The Universe, who is fascinated by that?

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Awrrr
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#1658988 27-Oct-2016 13:15

When I was a kid feeding on science fiction, a standard fixture of stories was the big, revolving donut in the sky using centrifugal force to generate artificial gravity. Now I see yet another report on the problems for humans of prolonged zero-g, this one being a weakened spine. What I never seem to see is any serious work being done on artificial gravity. Can anyone outline to me, in friendly monosyllables, why so little seems to be happening in this area? If prolonged zero g really is such a problem, shouldn't any craft to Mars be designed to rotate on the way? Why doesn't the ISS have gravity in its design? Is this really in the too hard box?

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Fred99

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#1659013 27-Oct-2016 13:36

I think the problem with centrifugal design to create artificial gravity is that the structure would need to be quite large to keep rotational speed down, I've seen suggestions that they could do something with a long tether with living quarters swinging around and counterweight consisting of the engines, fuel etc.

Of course if they could come up with a method to sustain acceleration at ~ 10m/s^2, you'd get a constant ~1g "gravity" as you were speeding up, then turn the ship around and get a constant 1g as you're slowing down to land at your destination. Would be fine within the solar system, inter-stellar not so much, as after about a year at 1g acceleration you're getting close to the speed of light.

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#1659014 27-Oct-2016 13:37

Rikkitic:

When I was a kid feeding on science fiction, a standard fixture of stories was the big, revolving donut in the sky using centrifugal force to generate artificial gravity. Now I see yet another report on the problems for humans of prolonged zero-g, this one being a weakened spine. What I never seem to see is any serious work being done on artificial gravity. Can anyone outline to me, in friendly monosyllables, why so little seems to be happening in this area? If prolonged zero g really is such a problem, shouldn't any craft to Mars be designed to rotate on the way? Why doesn't the ISS have gravity in its design? Is this really in the too hard box?

LOL I don't know what to say ;p

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#1659017 27-Oct-2016 13:39

G-Force ≠ Gravity

Rikkitic

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#1659022 27-Oct-2016 13:45

joker97:

G-Force ≠ Gravity

Jeez, go easy. You surely know what I am referring to.

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Rikkitic

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#1659028 27-Oct-2016 13:49

Fred99:

I think the problem with centrifugal design to create artificial gravity is that the structure would need to be quite large to keep rotational speed down, I've seen suggestions that they could do something with a long tether with living quarters swinging around and counterweight consisting of the engines, fuel etc.

Of course if they could come up with a method to sustain acceleration at ~ 10m/s^2, you'd get a constant ~1g "gravity" as you were speeding up, then turn the ship around and get a constant 1g as you're slowing down to land at your destination. Would be fine within the solar system, inter-stellar not so much, as after about a year at 1g acceleration you're getting close to the speed of light.

I have also read stories that use constant acceleration, but I'm not sure how that would be fuelled with current technology.

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#1659106 27-Oct-2016 15:48

Rikkitic:

Fred99:

I think the problem with centrifugal design to create artificial gravity is that the structure would need to be quite large to keep rotational speed down, I've seen suggestions that they could do something with a long tether with living quarters swinging around and counterweight consisting of the engines, fuel etc.

Of course if they could come up with a method to sustain acceleration at ~ 10m/s^2, you'd get a constant ~1g "gravity" as you were speeding up, then turn the ship around and get a constant 1g as you're slowing down to land at your destination. Would be fine within the solar system, inter-stellar not so much, as after about a year at 1g acceleration you're getting close to the speed of light.

I have also read stories that use constant acceleration, but I'm not sure how that would be fuelled with current technology.

Not close.

Current rockets can only run for minutes.

They just aren't that efficient and use a lot of fuel.

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#1659128 27-Oct-2016 16:18

Rikkitic:

Fred99:

I think the problem with centrifugal design to create artificial gravity is that the structure would need to be quite large to keep rotational speed down, I've seen suggestions that they could do something with a long tether with living quarters swinging around and counterweight consisting of the engines, fuel etc.

Of course if they could come up with a method to sustain acceleration at ~ 10m/s^2, you'd get a constant ~1g "gravity" as you were speeding up, then turn the ship around and get a constant 1g as you're slowing down to land at your destination. Would be fine within the solar system, inter-stellar not so much, as after about a year at 1g acceleration you're getting close to the speed of light.

I have also read stories that use constant acceleration, but I'm not sure how that would be fuelled with current technology.

Constant acceleration will very quickly run out of puff as it reached maximum speed and cannot accelerate any more.

Gravity is a very weak force. My weight is due to Earths gravity. Even if you rotated something, it has no weight in space so you cannot create gravity. Aside from the teeny gravity that everything has. I suggest magnetism is the easiest way. Doc Martens Magna brand! (Suitable for magnetic floors only)

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#1659134 27-Oct-2016 16:34

Rikkitic:

joker97:

G-Force ≠ Gravity

Jeez, go easy. You surely know what I am referring to.

You are saying spin something to create gravity like you read on the internet. I have no idea how people come up with those ideas because it's not going to work. THose create g-forces.

Gravity is caused by .... hey you know what - nobody knows. So how you gonna create an artificial something that nobody understands?

Ok maybe you mean generate forces so that the muscles have something to work against - well that's not that hard. Stick them in a passive suit that has a background constant passive something for the muscles to work against - just need to ask the materials engineer to figure it out. Probably can't get a suit to work out every muscle though, only target certain ones.

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#1659137 27-Oct-2016 16:45

I honestly don't understand what you are going on about. Continuous centrifugal force has the same effect on the body as gravity. Fine, call it something else but the effect is the same and for this purpose that is what matters.

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#1659145 27-Oct-2016 16:54

oh i see what you mean by the spinning donuts - needs to be quite big i thought, to create the artificial gravity thing whatever it really is called. not sure how it'd work on an object like the ISS. it'd throw everything everywhere and make everyone puke everywhere probably without creating the gravity effect thingy. but don't quote me. just imagining all the barf.

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Fred99

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#1659167 27-Oct-2016 17:07

joker97:

Ok maybe you mean generate forces so that the muscles have something to work against - well that's not that hard. Stick them in a passive suit that has a background constant passive something for the muscles to work against - just need to ask the materials engineer to figure it out. Probably can't get a suit to work out every muscle though, only target certain ones.

I think there's more to than just that. IIRC the specific concern was bone (density) loss in the spine after time in micro-gravity conditions. Of course there will be muscle loss as well, some carefully designed exercise might help with that, but it's probably not going to help with bone density which is influenced by things like weight-bearing. A typical concern back on earth with bone density loss is fractures in the elderly, and loss of density when bone strength is needed to hold prosthesis like hips in place. In those cases there are medications with side effects such as biphosphonates which can help reduce/reverse bone density loss, but "use it or lose it" is the way to go in a healthy person - and has positive rather than negative side effects. (If you have a total hip replacement, then regular walking [weight-bearing] will tend to prolong life of the prosthesis by reducing the chance of detaching/breaking bone- while exercise like swimming or cycling - while beneficial is less so).

One of very many health related issues which are troubling for long duration space flight. Radiation is another main one.

Of course there's another practical problem - what happens if you're on a 2 year mission and get sick or injured which on earth would require specialist treatment/equipment, you've got no x-ray machine, no facility for anaesthetics, diagnosis, surgery, can't have an unlimited medical cabinet, some drugs don't store well, and even if there's a doctor on board, something that they can't do could easily crop up. Here's an example of a medical doctor ER surgeon, a remarkable story - and this happened when some help was able to be obtained (air-drop of supplies).

Fred99

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#1659174 27-Oct-2016 17:14

joker97:

oh i see what you mean by the spinning donuts - needs to be quite big i thought, to create the artificial gravity thing whatever it really is called. not sure how it'd work on an object like the ISS. it'd throw everything everywhere and make everyone puke everywhere probably without creating the gravity effect thingy. but don't quote me. just imagining all the barf.

Then the problem of keeping comms gear antennae, solar panels etc pointed in the right direction. People barfing in space wouldn't be very nice, but it's certainly happened anyway.

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#1659180 27-Oct-2016 17:18

Fred99:

joker97:

oh i see what you mean by the spinning donuts - needs to be quite big i thought, to create the artificial gravity thing whatever it really is called. not sure how it'd work on an object like the ISS. it'd throw everything everywhere and make everyone puke everywhere probably without creating the gravity effect thingy. but don't quote me. just imagining all the barf.

Then the problem of keeping comms gear antennae, solar panels etc pointed in the right direction.

One could build a death star

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#1659183 27-Oct-2016 17:21

The middle part of the flying saucer is always stationary with regard to antenna direction. I thought everyone knew that. NASA should look at employing the history channel as aeronautical design consultants. ; ).

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