 October 31, 2007 - 4:28pm | Why argue about the sand on the rock. It is a minor detail when you have many rocks. Sand on the rock...sand on the rock... ...nope, not gettin' it.By the way, welcome to the conversations, Gilbert. Glad to have someone else in the fray. |
 November 1, 2007 - 7:06am | Yeah, I was thinking about that. My only goal was to find an option to take the place of spinning space stations (as it has been shown how fast a station would have to actually spin to produce the effects). I'll leave out the tech talk and just stick to the base premise and the resultant tech. Corjay, how fast does the station have to rotate? I've spent a lot of time reviewing some of the "hard science" GURPS books and the stats from those don't seem too daunting. Merely curious. |
November 1, 2007 - 9:51am | Yeah, I was thinking about that. My only goal was to find an option to take the place of spinning space stations (as it has been shown how fast a station would have to actually spin to produce the effects). I'll leave out the tech talk and just stick to the base premise and the resultant tech. Corjay, how fast does the station have to rotate? I've spent a lot of time reviewing some of the "hard science" GURPS books and the stats from those don't seem too daunting. Merely curious. Also, the consideration that you're not actually producing gravity (not yet), but just weak kinetic forces that you have to control by slanted floors and the like. Walking on the outside or inside walls as depicted in the movies wouldn't actually be what happens. To get around anywhere, you would have to actually climb or decend, not walk. |
 November 1, 2007 - 5:03pm | In my SF games, I've explained hover vehicles and other "anti-grav" technology as highly advanced mag-lev tech. Advanced and fine tuned to the point where the vehicle is able to position and stabilize itself relative to the magnetic field of the planet it's on.
In space, where magnetic fields are too weak to align to, vehicles can be fitted with special gear that allows them to perform a limited, controlled, rotating magnetic repulsion/attraction to metallic bodies, such as the hulls of spacecraft, or the floors/walls/ceilings of spacecraft large enough to allow vehicle operation inside them. This lets the vehicle "hover" at a chosen distance from the metallic body, limited to 3 or 4 meters altitude, beyond that the equipment isn't strong enough to maintain stability.
Mag-lev hover equipment is expensive, and requires a tech expert to calibrate the settings on a new world, explaining why many groups still use tracked and wheeled vehicles when exploring new worlds. ~ Rich berentiu@gmail.com |
November 2, 2007 - 6:34am | Also, when you move perpendicular to the direction of rotation, you'd probably be falling forwards and have to walk/move backward and to the side or something. And I am pretty sure I read that you couldn't merely walk against the spin (more like controlled falling). Not to mention how bloody uncomfortable the whole sensation would be. Some research on the subject (available online) doesn't paint a great picture. However if "gravity" could be produced even in a fraction of Earth norm, it would provide the health and comfort effects (isn't .3G the threshhold? I seem to remember that from somewhere). And placing it along the outer rim of a spinning donut spacestation would provide the most living area. No reason to make it spin and, in fact, that would be counter productive. I have a few thoughts on the subject I'll try to piece together for future reading... . Looking forward to your work with great interest. |
November 8, 2007 - 9:40am | Another thought on gravity, if gravitation generation would be feasable, is that if the power requirements are great or the technology required for generation is sizeable/complicated/etc..., it is likely that starships would still be set up with decks laid out as they currently are suggested. Otherwise, gravity generation would have to counter the effects of acceleration as well as provide deck orientation. |
November 8, 2007 - 10:11am | Another thought on gravity, if gravitation generation would be feasable, is that if the power requirements are great or the technology required for generation is sizeable/complicated/etc..., it is likely that starships would still be set up with decks laid out as they currently are suggested. Otherwise, gravity generation would have to counter the effects of acceleration as well as provide deck orientation. |
November 8, 2007 - 10:09am | Also, when you move perpendicular to the direction of rotation, you'd probably be falling forwards and have to walk/move backward and to the side or something. And I am pretty sure I read that you couldn't merely walk against the spin (more like controlled falling). Not to mention how bloody uncomfortable the whole sensation would be. Some research on the subject (available online) doesn't paint a great picture. I think you'll find it very much in line with your thoughts. I think you'll enjoy the article.However if "gravity" could be produced even in a fraction of Earth norm, it would provide the health and comfort effects (isn't .3G the threshhold? I seem to remember that from somewhere). And placing it along the outer rim of a spinning donut spacestation would provide the most living area. No reason to make it spin and, in fact, that would be counter productive. I have a few thoughts on the subject I'll try to piece together for future reading... . Looking forward to your work with great interest. |
 November 9, 2007 - 2:23pm | A related field of research in sci-fi would be "mass reduction" technology. I'm just making this up completely, but imagine a field that reduced the mass of ordinary objects (along with their inertia) without changing their physical size, density or other properties. ...and bullets entering the field wouldn't hit as hard. Their speed would be the same, but kinetic energy would be reduced. |
 November 11, 2007 - 4:16pm | As far as rotational gravity is concerned, here is a spiffy graph I whipped up that might help illustrate the kind of sizes we are talking about: The direct link is http://i25.photobucket.com/albums/c59/geejaydee/Star%20Frontiers/graph.jpg At 1 and 2 RPM there are no noticable coriolis effects or nausea from the rotation. Since everything inside the torus, or drum, including the air, will be moving, the air resustance will naturally carry objects not in contact with the floor along, and even if the object did remain in place to the rotating observer it would seem to arc towards the floor. You will need some kind of periodic input to spin-up the torus to keep it rotating, and they are best deployed in contra-rotating pairs to avoid any wobble. G. |
November 11, 2007 - 6:11pm | I haven't checked the math myself, but this site has a good artificial-gravity calculator that can be used to work out the specs of rotating space stations. http://www.artificial-gravity.com/sw/SpinCalc/SpinCalc.htm It includes the comfort/nausea consideration. |
November 11, 2007 - 6:19pm | The math isn't complicated, the graph above was produced in excel in about 15 minutes, and the biggest problem I had was geting the labels in the right place  What it does show is that it's pretty much out of the question for all but the largest ships to have anything approaching "normal" gravity using rotating spin sections. Even at .5 g at 3rpm, on the borderline of tolerable, you need a 100 meter diameter torus. But, a 500 meter diameter station, at 2rpm works quite nicely. G. |
November 11, 2007 - 6:34pm | That calculator doesn't involve mass. It's my understanding that mass is a large part of calculating gravity. |
November 11, 2007 - 6:46pm | The spin-calc is only for "artificial-gravity" caused by rotation. It's not intended to be used for gravity calculations involving mass. |
November 11, 2007 - 7:21pm | That calculator doesn't involve mass. It's my understanding that mass is a large part of calculating gravity. Indeed. This is actually calculating the centripetal acceleration of a rotating object, not actual gravity. To calculate the gravitational attraction between two objects we can use Newton's handy Universal Gravitation Equation: F = GMm/R^2 where G is the universal gravitational constant; G = 6.67*10-11 N-m²/kg². M and m are the masses of the two objects, in kg
Now, begause G is so teeny tiny – 0.0000000000667 – you can see that you need A LOT of mass to generate a decent sized gravitational force. You can convert the force, F, produced above into g’s by using the equation a =F/m (adapted from the handy F=ma)
F is the force of gravitational attraction m is the mass of the object a is the acceleration due to gravity This will give us a figure for the acceleration due to gravity, a. Divide that by 9.8ms^-1 to give you your figure in g’s. Or, on the other hand, you could do something MUCH more interesting. In my opinion, for Star Frontiers you only need four settings for gravity - High - difficult to move around and very tiring, normal - well, normal..., low - everybody bounces around a lot and you can jump further, but risk smashing your brains out on landing and zero-g - everybody check for space sickness and unlimber those rcoiless gyrojets! G. |
November 12, 2007 - 11:26pm | Oh yeah. I was thinking actual gravity. I was forgetting that the force applied produces a simulation of the effect of gravity. Now the calculator makes sense to me. |
 November 13, 2007 - 12:13am | IMO, one of the appeals of Star Frontiers is the lack of explicit Anti-Gravity; makes it different from a lot of the main-stream Science Fiction. Of course, there is the implicit anti-grav or 'innertial re-directors' or whatever, such as the MR in Knight Hawks (which has it's plus' & minus', not wanting to start a debate on vectored movement in space...) Looking forward to the article. |
November 13, 2007 - 12:50am | F = GMm/R^2 Why do I suddenly feel like I have a Brainleech from Glignarg 5 on my head? where G is the universal gravitational constant; G = 6.67*10-11 N-m²/kg². M and m are the masses of the two objects, in kg
Now, begause G is so teeny tiny – 0.0000000000667 – you can see that you need A LOT of mass to generate a decent sized gravitational force. You can convert the force, F, produced above into g’s by using the equation a =F/m (adapted from the handy F=ma)
F is the force of gravitational attraction m is the mass of the object a is the acceleration due to gravity This will give us a figure for the acceleration due to gravity, a. Divide that by 9.8ms^-1 to give you your figure in g’s. Or, on the other hand, you could do something MUCH more interesting. In my opinion, for Star Frontiers you only need four settings for gravity - High - difficult to move around and very tiring, normal - well, normal..., low - everybody bounces around a lot and you can jump further, but risk smashing your brains out on landing and zero-g - everybody check for space sickness and unlimber those rcoiless gyrojets! G.  Where are the Giant Brains when you need them?
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 November 18, 2007 - 5:33am | Are you sure that's not a jet engine on that horse...add a few thrust nozzles, and that sucker just could just as easily be an aerodyne vehicle as anti-grav. Could thrusters keep this thing a-float? Serious, is that possible? My first comment here. The thing is the Harrier jet can only hover for a minute before it's engine starts to over heat. For true hover capabilities you'd need to have a dedicated hover engine like the new JSF Joint Strike Fighter the F-34, I think they've designated it the F-34? The Harrier can only divert it's thrust while the engine still runs with the axis of the fighter. A gimbal mounted engine is what you seek design wise like the Osprey. In every age, in every place, the deeds of men remain the same. |
November 18, 2007 - 12:48pm | Are you sure that's not a jet engine on that horse...add a few thrust nozzles, and that sucker just could just as easily be an aerodyne vehicle as anti-grav. Could thrusters keep this thing a-float?Serious, is that possible? The thing is the Harrier jet can only hover for a minute before it's engine starts to over heat. For true hover capabilities you'd need to have a dedicated hover engine like the new JSF Joint Strike Fighter the F-34, I think they've designated it the F-34? The Harrier can only divert it's thrust while the engine still runs with the axis of the fighter. A gimbal mounted engine is what you seek design wise like the Osprey. |
 December 2, 2007 - 12:25am | Another thing to contemplate: In order to prevent bones from calcium loss, you need sufficient levels of "true gravity" to maintain a healthy body. True gravity is just that: graviton radiation. Spin-induced inertia is *NOT* true gravity. G's generated by acceleration is not true gravity either. NASA is trying to plan a manned mossion to Mars. This unfortunate fact is becoming a real problem, as astronauts might not be healthy enough to land on the planet by the time the spacecraft gets to its destination. Spinning the hull will not solve the problem, nor would constant acceleration (assuming the craft could carry enough reaction mass for this. Chemical propulsion will not cut it.). This is something to consider, especially for the ones who want a more "realistic" environment. A possible solution is mentioned in another RPG called "2320ad". It is an update to GDW's "2300ad" RPG. I was a playtester for 2320. There are a few interesting concepts. One of which is a DNAM (DNA modification, 2320's word for genetic engineering) that intorduced an extra organ in a human body. The organ is a permanent addition. Its purpose is to, when it's active, to house a special calcium-providing bacteria that floods the human body with what is depleted during low-gravity situations. When reaching a planet's surface, the organ is rendered dormant and the bacteria is killed off to prevent overdosing on calcium (arthritis and liver failure anyone?). Something to consider. Grendel T. Troll Registered Linux User #299419 "Nobody remembers what you say. A few might remember what you do, but EVERYONE remembers how you make them feel." ~ Anonymous |
December 2, 2007 - 4:13pm | Actually that's incorrect on a couple of points. Firstly, there is no such thing as gravitational radiation. Gravity is the curvature of space-time by the presence of a body with mass. It is produced by and affects all other objects with mass. There is a search on for the mysterious graviton quark, but quarks are not radiation. It binds us and holds the universe together - me, you, the rock, the ship.... no, with, that's the force. Secondly, calcium loss due to weightlessness is purely as a result of the body no longer needing to apply load bearing calcium into the bone matrix. Normaly our bones are undergoing a constant cycle of regrowth and clacium is laid down in load bearing structures in our body in the direction of peak mechanical stresses. When that stress is removed the calcium stops being laid down. This can lead to dangeroulsy elevated levels of calcium within the blood. However, because this bone growth is related to skeletal stress, it can be alleviated using regular exercise (as can the muscle wastage associated with weightlesness) or mechanically produced artificial gravity. G. |
December 2, 2007 - 4:25pm | Yeah, I believe regular exercise is how the space station attendants for the one in orbit right now (I forgot the name) fight the calcium problems as well as leg muscle atrophy. |
December 3, 2007 - 1:17pm | Weightlesness presents other problems as well, we evolved on a planet with a constant 1g downward attraction, so our bodies are designed to work in that environment. Many astronauts have experienced space adaptation sundrome, also known as space sickness or SAS, which brings on nausea, vertigo dizziness and sudden and unexpected perceptual flips (you suddenly feel like you are upside-down) before the body adapts. This is measured on something called the Rath scale, I think, named after one of the first astronauts to experience it. So far it hasn't lasted more than 72 hours in any single case, but it can be very, very debilitating. You also experience a fluid redistribution, meaning that the face and neck swell up as fluid relocates to those tissues. The sinuses often clog up leading to a constant stuffy nose or cold-like symptoms. This fluid redistribution is also the reason that many astronauts can't stand upon return to earth - the blood supply to their leg muscles has yet to return to normal. The internal organs shift and re-distribute themselves slightly, leading to enlargment of the liver and heart. The digestive tract can be....disturbed... leading to... ahem.... excessive flatulence. Muscle fibres which are normaly used for brute strength work - walking, lifting, supporting the body, start to change fo muscle fibers designed for fast reactions (or fast twitch as they are known), which makes the astronaut more dexterous and nimble, but weaker. G. |
December 6, 2007 - 2:09pm | I've been thinking about the donut shaped space stations and their spin-induced faux gravity. Up to now we've been thinking of the station's spin creating centripital force to create simulated gravity along the rim - creating a sensation of gravity "pushing" away from the center. However, due to the coriollis (sp) effects, wouldn't it be wiser to create donut-shaped space statons with floors/levels shaped like wedges/pie pieces, where the "down" direction would be the opposite of the spin? Would the station have to spin much faster? |
December 7, 2007 - 10:27am | No, the problem is that as soon as you add a rotational component, you skew the vector away from the axis of rotation. It's this that creates the centripetal force.you can't use the direction of spin to create a force, since the rotational moment will always be greater than the moment in the spin direction. You need to reduce the angular moment below that of the rotational moment, but the only way to do that is to extend the radius, reducing the rotational moment, but then you have to reduce the angular velocity to compensate for the extended radius..... |
