marginal, the top one becomes the primary deliverer. The top one also doesn't have to deal with atmospheric disturbances, giving it a larger effective range. As for how to power the top laser? The anchor needs to be heavy, right? Sounds like the perfect excuse to plant a large solar array up there.
Excellent plan, but you'd probably want either a nuclear reactor or hydrogen batteries up there as well. So your elevator doesn't stop/fall out of the sky at night.
I sort of like this idea, but the Solar implementation at the top looses me, as well as the break point for the laser.
Starting with the laser break point(meaning the point where the elevator switches from Earth to the "space laser"). That specific point, would have to be almost outside the atmosphere to be really just economic enough to implement. Reason being, we would want the "space laser" to(as you also say) avoid distortion to get us up there the rest of the way, but also the break(or switch over) point would mean that there would have to be some power compensation(because of the "Earth laser's" distortion) before we reached the breaking point. That would also mean added weight to the lift, because(with current technology) circuitry involved to make a regulator which could handle the power load for that lift, would only add more weight causing yet again a power vs weight challenge.
The idea of putting a solar array at the top, again involves the idea of both electrical power vs weight. A decent enough solar array capable of producing that kind of power to push a laser that pushes a cart up a cable, in addition to the to the distortion of the "space laser"(yes it still has some distortion in space, just not nearly as much as it would going through the atmosphere), would mean that you would need a LOT of panels to create that decent load. A lot of solar panels means a lot of flat usable space, which can be very hard to achieve especially when the counterweight needs to be certain mass which might not mean enough space for panels, in a realistic format.
And who says that it can only be one energy source. Why not eletrcal power from a wire to start and then a boost from a reusable rocket finished off with the Lazer from the top powered by a solar array. Then on the return Lazer to gravity.
In addition to the other answers, I would like to point out the havoc such a laser would cause on earth, were it to ever miss the panel (and part of the beam WILL miss, laser beams are not perfecty homogeneous tubes of light even in vacuum)
The problem is that you don't need power at the top: you get free acceleration from centripetal force.
"Approximately France" Can't wait to figure out a situation to use this in.
Meaning: when you get 1,000 miles away from the station it'll surrender.
Grady, that was cool seeing a glimpse of you on one of your real life projects. I'm sure many of us engineers of other disciplines would love to hear about your work and maybe a little about a real project you are doing or have done.
This is so cool, these are things I've been wondering about space elevators forever, but nobody ever seems to talk about it. Thank you ^-^
Thanks for including the Formulas!! we have enough dumbed down science videos.
The animations are really good (even if they are without a sexy accent).
+Amar Gandhi If anything, a german accent would go better with a video like this. Maybe he can fake one next video!
CheeseWithMold No...a good Russian accent...."we build for mother Russia commrade".
yeah ;) way to put yourself down...from one pale whiteboi to another
Let's get realistic - a Chinese accent would, at least, be believable.
I got stuck on the space elevator once. Good thing they gave us emergency parachutes and propulsion packs so that I could safely descend all 7320 stories back to Earth.
Except you died before you could get to breathable atmosphere.
Your clarity is compelling. Thank you.
Another suggestion for improving the nanotube space elevator design: Wrap the cable in superconductive tape and put a circular current around the cables. They will produce a magnetic field along the length of the wires, so if they ever got broken by (say) an asteroid, the 2 ends of the cable would pull back together again like the 2 ends of a broken bar magnet. There is some evidence that nanotubes could be superconductive at room temperatures, so maybe we can put a current inside the cables themselves. A few million amps per meter should be enough. The field lines being mostly inside the cables and the direction being along the length of the cables, this wouldn’t stress the pods travelling up or down the cables.
Thank you. A video with real maths and not just theories.
this entire video is nothing but a theory lol
Ironically on "practical engineering" smh
In my final exam in physics, most excersises dealt with the space elevator. Wish I had seen this video sooner..
(still aced that exam)
Dear Grady, you actually revealed the engineering of the sky elevator, I thanks you a lot for such beautiful revealing the engineering connection of sky elevator , stay bless, thanks
"Obviously I can't show you a full sized space elevator, so I built a miniature, fully functional space elevator in my garage."
Such a great explanation! I love seeing just enough equations and graphs. It makes me remember fondly of college.
“The wonders of calculus”
How about alternatives like a space fountain or launch loop?
They can be built tomorrow, but channels like these don't like practical solution for futurism problems. For something more down-to-earth, go to Isaac Arthur's channel and watch the videos about spaced towers and power satellites.
(And yes, I do realize most of his video are about interplanetary and space stuff, when I said he's down to earth. Bad pun intended.)
Or Catapult?
@@Broockle massive cannon is not actually the worst idea
@@NathanK97 It is the moment you experience neckbreaking G forces when the canon fires due to acceleration
At the ground you can just use the local power grid. We can send power 1000km with copper. Nanotubes and graphene shouldn't lose much of the power.
That's still gonna be one tall as fucking power grid. Also you still need God beam for enough laser to pass through all that atmosphere high up.
We need Tony starks arc reactor tbh
Don't beat down om your voice, it's very relaxing. Also, "using the wonders of calculus" is probably the funniest thing I've heard all day
This is hands-down the best video on space elevators I've ever seen. Sorry, Kurzgesagt.
"using the wonders of calculus" that one goes straight to the quotation goldmine xD
Could you use the tether as an extension cord? Basically sending power through that material? It would work kind of like a street car except vertical :P
I think the problem is the loss of energy because of the lenght of the cable, the material's resistance i think it is
carbon nanotube is basically a superconductor. we could use the tethers travel through the atmosphere (friction) to generate electrical current.
the climber could theoretically just draw power straight from the cable as it climbs, provided the structure used to grip the tether is conductive as well.
What are the carbon nanotube properties, couln't we build all from nanotubes ? I speculate it will be the most expensive material.
In order to have an electric circuit, you need two conductors, and thus two cables. And since they'd be whipping around in the atmosphere, they'd short out whenever they touched each other.
Hungry Guy
not entirely true. you have one circuit, negative/ground at the base, positive end at the orbiting mass.
the cable itself just allows flow, then the climber as two sets of grippers, negative and positive, basically just making a mobile flow gate with attached motor/control center.
I can't believe you didn't mention Arthur C. Clarke! You even mentioned the "Clarke Belt", but you didn't mention his novel "The Fountains of Paradise", which popularized the concept of the Space Elevator!
TO: Alvaro S.
There's also Arthur C. Clarke's novel 3001: The Final Odyssey, which goes into great detail about a space elevator. He describes an Earth which has four space elevators that connect to an inhabited ring around the planet. The towers containing the cables are inhabited as well.
@@spaceman081447 I have that novel, too. You can call me a fan of Clarke's 🙂
The tone and content of this video is a good demonstration of why I subscribe to this channel even though I'm not an engineer. Oh, and I think you have charm and are handsome. :)
The 1st thing is the climber, aka elevator. Batteries are becoming stronger and stronger with longer life times. By the time this could be developed, batteries just might be the solution to the power to get to station. As many batteries are rechargeable, we use the same principle that is used in electric cars. Applying the brakes feeds power back to the batteries. By the time the elevator got back to ground, it would be close to a full charge.
I first read of this concept in a book by Arthur C. Clarke, "The Fountains of Paradise." They used 4 cables made of a super strong light weight material. The car rode up and down these cables using wheels with friction brakes. This isn't that different that how some elevators currently work. The story also has another story, or 2. I highly recommend this. As you noted, we are getting some materials that just might have the strength to begin giving this idea serious consideration.
its just like jack and the beanstalk. its do-able.
+Albion Laster That's the attitude!
+Albion Laster lol
+Practical Engineering Hey, just a nitpick, but at 2:18 you say "force of gravity", but show the equation for acceleration due to gravity, the term gotten when canceling out the little m's. Not a big mistake, just wanted to make sure you knew it was there!
+Matteo Mcdonnell Yeah I played a bit loose with terminology since the mass term cancels out in both equations. I take a bit of liberty with the rigor because I know no one's relying on me as a primary source for engineering education.
Of course! I really value what you are doing, man. I love every bit of your videos.
If the tether snaps, would it wrap around the earth and kill everyone?
+Berrymouse only one way to find out!
Fight?
Depends on where it snaps.
Watch Gundam 00.
that was my first thought as well.
Why didn't you talk about space elevators on smaller solar system bodies. I know there has been talk about having the first space elevator be on the moon, because the lower mass/gravity means you don't need as strong of a tether that also wouldn't need to be as long, and the barely-there atmosphere of the moon wouldn't impede a power beaming system anywhere near as much. We would then take the infrastructure and what we learned from building the moon space elevator to work toward an Earth space elevator.
what practical purpose could a lunar moon elevator serve? The experience of building it would hardly justify the absurd expense, especially considering it would do little to simplify the construction of one on earth since the fundamental material demands would be so different. All the equipment and materials would first have to be flown to the moon, an enomous and unprecedented endeavor of itself
+charlesissleepy It would make sustaining a lunar base way cheaper over the long run, especially if you consider wanting to bring lunar material back to Earth in mass. I think you also underestimate how beneficial having a stepping stone to an Earth space elevator would be. Even if none of the developed technology crossed over (which is a bit of a ludicrous proposition), just from a fiscal standpoint of fundraising (particularly in the current socioeconomic climate), it is a far more likely path to actually get off the drawing boards than building an Earth space elevator first. Building a lunar space elevator offers far less risk, while still offering substantial reward if successful. And it is far more likely that whatever technologies, processes, and manufacturing techniques that were developed for a lunar space elevator, would almost certainly directly lead into what would be used for an Earth space elevator.
A lunar space elevator presents a very distinct set of engineering challenges.The moon has inadequate rotation to permit the construction of a space elevator of the same working principle as an earthling one and would have to use lagrange points instead. This means the tether would have to be considerably longer than on earth, 56,000 km on the earthfacing side. The lower mass and lack of atmosphere permit the use of a uniform diameter tether made of existing engineering materials, which clearly already sets it apart from on earth based design (and no research into CNT in massive scale). The tether itself would be massive (using the length and proposed cross section area of the ribbon i figure around 66 metric tons, very likely i bungled the math though) and very expensive both to produce and to convey into lunar orbit. All without much economic motivation, save perhaps He-3. Long-short I don't see it preceding an earth-based project, since any practical use it might have almost presupposes one on earth.
Since the Moon is tidally locked with one face permanently facing Earth, the only place where one would work would be on the far side of the Moon where any kind of centrifugal force would be found. Taking that into account, it wouldn't make much sense taking material to the Moon, landing it from orbit and then lifting the same material out of the Moon's gravity well up to a point where we could reach by simply extending the lunar orbital eccentricity to the point of meeting the same point in space where the counterweight would be. If you are looking for an economical, efficent and faster means of getting to any of the Lagrange points, it would make more sense to use the Moon for a slight slingshot boost to get you there.
Now if you are looking for a means to move stuff to the lunar surface, then you may have a point. But for the counterweight to overcome the gravitational pull on it and the mass of the tether, the counterweight would have to be much much closer to Earth for Earth's gravitational force to pull on it with sufficient force to overcome all that lunar weight. I'm not sure what the math would work out to for all of this, but I could see it being done. One of the advantages of having the Earth's space lift's counterweight being beyond the Clarke Belt is that spacecraft launched from the counterweight would be able to put all that centrifugal force to use by merely undocking and being slung into space! It would be interesting to see if and how all that would work, essentially using minimal energy to move materials to the Lunar surface by this means.
Since the Moon is tidally locked with one face permanently facing Earth, the only place where one would work would be on the far side of the Moon where any kind of centrifugal force would be found. Taking that into account, it wouldn't make much sense taking material to the Moon, landing it from orbit and then lifting the same material out of the Moon's gravity well up to a point where we could reach by simply extending the lunar orbital eccentricity to the point of meeting the same point in space where the counterweight would be. If you are looking for an economical, efficent and faster means of getting to any of the Lagrange points, it would make more sense to use the Moon for a slight slingshot boost to get you there.
Now if you are looking for a means to move stuff to the lunar surface, then you may have a point. But for the counterweight to overcome the gravitational pull on it and the mass of the tether, the counterweight would have to be much much closer to Earth for Earth's gravitational force to pull on it with sufficient force to overcome all that lunar weight. I'm not sure what the math would work out to for all of this, but I could see it being done. One of the advantages of having the Earth's space lift's counterweight being beyond the Clarke Belt is that spacecraft launched from the counterweight would be able to put all that centrifugal force to use by merely undocking and being slung into space! It would be interesting to see if and how all that would work, essentially using minimal energy to move materials to the Lunar surface by this means.
Kurtzgesagt isnt bad. They just made videos for basic understanding and to encourage scientific thoughts
The biggest problem in my mind is how the heck we actually string up that cable. We would almost need anti gravity technology just to feasibly connect it, in which case we don't need the elevator. The best way I can think is lowering it from geostationary orbit to the earth, in which case we need to take unspeakable amounts of the most expensive stuff ever to high orbit. Anyone thought of what would happen if space junk or debris hit any part of that thing? What about being a terrorism target? What if it broke and literally fell from orbit slamming into everything and wrapping around the earth? What about trying to make such a long, continuous piece of material without breaking it down into smaller pieces to keep it strong. It is molecular in its connection.
why not just integrate a conductive surface into the wire and use that to power it?
Too long for regular wiring. It's the same reason power plants are spread out instead of all being in one place, cause you lose energy over longer distances. You could assume that room-temperature superconductors have been figured out as well as nanotubes, but even in that case, if each metre was only 10 grams, that's still thousands of tons, and then that old taper gets you again.
Is that true in a vacuum though? I thought the reason you lost power over distance was the wind stealing ions?
@@kahlzun It's resistance.
It needs to be a super conductor to not lose a lot of power from resistance. Or a lot of small energy sources along the cable, which would increase the weight.
What about a lunar elevator? No atmosphere weaker gravity, and a shorter Clark belt?
I thought you meant between the earth and the moon😂😂
Exactly, its "easy" to get in orbit from the Moon's surface. The problem is here on Earth.
Everyone knows that electrical/electronic/control engineering is the best kind of engineering.
industrial?!
No, everyone knows that EE's work with magic and that we just have to take your word for it. Trust me, we're on to you guys.
define ''best''
Have been a space elevator head for some time now. Thanks for tackling this :) I learned a few new things in just ten minutes.
Great video mate! I watched some other videos on this topic before but I didn't get bored and learned something new.
Why is nuclear power not an option for the carrier? Wouldnt a mini nuclear reactor like the ones user on submarines produce far more power than a laserbeam?
That's what I was thinking, imagine fusion ;) probably do the trick
+Bonta kun hmmmm fair point, obvs not with fusion but that's a long shot anyway isn't it ;) I still think it would be an option, it would be the best looked after reactor on the planet and short of the whole thing falling down I can't see why shit would hit the fan especially with the modern quality of reactors
+Bonta kun and maybe the craft could have a very lightweight payload? One that could be easily ejected if a problem occured? I mean although a lot of energy would be needed it wouldn't need to be like a full city reactor would it? I don't know how much the thing would weight
Hmmm well true just thinking about efficiency. I mean you get nuclear subs but maybe you're right and it wouldnt be worth the efficiency benefit for the huge weight. Still and interesting thought though ;) To be honest I would bet fusion is perfected before graphene but then again without graphene what would we build the thing out of in the first place! ahaha
Well, we already use small fission reactors on some satellites (probes actually) which are very light. And fusion is probably much closer than large scale nanotubes.
Why not send the power through the tether? Just have charging stations every X kilometers
Pretty sure that is what he is referring to when he talks about extension cords (ie well due to resistance and such you wont have enough power left long before you reach even a quarter of the way)
@@GummieI Why not have a generator on the elevator? Not sure how feasible that is with how much fuel you would need but that is what immediately came to my mind
@Robert Ibey I am by no means an expert on this topic but generators are HEAVY, VERY HEAVY, I don't think most generators output enough power to lift themselves in the first place.
Beside that generators still do need some kind of fuel to generate power in the first place, so what would said generator use as fuel? Wind? Well there are no wind when the elevator is in the space part of it, or maybe its just a day without any wind. Solar panels, what about on the earth part of the elevator journey and a cloudy day?
Gummiel u right
@@GummieI We can build fuel-based generators that can lift themselves off the ground WITHOUT needing a cable to climb, so this should definitely be doable.
"Centrafugal Force..."
okay , I can hear the Angry Comments already
I enjoyed this overview. This is apparently becoming a hot topic. I remember reading Arthur C. Clarke's book on the subject (yes, the same Clarke as the name for the geosynchronus orbit band), "The Fountains of Paradise". A couple of questions, First, I agree with Einar Gissurarson about having an SPS attached to the counterweight and splitting the power load. Why not make the tether conductive and use it to power the climber? Also, the counterweight could be quit far from the Clarke band so we could use it as a cheap method to launch Solar System ships.
Also, I have read of two other methods for a space elevator. Clarke listed one in a different book (I think "The City and the Stars") which used a rotating tether/weight system so you wouldn't need a climber. I think Neil Stephanson used it in "Seveneves" as well. And Dr. Robert L. Forward wrote about a fountain of rings in Starquake. All of these have their own problems in terms of currently impossible engineering challenges.
I think the largest challenge however is overcoming the character of the human race. We've seen just this century on the internet how something that can be massively useful gets abused or destroyed by a few individuals who want to smash things to see them smash, or to give them a short-term advantage, or to destroy the creators because of jealousy, spite or perversity. We're about to see it happened again, IMHO with the Internet Of Things (IOT) since the engineers continue to insist that because it's so useful, no one will want to misuse it.
Again, I liked the explanation, it was concise and not difficult to follow.
Isaac Arthur's channel does such a thorough job at describing this in several of his vids. 👍👍
you should check out the channel science and futurism with Isaac Arthur. he's got a couple of really good videos on this topic and many videos on related stuff. I'd love to see a collaboration between you two on something.
Whatever they do, "practical engineering" would do his most theoretical work, and Isaac Arthur would do his most practical. :P
Why not send the power through the cables themselves? Nano-tubes are conductive are they not?
Resistance grows with distance. So no.
@@3gunslingers Sure, but there could be small stations on the tether to help pass the electricity along.
@@Hallowed_Ground
How does that work?
And why not put a small nuclear power station directly on the cabin?
arxiv.org/ftp/arxiv/papers/1802/1802.07443.pdf
@@3gunslingers this. i scrolled so long to see someone suggest nuclear cabin. we have it in US Subs already. A micro reactor would provide all the power needed.
The problem with that would be that the electricity would just flow PAST the climber, as the tether needs to go past it uninterrupted. Also with a single cable you wouldn't have a closed loop for the current. So you'd need to use two cables that need to be insulated from each other. Either you'd get power from current that you let pass from one cable to the other, or one of the cables is a guiding cable and the other one is a pulling cable that you just reel in from the top. Which would mean that you'd need to accelerate 1000 cubic meters of carbon nanofibers per square centimeter of cable cross section at the climber. Or you could just send the current past the climber and transfer power by induction. You'd still need two cables in close proximity to in order to shield any stray fields , because else you'd have the biggest wireless power transmission antenna ever conceived.
@Keyboard runner Having a nuclear reactor next to a structure that could wipe out a whole county if it would break due to ratiation damage does not sound smart. But a space elevator is such a crazy concept that that might actually be the smartest solution... After all, you only need radiation shielding on the side with the cable and passengers.
How about we attach a rocket to the climber! =P
Or a Nuclear Reactor ...
How about we attach a rocket to a flying machine that will get into orbi-... wait a minute...
Kinda defeats the purpose my guy
Yeah but you lose the risk of dying if your rockets fail
What's the point then using the elevator when all are you using is rockets
Great video. The "approximately france" graphic at 7:41 had me in stitches!
First, a geosynchronous orbit radius is necessary only for daily orbit periods. Shorter orbit radii are possible, but only for elevators tethered to rotational poles. Second, electric conductors embedded into the cable(s) can charge supercapacitors (or batteries) spaced periodically in the cable to serve as "filling stations" to refresh an energy cell in the elevator. A descending elevator releases energy which can be captured in reversible motor/generator, recharge the cable's cells, and power the electric grid until another ascent is needed.
Loving the misspelling of Clarke
Whoops!
+Practical Engineering but your good at math so that's good :) Awesome video's and yes Civil engineering = awesome!
Mechanical engineering > Civil engineering
there is a simple answer: magic
Or we can add a fuel line and reusable thrusters to counter the weight of the elevator
Whats the point then? You need to power the elevator not the counterweight
What most people fail to realise about space elevators is that we don't need a fantastic supermaterial strong enough to hold the tension of the whole thing. We could use an active power structure instead, so it holds itself up with energy instead of strength. It's called a "space fountain". We could use this for super-long single-span bridges too. Grady really should check out active power structures!
The space fountain also eliminates the power beaming problem, because you're already sending power up the entire thing in a near-vacuum (so no atmospheric losses). The question is whether we could lower the friction of the system enough to keep the energy costs low enough to be worthwhile.
Awesome video for those of us who are interested in more engineering and mathematical details for a given topic!
Why would we even bother having a separate powering system when carbon nanotubes are conductive?
Then you need two tethers for the circuit?
Well, first solve the problem of the cable and then think about the energy issue, which seems complicated enough but maybe less absolutely impossible.
bruh... you're handsome enough. don't sell yourself short.
I’m still waiting for the space escalator
This was very nicely done. I'm glad I found your channel and look forward to more.
An easy solution to beaming power to the climber is to beam it from the counterweight station. Most of the trip does not go through any atmosphere so there would be very little loss or diffraction once the climber goes above the densest portion. The climber could also receive power for the first part of the journey from a ground based system. The counterweight station could be powered by solar panels or a nuclear reactor. During initial construction, the carbon nano tube filaments should be manufactured in orbit and then lowered as it is made. Once the first elevator is made, any others would be much cheaper and easier to construct.
But if the cable were to be made out of carbon nantubes, and carbon nantubes turn out to be room temperature super conductors, that'd solve two problems at once. lots of ifs though.
Carbon nanotubes have been produced, just not in bulk. They aren't room temperature superconductors.
*_what about when they are cold_*
sure not room temperature. but what about space temperature
They would be very hot heated by the sun.
@@IamGrimalkin Who needs room temperature superconductors? They just need to beat 36,000km of inevitably imperfectly focused laser.
@Muh Face The temperature would vary depending on whether they're in the shadow of the Earth or directly exposed to sunlight, and even then not necessarily very hot depending on the specific properties that nanotubes in macroscopic structures wind up having (e.g. if able to be constructed with highly reflective surfaces they could stay cool even in direct sunlight).
You could build a space elevator out of kevlar on the moon...
?
?
Oddly enough that would be useful for observation purposes or it may make a gravitational slingshot a lot more controllable by making the distance from the planet rather precise so you might be able to calculate the exact power of the maneuver
Should be spelled Clarke belt since it's named after Arthur C. Clarke...
Nah it’s named after Clark Kent, who transforms into superman, obviously. When you put on the Clark Belt, you are in 0 gravity, hence the name.
I love how this guy always has like.. 15% of a smile on his face.
When people quote the cost of sending something up a space elevator, they are only referring to the incremental cost. What EVERYONE neglects to talk about is the cost to put the tether in space. It won't be free, nor do I think it would even be possible and the cost would have to be amortized over all subsequent lifts.
"It's almost impossible to speak in hyperbole about the space elevator."
correct me if I'm wrong, but I'm pretty sure that's hyperbole.
Kurzgesagt. Not kerzgesazagt
I love your videos, but:
Civil Engineers are just people that couldn't cut it as a Mechanical Engineer.
Best Regards,
A Mechanical Engineer
Reading through the comments (well, the first few hundred at least!), I am reminded of two science fiction stories - but can't remember the title or author of either of them!! One is about a building which is being built to reach the sky and the lives of people building it and living on the various levels. It's fantasy, obviously, but it still illustrates wonderfully the size such a building would have to be and the distances and time involved in moving up and down it. (Spolier alert - they do actually reach the sky - and then break through it!) The other story I only have the faintest memory of, but I think in that one a space elevator (there might have been more than one) has lost its cable, which is now coiled all over the ground. When the people in the story find this cable (which is very thin, but supremely strong) they discover (the hard way) that it can cut through almost anything. If anyone reading this knows these stories please tell me! Ta.
The first story is probably "The Tower of Babel" by Philip Chiang. It's actually biblical science fiction, written as though someone from the late bronze age would write, with their understanding of cosmology. One of my favourites!
The second story is probably "Ringworld" By Larry Niven, where they come across one of the broken cables whioch held up the shadow squares which, in the Ringworld, were used to create an artificial nicht and day sequence. The cables are very strong but obviously not unbreakable because it's lying there because it got broken! Maybe you should start to take notes when you read...
A few other important points:
- The most practical way to power the elevator is to have large fuel tanks that get jettisoned, just like for a rocket, rather than using lasers.
- If we're already assuming we can produce a graphene cable strong enough for a practical space elevator, we might as well assume we can pair it with a superconducting cable for power.
- The minimal space elevator is far from getting things to orbit, as it doesn't directly impart velocity.
- It would have to be much longer to allow things to accelerate via centrifugal force, and to gain more gravitational potential.
- Vibrations along the cable and micro-meteorites are not to be underestimated.
- Rockets are surprisingly efficient (around 10% for some orbits?). Given the huge upfront cost of space elevators, the long travel time, etc, it will take a while before they get competitive.
The Devil's not in the details, he's in the White House.
Oh yes.
Isn't centrifugal force really a pseudoforce like the Coriolis effect?
Ben Kim Depends of the frame of reference. If static reference is used then yes. If rotating reference is used then it becomes a force.
Yes, it is. It's fictitious. Sure, it seems real in a rotating frame of reference, but if you were to release the object from your tether It would not continue to travel in the direction of what seemed like a force, the object will fly tangentially not radially.
xkcd.com/123/
"CentrifugalForce"
It's ok... you're just not a physicist
It's not a force!!! But I get why he's using it
Whats the problem?
@@sebastiaomendonca1477
Engineers and Physicists have some disagreements on terminology.
Physicists characterize everything to get a deeper understanding of reality while Engineers just need things to work, so they are often times intentionally ignorant of the underlying ideology of their language.
Here's a good video from a Physicist's perspective.
th-cam.com/video/zHpAifN_2Sw/w-d-xo.html
@@Broockle Sure it may not be an actual force, but you can use it to help calculate the needed speed/height
@@sebastiaomendonca1477
ye u'r an engineer too ;D
They just need things to work. And it does work mathematically as a force.
To a Physicist even Gravity is a fictitious force caused by spacetime curvature.
It's a funny world.
3:45 I'm pretty sure that increasing the mass doesn't help solve the problem. True, the centrifugal force increases, but because gravity is w=m*g, the centripetal force increases as well. Because at the Clarke belt, the weight is equal to the centrifugal force, both scale by the same factor and there's still no room to add the tension by the tether. If the satellite is slightly beyond the Clarke belt, however, then increasing the mass still causes proportional increases in both radial forces, but because the slight difference to begin with, the absolute difference actually grows. Basically, increasing the mass can't compensate for adding a tether without being accompanied by a increase in altitude. I suspect that a captured asteroid is suggested as a possible counterweight because having such a high mass would cause the tension to be trivial compared to the high centripetal and centrifugal forces.
I would love for you to revisit this particular topic again I think the engineering would be quite intriguing if you include resistance of our atmosphere.
Well, it looks like multiwalled nanotubes are good electrical conductors, so the power problem is solved, just make 2 long cables out of carbon nanotubes around 1-2 meters apart and put the lifter between them, set up a few thousand volts potential difference between the cables and have the lifter run an electric motor from that. Ok, I know, the exact resistance of the cables will be critical, but also the gravitational force decreases with height, so you will need less current as you go up.
You lack nothing in charm, Grady. Loving your work!
There is a small but significant thing I believe you may have overlooked. While discussing the taper ratio you mentioned how the line (at minimum) must support its own weight. To my knowledge you did not factor the weight of the tether into your calculations for the distance of geostationary orbit. I went and used the small scale carbon nanotube ultimate tensile strength and calculated the weight of the strand to be on the order of 1000's of tons (I used calculus to integrate the mass with respect to radius from the earth to find its actual weight not just its surface weight), which drastically affects the needed centripetal force to sustain orbit. This doesn't affect your conclusions at all, and if anything strengthens your argument, but it's an interesting and really fun problem.
You should do a video about the much less unfeasible skyhook sometime. This concept deserves more publicity!
The last paper had an assumption that the space elevator must be stationary, which is why they pick R_g to be geosynchronous radius. Technically the counter weight just need to maintain constant altitude, it does not need be geosynchronous. So technically R_g could be at any value, as long as the counter weight orbital velocity is sufficient to counteract gravity and we don't mind the elevator to not geosynchronous.
If we shuffle the taper ratio equation in the last paper for a bit, we can estimate it as Ln(taper_ratio) ~= C * 1/(R_g^3). Which mean even use the worst example of steel, there would be no taper require if the R_g is roughly 3.2 times longer than geosynchronous orbit altitude. It seems way more feasible to just have 3.2 * R_gsync length of tether than a tether that taper to 10^33 times at the end. Assuming 14 gauge wire, at 3.2 * R_gsync length would roughly take 0.07 % of 2018 global steel production. It's pretty big amount but it's not an impossible amount. Certain Olympic stadium construction consume way more steel than that.
But then this design would require the "tower" to be drifting at some velocity to compensate for the non-geosynchronous-ness. Nothing mention all the additional drag, vibration mode, increase travel time and a whole host of other issues. I guess you could have multiple counter weight satellites "baton pass" the tether between each other in order to let tether remain stationary. Or have some sort of mini-planetary-ring-world like counter weight to let the tether remain stationary.