Coriolis Station Physics

[laforge]

Firstly: Having the Coriolis effect in a rotating space station is unavoidable. However small it is, it's always there.

I said that you minimize the effects by increasing the size of such stations and never spoke that you can avoid it completely. Text comprehension.

Secondly: The Coriolis effect is already in the game. See this video at 1:55 See how the ship veers to the left as it gains distance from the pad? That's the Coriolis effect.

Your observation would fit to every game in which you can make this maneuver, even the old elite games. What I had in mind - as you would see by the examples - was the situation when you walk outside of your ship within such a station, i.e. the physics on the station (if that is what we will have some day). Especially the gradually change from high centripetal force regions to almost zero near the axis. For example if it would be possible in the game to pick something up and let it fall down to the ground, it doesnt make much sense to implement how the Coriolis effect will alter this motion, because it just makes additional complifications.

Thirdly: Nothing wrong with naming a rotating space station after a famous scientist who extensively studied rotating frames of reference.

The general practice is to name it according to those persons who actually made the idea public in the first place. Probably Tsiolkovsky but definitively not Coriolis.

 

[Razorwire]

Cosmic, If you are moving in a circle, with no gravity, your velocity direction (vector) at any point is the green arrow in the pic above. If the circle wall vanished for any reason, the green arrow is the direction you would go in.
The wall of the circle changes your vector constantly to the blue line, which applies a constant acceleration in the direction of the axis (the orange arrow).
You would feel this as a weight toward the rim, same as you feel a weight toward the floor in an ascending elevator.

Which is why the floors in a rotating station are concentric circles around the axis, not slices away from it.

There's a fairly clear explaination of artifical gravity, rotation and orbits here.

 

[Yaffle]

It's possible that the phrase "artificial gravity" is causing confusion here. There is no gravity "made" anywhere. Instead a force is being substituted, which is the centripetal force required to stop an object flying off in the direction Razorwire explains.

 

[NeilF]

I said that you minimize the effects by increasing the size of such stations and never spoke that you can avoid it completely. Text comprehension.

RE minimizing the effect - I'm right in saying the same effect (in reverse) happens here on Earth? ie: If you could remove air resistance, and throw a ball miles up in the air, it wouldn't come straight back down again, but fall back along the line of rotation?

The effect we're seeing inside our ED space station is just a magnified (opposite) version of this is it not?

 

[Captain N]

I said that you minimize the effects by increasing the size of such stations and never spoke that you can avoid it completely. Text comprehension.

You said they're something you don't "want" in your space station. You can't have a rotating space station that doesn't have the Coriolis effect.

Your observation would fit to every game in which you can make this maneuver, even the old elite games.

You can't do that manoeuvre in the old games. It was not possible to fly or land inside the stations. They didn't even simulate rotational momentum inherited from the station that you launched from. Rotational assist was always on in FE2/FFE.

What I had in mind - as you would see by the examples - was the situation when you walk outside of your ship within such a station, i.e. the physics on the station (if that is what we will have some day). Especially the gradually change from high centripetal force regions to almost zero near the axis. For example if it would be possible in the game to pick something up and let it fall down to the ground, it doesnt make much sense to implement how the Coriolis effect will alter this motion, because it just makes additional complifications.

That is the same effect demonstrated in that video, just on a smaller scale, and less noticeable. Simulating it would not be any different.

The general practice is to name it according to those persons who actually made the idea public in the first place. Probably Tsiolkovsky but definitively not Coriolis.

Which idea precisely? Did Tsiolkovsky invent cuboctahedron-shaped stations? I never heard about this.

 

[jahvetti]

I guess Coriolis effect is called that exactly for reasons mentioned.

Rocket equation paper: К. Э. Циолковский, Исследование мировых пространств реактивными приборами, 1903.

Coriolis effect: G-G Coriolis (1835). "Sur les équations du mouvement relatif des systèmes de corps". J. de l'Ecole royale polytechnique 15: 144–154.

All info available in Wikipedia as well.

 

[Ittiz]

There's a fairly clear explaination of artifical gravity, rotation and orbits here.

That page is great, I love the little stick figures they use in their examples.

 

[Slawkenbergius]

First: To call these stations 'Coriolis Stations' is a horrible description. In fact Coriolis effects is something you do not want in your station. I would simply call them 'Rotating (Space) Stations'.

Coriolis is an awesome name and has stuck in the imaginations of gamers since 1984. 'Rotating (space) Stations' would equally refer to the 'wheel' design and other designs in the Elite universe, as well as being totally dull. Good thing you weren't involved in the naming process! The fact that anyone who cares to look it up will learn some stuff about physics is also a real positive.

But I though we did... I remember talking about Dodec stations somewhere...

There were Dodecahedral (Dodo) stations, but they're a different design to the Coriolis, which is a cuboctahedron.

 

[Susimetsa]

There were Dodecahedral (Dodo) stations, but they're a different design to the Coriolis, which is a cuboctahedron.

Thank you! So, using the shape name to refer to a station is as much Elite tradition as using the "Coriolis" name.

 

[Dirk Braben]

"Yes. Please don't forget about me"....

 

[NeilF]

It's possible that the phrase "artificial gravity" is causing confusion here. There is no gravity "made" anywhere. Instead a force is being substituted, which is the centripetal force required to stop an object flying off in the direction Razorwire explains.

From my noddy understanding, with someone standing on the inside of the hull of the spinning station:-

• The person has inertial (in the direction of spin).
• The hull is applying a centripetal force on the person by keeping them in place.
• They feel a centrifugal force, which feels somewhat like gravity.

Centripetal force is what keeps them from flying off. Centrifugal force is what they "feel" is being applied to them. ie: Being pushed straight down on to the floor/hull (by what is in reality their inertia). It's what they would perceive as being an artificial gravity in effect.

 

[CoSm1c gAm3r]

Cosmic, If you are moving in a circle, with no gravity, your velocity direction (vector) at any point is the green arrow in the pic above. If the circle wall vanished for any reason, the green arrow is the direction you would go in.
The wall of the circle changes your vector constantly to the blue line, which applies a constant acceleration in the direction of the axis (the orange arrow).
You would feel this as a weight toward the rim, same as you feel a weight toward the floor in an ascending elevator.
.

Am I missing something or there is no pic you mentioned?

 

[laforge]

Captain N, by trying to argue with vacuous things it wont get better...

You said they're something you don't "want" in your space station. You can't have a rotating space station that doesn't have the Coriolis effect.

As I said: text comprehension isnt everyones strength... even after my polite hint. if I do 'not want' something this does not mean that I can avoid it. Is that still not clear?

You can't do that manoeuvre in the old games. It was not possible to fly or land inside the stations. They didn't even simulate rotational momentum inherited from the station that you launched from. Rotational assist was always on in FE2/FFE.

All you do is to fly your ship past a rotating space station and compare your ships drag with respect to that rotating system. This is perfectly doable in the old games. I wonder how often I have to repeat: What I meant was especially Coriolis effects when walking on the station.

Which idea precisely? Did Tsiolkovsky invent cuboctahedron-shaped stations? I never heard about this.

Is that now an argument to justify to name your 'cuboctahedron-shaped stations' 'Coriolis stations'?

To my knowledge Tsiolkovsky was one of the first persons who published about the idea of using rotation to generate a gravity effect on space stations. Therefore if there is someone to name these stations then he would probably deserve it. Now if the shape of these stations is cylindrical or more like a dodecahedron... really who cares about that detail in a name for the category of these stations? Even in this topic people give the stations a general name without refering to a special layout.

 

[laforge]

RE minimizing the effect - I'm right in saying the same effect (in reverse) happens here on Earth? ie: If you could remove air resistance, and throw a ball miles up in the air, it wouldn't come straight back down again, but fall back along the line of rotation?

The effect we're seeing inside our ED space station is just a magnified (opposite) version of this is it not?

If you throw something straight up, then it will also receive the angular velocity of your current location. So better make that experiment simpler by letting something fall down to earth (without air effects) from a point which does not rotate with the earth. Then yes: obviously by the earths rotation that object will fall along a curvilinear motion with respect to the rotating frame of the earth. Anyways, its all a bit clumsy do describe with words.

Coriolis effects do not need a gravity well - as in the case of space stations which are discussed here.

 

[Ittiz]

If you throw something straight up, then it will also receive the angular velocity of your current location. So better make that experiment simpler by letting something fall down to earth (without air effects) from a point which does not rotate with the earth. Then yes: obviously by the earths rotation that object will fall along a curvilinear motion with respect to the rotating frame of the earth. Anyways, its all a bit clumsy do describe with words.

Coriolis effects do not need a gravity well - as in the case of space stations which are discussed here.

Yep people tend to forget even on earth we are subject to coriolis forces from the earth spinning. It's what causes our interesting weather, jet streams, doldrums and the like. The reason we don't feel it in our every day life is because the earth is so huge with respect to it's rotation rate. Of course the coriolis forces we experience from earth's rotation are the opposite we get in a station since the rotation pushes us away from the surface. If you had a 1g rotating station the diameter of the earth the coriolis forces would be next to nill.

 

[Sanpaku]

These effects will make life on a small rotating space station impracticable and is the main reason why such stations are not build yet: Such stations must be large in order to mimimize these effects (= too costly).

Only if one is planning an enclosed ring/sphere.

A very plausible design for any manned Mars mission is to spin the return stage and the transit habitat/descent stage at the ends of a tether, to simulate Mars surface gravity for the months of a transfer orbit. It does require rotating radio antennas, but its by far the simplest solution to maintaining muscle mass for the long journey.

Likewise, in early stages of space infrastructure, one wouldn't need a large enclosed volume, just enough room for workers handling material. I rather hope early stages of Coriolis station construction model this, with two synchronously rotating partial rings (the docking aperture and the opposite face), with the girders completing the rings, the faces, and connecting the two slowly accumulating.

 

[Shigawire]

What an awesome thread! Very geeky stuff indeed.

CoSm1c gAm3r, real funny posts about the hair dryer floor design.
You just need to learn about angular momentum.

You can compare that to sitting in a merry-go-around in a kindergarten or tivoli. It still applies, even if it's on Earth.

Imagine a direct line (vector) moving from your body in the direction of the rotation.
Remember, your body is not being thrown in a curve with the rotation. Your body is being thrown in a straight line. That straight line is the ideal vector that your body will always try to move in. After a short while rotating in that fantasy thing, maybe a few seconds.. your body, and all your furniture would start to slide outwards, into the round "wall" facing outwards from the circle. I don't know what your hair dryer ceiling is useful for, but your body isn't being thrown upwards from the floor. Just outwards to the edge of the circle.

Here's a simple exercise to do on your drawing, one that you can learn from (learn from doing, right?):
Draw 2 frames of your station. Forget the hair dryer.

1. Leave frame 1 as you already have it (your basic station cross section)
2. If you have a drawing app with layers (Photoshop, Gimp etc), make a new layer. Draw a straight line (vector) 90° from the floor where the stick man stands, toward the rotation direction, draw it far enough to reach outside the station.
3. Note where that straight line intersects with the outer circle, and continues out towards space. Make a new layer, and mark the intersection spot with an X.
4. Now you will draw Frame 2, by copying frame 1. If you use Photoshop, Gimp or something with layers, you can keep the "line vector" and "X" as two immovable items/layers on top, while you rotate the layer "Frame 1" below. Rotate Frame 1 so the floor in your room intersects with the X.
5. Now you have to move your stick man to the wall near X.

When you've done that, I think you would have learned a lot. Because doing is learning.


Back on topic:

I would like to add the medical necessity of Earth Gravity. If you do not take this into account, you will lose a lot of bone mass, and muscles will deteriorate. If you are too long in low gravity, you will not be able handle landing on planets. Anyone living in an apartment close to the center, with far less than 1G, would have to travel to subscription based exercise centers at the edges of the space station where there is 1G. Imagine even extreme athletes would go to special exercise rooms extended even farther out from the edge of the station by elevators (stairs would be far too unsafe). Here the exercise freaks and athletes would get their day's work of exercise done in less time with even higher than 1G.

 

[Pyros]

Back on topic:

I would like to add the medical necessity of Earth Gravity. If you do not take this into account, you will lose a lot of bone mass, and muscles will deteriorate. If you are too long in low gravity, you will not be able handle landing on planets. Anyone living in an apartment close to the center, with far less than 1G, would have to travel to subscription based exercise centers at the edges of the space station where there is 1G. Imagine even extreme athletes would go to special exercise rooms extended even farther out from the edge of the station by elevators (stairs would be far too unsafe). Here the exercise freaks and athletes would get their day's work of exercise done in less time with even higher than 1G.

In ED universe, not really. Medical science evolves, and a space faring civ has certainly found ways to deal with this (and much more) in a more subtle way. But you know that already

 

[drew]

From my noddy understanding, with someone standing on the inside of the hull of the spinning station:-

• The person has inertial (in the direction of spin).
• The hull is applying a centripetal force on the person by keeping them in place.
• They feel a centrifugal force, which feels somewhat like gravity.

Centripetal force is what keeps them from flying off. Centrifugal force is what they "feel" is being applied to them. ie: Being pushed straight down on to the floor/hull (by what is in reality their inertia). It's what they would perceive as being an artificial gravity in effect.

Yes. There is no 'gravity' being generated. It is the inside edge of the hull pushing up and steering the individual in an circle as their inertia attempts to make them travel in a straight line at right angles to the centre of the station's rotation.

Excellent work folks. Looks like the physics holds up well. Good to see the thread still running.

Here's my next observation, based on the dev diary (and I've included something similar in my book).

David mentioned that the interior was mostly empty, there is 'space' allowing a large empty living area with space for parks and lakes. That's going to be quite a sight.

An interesting issue in this environment is weather.

I'm not sure how temperature is going to be maintained in this environment, but regardless hot air rises and will attempt to rise away from the 'ground' of the station (the maximum radius inside edge).

As it does so it will have a higher velocity than the air its rising through, due to the aforementioned coriolis effect. To lose this velocity air is going to move, which means some significant wind will be generated. The air is also going to cool. If there are lakes in the inside of the station, the air may be sufficiently moist to precipitate out.

I don't know whether (!) this sort of thing has ever been modelled, but some kind of Hadley cell rotation is going to set itself up within the confines of the station.

I predict a layer of clouds just outside the central hub, with occasional rain. Without some clever engineering there could be significant turbulence in the internal atmosphere - assuming a large open space.

Cheers,

Drew.

 

[Shigawire]

In ED universe, not really. Medical science evolves, and a space faring civ has certainly found ways to deal with this (and much more) in a more subtle way. But you know that already

No I don't. What is this information you speak? Indulge me.