Re: the movie Interstellar–and how they attempted to play baseball on the rotating station. That wouldn’t work, would it? While the ball is in the air, no force is acting on it, the “gravity” that the inhabitants feel is solely generated/felt only while they are standing on the inside of the ring, right? So any projectile launched off of said surface would not come back down like it would in an actual gravity well, and would presumably just rattle around in the rafters of the station. Likewise if you attempted to play golf there.
The balls in the air would have no forces on them, and from the frame of reference of the players would therefore come back down.
Think of it this way: The ball is moving when it leaves the shell of the station, right? And so, with no forces, it’ll continue to move. Which means that it’ll eventually hit the shell of the station again. Which, from the point of view of the people standing on the inside of that shell, would be “coming back down”.
The paper you link to predominately uses old data from 1962 to 1969. It is a largely review of old data, not newly-performed physiological research.
By contrast the 2000 Lackner paper IS new science and uses newly-performed physiological research by an JR Lackner, an MIT professor of physiology. By newly-performed I mean genuine new biological research vs rehashing old data from 1962 to the 1970s.
Lacker’s conclusion states: “Concerns that it would be difficult if not impossible to adapt to Coriolis forces generated by movements made in a vehicle rotating at more than 3 or 4 rpm have turned out to be unfounded.”
The 2001 Discovery centrifuge was not accompanied by a guarantee of scientific authenticity, and in fact the dimensions and rotation rate were not stated in the movie, only in production notes and maybe the book.
However it turns out that based on recent research (vs the early 1960s research) that the 2001 Discovery centrifuge parameters are possibly within adaptation range of selected humans, such as specific astronauts. Reviewing this actual published data (vs an abstract), it becomes obvious the 2001 scenario cannot be totally discounted. Even some of the old data shows those parameters might be within the adaptation limits of selected individuals.
This doesn’t mean it would be guaranteed to work for any “space tourist”. However for highly filtered, selected astronauts chosen for specific physiological attributes, something like that might conceivably work. And if it turned out to require a modestly larger radius or different rotational speed, the basic concept would still be sound. IOW a redesigned Discovery with a 70 or 100 ft diameter spherical habitat (vs 38-40 ft) and proportionately scaled up structure would look indistinguishable to a movie audience.
The 2001 centrifuge case is not like other fictional movies which took gross liberties with known science. Those are so prevalent that it’s easy to fall into a critical mindset that they are all equally inaccurate.
The difference between expected plain thrown-ball trajectories, and those you would see in a spinning drum space station - that’s exactly what “Coriolis force” is. Like centrifugal force, Coriolis is a corrective fictitious “force” applied to compensate for the fact that the frame of reference itself is accelerating (in a circle). Apparent motion - throw a ball straight up, it will come down anti-spinward. Throw it parallel to the axis of rotation, it curves downward and to the anti-spinward. Throw it spinward, it slows and falls faster, throw it anti-, it falls slower. Like centrifugal force, this is just an unsecured object displaying inertia, but to make it look normal in an abnormal frame, we add fictitious coriolis force.
(Think of a pendulum at the north pole. We would expect a pendulum to simply swing back and forth in a straight line; but as the earth turns underneath it, we would see the swing line turn 360 degrees every 24 hours from the observer’s point of view.)
Oh, yeah, baseball on a rotating space station of reasonable size would certainly be a lot different than on the ground. To someone who’s used to terrestrial baseball, everything would be moving all wrong, and it’d be impossible to predict motions well enough to catch a ball, or throw it to the right player. But I imagine that people who live there would get used to it and be able to adapt.
You have a friend who’s so slender that her mass experienced a different acceleration than other masses? That is slender indeed!
How high can she jump?
Dunno how it can be explained, but she wasn’t pressed against the rim of the barrel with enough force to cling to it, the way us bigger blokes were.
(Maybe she’s just slippery?)
I dunno. None of the above, very intelligent-sounding descriptions seems realistic to me at all. I imagine that I am weightless, in the center of an already spinning space station, and when I try to move towards the outer rim, I’m not drawn or sucked or attracted to the surface of the inner side of the “rim,” I’m just pushed sideways by the “spokes.” And if they are turning at a constant rate, not accelerating, as soon as I AM turning at the same speed as they are, they cease to feel as though they are exerting pressure on me. When I reach the inside of the “rim,” and try to stand still or move, the force being applied to me by the turning of the rim isn’t coming upwards from under my feet, it’s going sideways in a large arc. I imagine it would be more like being on a stairmaster than anything else, with a ramp in place of squared off steps.
Anyway. Mainly wanted to mention a small thing, someone above said they’d not seen a story where the space station was spun up, or where changing the spin was a part of the story, and I remember an old 007 movie with exactly those elements. Moonraker. Just mentioning it for fun.
I’m not educated in physics all that much, but I seem to recall that gravity doesn’t behave like speed, it behaves like acceleration. Isn’t that right?
“What’s he doing now?”
“I think he’s attempting re-entry…” -Moonraker
If you were floating in the middle of a giant drum, like those L5 environments you see illustrated every so often - a giant pressurized can spinning on the longitudinal axis…
Yes, as long as you stayed in the center, no gravity, you just float around. But as they cound on various space stations so far, even without gravity, you meander. Air currents and other odds and ends (microgravity, your own breath, etc.) cause you to start moving. If you aren’t properly nailed down, roped down, or whatever, eventually you meander outward toward the rim (every direction except the axis is outward…)
When the station was first 'spun up" the air would not be going along, but like turning a cup of coffee on a lazy susan, eventually friction will drag the fluid along so it rotates just like the container, an analogy would be how a car drags air along in its wake.
So you meander from the axis, not anchored. As you leave the axis, you are still not rotating with the station. But - the air is. It will start to blow you spinward… but straight line blow moves you further and further toward the rim. Eventually you will spiral out to hit the rim at a fairly good clip. Remember, in this space can, even if it’s tiny, say 300 feet in diameter, you’re doing the equivalent of falling from several dozen feet - the last 30 feet or so will be close to 1G. Splat.
So you start from the axis weightless, and grab a spoke. Here, air does not matter - you can do this in a spacesuit or naked in a giant spinning air can. You start sliding downward (outward) on the spoke. Near the center, you feel nothing. As you work your way out, you start to feel weight - actually the centrifugal force. You are not pushed against the spoke so much as being pulled down it.
(Ever been on that ride in a playground, where there’s a spinning platform and you try to hold the handrails?
As the kids spin it faster, you aren’t pushed against the handrail - you are being flung outward. This is the same effect. If the station’s spoke doesn’t have a ladder or elevator platform or something, you will just slide right down, faster and faster, adding friction burns to the final splat effect.
Or, you meander in a vacuum in a giant spinning can, say. you will meander until you eventually hit something. If you are lucky, the end walls near the axis. Not lucky, you and your spacesuit hit the outer wall, and the effect is like falling out a car door at high speed (or like the roulette ball catching the spinning wheel…)
http://www.artificial-gravity.com/sw/SpinCalc/
Spincalc tells me a 100m ring needs to spin at about 3rpm to get 1G (9.8m/s^2)
In this situation, the outer rim is travelling at 31m/s or about 102ft/sec. Keeping in mind that 60mph is 88ft/sec, you are planning for some serious roulette ball effects if you meander into the rim in a vacuum at this speed. In air, the wind of the rotating atmosphere would blow you along so you would have a combination of being accelerated to the point where you “fall” several dozen feet at close to 1G, plus if the wind doesn’t get you fully up to speed, you do risk a combination of both a high fall and a roulette wheel bouncing rolling impact.
IIRC, it was the second book of Karl Schroeder’s Candescence series that opens with this sort of scenario…
(Emphasis mine.)
This is a common misconception. It’s easily explained with vectors but the short answer is any change in magnitude OR direction IS a change in velocity (which is a vector (which has an amplitude as well as a direction)).
There really is no such thing as rotation without acceleration. It’s not acceleration in the sense that the turning thing is speeding up (like an engine revving) but that everything attached to the turning thing wants to fly off in a straight line and the turning thing is forcing them to go in a circle.
The turning thing is forcing them to go in a circle by exerting an inward force toward the center that physicists and engineers call centripetal force but basically it’s just the structure just holding itself together.
So when you’re climbing down a ladder from the axis of rotation, yes you are pushed sideways by the motion but as the ladder, & your arms & your legs bring you into rotation with the rest of the object you will begin to feel “weight” as the centripetal force from the station is trying to keep you from flying off in a straight line from the little bit of velocity you just acquired.
I think I grok what would happen to a free projectile in such a station (system)-it would keep moving on the initial vector, but eventually would MEET the curved wall of the station as the station continued to rotate underneath it. At first I thought that you could ‘escape’ the rotating forces (call them what you will semantics shemantics) by not touching any part of the rotating structure (and just float above it in freefall), but apparently the curving surface would eventually ‘catch’ up to you. I’d sure like to see a diagram of such a projectile in said system tho.
I’d imagine if you hit a high enough popup that it could reach the zero gee center, and thus never ‘come back down’, tho…
Quoted for emphasis.
Another example is planets orbiting the Sun. Nothing is pushing the planet forward in its path. It is constantly pulled towards the Sun by gravity - i.e. it is constantly accelerating towards the center of the circular orbit. (OK, elliptical.)
I recall some sci-fi story scene where a spaceship creates temporary artificial gravity by flying around in a circle with constant thrust. This may sound counter-intuitive, but it will work. The rocket engine needs to point away from the center of the circle all the time (i.e. accelerate towards the center of the circle).
What would stop it in the exact center? Admittedly there’s no rotational-gee force there, but it had momentum to move into that spot, and that momentum would still carry it out. Assuming that there isn’t something that would exert a force to keep it there, that is.
Possibly one of the stories in Charles Sheffield’s The McAndrew Chronicles
As I said - in a vacuum, floating free in an enclosed spinning can (starting, say from the center), you would just meander. There’s no such thing as pure zero G, and you would float around, with micro differential effects of gravity possibly moving you around, etc. You will drift, unless you make an effort every so often to correct your position. You would be fine as long as you did not drift into a moving part. The closer to a fast-moving outer shell you make contact, the more spectacular the result.
In a can full of air, ( O'Neill cylinder - Wikipedia ) consider it like this. The spinning air can will eventually end up with most of the air also rotating with the can, due to friction on the surface. Draw a big circle. This is the outside circumference surface of the can. Now draw assorted smaller concentric arc arrows each a slightly smaller length; these are wind speed arrows.
So you meander a little off of center… you catch the wind. The wind pushes you in the direction it is going, spinwise. However, at any one point in time, it pushes you on a tangent. Thus, you are pushed a bit farther out toward the circumference surface… where the wind is stronger and pushes you further forward, faster, and hence even more outward, even faster. Eventually, you hit the circumference surface. Splat.
More to the point, no matter what direction you point the rocket will always be away from the center of curvature, and you’ll always get the pseudo-gravity on board. If you’re changing the direction so as to fly in a circle, that’s probably just because you have some reason you want to stay near some particular point.
" Moment of Inertia" is the name of the story I think.
To imagine how contact with the ground creates “gravity”, I think of how it would be from the outside of the station. Imagine a giant tire spinning at a fast rate. If you’re standing near it, you won’t feel anything more than a breeze of air. But once you contact that tire, you’re flung away from it with great force.
The artificial gravity from the inside would work the same way, just in reverse (pulling toward instead of pushing away).
In fact the rotation of the rocket can be considered separately from the thrust. A slowly rotating rocket (with engines off) will not have much physical effect on its passengers, particularly if they are near the center of rotation. Engine thrust, however, will cause artificial gravity regardless of how the rocket is changing direction.
In all these cases, you can determine the strength of gravity simply by looking at the forces contributing to your position. In a rocket, you’re shooting particles out the end. A capsule on a tether has tensile forces on the tether–and behaves identically to a capsule being towed in a straight line by another ship (with the same tensile force on the tether). A circular part of a space station will have forces at the ends, and the gravity will be identical to a planet with a bridge that experiences the same end forces.