Simulated gravity using rotating two-part rope-linked ship

[Cesrate]

Well, does the angular velocity count? I mean, if the rope-linked ship rotates very fast, will astronauts fell they are really rotating instead of just in a simulated gravity field if they can't see the outside? (Seems to be Biology+Physics)

And… how long would you support for the rope? And how fast ship rotates?

Well, be aware that the formula is g=v^2/(L/2), you must create enough gravity:)

[shand]

the astronauts will feel it as rotation as it spins up, but once it settles at (i assume 1 G) it will feel like home. remember they G-test the astronauts by rotating, our sensation of gravity is simply one of force, we cant feel the source of the force. once we spin up all we feel is the force countering our inertia, which is an inward force, so assuming our heads were pointing in, it will feel like gravity.

as for lengths and rotation speed, its a compromise between the two. the longer the pivot, the faster the spin will have to be (is that the right way round), since there is very little cost in a faster rotation (once its got going) and a very real cost in getting said system up (volume and mass of launch). Ithink the answer will be, as short as possible given the required space. for example if you just wanted a looroom (gravity is useful on the bog) i'd have the pivot point cm's above the head.

You also have the additional problem of this spinning bit imparting a rotational force on either, a reaction mass, or the space station. in ksp this isnt too much of a problem, but on the ISS, you'd have to be careful not to overload the reaction wheels.

[Nibb31]

What you are mentioning is called the Coriolis effect, which is a side effect of artificial gravity that is induced by spinning. We don't have much experience with these ideas, because we can't simulate the various levels of artificial gravity. It is expected that the Coriolis effect caused by the spin might cause motion sickness and various undesirable effects that might be more detrimental on the organism than the benefit of the artificial gravity itself.

To reduce the Coriolis effect, you want to make the diameter of the spinning vessel as large as possible and the spin rate as slow as possible.

[shand]

completely forgot about that. the Coriolis effect would definately apply as the system was spinning up, but if you minimised the volume of the spinning bit (to control the air better) once it got up to speed would it still be significant. you want to minimise the velocity of the inner and outer edge of the rotating space to minimise the Coriolis effect - so yes wide and slow is the way to go. so now its a compromise given mass/volume of launch (tending to increase speed) and minimising the Coriolis effect (tending to decrease speed), so it will come down to which is the most constrating factor for the mission. for long haul interstellar flights you'd go big and slow, for ISS small experiments (why would you do them in space?!) you'd go small and fast.

[Rune]

as for lengths and rotation speed, its a compromise between the two. the longer the pivot, the faster the spin will have to be (is that the right way round), since there is very little cost in a faster rotation (once its got going) and a very real cost in getting said system up (volume and mass of launch). Ithink the answer will be, as short as possible given the required space. for example if you just wanted a looroom (gravity is useful on the bog) i'd have the pivot point cm's above the head.

Quite the opposite, for a given rotational period (rpm's), the "centrifugal force" (which is not a real force) is directly proportional to the turning radius. So the longer the "rope" is, the slower you turn for the same acceleration. In fact, at very short distances, the acceleration may become significantly different between your head and toes, so that would feel incredibly weird. Plus coriolis would become more significant, relatively speaking.

Still, the energy contained in the system would be the same for the same acceleration and mass, so the length would not matter in the energy requirements to spin it up. Only a longer rope would be heavier, so it would matter in real life. For a practical number, around 50m radius would be OK (longer even better), but forget about centrifuges ~10m in diameter, unless you just want a small fraction of a G, or you just use them as beds. Studies seem to indicate somewhere between 6 and 10 rpm humans get sick (as in motion sickness sick) due to coriolis effects.

[K^2]

One of the fundamental principles of General Relativity is that you cannot distinguish acceleration from gravity. At least locally. What that means is that given a long enough tether, you can make it so that it's impossible for astronauts to tell whether they are in space, with gravity simulated by rotation, or the whole thing is sitting on the surface of the Earth.

Of course, "long enough tether" in practice is going to be prohibitively long. With short tether, there are going to be some obvious signs that the gravity is generated by rotation. Coriolis effect is the single biggest giveaway. In terms of human biology, so long as rotation is slower than 2RPM, none of these effects cause any health problems. That means that if you want to actually use this in space to generate Earth's gravity, tether has to allow for at least 220m from center of rotation. In other words, if counterweight has similar mass to the ship, you are looking at about quarter mile of tether. This is far from impossible, but it's not going to be cheap.

[Nikolai]

They actually tested this idea for creating artificial gravity on Gemini 11, tethering the spacecraft to its (Agena) docking target and thrusting sideways. They ended up creating about 150 millionths of a gee.

The funky thing about Coriolis forces is that you'd feel a stronger force going with the direction of the station's spin than you would sitting still, and the force you'd feel going against the direction of the station's spin would be less than sitting still. As noted, these effects would be minimized with a "long enough" turning radius, but it's interesting to contemplate what this means in terms of simple things like pouring drinks and urinal placement.

Not to mention that these Coriolis effects make people queasy in the stomach because they do weird things to the otoliths that tell our brains how our heads are oriented with respect to "gravity". A long-time station resident might be able to tell which direction is "spinward" and which direction is "anti-spinward" if you blindfolded her simply by turning her head from side to side.

[nyrath]

Using spin is the best way to generate gravity (since micro-black holes are in short supply). Spacecraft can spin around their roll axis, or either the pitch or yaw axis (the latter is called a "tumbling pigeon"). Or as the original poster said, separate the ship into two parts connected by a cable.

Why? Crew nausea.

Centrifugal gravity strength is related to the spin rate and the radius of spin (equation here: http://www.projectrho.com/public_html/rocket/artificialgrav.php )

If the spin rate is above 7.5 rotations per minute, the crew will become nauseated. With that as a limit, the only way to increase the strength of the centrifugal gravity is by increasing the spin radius. And the most low-mass way to do that is by splitting the spacecraft in two connected by cables.

[drakesdoom]

If you were worried about having to counter the forces of spinup on the rotating section you would only have to have two counter rotating sections with equal rotational inertia. This could be accomplished with either a mirrored gravity wheel shall we call it or a massive reaction wheel, though why bring up a chunk of steel for just that?

[Holo]

If you were worried about having to counter the forces of spinup on the rotating section you would only have to have two counter rotating sections with equal rotational inertia. This could be accomplished with either a mirrored gravity wheel shall we call it or a massive reaction wheel, though why bring up a chunk of steel for just that?

It would have to be 50m in diameter to supply a pleasant 1/3g without making everyone sick, which is expensive.

[Tommygun]

Someone posted this link the other day you might find useful.

http://www.artificial-gravity.com/sw/SpinCalc/