THESE FORUMS NOW CLOSED (read only)
Comic Discussion => QUESTIONABLE CONTENT => Topic started by: Is it cold in here? on 19 Jan 2012, 13:21
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Hannelore's Formspring experiment said that the station spins to create a 1g acceleration.
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That would also be much simpler than hauling people up to his space station or coming down to earth (something I'd say he could no longer do if Hanners didn't seem to be free of physical maladies from growing up in low-g).
Rotational pseudo-gravity of course (IICIH got in ahead of me!). Which in turn implies that Hannerdad's orbital is quite large, to avoid the problems (http://www.spacefuture.com/archive/artificial_gravity_and_the_architecture_of_orbital_habitats.shtml) of nausea induced by gyroscopic coupling etc. Since this is a comic, let's say <calculator noises> his station has a radius of 1000m so that it can provide a 1g centripetal acceleration while turning at just under the one revolution per minute that is supposed to be safe even for motion-sickness susceptible people (Yes, I am a space-nerd). Hilarity ensues when <character> turns out to be extra-susceptible.
The other question is, who is the "they" that Hannerdad is permitting to hold a birthday party? The station's human crew? The un-secret robots?
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I wouldn't like to have to design a structure 1km in radius to rotate at 1rpm. All the stresses are in tension, not compression, which gives me bad feelings on that scale. But since I've done no mechanics since my engineering degree in 1968, my feelings might not be justified, I suppose.
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Suspension bridges are largely in tension.
The easy way to create 1g worth of spin is a long tether and a counterweight.
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Now try docking your transport on it, and then realise you've thrown it way off balance.
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Well what if we made it more like a giant Frisbee and have the docking station on the logical top or bottom of the station? that way any added weight isn't throwing off the spin by adding unnecessary weight to a side that is making a large rotation?
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Now try docking your transport on it, and then realise you've thrown it way off balance.
That's why you have a de-spun central docking hub. Saves your space station from the wrath of Sir Issac Newton and allows for physical comedy when entertaining guests.
Well, if you want to get to space, you generally have to get to either Florida (Kennedy SC), New Mexico (NM Space Facility) or California (Edwards AFB).
Unless, of course, Hannerdad has a space elevator located somewhere nearby.
I'm thinking more space plane. Hannerdad's station is in LEO given how frequent Hanners said the sunrises were, elevators don't work so well that low. I'm thinking something Skylon-esque (http://en.wikipedia.org/wiki/Skylon_%28spacecraft%29) or NASP-esque (http://en.wikipedia.org/wiki/Rockwell_X-30).
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I'm thinking more space plane. Hannerdad's station is in LEO given how frequent Hanners said the sunrises were, elevators don't work so well that low. I'm thinking something Skylon-esque (http://en.wikipedia.org/wiki/Skylon_%28spacecraft%29) or NASP-esque (http://en.wikipedia.org/wiki/Rockwell_X-30).
Considering that there was a change in universes at some point in recent history, a combination of the X-30/33 and SpaceShip One/Two from Virgin Galactic.
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Which in turn implies that Hannerdad's orbital is quite large, to avoid the problems (http://www.spacefuture.com/archive/artificial_gravity_and_the_architecture_of_orbital_habitats.shtml) of nausea induced by gyroscopic coupling etc. Since this is a comic, let's say <calculator noises> his station has a radius of 1000m so that it can provide a 1g centripetal acceleration while turning at just under the one revolution per minute that is supposed to be safe even for motion-sickness susceptible people.
Thanks for the links (also the last time this topic came up) explaining Coriolis-induced problems of rotational gravity. But in a way the fact that you resorted to a frigging calculator to (effectively) estimate Pi over 30 (radians per second) squared up to the whopping accuracy of a single significant digit makes me sad. :cry: I know, that's the way it's done nowadays. This is not meant as a personal criticism, please don't take it as such. Just my old school thinking, where mental arithmetic is the default.
@Torlek: Thank you so much for reminding everybody that a space elevator would be mostly useless for getting to a low orbit station! I guess you could ride a space elevator up a significant fraction of the distance to geosynchronous orbit and drop off
to end up on a suitable elliptical orbit approaching the space station at perigeum, but the velocities would not match, so you would still need a lot of thrust to be able to dock into the space station. May be the resident experts of space travel can help me here :-)
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How many sliderules have you got? I can still lay my hands on three.
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I think that the one slide rule I used in middle school is still somewhere. Can't say that I would have used it for a looong time. :cry:
More often than not I only need exact results (or estimates based on long simulations) at work. I admit that Mathematica (or long computer simulations) will be the tool, if I need more than two significant digits of an approximate figure. Currently I do not own a calculator at all. I did 'save' a book full of logarithm tables, when our library decided to get rid of some of their old stuff. Mostly for sentimental reasons.
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Slide rule. Good thing I didn't take geometry and trigonometry until the 1980's, or I woulda had to learn how to use one of those.
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(This seemed like enough of a digression to merit its own thread. I've taken the liberty of quoting a couple of messages that were sent by PM rather than go too off-topic in the WCDT.)
I wouldn't like to have to design a structure 1km in radius to rotate at 1rpm. All the stresses are in tension, not compression, which gives me bad feelings on that scale. But since I've done no mechanics since my engineering degree in 1968, my feelings might not be justified, I suppose.
Your engineering background is certainly stronger than mine. The 1975 "Stamford torus (http://ttp://en.wikipedia.org/wiki/Stanford_torus)" study proposed a radius of 900m, but I am not qualified to assess the structural design. The classic space station is always imagined as a complete wheel, but I've often imagined a single spoke with a docking-hub free-fall area in the centre of the rotating structure, and habitable areas at the ends. It would certainly be a structure in tension with elevators/cable-cars linking the hub to the habitats at the ends. Docking anywhere other than the hub of a 1000m radius rotating space-station would present serious difficulties, since the "circumference" would be whirling round at roughly 100m/s.
As for the radius, the curve of radius vs. rotation for any given centripetal acceleration (http://i1094.photobucket.com/albums/i446/ZAL77449/hab-rot01.jpg) gets pretty flat once the radius exceeds 250m or so. If one reduces the radius from 1000m to 500m, for example, the rotation required for 1g only rises from 0.95RPM to 1.34RPM, which most studies have suggested is easily tolerated. Supposedly 3RPM (100m radius) is bearable with acclimatisation, but 5RPM (35m radius) has everyone reaching for the sick-bags. Yes, I did already have a spreadsheet set up to work all these things out...
Off-center docking: A vehicle trying to dock couldn't afford to spend any amount of time staying near the docking port, since the vehicle would have to accelerate constantly. Relax the requirement for allowing multiple docking attempts, though, and the approaching vehicle could fly a free-fall course that intersected the path of the spinning element at zero relative velocity (I think the usual metaphor is "catching an egg on a plate"). With slow rotation, the station and the approaching vehicle might even stay in proximity long enough to allow human control.
There's a hidden economic assumption in the model of a complete wheel, which is that the valuable real estate that you want the most of will be in the 1g area. Microgravity industry might be a more important tenant.
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In the absence of my long-lost mathematical capability and knowledge of materials science, I resort to weak analogies.
Using cables to link the station and its counterweight to a central hub (and maybe the counterweight would be more useful accommodation, for efficiency) is equivalent to having cables that could lift the structure concerned off the surface of the Earth from a height of a kilometre. In comparison, the tallest suspension bridge in the world has towers less than 300m high, and the bridge deck is not at their base, of course. OTOH, the main cables are at an angle, so the tension in them will be greater. Thus, if the deck is 250m below the tops of the towers, and the angle of the cables at the tower attachment is such that the tension is double what it would be if straight down, then a 500m radius for the space station would be doable using similar technology; maybe a bit more given that there doesn't have to be the same margin for the effects of weather and traffic.
So, I was being a bit pessimistic - it's on the edge, but probably possible.
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Sorry about being dense, but I'm still recovering from a flu, and this makes my head spin. How do you dock into the hub of a rotating space station, if you can't make the incoming spacecraft rotate at the same rate? At the hub you have control of the relative speed, but the rotation is still there.
Dock into a huge ball-bearing, and fine-tune the rotations before opening an airlock?
I realize that the docking spacecraft would be small, so 1RPM won't take much. May be this isn't a problem at all?
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The counterweight module could carry all the heavy stuff like fuel, water, batteries and food. The habitation module could be relatively light weight, and doesn't need to be at 1g. In fact, if the station is being used as a way station between the Earth and the Moon, as in 2001, a lower gravity such as 1/3-1/2g may be more beneficial, as a transition for people who are adjusting between 1g and 1/6g.
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How do you dock into the hub of a rotating space station, if you can't make the incoming spacecraft rotate at the same rate? At the hub you have control of the relative speed, but the rotation is still there.
I had thought about that; it seems to me that approaching along the axis and matching the rotations is trivial compared with having to accelerate continuously to keep in position during docking off-centre. I don't want to contemplate the other alternative of a stationary hub with the space station rotating around it!
a lower gravity such as 1/3-1/2g may be more beneficial, as a transition for people who are adjusting between 1g and 1/6g.
But if they are not, and are only going between the station and the Earth, then what is the minimum gravity to avoid skeletal and muscular problems in the long term?
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Paul, I can't do the mechanics right now. If coerced to do it I think I would be able to work out the tension on a catenary, i.e. a cable hanging from its end points at the top of the pylons with zero load, but the figures coming out would be meaningless for our present question, so I won't. Anyway, the angle makes a huge difference. May be the reason they want tall pylons is to increase the angle?
As an extremal case of a tiny angle consider the tension on the cable of a tight rope dancer. I may be way off, but I think it could easily be ten times the weight of the artist or more. IIRC in the story about the French guy who danced between the WTC towers they said that the tension on the cable was something like 5 ton(ne)s (sorry I don't know whether those were metric or not).
So the existing materials could be strong enough to take the tension of a spinning space station. If the spinning station has a full rim connected to the hub by several spokes, may be building a 'suspension bridge' from each and every spoke to the next one would give enough extra structural support?
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But if they are not, and are only going between the station and the Earth, then what is the minimum gravity to avoid skeletal and muscular problems in the long term?
That's not really known. The only gravities humans have spent more than a few days at have been 1g and 0g.
We are adapted to 1g (obviously) and there have been Astronauts and Cocmonauts spending many months at a time at 0g since the 1970's, but the longest anyone has spent at an intermediate level was when Cernan and Schmidtt spent just over 3 days on the Moon.
Given that physically fit individuals can spend extended periods at 0g with little ill effect, artificial gravity on a spacecraft may be more of a luxury than a necessity (It does make filming Sci-fi movies simpler).
The real limit to long term space habitation is radiation exposure. Without the shielding properties of Earth's atmosphere, Astronauts in Low Earth Orbit receive much larger doses of some really scary photons.
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Paul, I can't do the mechanics right now. If coerced to do it I think I would be able to work out the tension on a catenary, i.e. a cable hanging from its end points at the top of the pylons with zero load, but the figures coming out would be meaningless for our present question, so I won't. Anyway, the angle makes a huge difference. May be the reason they want tall pylons is to increase the angle?
A suspension bridge is not a simple catenary, though, because the deck is suspended from multiple points along the cable. The angles at the end are typically of the order of 45 degrees, so you don't have the tight-rope levels of multiplier (I start to see more extreme tensions when suspending microphones on a taut cable across an auditorium).
The real limit to long term space habitation is radiation exposure. Without the shielding properties of Earth's atmosphere, Astronauts in Low Earth Orbit receive much larger doses of some really scary photons.
True - and the best form of shielding is (in effect) mass, and so impacts on the feasibility of our rotating designs.
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How many sliderules have you got? I can still lay my hands on three.
I have two good quality slide rules, and one cheapie plastic circular slide rule. I am looking for pictures.
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Aristo 0968 Studio
My 10" rule that I bought to be an engineer with (not my own - mine's cleaner than this photo):
(http://cassland.org/images/Aristo-0968-Studio.jpg)
Aristo 89 Rietz
A 5" pocket rule I picked up sometime (mine has a leather slipcase):
(http://cassland.org/images/Aristo-89-Rietz.jpg)
I can't identify my wife's without going home to look at it.
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My slide rule is a 10-inch (the length of the scale as opposed to the entire frame, I presume) Japanese make Royal Techlog. My middle school math teacher probably got commissions from whichever company was importing those. It has the same set of scales as your 10-incher. Seems to be in reasonable but not pristine condition. There are some scratches in the sliding window (sorry, don't know what it's called in English) - luckily none too close to the hairline. Also the spring from the other side of the window is missing, but the one on the other side keeps it in the correct position. IIRC we occasionally had to use graphite from pencils as a lubricant, but it seems to be sliding just fine, now.
My Dad has an Aristo, and that's what he used when teaching me :-)
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The sliding window is referred to as the cursor (the running part, from the Latin for run). More elaborate rules (like mine) have additional hairlines for special purposes.
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They look like the GFTs I learned to use when firing howitzers back in the 80s.
{looks around at all the real engineers} I'll go back to lurking in this thread now.
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If you can lay hands on a July 1976 National Geographic, Isaac Asimov took a science-fictional look at a mile-wide spinning-wheel space station. My copy is ... somewhere ... but here's a link (http://www.thespacereview.com/article/1376/1) to a recent commentary about it.
A wheel station would have the advantage over a module-and-counterweight structure in that you'd be able to move throughout the habitable-gravity area without having to move through the hub. I'd have to think the ring would be self-reinforcing to a degree.
For some entertaining nonsense, the original "Star Fleet Technical Manual" from the 1970s contains schematics for a giant spinning space station with, among other things, docking facilities *around the rim* for Enterprise and her fleetmates. Quite apart from the increased gravity, I'd hate to be the one who had to navigate a ship into one of those docks. Mr. Sulu'd be earning his pay, he would ...
ADDED LINK. Duh.
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With a central docking hub, you could put the approaching craft into a slow roll and match the station. Control inputs would have effects that would surprise an untrained human. Alternatively, you could despin the hub during docking maneuvers and spin it back up again for the convenience of people leaving the docking hub.
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I'm worried by the idea of a bearing of that size to allow that decoupling; the effect of a jam would be devastating.
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(http://i44.photobucket.com/albums/f50/Kugai2/Babylon%205%20Files/Babylon5Station.jpg)
Admittedly, anything like B5 is a long way off, but it does use a Rotational Section (Ie the cylindrical main body) to maintain gravity and has an inner central core which is used as a large garden to grow foodstuffs and to create a natural CO2/Oxygen exchanger. JMS, in many cases, tried to stick close to what was scientifically known and postulated about building such a station while giving it a futuristic bent.
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For some entertaining nonsense, the original "Star Fleet Technical Manual" from the 1970s contains schematics for a giant spinning space station with, among other things, docking facilities *around the rim* for Enterprise and her fleetmates. Quite apart from the increased gravity, I'd hate to be the one who had to navigate a ship into one of those docks. Mr. Sulu'd be earning his pay, he would ...
Take a closer look at those schematics. It doesn't say anywhere that it spins, and it should be obvious that it doesn't. The floors don't follow the curve of the rim, they're flat. With a spin-induced gravity, if you stood near the end of a pie-shaped segment, it'd feel like the floor is tilted at a 30 degree angle. It must generate artificial gravity using the same technology as the Enterprise.
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Here are My Slide Rules (http://www.celticgeek.com/images/SlideRules_01.jpg).
And the father of one of my friends in High School had a "double length" slide rule; a full twenty inches long!
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For some entertaining nonsense, the original "Star Fleet Technical Manual" from the 1970s contains schematics for a giant spinning space station with, among other things, docking facilities *around the rim* for Enterprise and her fleetmates. Quite apart from the increased gravity, I'd hate to be the one who had to navigate a ship into one of those docks. Mr. Sulu'd be earning his pay, he would ...
Take a closer look at those schematics. It doesn't say anywhere that it spins, and it should be obvious that it doesn't. The floors don't follow the curve of the rim, they're flat. With a spin-induced gravity, if you stood near the end of a pie-shaped segment, it'd feel like the floor is tilted at a 30 degree angle. It must generate artificial gravity using the same technology as the Enterprise.
Huh. I remember my copy (long gone) saying it spun. And remembering, even as a sixth-grader, that it made no sense.
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But in a way the fact that you resorted to a frigging calculator to (effectively) estimate Pi over 30 (radians per second) squared up to the whopping accuracy of a single significant digit makes me sad. :cry: I know, that's the way it's done nowadays. This is not meant as a personal criticism, please don't take it as such. Just my old school thinking, where mental arithmetic is the default.
Actually I didn't use a calculator (the noises were artistic license) :-P. I had a spreadsheet already set up to run the numbers for a range of radii and centripetal accelerations (http://i1094.photobucket.com/albums/i446/ZAL77449/hab-rot01.jpg) :lol:, but if I hadn't, I certainly would have used a calculator. I'm just not confident that I could calculate in my head the necessary radius for a space station given only that the rim would be travelling in uniform circular motion at one RPM, and the required centripetal acceleration at the rim was 1g (which I approximated as 9.81m/s). I take comfort from knowing enough physics and maths to do the calculation at all, and being curious enough to want to do it. I'm not nearly ancient enough to feel nostalgic about slide rules, but this was my first calculator (and the suànpán (http://en.wikipedia.org/wiki/Suanpan) can easily handle hex as well as decimal owing to the peculiarities of traditional Chinese weights and measures):
(http://www.chinavista.com/experience/abacus/suanpan.jpg)
I realize that the docking spacecraft would be small, so 1RPM won't take much. May be this isn't a problem at all?
I've always assumed that the incoming spacecraft would match its spin to that of the space-station. A 5m radius spacecraft (larger than anything in service today; Soyuz and Shénzhōu are both under 3m in diameter) rotating at one RPM would generate so little pseudo-gravity (about 0.06g) that its crew would probably not notice.
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I'd consider using a magnetic bearing to avoid vacuum welding problems.
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@Akima, a spreadsheet at hand is, of course, an acceptable excuse for not doing mental arithmetic. I just happened to be working with that single data point that you gave us first: omega=1RPM=Pi/30 rad/s is approximately (using the Hoosier approximation Pi=3) 0.1 rad/s, so to find a radius R giving the target acceleration of R*omega^2=1g=10m/s^2 we immediately see that R=1000 m. IOW for this particular set of inputs at this level of precision the "mental arithmetic" amounts to moving the decimal point around :-D
You're, of course, correct about the problem of matching spins being trivial. I knew that the crew wouldn't need to use barf bags, but for some reason it wasn't clear to me that matching spins is no more difficult than matching speeds. My lack of knowledge about steering in space showed.
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OK, suppose you've matched spins but need to correct a slight drift to the left. You instinctively fire the right thrusters.
Suddenly you're going in circles.
Humans are highly trainable, so it might be possible to teach them to do the right thing. Computers would be a better bet.
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Ok, "trivial" was an overstatement. Would "Something that a computer or a trained pilot can handle" be closer to the mark?
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First you would have to align the axes, then you would match rotation, then dock.
It might be tricky for a human pilot, but for a computer controlled pilot, it would be simple.
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Gundam.
http://www.youtube.com/watch?v=DO5-XGCqzfo
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For some entertaining nonsense, the original "Star Fleet Technical Manual" from the 1970s contains schematics for a giant spinning space station with, among other things, docking facilities *around the rim* for Enterprise and her fleetmates. Quite apart from the increased gravity, I'd hate to be the one who had to navigate a ship into one of those docks. Mr. Sulu'd be earning his pay, he would ...
Take a closer look at those schematics. It doesn't say anywhere that it spins, and it should be obvious that it doesn't. The floors don't follow the curve of the rim, they're flat. With a spin-induced gravity, if you stood near the end of a pie-shaped segment, it'd feel like the floor is tilted at a 30 degree angle. It must generate artificial gravity using the same technology as the Enterprise.
Huh. I remember my copy (long gone) saying it spun. And remembering, even as a sixth-grader, that it made no sense.
Take another look. The 'Buildings' of the station are set on the outer rim. Looking at it it seems to have the same constructional layout as Babylon 5 as to the relation of floors and decks layout. Admittedly, unlike B5, the Trek Universe has the benefit of Artificial Gravity, so it probably doesn't rely on rotational action gravity wise as that station does, so I'm guessing that the rotation is more of a slow 'Barbeque Roll' much like the Apollo spacecraft used during their journey to the moon.
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To be pedantic, it was the humans in the B5 universe who didn't have artificial gravity.
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I am aware of that, which is why ships of the Hyperion Class were zero G ships and their stations rotated or, like the Omega's, Earth Force One, Liners like the Azimov and the large Explorer Class ships had rotating sections. Human's didn't gain Gravtech until the Shadow War era with their co-operation with the Minbari during it.
And yes, yes you are.
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I have only begun to show my potential for pedantry.
Could you prevent bone loss with regular sessions in a small centrifuge, so you wouldn't have to spin the whole station? Or combine recreational EVA with bone therapy by putting spacesuited humans at opposite ends of a spinning tether for a few hours each?
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Exercise sufficient to maintain your musculature at 1g levels would probably do much of what's required. Possibly.
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For some entertaining nonsense, the original "Star Fleet Technical Manual" from the 1970s contains schematics for a giant spinning space station with, among other things, docking facilities *around the rim* for Enterprise and her fleetmates. Quite apart from the increased gravity, I'd hate to be the one who had to navigate a ship into one of those docks. Mr. Sulu'd be earning his pay, he would ...
Take a closer look at those schematics. It doesn't say anywhere that it spins, and it should be obvious that it doesn't. The floors don't follow the curve of the rim, they're flat. With a spin-induced gravity, if you stood near the end of a pie-shaped segment, it'd feel like the floor is tilted at a 30 degree angle. It must generate artificial gravity using the same technology as the Enterprise.
Huh. I remember my copy (long gone) saying it spun. And remembering, even as a sixth-grader, that it made no sense.
Take another look. The 'Buildings' of the station are set on the outer rim. Looking at it it seems to have the same constructional layout as Babylon 5 as to the relation of floors and decks layout. Admittedly, unlike B5, the Trek Universe has the benefit of Artificial Gravity, so it probably doesn't rely on rotational action gravity wise as that station does, so I'm guessing that the rotation is more of a slow 'Barbeque Roll' much like the Apollo spacecraft used during their journey to the moon.
Oh, I'm not prepared to go to war over a piece of Star Trek lore most folks would prefer hadn't happened (Roddenberry basically told Franz Joseph Schnaubelt to go to town and make s**t up because at the time, no one had figured out Star Trek would live on and on and on in multiple incarnations) ... I just remembered (because as a 10-year-old nerd I was familiar with the idea of rotational "gravity") looking at it and thinking, it's meant to spin for gravity but those floors make no sense; they'd effectively be like giant hills and I'd hate to try to dock with those docking pods on the rim.
It's just Star Trek. Entertaining, but I don't go there for the science. Don't get me started on the transporter.
I prefer the "2001" space station and the one Asimov and Mion depicted in the July 76 Geographic, anyway. More attention to science. (and I think, from the Mion paintings, the Asimov station has a hub dock that counterrotates to allow more than one ship at a time to dock.)
Incidentally, I've read that engineers who saw the wheel in "2001" cringed, to a man wondering why the under-construction section was coupled to the finished, spinning section. Build it, they cried, then spin it up and couple it to the spinning section.
But enough nerdery from me. Happy birthday, Hannerdad!
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Current long-duration orbital missions include spending as much as two hours a day exercising with bungee cords to provide some "down"ward force, and bone loss is still a serious problem.
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How exactly DO you work out in space anyway? With rubber bands only?
*Pictures weightless aerobics*
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Treadmill.
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Boxing would be hella fun to try as well...
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Gundam.
That clip illustrates a space-habitat along the lines of an O'Neill Cylinder (http://en.wikipedia.org/wiki/O%27Neill_cylinder). Structures like that are a bit grand for the title "space-station".
...what is the minimum gravity to avoid skeletal and muscular problems in the long term?
Unfortunately, the simple answer to this question is: nobody knows. Nobody has done the necessary long-term testing even on non-human animals. An even more ticklish problem for permanent habitation in space of the sort depicted in the Gundam universe, is the question of fetal development. Experiments on rats in free-fall done by the Russian space agency suggested that gestation in "zero-g" was a very bad idea with essentially catastrophic effects on skeletal and nervous development.
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Which is a little counter-intuitive since the embryo/fetus is floating anyway.
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Floating, yes; but it's not in 0-g. Even floating, you have a sense of up & down, and a foetus would have some sense of mass from resting in the pelvis.
Although the 6-month pregnant friend we have staying with us would love 0-g if only to get the little bugger off her bladder...
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There was a point in the WCDT about friction between a despun hub and a spinning station.
The power requirements of overcoming friction are surprisingly modest. Google has let me down coming up with exact numbers, but rotating restaurants and the Dubai rotating skyscraper use quite small motors. A high-tech structure like a space station might use magnetic bearings, cutting the power needs further.
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With nothing more than a free-to-rotate docking ring, you could walk (float) right into the hub and grab handles on the wall to adjust your momentum to match the station, then move out to the ring. It really wouldn't be any different than those fun-house rotating tunnels, and would probably be turning more slowly...
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Less need for spin, with all the associated structural problems, if you can avoid deconditioning using high-tech clothing: http://www.txchnologist.com/2012/next-gen-space-couture-to-feature-slimmer-silhouettes-and-new-accessories
Simulated gravity would still be valuable for the way it simplifies plumbing.
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You wouldn't want to love in your suit all the time. Eventually, you're gonna want to have a shirtsleeve environment to exist in. That stretch suit could be useful for the ride up or down, or for quick trips outside to replace the AE-35 Unit or the Illudium Pu-36 Explosive Space Modulator (Isn't it lovely?)
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For the bearings issue (non rotating hub interface) check out R.A. Heinline's description of such in "The Cat Who Walks Through Walls".
Mercury as a supporting agent/lubricant.
Another difficulty is: What is "Spin"? What is "Stationary"? when there is no fixed point of reference.
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The simple answer to those questions is to define "stationary" and "spin" with respect to an inertial frame. A working definition of an inertial frame is one that would be stationary "with respect to the distant stars". This raises the question that how on Earth can the
distant stars make their presence felt in a meaningful way here? IIRC the general theory of relativity gives an answer to that (because its equations are supposed to work in any coordinate system, even rotating ones), but it's been 25+ years since I seriously tried to understand that. And the math is a bit beyond me (but something that a certain snotty kid thought he can cakewalk thru), so hopefully more knowledgeable people can comment, too. Any physics majors around here?
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The twist is that a rotating structure is not an inertial frame, it's an accelerated (which is why we spun the thing in the first place, to use centripetal acceleration to simulate gravity)
There's also angular momentum to consider.
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Yeah, "inertial frame" is the key term, but the philosophical question that I find a bit difficult is the following. Imagine a single space station in an otherwise empty universe. How could you tell whether the station rotates or not? You can claim that it rotates, if and only if all objects on board feel the effect of this centripetal force. Or more generally, you can say that is undergoes an acceleration, if the passengers feel the resulting forces. But, like motion, acceleration is also defined with respect to a frame of reference. Without a single frame of reference other than those attached to the station itself you are lost. And it is not clear what happens, if your thrusters change the of spin the station. Will everybody feel a change in the artificial gravity, if you still don't know, whether you rotate or not?
Sir Isaac solved the problem by postulating an "absolute space", but this created other problems, and lead, eventually, first to the
special and later to the general theory of relativity (both by Einstein), the first got rid of the need for a frame of reference to define motion, and the latter (according to my feeble understanding) the need for a frame of reference to define acceleration (and hence also inertial frame) building on the observation that the effects of gravity and acceleration are locally indistuingishable.
I am under the impression (but also prepared to be wrong) that the distant stars do affect, and essentially give that frame of reference. The mechanism is vaguely similar to the way the nature balances its books, when there are moving electrical charges.
The laws of electromagnetism are immune to motion at constant speed. Yet moving charges create different forces (magnetic as opposed to the Coulomb force) that exactly compensate for the difference that would otherwise result from shifting to a stationary coordinate system to one that moves (at constant speed) together with the charged particle. Similarly, if your coordinate system is not inertial, e.g. it rotates with respect to the distant stars, then those distant stars would move at huge velocities w.r.t. your frame of reference, and then affect you by... making you feel an artificial gravity???? As I confessed, I can follow the math of the simpler case of electromagnetism but cannot follow the more complicated GTR.
I'm afraid I cannot exclude the possibility that I am talking crap, and that this philosophical problem of an "inertial frame" is not related to GR.
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Not an answer, but more information: http://en.wikipedia.org/wiki/Mach%27s_principle.
All inertial frames see the same events and physical laws, just with different numbers attached. Rotating frames see strange things like Coriolis force.
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Thanks. Mach was the name I was trying drag out of abyss of memory.
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If I was gonna live on anything that had to rotate, I'd rather it be an Omega Class Destroyer
:-D
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Does conservation of angular momentum prevent using the station as a giant flywheel to store energy from the solar panels when there's a surplus and then meet peak demands by slowing the station with a generator?
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I should know that, but it's been over 30 years since my last physics class (when I changed my majr to math).
I think, though, that it wouldn't work that way. The whole station is rotating (modulo the docking rings), not spinning on a fixed axis like the restaraunt atop the CN tower. Speeding it up (or slowing it) would take the firing of propulsion devices, not applying a motor/generator to the rotatng part from a fixed part.
Feel free to call into doubt any mistaken assumptions!
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In the absence of a way to tie a structure to the inertial frame, you'd need two structures rotating relative to each other whose relative rotation could be sped up to store energy, and slowed down to recover energy by reactive braking. In practice a small fast flywheel is used (they have been proposed for electricity storage on Earth).
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This has the disadvantage for a spinning wheel station that any change in the reaction wheel has an equal and opposite change in the rest of the station.
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Dual counter-rotating rings, then.
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For the Habitat? Absolutely not! That defeats the whole purpose of having a constant 1g environment.
You could build a momentum storage device with contra-rotating reaction wheels, but that's probably not much better than a battery.
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Correct me if I'm wrong, but isn't it so that with the existing technology solar power can more efficiently be used by heating up large quantities of water. Photovoltaic processes are less efficient. Of course, that does not need to apply in QCverse. And also, on a space station exposed to direct sunlight (when not shadowed by the Earth) heating may not be a problem.
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A thermal power cycle requires more mass and more moving parts, and creates a real problem dumping the waste heat. Vacuum is a good insulator. You need big radiators. Big, heavy, radiators. Photovoltaics lose on thermodynamic efficiency but win on mass efficiency.
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RE: Solar power and heating -- The first publicly released designs for a "wheel" space station, back when von Braun was selling the idea to Collier's Magazine in the 1950s, (http://science.nasa.gov/science-news/science-at-nasa/2000/ast26may_1m/) had the station deriving power from a trough running along one side of the torus which focused sun rays onto a tube of mercury running along the trough's base. The mercury would vaporize and spin a turbine to provide power.
Good point on the radiators, though. Major inaccuracy in "2001" was that Discovery should have had huge radiating panels to dump the heat from what was presumably a big honkin' reactor, but Kubrick didn't want to have to explain what a space-only ship was doing with wings. A decade later, people would accept X-wings uncritically.
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...and then people criticized the wings on Spaceship!
Funny how fashions change the perception of science.
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Yeah. The good ship EC-101 looks like it'd be at home in a hangar next to the 1960s lifting-body study vehicles, a Space Shuttle, and that X-vehicle (http://www.space.com/14305-secret-x37b-space-plane-landing-mystery.html) that is said to be in orbit. Jeph did what any respectable visual SF storyteller does: Extrapolate from known technology. Plenty of SF TV shows and movies in the 80s and 90s presented spaceships that basically looked like undercooked (or overcooked) Space Shuttles.
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An before the shuttles, it was rockets, rocket, rockets!!
Except when it was saucers.
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Don't forget bugs. Gotta leave some love for the Eagle and its juvenile delinquent cousin, the Hawk, from Space:1999.
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and that X-vehicle (http://www.space.com/14305-secret-x37b-space-plane-landing-mystery.html) that is said to be in orbit.
I love how it's supposedly "secretive" and "hush-hush" - and then there's a whole friggin' article about it, with diagrams and press statements and everything. The internet age really has redefined the meaning of "secret".
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Makes you wonder, though, how long it's been around, what "failures" have in reality been camouflage for clandestine successes. And though it makes me sound like a tinfoil-hatter for saying it, I wonder if the "exposure" of this "secret" is meant to distract us from the truly amazing stuff. I'm reminded of the Air Force general who, when asked if the U.S. was developing secret advanced tech out in the desert, said, "I sure hope so."
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"... because if we're not, we're in big trouble with the shit we have."
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"... because if we're not, we're in big trouble with the shit we have."
Yeah, if you go to the USAF Museum,, there are a couple sections of display that makes you think of a bunch of aircraft designers looking up at the sky and saying, "Welp ..." or maybe "Hey you guys, watch THIS."
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The nascent air force suffered the first airplane related death ever. Orville was demonstrating the new flyer, and a lieutenant flying with him died when the plane wrecked. Orville was injured, but recovered.
The naval air corps eventually decided on Curtiss flyers instead...
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An before the shuttles, it was rockets, rocket, rockets!! Except when it was saucers.
Reputedly Gene Roddenberry didn't want the spaceship that would become the Enterprise to look like a "rocketship" with fins, and the designer Matt Jeffries wanted to avoid the "flying saucer" cliché, yet arguably the Enterprise ended up looking like a combination of both.
My pet peeve with most fictional spaceships (at least in TV shows and movies) is that they are imagined with the decks parallel to the direction of travel like aircraft or marine ships. That makes sense for a space-plane type vehicle which actually lands or takes off like an aircraft, but otherwise, not so much. Even if you handwave "artificial gravity" and "acceleration compensators" it's hard to imagine that the technical problems would not be simpler with gravity and acceleration forces along the same axis. This would produce designs with decks stacked like the floors of a skyscraper with the engines in the basement, and much simpler turbolift design. Firefly took the whole "you must fly parallel to the floors" thing to a ludicrous level with its Alliance cruiser design in which the ship is shaped like a collection of skyscrapers (http://images2.wikia.nocookie.net/__cb20081008210550/firefly/images/4/41/Alliance_cruiser.png) but flies sideways!
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Whedon said the design was deliberately inefficient to show the nature of the Alliance.
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Wondered the same thing, Akima ... why complicate matters that are complicated enough?
Also (and I can't claim originality on this; someone with more letters after their name than I said it before I did) if you have artificial gravity control (powered by Unexplainium, not spinning) -- you HAVE your propulsion. No reaction motors or whatever "impulse drive" is, because you're already controlling acceleration.
Maybe simple reaction motors for attitude adjustment and the so-called "inertial dampers" or "dampeners" are just an automatic fine-tuning mechanism built into the gravity control, like a car's shock absorbers or an airplane's trim tabs.
I kind of think Spacedock from the ST movies would be a fine design for a starship, with the mushroom cap facing forward as a space debris shield (and the hatches on the underside, naturally). Habitat and such tucked up under the mushroom cap, other stuff further aft. Would make sense for everything from the reactionless drive to one of Larry Niven's ramscoops to Arthur C. Clarke's constant-acceleration spaceliner from "Imperial Earth."
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...attitude adjustment...
Sorry, been dealing with unruly students today. So this phrase popped out for me.
Mine's in a bottle at home... :angel:
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As long as conservation of momentum applies, you still have to push something in the opposite direction to go anywhere. It doesn't have to be something you carried on board if you have a solar sail, but there always has to be some form of propellant.
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Also (and I can't claim originality on this; someone with more letters after their name than I said it before I did) if you have artificial gravity control (powered by Unexplainium, not spinning) -- you HAVE your propulsion. No reaction motors or whatever "impulse drive" is, because you're already controlling acceleration.
Reactionless propulsion is popular in SF because it allows for spaceships that are not mostly fuel-tank, and that can land and take off without worrying about the rocket exhaust flame destroying Mos Eisley space-port. There are however gigantic problems with the idea in terms of our understanding of real physics all the way back to at least Gallileo, never mind Einstein. Most SF authors' handwaves amount to pushing your ship along with a gravitic pole pressed against some mysterious, infinitely massive, special reference frame: "I felt a great disturbance in the Force, as if millions of physicists suddenly cried out in terror and were suddenly silenced. I fear something terrible has happened."
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"These are not the AnthroPC's you are looking for..."
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Stay on target. Stay on target. Stay on tarBLAM.
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Imperial troops have entered the base! Imperial troops hav--krkrkkrkkrkrkkrrrkkkk
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Why does it always have to be snakes?
Oh, sorry, wrong franchise. :roll:
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Asps! Very dangerous! You go first!
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Dioxis. *inhales* :roll:
...
Wait, I'm sorry, I don'tunderstand fully,what are we playing? °O
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42.
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Oh, that's just your answer to life, the universe and everything, isn't it?
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People people calm down!
to bring some semblance of control (and you know carry on talking about actual stations) would a spinning design need to be perfectly balanced or is there just a level of tolerance(a la car wheel) to stop vibrations and tumbling?
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Balance is needed for something to spin on a fixed axis. Otherwise, when set to spinning, it will find its own center of mass and rotate about it. The problem with a car wheel that's out of balance is that the axis you want and the center of mass are different...
So no, the space station doesn't need to be balanced, but the wobble would mess with the g-force in different parts, depending on how severe it was.
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Balance is needed for something to spin on a fixed axis. Otherwise, when set to spinning, it will find its own center of mass and rotate about it. The problem with a car wheel that's out of balance is that the axis you want and the center of mass are different...
So no, the space station doesn't need to be balanced, but the wobble would mess with the g-force in different parts, depending on how severe it was.
So, if you had Sufficient reaction mass or reactionless thrust, could you avoid off-axis wobble by automatically exerting thrust on the opposite side to dynamic masses like people around the ring? (Like, say, with some sort of advanced AI controller...)
Also, is anyone else weirded out by how *big* Potter's room is?
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Yes, it struck me as remarkable for military quarters.
"Applying thrust" gets expensive in short order.
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Earin, it looks like a bunk bed behind her (shades of Lister's room only clean) and there could be another pair on the other side (IMO 4 officer rooms are pretty common, especially where space is tight, think Nuclear Sub)
Carl-E so if you were building a ring that was spinning, say at 1 rpm and you were walking around it would the imbalance cause the ring to slow down, start spinning erratically or other undesirable behavior?
[edit] rather than thrusters a 'maglev' style counterbalance around the outer edge?[/edit]
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Depends on the size of the station. The mass of a person coul be negligible if the station's large enough (think a BB in a tire), but get a large group in one place...
"..tonight's assembly is cancelled. Please stay in your rooms until balance is restored"
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Hm. I'd want in place some sort of regulation, similar to a fire marshal's, limiting occupancy in any one room. The net effect of that would be to have people more or less evenly distributed around the torus. A big enough torus, and enough people, and small discrepancies could be compensated for with the usual station-keeping maneuvers.
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I would say that it doesn't matter most of the time if the centre of gravity drifts a little away from the geometric centre of the structure. However, with docking being performed along the central axis, it would be advisable to restore the C of G there to make it stationary in preparation for docking to take place.
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The mass of the station is so much bigger than the mass of anything that would be moving around on it that any wobbles or eccentricities would not be noticed.
On a small boat, you have to be careful how you move so you don't tip the boat. On a big boat it doesn't matter because you're not big enough to make that much difference. The big boat still tips, but the displacement is measured in millimeters.
Plus, the more people you have moving around randomly, the more of their motions are cancelled out.
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The mass of the station is so much bigger than the mass of anything that would be moving around on it that any wobbles or eccentricities would not be noticed.
On a small boat, you have to be careful how you move so you don't tip the boat. On a big boat it doesn't matter because you're not big enough to make that much difference. The big boat still tips, but the displacement is measured in millimeters.
Plus, the more people you have moving around randomly, the more of their motions are cancelled out.
Except on the Black Pearl
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But they were moving in sync, and what's more, in simple harmonic oscillation with the ships mode of rolling.
If everyone on the station ran around the perimeter in the direction opposite the rotation, it might have a noticeable effect.
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So no marching troops! I'd imagine that a station large enough to have a decent size habitation ring and labs and accommodation for >100 people would weigh enough to stop a handful of people meeting up from becoming a problem then?
if you were actually going to build it, would you want to build the ring first (in airtight sections) and then add labs/habitation modules bit by bit balancing as you go?
a couple of things I've noticed about Jeph's design is that there are no emergency covers for the windows in case of accidental breaking, and that those doors (sliding I assume) don't look particularly airtight.
Of course I'm probably taking the whole thing far too seriously :roll:
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You'd have the situation of a big enough overall mass damping out the effect of individual people and other smaller bits of the station's mass moving around inside.
Wonder: If you were the sort who went in for running as an exercise, you'd get more of a workout running spinward (and so increasing your velocity around the circle, and therefore "weighing" more) as opposed to antispinward (decreased velocity and therefore decreased simulated weight). Again, a large enough torus would damp that out, by decreasing the overall rotation rate necessary for the desired g-equivalent.
As far as construction, build it, get the masses balanced and then spin it up. That actually was a problem engineers had the first time they saw Kubrick's version of the spinning-wheel station in "2001" -- the section under construction, they said, should have been completed in free fall (so you didn't have tools, parts and construction workers being spun off into the void), THEN spun up and mated to the existing section.
Windows and doors? I'm so used to SF space windows being made of transparent superstrongium (or better still, it's really just a force field) I take the handwave. Though, anyone remember "Space:1999?" The windows in the control room would break or crack at the slightest provocation, but an emergency repair could be made by laying a piece of office paper over the crack and sealing it with something from a handy spray can.
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Of course I'm probably taking the whole thing far too seriously :roll:
You'll fit right in!
Maybe we just haven't seen the airtight safety doors.
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DSL, re: the running question.
What a fascinating thought! I think, though, that the effect doesn't happen - the centripetal force exerted by the station holding you in when your foot touches the ground will be the same that moment regardless of the direction you were moving. However, the acceleration made when you push off is linear, and the motion of the station is circular, and so I think that the faster you go, the heavier you'll feel because of the added force from the greater accelleration in each step (F = ma).
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Carl-E,
Sounds like a question of which effect overpowers the other: Circular motion spinward or antispinward vs. the other vectors you describe.
Now what we need to do is to build a spinning torus space station and move up there to test that. Who's with me?
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Re spinward/antispinward jogging. I though about it a bit, when we first discussed spinning space station a while back, and Akima explained how the Coriolis force places a limit to the size of the station (too large Coriolis => crew resorting to barfbags). Carl-E is, of course correct in that the centripetal force is the same. However, the Coriolis force is also there unless your motion is parallel to the axis of the spin. And (barring a mistake in me mentally calculating the direction of the relevant vector cross product) the Coriolis effect will fulfill DSL's prediction: if you jog spinwise the Coriolis force will also be pressing you out into the floor, so your muscles have to work harder to lift your feet/legs. Similarly if you jog antispinward, the Coriolis force will be in your favor.
Mind you, I'm fairly sure that Carl-E's argument is the same thing viewed a bit differently. There are many (equivalent) ways of looking at it.
Edit: That was probably written the right way on my first attempt :-)
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Fun with physics: http://freefall.purrsia.com/zu/ffskates.gif
From http://freefall.purrsia.com/zu.htm – credit is important, right? – but I think hotlinking works for this image.
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DSL, re: the running question.
What a fascinating thought! I think, though, that the effect doesn't happen - the centripetal force exerted by the station holding you in when your foot touches the ground will be the same that moment regardless of the direction you were moving. However, the acceleration made when you push off is linear, and the motion of the station is circular, and so I think that the faster you go, the heavier you'll feel because of the added force from the greater accelleration in each step (F = ma).
That might be why Lt. Potter was out of breath from running to catch up to Marigold and company.
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Here's my thought:
You're standing on the "floor" of the torus as it's spinning. The point defined by you is moving in a circle. You experience a certain value of g.
Move spinward and you still describe the same circle, but faster than the station does. Your personal value of g is greater; you're heavier.
Move antispinward, you describe the same circle, but slower. You personal value of g is lower; you're lighter.
(This assumes you're not moving so fast to antispinward you cancel out the rotation, in which case you could, barring obstacles like bulkheads, missing MP3 players and pissed-off Air Force lieutenants, appear to float through the torus to antispinward from the point of view of someone standing on the torus floor.)
Coriolis effect, which if memory serves from my SF nerdier days depends on how fast you move through angles, would appear to diminish the larger the radius if the torus. There's a bit of old video somewhere from the early Soviet space program of the inside of a small room on the end of a centrifuge arm only a few meters radius but moving at speed to produce a comfortable fraction of g; the astronaut trainee inside throws a dart toward the outer wall and the dart describes a tight curve to strike a dartboard off to the trainee's side.
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Coriolis force is always perpendicular to both the axis of the rotation and also to the speed vector (in the rotating frame). Its magnitude is proportional to the sine of the angle between those two vectors (explaining why it is equal to zero, when your motion is
parallel to the axis of rotation, and also why it is at its largest when the motion is perpendicular to the axis of rotation). So when you jog along the perimeter of the spinning space station, it will be either "up" (towards the hub) or "down" (pressing you to the floor with extra force) effectively decreasing/increasing your "personal g". When you throw a dart in a centrifuge towards (or away from) the outer floor, the Coriolis force will be sideways. I am fairly sure that all the dartboards on HannerDad's station are on those walls that you would also place the donut toppings on (looking at the station from the outside).
The difference in "personal g" will not be very large in a practical setting. Starting with the numbers from Akima's spreadsheet of a station with radius 1000 meters spinning at 1rpm, the rim will be moving at about 100 meters/second. A world class sprinter can run at one tenth of that speed, and thus might be able to vary his/her personal g by 20 per cent. The centripetal force is proportional to the square of the speed, so the relative difference (unless very large) gets doubled.
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Ah. Yes, I completely forgot about coriolis. Nevertheless, I think my first point still stands - eihter way you run, in the inertial frame of reference, it's "uphill" since your accelleration vector is straight and the station isn't.
...and I just realized what I wrote. Sorry, Station. Not that there's anything wrong with not being straight... :laugh: :roll: :angel: :psyduck:
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Why are you apologizing if there's nothing wrong with it?
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Someone obviously hasn't seen Seinfeld.
"NOT... THAT THERE'S ANYTHING WRONG WITH THAT!"
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Ah. Yes, I completely forgot about coriolis. Nevertheless, I think my first point still stands - eihter way you run, in the inertial frame of reference, it's "uphill" since your accelleration vector is straight and the station isn't.
...and I just realized what I wrote. Sorry, Station. Not that there's anything wrong with not being straight... :laugh: :roll: :angel: :psyduck:
there's nothing wrong with being a holosexual
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Okay, I'm officially TOO much of a "layout" geek.
(Link to the full size view & the Wikia article here (http://questionablecontent.wikia.com/wiki/The_Space_Station).)
(http://images3.wikia.nocookie.net/questionablecontent/images/f/ff/SSECTbunk.png)
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Hmm. Correct me, if I'm wrong, but I don't think that there is a "spaceside" and an "Earthside". Remember that the axis of rotation is fixed with respect to the distant stars. IOW, the space station, unlike the Moon, won't have one side continuously facing the Earth. The Moon does that because tidal forces of Earth's gravity have locked Moon's own rotation to synch with its orbital period.
Ok, so the axis of rotation doesn't need to be exactly fixed, because there is precession (http://en.wikipedia.org/wiki/Precession), but I don't see that helping us here.
Actually I am little bit worried about this, because it would mean that one side of the station is facing the sun half the year. That surface could become very hot.
Space engineers, help me out!
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Skew, yes it could, however as has been mentioned by Von Braun, this could be used as a source of power (using mercury if memory serves), also because the station doesn't 'point' (rotational axis) towards the sun, there will be some parts heating as others are cooling, (see apollo PTC or 'barbeque roll') or if the station is designed to be orientated with one part permanently in shade then passive radiators could be mounted for heat venting, with an internally pumped heat transfer medium between the exposed parts of the body and the rads.
(one idea that occurs to me is that if you were ejecting 'waste' (and not worried about water preservation) it could be used as a heat sink, but the thought of boiling hot urine is not very pleasant)
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Actually, I'm going off of the basis of the first time we saw the station (http://www.questionablecontent.net/view.php?comic=2111).
Think about it - the "floor" of the station would be the outside of the torus, due to the gravitational spin. If the station is oriented where the center hub has one end "pointed" towards the Earth, and the other "pointed" upwards towards the stars, then the two "sides" of the torus would logically face earth-ward and star-ward.
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@jwhouk: Just to make sure. What I was trying to explain is that the pointed end in that image will not always be pointing towards the Earth. If it is pointing towards the Earth now, 45 minutes (or half an orbit) later, it will be pointing away from the Earth. That is because the station is spinning, so conservation of angular momentum (http://en.wikipedia.org/wiki/Angular_momentum#Conservation_of_angular_momentum) prohibits that pointy end from always pointing towards the Earth. It could always point at e.g. the North Star, or Sirius, or your favorite constellation, though.
The Skylab, the Space Shuttles or the ISS could/can move in a way that they always show the same side to us. You achieve that by making them slowly spin about another axis once per revolution. When the station has artificial gravity created by spinning, you give up on that. The faster spin rules.
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One constraint people are missing is that you don't want the solar panels to be in the station's shadow ever for a little while.
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Hmmmm.
The Centralised Bathing Room makes sense. It would cut down on what was required for water reclamation and storage
Hell, even B5, as big as it was, limited the use of water for bathing. Only Ambassadorial, Officers and Guest Quarters had Wet Showers, everybody else had Vibe Showers or used Centralised Bathing Facilities, such as in the 'Fury Pilots Ready-rooms.
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I want to point out, as I did to IICIH, that this was all a guess on my part.
What I'm assuming is that the station is spinning around somewhat like a top as it orbits the earth. The solar panel remains facing the sun as it orbits the earth, just like (I'm assuming) Skylab, the ISS and Mir did with their panels.
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One constraint people are missing is that you don't want the solar panels to be in the station's shadow ever for a little while.
Can't you solve that problem by attaching the solar panels to the spokes of the wheel, and have them rotate (very slowly) around the spokes? I don't see a solution that does not involve periodically moving solar panels from one side of the station to the other. That may be just my personal limitation, though.
Edit: Well, a semi-obvious alternative is to make the axis of rotation perpendicular to the plane of Earth's orbit around the Sun. Then the solar panels sitting a few hundred feet above the plane of the doughnut will always see the Sun. You do need a full circle of panels in that case, because otherwise the rotation of the station will make a panel face away from the Sun once per minute (again assuming that the station rotates 1RPM).
Rephrasing my main theme: Basically artificial gravity turns the spinning space station into a gigantic gyroscope. When you have a gyroscope inside a fighter plane manouvering a full 360 degree loop, the axis of the gyroscope is always maintaining its orientation relative to the distant stars, and it cannot stay aligned with, for example, the pilot's spine. That is sort of the whole point of having the gyroscope.
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Can't you solve that problem by attaching the solar panels to the spokes of the wheel, and have them rotate (very slowly) around the spokes? I don't see a solution that does not involve periodically moving solar panels from one side of the station to the other. That may be just my personal limitation, though.
Edit: Well, a semi-obvious alternative is to make the axis of rotation perpendicular to the plane of Earth's orbit around the Sun. Then the solar panels sitting a few hundred feet above the plane of the doughnut will always see the Sun. You do need a full circle of panels in that case, because otherwise the rotation of the station will make a panel face away from the Sun once per minute (again assuming that the station rotates 1RPM).
This sort of thing is why space-habitat proposals often involve mirrors, although Jeph's plainly does not. The Stanford Torus study, for example, proposed an angled, non-rotating mirror to reflect sunlight onto solar arrays mounted between the "spokes" of the "wheel", and I think that would work on similar, if less grandiose, space-stations. In Earth orbit, there's still the problem of passing through Earth's shadow, so you'd need energy storage facilities, or auxiliary nuclear generators, or both.
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Or regenerative braking. I bet there's a lot of stored energy in the station's rotation and that you could ride out an eclipse without causing disturbing shifts in people's apparent weight.
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Braking against what? In this situation you're really speaking of using a faster flywheel to store energy.
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Is it beyond the capacity of batteries? Recharge them when in sunlight, use them when in the dark. The Earth's shadow comes and goes in a 90 minute cycle after all. I'm no engineer, so cannot guesstimate, whether batteries can store enough electricity to run the station for 45 minutes. Without filling up the entire station with those batteries that is?
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The Qinetiq Zephyr had enough battery capacity to fly through the night, loosing 10-15,000 feet in the process, obviously its an aircraft, not a station but in principle if weight wasn't' an issue you could have as much space devoted to batteries as you needed. The problem would be the charge/discharge cycle, even deep cycle batteries are only good for a few thousand cycles, and if you are discharging several times a day (orbit dependent) then they won't last too many years before they need to be replaced.
using a separate flywheel is out, and unless you can realistically decelerate the station to generate power and then accelerate it in sunlight (is this possible with a large enough station and not affect g?)
the two best options i see are a closed loop fuel cell/electrolysis unit but even this will have a limited operational life, dependent on the membrane. Or a 'nuclear battery' such as one of the larger SNAP units developed by NASA but this would require deactivation of many of the systems during the 'night' as I assume that the SNAP won't be able to generate enough power to keep the entire station running (otherwise what is the point of the solar panels).
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Braking against what? In this situation you're really speaking of using a faster flywheel to store energy.
Conservation of angular momentum means the station's rotation will speed up or slow down as you speed up or slow down the flywheel.
The solar panels could be there to sustain operations while the antimatter reactor was being refueled, and to bootstrap it afterward.
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I could sort of see energy transfer from the flywheel to the station (eddy currents or some form of regenerative braking), but how could do you turn the kinetic energy stored in the rotation of the station back to the flywheel (or turn it into electricity by other means)?
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Run the connection between the station and the flywheel as a motor.
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Ok. I had to think about this. My mistake was in thinking that we would first use the flywheel to speed up the rotation of the station itself, and only then try to use that energy. If we do that then there is no speed difference remaining to be used as a motor. So during the "night" we use the speed difference between the flywheel and the station as a motor. At "dawn" the flywheel and the station are spinning at the same rate. This will also speed up the rotation of the station by a tiny amount. To prevent that speeding up from accumulating over a long period of time (and dramatically changing the level of artifiicial gravity), we need to use the solar panel to slow down the flywheel on alternate "days".
But how did we use solar power to accelerate the flywheel again? And can we actually build a massive enough flywheel?
Arggh. I shall leave this problem for the engineers to solve. :psyduck: :psyduck:
Edit: Thank IICIH (see below). It looks like I may have forgotten a conservation law or two :psyduck:
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It can be either massive or fast. Flywheel engineers, at least for mobile applications, seem to go for fast.
Just wire up a motor-generator like the Prius uses. Put energy in, and it spins up the flywheel, spinning up the station by reaction. Pull energy out, and it equalizes the spins of the flywheel and the station.