Another possibility is to hollow out the asteroid and build a spinning habitat inside. The outer asteroid layer acts as a shield, and could be mined for all the water and other materials. Also, if this hollowed area could be pressurized you could plant crops and such. A very slight spin would allow for water to go down and plants to grow up. Now too me, this is far more realistic and interesting.
I've been much more of an advocate for the O'Neil cylinder inside the asteroid idea. Though... you do have to have some strong magnetic bearings to ensure your cylinder doesn't precess out of center.
Found this after independently duplicating your comment. Precession is prevented by building counter-rotating structures attached to the habitat. They have equal but opposite angular momentum, so no precession.
Couldn't the whole structure just torque off the asteroid itself? The enormous mass of the asteroid would serve as the counter rotating structure to the relatively tiny mass of an air-filled space station. If you place the station at the centre the effect of the asteroid would be barely detectable.
I expect asteroids are going to be predominantly loosely packed rubble piles. Using the intrinsic rock as a shield will probably be about as effective as covering a bunker with packing peanuts. I'm betting on a bit more structure from a combination of engineered trusses and bails of loosely consolidated raw asteroid material. Still going with an un-spun shield made up of bailed rocks and water tanks then connected to a spun habitat inside with magnetic bearings. Asteroids like Ceres or Eros would ironically be too big, carrying with them small but noticeable gravity fields. A habitat built inside a void would get the vast majority of its gravity from its own spin but then have the asteroid's gravity overlaid leaving inhabitants with a gently rocking environment. Everyone's soup pots would be self-stirring but furniture and dinnerware would be self-relocating. An engineered external shield would be uniform in mass netting out to zero gravitational effect. A shield wouldn't need to be especially overwhelming, a dozen meters thick combination of rock and water tanks would put up far more protection against micrometeorites and radiation than the Earth's atmosphere. Habitats inside asteroid voids would not be ameniable to relocation. If Eros station ever got bored and collectively wanted to to experience the thrills of Mercury or hanker for a jaunt to Pluto it would mean thrusting all 34km by 11km by 11 km (6.7e15 kg) of Eros. A habitat with engineered shield would likely mass "only" around 1e12 kg, a featherweight compared to Eros.
All the tecnical details aside, they didn't spin those asteroids up to martian gravity. A major point in the series is that gravity on stations like Eros and Ceres is so weak that belters are having serious muscle and bone issues. They can't live in either martian or earth gravity. I always figured ceres and Eros had somewhere between 0.1 and 0.2g of gravity.
There is a scene of a character pour a drink from a jug. The stream shows exagerated effects of corriolis. I think this would indicate a very small radius station spun at high rpm. I seem to recall from the books too that well-to-do on Ceres could afford apartments on the edge of the station where the spin gravity would be highest and thus cause fewer health complications. Then there were the unspecified, expensive medical interventions that Belters could undergo to mitigate the health effects of low G, a rubbing point between Miller whose parents did pay for the interventions and other Belters. It set Miller apart as a privileged rich boy.
I can't remember if they specify it in the TV show, but in the book it's stated that Ceres is spun up to about 0.3 g, which is close to Martian gravity. The slums of Ceres are toward the "ends" and are closer to the axis of rotation so the coriolis effect is more pronounced. Most stations and asteroids that use spin for "gravity" have settled on something in the range of 0.3 g, however there are a lot of habitats on moons like Luna, Ganymede, Titan, Io, and Triton that just have whatever gravity the moon naturally has, and there are a few smaller asteroids like Pallas which were never spun up because they couldn't take the stress and so have almost no gravity at all.
I've never had time to read the books, but the TV show titles make it look like that. I know there was at least one religious group who believed that instead of living on the surface of a sphere, we in fact lived on the interior of a sphere en.wikipedia.org/wiki/Koreshanity They had to come up with some rather complicated refraction mechanics to make the sun more correctly in the sky. If the GOT world were like this it would need something similar to create the sunrises and sunsets in the show.
i always assumed that for the stations they dug out some of the asteroid/body and spun an cylinder inside it. cheaper, youre mining the body anyways, and you're spinning up the cylinder not the actual body.
also i guess all that rock is a nice protection against that nasty space radiation, in my opinion that's the only advantage of digging a hole in an asteroid instead of building something on the surface anyway.
frischer bärlauch speaking of those nasty little solar rays i wonder if it's possible to put something near Ceres to block out the rads, like a nasa scientist (i believe it was) suggested recently. Then you could build habs on the surface. Maybe put up a nice little space elevator.
+Daniel Carter Well, why would you build a large space habitat like that, to shield workers from radiation and micrometeorite and provide them with artificial gravity while they mine the asteroid but wait, if you have to mine the asteroid first before building the habitat then how will you house them while mining and once it's mined, why would you continue to have to house miners? It would make far more sense to build a smaller habitat either floating nearby or a small centrifuge on or just below the surface rather than turn the entire asteroid into a habitat.
John Wang i never said a hollowed out asteroid with a cylindrical city made sense, I'm just saying that's how i always figured it was done. Personally I'd but a magnet in orbit to block stellar radiation and build bowl shaped habs on the surface and spin them to have artificial gravity. And you'd want a permanent base on Ceres because there aren't any satillites, it's rather small, lots of fuel, and it's larger and more circular than a lot of other bodied you could consider.
John Wang i don't see the point in a habitate on a planet or a dwarf planet or whatever if there is no atmosphere, you might as well sit in a tin can in orbit. However, I wonder how much radiation would actually be absorbed by an asteroid if it has such a dusty consistency
I would just say that it's not so much that rock isn't strong, so much as it's the wrong kind of strong. It's strong in compression, but this structure requires tensile strength, and rocks in general are indeed very bad at this.
Depends on the composition. Plus nobody said that you can't reinforce or stabilize faults in an asteroid. The stations in ED all have massive struts holding them together from the inside.
answer is fairly easy....mass is the issue,,,soo just hollow the thing out morons. remove like 4/5ths the mass....in fact they did on the show, they extracted all the water .
I had thought that in The Expanse they had mined out much of the interior or several asteroids over many decades, adding improvements to support miners as they went: air, water, waste processing, tunnel reinforcement, long-term living quarters, machine shops and warehouses, etc. So perhaps over 60% of the mass had been removed and what remained was of value due to those improvements. Still fantasy, and it probably adds new complications, but that might change some of the numbers.
Nice video as usual. I haven't read the books but recently watched the first season on Netflix. I kept thinking, "How'd they spin Eros up?", and, "Wait, it would fly apart, what's holding it together?". Then when it started talking about the same for Ceres i just decided to turn off my critical thinking on the subject and enjoy the story. With that much energy they could easily construct a very nice spinning habitat using asteroidal materials, ie organics and metals. In fact they could make lots of them.
it would be alot easier to use a iron asteroid,,,to build a space station. melt it down and build what ya need. or at the very least just hollow it out mostly. like 90% hollow.
I think the reason for Ceres station being the way it is is because "digging" requires a lot less material than actually building something. Just dig and throw away some part of the asteroid and voila, you suddenly got space you can build a habitat on. The spinning part is to resolve the gravity issue. When you have a basically magic Epstein drive, that's not that hard
Yeah Scott, I'm with you on this. I think the reason for interest in asteroids, is mining them. What one could do, is mine the materials for building a space station, rotating the station for gravity. It could be engineered for safety. After it is built, maybe one could sell the rest of the stuff you mine.
You can't possibly consider a guy who makes you do homeworks and eat your broccoli cool. Not at his age. The understanding of Scott's coolness will come later.
Decades ago, Prof. Lionel Wilson (UK) discussed hollow asteroids as the common, result, of small impactors penetrating some depth before fully releasing their superheated vapor of impact hollowing-out the asteroid insides, expanding the looser rubble outer thickness, and depositing melt and vapor, brazing, sealing, and pressurizing, interior chamber 'walls'.
I think in the books they describe the tunnels that were the spin up tunnels, one shot engines of some not specified type. The books were long on concept short on details, probably for good reason. Sure, we could do like the earthquake proofing of buildings in California where you have rebar running through the length of the asteroid to help counteract the centrifugal forces but I think they are held together by the writers imagination ;)
Well, something to consider is that while you are digging the asteroid, you need to to something with the resulting material and one possibility is to "shoot" it out to push yourself (maybe engineering the orbit to be more stable or obtain particular rendezvous). The spinning still remain a problem, but lets go back to a smaller asteroid with reinforced structure, you are pushing a lighter and lighter version of the asteroid, to the point when you are mostly hallow, and the energy requirement to bring to "final spin" are greatly lowered. Basically the asteroid became a source of resource in a convenient orbit, more than your ending base
I can't see spinning a hollowed asteroid for artificial gravity but I can see doing a cut and cover rail system around an asteroid so that you could have artificial gravity in what's essentially a train on the tracks. The reason for cut and cover would be for radiation and micrometeorite shielding
@@jorgepeterbarton Tangential velocity would depend on the radius but nice try at seeming to sound as if you know something. Yes, it would be fast but you are in space and magnetic suspensions is more than sufficient, I would imagine permanent magnets on a Halbach array along the habitat pressure vessel and aluminium coils as the tracks thereby using Lawrence Livermore's Inductrack system as the materials needed are plentiful and there would be no need for cryogenic temperatures, just heat dissipation issues from the aluminium coils but aluminium also makes good heat radiators. Of course, it would be maglev as well as tension cables in the habitat as the habitat could go completely around the "track" hence the mag Lev would not be needed to sustain the entire weight of the structure even when spinning as the tension cables would do that, the magnetic levitation would only be needed to center and guide the structure so no contact is made, and quite frankly, as most of the forces would be in the tension cables anyways, even a mechanical system instead of maglev could be used as again it is only centering and guidance that would be involved and that would be intermittent. A mechanical system would just be more costly and precision manufacturing intensive than just setting up a Halbach array and aluminium coils. We're not talking about the precision supercooled maglev of millimeters of trains on Earth, just preventing a spinning ring from contacting what it's spinning in while in the microgravity of an asteroid. Normally, the habitat pressure ring should not require anything to avoid contacting whatever it's spinning in, it's just that occasionally it would need to be guided away.
I was sort of expecting/hoping you were going to build a hanger into an asteroid in KSP and spin up it's rotation via srbs or something and dock into it...
A bit of this is addressed indirectly in the books. They do say that it took decades to spin up an asteroid (though I don't think they were talking specifically about Eros), and the Epstein drive is fueled by very small pellets, so it is phenominally efficient. What isn't addressed is keeping the body in one piece and ejection mass. So in-universe, energy and time are addressed, stability and propellant are not. My head canon is they use the rock itself as ejection mass. As it is melted by the Epstein drive, the magma itself is used to accelerate the drive. 3/4 issues resolved is good enough for me when the story is as good as The Expanse.
Warp Drive - Hyperspace - Wormholes - Transporters...yada, yada, yada. How Many Angels can dance on the head of a Pin? It's not called SciFi=Science Fiction, or SyFy=Science Fantasy for nothing folks!
phobos would make a nice equipment platform, with a molten salt thorium reactor. Don't want no stinking gravity, just a big gymnasium to play 3d ball in.
Its videos like this that see you being the only KSP channel I bother to subscribe to. This video is so much more valuable than some of these "look at my cheated ship go everywhere" channels.
Scott, I think it's absolutely amazing how you can explain such complicated subjects(relatively complicated for us, who aren't educated like yourself) and explain things so we can understand it much easier. I have learned a lot from you and I appreciate that like you have no idea. I would imagine that if you had a Scott Manley when you were growing up, you would be far more educated than you are now(which is truly hard to comprehend). I wish you luck in everything you do. Thank you sir.
There is a common misunderstanding that asteroids are large rocks. In most cases they are gravel balls, there may be a large rock in the middle somewhere but it is likely that they are mostly gravel and dust cemented to the large rock(s). Even if you found a large enough boulder to put a base on you would be subject to a storm of loose debris bouncing and orbiting through highly erratic orbits. This would make it extremely dangerous to attempt to land on and would require the base to be buried deep inside the asteroid. Making it largely inaccessible. It would be a much better plan to do this on a planatoid like Ceres. The weight of the armor you would need to approach an asteroid would be less then the fuel required to land on and launch from Ceres. In my opinion the best plan would be to build a space station that would be easy to spin and use drones to collect the material you are there for. A space station would be a lot lighter and could be driven around.
There is a common misunderstanding that asteroids are all the same thing. Also, Manley's projection seems to assume this trick is easier for larger objects. The opposite is true. With a maximum spin rate of 2 RPM, you can get useful gravity with natural materials, like basalt and granite. Nobody is going to try to spin up a slagpile. This is a "straw man" post.
you got a gift man, I actually understood when you started spitting math out, normally that's about when my eyes glaze over and I zone out. keep it up.
Yup. That's why in my sci-fi stories, space habitats hide behind asteroids. In other words, the asteroid always blocks direct sunlight and solar radiation from hitting the space habitat. However, in most cases I put a huge lightweight ring shape structure beside the space habitat and barely a sufficient distance away so the sunlight is not blocked from hitting it. Essentially this structure is just a ring [with internal web] that holds huge sheets of something like aluminized mylar at a 45-degree angle to the sunlight so the light reflects off and onto the habitat. Note that highly energetic particles will pass right through this material while lower energies like visible light bounce off and provide the habitat with illumination and a source of energy. A few other minor components are also required to keep everything stable (since the main asteroid has a tiny bit of mass and thus exerts gravitational and tidal forces on the habitat and energy reflectors.
but then you still would have to spin up the mined material...that would undermine the whole idea of hollowing it out in the first place...you need to bring out the mined material fia conventional, far more efficient methods...
So what you're saying is hollow out the asteroid and use spacecraft to dump the mined material somewhere, then spin it up using fuel you brought from earth? That doesn't make any sense.
no...i am saying hollow out the asteroid without spinnig it, removing the mined material with, lets say conveyor belts or push it out or give it a little push and let it drift out in microgravity and then, after removing most of the mass of the asteroid spinning it up
and who knows from where you get the fuel, doesn't need to be from earth at a time where you are technologically advanced enough to hollow out an asteroid...could even come from the mined material itself...
Thanks for the video, Scott. I remember talking to you about the issue on reddit. I love the Expanse, too, but sometimes it's just fun to pick it apart :)
Rock is also particularly ill-suited for this application, because it's at its weakest in tension (which would be the dominant stress mode in this case). Alternatively, what about Niven-style blowout asteroids? His suggestion is to use nickel-iron asteroids, balloon them using steam pressure, then spin them up. Would this be plausible with smaller asteroids, or is it another case of him failing to consider material strength a la ringworlds? Separate question: Sci-fi authors love space elevators, but even assuming you could create a suitable cable or ribbon, how would you actually get the whole thing in place to begin with?
Ignoring engineering details like material strength and resonance modes? Conventional launch of bootstrap material, then build the tether down from geostationary orbit while simultaneously building the counterweight up. Once a minimal tether is in place, you can haul additional material up the tether and reinforce it.
In Niven's books, humanity has infinite cheap energy. So heating a metal asteroid up to melting point and inflating it is plausible, in his fictional universe.
Elevator cables: elevators are only going to usefull in fairly high-gravity environments where rockets are big and dangerous. An elevator at Ceres or Eros would be easy to do but wouldn't save much over using low-thrust rockets. On either you could do all your launches with catapults. Getting an elevator cable would be just a matter of fabricating it in space. The minimal cable, only large enough to accomodate a modest climber would still mass around 100,000 tons, close to 1,000 SLS launches. That would still leave the challenge of seamlessly splicing the 1,000 or so cable sections in space. An easier approach would be to source all the raw materials from a carbonaceous condrite and fabricate the whole carbon nanotube or graphene cable in one continuous process. Attach an archor to one end and gently lower it to the surface of the Earth. The only necessary thing it that the center of mass of the cable is at geostationary orbit above the point where you want to anchor to on Earth.
Kevin Shepardson, A stationary space elevator is assembled in orbit. Preferably at synchronous orbit but, perhaps, the structure is gradually moved outwards with ultra-high efficiency engines. The center assembly (micro-g) hub is supplied with spools of fabricated graphene tube segments. Splicing and composite layering is done until the ribbon is ready to deploy both up (out) and down (inwards) simultaneously. The initial elevator fabrication must reach full length before it is ready to be lowered into the atmosphere and anchored on land or sea. Until then, the excess length is stored on spools and/or the ribbon cable will be deployed folded over a pulley at the weighted lower end. With folding, the true endpoints can be maintained in the center micro-g fabrication hub until self-mass and layering requirements preclude this. There are several harmonious ways to continue fabrication. One is to install fabrication plants and/or habitats at both top (outward) and bottom (inward), which need to be weighted anyways. The inner end will eventually experience near surface gravity, even while above the atmosphere. The second is to fabricate and deploy the actual ribbon endpoints from the hub. Of course this requires folding at the weighted ends. The third is to shuttle along the existing structure, bonding new composite layers. The outwards section can be shorter than the inwards section if a greater mass is maintained at the outer end. Both must be adjusted to maintain balance so that the micro-G fabrication plant can operate correctly. A side effect of lifting all mass to the geostationary point is that a large amount of potential energy is stored. The act of deploying the cable will allow this to be converted to electricity, for example.
Maybe you don't need that much gravity. I think the minimum would be just enough to do gravity-assisted bodily functions. Has NASA performed any study on low gravity pooping?
dkosmari As far as gravity goes you can go as low as you want for the most part. There are some exceptions, but mainly the return to normal gravity is what causes problems since your body quickly adapts to microgravity. Astronauts on the ISS are actually really comfortable until they return.
Yes you can the ISS has a toilet. Actually shouldn´t be a problem to live in low gravity as long as you don´t plan on returning to gravity ever. Well in the Expanse they came up with fancy medication that keeps your bones strong so if you have that it might work no problem.
You can poop just fine in zero g. Here's an experiment. Stand upside down on your hands and try to poop upwards. Piece of cake. If your bowels can overcome negative g's they can surely overcome 0 g.
I thought this was called the Poynting-Robertson effect, but i follied, the effect is restricted to the degradation of angular momentum on dust due to radiation pressure rather than adding spin. At least you made me correct myself on something I learned about years ago!
The asteroid belt is about as far away from the sun as you can get and still primarily use solar power[1] so maybe? The question is is it worth the time and energy to try something like that or do you build something that you know will work and fly it out there. [1] I know we've sent solar powered probes out farther than that but I'll take a RTG at that distance any day of the week.
I was talking about natural the spin up process, if vaporizing ice might cause the asteroid to spin, but I guess focusing sunlight intentionally onto an icy part of the asteroid would be a very cost effective way to do it assuming you have large, cheap and accurate enough mirrors to do it :) And now that I'm a little bit less tired I can actually calculate the distance at which this can occur naturally: It would be using Stefan Boltzmann's law and some algebra we get: r_asteroid^2 = T_sun^4 * r_sun / T_boil^4 (We got this by calculating when the amount of energy radiated per area of an asteroid being at boiling temperature is the same as the energy received by the suns radiation). Plugging in some numbers that gives us 166 805 431 km or about 1.1 AU, so yes, they are too far out for this to be a thing. However liquid water does still evaporate slowly, so plugging in the freezing temperature of water instead gives us 2 AU. Still not far enough out, but some asteroids could come close to that distance. Still, using mirrors to do this if there's ice on the asteroid would be viable, maybe even a way to move the asteroids :) Then you wouldn't need to transport anything out to the asteroid to move it, you can just shine the "sun death ray" on it in very precise locations. You would need some very large mirrors tho, but that wouldn't be much of a problem, they would be pushed away from the sun slightly but easily compensated for using small thrusters, or you could position the mirrors in such a way that the small distance your pushed doesn't really matter much, eventually you would have to compensate for it tho if you plan on using the mirrors many times to move many asteroids. In practice you would probably still have to send probes to the asteroid to determine it's exact center of mass, where ice is etc etc so you know where to shoot on the asteroid. You might also need to send up mirrors to be able to shine light behind the asteroid. I think Isaac Arthur made a video on this, not sure tho :/
If you look at a phase diagram for water you see that you'd have to get above 200 Kelvin at a minimum to get vapor. Plugging that into the previous equation gives us about 3.8 AU, so yes, there are asteroids inside that range within the asteroid belt it seams (the belt between mars at around 1.5 AU and Jupiter at around 5 AU) If you're talking about "stray particles sublimating" such as evaporation experienced here on earth even tho you're not above boiling point, I don't think this would have a very big effect in a crystalline structure such as ice but I could be wrong, I just thought the temperature distribution in the substance thinned off very quickly when you get down to lower and lower temperatures allowing for extremely few atoms to sublimate.
Going further deep in this topic, one photon from the sun has more energy than the hydrogen bonds connecting each molecule in a crystalline ice structure. So I guess exposed ice will sublimate, no matter at what distance from the sun. I think this mechanism is better called ablation than regular sublimation, but... Let's go to the numbers: The hydrogen bond energy in ice is about 4.5 kcal/mol. With 4 bonds in a crystalline structure, this gives an energy of 0.78 eV per molecule. Even a low energetic red photon from the sun, with a wavelength of 780 nm, has an energy of 1.59 eV. Of course some of that energy is transferred as heat to the ice (and I have no idea on how to estimate that), but I believe there's a significant sublimation rate. Maybe enough to spin an asteroid in a couple million years.
I remember reading KSR's Red Mars trilogy and he has loads of hollowed-out spun up asteroids flying around. It always struck me as impractical, if not totally infeasible. Interestingly in the beginning, when they're setting up a colony on Phobos, they do build a large track that runs around the entire surface to give a sort of "refuge" where they can get into some gravity rather than having to live entirely in milli-gee conditions.
That "train" idea was exactly what I was going to post...and, although I thought it was an original idea, I read the first book of that trilogy a long time ago so my subconscious probably just plagiarized it. To go a little farther - since I can't recall if they did it in the books - I'd say hollow out the interior for use as a micro-g space-dock for the ships, slap rails around the outside, and basically make a space-version of that carnival ride where you get spun around-and-out in little seats that are tethered to a spinning central pole, in this case using nanotubes and relatively small pods to keep the math realistic ("extended stay hotel rooms" for you and your crew to get some g's, go to meetings with others, etc.). Now that I think about it, Neil Stephenson's recent book Seveneves does something like that, and AFAIK he actually did the math/got help from people that could do the math for him. Damn my memory once again! :O
It makes sense for several reasons: 1) Assuming you're mining the asteroid, you've got to remove material from _somewhere_, and I see no reason why you wouldn't construct mines relatively the same in space as on Earth (i.e. "dig where what you want is"...which is likely to be inside, not on the exterior of the asteroid) and 2) Kepler Syndrome is already a known/potential issue around Earth; I can only imagine how bad it could become around an asteroid that's being mined/constantly visited by ships/etc., so 3) by keeping docked ships inside of the asteroid, you not only have much better control over debris, but you effectively shield the ships from all external sources of damage as well.
Tbf, by the time we see the asteroid colonies, like the one that goes off into interstellar space, they have much more advanced technology. Enough to have a city on wheel on Mercury, undersea ones in Europa, fusion power, and they apparently can make diamonds for peanuts, given they had dams of the stuff on Mars.
Larry Niven had a slightly different method for creating asteroid stations in his Known Space books. They would take a reasonably pure nickel-iron asteroid, put a heatproof balloon in the middle, then use solar mirrors to raise it to melting point. They'd inflate the balloon up to the right size and shape, then let the whole lot cool. Seems more reasonable than just hollowing out an asteroid, and the original asteroid doesn't need to be anything like as large to produce the same size habitat, either.
The key is to spin the internal structure relative to the surrounding asteroid material, then correct the outer spin of the asteroid to keep it stably non-spinning with exterior boosters.
I haven't put any thought into this other than the idea just popping into my head, but in the same way a longer wrench provides more torque and makes it easier to turn something, would it be significantly different (Or any different) if the engines were 100KM off the surface and attached in some way? So you'd essentially be spinning an object "500" KM in radius, but with the same mass? Disclaimer, I am the opposite of a physicist, whatever that would be called.
sonnder I wouldn't think so, because with a wrench you're trying to overcome material sticking forces, which is why more torque is helpful, but there isn't any such forces in the vacuum of space. The only force to overcome is this YORP effect mentioned. It becomes a relatively simple matter of just imparting the needed momentum.
Yes, that would greatly reduce the thrust and/or time required to achieve the proper spin rate. And you would not need a frame system to handle the "torque", you would put the engines on a 100km tall tower than run a cable from the top of that tower to the horizon. The cable would be under tension pulling tangentially to the surface, the tower would be under compression.
you gotta think outside the box. this is a case of mythbusting similar to that infamous mythbuster show where they claimed pirates couldn't possibly glide down sails with swords simply because the tv show crew couldn't physically do it. there are many crazy physical feats people do that blow my mind. so for the asteroid spinning, you could hollow out the asteroid, cut it into big chunks and spin each smaller chunk separately. bring the asteroid back together and stitch up. tada!
Hi, guys! This video puts me to idea, that big space station (death star particularly) has a HUGE inertia momentum, and if it is not positioned to target initially (see Rogue One movie), it... WILL SPIN ITSELF OUT (100 km diameter claimed multiplied by reasonable speed of rotation gets linear accceleration, that no carbon nano-tubes can withstand) Bye-bye, Death Star!!! PS. Scott, I've started to look your channel a month ago, when started playing KSP. Man, you're doing really cool things and videos! Thank You!!!
Wait a minute, forgive me if this is a stupid question, but given Earth is spinning, does it also produce a force and reduce the pull of gravity to some degree?
Just the flotation effect of gas pressure on the volume of our bodies negates more than that I'd say! Just that we don't notice it since we weigh in with that already subtracted. How much more DOES a human weigh at earth sealevel in vacuum compared to in atmosphere ?
thank you Scott Manley. Great stuff. a fun mix of Kerbal, sci-fi, and hard science discussion, all in a Scottish accent. I wish I had stumbled across your channel earlier.
I did the numbers for something like this a few years ago for a story I had been working on, just growing lore and such out of "What if we had this space travel tech..." kind of thought experiment. A big part of it became a "Because we can!" sort of thought process... - While mining useful materials from a very large asteroid you give priority to minerals that lie within a target structure space - These spaces then become room for reinforcement structures and living space. - While processing the materials, useful refined material is ejected at set points by mass driver, while waste material is ejected at other rotational positions... The energy of shipping your product and disposing of waste material then automatically inject rotational movement into the asteroid as a whole. - Eventually you have a shallow gravity well deep space location that has 0.7g or something, and natural armour such that it becomes a non-trivial energy level to destroy or even be able to do much in the way of major damage, even if defensive weapons systems fail. - A rotation structure also offers defences against long duration directed energy attacks - Some neat sweet spots develop at the right rotational speeds, mass, and materials - You increase the required energy to really do anything since by the time the energy weapon has heated the surface enough to start really changing anything then it has moved around to the far size and can naturally radiate the energy back into space. - A non-trivial rotation speed also gives handy attack/defence advantages, as weapons/access ports are now moving more rather than being more stationary targets/launch points.
I guess you could try reinforcing the asteroid to hold it together better...though at that point, you're probably better off just building your own space station and mining some non-spinning asteroids.
Great video, as always, but I don't think the concept of breaking strength could be applied to this problem directly. Imagine the spinning rod (around one of it's ends). Centrifugal force will vary across the rod length, unlike gravitational force used to derive the breaking length. So, to derive maximum length of such rod rotating with angular speed omega, we need to integrate. The answer (if I didn't make some dumb mistake) can be put like this: if we want to have an acceleration of 0.3g (like Eros in the Expanse) at the end of the rod the maximum length will be (breaking length)/0.15 or approximately 6.7*(breaking length). So to support such rod with length equal to Eros radii the rod's material need to have breaking length about 1.3 km. Of course Eros is not a rod and even not a ball, so one need more complicated analysis, but i think it's a great approximation that shows that the stresses aren't that big, and maybe if one chooses the rotational axis carefully, this is possible even without structural modifications. For Ceres the breaking length needed is about 70 km, still quite impossible with rocks. And of course spin-up still requires insane amounts of energy
The Earth is considered one of the small planets in our solar system... at 12,750 km in diameter. Eros at 34km by 11km by 11km is roughly a billionth the volume of Earth and about 10 billionth the mass. Our sun, just 1 of about 400 billion in the Milky Way, weighs in at 3 million times that of Earth. So, yeah, Eros is small.
Hey Scott! nice! destroying The Expanse like that :P ...Did you do one about the Elysium space station? i was thinking would that design really work? how fast would it have to spin to hold the atmosphere in place and wouldn't the radiation be a huge problem
To touch on your final thought of an artificial gravity generator on the surface, that's what I was thinking throughout the video. a corridor placed at an entrance to the asteroid that would be stationary with a massive bearing at the end where it connects to a large docking bay or what have you, the bay could rotate inside the asteroid to generate gravity. To counteract whatever destructive force that artificial gravity would cause on the asteroid that docking bay could be placed inside a set of rings spinning in the opposite direction. Nullifying any gravity shift between the rings so no amount of artificial pull or rotation would be transfered to the outer shell causing the asteroid to collapse on itself or break apart.
I don't know a lot about astronomy, so I'm a bit proud that it only took me like 200 milliseconds to figure out that differential reflectivity could be the cause of an increasing rotational speed.
The concept of steroid bubble worlds is many decades old. A model of such was featured as an exhibit at THE GRIFFITH OBSERVATORY over thirty years ago.
This is something I've been thinking about whilst reading the series. All they said was it took a generation for engineers to figure it out. And they note that there were no surface pebbles. But other than that, no details yet.
I recall Dandridge Cole and even Ernst Fasan (lawyer) were talking about using astroids as outer shells, while the rotation would be only applied to the inner cylindrical structure.
it makes more sense to hollow out an asteroid, build the space station inside the hollow asteroid, and spin the can inside for gravity. you would have less mass to move, you could easily build a dock accessible from the central axis for cargo and personnel transfer, and you still have a lot of mass from the asteroid itself for radiation shielding. you can even use the overburden from hollowing out the asteroid to help protect the dock whether you fuse it thermally or with some polymer binder.
This was pretty much my exact thought when I heard of the concept of Ceres from the Expanse. It went like this "The writer is not very well versed in physics if he thought something like this would work at all and not tear apart an asteroid,". Even I knew that, and it isn't like I'm an expert. I work as a chef.
First example of an asteroid based space station that I ever came across, was in one of the first SF books I ever read as a youngster (oh how the time has flown)... VENUS EQUILATORAL. Science in it is of course somewhat rusty by now, but what counts the most was the internal consistancy of the stories. Damn good.
Nice analysis. One of the more implausible things I found with The Expanse series was how massive all the ships are. I would expect our future space infrastructure to be much more gossamer. Mass is expensive in space, and cuts into the bottom line. Their ships remind me of ocean going vessels, which can be massive and cheap to operate, since they have all that water to push against and they don't go very fast anyway.
Self support length as shown in the Wikipedia table assumes 1G acceleration and constant cross-sectional area. Objects that taper from top->bottom will have higher critical lengths, as will objects seeing
Suppose a tunnel boring machine has excavated a circular tunnel of Van Braun-space wheel dimensions. Place railroad track on the outer radius of said tunnel with interspersed linear induction motors. Operate pressurized railroad cars on the railroad at speeds commensurate with the ring-rail's dimension and desired gravity. Use them as residential/sleeping compartments to limit zero-g exposure. Operate the ring-rails in pairs to cancel out rotational effect on the asteroid. Operate three orthogonal pairs of ring-rails to intentionally control asteroid rotation.
Scoot Manley, i watched your video and got a good solution who he did not get cover. It is to create a ring of highly tensile strength material around Ceres equator in order to resist any Yoke effect. If the idea is to spin it, the "equator line" will probably be where the centrifugal force is the biggest one, so my focus will be to calculate there. Also i will approximate every ring as a cylinder with height as (h), but that will matter a little. Ceres is an asteroid with radius (R) of 482 km, density (p) of 2.7 g/cm and gravity of 0.28 m/s^2. Its perimeter around equator line is 3,028 km, which is 7 times lower than the Great Wall of China (21,196 km). In the show Ceres have spin gravity (sg) of 0.3 g, equals 2.94 m/s^2 with angular velocity (w) -> sg = w^2*r -> w = sqrt (sg/r) = sqrt(2.94/482000) ~~ 2.4 E-3 rad/s. Angular velocity is constant over all the radiuses. The centrifugal force from the asteroid requires us to integrate, cause the centrifugal force is a function of the radius, and we need to sum all the rings from the axis of rotation to the outer radius (R), so it will need to be an integral and calculated as -> dFc = m*w^2*dr = p*Volume*w^2*dr = p*pi*r^2*h*w^2*dr With 482000 < r < 0 Fc = p*pi*h*R^3*w^2/3. Since tensile strength (s) is s = F/area, the material needs to resist the Centrifugal force, and the area where it makes contact could be approximated to Ceres perimeter * height = 2*pi*R*h s/area = F = Fc. -> s = Fc*A = p*pi*R^3*h*w^2/3/2*pi*R*h = p*R^2*w^2/6 The material need to resists to: (2700 kg/m^3) * (482000) ^ 2 * (2.4 E-3) ^2 /6 = 650.48 MPa. 650.48 MPa Is well inside plenty of materials that we have. A High strength steel alloy got Ultimate Tensile strength in 760 MPa. Stainless got 860 Mpa, Maraging Steel (an alloy with nickel, cobalt and titanium) got even to 2500 Mpa!, and that is talking only about steel. Even talking in a shear stress perspective the perspective doesn't change, since shear the composite material of steel + Rock have a good shear resistance. In other words. It was a good exercise on Engineering skills and if that show made me try some, im glad. Hope you like the answer. Have a good day.
I see someone already mentioned this, and has a discussion going, but I'll say it anyway, here, because I would have to read all those posts to join. I think it would be better to carve out an area for a space station inside an asteroid, and just have the station itself spin. The asteroid would be a great shield against all that nasty stuff that flys around in space. Ever heard of an “OMG particle”? They're a rare kind of cosmic ray. There are of course, many less extreme, but more numerous cosmic rays, and plain old radiation from Sol to worry about. And those tiny bits of high velocity rock are problematic for a naked space station. As I learn more, I find it increasingly likely that things in space will be built mostly by robots.
You would not need to rotate the entire asteroid. A simple method would be to house a really big cylinder shaped habitat / working area that can rotate freely inside a housing/cage/frame that is located inside the asteroid driven and suspended by electromagnets (assuming resources and energy needed would be available). The habitat could be entered and exited through a gyro/gravi-lock system located at the centre of the cylinders rotation, to enter the hapitat the gravilock is enetered and then spun to match the rotation of the 'Habi-tube' to exit the gravilock is entered and spun down to a stop and then exited. Not all activites would require gravity especially working activities... The Habi-gravitat would be like going home after work where people could experience earth or even heaver gravity between work shifts. Those working as controllers, workstation operators would stay in the gravi-habitat most of the time while those working outside would be there during downtime.
Building a giant ring around an asteroid and connecting it to the asteroid with a few support structures, you could gently but relatively quickly spin up that ring using simple electric motors and solar panels. That would possibly be one of the cheapest ways to spin up such a gigantic structure. One could also do the inverse of this, like creating a spinning cylinder inside of the asteroid. That would leave the asteroid as a shield and a place for solar panels. Doing this would allow you to start very small by boring a simple ring inside the asteroid and start by spinning a few capsules to serve as an initial base of operations. You can slowly add more capsules and continue widening the ring to allow for more space as needed.
I love the idea. In the long run would be great. Kinda reminds me of a movie I saw recently. Around the end of the movie, they showed a hollowed out asteroid being a space colony (I'm sorry, the movie title escapes me - maybe someone would know, something about a black hole, made in the last 15 years). Plus one added feature, it would provide additional protection from the space elements (cosmic rays and other radiation).
IIRC in one episode of The Expanse you hear one of the stations flight controllers say they were going to take over control, I think it was season 1. Would it be easier for someone on the spinning station to maneuver in the ship trying to dock?
Thanks for all the fun food for thought you provide, Scott. Here's some dessert for you to enjoy: Since we're talking improbable projects here, let's go whole hog and really optimize it. I mean, why spin up and live on something solid when you can spin up and live in something hollow instead? More living space on the inside surface, with convenient docking at the zero-gee zones at each end seems a lot more preferable to limited surface domes at each end of a "peanut". Gravity for babies to develop safely in mom's womb also means an actual Belt civilization becoming a tangible reality. Larry Niven had the right basic idea: bore a hole through the long axis of a mostly nickel-iron asteroid a few kliks long by a couple wide, pack it full of water ice (all you could ever need or want can be found free over at Saturn), seal the ends back up, and then spin it up with laser-pumped diffusion mirrors trained on it to heat it evenly and soften the body of the asteroid. After the ice in the core turns to steam and the asteroid gets soft enough, the whole thing suddenly expands like a bubble from the core pressure creating a very large living space where the ice used to be. Of course, heat resistant exterior bracing will be required to prevent blowouts and to restrict the overall expansion as well as fine-tune the shape of the asteroid from say, peanut to cylinder for a more even structural mass distribution (and easier docking), not to mention the sheer amount of time required for the passive heating and cooling processes. Yikes, even. Right there is the deal-breaker. But, by the time we're ready to attempt an engineering project of that magnitude, the tech needed for the bracing and the superheating/cooling required to make the deal-killing time factor manageable and the project worth tackling at all will most likely also exist. We might even have working gravity generators by then that would negate the need to spin it up at all - slow it back down to a stop, clamp them on and fire them up, done. But, wait... With all that tech available to us, why not just build a habitat instead? Well, I personally prefer "natural" gravity to the type generated by a device that could fail at any time for any reason. Thicker outside walls are nice, too. If we're going to be having babies up there, I sure as heck want them to be as safe as possible, so a nice thick asteroid wins that contest every time. Murphy is the God of Space, after all. Cheers, mate. =)
There is one way to solve many of the problems you spell out in one go... First, use the ones you "don't want," the rubble piles, but reshape them first, by wrapping them in a sheath of wound fabric that is shaped as you like, but that has room in it as well for the later tunnels et al. In fact, you might even inflate separate balloon shapes as well, to carve out the space inside a bit. So once you have an "enshrouded" body, you then spin it up, shocking the pile at the same time, to let the outward forces start putting the matter into a different configuration, in the process reshaping the dust-berg into a BALANCED spinning shape to start with. THEN, once the berg is completed, spin it slowly under your solar concentraters, to fuse the outside, probably leaving the shroud in place.Then proceed with the finishing, after those internal voids you left exposed to space cool the sucker down...
Asteroids are for materials and possible industrial/military facilities which you can add smaller gravity blocks onto as needed. O'neil cylinders engineered to be as lightweight as practically possible with safety and cost in mind are for spinning up for artificial gravity and large sacale population settlements. Best regards, Mobile Suit: Gundam
you could hollow parts out of the suface and insert a spinning station into the surface, like the drum of a washing machine. you would have exterior entry for spacecraft etc, and interior entry to enter asteroids surface and interior structures inside the asteroid the station would be protected against radiation and smaller impact events,and would have easier time to sustain normalized temperatures.
I think it was a Larry Niven story that had a company using mirrors to focus sunlight on asteroids to heat them until they were molten, then inject gas in them to make gigantic glass globes to live in. From your presentation here, it sounds like this just would not work as he described. Which in retrospect makes sense. The impurities would crystallize in the glass and weaken it.
In regards to the spin-up time, it's possible that they built the station first, to eliminate mass, and then spun it. I don't know how expansive the station is but it seems like that would do a great deal to reduce the thrust required.
Well, that makes the Eve Online asteroid stations the most accurate looking - as they don't spin. However, I believe Eve has gravity generators for stations and ships, so its not needed anyway. :) At the same time, you've discounted Niven's explanation for how Spacers kept fit off Earth (using an asteroid as living quarters for children while growing up). Though you also have a potential solution for other structures like Rama and the Ringworld. :) Impressive amount of implications for (what appears to be) such a simple idea...
I always liked to think the Amarrians were the only ones with graviton based tech. While the Matari just kinda lived with out. That is, at least, before the cultures started "interacting".
If I remember correctly, there's an idea in an alastair reynolds book that's something along the lines of essentially shrink wrapping an asteroid in some super-strong membrane to stop it from spinning itself to bits.
Space is just so alien to us, we forget all the small important details that make the difference Ideas like: >Getting rid of heat in a void thats super great at islationg and also bombing you with radiation. >Not hitting small near lightspeed particles when flying around on long trips. >How fitigh in a 3D plane with km of noting between you and the enemy makes close combat for the most part stupid. >The huge distance between even the smallest objects, making Asteroid fields were you need to fly carefully around to not hit anything non existent. (and well even if there was such a thing, flying all the way around it would be easy) To name a few :D
Progressive break ups that occur over months are the worst kind...
They're called primaries.
Gets popcorn
this made me happy.
I have had a few of those myself
Progressive break up!? No, please don't go Flo!
But the “ make up sex” during the process is great.
Fast = "in under a million years"
Another possibility is to hollow out the asteroid and build a spinning habitat inside. The outer asteroid layer acts as a shield, and could be mined for all the water and other materials. Also, if this hollowed area could be pressurized you could plant crops and such. A very slight spin would allow for water to go down and plants to grow up. Now too me, this is far more realistic and interesting.
I've been much more of an advocate for the O'Neil cylinder inside the asteroid idea. Though... you do have to have some strong magnetic bearings to ensure your cylinder doesn't precess out of center.
Just the idea I had some years ago. I mean he's right questioning the need to spin up an asteroid. Is there any model available of such a design?
Found this after independently duplicating your comment. Precession is prevented by building counter-rotating structures attached to the habitat. They have equal but opposite angular momentum, so no precession.
Couldn't the whole structure just torque off the asteroid itself? The enormous mass of the asteroid would serve as the counter rotating structure to the relatively tiny mass of an air-filled space station. If you place the station at the centre the effect of the asteroid would be barely detectable.
I expect asteroids are going to be predominantly loosely packed rubble piles. Using the intrinsic rock as a shield will probably be about as effective as covering a bunker with packing peanuts.
I'm betting on a bit more structure from a combination of engineered trusses and bails of loosely consolidated raw asteroid material. Still going with an un-spun shield made up of bailed rocks and water tanks then connected to a spun habitat inside with magnetic bearings. Asteroids like Ceres or Eros would ironically be too big, carrying with them small but noticeable gravity fields. A habitat built inside a void would get the vast majority of its gravity from its own spin but then have the asteroid's gravity overlaid leaving inhabitants with a gently rocking environment. Everyone's soup pots would be self-stirring but furniture and dinnerware would be self-relocating. An engineered external shield would be uniform in mass netting out to zero gravitational effect. A shield wouldn't need to be especially overwhelming, a dozen meters thick combination of rock and water tanks would put up far more protection against micrometeorites and radiation than the Earth's atmosphere.
Habitats inside asteroid voids would not be ameniable to relocation. If Eros station ever got bored and collectively wanted to to experience the thrills of Mercury or hanker for a jaunt to Pluto it would mean thrusting all 34km by 11km by 11 km (6.7e15 kg) of Eros. A habitat with engineered shield would likely mass "only" around 1e12 kg, a featherweight compared to Eros.
All the tecnical details aside, they didn't spin those asteroids up to martian gravity. A major point in the series is that gravity on stations like Eros and Ceres is so weak that belters are having serious muscle and bone issues. They can't live in either martian or earth gravity. I always figured ceres and Eros had somewhere between 0.1 and 0.2g of gravity.
There's also visual of a bird literally floating after flapping its wings once or twice, so the gravity is VERY low
There is a scene of a character pour a drink from a jug. The stream shows exagerated effects of corriolis. I think this would indicate a very small radius station spun at high rpm. I seem to recall from the books too that well-to-do on Ceres could afford apartments on the edge of the station where the spin gravity would be highest and thus cause fewer health complications. Then there were the unspecified, expensive medical interventions that Belters could undergo to mitigate the health effects of low G, a rubbing point between Miller whose parents did pay for the interventions and other Belters. It set Miller apart as a privileged rich boy.
I can't remember if they specify it in the TV show, but in the book it's stated that Ceres is spun up to about 0.3 g, which is close to Martian gravity. The slums of Ceres are toward the "ends" and are closer to the axis of rotation so the coriolis effect is more pronounced. Most stations and asteroids that use spin for "gravity" have settled on something in the range of 0.3 g, however there are a lot of habitats on moons like Luna, Ganymede, Titan, Io, and Triton that just have whatever gravity the moon naturally has, and there are a few smaller asteroids like Pallas which were never spun up because they couldn't take the stress and so have almost no gravity at all.
They mention in the book that the outer layers have 0.3g
The more you go inwards, the less gravity you have (thus poor people tend to live inward)
@@ericjamieson Ceres natural gravity is already 0.27g
What do you think about the Game of Thrones world actually being a giant rotating space habitat complete with central fusion reactor?
I've never had time to read the books, but the TV show titles make it look like that.
I know there was at least one religious group who believed that instead of living on the surface of a sphere, we in fact lived on the interior of a sphere
en.wikipedia.org/wiki/Koreshanity
They had to come up with some rather complicated refraction mechanics to make the sun more correctly in the sky. If the GOT world were like this it would need something similar to create the sunrises and sunsets in the show.
Speaking of shell worlds, have you guys had the chance of reading Iain Banks' "Matter" ?
He did a few videos in ksp ages ago, before his channel blew up
gotta get Preston Jacobs in here
Universe Sandbox actually has Westeros orbiting it's 2 suns as an imbedded feature so you can get all the stats on it.
i always assumed that for the stations they dug out some of the asteroid/body and spun an cylinder inside it.
cheaper, youre mining the body anyways, and you're spinning up the cylinder not the actual body.
also i guess all that rock is a nice protection against that nasty space radiation, in my opinion that's the only advantage of digging a hole in an asteroid instead of building something on the surface anyway.
frischer bärlauch speaking of those nasty little solar rays i wonder if it's possible to put something near Ceres to block out the rads, like a nasa scientist (i believe it was) suggested recently. Then you could build habs on the surface. Maybe put up a nice little space elevator.
+Daniel Carter Well, why would you build a large space habitat like that, to shield workers from radiation and micrometeorite and provide them with artificial gravity while they mine the asteroid but wait, if you have to mine the asteroid first before building the habitat then how will you house them while mining and once it's mined, why would you continue to have to house miners? It would make far more sense to build a smaller habitat either floating nearby or a small centrifuge on or just below the surface rather than turn the entire asteroid into a habitat.
John Wang i never said a hollowed out asteroid with a cylindrical city made sense, I'm just saying that's how i always figured it was done. Personally I'd but a magnet in orbit to block stellar radiation and build bowl shaped habs on the surface and spin them to have artificial gravity. And you'd want a permanent base on Ceres because there aren't any satillites, it's rather small, lots of fuel, and it's larger and more circular than a lot of other bodied you could consider.
John Wang i don't see the point in a habitate on a planet or a dwarf planet or whatever if there is no atmosphere, you might as well sit in a tin can in orbit. However, I wonder how much radiation would actually be absorbed by an asteroid if it has such a dusty consistency
I would just say that it's not so much that rock isn't strong, so much as it's the wrong kind of strong. It's strong in compression, but this structure requires tensile strength, and rocks in general are indeed very bad at this.
Depends on the composition.
Plus nobody said that you can't reinforce or stabilize faults in an asteroid. The stations in ED all have massive struts holding them together from the inside.
+jodomo which is great and all, but if you have to fill the fucking thing with steel anyway why not just make the whole thing artificially?
Shell of dead rock to provide shelter (rock is great insulation from radiation and weapons), steel inside to give structure.
answer is fairly easy....mass is the issue,,,soo just hollow the thing out morons. remove like 4/5ths the mass....in fact they did on the show, they extracted all the water .
I always assumed that spacecraft were docking at the "poles", where the asteroid's spin was easier to manage
protomolecule can spin up an asteroid. protomolecule can also hold it together. protomolecule can do lots of things.
You sure, you wanna mess with this stuff? It gets out of control quickly...
FirstPersonStranger protomolecules, son
Major Dakka Coulda' gone pro if I hadn't joined the Navy!
Protomagicule
It would also protect against small meteors and micro meteorites
I had thought that in The Expanse they had mined out much of the interior or several asteroids over many decades, adding improvements to support miners as they went: air, water, waste processing, tunnel reinforcement, long-term living quarters, machine shops and warehouses, etc. So perhaps over 60% of the mass had been removed and what remained was of value due to those improvements. Still fantasy, and it probably adds new complications, but that might change some of the numbers.
Nice video as usual. I haven't read the books but recently watched the first season on Netflix. I kept thinking, "How'd they spin Eros up?", and, "Wait, it would fly apart, what's holding it together?". Then when it started talking about the same for Ceres i just decided to turn off my critical thinking on the subject and enjoy the story. With that much energy they could easily construct a very nice spinning habitat using asteroidal materials, ie organics and metals. In fact they could make lots of them.
It would be easier to just build a rotating space station than to spin-up an asteroid.
it would be alot easier to use a iron asteroid,,,to build a space station. melt it down and build what ya need. or at the very least just hollow it out mostly. like 90% hollow.
@@autopartsmonkey7992 i think asteroids have the advantage for 1 reason, easy radiation shielding, easier than you could get on a space station.
I think the reason for Ceres station being the way it is is because "digging" requires a lot less material than actually building something. Just dig and throw away some part of the asteroid and voila, you suddenly got space you can build a habitat on. The spinning part is to resolve the gravity issue. When you have a basically magic Epstein drive, that's not that hard
Yeah Scott, I'm with you on this. I think the reason for interest in asteroids, is mining them. What one could do, is mine the materials for building a space station,
rotating the station for gravity. It could be engineered for safety. After it is built, maybe one could sell the rest of the stuff you mine.
Scott, have you seen Isaac Arthur's channel? He's done a video on this. I would recommend his channel to any sci-fi nerd
I was gonna post this too. Isaac Arthur is SO good and more of the space-community should watch his videos.
+Herbstein Gotta spread the good word whenever possible :P
Honestly I avoid watching his content because most of what he does I might do in the future and don't want to be accused of plagiarism.
Understandable. This just means we have more superb content to look forward to :D
i saw his channel, he has really nice vids.
Does your kid think you're as cool as we all do?
His kid is probably like "my dad is boring he likes maths but he has cool computer games"
You can't possibly consider a guy who makes you do homeworks and eat your broccoli cool. Not at his age. The understanding of Scott's coolness will come later.
Almost certainly not
*Kids, he has two. And I think they trhink he's pretty cool.
that is actually a good question
Decades ago, Prof. Lionel Wilson (UK) discussed hollow asteroids as the common, result, of small impactors penetrating some depth before fully releasing their superheated vapor of impact hollowing-out the asteroid insides, expanding the looser rubble outer thickness, and depositing melt and vapor, brazing, sealing, and pressurizing, interior chamber 'walls'.
I think in the books they describe the tunnels that were the spin up tunnels, one shot engines of some not specified type. The books were long on concept short on details, probably for good reason. Sure, we could do like the earthquake proofing of buildings in California where you have rebar running through the length of the asteroid to help counteract the centrifugal forces but I think they are held together by the writers imagination ;)
Well, something to consider is that while you are digging the asteroid, you need to to something with the resulting material and one possibility is to "shoot" it out to push yourself (maybe engineering the orbit to be more stable or obtain particular rendezvous). The spinning still remain a problem, but lets go back to a smaller asteroid with reinforced structure, you are pushing a lighter and lighter version of the asteroid, to the point when you are mostly hallow, and the energy requirement to bring to "final spin" are greatly lowered.
Basically the asteroid became a source of resource in a convenient orbit, more than your ending base
I can't see spinning a hollowed asteroid for artificial gravity but I can see doing a cut and cover rail system around an asteroid so that you could have artificial gravity in what's essentially a train on the tracks. The reason for cut and cover would be for radiation and micrometeorite shielding
Or even better, use a Tunnel Boring Machine (TBM, instead of the incredibly labour intensive cut and cover.
Fast train. 473km/10mins 3600km/h but mag lev it maybe
@@jorgepeterbarton Tangential velocity would depend on the radius but nice try at seeming to sound as if you know something. Yes, it would be fast but you are in space and magnetic suspensions is more than sufficient, I would imagine permanent magnets on a Halbach array along the habitat pressure vessel and aluminium coils as the tracks thereby using Lawrence Livermore's Inductrack system as the materials needed are plentiful and there would be no need for cryogenic temperatures, just heat dissipation issues from the aluminium coils but aluminium also makes good heat radiators. Of course, it would be maglev as well as tension cables in the habitat as the habitat could go completely around the "track" hence the mag Lev would not be needed to sustain the entire weight of the structure even when spinning as the tension cables would do that, the magnetic levitation would only be needed to center and guide the structure so no contact is made, and quite frankly, as most of the forces would be in the tension cables anyways, even a mechanical system instead of maglev could be used as again it is only centering and guidance that would be involved and that would be intermittent. A mechanical system would just be more costly and precision manufacturing intensive than just setting up a Halbach array and aluminium coils. We're not talking about the precision supercooled maglev of millimeters of trains on Earth, just preventing a spinning ring from contacting what it's spinning in while in the microgravity of an asteroid. Normally, the habitat pressure ring should not require anything to avoid contacting whatever it's spinning in, it's just that occasionally it would need to be guided away.
I was sort of expecting/hoping you were going to build a hanger into an asteroid in KSP and spin up it's rotation via srbs or something and dock into it...
I'm so happy that you give so much exposure to The Expanse, it's the best space-y show since the BSG reboot in my opinion
4:34 I realy had to laugh at that point of the video. In under a million years. How can he make that sound so fast? That is ridiculous! xD
A bit of this is addressed indirectly in the books.
They do say that it took decades to spin up an asteroid (though I don't think they were talking specifically about Eros), and the Epstein drive is fueled by very small pellets, so it is phenominally efficient.
What isn't addressed is keeping the body in one piece and ejection mass. So in-universe, energy and time are addressed, stability and propellant are not.
My head canon is they use the rock itself as ejection mass. As it is melted by the Epstein drive, the magma itself is used to accelerate the drive. 3/4 issues resolved is good enough for me when the story is as good as The Expanse.
Warp Drive - Hyperspace - Wormholes - Transporters...yada, yada, yada. How Many Angels can dance on the head of a Pin? It's not called SciFi=Science Fiction, or SyFy=Science Fantasy for nothing folks!
The Epstein drive should be something close to Hawkins radiations.
@@Fridaey13txhOktober ?
"small pellets"=/="phenomenally efficient". Basically, it's magic.
phobos would make a nice equipment platform, with a molten salt thorium reactor. Don't want no stinking gravity, just a big gymnasium to play 3d ball in.
Its videos like this that see you being the only KSP channel I bother to subscribe to. This video is so much more valuable than some of these "look at my cheated ship go everywhere" channels.
so why not use the material in the asteroid to build a space station.
Scott, I think it's absolutely amazing how you can explain such complicated subjects(relatively complicated for us, who aren't educated like yourself) and explain things so we can understand it much easier. I have learned a lot from you and I appreciate that like you have no idea. I would imagine that if you had a Scott Manley when you were growing up, you would be far more educated than you are now(which is truly hard to comprehend). I wish you luck in everything you do. Thank you sir.
There is a common misunderstanding that asteroids are large rocks. In most cases they are gravel balls, there may be a large rock in the middle somewhere but it is likely that they are mostly gravel and dust cemented to the large rock(s). Even if you found a large enough boulder to put a base on you would be subject to a storm of loose debris bouncing and orbiting through highly erratic orbits. This would make it extremely dangerous to attempt to land on and would require the base to be buried deep inside the asteroid. Making it largely inaccessible. It would be a much better plan to do this on a planatoid like Ceres. The weight of the armor you would need to approach an asteroid would be less then the fuel required to land on and launch from Ceres.
In my opinion the best plan would be to build a space station that would be easy to spin and use drones to collect the material you are there for. A space station would be a lot lighter and could be driven around.
There is a common misunderstanding that asteroids are all the same thing. Also, Manley's projection seems to assume this trick is easier for larger objects. The opposite is true. With a maximum spin rate of 2 RPM, you can get useful gravity with natural materials, like basalt and granite. Nobody is going to try to spin up a slagpile. This is a "straw man" post.
you got a gift man, I actually understood when you started spitting math out, normally that's about when my eyes glaze over and I zone out. keep it up.
Well, if it's good enough for Scott M, I guess I best be checking out The Expanse.
Scott I find your physics / astrophysics lessons every bit as fun as the rocket science stuff, maybe more so. Thanks.
Be more practical to hollow an asteroid out and use the spoil to build a rotating structure inside the protective outer shell I reckon.
A pair of opposing O'Neil cylinders, inside that lovely rock shielding.
Circular train tracks on the surface, or in subsurfce tunnels, like a subway going in an endless highspeed circl
Yup. That's why in my sci-fi stories, space habitats hide behind asteroids. In other words, the asteroid always blocks direct sunlight and solar radiation from hitting the space habitat. However, in most cases I put a huge lightweight ring shape structure beside the space habitat and barely a sufficient distance away so the sunlight is not blocked from hitting it. Essentially this structure is just a ring [with internal web] that holds huge sheets of something like aluminized mylar at a 45-degree angle to the sunlight so the light reflects off and onto the habitat. Note that highly energetic particles will pass right through this material while lower energies like visible light bounce off and provide the habitat with illumination and a source of energy. A few other minor components are also required to keep everything stable (since the main asteroid has a tiny bit of mass and thus exerts gravitational and tidal forces on the habitat and energy reflectors.
9:40
> Oak
> 12 to 13 kilometers
Seriously? That's some tough wood.
Whole new meaning to "grow your own", isn't it? Look up "dyson trees" if you want an example of a wooden (living) space station.
Man this is amazing! You have videos on all question I had in the Expanse! #1 show for sure
what about hollowing out the asteroid first and spinning it up afterwards?
and you could use big mass drivers to spin it up and eject the excess mined material.
but then you still would have to spin up the mined material...that would undermine the whole idea of hollowing it out in the first place...you need to bring out the mined material fia conventional, far more efficient methods...
So what you're saying is hollow out the asteroid and use spacecraft to dump the mined material somewhere, then spin it up using fuel you brought from earth? That doesn't make any sense.
no...i am saying hollow out the asteroid without spinnig it, removing the mined material with, lets say conveyor belts or push it out or give it a little push and let it drift out in microgravity and then, after removing most of the mass of the asteroid spinning it up
and who knows from where you get the fuel, doesn't need to be from earth at a time where you are technologically advanced enough to hollow out an asteroid...could even come from the mined material itself...
I keep waiting for another episode of GPP playthrough - But happy to see a video all the same!
Ceres isn't even an asteroid, it's a dwarf planet. Why the hell would you think spinning that up is a good idea?
it is both
Thanks for the video, Scott. I remember talking to you about the issue on reddit. I love the Expanse, too, but sometimes it's just fun to pick it apart :)
Rock is also particularly ill-suited for this application, because it's at its weakest in tension (which would be the dominant stress mode in this case). Alternatively, what about Niven-style blowout asteroids? His suggestion is to use nickel-iron asteroids, balloon them using steam pressure, then spin them up. Would this be plausible with smaller asteroids, or is it another case of him failing to consider material strength a la ringworlds?
Separate question: Sci-fi authors love space elevators, but even assuming you could create a suitable cable or ribbon, how would you actually get the whole thing in place to begin with?
I want to know the cable thing, too.
Ignoring engineering details like material strength and resonance modes?
Conventional launch of bootstrap material, then build the tether down from geostationary orbit while simultaneously building the counterweight up.
Once a minimal tether is in place, you can haul additional material up the tether and reinforce it.
In Niven's books, humanity has infinite cheap energy. So heating a metal asteroid up to melting point and inflating it is plausible, in his fictional universe.
Elevator cables: elevators are only going to usefull in fairly high-gravity environments where rockets are big and dangerous. An elevator at Ceres or Eros would be easy to do but wouldn't save much over using low-thrust rockets. On either you could do all your launches with catapults.
Getting an elevator cable would be just a matter of fabricating it in space. The minimal cable, only large enough to accomodate a modest climber would still mass around 100,000 tons, close to 1,000 SLS launches. That would still leave the challenge of seamlessly splicing the 1,000 or so cable sections in space. An easier approach would be to source all the raw materials from a carbonaceous condrite and fabricate the whole carbon nanotube or graphene cable in one continuous process. Attach an archor to one end and gently lower it to the surface of the Earth. The only necessary thing it that the center of mass of the cable is at geostationary orbit above the point where you want to anchor to on Earth.
Kevin Shepardson,
A stationary space elevator is assembled in orbit. Preferably at synchronous orbit but, perhaps, the structure is gradually moved outwards with ultra-high efficiency engines. The center assembly (micro-g) hub is supplied with spools of fabricated graphene tube segments. Splicing and composite layering is done until the ribbon is ready to deploy both up (out) and down (inwards) simultaneously.
The initial elevator fabrication must reach full length before it is ready to be lowered into the atmosphere and anchored on land or sea.
Until then, the excess length is stored on spools and/or the ribbon cable will be deployed folded over a pulley at the weighted lower end.
With folding, the true endpoints can be maintained in the center micro-g fabrication hub until self-mass and layering requirements preclude this.
There are several harmonious ways to continue fabrication. One is to install fabrication plants and/or habitats at both top (outward) and bottom (inward), which need to be weighted anyways. The inner end will eventually experience near surface gravity, even while above the atmosphere.
The second is to fabricate and deploy the actual ribbon endpoints from the hub. Of course this requires folding at the weighted ends.
The third is to shuttle along the existing structure, bonding new composite layers.
The outwards section can be shorter than the inwards section if a greater mass is maintained at the outer end. Both must be adjusted to maintain balance so that the micro-G fabrication plant can operate correctly.
A side effect of lifting all mass to the geostationary point is that a large amount of potential energy is stored. The act of deploying the cable will allow this to be converted to electricity, for example.
"SciFi: We love the cool ideas, but sometimes we don't think them through before writing them down" is a brilliant summation, man!
Because if we write about the science more than about the fiction it would just become a science paper.
Maybe you don't need that much gravity. I think the minimum would be just enough to do gravity-assisted bodily functions.
Has NASA performed any study on low gravity pooping?
dkosmari As far as gravity goes you can go as low as you want for the most part. There are some exceptions, but mainly the return to normal gravity is what causes problems since your body quickly adapts to microgravity.
Astronauts on the ISS are actually really comfortable until they return.
I want to know if I can pee and poop without needing to vacuum it out of my orifices.
Yes you can the ISS has a toilet. Actually shouldn´t be a problem to live in low gravity as long as you don´t plan on returning to gravity ever. Well in the Expanse they came up with fancy medication that keeps your bones strong so if you have that it might work no problem.
You can poop just fine in zero g. Here's an experiment. Stand upside down on your hands and try to poop upwards. Piece of cake. If your bowels can overcome negative g's they can surely overcome 0 g.
Thank you for that... unpleasant imagery.
I thought this was called the Poynting-Robertson effect, but i follied, the effect is restricted to the degradation of angular momentum on dust due to radiation pressure rather than adding spin. At least you made me correct myself on something I learned about years ago!
How about just ice vaporizing when hit by the sunlight creating a thruster? Or maybe this asteroid was too far away to get that hot?
The asteroid belt is about as far away from the sun as you can get and still primarily use solar power[1] so maybe? The question is is it worth the time and energy to try something like that or do you build something that you know will work and fly it out there.
[1] I know we've sent solar powered probes out farther than that but I'll take a RTG at that distance any day of the week.
I was talking about natural the spin up process, if vaporizing ice might cause the asteroid to spin, but I guess focusing sunlight intentionally onto an icy part of the asteroid would be a very cost effective way to do it assuming you have large, cheap and accurate enough mirrors to do it :)
And now that I'm a little bit less tired I can actually calculate the distance at which this can occur naturally:
It would be using Stefan Boltzmann's law and some algebra we get: r_asteroid^2 = T_sun^4 * r_sun / T_boil^4 (We got this by calculating when the amount of energy radiated per area of an asteroid being at boiling temperature is the same as the energy received by the suns radiation). Plugging in some numbers that gives us 166 805 431 km or about 1.1 AU, so yes, they are too far out for this to be a thing. However liquid water does still evaporate slowly, so plugging in the freezing temperature of water instead gives us 2 AU. Still not far enough out, but some asteroids could come close to that distance.
Still, using mirrors to do this if there's ice on the asteroid would be viable, maybe even a way to move the asteroids :) Then you wouldn't need to transport anything out to the asteroid to move it, you can just shine the "sun death ray" on it in very precise locations. You would need some very large mirrors tho, but that wouldn't be much of a problem, they would be pushed away from the sun slightly but easily compensated for using small thrusters, or you could position the mirrors in such a way that the small distance your pushed doesn't really matter much, eventually you would have to compensate for it tho if you plan on using the mirrors many times to move many asteroids. In practice you would probably still have to send probes to the asteroid to determine it's exact center of mass, where ice is etc etc so you know where to shoot on the asteroid. You might also need to send up mirrors to be able to shine light behind the asteroid. I think Isaac Arthur made a video on this, not sure tho :/
Well, ice still sublimates at very low temperatures, specially in vacuum, so I wouldn't discard this possibility.
If you look at a phase diagram for water you see that you'd have to get above 200 Kelvin at a minimum to get vapor. Plugging that into the previous equation gives us about 3.8 AU, so yes, there are asteroids inside that range within the asteroid belt it seams (the belt between mars at around 1.5 AU and Jupiter at around 5 AU)
If you're talking about "stray particles sublimating" such as evaporation experienced here on earth even tho you're not above boiling point, I don't think this would have a very big effect in a crystalline structure such as ice but I could be wrong, I just thought the temperature distribution in the substance thinned off very quickly when you get down to lower and lower temperatures allowing for extremely few atoms to sublimate.
Going further deep in this topic, one photon from the sun has more energy than the hydrogen bonds connecting each molecule in a crystalline ice structure. So I guess exposed ice will sublimate, no matter at what distance from the sun.
I think this mechanism is better called ablation than regular sublimation, but... Let's go to the numbers:
The hydrogen bond energy in ice is about 4.5 kcal/mol. With 4 bonds in a crystalline structure, this gives an energy of 0.78 eV per molecule.
Even a low energetic red photon from the sun, with a wavelength of 780 nm, has an energy of 1.59 eV.
Of course some of that energy is transferred as heat to the ice (and I have no idea on how to estimate that), but I believe there's a significant sublimation rate. Maybe enough to spin an asteroid in a couple million years.
Not only did I learn some good stuff about Asteroid Space Stations... You just showed me how to modify my racks to hold my records! Cheers mate!
I remember reading KSR's Red Mars trilogy and he has loads of hollowed-out spun up asteroids flying around. It always struck me as impractical, if not totally infeasible. Interestingly in the beginning, when they're setting up a colony on Phobos, they do build a large track that runs around the entire surface to give a sort of "refuge" where they can get into some gravity rather than having to live entirely in milli-gee conditions.
That "train" idea was exactly what I was going to post...and, although I thought it was an original idea, I read the first book of that trilogy a long time ago so my subconscious probably just plagiarized it. To go a little farther - since I can't recall if they did it in the books - I'd say hollow out the interior for use as a micro-g space-dock for the ships, slap rails around the outside, and basically make a space-version of that carnival ride where you get spun around-and-out in little seats that are tethered to a spinning central pole, in this case using nanotubes and relatively small pods to keep the math realistic ("extended stay hotel rooms" for you and your crew to get some g's, go to meetings with others, etc.).
Now that I think about it, Neil Stephenson's recent book Seveneves does something like that, and AFAIK he actually did the math/got help from people that could do the math for him. Damn my memory once again! :O
I don't think hollowing the interior to make an spaceport has any practical benefits over building the port at the surface.
It makes sense for several reasons:
1) Assuming you're mining the asteroid, you've got to remove material from _somewhere_, and I see no reason why you wouldn't construct mines relatively the same in space as on Earth (i.e. "dig where what you want is"...which is likely to be inside, not on the exterior of the asteroid) and
2) Kepler Syndrome is already a known/potential issue around Earth; I can only imagine how bad it could become around an asteroid that's being mined/constantly visited by ships/etc., so
3) by keeping docked ships inside of the asteroid, you not only have much better control over debris, but you effectively shield the ships from all external sources of damage as well.
Tbf, by the time we see the asteroid colonies, like the one that goes off into interstellar space, they have much more advanced technology.
Enough to have a city on wheel on Mercury, undersea ones in Europa, fusion power, and they apparently can make diamonds for peanuts, given they had dams of the stuff on Mars.
Larry Niven had a slightly different method for creating asteroid stations in his Known Space books. They would take a reasonably pure nickel-iron asteroid, put a heatproof balloon in the middle, then use solar mirrors to raise it to melting point. They'd inflate the balloon up to the right size and shape, then let the whole lot cool. Seems more reasonable than just hollowing out an asteroid, and the original asteroid doesn't need to be anything like as large to produce the same size habitat, either.
The key is to spin the internal structure relative to the surrounding asteroid material, then correct the outer spin of the asteroid to keep it stably non-spinning with exterior boosters.
I haven't put any thought into this other than the idea just popping into my head, but in the same way a longer wrench provides more torque and makes it easier to turn something, would it be significantly different (Or any different) if the engines were 100KM off the surface and attached in some way? So you'd essentially be spinning an object "500" KM in radius, but with the same mass? Disclaimer, I am the opposite of a physicist, whatever that would be called.
sonnder you'd need an extremely strong frame system to handle such torque.
sonnder I wouldn't think so, because with a wrench you're trying to overcome material sticking forces, which is why more torque is helpful, but there isn't any such forces in the vacuum of space. The only force to overcome is this YORP effect mentioned.
It becomes a relatively simple matter of just imparting the needed momentum.
Yes, that would greatly reduce the thrust and/or time required to achieve the proper spin rate. And you would not need a frame system to handle the "torque", you would put the engines on a 100km tall tower than run a cable from the top of that tower to the horizon. The cable would be under tension pulling tangentially to the surface, the tower would be under compression.
you gotta think outside the box. this is a case of mythbusting similar to that infamous mythbuster show where they claimed pirates couldn't possibly glide down sails with swords simply because the tv show crew couldn't physically do it. there are many crazy physical feats people do that blow my mind. so for the asteroid spinning, you could hollow out the asteroid, cut it into big chunks and spin each smaller chunk separately. bring the asteroid back together and stitch up. tada!
I think what you are explaining is exactly why you have to use rebar in concrete.
Have you ever watched Isaac Arthur's videos?
That's actually a really cool format, and could even take the form of a ring or even an O'Neil cylinder encapsulating the body
"its a rock, its completely full of rock" that was really helpful, really needed to know that
Well at least we know there won't be any Metallica
Hi, guys! This video puts me to idea, that big space station (death star particularly) has a HUGE inertia momentum, and if it is not positioned to target initially (see Rogue One movie), it... WILL SPIN ITSELF OUT (100 km diameter claimed multiplied by reasonable speed of rotation gets linear accceleration, that no carbon nano-tubes can withstand) Bye-bye, Death Star!!!
PS. Scott, I've started to look your channel a month ago, when started playing KSP. Man, you're doing really cool things and videos! Thank You!!!
Wait a minute, forgive me if this is a stupid question, but given Earth is spinning, does it also produce a force and reduce the pull of gravity to some degree?
Hyrum Diesen yes! But only very sightly. I feel like Vsauce has brought it up before. I think it's a difference of 1 lb or less.
Yes! That's why it's better to launch rockets closer to the equator.
For fast weight loss, travel from pole to equator!
Fabrício Lara you’d lose more weight walking the distance, than you’d lose because of the spin
Just the flotation effect of gas pressure on the volume of our bodies negates more than that I'd say! Just that we don't notice it since we weigh in with that already subtracted. How much more DOES a human weigh at earth sealevel in vacuum compared to in atmosphere ?
thank you Scott Manley. Great stuff. a fun mix of Kerbal, sci-fi, and hard science discussion, all in a Scottish accent. I wish I had stumbled across your channel earlier.
could you wrap the asteroid in a giant net / wire mesh type of thing, would that be enough to keep it together?
For Ceres it would have to be about 30km thick and made of perfect carbon nanotubes.
oh god, that's a fair amount alright
MrNuclearturkey thats an understatement
I did the numbers for something like this a few years ago for a story I had been working on, just growing lore and such out of "What if we had this space travel tech..." kind of thought experiment. A big part of it became a "Because we can!" sort of thought process...
- While mining useful materials from a very large asteroid you give priority to minerals that lie within a target structure space - These spaces then become room for reinforcement structures and living space.
- While processing the materials, useful refined material is ejected at set points by mass driver, while waste material is ejected at other rotational positions... The energy of shipping your product and disposing of waste material then automatically inject rotational movement into the asteroid as a whole.
- Eventually you have a shallow gravity well deep space location that has 0.7g or something, and natural armour such that it becomes a non-trivial energy level to destroy or even be able to do much in the way of major damage, even if defensive weapons systems fail.
- A rotation structure also offers defences against long duration directed energy attacks - Some neat sweet spots develop at the right rotational speeds, mass, and materials - You increase the required energy to really do anything since by the time the energy weapon has heated the surface enough to start really changing anything then it has moved around to the far size and can naturally radiate the energy back into space.
- A non-trivial rotation speed also gives handy attack/defence advantages, as weapons/access ports are now moving more rather than being more stationary targets/launch points.
I guess you could try reinforcing the asteroid to hold it together better...though at that point, you're probably better off just building your own space station and mining some non-spinning asteroids.
Did the math on that, watch the whole video.
Great video, as always, but I don't think the concept of breaking strength could be applied to this problem directly. Imagine the spinning rod (around one of it's ends). Centrifugal force will vary across the rod length, unlike gravitational force used to derive the breaking length. So, to derive maximum length of such rod rotating with angular speed omega, we need to integrate. The answer (if I didn't make some dumb mistake) can be put like this: if we want to have an acceleration of 0.3g (like Eros in the Expanse) at the end of the rod the maximum length will be (breaking length)/0.15 or approximately 6.7*(breaking length). So to support such rod with length equal to Eros radii the rod's material need to have breaking length about 1.3 km. Of course Eros is not a rod and even not a ball, so one need more complicated analysis, but i think it's a great approximation that shows that the stresses aren't that big, and maybe if one chooses the rotational axis carefully, this is possible even without structural modifications.
For Ceres the breaking length needed is about 70 km, still quite impossible with rocks.
And of course spin-up still requires insane amounts of energy
But if Ceres is 0.029g and barely stuck together what happens when 0.3g is applied in the opposite directions?
Gotta love universal size scales where an object that is 11 km by 35 km is considered to be "small."
The Earth is considered one of the small planets in our solar system... at 12,750 km in diameter. Eros at 34km by 11km by 11km is roughly a billionth the volume of Earth and about 10 billionth the mass. Our sun, just 1 of about 400 billion in the Milky Way, weighs in at 3 million times that of Earth. So, yeah, Eros is small.
@jonny j - clearly, Lenard Segnitz is *agreeing* with DahVoozel.
Earth is the 5th largest planet and the largest rocky planet so it’s hardly small
Hey Scott! nice! destroying The Expanse like that :P ...Did you do one about the Elysium space station? i was thinking would that design really work? how fast would it have to spin to hold the atmosphere in place and wouldn't the radiation be a huge problem
There's also the problem that a lot of asteroids are more like piles of rubble than solid rocks.
To touch on your final thought of an artificial gravity generator on the surface, that's what I was thinking throughout the video. a corridor placed at an entrance to the asteroid that would be stationary with a massive bearing at the end where it connects to a large docking bay or what have you, the bay could rotate inside the asteroid to generate gravity. To counteract whatever destructive force that artificial gravity would cause on the asteroid that docking bay could be placed inside a set of rings spinning in the opposite direction. Nullifying any gravity shift between the rings so no amount of artificial pull or rotation would be transfered to the outer shell causing the asteroid to collapse on itself or break apart.
I don't know a lot about astronomy, so I'm a bit proud that it only took me like 200 milliseconds to figure out that differential reflectivity could be the cause of an increasing rotational speed.
i dont why exactly but i think i love this video the most of all your videos i have seen so far.
The concept of steroid bubble worlds is many decades old. A model of such was featured as an exhibit at THE GRIFFITH OBSERVATORY over thirty years ago.
God dame it Mr Manley sir stop smashing my space trucking dreams with your factual science mathematics oligy stuff
You mean like the touch and go cargo planes full of gold bars.
I definitely found this interesting. There is logic to your explanation. Thank you. You are awesome.
I never thought they spun the whole rock up. But rather tunnel into it, build a space station inside it and spin the Space station up inside the rock.
This is something I've been thinking about whilst reading the series.
All they said was it took a generation for engineers to figure it out. And they note that there were no surface pebbles. But other than that, no details yet.
I recall Dandridge Cole and even Ernst Fasan (lawyer) were talking about using astroids as outer shells, while the rotation would be only applied to the inner cylindrical structure.
it makes more sense to hollow out an asteroid, build the space station inside the hollow asteroid, and spin the can inside for gravity. you would have less mass to move, you could easily build a dock accessible from the central axis for cargo and personnel transfer, and you still have a lot of mass from the asteroid itself for radiation shielding. you can even use the overburden from hollowing out the asteroid to help protect the dock whether you fuse it thermally or with some polymer binder.
This was pretty much my exact thought when I heard of the concept of Ceres from the Expanse. It went like this "The writer is not very well versed in physics if he thought something like this would work at all and not tear apart an asteroid,".
Even I knew that, and it isn't like I'm an expert. I work as a chef.
First example of an asteroid based space station that I ever came across, was in one of the first SF books I ever read as a youngster (oh how the time has flown)...
VENUS EQUILATORAL.
Science in it is of course somewhat rusty by now, but what counts the most was the internal consistancy of the stories.
Damn good.
Nice analysis. One of the more implausible things I found with The Expanse series was how massive all the ships are. I would expect our future space infrastructure to be much more gossamer. Mass is expensive in space, and cuts into the bottom line. Their ships remind me of ocean going vessels, which can be massive and cheap to operate, since they have all that water to push against and they don't go very fast anyway.
They mine huge things and have inexhaustible fusion engines.
Now you have me wondering just how much energy would be required to begin to spin a space hotel, or an O'Neill cylinder.
Self support length as shown in the Wikipedia table assumes 1G acceleration and constant cross-sectional area. Objects that taper from top->bottom will have higher critical lengths, as will objects seeing
I thoroughly enjoy these science talk videos. Keep'm coming. =)
Suppose a tunnel boring machine has excavated a circular tunnel of Van Braun-space wheel dimensions. Place railroad track on the outer radius of said tunnel with interspersed linear induction motors. Operate pressurized railroad cars on the railroad at speeds commensurate with the ring-rail's dimension and desired gravity. Use them as residential/sleeping compartments to limit zero-g exposure. Operate the ring-rails in pairs to cancel out rotational effect on the asteroid. Operate three orthogonal pairs of ring-rails to intentionally control asteroid rotation.
Scoot Manley, i watched your video and got a good solution who he did not get cover. It is to create a ring of highly tensile strength material around Ceres equator in order to resist any Yoke effect. If the idea is to spin it, the "equator line" will probably be where the centrifugal force is the biggest one, so my focus will be to calculate there. Also i will approximate every ring as a cylinder with height as (h), but that will matter a little.
Ceres is an asteroid with radius (R) of 482 km, density (p) of 2.7 g/cm and gravity of 0.28 m/s^2. Its perimeter around equator line is 3,028 km, which is 7 times lower than the Great Wall of China (21,196 km). In the show Ceres have spin gravity (sg) of 0.3 g, equals 2.94 m/s^2
with angular velocity (w) -> sg = w^2*r -> w = sqrt (sg/r) = sqrt(2.94/482000) ~~ 2.4 E-3 rad/s. Angular velocity is constant over all the radiuses.
The centrifugal force from the asteroid requires us to integrate, cause the centrifugal force is a function of the radius, and we need to sum all the rings from the axis of rotation to the outer radius (R), so it will need to be an integral and calculated as -> dFc = m*w^2*dr = p*Volume*w^2*dr = p*pi*r^2*h*w^2*dr With 482000 < r < 0
Fc = p*pi*h*R^3*w^2/3.
Since tensile strength (s) is s = F/area, the material needs to resist the Centrifugal force, and the area where it makes contact could be approximated to Ceres perimeter * height = 2*pi*R*h
s/area = F = Fc. -> s = Fc*A = p*pi*R^3*h*w^2/3/2*pi*R*h = p*R^2*w^2/6
The material need to resists to: (2700 kg/m^3) * (482000) ^ 2 * (2.4 E-3) ^2 /6 = 650.48 MPa.
650.48 MPa Is well inside plenty of materials that we have. A High strength steel alloy got Ultimate Tensile strength in 760 MPa. Stainless got 860 Mpa, Maraging Steel (an alloy with nickel, cobalt and titanium) got even to 2500 Mpa!, and that is talking only about steel. Even talking in a shear stress perspective the perspective doesn't change, since shear the composite material of steel + Rock have a good shear resistance.
In other words. It was a good exercise on Engineering skills and if that show made me try some, im glad. Hope you like the answer. Have a good day.
I see someone already mentioned this, and has a discussion going, but I'll say it anyway, here, because I would have to read all those posts to join. I think it would be better to carve out an area for a space station inside an asteroid, and just have the station itself spin. The asteroid would be a great shield against all that nasty stuff that flys around in space. Ever heard of an “OMG particle”? They're a rare kind of cosmic ray. There are of course, many less extreme, but more numerous cosmic rays, and plain old radiation from Sol to worry about. And those tiny bits of high velocity rock are problematic for a naked space station. As I learn more, I find it increasingly likely that things in space will be built mostly by robots.
You would not need to rotate the entire asteroid. A simple method would be to house a really big cylinder shaped habitat / working area that can rotate freely inside a housing/cage/frame that is located inside the asteroid driven and suspended by electromagnets (assuming resources and energy needed would be available). The habitat could be entered and exited through a gyro/gravi-lock system located at the centre of the cylinders rotation, to enter the hapitat the gravilock is enetered and then spun to match the rotation of the 'Habi-tube' to exit the gravilock is entered and spun down to a stop and then exited. Not all activites would require gravity especially working activities... The Habi-gravitat would be like going home after work where people could experience earth or even heaver gravity between work shifts. Those working as controllers, workstation operators would stay in the gravi-habitat most of the time while those working outside would be there during downtime.
Building a giant ring around an asteroid and connecting it to the asteroid with a few support structures, you could gently but relatively quickly spin up that ring using simple electric motors and solar panels. That would possibly be one of the cheapest ways to spin up such a gigantic structure.
One could also do the inverse of this, like creating a spinning cylinder inside of the asteroid. That would leave the asteroid as a shield and a place for solar panels. Doing this would allow you to start very small by boring a simple ring inside the asteroid and start by spinning a few capsules to serve as an initial base of operations. You can slowly add more capsules and continue widening the ring to allow for more space as needed.
The Expanse: the best darn modern space show out there! Period!
I love the idea. In the long run would be great. Kinda reminds me of a movie I saw recently. Around the end of the movie, they showed a hollowed out asteroid being a space colony (I'm sorry, the movie title escapes me - maybe someone would know, something about a black hole, made in the last 15 years). Plus one added feature, it would provide additional protection from the space elements (cosmic rays and other radiation).
IIRC in one episode of The Expanse you hear one of the stations flight controllers say they were going to take over control, I think it was season 1. Would it be easier for someone on the spinning station to maneuver in the ship trying to dock?
Landing a vessel not designed to land is such a kerbal move
Thanks for all the fun food for thought you provide, Scott. Here's some dessert for you to enjoy:
Since we're talking improbable projects here, let's go whole hog and really optimize it. I mean, why spin up and live on something solid when you can spin up and live in something hollow instead? More living space on the inside surface, with convenient docking at the zero-gee zones at each end seems a lot more preferable to limited surface domes at each end of a "peanut". Gravity for babies to develop safely in mom's womb also means an actual Belt civilization becoming a tangible reality.
Larry Niven had the right basic idea: bore a hole through the long axis of a mostly nickel-iron asteroid a few kliks long by a couple wide, pack it full of water ice (all you could ever need or want can be found free over at Saturn), seal the ends back up, and then spin it up with laser-pumped diffusion mirrors trained on it to heat it evenly and soften the body of the asteroid. After the ice in the core turns to steam and the asteroid gets soft enough, the whole thing suddenly expands like a bubble from the core pressure creating a very large living space where the ice used to be.
Of course, heat resistant exterior bracing will be required to prevent blowouts and to restrict the overall expansion as well as fine-tune the shape of the asteroid from say, peanut to cylinder for a more even structural mass distribution (and easier docking), not to mention the sheer amount of time required for the passive heating and cooling processes. Yikes, even. Right there is the deal-breaker.
But, by the time we're ready to attempt an engineering project of that magnitude, the tech needed for the bracing and the superheating/cooling required to make the deal-killing time factor manageable and the project worth tackling at all will most likely also exist. We might even have working gravity generators by then that would negate the need to spin it up at all - slow it back down to a stop, clamp them on and fire them up, done. But, wait...
With all that tech available to us, why not just build a habitat instead? Well, I personally prefer "natural" gravity to the type generated by a device that could fail at any time for any reason. Thicker outside walls are nice, too. If we're going to be having babies up there, I sure as heck want them to be as safe as possible, so a nice thick asteroid wins that contest every time. Murphy is the God of Space, after all.
Cheers, mate. =)
There is one way to solve many of the problems you spell out in one go...
First, use the ones you "don't want," the rubble piles, but reshape them first, by wrapping them in a sheath of wound fabric that is shaped as you like, but that has room in it as well for the later tunnels et al. In fact, you might even inflate separate balloon shapes as well, to carve out the space inside a bit. So once you have an "enshrouded" body, you then spin it up, shocking the pile at the same time, to let the outward forces start putting the matter into a different configuration, in the process reshaping the dust-berg into a BALANCED spinning shape to start with. THEN, once the berg is completed, spin it slowly under your solar concentraters, to fuse the outside, probably leaving the shroud in place.Then proceed with the finishing, after those internal voids you left exposed to space cool the sucker down...
Asteroids are for materials and possible industrial/military facilities which you can add smaller gravity blocks onto as needed. O'neil cylinders engineered to be as lightweight as practically possible with safety and cost in mind are for spinning up for artificial gravity and large sacale population settlements.
Best regards, Mobile Suit: Gundam
you could hollow parts out of the suface and insert a spinning station into the surface, like the drum of a washing machine.
you would have exterior entry for spacecraft etc, and interior entry to enter asteroids surface and interior structures
inside the asteroid the station would be protected against radiation and smaller impact events,and would have easier time to sustain normalized temperatures.
I think it was a Larry Niven story that had a company using mirrors to focus sunlight on asteroids to heat them until they were molten, then inject gas in them to make gigantic glass globes to live in.
From your presentation here, it sounds like this just would not work as he described. Which in retrospect makes sense. The impurities would crystallize in the glass and weaken it.
In regards to the spin-up time, it's possible that they built the station first, to eliminate mass, and then spun it. I don't know how expansive the station is but it seems like that would do a great deal to reduce the thrust required.
Well, that makes the Eve Online asteroid stations the most accurate looking - as they don't spin. However, I believe Eve has gravity generators for stations and ships, so its not needed anyway. :)
At the same time, you've discounted Niven's explanation for how Spacers kept fit off Earth (using an asteroid as living quarters for children while growing up). Though you also have a potential solution for other structures like Rama and the Ringworld. :)
Impressive amount of implications for (what appears to be) such a simple idea...
I always liked to think the Amarrians were the only ones with graviton based tech. While the Matari just kinda lived with out. That is, at least, before the cultures started "interacting".
Clearly makes more sense to mine and process the materials on asteroids to build large spinning space stations instead.
If I remember correctly, there's an idea in an alastair reynolds book that's something along the lines of essentially shrink wrapping an asteroid in some super-strong membrane to stop it from spinning itself to bits.
Space is just so alien to us, we forget all the small important details that make the difference
Ideas like:
>Getting rid of heat in a void thats super great at islationg and also bombing you with radiation.
>Not hitting small near lightspeed particles when flying around on long trips.
>How fitigh in a 3D plane with km of noting between you and the enemy makes close combat for the most part stupid.
>The huge distance between even the smallest objects, making Asteroid fields were you need to fly carefully around to not hit anything non existent.
(and well even if there was such a thing, flying all the way around it would be easy)
To name a few :D
Scott saying "let's do the math" is the final boss of making realistic sci-fi movies