This is NOT how you make Artificial Gravity
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- Опубліковано 27 тра 2024
- Today we're talking rotational stability and Artificial Gravity! This video has been a long time coming, and not just because it took 47 hours to edit, I took my first pass at this script about a year ago but wasn't sold on the final product. A very busy year later I've finally decided to cut the video down to a (slightly) more simple discussion about rotational stability in the context of artificial gravity. Nevertheless, this ended up being my longest science video ever, and definitely one of the most taxing for my ten-year-old computer.
I think these are some of the best visuals I've done even though they are still fairly simple, but there is still so much to talk about. I did a lot of research for that first draft, including how you can perform maneuvers while spinning, and even a way to jumpstart the rotation using gravity gradient stabilization.
Enjoy!
Starship SN10 Footage is used with the permission of Cosmic Perspective:
Video: • Starship SN10 landing ...
Website: cosmicperspective.com/
Thank you Ryan!
Intro Music: "Tornado" by Wintergatan
This track can be downloaded for free at www.wintergatan.net
Free License to use this track in your video can be downloaded at www.wintergatan.net
Thank you Martin!
Main Music: Lone Wolf by Dan Lebowitz
Available in the UA-cam Audio Library
Outro Music: "Blast" from Bensound.com
(0:00) - Intro
(1:31) - What is Artificial Gravity?
(2:41) - Small Radius AG
(4:44) - Large Radius AG
(5:26) - Single Starship AG
(6:39) - The Rotational Stability Problem!
(8:51) - Multiple Starship AG
(12:05) - What if the Tether Breaks!?
(14:55) - What's the Best Option?
(15:43) - Outro - Наука та технологія
Centrifugal force isn't just about health. It is also about hygiene. Water and dirt going "down" might make cleaning easier and reduce the risk of inhaling dirt.
Hygiene is just about health.
@@jbigbmofo Hygiene is also about disgust.
Disgust is not in the definition for hygiene, health is in the definition.
good point, it makes it a maintenance issue aswell, pleanty of stories, fictional and real of floating debris getting into equipment etc. (and not having to deal with zero G toilets!)
@@jbigbmofo Hygiene is more so about cleanliness, I think that's what Brandon may have meant to say. But regardless, words have usages wherein they have meaning, they don't intrinsically have meanings. We give words meaning. Kestralwings was making a distinction from health where hygiene is more appropriately used, even making an example were hygiene threatens health. personal hygiene, food hygiene and environmental hygiene are all forms of hygiene.
I think an advantage of whole ship gravity over short radius is crew sanity, it would feel a lot more comfortable and natural to just have 'gravity' all the time.
Uh huh....remind us how many of the astronauts on the space station have gone nuts with no gravity at all.
@@sleelofwpg688 I'm not saying you go nuts without it obviously, I'm saying it would feel better.
Not to mention that in theory lower g for longer would be about the same as higher g for shorter periods.
@@sleelofwpg688 none because all of them were specifically picked for being mentally strong not just due to the stakes involved in space travel in general but also because prolonged periods of time in a 0g environment requires a strong will and discipline
@@sleelofwpg688 mental health is not just relevant when the risk is complete insanity.
The cool thing is you can basically simulate this VERY accurately in Kerbal Space Program....as long as the kraken doesnt get to you
bold assumption 😂
kraken always comes, there is no exception
i think matt lowne did it before if i remember it correctly
just don't go 2km away
The Kraken is here.
Just looking at the small centrifuge, it looks like the most likely issue with the pressure in the eyes is that there is a force gradient from the feet to the head. The surface tension of the liquid below is pulling it down slightly but not meaningful force is being applied to the head. A large centrifuge has a smaller gradient.
Yep. This gradient issue is actually one thing I've seen as an issue cited for artificial gravity. The gradient can mess with balance. The head basically has no centrifugal force on it in thd small scale example
That was the first thing I noticed. There isn't hardly any artificial gravity forces applying to his head.
His head was basically at the center of that centrifuge meaning his head would have nearly zero simulated gravity effects. If a plumber can recognize that these "scientists" shouldn't have wasted time or money on that scale
@@montgomeryfitzpatrick473 except health wise that's really not an issue, our heart is more than strong enough to deal with a gradient like that, and the inner ear can easily be trained to not freak out.
sure it can be an issue for plumbing, but the human body is a tad more smart and adaptable than a bunch of pipes.
Also, this small centrifuge is quite cheap, maybe 200$ plus the sensors they already had for other experiments. And the rest is just concepts and CGI.
@@montgomeryfitzpatrick473
yes, that's the whole point. to evaluate if short gradients are enough by simulating a larger diameter by spinning the small one at a different rate. they want the head to be mostly free of forces so they can more clearly read other pressures in comparison.
This gives new meaning to the term "I'm going to take Starship out for a spin"
I couldn't wipe the smile from my face no matter how awful the pun so I gave it a like.
Oh, NICE. Very nice.
📣Badup boom!
Nice one, I see what you did there.
LOL
sure if spinning in space was actually a thing lol XD your position in a vacuum is a constant wherby the space around you rotates not you. so good luck taking your starship for a spin matey haha
@@jamiemarsden3823 Acting like you owned someone when you said some of the silliest stuff in this thread. Get some knowledge before doing that. You aren't really even arguing anything, just saying nonsense and then doing a Mic drop.
Really embarrassing, not for you, for the rest of us. We are embarrassed for you.
bro FINALLY. when i first saw that concept with the 3 starships, i was just thinking.. what??? its so overcomplicated when you could just use a massive rope. and NO one was talking about it.
my very first thought and solution to the art grav problem was just tethering two starships, and personally, i still think that's the best option. either way, i'm glad someone actually made a video about it. thank you.
That just sounds like it would be a waste of resources because you would have to launch 3 of them instead of launching one
The rope will flex and recoil inward requiring constant pressure outward, which will need to be balanced by the amount of recoil of the rope and it's period of bounce. It's not a good design. It would require more energy than a stiff system that can hold the forces that will be applied both in toward the center and out. With a stiff system you only need to keep it spinning, not spend energy keeping tension in the rope or fighting 'spring-back'.
@@nickjunes ever heard of centrifugal force? that is your energy keeping tension.
@@fxzn Yes but tethers are springs. The tension out will not be perfect. It will bounce and eventually the bounce will be strong enough to cause the weights at either end to start to drift in fowling up the whole system.
@@Mrpersonman0 I suspect every rotation will add to the resonance of the rope eventually creating an 'escape velocity' bounce that will cause the rope to become slack. Depending on the period of the rop, whether you are at the top or the bottom of the bounce curve you could let out or pull in the rope to reset the system. This might be able to be automated. The amount of energy this takes would then have to be compared to the pros and cons of a rigid system. Maybe in a rigid system this energy contributes to wobbles and polar shift of the whole system. Maybe those wobbles would have to be corrected in a rigid system. I believe this would take much experimentation as a lot of this depends on the performance of specific materials and shapes in the real world.
I like how this video is about the quality of youtube comments, but that's not making people think twice before posting their opinions on matter's they don't really understand very well at all.
I love how absolutely absurd the way that "works" looks. This is the type of thing that would show up in Star trek and have the entire crew spend 15 minutes going "WTF is going on with their ship?"
The precession problem is why I thought the design of the Hermes cycler in the Martian was epic, as the plane of rotation for the gravity hab modules is isolated to the bearing at the point where it intersects the main hull. This means you get that flat plane of rotation because the main hull is NOT rotating. It also gives you a stationary point to mount antenna, telescopes, thrusters and heavy stuff like fuel.
Wouldn't you need a large hull diameter (something in the tens of meters)?
@@tmst2199 the rotating section is a wheel with the much narrower main hull of the ship as the axis.
You would also need a counter rotating flywheel in order to prevent the main hull from spinning
@@ralphclark 2 wheels! Twice the fun!
How are you going to get the hull NOT to spin? They will simply counteract each other.
@@yourhandlehere1 Use thrusters to start the ring spinning as that will probably have the most angular momentum, then rotate the centre hull in the opposite direction
They could put a small one up on the ISS or Gateway to be used as sleeping quarters. It spins with the beds positioned to the sides, allowing you to sleep like you're on Earth, but also letting your body recover from zero gravity.
I don't think you would want to use this while sleeping, bed rest is a pretty good analog for zero-g on Earth so sleeping in AG wouldn't be very productive. I think the best implementation is for use during exercise similar to the MIT concepts around 15:16. This would take the form of an exercise bike or something similar that is on an arm within the ship. This would limit balance and motion sickness issues as you'd be on a bike seat and not turning your head too much. Intermittent exposure seems to be adequate to counteract zero-g, the 2nd paper on the right around 0:22 demonstrated that 30 minutes a day was enough to offset the muscle losses we usually see during bed rest studies. "Aerobic exercise capacity" was not maintained but this is probably because they were not moving while in AG, 30-60 minutes on a bike is pretty reasonable given current astronaut schedules and would likely do a better job maintaining "cardio."
@@ConHathy An external enclosed ladder attached to the ship's nose can provide a bit of gravity for the ship and great full-gravity (or more) exercise for the crew. Leave the ladder in orbit around Mars for the return trip.
The counterweight would need a dampening buffer or your balls would tend to sling around and chime when they collide, thus keeping you awake.
They don't deserve gravity if they didn't think of it first
@@Accumulator1 !!
Allright, so as a soon to be mechanical engineer I can say that the short centrifuge AT FIRST looks dizzying, with the head near the center of rotation, but really it's genius. The way it's built is *chef's kiss*. I even mistook the linear rails for an aluminum ladder, but linear rails are better. Linear rails are cheap as hell in these large quantities and you need only simple hardware like:
a)Wood
b)Bolt
c)Matress
Also it's so goddamn simple :D I feel like doing the structural analysis would be the best experience in the world since even hand calculations would end up near exact.
Bruh why they say it's a waste of funds lmaoooo
@@Mrpersonman0 Same with economists - a funeral is cheaper than heart surgery
The issue isn't with the construction. It's whether it's giving results relevant to the problem. People who think small radius artificial gravity was shown to be unworkable long ago are asking why we're still doing studies with a centrifuge so small it barely fits a full person.
You are not going to get a diploma, Bruh. LMAO
galvanized square steel, eco-friendly wood veneer, and screws borrowed from an aunt
something i don't understand about short radius centrifuges:
wouldn't they apply significantly less acceleration to your upper body, and especially your head?
and aren't those also the areas which are the most negatively affected by low gravity?
Same thing I was thinking, your feet could feel normal, but your head still feels weightless.
That depends on your facing isn't it
They have tried the small centrifuges for 50 years. There are inherent issues with them which only the long tether design can address.
@@Jinkypigs Eh?? Are you suggesting they fly to mars standing on their heads in artificial G?
Apparently, a difference of about 1% between the lower and upper extremities is detectable by humans and can result in nausea, vertigo, and other balance and inner ear related problems. While that is mostly just a comfort issue and would only really be a problem for long term habitation there are serious health risks with blood pooling in your lower extremities (because it weighs more in your feet than it does in your head) if the difference is too extreme. In order to be under 1% difference in a typical 6ft human, you'd be looking at a rotational body several kilometers in diameter. It's difficult but doable.
Alright I was ready to come in here and defend the tether design but you actually said it makes sense so now I don't know what to complain about. I hadn't considered the other designs, but I learned a lot from your analysis. These small radius centrifuges look very interesting and I'd love to see them developed more, but artificial gravity on the whole ship is some hard to beat quality of life. Anyway, subbed!
Note this is very noticeable in KSP for early RP-1 rockets, which almost always have at least one spin-stabilized stage.
If you start them spinning on the minimum axis, above a certain altitude, they will slowly spin out towards the maximum one due to the fact that KSP rockets are made of multiple parts that can bend and move in relation to each other.
It's also an important concern when making stock props. A 3-bladed prop is stable but a 2-bladed prop wants to yank the axle out of its housing whenever you turn the aircraft.
...I honestly don't think I've ever had to spin a single KSP ship...
@@TheWorldsprayer Me neither. Some people really overcomplicate that game.
@@TheWorldsprayer he’s referring to the realism mod overhaul.
@@aniquinstark4347 you do with certain mods
@TheWorldsprayer you never build a giant mass spinning completely unnecessary to brake either your ship, physic engine or hardware. Man you really missed out on a hell of a lot of fun.
Oh my god I love you. I do the moment of inertia with a phone demo for people ALL THE TIME
Haha I was thinking about the T Axis handle all the time, great that you mentioned it!
I love the way you went about this discussion. Don't give up on snapping the tether as NASA has proven fairly good at projecting trajectories and wasting all that momentum would be a shame.
Exactly, it's like a stone in a sling. If you time the release just right, it will go where you want.
It depends on your design. If the counterweight is a big propellant tank (like a Starship tanker version or something) then throwing it away will get you less delta-V than despinning and using the propellant in your engine.
Also, NASA has real world experiences with their tethered weight experiment for power generation using the Earth's magnetic field. The cable was several kilometers in length, and actually jammed, forcing them to cut it loose from the shuttle.
@@paulmoffat9306 I missed hearing of that, so tragic since some people have been waiting most of their lives to see that experiment done.
Recently I watched a youtube video were it showed some astronauts in space doing an experiment where they spun a crew member in a chair. It was to compare the results to that of spinning a person in a small centrifuge on Earth. The result was none of the crew got sick when spinning inside the spacecraft where there is no gravity, but they did when on the Earth? The conclusion was that gravity affected the inner ear and that was what made people sick when spinning. I am not sure how this relates to artificial gravity in space, but maybe the human body can tolerate a faster spin rate in space than what is presently accepted. I don't know the answer, just food for thought.
Yeah, since there is no other major gravitational competition off Earth the confusion or mixed signals might be significantly less.
While being on Earth your stability system is still affected by it's gravity. So your perception is of you rotating in some general position to ground.
Going around ain't no gravity, that's centrifugal force
Makes sense. In 0 G, the way your body rotates is directly influenced by any motion of your body. The natural direction change of all the body parts is less disorienting for the inner ear as there are less forces working on it.
@@santos-kn5dt Einsteins equivalence principle says that gravity and centrifugal force are equivalent.
The phone flipping analogy was the coolest interactive thing I've seen to demonstrate a concept, well done.
By far the coolest thing on this video was the little T handle spinning and flipping every so many rotations. ua-cam.com/video/aONcg5pcspI/v-deo.html
I wonder how many people broke their phones though
We had a mechanical merry go round in my local park. Only one ive seen physically. It was a wonder. I digress, it was covered with a metal dome where we could climb into once pushing it to its limits. Orienting yourself to he correct position had this same effect. You could spin full speed for 15 minutes looking any direction with no ill effects. Compared to to the 5 on the actual seats at 3/4 speed. I was instantly reminded of those memories upon seeing your video. Thanks for bringing up golden times.
I would think short-radius centrifuges have major disadvantages vs the tethered starships option:
1.) Uneven: Different spin and therefore uneven G-force applied from top-down on the body.
2.) Stationary: Movement around the cabin and useful work is limited to near zero: inactive astronauts.
3.) Periodical: This is a guess, but I can hardly imagine that anyone could so much get used to the rotation that sleep could be accomplished: only periodical use vs continuous.
Sleeping in a centrifuge wouldn’t be worth it, we use bed rest to simulate the side effects of zero-g already so there would be no benefit. The best use would be for exercise like the MIT designed bike I show near the end. This is time where the crew is already staying in one spot and is committed to zero-g countermeasures. Exercise in a centrifuge would just make the existing countermeasures more effective. It is unevenly distributed, but if it’s good enough to reduce pressure in your eyes and puts strain on your skeleton and heart, then it’s an improvement to what we have for a fraction of the cost and complexity of tethering.
Either way the first missions will probably just use normal exercise like we do on the ISS.
The three-starship solution seems to have the same problem like the rotating wingnut in zero gravity, that in regular intervals flips around 180 degrees.
That's addressed in the video
Very well done! You deserve so many more views!
Finally! I found a video talking about the same thing I've been thinking about for years now.
Yes, bone and muscle loss are the biggest physiological problems for a trip to Mars.
I envisioned two cuboid shipping containers tethered together by cables (and transit ducts) about 200 feet apart, slowly rotating around their center of mass.
A trip can be shortened to about 40+ days with a variable impulse ion or plasma engine, such as Ad Astra's Vasimr engine.
The biggest problem may actually be radiation. Bone and muscle loss can be kept in check with training. The longest stay so far was 437 days, so the astronauts would probably survive a Mars mission even without artificial gravity or spending time on Mars with a 3rd of Earth gravity. The question is how long it will take them to recuperate....
Short radius is a good solution for astronauts, whom have been rigorously trained. And for a situation where all you need the gravity for is maintaining human health.
It most likely is not a solution for anything else. Civilians wouldn't be able to handle the restrictions for the periods of time involved.
"a situation where all you need the gravity for is maintaining human health"
Yep... But that's not the only thing a bit of gravity is very useful for. Tons of activities are much easier with some constant acceleration "down".
Micro gravity is the point of a lot of space research and (hopefully) manufacturing, but we really want to have areas with micro gravity *and* areas with some appreciable gravity with easy access to each other.
Oh, on the health thing... Have we figured out how much gravity is required to maintain long-ish human health?
@@travcollier Correct. Even fractional gravity is a good thing and its not that hard to achieve with spin. Its good that liquids don't float around. Its good that you can eat (relatively) normally. Its good that you don't have to strap yourself into the bunk. But one thing a lot of people haven't really given much thought to is the possibility of a real shower on a long space flight. Rather than using wipes (which itself becomes a garbage/recycling problem). A real shower would make a huge difference to morale.
Another point is that you can compensate for having less than a full Earth gravity environment by adding wearable mass - which puts more load on your bones/muscles. And as it happens, wearable radiation protection (vests etc) is a good idea and will also add to your effective weight. That lands you in a zone around 0.8 Earth gravity.
Just crunching the math. A transit vehicle (Earth to Mars and return) comprised of a 150 metre truss with tankage on the far end acting as a counterweight to the habitat on the near end. Effective radius about 80 metres. For this we have 2 revolutions per minute provides near Mars gravity. 3 rpm provides 0.8 Earth gravity. And that is acceptable provided it is spun up gradually.
I had suspected that astronauts could adapt to short-radius centrifuges based on watching a ride operator walk around inside an amusement park centrifuge (with a radial acceleration of about 1g) circa 1970. I'm really happy to see this confirmed by the recent research you mention here. Thanks for a really excellent video.
By the way, here's an idea I had a while back that I've never seen mentioned elsewhere, though I seriously doubt I'm the first person to think of it, and I would love to see someone do a video about it. Land the lunar starship upside down. The lunar engines are already going to be mounted high up the side anyway. Landing nose-down would put the astronauts and cargo near the surface and give a clear view of the terrain from the flight deck. It might even be more stable, depending how how full the tanks are at landing.
I think you are the first person in history to think of landing a space ship upside down.
I think this is a really clever concept.
@@TheBooban I'm sure Elon Musk would have thought of it. That bugger seems to think of just about everything, and of ways to make them work. A latter day Edison, to be sure.
@@TheBooban isn't that normally called a Crash? 😊
Yeah. Who would have imagined that astronauts who spend over a year in microgravity without spontaneously combusting could possibly adapt to life in a centrifuge for a few months? 🙄
The tether concept was experimented with and was found out that due cable stretching and pulling back like a spring the space craft is pulled towards the center then a inertia pulls the craft away from the counter weight creating an impact load on cable and makes the center of rotation unstable meaning gravity will be as well. This is a reason why solid structures are required in between the ships. As for small diameter centrifuges, they will work for research purposes and small scale transport but the selling point is colonization.
you may like Steve Mould's video on parametric resonance and different modes of elasticity
The first thing that people ask is "what happens when the tether breaks?" because that's exactly what happened during the mission TSS-1R; you also didn't considered the damage that the whiplashing cable would do
Was that the one that dragged a cable through the magnetic field of the Earth to generate electricity but wound up generating too much which blew the cable? Not the same thing at all.
@@dpsamu2000 the application was different but the concept was the same: two objects in space tethered by a cable under tension. When the cable broke, the object without propulsion was lost to space. That's why "what happens when the tether breaks" is a perfectly valid question
@@Beregorn88 The conductor wasn't a structural support cable. It was thin, and in an experiment of unknown electric forces. The tension on an AG is known, and mentioned in the video. The solution to the question of what happens was answered by making the cable strong enough not to break, redundant if one broke, and having enough fuel to recover from the separation. There are only so many things that can be done practically. Too much pearl clutching on one thing winds up neglecting other things. Every major disaster in NASA was caused by that. Apollo 1 fire pressurized oxygen was the cause, and failure of an impossible standard of no ignition source caused the negligence of the hazard. Neglecting the cause of Gus Grisom's blown Mercury capsule hatch resulted in the Apollo 1 hatch that couldn't blow. If it could have blown the pressure would have dropped, fire wouldn't have spread explosively, could have been put out, and the astronauts could have been extracted. Same with the Challenger O rings where dire warnings were repressed, and NASA tried to fraudulently technobabble out of their responsibility to the investigating committee. Richard Feynman on the committee exposed their fraud with a glass of ice water, and a clamp. Columbia was lost because tile damage was neglected as was scheduling a backup rescue vehicle. That backup was done on subsequent missions as was tile inspection and repair equipment. All of which I suggested in a paper I wrote 2 days after the disaster. Also criticizing NASA for failing to advance the next shuttle in line just 30 days from its scheduled launch for a rescue. I pointed out the foam strike was large enough to do significant damage. In that same paper I predicted the damage to within a few tenths of an inch the length, depth, and width of the gouge the foam would make on the tiles. Spending over a million dollars on a test simulation of the strike produced a gouge within that few tenths of an inch on the first try. NASA claiming it was a fluke that the damage was predictable, and to evade responsibility for failing to launch a rescue, and to evade having a standby for subsequent launches spent another 20 million testing with a different angle strikes to prove me wrong. Those tests only succeeded in blowing holes in the wing. I can no longer find the video of the first test that resulted in the gouge I predicted. The point is rationalization is not reason. Your comparison to the breaking of the conducting tether of the TSS-1R experiment was an intellectually incompetent rationalization.
I think for a Mars mission you would aim for 1/3 gravity. They are going to be on Mars and under that gravity for some time. And the simple two starship 500m tether gets my vote. You want the whole living space at 1/3 g.
1. I think you'd want to keep it higher than that. Maybe not as high as 1g, but still higher than Mars.
2. You don't need to keep it constant. You may start higher and lower the rate and the gravity as you go and then do the opposite on the way back.
You want 1g, cause one of the biggest issues astronauts face is loss of bone density. This would also be the longest time a human has been out in space. It's crucial they experience the most amount of artificial gravity as possible in order to stay healthy enough for the trip back and carry out their job on mars.
@@jonathananderson7990 They will be on Mars for 2 years at least.... 730 day, Way past any record on the ISS. They go knowing that it will permanently affect their bodies. In fact they may not be able to return at all for that exact reason.
@@moozoowizard Well what would be the point in giving them anything less than the most time possible under normal gravity? Is there a purpose you want them to get used to mars gravity?
@@jonathananderson7990 they are going to make a colony. At least with Elon they are. A colony where everyone comes back every two years isn't going to work. 6-9 months of 1g on the way won't make much of a difference if they are going for 10 years + say. And they won't be taking a centrifuge for gravity on Mars. Anyway that's my view if it. Sure on the way back. Start at .3 g and slow increase to 1g so they are use to it when they land on earth
excellently presented! Thanks for sharing! I'm all for going to Mars when we can travel 20 times faster than we now can. The "problem" is going to be with mental health and such. Best of luck to all of us!
we actually already have the technology, we already have small nuclear reactors inside military submarines, and we already have ion thrusters that's pretty much in every satellite we launch, and we already have giant radiators in the international space station.
you only need to combine these 3 things to make nuclear spaceship viable. nuclear spaceship is basically just your average satellite, but instead of being powered by battery or solar panel, it's powered by a small nuclear power plant, and the most conservative estimates say that we should be able to cut travel time to only one month.
Mental health will be okay. We have submarines out at sea for months, scientists who over-winter at the south pole, etc. Obviously you need to screen the people, and give them some structure, but it's completely do-able.
The classic case was the BioSphere 2, which had 8 people locked up inside for 2 years. There was major conflict, but they also had to deal with constant stress over oxygen levels and insufficient food. And nobody got hurt.
In the case of a space station, beyond the ISS, I think a thin cylinder shape, probably a quarter of the diameter thick, would make sense to have enough space for people to live in with plenty more in addition. Instead of thrusters, I'm thinking an equivalent to reaction wheels for the spin and moveable weights along the edge to maintain a consistent center of gravity with a docking bay in the center which would decrease in RPM to match the incoming ship to allow for a proper connection. After the ship departs, the center will start to spin after those who entered are along the outside until it's matched the RPM of the station when they're able to exit the dock and go elsewhere. There's more to the idea, but this should be enough for now.
you probably don't need a rotating berth, just sync your incoming spacecraft's rotational rate. we've all seen interstellar by now, yes?
Spinning the entire ship will make your control engineer hate you as your actuators change orientation all the time.
I do actually like the two ship rope idea. Make the rope a winch and you have a great control tool. Hock in close bring the system to target rpm. Then let the winch increase distance while the thrusters keep the rpm to increase gravity. Would love to experience this.
Having a centrifuge inside the ship is somerhing your controlengineer would love. As it stabelizes the system. Actually having two like a dumbbell would be great to control stability. While you travel speed it up to keep orientation, even if you hit something. If you want to manover regenerative brake the centrifuges, manover with little moment of inertia and spin them up again. It might be possible to rotate more efficient with coordinated acceleration of the centrifuge and thrusting.
Sience fiction got his point right quite a view times. Many long travel ships have a ring rotating, the main thruster in the center of rotation and the thrusters located on a long leaver fixed on the none rotating frame. Thats basically a centrifuge but outside of the main rockets shell.
Well done. The medium moment of inertia of rotating bodies is a very difficult concept to understand.
this guy gotta get more recognition
Great show! Not previously aware of the opportunities with small radius centrifuges. Like the instability demonstrations, saw the spaces Tatiana handle previously but you provided an excellent explanation, thanks!
Lets take a moment to appreciate the quick remote camera work at arecibo tht gave us some once in a lifetime footage!
OK this was a great video. It anticipated most of my objections. Heinlein already described most of the single starship issues, for viewers of a certain age who've read his work; he refers to the viable single starship solution as a "tumbling pigeon". And yes, thanks to Veritasium, I knew about the intermediate axis problem so when you brought up smallstars's idea, the issue was already clear. Good citation, btw. I think you over-emphasized refuting that one commenter's plan, though. Your modification is pretty much one of the two standard versions of spin tethers I've seen, and it's not that different from smallstars's idea, so long as you reorient or reconfigure the hub ship prior to spin-up so it rotates around the correct axis. The other version I've seen is where there is no central ship, which comes with its own tradeoffs.
Since Elon Musk's plan is to send a fleet of Starships, you also might want to look at the engineering issues of having multiple ships hanging together in grape clusters (eg a hub ship with, say, three ships/inflatables connected and hanging on each of the two tethers) vs flying in separate pairs/triplets. His vision is to get beyond "boots on the ground" PR stunts and pure research Big Science missions. That requires drastically larger crews and payloads per mission, and also many more missions.
One consequence from a mission planning perspective is that with very long tethers (R=85m+), your crew can spend the outbound trip acclimating to martian gravity and land on the surface ready to work on day one (with minimal adaptation required to learn/unlearn 2 RPM coriolis effects at each end of the journey). Of course, that's also assuming no long-duration adverse health effects for living/working in martian gravity, which we don't know. As g-requirements go up, the practicality of spin tethers goes down.
Small radius centrifuges have many problems; I get that you don't want to talk about them so I won't. They do have a place in a mars mission, even one using spin tethers. If you're sending a dozen starships, it starts making sense to leave an occasionally-manned space station in Martian orbit (or docked to one of its moons, which isn't all that different). I could totally see the utility of having a small axis centrifuge aboard such a station, especially given the intermittent crew.
Most of our assumptions about mission planning stem from the idea that it's a research/PR mission funded and run by NASA. Even two years ago, Musk's ideas about cost and scale seemed optimistic to the point of lunacy. While it's still very optimistic, nobody's laughing now. I don't think anybody has fully grokked the implications of a big shift in launch costs. A shift in cost economics, and sending a fleet of ships on a working mission, changes what you expect of the crew and how you make tradeoffs between payload and cost, and that in turn affects what your ship and habitat look like.
Very interesting. Would spinning up a "small"ish centrifuge inside of Starship affect the ships movement?
Just wanted to share some thoughts on your video. Awesome content! Thank you for making it. The idea of the tether is genius. It would be practical and easy to add. Each Starship could have the tether cable, winch system and its own tethering hook in the nose cone. You could have two Starships meet nose to nose in order to initiate the tether, with each ship hooking to the other one's tether. This would give you redundancy, with two tether cables, one from each ship, keeping the system connected. You can then initiate the spin with a really short radius, the length of two Starships essentially, and pay out the tether cable as you accelerate to use that centrifugal inertia to help with the acceleration process. Then disengaging those tethers at the same time when it's time for the Starship pair to separate, after they are done with their journey.
Great video! Love how in depth it is for just a 16 minute video
My criticism of short radius centrifuges is that they solve a subset of problems and also tend to be more effective in loading the lower body.
Spin gravity applied to the whole vehicle has other worthwhile benefits. One of those is simply to create a sense of "up" and "down" within the crew cabin which has psychological benefits. There is also the practical benefit of ensuring objects will fall. That makes a lot of activities, like eating, a lot less complicated. (Ok, so you still need zero g procedures for when you're not spinning). Again, the intangible here is psychological benefit. Speaking of which, I don't think it too much of a luxury to have a normal shower and spin gravity is essential to this (you need the water to head down and be collected, not float).
So while I get the idea of centrifuges in some contexts, I still feel that spin gravity, if its practical to implement, should be implemented.
And while I'm here, I'll point out that a lot of people seem to be fixated on creating exactly one Earth g. Much of the benefits noted above work at fractions of an Earth g. Also, wearable masses (imagine for instance a radiation protection vest) would increase musculoskeletal loading and would be applicable in the range of 0.5 to 0.8 Earth gs. So you may be able to seek a reasonable compromise at below 0.8 g. Again, something to factor in when you're doing the real engineering trades.
Tethers are lighter than a rigid trusswork, but are there secondary stability issues with a flexible tether? Such as wobbling or twisting of the load, "crack the whip" scenarios, etc.? Is some sort of shock absorbing and dampening system necessary?
When enough tension is applied to a flexible cord it begins to act rigid. The velocity of spin required to create meaningful artificial gravity easily accounts for that
Always liked this choice of a cable. With 2 starships you can rescue each other if necessary that far safer
With starship being so cheap, you'd have a robotic cargo/replacement spaceship close by anyway.
I suppose the one nice thing about the tethered method is since that would cause the gravity to be in the same direction as when the starship lands, allowing you to design the interior to be used the same way on land and in space, a minor benefit but a cool one
Small spinnes are health risk for the crew in long term missions. Better will be to use the whole ship version, but go for lower G than 1. Spincalc mostly covers all situations. By the way, the best "spinner ship" would be either equivalent of tyqoon "station" from ixion pc game, or Nauvoo from expanse sci-fi universe.
Yeah, all I can think of with the a small spinner is the drastic difference in g-force between the head and feet and how that'd affect stuff like circulation.
I imagine if we don't have the data already before launching a mission to mars, it make the most sense to see how well the crew manages in simulated martian gravity. For the long voyage.
If there's negative health effects then we know colonizing mars is going to have more issues then we thought.
I still think constant acceleration with plasma/ion engines (Like VASIMR) is the best option for artificial gravity. The gravity is toward the base of the starship and you just need to rotate 180 degrees during the deceleration half of the flight. Just build the damned radiant heat exchangers so you can run a nuclear generator about the size we already have on nuclear submarines and you have sufficient power for VASIMR engines. You may still not get enough acceleration for a full 1G but that probably is not necessary to maintain health anyway, especially since with constant acceleration the trip to Mars is shortened to like 40 days. If you can generate 1/3 G everyone is already acclimated by the time you get to Mars.
Constant thrust would be great, but you certainly couldn’t get 40 days of 1/3 G with any like current technology. I don’t see a thrust to weight ratio for VASIMR but the thrust is only 5 N so if the engine, reaction mass, and power source have a mass of more than 1.5kg (they definitely do) it isn’t capable of that level of acceleration even at this small scale.
Constant thrust would help in many ways. Like, even constant 0.1G would limit travel time to Mars to under 1 week (in the launch window around the shortest distance) - this translates to much less radiation, wider practical launch window, no need for aerobraking.
With a realistic power source, you're talking about less than 0.01 gs. In other words, enough gravity to make things settle and leave a sense of "up" and "down". Perhaps enough to have a real shower (if you were patient). But not enough to get the physiological effects of gravity.
Epstein Drive from the Expanse was that bit of magic. Maybe someday in some universe.
@@jaceksiuda -- "even constant 0.1G" -- that's not as big a concession as you think.
Accelerating 'A' metres per second squared halfway through a distance 'x', then decelerating at the same rate the other half of the distance, the minimum possible time-averaged rate of kinetic energy accumulation per unit mass is one-half of the square root of (A cubed x). For A=0.98 m/s^2 and 'x'=64 billion metres that comes out 123 kW/kg.
That's with a perfectly efficient engine that gets perfect traction on space itself. A heat engine, throwing propellant (which carries off kinetic energy of its own) you're looking at a need to radiate away about 1 MW/kg.
Yay, finally somebody has reminded us all of what I learned 50 years ago in year 12 physics about rotational motion.
The ellipsoid rolls on Poinsot's plane
"What if the teather breaks?" As if we can't build huge suspension bridges.
I'm a big fan of the two-Starships-connected-by-cables concept for a Mars mission. One passenger and one cargo (with the cargo Starship also acting as a lifeboat).
Two things. One, there is no need to create an artificial gravity greater than Mars' gravity (.375 g). There will already be a gravity gradient between decks that can be put to some use.
Second, I have a concern if the cable breaks it will snap back on the Starship and damage it or wrap around it. It will be under 80 tons of tension, and I have no idea how it will react when suddenly going to zero.
I grew up just south of KSC, with several family members working there , one worked in the graphic design dept of the print shop . She would bring home non classified projects that were to be presented to NASA and DOD or congressional big wigs . One of these was a well engineered copy of Zubrin's direct to mars, others were more complicated variations . Zubrin's plan was shot down because it did not bring jobs and money to their districts . DOD and NASA engineers the simplicity .low risk, low cost and short lead time . Congressmen did not care what this could do for the country just how much public credit and private kickback they could claim.
part two The first presentation was over a hundred pages of what had to be designed and what they had on the shelf , with pages of draft blue prints for a 23? ton package of booster, landing system , and hab can launch-able on the shuttle . They also had plans for two expendable launchers with orbital docking of booster and landing system/ hab can but this would have much larger and cheaper than shuttle plan. I vaguely remember they all used Zubrin's rotational system at .4G , They had already tested synthetic cable that could hold the entire stress of lander but they used 6 for safety. This all came about maybe 6-9 months after Zubrin's book .
@@virginiamiller3521 His plan has a lot of moving parts consisting of many elements that have yet to be designed, built, and tested.
My plan for Mars is two Starships (one cargo, one passenger), refueled in Earth orbit, connected nose-to-nose with a tether after TMI and course corrections, and spun up to Mars gravity with side-firing hot gas thrusters.
Simple, cheap, uses existing technology, and probably the safest approach in that the cargo Starship could be used as a lifeboat.
Not as sexy as the cycler system in "Stowaway" or some of futuristic nuclear electric proton warp drive proposals, but it is doable today.
Use a combination of short radius centrifuges at the axis for workouts at higher gravity with lower gravity (lunar level) at larger radius with slower spin rate.
The human body needs a gravity of 1g constantly or the human will experience changes. Not more and not less.
NASA made an experiment with short radius centrifuges that were running at 1.2g. It ended in disaster (one participant had a short cardiac arrest). The human body isn't made for anything except 1g.
Also, regarding the ring-stations - yeah, they're not very practical to build, but my favorite proposal for building a space station was one that involved the big orange fuel tanks used in the shuttle program - the idea was that rather than discarding them, they'd give them just enough extra push to get into orbit, where after numerous launches, we could send up a space-tug with some extra hardware to rendezvous and gather them all together and use them to build the segments of a ring station (of course you'd start with the dumbbell of 2, but then you can keep attaching them in pairs until you have the full ring).
one concept not covered by this video, that I think would actually be quite nice, is to have two starships dock nose-to-nose, no tether required.
Yes, it'll be a short radius, and having the crew cabins near the center of rotation compared to the fuel "wastes" the strongest centrifugal force, but it's easily the least complex and most practical approach.
keep in mind, they don't need a full gee, just enough of a gradient to stave off the worst effects
Feels like they're shoehorning this into a craft that didn't have this in mind from conception.
Yes, it makes a big difference if the lift-points and the upper structure is designed to hold the weight of an empty or a fully fueled and loaded Starship.
At the moment it is an empty steel-silo with blank slates welded together, nobody is dreaming about hanging additional hundreds of tons to the frame
Lower bound on dry mass is 100t and Wikipedia payload mass is 100t, so the lift points can handle at least 200 tonnes-force, conservatively. Even if for some reason you're traveling with 1200 tonnes of prop, pushing total mass to 1400 tonnes, the lift points can still provide 200 tonnes-force of centripetal force, or 0.14Gs. My guess is that would be worth it. More likely tho travel mass would probably be low enough to provide at least as much gravity as Mars does
The two vehicles connected by a tether has been my favorite for many years. I am no expert, but my intuition tells me that that is the easiest, cheapest, and most stable large radius set up. I hope that someone sets this rig up in orbit around earth for experimental purposes.
Would it be possible to deliver and retrieve people and cargo to that rotating system without stopping it? Some sort of creeper car stationed on the axis point that creeps down the tether to the vehicles?
I don’t see any physical reason why you couldn’t, you would want a rotating docking mount so it didn’t move but otherwise this seems like something we could pull off if we wanted to
@@ConHathy ha! You are right there right now! I did not expect your immediate presence! That was almost startling. :-)
The "creeper car" is more usually known as an _elevator_ . It takes people and cargo down from the axis point, gravity gradually increasing, and -- unless they want to exit via a trapdoor in an unpressurized deck down there -- back up.
Trapdoor diving takes rotational kinetic energy away from the station. If the loss is made up by ion thrusters, it is a way to get an impulse from those thrusters in a short time that they took much longer to make.
@@ConHathy What AG, if any, has already been tried aboard the ISS? I do appreciate that the whole station is a microgravity environment for the benefits of science, but has anybody considered the use of something like an attached module, for AG research?
@@phildavenport4150 if I remember correctly I think they discussed it in the very early days of the design but we’re concerned about how the vibrations could affect the rest of the station. The only a.g. done in space was gemini and it was very slow tethered rotation. The purpose of the test was more for “station keeping” between two vehicles than actually creating meaningful acceleration.
This just drifted through my feed, I think I just found a channel to sub to.
I also really like the use of the astronaut avatar as a way to deal with the microphone. Some serious "calling it a feature" there.
"...this lunar landing contract came with 2.89 billion dollars, which is definitely going to speed up development..."
Wow. _That_ aged like milk.
Other than that, great video!
Have a nice day!
Ok, so to jump in on the questions about the small centrifuge. Is this something that can only be used for sleep? What would you suggest for an implementation of a small centrifuge on Starship? Can people on this solution do useful work, or are they just going to be lying down while their body fluids drain back to places where they should be? I have generally been on the anti-small camp, but I'm really curious as to what a recommended implementation might look like, and how it might help Starship travelers. Also, most importantly, can you poop within the small centrifuge?
I don't think you would want to use this while sleeping, bed rest is a pretty good analog for zero-g on Earth so sleeping in AG wouldn't be very productive. I think the best implementation is for use during exercise similar to the MIT concepts around 15:16. This would take the form of an exercise bike or something similar that is on an arm within the starship's 9m diameter. This would further limit balance and motion sickness issues as you'd be on a bike seat and not moving your head side to side. Intermittent exposure seems to be adequate to counteract zero-g, the 2nd paper on the right around 0:22 demonstrated that 30 minutes a day was enough to offset the muscle losses we usually see during bed rest studies. "Aerobic exercise capacity" was not maintained but this is probably because they were not moving while in AG, 30-60 minutes on a bike is pretty reasonable given current astronaut schedules and would likely do a better job maintaining "cardio."
I wouldn't put a toilet on one but I don't see why it wouldn't work.
@@ConHathy I mean have you seen how they use the loo in space? I'll take gravity for my toilet runs, please!
I very much appreciate you not brushing off what if the tether snaps. Human history is literally the story of shit failing over and over again until we find something acceptable. It would extreme arrogance to act like the tether would never fail ever, and there should absolutely be plans addressed in case it does.
You don't need any fuel to start spinning, there are several ways to avoid carrying extra fuel. A couple of them:
1 - Send first ship and then a second ship just a bit faster than needed. Bind the link at the very moment when the 2nd ship overtakes the first, and they will start spinning naturally with no extra energy cost. Just cut the link on Mars orbit insertion, both ships will go in slighty different orbits but that is probably desirable
2 - Link both ships without any rotation at first, tied to a small central ring, with 1/2 of the total payload located ina capsule inside the ring. Then use solar energy to rotate the central ring against the inner payload capsule and the ships will start rotating in the opposite direction naturally. Invert the process on arrival.
1 - ignoring the fact you’re trying to connect the ships while they’re moving a hundreds of meters per second relative to each other, that velocity still came from propellant
2 - that’s going to have to be a huge flywheel spinning very fast. It would probably double the mass of the whole spacecraft, at that point why not just use the fuel which would be lighter. Another way to think of this is that the propellant is expelled at thousands of m/s, so the flywheel must also spinning at thousands of m/s or be much larger than the rest of the spacecraft to match the performance per kg (ignoring all the mass of the motor+solar)
@@ConHathy 1 - You dotn need extra fuel (or very little) extra fuel, by conservation of momentum the center of mass will move at the same average speed before and after connecting the ships.
2 - In my proposal the central mass would be made of useful payload that they need to bring anyway, it would not be made of extra mass. Same about the solar panels. Some extra mass is neccesary for binding the containers and ring, but almost irrelevant compared with the total mass. In fact it can save fuel by acting as a kinetic battery and reducing the need of some of the fuel for orbit insertion.
To land 100 tons on the moon, no one actually knows how many star-ship launches are needed for every 100 tons, but it is definitely more than 3, and most likely over 20, if not over 60.
You need a lot more than 100 tons for a small base and its supply-over-time.
Not sure if you have mentioned this in any of your more recent videos, but I suspect that the eye pressure problem on the short radius centrifuges is most likely due to the gradient offset of the G-forces. The subject's head is close to the centre point of the rotational axis meaning that the head is closer to the zero G point. If the short radius centrifuge is just a bit longer such that the subject's head is closer to 0.5 G it might help with the eye pressure problem. But, I'm no physicist, so I might be wrong on this, it's just what made logical sense to me. 😅
psst! that's the whole point of the experiment, and I guarantee they didn't do _all_ their trials centered.
you start off with one end of your gradient as "no movement" then adjust the radius and speed in little increments from there to see what different ratios are like.
Hey, thank you for the insight on rotational stability problem. I really liked it.
As layperson I have a question regarding the segment around 12:20: if the all 500m apparatus was rotating at 2 rpm, shouldn't the starships rotate faster than that after the tether is cut because of conservation of angular momentum?
That's what I thought but no. If you cut the tether you go from a force pulling the ships together to no force at all. There is no force to cause angular acceleration of the ships. The angular momentum stays the same because the starships continue to move in two parallel straight lines which when looked at from the correct frame of reference, gives you angular momentum.
Hopefully we can get a follow up #short better explaining it
No, they would still rotate at 2 RPM. Angular momentum at a very general level is actually masses traveling parallel in opposite directions. The relationship where it's the moment of inertia times the angular velocity is actually derived from this and is really just a simplified version of totaling up the angular momentum of a bunch of tiny point masses (atoms) moving in opposite directions.
The two Starships are themselves, traveling in opposite directions and are separated by 1 km. When the tether breaks they are still moving in opposite directions and their paths are still separated. This is where the bulk of the angular momentum of the system is because the Starships are small relative to how far apart they are. Breaking the tether does not require this momentum to be transferred to the rotation of the Starships. As they float off into space, their separation increases, and their relative angular velocity decreases such that angular momentum is conserved.
By the way, this is why two non-spinning objects can collide and end up spinning in the same direction, it's turning the angular momentum of non-aligned velocities into the more familiar form of rotating objects. But again, if we zoom in on the rotating objects are just a bunch of atoms traveling along opposite parallel (actually concentric) paths.
Thanks for the comment, I didn't even think to mention this in the video. Also, don't worry, my brother has been an engineer longer than me and he asked a pretty similar question.
@@ConHathy & @seedorfj
Thank you!
I understand. Actually it's pretty obvious now duh!
@@ConHathy ... So you are a fan of small centrifuges inside the ship? Then what is the point of preserving the human body if you a apply a gradient of gravity from the legs to the head, if the head only experiences a fraction of the gravity. Are you willing to preserve the crew's feet only? Have you ever thought about how important the bones sustaining the head on your shoulders really are? Imagine you land on mars and your head is suddenly falling cause you are not able to sustain it anymore... that's why i support the idea of larger centrifuges. Cheers! And keep the science up, overall i liked the video!
@@evoelias6035 true, you would probably want at least 1/3 g at their head level so their neck is accustomed to at least Mars level gravity. That said, astronauts have spent up to a year in space with no AG and didn’t break their necks. I would be more concerned with heart and eye health or the recently discovered blood clots that form in zero g.
Great explainer about the concept of moments in general. This would have been real helpful for applied mechanics class.
Incredible video! So well done.
I'm saying for years that short arm centrifuges are the way to go for science missions. They allow the ship to keep its orientation (solar cells, antenna, thermal management all depend on that!), are relatively easy to install in a ship like Starship and are super usuful for supplementing daily workout to keep the astronauts in shape.
i cant do the actual math myself, but using spincalc, 500 meter radius to get 1g is about 1.3 rpm. also i'd imagine they dont even NEED 1g. i wonder how low they could get away with and still stave off the effects of 0g life.
Since Mars is 0.34g that is the most that is needed.
Nice video!
While I agree that short-radius centrifuges may be more practical to build, I don't see them more practical to use. Living in gravity is far more than organic health and our bodies function better in ergonomic terms when something is pulling us "down". From eating (with your digestive system benefiting from gravity as a bonus) to writing, walking, playing basketball (with very large radii, this would be possible without significantly twisted throws), using untethered tools, drinking water... the list goes on.
Adding to it, I definitely hope no one builds a ring station, though... if they do, we can throw the old trope at them: "Well done, FLIPPER!" :D
However you are right living in gravity is better. We are still talking about first steps towards interplanetary travel. And it must be as compact as possible. We simply can't afford to haul hundreds or thousands of tons of material from Earth into orbit to build most luxurious spaceship we can think of. It must be minimalist and functioning. And SRC beds are answer for this. Sure once we establish our presence on places like moon from where we will be able to haul material into space for cost of putting it on marine container ship then yes, we can build huge spinning vessels to provide home like conditions for crew.
@@jamessatler5461 Hi! Thanks for answering! Well, I partially agree with you and the part that I don't refers to the fact that we are aiming at making a manned flight to (or even a colony on) Mars before being extra capable in mining regolith from the Moon and building with it directly in space. I would never try to jump steps in this case, as I believe the time when human lives were as expendable as to be OK to place them in caravels and send them to their almost certain death is long gone (is it?...). When you have space mining and space building capabilities (it doesn't even have to be a full economy, but only the capabilities to use in a project, which is far faster to achieve), then we can truly build Mars-capable spaceships with proper artificial gravity (among other necessary capabilities - such as hydroponic bays, large CO2 scrubbers, proper space for people to walk, etc. - that don't fit all too well in a "caravel" like Starship).
Studies show 15 minutes a day in gravity reduces 85% of the bone loss of no gravity, and 75% of the bone loss of no gravity with 2 hours a day hard exercise. A short rotation centrifuge for eating, toilet, bath, and sleep would solve nearly all no gravity problems without hours of exercise, and the long hours of sleep has low head turning effect. That effect in ground centrifuge studies is partly due to both the centrifugal force, and the gravitational force on a different axis. The fluid in the ears tilts in opposite directions. Not a big problem unless you turn the head resulting in the fluid swirling like when you slosh a cup of water so the water takes on a wave form against the sides of the cup. In the ear that's where the balance nerves are. As long as the fluid doesn't slosh you're ok. The surface of the fluid stimulated just the nerves at the surfaces of the fluid. But the slosh stimulates all the nerves in there making us dizzy. Like when you spin as a kid. You don't get dizzy until you stop. The fluid is still spinning with that angle which makes it slosh. In space centrifuge there isn't 2 directions of force so the fluid is stable, and if you slowly stop or turn your head you don't get that slosh as much.
In that spinning table the head itself is right at the pivot point - meaning the head is not experiencing gravity. This surely would have an impact on the results of the experiment.
That was actually a control configuration where there is intentionally no load on the eyes, they can also elongate the arm to subject they eyes to AG
Thought this was an sfs video💀
Same
Same here
Same
same
It's weird seeing you guys here, glad the community is still somewhat alive. Sfs might not be the most detailed game or the most fun game to replay, but it sure is amazing and impressive how a small independent creator made an entire solar system in his PC (And He Didn't Even Put Ads!). Stef and SFS deserve way more recognition.
But again it's glad seeing you all here together again.
Man you put a ton of effort into this 👏
For Crew Starship applications, two ships tethered at the nose seems by far the best cheapest option. Lot’s of bang. SpaceX will build lots of cargo/tanker Starships and their propellant can be adjusted to balance the crewed ship. Tether allows variable G - which means for example a mission could test long term living at exactly Mars gravity in a Ship built to be a Mars hab. A tether to a cargo Starship seems way better/cheaper/more useful than a short radius spin machine.
Don't confuse 'easy to say' with 'easy to do.' The statement "tethered at the nose" hides a ton of complexity:
- Are you going to try to do the Mars transfer burn while connected? What kind of connection can carry that much load, would the entire ship need to be reinforced? Or are you going to try to do simultaneous transfer burns in close proximity. That's high-risk and still leaves a very difficult rendezvous (on a hyperbolic trajectory, not an elliptical one).
- How do you connect the tether, EVA, or a special 100+ ton rated docking mechanism that will definitely be more complex than a bike on a stick.
- If the winch is going to carry the load once the tether is spooled out, it also has to be rated at over 100 tons, if not you'll have to create a different mechanism to detach and lock the tether once it spools out (more complexity, more weight, more cost)
- How much fuel would it take to spin up? To get 100 ton to 100 m/s will take about 3 tons of methane and oxygen (that's per ship and only spin up), so a total of 12 ton for the whole trip.
Do you really need more than 12 ton to build a bike on a stick? And don't forget that we aren't counting the weight of the tether, winch, extra fuel for the rendezvous, etc. so this is a severe under estimate. Also no, you can't save weight by spinning up with reaction wheels, the wheels would end up being heavier than the fuel.
For everyone terrified of tethers… why not just use multiple tethers? Redundancy is a great way to ease concerns.
I just uploaded a follow up video on Thrust based gravity, check it out!
Q: How much time do astronauts need to spend in artificial gravity?
A: Short exposures seem to be adequate to counteract zero-g, the 2nd paper on the right around 0:22 demonstrated that 30 minutes a day was enough to offset the muscle losses we usually see during bed rest studies. "Aerobic exercise capacity" was not maintained but this is probably because they were not moving while in AG, 30-60 minutes on a bike is pretty reasonable given current astronaut schedules and would likely do a better job maintaining "cardio.” I think the best implementation is for use during exercise similar to the MIT concepts around 15:16. This would take the form of an exercise bike or something similar that is on an arm within the starship's 9m diameter. This would further limit balance and motion sickness issues as you'd be on a bike seat and not moving your head side to side.
I won't return to veritasium ever. Dude lies half the time and the other half the time only barely understands what he is talking about.
the problem with conducting things like small centrifuge on earth is that earths gravity fucks with your equilibrium where in space you don't have that problem. Bring a small centrifuge up to space, test the effect IN SPACE to know how it will effect people IN SPACE... FFS, is it really that hard after we put space stations that support astronauts for months at a time, landed on the moon and mars and asteroids?!? (only problem with small centrifuges, they WILL cause a small counter rotation in the space ship when turned on, and attempting to correct that spin in the space ship will cause the small centrifuge to STOP. This is known as conservation of angular velocity for the nerds out there. If the centrifuge can be perfectly centered and turns along the maximum axis of inertia we have no problems, just correct the ships spin by turning off the centrifuge and the next person turns the opposite direction...)
@@anjhindul or just have two counterrotating centrifuges. If you have a large crew of colonists, you'd probably want two anyways.
I agree that, from a pure logic and numbers game, small radius centrifuges are probably the best, but the tethering two starships has one added benefit: it'd probably be nice to be able to walk around during your months long journey to Mars.
If you are smarter than Elon then why are you not the richest man on this planet?
@@nickkorkodylas5005 Firstly, because I didn't have the monetary head start he did, and secondly, because I suck a publicity and charisma. Elon may not be an engineering genius, or a public transit genius, and a lot of his ideas are duds, but he is a skilled businessman and a publicity genius. He has grand flashy ideas and he knows how to get the public hyped over them, then he outsources the actual implementation to people better at engineering and logistics than he is. Also, I think most of these artificial gravity concepts were designed by amateurs, not by Musk's team of engineers. When it comes to Elon, he seems to know when to step back and let the people he pays to be smarter than him step up and do the math for him, he's not going to be trying to implement anything like this without his scientists and engineers verifying that it's at minimum an adequate solution..
Nice discussion and it changed my mind about tethered artificial g. Now I see how unworkable it is. I can only imagine the negative long term effects of short radius artificial g though. Permeant ear changes at the least. Fast transport is the only solution to Mars travel.
I would definitely go with developing a dedicated spaceship for routine journeys to Mars. The mission parameter differences between launching from a planet and voyaging through space are quite wide.
Yeah imagine a big shuttle that many starships could hook up to
As someone with horrible short term memory, i really appreciate the secon reminders at the end
Apart from worrying about gravity, radiation shielding is more important. Cosmic radiation goes through everything and destroys DNA. This is a very destructive radiation that exists in all space. The earth's atmosphere protects us and it cannot be replicated easily.
The atmosphere does not protect earth from "cosmic radiation", and is really just a loose collection of molecules at extremely low density. "Cosmic radiation" or gamma waves have no problem going through that very minor clutter (in it's low amplitude frame of reference) and has a ballpark of one light year of lead to have enough matter density to stop a gamma wave. An entire solar system cannot replicate that.
A magnetic field, which just happens to have a known effect on electromagnetic radiation such as gamma waves, is far more effective at redirecting gamma radiation.
JAGI, you misunderstood what he meant. His claim was not that the atmosphere rather than the magnetic field of the Earth protects from radiation. His claim was that on a trip to Mars the radiation is the main problem, not the missing gravity.
If Lord God Philosopher King Musk says we can spin around like gerbils in a cage then it is written.
May his words spread through the ages and let it be known and true that the Lord God Philosopher King Musk Gave us a Gravity wheel that not only gave us gravity and experience space and gravity in a new way be heth gave us the experience of being a gerbil hazzzaasa
If a cylindrical spaceship is built like a properly insulated hollow capacitor and is highly charged enough that charge interacts with spacetime, it could create artificial weak gravity on either surfaces of cylindrical spaceship without centrifugal force. In theory. It might also allow spaceship to generate artificial magnetic field due to displacement current created by electric flux.
We dont need artificial gravity at all. We just need magnet shoes and a metal walkway. I've been thinking about this for years and i feel like NASA should hire me.
Doesn’t really do much for your eyes or heart
After watching Real Engineering's video on the SpinLaunch, I am fascinated by the discourse on design concerns that people have for certain things. I know some people do comment with their credentials and a really well thought out argument for their point, but I'm really interested in how sometimes the discussion gets side tracked by assumptions in the proposed solution. For example, people were dismissive of SpinLaunch's vacuum chamber based on aerospace testing vacuum chambers, which were orders of magnitude more complex and expensive than the actual needs of the SpinLaunch system. I wonder if the concerns about the tether or the centrifuges could be similar in this case, or if it's all just a reaction from ignorance on the actual science
I think the small centrifuges could work well for people who've gone through the requisite training - which the initial astronauts would almost certainly be, or could definitely add it to the normal training regimen. In the more distant future that could also include people who work in space, or crews of military vessels. It could be like the one in the video or maybe a small rotating sleeping module where everyone's lying down. The larger centrifuges might only be for more permanent residences orbital and commercial passenger craft.
You probably wouldn’t sleep in them, bedrest has the more or less same side effects as zero-g so you would need to be upright for the ag to do much, probably just using it while exercising
@@ConHathy The problem with the small ones is it ONLY addresses muscle and bone loss. There will still be the issues with the eyes and fluid distribution in the body. All one has to do is apply logic to see the truth of this. Would it be better than nothing? Definitely much better but the larger ones are going to be necessary for long term health, both mental and physical, of astronauts spending years in space altogether and those who end up living their lives there. I agree that the smaller centrifuges will be the best way to do it for now due to general feasibility but they are a poor choice at best as a long term solution.
If you've ever swung a weight on a line, you know there's no tumbling when you let go. The mass moves directly away when released. The string doesn't coil as the mass spins, the mass remains spinless as it moves in a straight line away from the spinning center. As far as the mass is concerned, it's always moving straight away from the center, it doesn't perceive it's spinning motion in it's inertia. It's the line holding it to the center that is forcing a straight away motion to instead appear to the outside observer as a lateral motion. To the mass, it's always straight away from center.
Well that’s just not true, look at hammer throwing. If it’s a light object maybe the drag from the line will stabilize it but that obviously wouldn’t happen in space. Angular momentum is conserved so a rotating object is going to keep rotating unless you apply a torque to stop it
Nice. Glad this popped up on my feed. You have a new subscriber. Thanks, algorithm!
The ring type seems legit. And for the record. I discovered it as a child. Playing with a bike tire. I noticed that the rain water stayed in when I sent it flying across the yard. So I got the hose pipe and experimented. It works even with Earth's gravity trying to pull it out. It works sideways here on earth. You will get wet but it will hold some until it lands. Just remember too spin it.
Going on a tangent while talking about spinning in circles made me chuckle.
I really like this guy, he taught me things
Thanks for telling us about the short radius centrifuge research - i really believed that would never work
What a wonderful video with simple explanations of things so many common misconceptions!
I agree that tethered spacecraft definitely appear to be the best, the cheapest, the most lightweight and the most practical solution. This is especially the case if the generated 'artificial gravity' is lowered to less than one G, allowing for smaller diameters and much lighter (tethering) structures while still providing major benefits for physical and mental health (along with other measures like fitness workouts weightlifting etc) similar to those astronauts conduct in 0G environments to remain healthy for longer periods.
I would strongly suggest considering tethering more than just two spaceships (or space modules rather) though!
The most likely solution that I personally think will prove most practical, is tethering at least four, maybe even 5 or more modules together into a structure (maybe with some modules experiencing near 0 or low gravity in/near the center of the structure).
The result would be a modular structure which is in a way very similar to the ISS, but with the modules tethered and rotating.
Such a type of vehicle design would not only allow for final assembly in space, but it would also allow for a similar strategy as the Moon landings with modules of the vehicle remaining in orbit, and just one or two of the spaceships/space modules detaching for the trip down to the planet.
Such a design would of course also allow for each of the sections to be optimized for their special purposes, and it would allow for at least some limited implementation of a few mission critical redundancies, greatly improving mission safety aspects.
Furthermore can the tethering structures (easily) be designed for transfer of resources (fuel, water, oxygen food), energy, and data from one module to another during the trip, in return for waste products going back the other way to maintain balance of the rotating masses.
Maybe even more importantly though, would it allow for some of the sections to be left behind at various stages of the journey.
This (just like any other viable design will similarly require to be practical and efficient) allows to leave structures containing large portions of waste, (used) fuel, (used) food, and other used up resources or equipment behind.
This will make the vehicle for the return trip much smaller and much lighter (and it would even already allow reducing the ship's mass before 'decelerating' or entering the orbit of Mars). This will make the overall concept very (fuel) efficient, while at the same time retaining all the necessary (tethering) dimensions of the artificial gravity design concept, only with (far) fewer tethered (and spinning) modules on the return trip.
I liked the design of the hail Mary for smaller-scale ships
Tether design....
Pros: Efficient, sustainable and within current technologies
Cons: makes corrections in course more complex procedures, runs the danger of absorbing and expressing momentum from small impacts, requires extreme maintenance
Until spacecraft are like battle ships in crew area size, artificial gravity outside the short centrifuge would be more trouble than it was worth, ideally you want the mass of your vessel to be enough to absorb most of the rotational energy exerted upon the center of the crafts center of mass and center of gravity. You would have areas in the craft that are gravity zones because of what ever localized complex moving gravity chamber centrifuge things. Spinning requires alot of fuel to stop in order to perform other tasks that a spinning top cannot, like docking and space walks.
Generally speaking, objects do *not* tend to move towards lower energy states. As we know, energy is a conserved quantity, but if objects tended to go towards lower energy state, the total energy of all objects would decrease, which we know that it cannot do.
05:58 long axis rotation would work with a some changes to the problems you mentioned:
1. Leave certain sections of the cabin in the "upright" configuration for takeoff and landing, and store equipment securely to compensate for the direction of spin... while utilizing the center of the craft as the common area to reside in while the ship is rotating.
2. Don't use liquid fuel. Use a solid propellant.
Good luck landing with solid fuel
doesn't a short radius have a greater variation of g's across the length of the body? as the head is moving at a relatively and significantly slower speed than that of the feet. or do the g's come from the point of contact ie the floor? just curious.
Centrifugal force still requires friction to impart force on the occupants. A rotating disk on earth spinning imparts centrifugal force on it's surface due to the force of gravity on earth. Simply spinning a disk in zero gravity will not impart any force on bodies unless they are tethered to the disk in some way. So rather than walking around the outside wall occupants would need to walk on perpendicular walls along radials. The spinning wall would then collide with and impart a constant force on the occupants. However the force would change depending on position along the radial axis.
So the depicted diagram with star ships tethered end to end would actually collide with occupants from the side walls which are aligned with the radials of the axis of rotation. This could all be solved by rotating the habitation module internally instead of rotating the entire ship.
So just to be clear the force imparted on the occupants would first be perpendicular to the centrifugal force. Once friction occurs between the occupants and radial walls there would be a centrifugal force imparted as well. So if there were no radial walls you could jump from the outer ring and still be spinning at the speed of the outer ring but there would be no force to push you back out to the outer ring if you are suspended in zero gravity. You would just be spinning while jumping across the ring from side to side. The centrifugal force only works if there is friction.
1) You do not need any fuel to start/stop spinning - Electric power is enough. You need some mass that will carry a contra-rotating moment (like reaction wheel or second pair of tethered starships) and an electric motor to start-stop the rotation as You please. To keep everything safe and stable you detach masses during cruise phase.
2) When the tether brakes You are dead, due to elasticity of any rope material. The loose end will hit the ship with pinpoint precision and all the energy stored in the rope itself.
You could technically use electric power to spin up but it is necessary less mass efficient than thrusters. The exhaust of the thrusters is leaving at over a kilometer per second, to match that efficiency with a reaction wheel it would have to be the same radius as the entire vehicle and would also spin at over a kilometer per second which is impractical
Gravity also makes alot of tasks easier to perform. If there's no or very little zero g in the misson profile, they can eat crunchy foods, use grinding tools, worry MUCH less about martian dust, etc
Drink from normal cups, grow plants that have fewer problems, use normal tools faster.
Skateboarders know all about the intermediate axis. Spinning the board around the other two axis are some of the first tricks you learn, flipping the board around the intermediate axis is called "The Impossible."
Very interesting thank you for the quality
Interesting and slightly different than what I was jotting down for a short story idea. 4 ships tethered along the center of gravity to a central hub. The hub is a sphere that contains communication hard connections between each ship and mission control until the ships disconnect and start final approach to the new planet.