### Author Topic: Artificial gravity inside an inflatable module  (Read 12810 times)

#### scienceguy

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##### Artificial gravity inside an inflatable module
« on: 04/04/2016 05:50 PM »
So a major problem with a spinning section on a spacecraft is that you would have joints that are moving that would need to be sealed. What if you had a large inflatable spacecraft and put in the spinning structure after it has inflated in orbit? Kind of like a Bigelow module but bigger to contain the spinning structure.

e^(pi*i) = -1

#### sevenperforce

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##### Re: Artificial gravity inside an inflatable module
« Reply #1 on: 04/04/2016 06:37 PM »
Whatever gas you used to inflate the thing would produce considerable drag on the rotating portions, slowing them immediately.

And why do you want a spaceship-inside-a-spaceship anyway? If they aren't coupled in anyway then they will drift independently and the spinning inside module will impact the outer wall pretty quickly. That won't be good.

#### scienceguy

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##### Re: Artificial gravity inside an inflatable module
« Reply #2 on: 04/04/2016 07:12 PM »
Whatever gas you used to inflate the thing would produce considerable drag on the rotating portions, slowing them immediately.

And why do you want a spaceship-inside-a-spaceship anyway? If they aren't coupled in anyway then they will drift independently and the spinning inside module will impact the outer wall pretty quickly. That won't be good.

Good point about the drag from the gas inside. I hadn't thought of that.

The inner spaceship would be coupled to the outer spaceship. I just had not drawn the structure inside holding them together.
e^(pi*i) = -1

#### vulture4

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##### Re: Artificial gravity inside an inflatable module
« Reply #3 on: 04/04/2016 07:25 PM »
Over the years the requirement for artificial gravity, from a medical perspective, has declined, with several flights of a year or more in weightlessness. Conversely, there has not been much improvement in immediate transition from the rotating/gravity environment to the weightless one; it still results in disorientation and motion sickness. In combination there is no clear requirement at this point for a large centrifuge.

#### IRobot

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##### Re: Artificial gravity inside an inflatable module
« Reply #4 on: 04/04/2016 08:50 PM »
Conversely, there has not been much improvement in immediate transition from the rotating/gravity environment to the weightless one; it still results in disorientation and motion sickness. In combination there is no clear requirement at this point for a large centrifuge.
I could argue that without a test centrifuge, there is no way to improve the situation.

#### JasonAW3

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##### Re: Artificial gravity inside an inflatable module
« Reply #5 on: 04/04/2016 09:11 PM »
Whatever gas you used to inflate the thing would produce considerable drag on the rotating portions, slowing them immediately.

And why do you want a spaceship-inside-a-spaceship anyway? If they aren't coupled in anyway then they will drift independently and the spinning inside module will impact the outer wall pretty quickly. That won't be good.

Good point about the drag from the gas inside. I hadn't thought of that.

The inner spaceship would be coupled to the outer spaceship. I just had not drawn the structure inside holding them together.

Actually, you might be better off with a more,"loose" structure within a structure.

The inflatable would be you're actual pressure structure while the rotating section, (I would recommend a multilevel wheel type structure) would actually be more of a framework with inner panels.

Adding curving panels between the wheel structure and the outer pressure vessel, would allow simplified re-circulation of atmosphere, allowing fresh air to be brought down to the lower levels of the structure while pumping the CO2 upwards to the ECS.

This would be accomplished with a "Spindle" type structure established at both ends of the centrifuge structure and attached to the outer structure with a set of magnetic bearings, allowing for a "Air Bearing" at the center of rotation.  You would also use another pair of structures, with sufficient mass, also using air bearings, to counter the rotational issues that would crop up due to the rotation of the inner centrifuge.

These"Fly wheel" structures would be needed to prevent precesional issues with space craft, which would both cause a slow but inevitable course change due to gyroscopic forces created by the centrifuge structure.  Otherwise, this could be avoided using two counter rotating centrifuges of equal mass, in linear succession.
My God!  It's full of universes!

#### Impaler

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##### Re: Artificial gravity inside an inflatable module
« Reply #6 on: 04/04/2016 10:45 PM »
I've thought extensively about how to do just this in a Bigelow style inflatable module.

First off you use the axial core of the module where Bigelow currently puts all the ECLSS systems and put 3 rotational joints into it, one on each end one in the middle such that 2 segments can freely rotate within the enclosed volume.  The exterior docking points of the module remain fixed relative to the outer skin.

At the middle of the module where the two rotating segments meet a motor and brake are placed such that the two segments can be driven in counter rotation so the whole module dose not experience any torque.  It also allows a simple and controlled way to slow down the system without exerting any torque on the docking points of the module as the two segments slow down equally as the brake pad between them is applied.  Electrical and fluid couplings across rotating joints are difficult but still possible and would likely be used.

Around the two central core segments are a set of telescoping carbon rods and curved deck plates.  These are folded around the core and under the outer skin during launch.  Once in orbit the skin is first expanded then the segments are rotated to expand the decking by centripetal forces, the carbon rods are equipped with locking joints which lock them to their extended positions so structure becomes fixed once expanded.  The outer most deck plates will be a few inches from the inner surface of the module and will never touch it.

The final habitation step is to install safety walls in each rotating segments end where it faces it's counter rotating partner as the high relative speed and vertical supports would make it dangerous to pass between them.  Personnel will naturally use a hollow passage in the zero-gravity core to transition between the two segments as well as to enter or leave the module at the axial docking ports.

#### AlanSE

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##### Re: Artificial gravity inside an inflatable module
« Reply #7 on: 04/05/2016 02:34 AM »
Around the two central core segments are a set of telescoping carbon rods and curved deck plates.  These are folded around the core and under the outer skin during launch.  Once in orbit the skin is first expanded then the segments are rotated to expand the decking by centripetal forces, the carbon rods are equipped with locking joints which lock them to their extended positions so structure becomes fixed once expanded.  The outer most deck plates will be a few inches from the inner surface of the module and will never touch it.

For the purpose of articulating a reasonable vision - you did as good of a job as anyone of us could hope to do. But I want to dwell on the specificity of the wording a little bit. Typically, when I hear "telescoping", I think of cylindrical segments that slide in the axial direction relative to each other, which is illustrated by a literal telescope lens. What you describe is more like a saw-tooth shape that expands and locks into a true circle.

The largest heavy-lift versions of Bigelow modules would be of sufficient size to do this. Let me point out, however, that this obviously only makes sense for a multi-module station (with a full module dedicated to the centrifuges). This only has a niche if the station has many astronauts only visit the module in rotation. From the (currently optimistic) research results on the ISS, we have every reason to believe that periodic stressing of our bodies can essentially halt bone loss. Speculatively, a centrifuge would accomplish the same in less time and with less active effort from the astronauts.

I see this as establishing the break-even scale for artificial gravity. When the modules are large enough to accommodate them, and the staff is specialized enough to get value out of them, then of course we will use centrifuges in space stations. That doesn't detract from the value of micro-gravity - its main role will be to allow us to have longer stays in micro-gravity.

#### sanman

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##### Re: Artificial gravity inside an inflatable module
« Reply #8 on: 04/06/2016 04:51 AM »
Whatever gas you used to inflate the thing would produce considerable drag on the rotating portions, slowing them immediately.

And why do you want a spaceship-inside-a-spaceship anyway? If they aren't coupled in anyway then they will drift independently and the spinning inside module will impact the outer wall pretty quickly. That won't be good.

Wouldn't the initial drag reciprocally result in rotational acceleration of the boundary layer interface between the inner hull surface and the contained gas? So eventually, your gas would sort of be rotating in sync with your hull, rather than inflicting perpetual drag.

#### sevenperforce

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##### Re: Artificial gravity inside an inflatable module
« Reply #9 on: 04/06/2016 05:18 AM »
Whatever gas you used to inflate the thing would produce considerable drag on the rotating portions, slowing them immediately.

And why do you want a spaceship-inside-a-spaceship anyway? If they aren't coupled in anyway then they will drift independently and the spinning inside module will impact the outer wall pretty quickly. That won't be good.

Wouldn't the initial drag reciprocally result in rotational acceleration of the boundary layer interface between the inner hull surface and the contained gas? So eventually, your gas would sort of be rotating in sync with your hull, rather than inflicting perpetual drag.
Yes, but that will make your entire ship rotate eventually. If that is okay, then why not rotate the whole ship to begin with?

#### Impaler

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##### Re: Artificial gravity inside an inflatable module
« Reply #10 on: 04/06/2016 06:01 AM »
Around the two central core segments are a set of telescoping carbon rods and curved deck plates.  These are folded around the core and under the outer skin during launch.  Once in orbit the skin is first expanded then the segments are rotated to expand the decking by centripetal forces, the carbon rods are equipped with locking joints which lock them to their extended positions so structure becomes fixed once expanded.  The outer most deck plates will be a few inches from the inner surface of the module and will never touch it.

For the purpose of articulating a reasonable vision - you did as good of a job as anyone of us could hope to do. But I want to dwell on the specificity of the wording a little bit. Typically, when I hear "telescoping", I think of cylindrical segments that slide in the axial direction relative to each other, which is illustrated by a literal telescope lens. What you describe is more like a saw-tooth shape that expands and locks into a true circle.

The largest heavy-lift versions of Bigelow modules would be of sufficient size to do this. Let me point out, however, that this obviously only makes sense for a multi-module station (with a full module dedicated to the centrifuges). This only has a niche if the station has many astronauts only visit the module in rotation. From the (currently optimistic) research results on the ISS, we have every reason to believe that periodic stressing of our bodies can essentially halt bone loss. Speculatively, a centrifuge would accomplish the same in less time and with less active effort from the astronauts.

I see this as establishing the break-even scale for artificial gravity. When the modules are large enough to accommodate them, and the staff is specialized enough to get value out of them, then of course we will use centrifuges in space stations. That doesn't detract from the value of micro-gravity - its main role will be to allow us to have longer stays in micro-gravity.

The deck plates are indeed going to need to be in a overlapping saw-tooth configuration before expanding into a cylinder.  The telescoping rods would be the spokes connecting the decking to the central core, these need to compressed, folded or telescoped in some way to simply make room for the decking to be able to fold-up.

And yes I agree the largest size Bigelow module concepts 'Olympus' which aimed to max out the SLS launch capacity would have enough volume to get 2 rings of decks, a higher gravity deck on the outer edge, a low gravity deck above that and a zero-G core tunnel.  The use of such a module would certainly be on interplanetary transits, a LEO station doesn't need or want artificial gravity.

#### A_M_Swallow

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##### Re: Artificial gravity inside an inflatable module
« Reply #11 on: 04/06/2016 09:02 AM »
Whatever gas you used to inflate the thing would produce considerable drag on the rotating portions, slowing them immediately.

And why do you want a spaceship-inside-a-spaceship anyway? If they aren't coupled in anyway then they will drift independently and the spinning inside module will impact the outer wall pretty quickly. That won't be good.

Wouldn't the initial drag reciprocally result in rotational acceleration of the boundary layer interface between the inner hull surface and the contained gas? So eventually, your gas would sort of be rotating in sync with your hull, rather than inflicting perpetual drag.
Yes, but that will make your entire ship rotate eventually. If that is okay, then why not rotate the whole ship to begin with?

Put couplings at the front and back. Rotate the outside of the spacestation in one direction and the inside in the opposite direction. This permits use of electric motors rather than rocket fuel.

#### MIKKELH

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##### Re: Artificial gravity inside an inflatable module
« Reply #12 on: 04/06/2016 09:53 AM »
You are going to have a lot of sick people during the first few days of their respective deployments, if you want any sort of significant artificial gravity. People prone to motion sickness might not even be able to adapt at all.
Also, you will need to plan for reinforcing your shell in order to accomodate the additional hoop stress resulting from the centrifugal force.

#### QuantumG

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##### Re: Artificial gravity inside an inflatable module
« Reply #13 on: 04/06/2016 11:21 AM »
Human spaceflight is basically just LARPing now.

#### MIKKELH

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##### Re: Artificial gravity inside an inflatable module
« Reply #14 on: 04/06/2016 04:11 PM »
Quite true, but as a rule the effects tend to be less severe, it takes a shorter time for most subjects to adapt, and there are fewer cases of people so prone that they do not adapt.

#### Vultur

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##### Re: Artificial gravity inside an inflatable module
« Reply #15 on: 04/09/2016 06:05 PM »
Over the years the requirement for artificial gravity, from a medical perspective, has declined, with several flights of a year or more in weightlessness.

Also, zero-g allows you to make better use of limited space.

I really don't think artificial gravity is a good idea except for really long term, large things like space habitats/O' Neill colonies.

#### stoker5432

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##### Re: Artificial gravity inside an inflatable module
« Reply #16 on: 04/10/2016 03:13 AM »
Conversely, there has not been much improvement in immediate transition from the rotating/gravity environment to the weightless one; it still results in disorientation and motion sickness. In combination there is no clear requirement at this point for a large centrifuge.
I could argue that without a test centrifuge, there is no way to improve the situation.

Why does this have to be argued at all? This thread is about an engineering solution for AG not whether people think it's necessary or not. Just a good way to derail the thread. I don't know why the moderators put up with it.

#### AlanSE

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##### Re: Artificial gravity inside an inflatable module
« Reply #17 on: 04/10/2016 02:21 PM »
And yes I agree the largest size Bigelow module concepts 'Olympus' which aimed to max out the SLS launch capacity would have enough volume to get 2 rings of decks, a higher gravity deck on the outer edge, a low gravity deck above that and a zero-G core tunnel.  The use of such a module would certainly be on interplanetary transits, a LEO station doesn't need or want artificial gravity.

The future economics of manned spaceflight is victim to some of the worst sorts of speculation out there. How we we know that exploratory missions are even important in a proportional sense? For every 1 person you send to Mars, you could probably send 1,000 different people to trips in LEO with a mature launch economy. The economies of scale that are vital to making manned spaceflight a real economic sector are completely beyond of the horizon of imagination for Mars. Besides, if we are sure about using artificial gravity for Mars trips, then what, exactly, is the goal of the ISS?

I also can't accept that zero-g sickness is something outside of our control. It is very likely that therapy specifically designed to combat these effects could open up space to the fraction of our population who either could never otherwise adapt to zero-g conditions, or would find it too uncomfortable to tolerate. Considering centrifuges in moderation makes a heck of a lot more sense than any other conception of it. The Coriolis effects don't even exist unless your body is in motion. Many people would be content to stand in place and watch a sitcoms for an hour every day, particularly if this would reduce their discomfort and keep their bones healthy. There is much that we don't know about how the human body will behave in these circumstances.

#### Ibn Firnas

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##### Re: Artificial gravity inside an inflatable module
« Reply #18 on: 04/11/2016 01:17 AM »
If the Olimpus comes to be a reality we could actually aim for a true ring space station . Requiring just x13 BA 2100 and around 20+ SLS launches it is not that far from the ISS cummulative cost. It would have a radius of around 53 meters requiring a gentle angular velocity of 3rpm to provide 0.5G. Doable if you ask me.

Edit: This was proposed by Phil Wilson
« Last Edit: 04/11/2016 01:20 AM by Ibn Firnas »

#### Impaler

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##### Re: Artificial gravity inside an inflatable module
« Reply #19 on: 04/11/2016 07:23 AM »
That's not really what the threads about, the old pin-wheel station idea is well understood (conceptually) but rotation inside of inflatables is not.

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