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Old 17th January 2020, 04:51 PM   #41
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Originally Posted by Giordano View Post
Has anyone yet mentioned that the Coriolos effect would might produce some strange sensations when walking in a rotating environment designed to produce “artificial gravity?
It depends on how big the ring is.
Originally Posted by Meadmaker View Post
...
One of the things I find amusing in science fiction is that when spacecraft start getting his with enemy weapons, they might lose power. The warp engines go off line. The lights fail. At some point there is only enough power for life support, and that is about to go, and everyone will die unless someone can effect repairs before the last commercial.

But the gravity generators never go offline, even in ships that have been adrift in space for hundreds of years.
In all the Star Trek I've seen (almost 100% up to two years ago) I can recall gravity being a story point only once. I think it was the premiere of Enterprise, where Travis found a "sweet spot" (null gravity) on the ship where he'd go to relax, and said every ship had one.
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Last edited by alfaniner; 17th January 2020 at 04:54 PM.
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Old 17th January 2020, 04:52 PM   #42
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One of the things I find amusing in science fiction TV shows is the amusing stories they can tell, even if their production budget doesn't stretch as far as realistic zero gravity.

It always strikes me as weird and a little depressing, the way so many people seem to think TV producers are too ignorant, or just don't care enough, to produce convincing low gravity effects.
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Old 17th January 2020, 04:57 PM   #43
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Originally Posted by theprestige View Post
You tell us. What were the results, when you searched the thread for the word "coriolis"?
Pardon? I had read the full thread and did not notice mention of the Coriolis effect. However I thought that perhaps I might have missed such a mention, particularly if the word had not been used but the effects had been described. So I tried to be polite and cautious in launching my post.

Perhaps I didnít make it clear enough that I was noting that these effects would exist, not simply asking if they had been mentioned or not?

Now that Iíve clarified this we can move on. Unless Iím missing the actual point of your post?
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Old 17th January 2020, 05:13 PM   #44
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Originally Posted by Armitage72 View Post
Physicist and science fiction writer Robert Forward wrote a book called "Indistinguishable from Magic", that alternated scientific essays about hypothetical advanced technologies common in science fiction and short stories featuring those technologies. As I recall, the artificial gravity chapter involved somehow manufacturing hyperdense matter and placing it in a thin layer under a surface, with sufficient mass that it generated gravity pulling toward that surface. It couldn't be turned on and off though.
Originally Posted by Mike! View Post
I was thinking along the same lines, what if you had a piece of hyper-dense matter located someplace around the central core of the craft that would in essence, attract everything loose towards that central point?
You do see the problem with that though, right? If you have enough hyper-dense matter to create significant gravity, your spaceship is going to weigh as much as a small planet, and it will be much harder to maneuver and accelerate or decelerate.
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Old 17th January 2020, 05:17 PM   #45
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The best sci-fi has this covered.

You accelerate at up to 1 G until you're half way to your destination.

Everyone straps down and the ship flips over end to end.

Then you decelerate at the same rate until you arrive at your destination.

This way your ship doesn't need moving parts that are destined to fail, and really horrible interfaces between moving parts and non moving parts. It also means you don't have to have the universe spinning around outside your windows. AND it means that your ship can have common 'floor' surfaces that are always in the right place.
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Old 17th January 2020, 05:18 PM   #46
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Originally Posted by Giordano View Post
Pardon? I had read the full thread and did not notice mention of the Coriolis effect. However I thought that perhaps I might have missed such a mention, particularly if the word had not been used but the effects had been described. So I tried to be polite and cautious in launching my post.

Perhaps I didnít make it clear enough that I was noting that these effects would exist, not simply asking if they had been mentioned or not?

Now that Iíve clarified this we can move on. Unless Iím missing the actual point of your post?
You want to talk about the coriolis effect. Instead you're talking about talking about the coriolis effect. Does that make any sense to you?
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Old 17th January 2020, 05:25 PM   #47
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Originally Posted by novaphile View Post
The best sci-fi has this covered.

You accelerate at up to 1 G until you're half way to your destination.

Everyone straps down and the ship flips over end to end.

Then you decelerate at the same rate until you arrive at your destination.

This way your ship doesn't need moving parts that are destined to fail, and really horrible interfaces between moving parts and non moving parts. It also means you don't have to have the universe spinning around outside your windows. AND it means that your ship can have common 'floor' surfaces that are always in the right place.
I can't think of any top tier SF that does this.

Mainly because the fuel requirements for constant 1G acceleration over interstellar distances are not in the realm of good SF.

Also because you'd reach light speed long before you reached even Alpha Centauri.

Also because you'd disintegrate from relativistic effects and particle impacts somewhere around 25Č of light speed.

Unless you're talking about Larry Niven. In that case, I'll give you a pass.
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Old 17th January 2020, 05:31 PM   #48
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Originally Posted by RecoveringYuppy View Post
Warning, more pedantry.

Originally Posted by Puppycow View Post
Maybe you can use the electromagnetic force, like in The Expanse, but that force acts differently from the force of gravity. It's very strong up close, but weakens quickly with distance.
Actually EM and gravity obey the same inverse square law. The difference arises because you can create an EM in a very small space but creating a gravity well requires a huge object. The large radius of the Earth vs the potentially very small radius of magnets leads to the difference you are talking about.

The "hyperdense matter" solutions that some people have mentioned in this thread would have the same fall off problem you mention here (assuming same size). Similarly, you can avoid the fall off problem with an EM solution by making the magnet large.
Thanks. So, conceivably, if you had people wear clothes made out of magnetic materials and put magnets in the "floor" . . . ? But that probably still wouldn't work because of the polarity problem. Magnets have 2 poles and one attracts but the other repels. It's not like gravity that just attracts everything with mass.
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Old 17th January 2020, 06:41 PM   #49
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Originally Posted by novaphile View Post
The best sci-fi has this covered.

You accelerate at up to 1 G until you're half way to your destination.

Everyone straps down and the ship flips over end to end.

Then you decelerate at the same rate until you arrive at your destination.

This way your ship doesn't need moving parts that are destined to fail, and really horrible interfaces between moving parts and non moving parts. It also means you don't have to have the universe spinning around outside your windows. AND it means that your ship can have common 'floor' surfaces that are always in the right place.
Completely impractical. Take whatever propulsion technology you're planning on using and consider how much fuel you'll need to carry to maintain constant acceleration over the time span of your trip. Don't forget to use the rocket equation.

Even if you could somehow produce large quantities of anti-matter, and store them safely for years on your spacecraft, this still wouldn't make sense. I don't think it would work even with something like a light sail powered by lasers back home (consider that the faster you go, the more redshifted the light from those lasers becomes, so they need to be more powerful to produce the same acceleration), but I haven't actually looked at those numbers so... maybe.

There are also the concerns related to traveling at relativistic velocities through interstellar space that theprestige mentions. So, you solve the problem of having your view through your windows spinning by carrying insane amounts of fuel and turning every speck of dust along your path into a nuclear warhead. Doesn't seem worth it to me.

The only reason to try to go very fast is some sort of time constraints. And the difficulty in doing so is immense.

My personal solution to interstellar travel is to take very long journeys at a slow pace. Hundreds of km/s instead of tens of thousands.
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Old 17th January 2020, 07:18 PM   #50
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Originally Posted by Roboramma View Post
My personal solution to interstellar travel is to take very long journeys at a slow pace. Hundreds of km/s instead of tens of thousands.

Yeah, but then your trip takes millennia instead of decades. You'd have to bring a Robert Jordan novel or something.
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Old 17th January 2020, 07:28 PM   #51
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Originally Posted by Roboramma View Post
Completely impractical. Take whatever propulsion technology you're planning on using and consider how much fuel you'll need to carry to maintain constant acceleration over the time span of your trip. Don't forget to use the rocket equation.
I hate the rocket equation.


Ok, so, last year I took an online class on space mission planning, and learned what the rocket equation was, and realized just how incredibly hard interstellar travel was.

It's all the equation's fault. If we could just get rid of the equation we could make it work.
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Old 17th January 2020, 09:47 PM   #52
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Originally Posted by Giordano View Post
Has anyone yet mentioned that the Coriolos effect would might produce some strange sensations when walking in a rotating environment designed to produce ďartificial gravity?
That is a good point actually. For example if a person throws a ball vertically upwards it will not come down in the same spot, like it would on earth. It will start having a horizontal vector from the thrower's point of view. A ball thrown at an angle would have a strange path. It could also produce motion sickness if a person is going up or down.

Not to mention the fact that a person's feet would have greater gravity than the person's head.

The frustrating thing is that I tried to do a google search and though found a bit on the Coriolis effect, not much about the strange effects it would have on humans in a spacecraft.
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Old 17th January 2020, 09:52 PM   #53
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Originally Posted by Myriad View Post
Yeah, but then your trip takes millennia instead of decades.
Yep. And just to get to a single nearby star.

Quote:
You'd have to bring a Robert Jordan novel or something.
Or maybe even several.
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Old 17th January 2020, 09:58 PM   #54
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Originally Posted by Lothian View Post
Rubbish. It is all explained by the diagram below.

https://cdn.vox-cdn.com/thumbor/bKdL...ierimg.0.0.gif
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Old 17th January 2020, 09:59 PM   #55
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Originally Posted by sphenisc View Post
I seem to manage it.
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Old 17th January 2020, 10:02 PM   #56
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Originally Posted by Steve001 View Post
The nature of gravity is unknown and the question you've asked is open.
Aha! This gives me a well-into-the-future sci-fi idea. Perhaps humans will one day harness dark matter and use it to create artificial gravity.

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Old 17th January 2020, 10:06 PM   #57
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Originally Posted by Armitage72 View Post
Physicist and science fiction writer Robert Forward wrote a book called "Indistinguishable from Magic", that alternated scientific essays about hypothetical advanced technologies common in science fiction and short stories featuring those technologies. As I recall, the artificial gravity chapter involved somehow manufacturing hyperdense matter and placing it in a thin layer under a surface, with sufficient mass that it generated gravity pulling toward that surface. It couldn't be turned on and off though.
Interesting. Harnessing black hole material.

Maybe add some king of mag-lev device that counters it to shut it off.
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Old 17th January 2020, 10:11 PM   #58
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Originally Posted by 3point14 View Post
And it'd play havoc with your DeltaV
Good point. So it would have to be created in space and stay up there.

You would though, have the problem that the gravity made from some hyper-dense material would pull both ways. You might have an issue collecting space rocks on the hull.

I'd have the same problem with my dark matter device.
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Old 17th January 2020, 10:18 PM   #59
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Originally Posted by Loss Leader View Post
The problem with that gravity (and The Martian and others) is that you're always walking uphill.


But it's spinning, so it's like a treadmill moving under you. If you stand still you aren't even walking.


Rendezvous With Rama has an interesting description of the gravity you'd have with a miles long cylinder that was also spinning to create the gravity. You have to read it, it's too complicated to describe. It was different though, in that it wasn't the usual wheel shape.
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Old 17th January 2020, 10:21 PM   #60
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Originally Posted by Skeptic Ginger View Post
Aha! This gives me a well-into-the-future sci-fi idea. Perhaps humans will one day harness dark matter and use it to create artificial gravity.

Where are you and Steve001 getting the idea that we don't understand gravity?

General Relativity gives us a powerful theortetical framework that has been tested to enormous precision. We can measure the time dilation across a distance of a few meters in the earth's gravitational field, gravitational waves from colliding black holes, the motions of the planets and artificial satellites and spacecraft in our solar system, precision experiments like Gravity Probe B, stars orbiting Sagittarius B*, the patterns in the CMB, etc. etc. and we don't have a single measurement that is inconsistent with GR.

There are some issues with quantizing gravity, but there is absolutely no reason to expect that quantum gravity would open the door to artificial gravity, other than of the mundane sort produced by acceleration which we already know how to produce (for instance in a rotating cylinder).
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Old 17th January 2020, 10:30 PM   #61
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Originally Posted by Roboramma View Post
Where are you and Steve001 getting the idea that we don't understand gravity?
Where did you read me saying that?

I said harnessing dark matter.
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Old 17th January 2020, 10:59 PM   #62
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Originally Posted by Skeptic Ginger View Post
Where did you read me saying that?
Well, Steve001 said: "The nature of gravity is unknown and the question you've asked is open." and you seemed to be agreeing with him. Maybe I misunderstood.

Quote:
I said harnessing dark matter.
Dark matter's behavior and interaction with respect to gravity is no different to normal matter. Dark matter is only special in the sense that it doesn't interact with the electromagnetic force (hence "dark"). Energy causes spacetime to curve, and dark matter, ordinary matter, light, all of these things have energy.

You did suggest that your idea could be similar to the idea of having some extremely dense matter as a source of gravity. I agree that there's nothing in the laws of physics that would prevent that, but it's not really artificial gravity, it's just normal gravity. We have gravity on the earth because there's a huge mass beneath our feet. The problem with doing that on a spacecraft is that you'd need a similarly huge mass, and if you want to move your spacecraft you don't want to have to move a mass comparable to the mass of the earth.

I guess I'm exaggerating slightly: You wouldn't need something quite on the order of the mass of the earth, because the distance from the center of mass would be much less. But let's say that you concentrated your mass into something 1 meter in thickness*. The radius of the earth is, what, 6,000,000 meters? Gravity is proportional the the square of the distance, so if we're 6 million times closer, the force should be 3.6x1013 times greater, meaning we need 1/3.6x1013 of the earth's mass to produce 1 g.

One thirty six trillionth sounds like a small fraction, but as a fraction of the mass of the earth it's still an enormous mass. Whether you're supplying that mass with ordinary matter or dark matter, or with theprestige's idea of taking a diffuse energy source and concentrating it (maybe you're firing lasers through tubes in the floors) when and where you need it, you're still having to deal with that enormous amount of mass (or energy).

*never mind how you actually accomplish that. It's an engineering issue.
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Old 17th January 2020, 11:12 PM   #63
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Originally Posted by Roboramma View Post
Well, Steve001 said: "The nature of gravity is unknown and the question you've asked is open." and you seemed to be agreeing with him. Maybe I misunderstood.
Yeah, sorry about that. I quoted him because the post he answered gave me an idea. Not your fault, I shouldn't have quoted anyone.


Originally Posted by Roboramma View Post
Dark matter's behavior and interaction with respect to gravity is no different to normal matter. Dark matter is only special in the sense that it doesn't interact with the electromagnetic force (hence "dark"). Energy causes spacetime to curve, and dark matter, ordinary matter, light, all of these things have energy.

You did suggest that your idea could be similar to the idea of having some extremely dense matter as a source of gravity. I agree that there's nothing in the laws of physics that would prevent that, but it's not really artificial gravity, it's just normal gravity. We have gravity on the earth because there's a huge mass beneath our feet. The problem with doing that on a spacecraft is that you'd need a similarly huge mass, and if you want to move your spacecraft you don't want to have to move a mass comparable to the mass of the earth.

I guess I'm exaggerating slightly: You wouldn't need something quite on the order of the mass of the earth, because the distance from the center of mass would be much less. But let's say that you concentrated your mass into something 1 meter in thickness*. The radius of the earth is, what, 6,000,000 meters? Gravity is proportional the the square of the distance, so if we're 6 million times closer, the force should be 3.6x1013 times greater, meaning we need 1/3.6x1013 of the earth's mass to produce 1 g.

One thirty six trillionth sounds like a small fraction, but as a fraction of the mass of the earth it's still an enormous mass. Whether you're supplying that mass with ordinary matter or dark matter, or with theprestige's idea of taking a diffuse energy source and concentrating it (maybe you're firing lasers through tubes in the floors) when and where you need it, you're still having to deal with that enormous amount of mass (or energy).

*never mind how you actually accomplish that. It's an engineering issue.
I was talking about sci-fi idea a few hundred years or more in the future. That means speculating about elements of dark matter we don't yet know about: like maybe something to do with extra dimensions quantum theory suggests.

You have more details obviously, but I was speculating about some things one can imagine might fit physics. Like how hyperspace is a valid concept even though we can't fold space-time yet.
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Old 18th January 2020, 02:19 AM   #64
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Originally Posted by Lothian View Post
Have you never gravitied from 0 to 40 between the lights on Sauchiehall street?
No, but in my younger days, I pub-crawled the length of it.

Does that count?
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Old 18th January 2020, 02:38 AM   #65
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Originally Posted by smartcooky View Post
No, but in my younger days, I pub-crawled the length of it.

Does that count?
Certainly. I can verify that pub-crawling generally tends to have a big effect on gravity making walking quite tricky.
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Old 18th January 2020, 03:47 AM   #66
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Originally Posted by Mike! View Post
I was thinking along the same lines, what if you had a piece of hyper-dense matter located someplace around the central core of the craft that would in essence, attract everything loose towards that central point?
The other problem with this is inorder to have appreciable gravity your craft has to haul around the mass of a small planetoid, minimum. That's going to give your slick, powerful space craft the acceleration, braking and handling of a 1950's Cadillac running on one cylinder with the trunk and backseat filled with lead weights.

ETA: Ninja'd by Puppycow.
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Old 18th January 2020, 03:56 AM   #67
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Originally Posted by novaphile View Post
The best sci-fi has this covered.

You accelerate at up to 1 G until you're half way to your destination.

Everyone straps down and the ship flips over end to end.

Then you decelerate at the same rate until you arrive at your destination.

This way your ship doesn't need moving parts that are destined to fail, and really horrible interfaces between moving parts and non moving parts. It also means you don't have to have the universe spinning around outside your windows. AND it means that your ship can have common 'floor' surfaces that are always in the right place.
One of the details I loved about "Rendezvous with Rama" was that the height of the 'cliffs' on either side of the central sea allowed them to calculate the maximum acceleration and deceleration of the craft. Of course that's assuming it doesn't have a second burst once the water is frozen.
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Old 18th January 2020, 04:24 AM   #68
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Originally Posted by Puppycow View Post
You do see the problem with that though, right? If you have enough hyper-dense matter to create significant gravity, your spaceship is going to weigh as much as a small planet, and it will be much harder to maneuver and accelerate or decelerate.

Good point. It would probably massively reduce the DeltaV of such a craft...
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Old 18th January 2020, 08:46 AM   #69
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Originally Posted by Roboramma View Post
Where are you and Steve001 getting the idea that we don't understand gravity?

Even if SG didn't mean what she appeared to there are still an unusual number of people expressing the idea that we don't understand gravity. We've understood it well enough theoretically since the time of Newton. And we've been producing artificial gravity (without realizing it) since prehistoric times (such as slings described in the David vs. Goliath story).
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Old 18th January 2020, 09:17 AM   #70
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Originally Posted by rjh01 View Post
That is a good point actually. For example if a person throws a ball vertically upwards it will not come down in the same spot, like it would on earth. It will start having a horizontal vector from the thrower's point of view. A ball thrown at an angle would have a strange path. It could also produce motion sickness if a person is going up or down.
[... snipped something I'll come back to...]
The frustrating thing is that I tried to do a google search and though found a bit on the Coriolis effect, not much about the strange effects it would have on humans in a spacecraft.
The things you mentioned are also true to a smaller degree on Earth. It's just a matter of degree. And these affects and others were studied to a great degree back in the 70s.

How much you experience these affects on a space craft is a matter of it's rotation rate and radius. Studies in the 70s pretty came to the conclusion that 1 RPM was the highest rotation we could live well with. To get 1G at that rate you need a radius of half a mile.

The space station shown in 2001 A Space Oddysey was producing 1/6G (Moon gravity) if I recall correctly. Scaling that up to produce 1G means that style of station would be a torus a mile in diameter. You would have a 3 mile circumference so that would be the longest you could walk to get back to your starting point. It would be large enough to accommodate 10,000 people in an urban setting. If the occupants were prepared to accept something like aircraft carrier living conditions it might accommodate 50,000.

It would mass something like 20 million tons and most of that would be radiation shielding. It would require about 2 million tons of refined materials such as aluminum, titanium, and glass. If spread over 5 to 10 years that's not a large amount of refining industrial speaking. By Earth standards that would be a small mine on the moon and a small refinery/smelter somewhere in space.

And, this may be hard to believe, but it's not out of the question that we could launch 2 million tons of refined materials from Earth over that material and just get the slag for radiation shielding from the Moon or passing asteroid. It would require twice daily launches of the largest rocket ever designed for five years. Approximately 4,000 launches. Committing to 4,000 launches would be a game changer, it would make it possible for designers to invest in an assembly line approach. It could potentially put us at the point that fuel is the dominant cost of a launch which is very far from where we are now.

Originally Posted by rjh01 View Post
Not to mention the fact that a person's feet would have greater gravity than the person's head.

This is negligible in a large station. And it can also be put to advantage. The 1G area can be reserved for people to live in. Farming and industry could be in cheaper low gravity sections of the station. Low and zero G recreation and training areas are possible and accessible by a simple elevator ride.

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Old 18th January 2020, 12:10 PM   #71
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Originally Posted by rjh01 View Post
That is a good point actually. For example if a person throws a ball vertically upwards it will not come down in the same spot, like it would on earth. It will start having a horizontal vector from the thrower's point of view. A ball thrown at an angle would have a strange path. It could also produce motion sickness if a person is going up or down.

Not to mention the fact that a person's feet would have greater gravity than the person's head.

The frustrating thing is that I tried to do a google search and though found a bit on the Coriolis effect, not much about the strange effects it would have on humans in a spacecraft.
What you describe is exactly what I was thinking about as "strange effects." Essentially that our expectations of the path of moving objects, and probably our inner ear sensing of our own movements, will likely be different from those on Earth. I was only trying to point this out very generally and I thank you for clarifying my post. The precise effects of course depend on the details of the spinning environment and on the specifics of the moving objects.

Last edited by Giordano; 18th January 2020 at 12:13 PM.
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Old 18th January 2020, 12:13 PM   #72
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Originally Posted by RecoveringYuppy View Post
The things you mentioned are also true to a smaller degree on Earth. It's just a matter of degree. And these affects and others were studied to a great degree back in the 70s.

How much you experience these affects on a space craft is a matter of it's rotation rate and radius. Studies in the 70s pretty came to the conclusion that 1 RPM was the highest rotation we could live well with. To get 1G at that rate you need a radius of half a mile.

The space station shown in 2001 A Space Oddysey was producing 1/6G (Moon gravity) if I recall correctly. Scaling that up to produce 1G means that style of station would be a torus a mile in diameter. You would have a 3 mile circumference so that would be the longest you could walk to get back to your starting point. It would be large enough to accommodate 10,000 people in an urban setting. If the occupants were prepared to accept something like aircraft carrier living conditions it might accommodate 50,000.

It would mass something like 20 million tons and most of that would be radiation shielding. It would require about 2 million tons of refined materials such as aluminum, titanium, and glass. If spread over 5 to 10 years that's not a large amount of refining industrial speaking. By Earth standards that would be a small mine on the moon and a small refinery/smelter somewhere in space.

And, this may be hard to believe, but it's not out of the question that we could launch 2 million tons of refined materials from Earth over that material and just get the slag for radiation shielding from the Moon or passing asteroid. It would require twice daily launches of the largest rocket ever designed for five years. Approximately 4,000 launches. Committing to 4,000 launches would be a game changer, it would make it possible for designers to invest in an assembly line approach. It could potentially put us at the point that fuel is the dominant cost of a launch which is very far from where we are now.
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Old 19th January 2020, 07:35 PM   #73
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Originally Posted by theprestige View Post
I can't think of any top tier SF that does this.
The Expanse

Originally Posted by Roboramma View Post
Completely impractical. Take whatever propulsion technology you're planning on using and consider how much fuel you'll need to carry to maintain constant acceleration over the time span of your trip. Don't forget to use the rocket equation.
The Expanse gets around this with their Epstein Drive
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Old 20th January 2020, 07:22 AM   #74
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Originally Posted by PhantomWolf View Post
The Expanse



The Expanse gets around this with their Epstein Drive

The Battletech universe also uses it, but only for interplanetary travel. For most inhabited star systems, it's 3-4 days at 1 G acceleration (with a ridiculously efficient fusion torch drive), a flip-over, and then 3-4 days of 1 G acceleration in the opposite direction to stop. Interstellar travel uses nearly immobile ships that carry the transports as they jump through hyperspace 30 light-years at a time, with a week to recharge after each jump, and maintaining a significant distance from a system's star.
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Old 20th January 2020, 07:43 AM   #75
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TBH, that's why I keep mentioning that I favour just hollowing out an asteroid and giving it a spin, whenever this kind of idea about living in space comes about. We can easily find one larger than a mile across, and it would probably cost a lot less to send a few robots ahead to dig tunnels into one, than to send up all the materials to make a pretty torus in the sky.

On the other hand for interstellar travel, I'm surprised they don't use the centrifuge idea more often. The Enterprise D for example is already half a mile in size, so it could have half a g or so by just spinning the saucer. Because, yeah, you can also put the saucer sideways to minimize drag instead of moving the ship along the torus axis.
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Old 20th January 2020, 07:48 AM   #76
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Do you think you can find an asteroid a mile across that won't fall apart if you spin it enough to get 1G?
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Old 20th January 2020, 09:24 AM   #77
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A 1 mile across one? Almost certainly not. A 600 mile across one like Ceres on the other hand? Well, I'm thinking it would probably hold together. We're talking 1/600 RPM at that point, or one spin every 10 hours.
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Old 20th January 2020, 09:28 AM   #78
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Why the heck would you think that? And I think you forgot to account for Ceres existing gravity?

ETA: Every description of Ceres' mantle that I can find suggests rotating Ceres at that rate would simply rip it apart. And I can't think of anyway to get it to spin that fast without destroying it in the process before the spin destroys it.

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Old 20th January 2020, 10:06 AM   #79
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Originally Posted by Puppycow View Post
You do see the problem with that though, right? If you have enough hyper-dense matter to create significant gravity, your spaceship is going to weigh as much as a small planet, and it will be much harder to maneuver and accelerate or decelerate.
I did give it some thought, not much mind you, but, it went along the lines of, does it matter what the craft/ship weighs in space all that much? Since I'm not smart enough to know, I let it go at that.
What if the hyperdence matter was made in ultra thin sheets at the sweet spot between thick enough to generate a gravitational field but thin enough to be manageable? Since it seems mass is the key, and not size. Right?
I think there's a marketing slogan in there someplace... "It's hyperdence, yet ultra thin design..."
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Old 20th January 2020, 11:45 AM   #80
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Originally Posted by HansMustermann View Post
A 1 mile across one? Almost certainly not. A 600 mile across one like Ceres on the other hand? Well, I'm thinking it would probably hold together. We're talking 1/600 RPM at that point, or one spin every 10 hours.
Forget the rotation rate, rotation isn't what tears it apart, the "artificial gravity" being in the opposite direction is. Whatever you rotate has to be a single solid chunk of metal strong enough to hold it's own weight being pulled outward. Any asteroid that is a "rubble pile" is instantly out of the question.
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