### Author Topic: Realistic, near-term, rotating Space Station  (Read 603394 times)

#### LarryCanuck

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##### Re: Realistic, near-term, rotating Space Station
« Reply #3080 on: 01/25/2023 01:58 am »
Just to bring back some old ideas from this thread.  This a taxi type concept from 2019.  Time flies...
Noice! The stacked floors (about 16m dia.??) would have incrementally-increasing AG from perhaps Mars level to perhaps somewhat beyond Earth-level. Would the ports spin the taxi up, or would the taxi spin to match the station and port? Best regards!

#### Coastal Ron

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##### Re: Realistic, near-term, rotating Space Station
« Reply #3081 on: 01/25/2023 02:19 am »
Just to bring back some old ideas from this thread.  This a taxi type concept from 2019.  Time flies...
Noice! The stacked floors (about 16m dia.??) would have incrementally-increasing AG from perhaps Mars level to perhaps somewhat beyond Earth-level. Would the ports spin the taxi up, or would the taxi spin to match the station and port? Best regards!

That shape is referred to as a "dumbbell", whereas some designs are just the same diameter their whole length, and they are referred to as a "baton". Or stick.

The advantage of these types of designs is that they provide multiple levels of artificial gravity. The disadvantage would be that each level of artificial gravity is quite small, so they will more likely just be used for artificial gravity research, or applications where the change in gravity is not a big deal, but having some gravity is desired.

As for ports rotating, having such a system would offer some advantage, but they add their own amount of complexity (i.e. strength of the rotating structure, can it be made air tight, etc.).

Oh, and are you familiar with the "intermediate axis theorem" (aka "tennis racket theorem")? This describes how objects in space don't just rotate in two dimensions, but in three dimensions, so docking onto the middle of a dumbbell or baton station (and undocking) has to be done taking into account what the intermediate axis is.
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

#### lamontagne

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##### Re: Realistic, near-term, rotating Space Station
« Reply #3082 on: 01/25/2023 02:57 am »
As promised, Earth from a space station at 1 rpm

and 3 rpm

Definitively a case of a typical driving conversation:
-Look at that love!
-What, where?

At least in this case it comes back pretty fast
« Last Edit: 01/25/2023 03:10 am by lamontagne »

#### lamontagne

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##### Re: Realistic, near-term, rotating Space Station
« Reply #3083 on: 01/25/2023 02:59 am »
Just to bring back some old ideas from this thread.  This a taxi type concept from 2019.  Time flies...
Noice! The stacked floors (about 16m dia.??) would have incrementally-increasing AG from perhaps Mars level to perhaps somewhat beyond Earth-level. Would the ports spin the taxi up, or would the taxi spin to match the station and port? Best regards!
This is spinning taxi design, as simple as possible.

#### Coastal Ron

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##### Re: Realistic, near-term, rotating Space Station
« Reply #3084 on: 01/25/2023 03:40 am »
As promised, Earth from a space station at 1 rpm

and 3 rpm

NICE! Now we know what it looks likes.

Quote
Definitively a case of a typical driving conversation:
-Look at that love!
-What, where?

At least in this case it comes back pretty fast

Well, in LEO you are moving over the Earth pretty quickly. The ISS orbits the Earth every 90 minutes, so for every revolution of the station in LEO your frame of reference on Earth moves about 92 miles (148 km). Plus if you wait an orbit, your next orbit may be over a different spot on Earth...

Anyone think this will be a high value activity for tourists?
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

#### Asteroza

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##### Re: Realistic, near-term, rotating Space Station
« Reply #3085 on: 01/25/2023 03:40 am »
As promised, Earth from a space station at 1 rpm

and 3 rpm

Definitively a case of a typical driving conversation:
-Look at that love!
-What, where?

At least in this case it comes back pretty fast

What would it look like if the rotation axis was pointed nadir though, rather than flight vector?

#### lamontagne

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##### Re: Realistic, near-term, rotating Space Station
« Reply #3086 on: 01/25/2023 03:44 am »
As promised, Earth from a space station at 1 rpm

and 3 rpm

NICE! Now we know what it looks likes.

Quote
Definitively a case of a typical driving conversation:
-Look at that love!
-What, where?

At least in this case it comes back pretty fast

Well, in LEO you are moving over the Earth pretty quickly. The ISS orbits the Earth every 90 minutes, so for every revolution of the station in LEO your frame of reference on Earth moves about 92 miles (148 km). Plus if you wait an orbit, your next orbit may be over a different spot on Earth...

Anyone think this will be a high value activity for tourists?
1 rpm definitively.  3 rpm, perhaps not so much.  The bigger the window, the higher the value.

#### mikelepage

##### Re: Realistic, near-term, rotating Space Station
« Reply #3087 on: 01/25/2023 09:28 am »
As promised, Earth from a space station at 1 rpm

and 3 rpm

NICE! Now we know what it looks likes.

Quote
Definitively a case of a typical driving conversation:
-Look at that love!
-What, where?

At least in this case it comes back pretty fast

Well, in LEO you are moving over the Earth pretty quickly. The ISS orbits the Earth every 90 minutes, so for every revolution of the station in LEO your frame of reference on Earth moves about 92 miles (148 km). Plus if you wait an orbit, your next orbit may be over a different spot on Earth...

Anyone think this will be a high value activity for tourists?
1 rpm definitively.  3 rpm, perhaps not so much.  The bigger the window, the higher the value.

I think there have to be windows, but my preferred arrangement is a cupola type module at the centre of rotation, within which there is a "cage" that counter rotates such that experiments (and people) attached to it experience zero gravity.

I mocked up a 3rpm cupola rotation - assuming one is stationary within the cupola.

#### JohnFornaro

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##### Re: Realistic, near-term, rotating Space Station
« Reply #3088 on: 01/25/2023 10:12 am »
I see no point in berthing a 1200mT Starship to any station.  I expect a fueling station to be a separate element, and the Starship should reach a LEO station pretty much empty, except for 50 or so mT of landing fuel in a spherical tank.
Having many thousand mT of fuel on a station itself to fuel visiting Starships seems like a bad plan.

I think you're adding another layer of complexity.

The analogy here is the car and the gas station.  You drive the car up to the station and fill it up.  You don't park away from the station, fill up a gas can, and walk over to the car.
Sometimes I just flat out don't get it.

#### JohnFornaro

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##### Re: Realistic, near-term, rotating Space Station
« Reply #3089 on: 01/25/2023 10:19 am »
I took a few hours this morning to create a Shared Google drive.

Well done.

But.

The format changed overnight.  Yesterday, it looked like I had the ability to change my profile pic and upload files.  Today, it just shows a list of station and such, and there is only a "download all" button.
Sometimes I just flat out don't get it.

#### JohnFornaro

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##### Re: Realistic, near-term, rotating Space Station
« Reply #3090 on: 01/25/2023 10:22 am »
An algorithm do do this:

Big whoop.  So can I.
Sometimes I just flat out don't get it.

#### JohnFornaro

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##### Re: Realistic, near-term, rotating Space Station
« Reply #3091 on: 01/25/2023 10:29 am »
As promised, Earth from a space station at 1 rpm

Sweet.

Now do one from EML-1, when the Sun is behind the station, at 1.0 and 1.4 rpm.

You caould also do it from EML-1, when the Earth is behind the station, and hte station is lookingat the night "sky".  Be sure to include constellations.

Are you rethinking 3 rpm?
Sometimes I just flat out don't get it.

#### Lampyridae

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##### Re: Realistic, near-term, rotating Space Station
« Reply #3092 on: 01/25/2023 11:21 am »
So, somebody who isn't an NSF member made a great sequence of what a 5RPM spin would look like. They were even able to get some actors to help.

« Last Edit: 01/25/2023 11:22 am by Lampyridae »

#### Bizgec

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##### Re: Realistic, near-term, rotating Space Station
« Reply #3093 on: 01/25/2023 11:54 am »
As promised, Earth from a space station at 1 rpm

Sweet.

Now do one from EML-1, when the Sun is behind the station, at 1.0 and 1.4 rpm.
The Earth isn't visible in that configuration.

#### Solarsail

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##### Re: Realistic, near-term, rotating Space Station
« Reply #3094 on: 01/25/2023 12:02 pm »
(1) Visiting vehicles either need to rotate themselves to dock, (2) or the station must de-spin to receive a docking vehicle.
But you missed a third option - the visiting vehicle does not spin, but the docking capture mechanism on the center of station does counter-spin up to match the orientation of the non-rotating visiting vehicle, grabs and secures it, and then de-spins to match the rotation of the station and then docks the vehicle.

So..  I was trying to formalize the entire trade-space of rotating stations with that post.  I seem to have focused on the static and dynamic forces involved in rotation, interactions across bearings, and how both interact with visiting vehicles.  But I was really trying (and half-succeeding) at being brief and categorical about everything, so I guess I missed some of my assumptions in that wall of text...  In between the detours into my own pet spaceflight ideas.

I'm pretty sure there is a shared category of physical behaviour between the large 0g structures I talked about, and the barest-of-bare de-spun docking ports with a Starship attached.  In both this case, and for intermediate axis issues, a visiting vehicle counts as a part of one large integrated structure once docked.  A 100 ton rotating station with a tiny little de-spun docking port, connecting it to a 120 ton Starship (and it's 150 tons of payload) through a tiny and weak docking port...  Can exhibit many of the same structure-flexing issues as a big and flimsy solar panel + radiator structure connected to a rotating habitat by a small bearing and structure meant for 0g.  Both cases rather require a lack of lateral force transferred from the rotating habitat across a relatively weak bearing.  I'm not sure if that is categorically similar or different to the station ideas with essentially enormous bearings comprised of train tracks between a habitat and a cylindrical containing structure.  They're both bearings...  I separated them  out in my post thinking that structural issues would behave differently between them.  Maybe I broke my categories down wrong.  All of the rotating docking port issues can still show up on stations with bearings.  The total lack of bearings just removes the per-rotation dynamic forces, and vibration issues.  But the docking ports get some different problems any which way you look at it, and some of those seem (to me) to stem from the large scale principle of operation of the rest of the structure.

I think I was looking at that as the big set of issues that everyone was talking past each other on for the last 10 pages here...  There's some other things in this thread and other studies that fill out other parts of the trade space.  Intermediate axis is one of those pervasive questions for any rotating station, then there's the questions of efficient utilization of pressure vessel surface area, changing gravity at different floors, radiation shielding (not universally necessary, but prominent for most near-term stuff), sunlight access (human habitation or growing plants...), radiators not being in sunlight...  some need to change their axis of rotation over time, other concepts replace that with other tradeoffs.

Am I over-thinking the generality of the problem of wobble / resonant vibration across bearings?  Some of the stuff written in this thread makes even the Nautilus-X sound risky, despite originating within NASA.

Alas, I am but an engineering dropout.  Now that rotating space habitats have been on my mind for a few weeks, it's annoying that I don't know my physics well enough to figure out if a given station idea would wobble itself apart or not.  But that means I really can't examine rotating station ideas as practical structures very well.  Maybe there's an analytical solution to figuring out if a given geometry would work or not.  Maybe a computer simulation could depict it's implications.  A computer simulation would probably not be good enough for a research paper...  It's a dynamic system stepping through stuff over time.  But it might be nice for a thread like this to visualize the function of different concepts.

...Actually, a computer simulation with real 3D geometry could also provide simulations of the view out the windows, couldn't it?

Quote
(1) - The challenge with putting the onus on the visiting vehicle to rotate is that for vehicles like the Starship it is yet another operating environment that the engineers need to build into the vehicle before it can leave the ground. And since every deliver to a station will be different regarding the mix of cargo and passengers (i.e. weight & balance in the flying world), that forces the smaller of the two masses (i.e. the ship vs the station) to take on the burden of aligning with the station. I've advocated that this is not a good approach.

I suspect this actually possible, but it is most likely outside of what the engineers of docking vehicles have wanted to deal with.

Quote
(2) - It would be impossible to live on a rotating space station if it keeps changing gravity from "normal" to zero-G. Everything would have to be secured during the zero-G time, and all daily activities would likely have to stop. This would be impractical for a rotating space station that has people living on it, not just doing temporary research.

Now that's worrying for my own pet ideas.    Several concept Mars missions out of NASA and others have involved entire vehicles rotating for gravity during cruise.  That also includes my own Mars orbit-to-orbit ship, which spins up and de-spins as necessary through a half-year flight.  Though I'd guess it is at least as tolerable to put up with as life on a nuclear submarine.  So, probably not great for raising families, maybe the way to go for interplanetary transportation.

Quote
John actually relies on a larger version of this (i.e. mechazilla) in his large station with the large central dock, but if the visiting vehicle is just a space-only cargo/crew vehicle that only transits between the rotating space station and a zero-G transit/warehouse station, then docking the vehicle to the side of the station in the center of rotation shouldn't be a problem.

Visiting vehicles would only dock at the zero-G transit/warehouse station, so they don't need to be modified to support a rotating space station, and the cargo/crew vehicle only travels between the local stations it supports (propellant could be methane from waste processing or hydrogen from water electrolysis). Plus, now you don't have to pack everything onto your station, since you can have virtually unlimited warehousing just a short trip nearby. Likely there would be daily supply trips, just like businesses here on Earth get daily supplies.

And here I wish I knew how to formalize the math on the dynamics caused by station-center bearings.  There's all sorts of new issues brought about by having 0g work and the rotating habitat be independent free-flyers.  Which I might be over estimating.  Or I might be over reading the vibration issues in bearings.  I don't really want to be picking favourite technology choices over issues that could be anywhere between deal-breaker large and immeasurably small.  And bearings are used in enough concepts that...  I would want to study their implications for 0g structures.

I wanted to break everything down to fundamentals to get past the odd back-and-forth on the basic physics involved in each new concept.  It would help to characterize structures with bearings, and rotating-docking ferries, and go from there to figuring out what would make for a practical facility.

A computer program modelling all of this out sounds tempting to me, though I don't know the physics involved in it.  It could generalize to many station geometries, at least as far as they all exist in some N-dimensional tradeoff in many aspects.  Though you then need special case handling for some steps;  The program would probably need to fully distinguish structures that should be at 0g from those that shouldn't, so it can constrain things down to what would actually work, and not need to characterize solar panel wings performing a Tacoma-Narrows impression.

#### lamontagne

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##### Re: Realistic, near-term, rotating Space Station
« Reply #3095 on: 01/25/2023 12:36 pm »

I think there have to be windows, but my preferred arrangement is a cupola type module at the centre of rotation, within which there is a "cage" that counter rotates such that experiments (and people) attached to it experience zero gravity.

I mocked up a 3rpm cupola rotation - assuming one is stationary within the cupola.

Nice.  Clearly there are a number of possible arrangements and the view would depend where you are on the station.
This particular view promotes the interest in the central 0g part of the station. The center of rotation will be a space where there is competition for the different services!

#### lamontagne

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##### Re: Realistic, near-term, rotating Space Station
« Reply #3096 on: 01/25/2023 12:41 pm »

A computer program modelling all of this out sounds tempting to me, though I don't know the physics involved in it.  It could generalize to many station geometries, at least as far as they all exist in some N-dimensional tradeoff in many aspects.  Though you then need special case handling for some steps;  The program would probably need to fully distinguish structures that should be at 0g from those that shouldn't, so it can constrain things down to what would actually work, and not need to characterize solar panel wings performing a Tacoma-Narrows impression.
Look up Freedyn, it might be the tool for you.

or
https://forum.nasaspaceflight.com/index.php?topic=58013.0
for other tools.

#### lamontagne

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##### Re: Realistic, near-term, rotating Space Station
« Reply #3097 on: 01/25/2023 12:48 pm »
As promised, Earth from a space station at 1 rpm

Sweet.

Now do one from EML-1, when the Sun is behind the station, at 1.0 and 1.4 rpm.

You caould also do it from EML-1, when the Earth is behind the station, and hte station is lookingat the night "sky".  Be sure to include constellations.

Are you rethinking 3 rpm?
The Earth will be pretty small.  You will not see the stars if you see the station or the sun.

It's a trade-off.  3 rpm makes for a more compact station.  But at 3 rpm the view is almost stressful, while at 1 rpm it's still fast, but calmer.

#### lamontagne

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##### Re: Realistic, near-term, rotating Space Station
« Reply #3098 on: 01/25/2023 12:52 pm »
I took a few hours this morning to create a Shared Google drive.

Well done.

But.

The format changed overnight.  Yesterday, it looked like I had the ability to change my profile pic and upload files.  Today, it just shows a list of station and such, and there is only a "download all" button.
Check if you used the same link to access.  As a visitor rather than the owner of the site, I think the result changes depending on the access path you take.

Let me know if this works for you.

Or here is the link again.

I could also add you directly to the list if I have your email,  That should be more robust.

#### JohnFornaro

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##### Re: Realistic, near-term, rotating Space Station
« Reply #3099 on: 01/25/2023 01:07 pm »
As promised, Earth from a space station at 1 rpm

Sweet.

Now do one from EML-1, when the Sun is behind the station, at 1.0 and 1.4 rpm.
The Earth isn't visible in that configuration.

YMMV
Sometimes I just flat out don't get it.