Artificial gravity in long term space travel

[Yuri_Armstrong]

Obviously, a mission to mars will take a few months at least. Is it possible that the spacecraft going there will have one section spinning around enough to create aritifcial gravity on the same level that they will face on Mars? If so they could become acclimated to the martian gravity while on the trip, instead of recovering from a long period of zero g when they get to mars.

Centrifuges are commonly used in science fiction to protect space travellers from the health effects of long term zero g, but wouldn't the constant spinning make you dizzy and nauseous when you tried to get up and walk around?

 

[SteveCNC]

I am sure it could be done although the radius of the swing at floor level would have to be fairly large to not get dizzy I would think . I guess as long as the entire ship spun you wouldn't have to worry about creating air-seals that could handle rotation while maintaining pressure .

I always though that some type of constant ion propulsion (accelerating or braking) would be good for creating a weak artificial gravity and while it wouldn't help a lot for maintaining bone density it would provide enough gravity to be able to move around normally and even eat and cook in a semi normal manner because you would have a sense of up and down .

 

[sxjenks]

I haven’t done the sums but if you could sustain a burn for a reasonable proportion of the journey that would give you any noticeable fraction of 1G, transit time wouldn’t be an issue…

 

[scottb50]

I am sure it could be done although the radius of the swing at floor level would have to be fairly large to not get dizzy I would think . I guess as long as the entire ship spun you wouldn't have to worry about creating air-seals that could handle rotation while maintaining pressure .

I always though that some type of constant ion propulsion (accelerating or braking) would be good for creating a weak artificial gravity and while it wouldn't help a lot for maintaining bone density it would provide enough gravity to be able to move around normally and even eat and cook in a semi normal manner because you would have a sense of up and down .

I don't think ion engines can come close to the acceleration to simulate gravity, though it does make sense with getting to and from Mars or Earth.

 

[SteveCNC]

While I am certain you can't get even close to 1G acceleration however virtually any acceleration/deceleration would create an artificial gravity . It dosen't have to create much , just enough to get a sense of up and down and make objects fall toward the floor .

It would keep my cereal in the bowl while I ate .

 

[scottb50]

While I am certain you can't get even close to 1G acceleration however virtually any acceleration/deceleration would create an artificial gravity . It dosen't have to create much , just enough to get a sense of up and down and make objects fall toward the floor .

It would keep my cereal in the bowl while I ate .

Thrust is rated in the thousands of a G, I doubt that would keep your cereal from roaming.

 

[Yuri_Armstrong]

I am sure it could be done although the radius of the swing at floor level would have to be fairly large to not get dizzy I would think . I guess as long as the entire ship spun you wouldn't have to worry about creating air-seals that could handle rotation while maintaining pressure .

I always though that some type of constant ion propulsion (accelerating or braking) would be good for creating a weak artificial gravity and while it wouldn't help a lot for maintaining bone density it would provide enough gravity to be able to move around normally and even eat and cook in a semi normal manner because you would have a sense of up and down .

I don't think astronauts really have trouble with orientation and up and down and stuff like that. I think really the only purpose of artificial gravity is to keep the crew in decent health.

I'm not talking 1 G here, more like .30-.40 gs so the crew can become accustomed to Martian gravity. The spinning part of the ship would need to be big enough so the crew wouldn't become dizzy or nauseated. Is there an engineer here who could explain what would be necessary for this?

Also, is there another way to possibly create artificial gravity? The only other way I could think of would be building a huge space "globe" that the crew could live in, which generates a gravity field of its own. That idea is generally used for interstellar travel though, not interplanetary.

 

[SteveCNC]

I was thinking more about the psychological effects of being weightless on a long trip in space , the more "normal" you can feel the less you would be adversely effected . You are probably right that even with my personal design for a mars vehicle with 16 ion drives would only produce a small amount (maybe .05g at best) and since you couldn't carry enough fuel to run the main engine for very long it would be a pretty weightless trip .

 

[Polishguy]

The Mars Direct plan features tethering your habitation module to the spent final stage for the duration of the outbound flight, and then spinning it by the tether, using the spent stage as a counterweight. This can generate either 1G or 1/3G, depending on rate of rotation and length of tether (the longer the tether, the more G forces). This method is, unfortunately, impossible using constant-thrust drives like VASIMR, because the engine itself will be spinning and the direction of the engines changing constantly. Luckily, a realistic VASIMR mission would take 4 months, so the crew could just bite the bullet and get through it (like they do on ISS).

 

[uberhund]

Sadly, the title of this thread is a misnomer. There is no such thing as artificial gravity.

But I understand that this term is used to describe centrifugal effect (also incorrectly referred to as a "force," which it's not).

So if the question is whether the centrifugal effect within a spinning body can be used as a proxy for gravity, then the answer is absolutely not. At the very least, Coriolis effects and and engineering the plumbing of fluids will make this physically, medically, or economically impractical.

For this, and other reasons, long term space flight for intelligent life is not possible.

 

[Yuri_Armstrong]

Sadly, the title of this thread is a misnomer. There is no such thing as artificial gravity.

But I understand that this term is used to describe centrifugal effect (also incorrectly referred to as a "force," which it's not).

So if the question is whether the centrifugal effect within a spinning body can be used as a proxy for gravity, then the answer is absolutely not. At the very least, Coriolis effects and and engineering the plumbing of fluids will make this physically, medically, or economically impractical.

For this, and other reasons, long term space flight for intelligent life is not possible.

Could you elaborate on centrifugal effectse a bit more? I thought it was commonly thought that a large enough spinning object will create a small amount of gravity so the crew wouldn't become dizzy and nautious during the flight.

Also, this isn't the only method for long term space flight. There is the possibility of "world" ships that are large enough to create their own gravitational field. We couldn't do something like this right now but it's not impossible if you allow technology to progress.

 

[neutrino78x]

So if the question is whether the centrifugal effect within a spinning body can be used as a proxy for gravity, then the answer is absolutely not. At the very least, Coriolis effects and and engineering the plumbing of fluids will make this physically, medically, or economically impractical.

What are you talking about dude, this is established space engineering. You probably wouldn't do it with a little space capsule (although there is Zubrin's idea to use the spent thruster stage and a long tether), but there is no reason you couldn't have a large, slowly spinning torus, in which 1 G is felt along the edges.

See the Stanford Torus. The world renowned Stanford University, located here in Silicon Valley (part of the san francisco bay area), did a study on it in 1975.

They tried something similar on Skylab

During the first mission. the astronauts proved they could have a "track meet'' around the lockers in the upper compartment of the workshop. By accelerating slowly, they could develop enough centrifugal force to hold themselves against the locker doors, permitting them gradually to stand up and run. The force, as it turned out. was about the same magnitude as the gravitational force the Apollo crewmen felt as they walked on the Moon. In order to accelerate around the lockers, the men pushed off from the edges of the locker doors. A 150-pound astronaut induced a very slow counter-rotation of the 200 000-pound Skylab. This reaction of the vehicle, although small. was detectable by the precisely pointed solar telescopes. While one crewman was performing solar experiments requiring fine pointing. it was necessary for the other crewman to avoid pushing off the space station walls or floors with much force. They found that they could move around very effectively with light pushes so that their motions seldom affected such experiments.

See this page.

See also the Artificial Gravity section in Atomic Rocket, a page which I highly recommend to users on this site.


--Brian

 

[neutrino78x]

According to the Space Math site, if you want 1 RPM, and 1 G, the radius of the spacecraft would have to be 894 meters.

--Brian

 

[James_Bull]

Sadly, the title of this thread is a misnomer. There is no such thing as artificial gravity.

But I understand that this term is used to describe centrifugal effect (also incorrectly referred to as a "force," which it's not).

So if the question is whether the centrifugal effect within a spinning body can be used as a proxy for gravity, then the answer is absolutely not. At the very least, Coriolis effects and and engineering the plumbing of fluids will make this physically, medically, or economically impractical.

For this, and other reasons, long term space flight for intelligent life is not possible.

Artificial gravity is the emulation of the effect of gravity in outer space. And yes, it is very possible! The coriolis effect isn't noticable at under 2.5 to 2RPM rotation speed. They say with accimitisation humans can live comfortably at higher spin rates too.
No, actually I guess you're right. What was the genius Werner Von Braun thinking?! He obviously didn't have you around to tell set him right... :lol:

(Also, I'll stand on an escalator if I like, thank you very much!!)

 

[uberhund]

Good stuff, guys. Where to start. Let's start here:

Yuri writes:
1. A large enough spinning object will create a small amount of gravity.
No. Gravity is a property of matter. Spinning is not necessary for matter to possess gravity. It's there whether it spins or not. In fact, spinning an object will actually diminish the effect of gravity at right angles to the spin. For example, an object weights less at the equator of Earth than it does at the poles, owing to a couple of issues relating to the spin.
2. Ships that are large enough to create their own gravitational field [is] not impossible if you allow technology to progress.
The ship would have to have the mass of the Earth to possess 1G of gravity. Using something the mass of Earth as a space ship makes no economic sense.

Nutrino78 writes:
There is no reason you couldn't have a large, slowly spinning torus, in which 1 G is felt along the edges.
There's every reason why a spinning torus will not work for long term space travel. Here's just one: Consider the acceleration forces necessary to propel the torus to a meaningful velocity. Think about it - what will accelerations greater than zeroG along the rotational axis do to the right-angle centrifugal effects at the rim within the torus?

James_Bull writes:
1. No, actually I guess you're right. What was the genius Werner Von Braun thinking?! He obviously didn't have you around to tell set him right...
As I recall, vonBraun's rotating torus proposal was for a space *station* not for space *travel.* In any event, vonBraun admitted to being wrong on more than one occasion when non-geniuses were proven correct. The Earth-orbit-rendezvous versus Lunar-orbit-rendezvous debate comes to mind immediately as one example. It doesn't take someone of his intellect to suspect he would have chosen to revisit many of his convictions and decisions had he a chance to do it all over again.

2. Also, I'll stand on an escalator if I like, thank you very much!!
But of course. That's the benefit of living in a free society. I'm just asking you to like being courteous to others, that's all.

 

[Yuri_Armstrong]

Good stuff, guys. Where to start. Let's start here:

Yuri writes:
2. Ships that are large enough to create their own gravitational field [is] not impossible if you allow technology to progress.
The ship would have to have the mass of the Earth to possess 1G of gravity. Using something the mass of Earth as a space ship makes no economic sense.

Let's say then that eventually we colonize the 8 planets of the solar system and have the technology to access resources from all of its moons and asteroids. If that were the case then you could make a ship with half the Earth's mass, which would be good enough for the astronauts to land on a world with a gravity probably not higher than 1 G. So yes it would be very expensive but it's not impossible, which is what you were saying earlier:

For this, and other reasons, long term space flight for intelligent life is not possible.

 

[MeteorWayne]

ROFL, a ship with half the earth's mass???

That's much more massive than the Moon, Mercury, Mars, and anything else in the solar system except Venus, and the Gas and Ice Giants. In fact, it's more than everything in the asteroid belt combined.

 

[Yuri_Armstrong]

ROFL, a ship with half the earth's mass???

That's much more massive than the Moon, Mercury, Mars, and anything else in the solar system except Venus, and the Gas and Ice Giants. In fact, it's more than everything in the asteroid belt combined.

Yeah, you have to go to some extreme lengths if you want to do inter-stellar travel. I'm afraid that this is probably the best way to do it though, unless we invent some sort of artificial gravity machine. Wasn't somebody in the unexplained section talking about how he could make one?

 

[SteveCNC]

I'd have to say anti-gravity/artificial gravity would be far more likely then an object with half the mass of earth being built , I can't even begin to imagine how complicated it's structure would have to be to even have that much mass in a structure without it crushing itself . Let alone try to move it

 

[kelvinzero]

What are you talking about dude, this is established space engineering.

Why should established space engineering stand in the way of absolute self confidence?

 

[neutrino78x]

Good stuff, guys. Where to start. Let's start here:

Yuri writes:
1. A large enough spinning object will create a small amount of gravity.
No. Gravity is a property of matter. Spinning is not necessary for matter to possess gravity.

Dude, he was clearly referring to "the acceleration of gravity", that is to say, the result of gravitation, not gravitation itself. In a spinning spaceship, centrifugal force imposes an acceleration equivalent to that of gravity on the surface of the Earth.

There's every reason why a spinning torus will not work for long term space travel. Here's just one: Consider the acceleration forces necessary to propel the torus to a meaningful velocity. Think about it - what will accelerations greater than zeroG along the rotational axis do to the right-angle centrifugal effects at the rim within the torus?

Obviously, while the ship's main drive is in operation, the torus would be stationary, and people would be strapped into their seats, or liquid acceleration beds, or whatever.

Artificial gravity, that is to say, Centrifugal force, is for when the ship is in inertial travel ("coasting").

Let us say a large starship, able to produce 1 G of artificial gravity via centrifugal force, wishes to go to another star. This would involve a period of sustained acceleration.

So, you spin down the torus, activate the main rocket, accelerate for a while, turn off the main rocket. Now you are coasting, that is to say, you are in a state of inertial motion, and now you would spin up the torus.

--Brian

 

[scottb50]

For this, and other reasons, long term space flight for intelligent life is not possible.

It could easily be done with simple Modules, you could even have different gravity levels reachable by elevators with sound effects. Identical Modules, used as every component in the system, each Module consists of two Segments locked together over a filament wound Tube, Tubes vary in winding material, but are generally interchangeable, stainless steel windings are used on Modules carrying Hydrogen as an example.

Segments are multiple iteration of the same thing, everything is a mirror image, mating to another Segment. Smaller, but identical, Docking Adapters at the ends on a Segment allow docking to any other Docking Adapter, of the same diameter. By modifying the basic end adapter, either open or closed you could have multiple Segment Modules, though two Segment Modules will be Standard three or four have practical uses in First and Second Stages, and some orbital applications, though I stick to single Modules for added safety in numbers.

So basically you have a single piece, milled and drilled, ring of metal that gets an outer resin and composite covering, identical to every other pieces made, except, the design of the ring stays the same, only the diameter changes. A standard Modules uses two identical Segments mated over a single piece Tube, Each Segment has two end Adapters, one open and one closed, add an Adapter open on both ends and you have a longer Module, four smaller Adapters in the center, allow hatches for human transfer, structural integrity or any other use by switching the vault type hatch for one fitted for other uses.

Modules can be upper stage propellant tanks and go on to be Mars transfer Modules, or added space in a Station.

 

[Yuri_Armstrong]

Well this thread is about the multiple ways of producing gravity for long term spaceflight. Centrifugal effect is one, but the only other alternative is to have an object large enough to produce its own gravity field. Yes it would be very expensive and would take a while to do but I'd like to see some ideas about its possible construction, thrust methods, population, size, etc. It does sound unrealistic but a few hundred years ago people thought flying was impossible and that all transportation required animals, now we've got a crewed space station and multiple manned space vehicles.

Also, I seem to recall someone talking about a gravity machine in the unexplained forum. Is it possible to make such a thing?

 

[SteveCNC]

It seems to me uberhund your attempting to push your literal translation against an abstract thought which rarely works out as a positive and generally is purely argumentative . The term "artificial gravity" is usually used to describe any force or energy other than gravity itself that produces a like effect , hence the word artificial . It seems like too often people "skim" through a post and assume they fully comprehend what was said and then feel the need to comment on something they didn't understand as if they did .

I will admit that when people post their ideas it can be a struggle at times to fully understand the idea they are trying to convey , I have no doubt I have been mis-understood several times as a result of the same thing , but I try not to get condescending even when things seem way out there to me .

I'm not entirely clear as to why such a ship (one with a centrifical artificial gravity) wouldn't be able to run a low thrust set of motors at the same time as the ship spun . With gimbled nozzle's they could even help maintain the correct spin you would just need some way to maintain balance which wouldn't be very difficult . Of course anyone riding in the engine section would not like it much if they had to spin also but I'm sure that could be overcome as well by making an internal counter spin compartment . you would be virtually weightless in that section but I'm sure there would be intervals where spin was stopped to change things around .

Just so you understand the counterspin section idea , it would be basically a cage that counterspun within the center section of the ship . It would have its own internal power supply or could be laser fed power from the main ships power and is linked by wireless network back to the ship so no cables or plumbing have to spin , the atmosphere is maintained by the ship and this is just a cage within the ship that is counter spinning so it won't make the people riding there dizzy . I guess the spin could be reduced to work on any engine's that may need it or power/life support systems .

 

[uberhund]

My apologies, Yuri - I don't mean to be dragging the dialog away from your original theme. I'll try to make up for my digression in another post.

Permit me first though, this response to Neutrino78 and SteveCNC:
Obviously, while the ship's main drive is in operation, the torus would be stationary, and people would be strapped into their seats, or liquid acceleration beds, or whatever.

Hm. That's not so obvious to me. For one thing, it would take years of constant acceleration to achieve any practical velocity for useful space travel. That's a long time to be strapped down to a seat. Accelerating at a faster rate would destroy the torus or crush the intelligent inhabitants. Remember that the extents of this torus being described are *way* out there. The torque forces (in the Newtonian sense of the word) from the central axis would be tremendous. Breaking the torus or being crushed inside the torus would take all the fun out of space travel.

As an aside, I've enjoyed trying to imagine the kind of seat to which one would be strapped in your scenario. On some level, the inside walls of this crazy torus idea would have to, what, rotate is some weird way to stay orthogonal to the acceleration vector de jour? It's an intriguing idea, but can the insides of a torus be physically made to rotate around the axis of the circumference? Probably not. At least, not in a way practical for long term space travel.

I stand by my original post- though it's fun to think about, long term space travel for intelligent life will never be economically practical, let alone the generation of gravity through means other than accumulating mass. But it doesn't matter, because there's no place economically interesting for intelligent life to to travel to anyway. Let's stick with probes and robots. They don't need gravity.