1. chad.sims2
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    chad.sims2 Contributing Member

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    Artificial gravity in Space!

    Discussion in 'Research' started by chad.sims2, May 31, 2008.

    Ok this should get some interesting responses. I can only think of one actual way to create artificial gravity in space, but i know there are many(Theroeticaly) so could some one help me out?

    The way I know will work is also the simplest. Spin! Lets say you make a space station the shape of a roll of toilet paper and while in space spin it like a wheel. Anything inside the station would be pulled towards the outside of the station those producing gravity of a sort. So if you made the station so that the floor was always the out side of the cone and kept it spinning then you could have a decent place to live with gravity and all.
     
  2. Al B
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    Al B Senior Member

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    The centrifugal force method you describe is probably the most common idea for it, but it does force (no pun intended) you to have 'wheel' or saucer-shaped spacecraft. Failing that, at least a rotating chamber somewhere on the craft. This option is the one currently favoured by NASA and other space agencies, who would need crews on long space flights to exercise daily in a small radius rotating part of the ship in order to retain stuff such as healthy heart functions etc, which debilitate in zero gravity. Other options are simulating it for the crew in a very basic form with magnetic/electromagnetic boots and steel decks, although this is only of use for assisting in work, and would have no practical health benefits for long space journeys.

    If you're looking for fictional explanations for more of a science fiction approach with the emphasis on fiction, you could suggest having a heavy element in the floor of a craft which was dense enough to exert some gravitational pull, although it would really be 'blagging it' a bit in terms of real practical science. Or even an electromagnetically created gravitational field similar to the theoretical means which is often suggested as the possible propulsion on 'flying saucers'.

    Another way to have it in a fictional setting, which is slightly more believable, would be to have the crew quarters perpedicular to the line of travel, and have the ship constantly under 1G acceleration.

    Or, you could simply do what every other sci-fi book and film does, and just not even mention the 'science' behind it.

    Al
     
  3. TMA-1
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    TMA-1 New Member

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    Well, a gravity field is easy to create, all you need is something with restmass... the downside is, you need a lot of it. But seriously, I have no clue how to create an artificial gravity field. Most ideas I had have been mentioned already. Maybe in the future we will understand gravity well enough to create it artificially. The spin method is possible and maybe necessary on long space journeys. It doesn't create a gravity field (not enough mass to be noticed, though it should warp spacetime, but so little no one would notice) but the illusion should be good enough on that scale.
     
  4. Cogito
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    Cogito Former Mod, Retired Supporter Contributor

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    The only methods that are supported under what we know of science right now involve acceleration. The rotating ring/drum is the only method usable for a structure in a fixed location (orbit or free-floating) The acceleration in that case is due to the centrpetal force that keeps the station in one piece as it rotates. Changes in direction

    The other acceleration method is to accelerate at a contant rate, 9.8 meters per second per second for normal Earth gravity. This may be practiacl for interplanetary flight, but not interstellar journeys. In this case, you would accelerate for half of your journey, then you would have a period of zero gravity in mid flight during which the ship would turn the ship around, then you would decelerate for the rest of the journey. This method only works if you can plan the entire journey before setting out; course corrections require changes to acceleration, and any type of pursuit or battle maneuvering would mean huge shifts in the strength and direction of "gravity"

    The massive material under the decks would require a great deal of mass, and the engines wuld have that extera mass to move around. Also, the gravity would be strongest right at the deck, and a few inches higher it would drop off sharply. Magnetic boots would work about the same way without the mass penalty.

    Most SF postulates an artificial gravity generator based on science that has not yet been discovered.
     
  5. chad.sims2
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    chad.sims2 Contributing Member

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    Thanks for the coments, i'm a big supporter of SciFi where science and beliveability are focused on greatly. Most of the older scifi books tried to stay vary close to realistic but many of the newer ones just seem to unlikly. I think that scifi that is more fiction than science is really just fantasy with a futureistic setting. Scifi is definded by being logicaly plasible, if not nessicarily likly. In my opionion.
     
  6. NaCl
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    NaCl Contributing Member Contributor

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    Believable? Plausible?

    I am 60 years old. The first television I watched was black&white and it only had twelve channels, of which, only four had programming...the rest were just static. Our telepone was a "party" line which we shared with numerous other families. All food was "cooked" by a heat source...electricity, gas, charcoal or wood. There were no microwaves, no personal computers, no CD's, no satellite anything, no space exploration, no VCR's, no cable TV, no copy machines (only mimeograph machines), no jet-based airlines (only propeller planes like the DC4 and Convair 240...the new DC6 carried over 50 people!), no calculators, no GPS,....you get my drift.

    Einstein's General Theory of Relativity made some profound predictions and he was busy attempting to formulate his Unified Field Theory...the Holy Grail of Physics. My family lived in married student housing as dad studied to become a lawyer. One summer, Einstien came to visit his campus but the lecture hall was too hot (not many places had AC back then). He took the small group of students into an on-campus park where he lectured in the shade. My mom was working and dad got permission to bring me to the lecture with the understanding that if "the child" became disruptive, he and his child would have to leave. As they walked to the park, Einstein spoke with my dad and when they sat down he motioned for my dad to hand me to him. Dad said, I sat on Einstein's knee the whole time while he talked theory. Unfortunately, I have no personal memory of this and there were no cell phones with cameras back then.

    In 1967, my first calculus and physics classes banned calculators as cheating. I still have my original slide rule with all the logarythmic scales required for physics majors.

    The point of all this is simple. If a sci-fi tale is set in the immediate future, than I expect the "science" to be relatively (no pun intended) consistent with present day knowledge. But, when you look at the incredible strides in science and technology in just the last century, most anything is feasible over the next few centuries.

    For me, writing and reading sci-fi is not supposed to be like reading a technical manual...where is the "fun" in that? In my current sci-fi novel, I take liberties with current science because the story takes place far into the future. Instead, I invested heavily in character development and plot with lots of action to keep the reader moving. I even created three different, yet related, storylines that merge at various points in the story. The reader gets see the action from three different perspectives and cultures.

    The phrase "science fiction" means different things to different people.

    Just my $.02

    .....NaCl
     
  7. chad.sims2
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    chad.sims2 Contributing Member

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    I agree with you but i like writers who mention (Not nessisarily the details) the science that is involved, not in deapth or anything but a breif mention, like common knolidge of how it works. Not everyone would know exactly how an engine works but theyed be able to tell you that it's a machine that takes fuel, combusts it in a chamber that produces the power of the engine. That was a really bad example because i went ot indeapth but hopefully you know what i mean. Just becaue something is set in the feauture doesn;t mean a dragon can appear out of know where to fight your hero with out some logical reason for the dragon being there. Thats the difference between scifi and fantacy.
     
  8. NaCl
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    NaCl Contributing Member Contributor

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    I completely agree...hence, there are no dragons in my sci-fi tales. LOL!

    .....NaCl
     
  9. chad.sims2
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    chad.sims2 Contributing Member

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    Dragon riders of Pern was a SciFi book series, but then again the dragon's wern't quiet the mythical ones you see in Fantacy but where logicaly exsplained as natural creatures with a bit of genitic tempering later in the series.
    LOL But i get what you mean.
     
  10. Cogito
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    Cogito Former Mod, Retired Supporter Contributor

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    The only reason to explain tech at all in a story is so the readers can understand the rules that it follows, particularly as those rules affect the plot.
     
  11. InkDancer
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    InkDancer Senior Member

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    I always think it's funny in sci-fi how well everyone seems to understand the technology around them. In my experience, that's rarely the case... especially if the number of computers I've rebooted is any judge! With a sufficiently ignorant character, you could probably get away with all sorts of non-explanations. :)

    As for gravity, here's a theory to try on. According to string theory, the force of gravity may be weak because the majority of its force is acting in dimensions perpendicular to the 3 + 1 that we can directly observe. What if your gravity generator created a field which created a small torque in the direction of that dimension? You could then increase the gravity of a given object (say, the floor) without increasing its mass, just by pulling more gravitons from that dimension.

    (You can explain anything with string theory.)
     
  12. NaCl
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    NaCl Contributing Member Contributor

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    For that matter, what's to say a graviton generator has not been invented? To save energy, it senses the location of people wearing special sensory boots and the graviton field is ONLY generated in the critical sphere being occupied by that particular person. This type of "technology" could even be prime stuff for pranks and combat scenes...don't you just love applying fantasy to science?

    ....NaCl
     
  13. NaCl
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    NaCl Contributing Member Contributor

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    You nailed it! Excellent and simple explanation.

    .....NaCl
     
  14. InkDancer
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    InkDancer Senior Member

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    As a much bigger fan of fantasy than science, my answer is a resounding yes! :p
     
  15. LtTelra
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    LtTelra Member

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    Or you could just go like Star Trek and simply have artificial gravity.
    I always find it funny that all the systems cut out, yet the artificial gravity continues to work, especially in TOS. (The original series, for the layman)

    I'm not quite sure where I heard/read this, but one story used a 'black hole' of sorts contained in the ship, thereby creating gravity. I can't quite remember how they controlled and contained it.

    Hope it helps!
    Live Long and Prosper.
    Lt Telra
     
  16. Banzai
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    Banzai One-time Mod, but on the road to recovery Contributor

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    This is a good, if fairly succinct, summary of theories of artificial gravity.
     
  17. architectus
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    architectus Banned

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    Create a small black hole in space, then In encase it a durable material. It would be real gravity, because the black hole is very dense. If the black hole was small enough it would not destroy the crystal shape structure it is encased in. That structure would be placed in the bottom of the ship. These crystal-shape structures would have to be kept in space. The craft would first leave earth, then in space the crystal-shape structure would attach to the bottom of the craft.

    Before the craft entered another planet's atmosphere the crystal-shape structure, containing the mini-blackhole, would be disconnected and orbit the planet.

    I say crystal-shape, because some sort of angled form would be stronger against the pulling force of the mini-blackhole. I could ask Richard Muller at UC Berkeley what would be the best way to go about this.

    Either way it makes good sci-fi.
     
  18. Cogito
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    Cogito Former Mod, Retired Supporter Contributor

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    First off, small black holes are not stable. They evaporate. Explosively. But lets ignore that for a moment and pretend that they could be stable.

    Second, a crystal shape would not be the strongest. A sphere would be. Any imperfection in the spherical shape would probably be disastrous.

    Third, you have to deal with the inverse square law, so you would need to place your gravitational point source far enough "below" the deck so that a difference of, say, six feet doesn't result in a coouple gees of gravitational gradient (tidal force).

    Fourth, how do you accelerate or decelerate? If you move the container, the hole will stay put, making a nice pinhole in the container and anything else that the hole passes through.

    Fifth, even if you do manaage a way to keep the hole centyered in the container during acceleration (changes in speed and/or direction), you are still talking about lugging around many kilotons of mass. Your ship will be sluggish in its movements to say the LEAST. Basically. it's no different from lugging around your own private moon, but in a smaller package. A particularly large asteroid's mass MIGHT be enough, if you could tolerate the tidal gradient.
     
  19. architectus
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    architectus Banned

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    Right the ship would be massive, nothing something like zeropoint energy or the like wouldn't solve. Considering it is fiction.

    A sphere might be stronger than what I am thinking. If so then the very material the sphere is made out of should be artifical molecules, such as nanotubes, but not nanotubes of course,

    The size of a mini-blackhole I am refering to would be stable. I am unsure what is the smallest singularity that could be stable is though. I would have to ask Richard Muller.

    I thought about if it would stay in place or if once the ship moved the blackhole would go through the object, but I am not sure if that is correct. I would have to differ to Richard Muller once again. If so then some sort of EM field, or EM gravity fieldm, could be used to hold it in place to prevent that.

    But it is not like a blackhole is a ghost, it is a dense thing, so I am unsure why it would fly out of an object.
     
  20. Cogito
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    Cogito Former Mod, Retired Supporter Contributor

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    Put a ball bearing in a shoebox, and push the shoebox. The force you are applying is to the shoebox, so the shoebox begins to accelerate. The ball bearing tries to stay where it is, so it rolls back toward the side of the shoebox you push. The shoebox must apply a force to the ball bearing in order to make the ball bearing accelerate as well, (friction, or the collision with the back of the box). The box must exert a force large enough to accelerate the mass of the ball bearing, and when this is the case the force requirec to push the box will be the force to move the combined mass of box_ball bearing.

    With a black hole, any material it comes in contact with becomes part of it. No form of matter, or even an energy field, will remain intact. Whatever force you use to hold the hole in place within the container maust take that into account, or you will only move the container, and the hole will stay put.

    Forget about stronger materials. No material will be strong enough, including solid neutronium.

    With the kind of energy you are talking about to move such a ship, forget about using a ship. Motorize a planet. It's safer.

    Oh, and there's really no such thing as a stable black hole. Eventually they run out of stuff to feed on, and they begin the evaporation process. The smaller the hole gets, the faster it radiates, until it reaches a critical mass and explodes in a burst of gamma radiation. A black hole has a characteristic temperature that is related to the rate of radiation (and also determines the spectral distribution). Very large black holes are close to, but not at, absolute zero. As they evaporate, the temperature rises until the critical point is reached.

    Instead of trying to rationalize a super-advanced energy source pushing planetary masses around just to have a "down" in your decks, postulate an artificial gravity generator, and don't even bother trying to explain how it works.
     
  21. architectus
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    architectus Banned

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    You mean through Hawking Radation right?

    I wasn't aware that if a black hole touches let's say the inside of the metal sphere it is contained in, that it would pop strait through like a ghost. How does such a dense object do that? Does it eat a hole in it?

    I am sure there is a way to work this out so it works in the context of a sci-fi story. Such a blackhole should be usable for a while. Perhaps they feed it to keep it stable. Or let it run down and get a new one, sort of like a battery. I like the feeding idea, that could add an interest level to a novel.

    It would be someone job to feed the blackhole. That could make for some interesting patter.
     
  22. chad.sims2
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    chad.sims2 Contributing Member

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    The easist way is to say that we are wrong with what we thought and this is how things really work. :) Scientists are proven wrong daily.
     
  23. Cogito
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    Cogito Former Mod, Retired Supporter Contributor

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    You could as easily say that objects spontaneously move aor change directions when there is no applied force.

    To wave away well-established scientific fact just because it is inconvenient makes the writer look like a fool.

    Get the facts straight, with the best knowledge available. That's called research.

    You claim that scientists are proven wrong daily. And how often are non-scientists proven wrong? A hell of a lot more frequently.

    Best cover up, your bias is showing. :)
     
  24. NaCl
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    NaCl Contributing Member Contributor

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    Sci-fi writers constantly walk a path along the top edge of a narrow ridge. Lean too far in either direction and you fall off . . . i.e. your story sucks. A certain amount of reasonable fantasy can make a science-based story line fun, but too much and the story becomes absurd from a scientific standpoint. By the same token, a sci-fi story written for MIT level scientists would bore the average reader to tears.

    That said, it bothers me that sci-fi sections in most bookstores display lots of books full of demons, magic-based worlds and fantastic imaginary creatures with no regard for the environment in which they evolved. To me, those are NOT sci-fi books, yet bookstores regard fantasy and sci-fi as related topics, often lumping them together.

    As Cog has pointed out (over and over and over to his credit), real sci-fi must either 1) conform to conventional scientific theory, 2) offer a plausible evolution of present science, or 3) ignore the issue and just assume the result (for example: artificial gravity, trans-galactic travel without time dilation, "warp" speeds as a multiple of the speed of light, etc.) The key to ignoring present scientific knowledge is the setting in which the story takes place. If your sci-fi story is in the relatively near future, it can't deviate much from present science or you must create a convincing explanation for some evolution of present knowledge. If your story is set far in the future, you have much more flexibility with the supporting "science" and you can concentrate more on character and plot development as the story unfolds. The same possibility exists if your story involves alternative universe where your laws of physics may vary . . . but, if your writing moves this far into a made-up world, then is the story still "sci-fi" or has it become "fantasy" genre? Bottom line is Cog is giving you a valuable lesson in potential reader reaction to your fantasy-science. Instead of challenging his warnings, you would be better served to heed the advice and do more research.
     
  25. NaCl
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    NaCl Contributing Member Contributor

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    Here is an actual scientific fact that you could borrow from to "sell" your idea. It's a little long but makes the point.

    Do you understand the role of critical mass in a fission bomb?

    Two sub-critical masses of fissile material (U-235 or Pu-239) are brought together to reach a "critical mass" and, voila, a big bang results. Well, it's not quite that simple. If it was, every petty dictator or terrorist group in the world would have a supply of nukes.

    When you attempt to bring together the two (or more) sub-critical masses of weapon grade fissile material, the neutron flux between the approaching radioactive surfaces actually reaches an explosive level long before the total critical mass is reached. In essence, the homemade "atomic bomb" blows itself apart in a small local explosion instead of reaching simultaneous critical mass throughout the total fissile material. Such an explosion simply spreads a bunch of radioactive crap all over the ground about the size of a football field . . . no mushroom cloud, no firestorms, no mass casualties.

    The key to reaching full "critical mass" is to bring the sub-critical masses together quickly enough (measured in nanoseconds) so that the bomb does not destroy itself before all the fissile material becomes involved in the chain reaction. Early in the development of atomic bomb technology, scientists wondered if such a chain reaction could be controlled. Some speculated that once the chain reaction was initiated, nothing could stop it from completing. Then they discovered "delayed neutrons"! It turns out that not every atom in the chain reaction releases it neutrons at the instant of fission. Some neutrons are delayed for a tiny fraction of a second. This is the phenomenon that allows us to "control" a fission reaction inside a nuclear reactor core. Using special materials like boron that absorb neutrons, the flux can be regulated so that heat (energy) can be drawn form the system without it going into an uncontrolled chain reaction. So a nuclear power plant operates in the thin zone between nothing happening and a big bang. If things get a little too "hot", there are reactor poisons (neutron absorbers) that can be dumped in between the fissile pellets to shut down the chain reaction. In a worst case situation, called a China syndrome meltdown (like at Three Mile), the area beneath the reactor core is designed so the molten fissile material will spread out preventing an explosion and starting the cooling phase.

    Now, let's apply such history to your premise to see if we can imagine a mechanism to "control" tiny black holes.

    As the theory presently stands, tiny black holes will actually "evaporate" explosively as they lose containment of their energy. This would happen almost instantaneously after they were formed. So, in your story, you would have to offer a plausible mechanism to form and sustain these sub-microscopic black holes. Then, you have to regulate their gravitational pull . . . remember, for them to exert a gravitational "pull" on the passengers in the spacecraft, they would have to contain a total mass close to that of the Earth. The problem is that all this gravitational "pull" would come from a point source, instead of a large massive object where the "pull" would be equal across the entire spaceship. A point source, would require the ship to be a sphere so that every place in the ship had an equal gravitational field. No other shape would work.

    Now, let's say you used a spherical ship. How many concentric spheres would be possible inside the outer hull? Remember, the pull of gravity will diminish as you get further from the center of mass so it will change at each level. And, there are a bunch more issues you need to address.
     

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