Rotating Stations for Tourism

[Nathan2go]

In the Gateway Foundation videos and website (https://voyagerstation.com/building-voyager),


they make a pretty good argument that space hotels should rotate, both as the right answer for tourism and as a step toward space settlements.  Whereas 1 gee acceleration is assumed for settlements, levels between Lunar and Martian could be more attractive for tourism, to simulate those worlds without the inconvenience of going there.  The Voyager station concept is elegant and the wheel configuration is the assumed choice, but given that it is sized for 316 people, and relies on complicated on-orbit welding and assembly as well as utilizing a module size that is far too large to be carried by even the extended length Starship, I’m not convinced it will be the first type to fly.

The hammer configuration is simpler to build, and scales well to smaller sizes.  Also, much of the complexity of Voyager comes from the fact that it allows ships to dock while it’s spinning; however for smaller stations it would not be cost-prohibitive to spin down for dock/undock maneuvers (for Mars gravity at 2 rpm, the radius would be R1=86m at 40.5 mph).  So I think it’s worth discussing what such a station might look like.



The proposed station has the habitat modules along a small portion of an arc in two concentric rows, with a stair-well at either end so that each module has an exit at each end.  The life-boat capsules attach to the stair wells.  It uses a single pressurized elevator tube to connect to a module at the center of gravity (C.G.), and uses a weighted counter-balance on a long truss (R2 = 240m or so).  In the same way that the keel of sailboat usually masses about 25% of the boat’s mass, the counter-balance in this case is also about 25% of the station mass.  Unlike the Voyager station which has a ring truss as the frame which supports the habitat modules, this station would have load-bearing modules as part of the structure, with stiffening cables added after assembly.  As with other rotating stations, it would have adjustable ballast tanks to avoid the floor seeming tilted as people/things move about the station (and keep the wobble low at the center node).

The Voyager Foundation chose 12m diameter for their modules.  However, SpaceX has said their 9m diameter Starship will carry a payload up to 8m diameter, with a length about 17m for a tapering payload in the extended version (which they say is for space construction).  While Voyage is obviously correct that larger is better, 8m does seem to be good enough for an initial offering.  Modules with two decks over a crawl-space need at least 7m diameter (e.g. Airbus A380), but 8m makes it much less cramped.  The modules would be linked by a single main hallway, just below centerline, and each module could also have a local upper hallway and a small basement/crawl-space for equipment.   With small (2*2.5m) rooms, the modules could hold 20 rooms, each with a private lavatory.



For the elevator tube, 4m diameter will allow two elevator shafts, a spiral stairway, air ducts, and room for air-flow.   


The module count is determined by the desired guest capacity.  On this thread https://forum.nasaspaceflight.com/index.php?topic=50945.msg2113957#msg2113957, I argued that New Glenn with a reusable 2nd stage might be large enough for an initial tourism vehicle, and might hold 40 people (based on scaling up Dragon II so that it carries 3*3=9 tons of payload, which at 500 lbs per person gives 40 passengers).  One idea would be to layout the rooms in adjoining pairs, so they can be rented as 20 suites, or 40 small rooms.  Then the hotel would accommodate 1 or 2 New Glenn passenger loads.  So there would be 2 modules for guest rooms, 1 for crew, 3 for restaurants/entertainment, and 2 for equipment; totaling 8 modules. At a volume of 469 m^3 per module, the total is 4.5 times that of the 2017 Starship cabin.  [If the station were instead sized to 16 modules, it could accommodate 160 guests and 60-80 crew, which is likely enough for Starship LEO missions.]

The station could be launched to LEO, but moved to Lunar orbit when the next LEO hotel is commissioned, which is presumably larger and would be served by a larger launch vehicle. Note the same launch vehicle would have smaller passenger capacity for Lunar destinations compared to LEO due to the need for more passenger space for longer flights (e.g. Starship with 160 people in seats or 80 people in 40 mini-cabins).  With a Lunar orbit location (or even Voyager’s 500km sun-synchronous near-polar orbit) radiation shielding is desirable as well; for the 8*16m hab, shielding equivalent to Mars’ atmosphere of 17g/cm^2 (e.g. 17cm thick water, 6.3 cm aluminum, or 2.2 cm steel) the shield would mass 68.3 tons.

Like the traditional Von Braun wheel configuration, this one also can have a docking node at the central zero-G area.  However, with a 2 rpm rotation rate, large vehicles such as Starship can span far from the zero-G area, therefore rigid support and good balance would be required.  So my idea is to not try to keep large vehicles at zero-G.  Instead, of the two axial docking ports, one would be used for docking smaller vehicles and the other would connect to a zero-G recreation room, with de-spun inner walls.  Heavy vehicles would be docked in the plane of rotation, which decreases mechanical stress on the structure.  The counter-balance truss could pivot in-plane to account for rotational component of the vehicle balance, and water ballast would be pumped from tanks near the dock to the hab tanks for the radial balance component.  As previously mentioned, heavy vehicles will dock while the station is spun-down, however the zero-G dock could be used by light vehicles while the station is spinning.  When the station is spun-down and passengers are gone, the docking ports used by the life-boats can be used for maintenance vehicles.

We can quantify the cost of spin up/down, by assuming the construction vehicle is used for propellant service as well.  For the 8-hab station size, there is about 12 equivalent habs worth of station mass at the perimeter; the counter-balance will double that to 24 (it’s lighter but moves faster).  For Martian gravity, the spin rate of 2 rpm gives 40.5 mph spin velocity; so the delta-V for spinning up and down is 81 mph; with a propulsion system Isp =300 sec the Mr would be 1.0125; scaled for 24 hab-equivalent, the propellant consumption is 0.30 hab-equivs per spin up/down cycle [edit: 0.20, see next post].  If we scale the system down to R1= 57m, then at 2 rpm it gives 0.25 gees using a velocity of 26.6 mph, which brings the propellant consumption to 0.20 hab-equivs per cycle [edit: 0.13, see next post]; since each hab mass will be somewhat less than a tanker load, there would be one propellant delivery for every 6-8 passenger loads [edit: 9-12, see next post].

For construction of the 8-hab sized station, there would 3 other large modules (elevator hall/lobby, C.G node, and Zero-g room), which total 11 requiring a launch by a Starship class vehicle.  The 2 stairwells, propulsion module, 5 elevator tube modules (14m long), low-g docking node could all conceivably be launched on 9 New Glenn flights.  The Counter-balance, with a mass equal to 4 of the large modules, would be launched in pieces, in 4 Starship or 10 New Glenn launches. The Truss is light weight, so a portion of it could be launched with each portion of the Counter-balance.

Solar panels would presumably be used, though they are not included in the attached sketches. Voyager station places them on the hab modules, but with the hammer configuration, they could also be attached to booms near the counter-balance.

In summary, availability of a Starship class launch vehicle can enable construction of compelling space hotels; the incorporation of pseudo-gravity into a space hotel is a major complication, but does seem to be surmountable.

[Twark_Main]

I like it.

It uses a single pressurized elevator tube to connect to a module at the center of gravity (C.G.), and uses a weighted counter-balance on a long truss (R2 = 240m or so).  In the same way that the keel of sailboat usually masses about 25% of the boat’s mass, the counter-balance in this case is also about 25% of the station mass.

ISTM that for the price of doubling the length of your access tube, you can profitably switch from the "hammer" configuration to the "bolas" configuration. If the counterbalance is purely ballast, then this immediately drops the mass by 25%. You're replacing a long truss arm with a short pressurized tube (1/3rd the length), so that's probably close to a wash.

Of course the counterbalance probably isn't purely ballast, but honestly there's not that much stuff to put there. Solar panels and radiators don't really benefit from the higher G, and they don't add up to nearly 25% of the station mass. So maybe not all, but most of your counterbalance mass really will be inert ballast that you wouldn't otherwise need.

We can quantify the cost of spin up/down, by assuming the construction vehicle is used for propellant service as well.  For the 8-hab station size, there is about 12 equivalent habs worth of station mass at the perimeter; the counter-balance will double that to 24 (it’s lighter but moves faster).

The counter-balance should have 3x the moment of inertia as the "hammer head." It's 1/3 the mass but it's on a lever arm 3x as long, and moment of inertia goes as mr². So this value should be 48 EHWOSMATP (equivalent habs worth of station mass at the perimeter).

Of course you would quite logically want to put your spin-up / spin-down thrusters on that long lever arm, giving a 3x reduction in propellant use. But you're still yielding a total efficiency multiplier of 3/4 = 75%, meaning the "hammer" configuration needs 33% more fuel per spin-up/spin-down vs. the traditional "bolas" or "toroid" configurations. 


Those minor nitpicks aside, speaking as someone who has tried to square this circle myself I am buoyed by this fine proposal.

[Nathan2go]

ISTM that for the price of doubling the length of your access tube, you can profitably switch from the "hammer" configuration to the "bolas" configuration.

Yes, I had assumed that the hammer configuration was best for only small stations, bolas for medium (maybe not so much for resort hotels, since splitting the facility on the two ends means lots of elevator traffic/dependence), and wheel config for larger ones. 
 
But your next point changed that thinking (thanks for helping):

The counter-balance should have 3x the moment of inertia as the "hammer head." It's 1/3 the mass but it's on a lever arm 3x as long, and moment of inertia goes as mr². So this value should be 48 EHWOSMATP (equivalent habs worth of station mass at the perimeter).

Of course you would quite logically want to put your spin-up / spin-down thrusters on that long lever arm, giving a 3x reduction in propellant use. But you're still yielding a total efficiency multiplier of 3/4 = 75%, meaning the "hammer" configuration needs 33% more fuel per spin-up/spin-down vs. the traditional "bolas" or "toroid" configurations. 

I get confused on the rotational stuff.  But yes, I think that's correct.  The counter-balance adds 25-30% to the station mass (some mass is near the C.G.), and 33% to the propellant.

However, I had miscalculated in the original post, so the resulting propellant use is lower than I'd thought.

Assume there are thrusters on the hab end and the counterbalance.

If each thruster serves the local mass, they'll use equal propellant:  At the habs, the thruster accelerates hab_mass to 41 mph.  At the counter balance, the thruster accelerates hab_mass/3 to 41mph*3.

Now let the counter balance thruster do all the work: it has a 3:1 leverage against the habs, so it only applies 1/3 as much thrust*time for the same rotational acceleration (and it produces less wasteful linear acceleration that gets nulled out half a rotation later).

So moving all the thrusters to the counter balance reduces the total propellant usage to 0.5*(1+.333) = 0.667 of what I calculated above.  So 0.2 hab-equivs of propellant per spin cycle, for 2 rpm Mars gravity and 0.13 hab-equivs at 0.25 G & 2 rpm.

Moving the propulsion up the truss to the counter-balance (further from the passengers) also has a safety advantage.

Note that Voyage puts the thrusters on (downward hanging) "towers", but they are rather short, presumably so they don't hit slowly departing escape pods.   The escape pod issue is still relevant for hammers, but since the tower is 180 degrees away, it is less of an issue.

So while using a counter-balance does increase the station mass and propellant budget, the increase is low  enough that other factors may dominate the decision (e.g. keeping all living space accessible without using the elevator, maximizing the radius to keep the spin rate low for a given internal volume, etc).

[Nathan2go]

As extra motivation for rotating stations, and the hammer configuration, here's a great talk by Joe Carroll of Tether Applications, Inc.

lecture at 20th Annual International Mars Society Convention, 17 Sept 2017.

[Twark_Main]

Happy to help, if only slightly.

Note that Voyage puts the thrusters on (downward hanging) "towers", but they are rather short, presumably so they don't hit slowly departing escape pods.   The escape pod issue is still relevant for hammers, but since the tower is 180 degrees away, it is less of an issue.

Hmmm...  good point. Even at 150 and 210 degrees separation the capsules would be totally fine, but R2/R1 can't get much larger before running into problems...

[high road]

So, the Gateway Foundation is planning to do a demonstration of their welding technology in february. I'm posting here because I didn't want to make a new thread in the commercial space section just yet, because they don't seem to have a good grasp of how out of touch their two big ideas are (Gateway station and Voyager station).

But if they would provide their space assembly technology to customers to build whatever they need in space, that would put them in the same market as Made In Space 3D printing and Nanoracks' space welding technology.



I'll be comparing their test to this:



And Nanoracks' plate cutting demonstration mission in july will be great too.

[Nathan2go]

... they don't seem to have a good grasp of how out of touch their two big ideas are (Gateway station and Voyager station).
 ...

What do you think is wrong with their ideas, specifically?

I think Gateway station is a good idea, but I think it's too big of a jump from where we are today.  Their new Gravity Ring (in-space truss construction demo) is somewhat of an acknowledgment of the big step they are facing, but I don't see how it gets funded either.

I think the initial size needs to be for a passenger load of 1 Starship/week or equivalent.  That's probably 160 guest plus crew.

I think the module size should fit in the extended length Starship, so 8m diameter.  I don't see why any vendor would build a new rocket for 12m payloads until after a market has been proven (Starship is already sized for Mars missions, and NASA can't think of any Lunar payloads that size to launch). It's plausible that Blue Origin could build a rocket for space tourism, say 4 years after Starship, and they might go for a larger diameter, but 9-10m payloads would be an adequate upgrade to please customers.

Also, I'm not sold on the Sun-synchronous orbit.  The 500m altitude will have more space junk,  micrometeors, and radiation; the high inclination makes the radiation even worse.  Once the equatorial countries recognize the opportunity (i.e. French Giana, with their half-hearted ESA launch site), and start playing-to-win, low equatorial orbit could be the place to be.  Although, with mega comm-sat constellations coming, maybe being above Starlink's 550km is the right answer.

Also, their idea of having windows only on one side seems bad.

[high road]

... they don't seem to have a good grasp of how out of touch their two big ideas are (Gateway station and Voyager station).
 ...

What do you think is wrong with their ideas, specifically?

I think the initial size needs to be for a passenger load of 1 Starship/week or equivalent.  That's probably 160 guest plus crew.

Voyager station:

-the idea of building it like a hotel without pools, massive zero gravity or low gravity areas to play around in, or anything else that might attract tourists or keep them entertained for longer than a return trip on the launch vehicle without said hotel. How many times do you go to a hotel and stay inside for days? That's what this is.
-no zero gravity labs or production areas for any economic activities
-expecting billionaires to pay for owning real estate in space. Billionaires pay for comfort, which current technology does not provide
-paying for this by doing a lottery, at least with a trip to the station as the main/only price. I'm not even sure you could do a lottery for a ride on Starship, let alone that it would cover a ride on Starship and fund the station itself.
-expecting the usual space organizarions to rent modules. Their efforts are on zero gravity. Any research on the specific gravity of Voyager station will be a very small subset of experiments.

All of the advantages of this space station can be achieved with just two modules spinning around a central hub. Make that 4 if you wnat them to counterrotate and stabilize without expending fuel. Add modules if you want when demand grows. You'll probably have learned so much by then, you want to start over anyway, rather than stopping the rotation for the expansion.

Gateway station:
- way, way, waaaaay too big for all near future applications combined. As for the above, you could just build two counterrotating sets of modules, keep one at Mars gravity and the other at lunar gravity if you want. Add modules along the axis for zero g applications.
- Star Trek gravity in the docking bay.

And that's just what I remember from seeing the videos a long time ago.

[JohnFornaro]

Their station [Edit: IMO] should be located at EML-1 in a Sun Synchronous Precessional Orbit.  [SSPO]

Also, those videos above, about welding, have been turned into "Private".

Edit: 12-22-22: This is not to assert that "everything" should be at EML-1.  That would prolly cause a black hole to ensue.

[Twark_Main]

Thier station should be located at EML-1 in a Sun Synchronous Precessional Orbit.  [SSPO]

...just because you fancy the idea? 

Why not? Glad you asked! 

  • Harder and longer to reach from the Earth (more delta-v and time), which means your transport cost is higher. That means a higher ticket price for passengers to and from, and greater costs for all terrestrially imported consumables. There will still be a lot of those, even if you grow food and air (which is also $$$).

  • Harsher radiation environment, with less shielding from the Earth itself and the magnetic field. This means your radiation levels are higher (for the same shield), or your shield mass is greater (for the same radiation level).

  • It can't be just eternal sunlight, because it's still cheaper to just use Sun-synchronous LEO.

  • Being located high up in the gravity well is a disadvantage, not an advantage. Crawling uphill is expensive, so we always look for mass-optimized vehicles for that task. "Form follows function."

  • If you're looking for "variable gravity rest stops" for people working on or traveling to/from Earth/Moon/Mars/asteroids, you're better off choosing LEO/LLO/LMO/LAO (depending on the application). Try it! The thought experiment is instructive.

  • For vehicles departing to/from Earth/Moon/Mars, you want to be down low in the gravity well for maximum Oberth. Going to an L-point is a costly detour (like the 90-Day Study stopping at the Moon on the way to Mars).

  • This applies to agricultural stations/repair depots/surgical hospitals/dormitories too, for the same reasons as the above two points.

  • For tourist sightseeing, I'd argue L-points are far worse than LEO/LLO/LMO. The sights are way better up close! As soon as a both-better-and-cheaper low orbit competitor crops up, any L-station that relies on sightseeing is toast.

Don't get me wrong. I like the L-points too. They're neat! But I can't see a practical use for putting a station there (i.e. one that actually gets better numbers than alternative locations).

Those videos above, about welding, have been turned into "Private".

The first video is archived here. Likely it was removed after missing promised deadlines.

Looks like the second video wasn't archived, except for the metadata and preview image.

[JohnFornaro]

The reason for an EML-1 location has been discussed elsewhere.

[JohnFornaro]

Thanks for that link: The CEO makes a lot of "forward looking" statements, and sells a lot of sizzle.  The illustration of their "shop drawing", shown early in the clip, is a mockery of the concept.

In some respects, the "accomplishments" of their design team wane, as the narrator's explanations of "ORT" decisions borders on the juvenile, as if three rows of pedestrian traffic is so much better than two rows thereof, that the station design rests upon the diameter of the spokes proposed for the station.

I gave up at seven or so minutes when they pointed out that the construction time was 48 hours!  Construction time of what, they didn't clarify.

Question for the class:  Did they explain how 24 DreamChasers [if that's a correct guess] managed to synchronize their rotation around the station along their longitudinal axes, and back their way into docking, overcoming one gee forces?  Plus, check out the fine structure of their tension wires used to hold their ORT in place.

I'm not even gonna swipe their acronym.

https://www.youtube.com/watch?app=desktop&v=85MItNr0rBk

SpaceX Starship at Voyager Station: Space Tool fabrication begins!

[OverThePlanetsAndFarAway]

I hope I live long enough to get to a space hotel someday.

[Twark_Main]

The reason for an EML-1 location has been discussed elsewhere.

If it's the same place I'm thinking of, then the justifications you offered in that thread were just as woefully inadequate there, too.

Reposted: https://forum.nasaspaceflight.com/index.php?topic=34036.msg2442251#msg2442251

[Coastal Ron]

Before building a rotating station using our favorite ideas, if you're going to build a rotating space station that is specifically for tourism, then you should be identifying WHAT such tourists would not only want, but enjoy paying for. Since unless you can create an overall experience that tourists not only like, but LOVE, such a venture won't survive.

Here, I'll go first:

A. One of the supposed benefits of being in space is the ability to observe space, but in order to do that on a rotating space station the tourist must have access to a non-rotating part of the station. And don't count on them wanting to watch space on screens from the comfort of their rooms, because they could do that on Earth for a LOT less money. No, they need to see non-rotating space with their eyeballs, which means zero-G.

B. Many have thought that bouncing around in zero-G would be an attraction, and no doubt it will be for a subset of visitors. So what do they want to do, and how much room and equipment do they need?

C. Member "high road" mentioned a pool, and that would be interesting. Not sure if a Earth-gravity pool in space would be a MUST EXPERIENCE attraction, but maybe a less-than Earth-gravity pool would be? Don't know, looking for feedback from swimmers.

OK, what else would be fun in space for tourists to do on a one week visit?

[DanClemmensen]

Before building a rotating station using our favorite ideas, if you're going to build a rotating space station that is specifically for tourism, then you should be identifying WHAT such tourists would not only want, but enjoy paying for. Since unless you can create an overall experience that tourists not only like, but LOVE, such a venture won't survive.

Here, I'll go first:

A. One of the supposed benefits of being in space is the ability to observe space, but in order to do that on a rotating space station the tourist must have access to a non-rotating part of the station. And don't count on them wanting to watch space on screens from the comfort of their rooms, because they could do that on Earth for a LOT less money. No, they need to see non-rotating space with their eyeballs, which means zero-G.

B. Many have thought that bouncing around in zero-G would be an attraction, and no doubt it will be for a subset of visitors. So what do they want to do, and how much room and equipment do they need?

C. Member "high road" mentioned a pool, and that would be interesting. Not sure if a Earth-gravity pool in space would be a MUST EXPERIENCE attraction, but maybe a less-than Earth-gravity pool would be? Don't know, looking for feedback from swimmers.

OK, what else would be fun in space for tourists to do on a one week visit?

Zero-gee sports, not just floating in zero gee.
Space views from the rotating section, via windows in the floor or walls in some compartments.

[Paul451]

Before building a rotating station using our favorite ideas, if you're going to build a rotating space station that is specifically for tourism, then you should be identifying WHAT such tourists would not only want, but enjoy paying for. Since unless you can create an overall experience that tourists not only like, but LOVE, such a venture won't survive.

Not 1g. There's absolutely no reason for a space hotel to have any 1g sections.

And certainly no reason for the virtually the entire station to be at 1g.

Based on Apollo experience: Lunar gravity seems like the obvious g-level for the bulk of the station, including private cabins/sleep-areas, as well as common recreation areas, as well as eating/bathing/toilet areas.

And this is where most of the "activities" will be, given that the existence of gravity simplifies things like ventilation and fluid collection. And it reduces the level of direct staff supervision required. (For eg, to prevent "I can't touch any walls" panic that can occur zero-g.) This level of gravity should be low enough (but high enough) for people to do stupid/fun things without being able to hurt themselves or each other too easily.


You'd want to have places where you feel like you are exposed to space. For eg, a chamber where you are surrounded on all sides by transparent walls, so you can really see space. And a "Bottom of the station/Top of infinity", ultimate vertigo experience: a transparent floor in a dark chamber that lets you look "down" into space, while your senses are telling you that if you fall, you fall forever.

I'm not overly concerned about people seeing a rotating view from most of the station. Lunar-g on a mere 200m wide station requires only 1.2 RPM, a bigger station less. Having the Earth, for example, rotate past your window once every 50 seconds is not a nauseating experience. (If it is for you, you'd already know how sensitive you are and would never travel in space.)

Hence I'd have view-ports in every room, windows/cupolas in all common areas, up to the limit of technical feasibility & safety. Views wouldn't just be limited to zero-g areas. Indeed, you might not bother with windows in the zero-g areas.


You might even have actual EVAs. Walking on the "roof" of the station, where it's fairly safe -- you have a definite "ground", along with railings and harnesses to keep you from jumping/falling -- but you are genuinely doing an EVA! In a vacuum! In space! Zero-g EVAs seem like too much of a risk, unless space-suits get way, way better. Guided EVAs under lunar gravity might be a middle-ground, where the risk is manageable. Very limited, very expensive, lots of training, very high staff-to-visitor ratio.

[Paul451]

Tourists might want zero-g spaces, of course.

I think these would be limited to simple open areas for bouncing off the walls. I wouldn't expect much in the way of "zero-g sports" (or pools) given the time required to adapt to movement in zero-g. I think a basic "vomit comet" type of open space with rope-mesh on the walls and lots of vomit bags is really all you need.

Doesn't need to be too large either, instead you'd have a few separate smaller, more manageable rooms. This is safer and lets you separate tourist-types and activities. Sightseers aren't going to want to be repeatedly crashed into by "bounce-off-the-walls" types. Ditto for "science in zero-g" demonstrations.

But mainly it allows staff to clean up each section when they become too vomit-laden without closing the whole zero-g sector down.


However, even here, actual zero-g might not be necessary. It might be enough for people to experience very low gravity, say 1-2% of 1g. That might be low enough that you don't notice the gravity, it feels like zero-g except with a tendency to drift in one direction if you don't stop yourself. Useless for micro-g research, of course, but perhaps okay for tourists.

If so, it means you don't need the "zero-g" play areas exactly at the hub. That might allow open-hub docking designs, which makes off-centre docking easier, while still giving tourists plenty of "zero-g" experience.


You might also have a small portion of the station at slightly higher g-level to provide areas for visitors to experience Mars gravity. For eg, you might have a "Mars Experience" section, with sand&rocks, Mars-level sunlight, video walls/ceilings, and fake EVA suits.

[Come to think of it, that might be a type of "ride" for the zero-g sections. Pretending to do EVA "missions", without the risks of going outside.]

But I don't think you'd have the bulk of the station at Mars-g. It shouldn't be necessary. And it might be low enough for people to still be off-balance/clumsy, but high enough to be able to injure themselves if they fall, break things if they drop them, etc.

(Of course we might find the opposite. Lunar-g might lure people into bad risks, misjudging how high you can safely fall from, for example. Jumping off a roof in lunar-g might be no worse than jumping off your dining table in 1g, but that's still enough to jar your ankle/knees if you land wrong, or even crack your head open if you faceplant onto the coffee table. Or not realising that you still have enough weight to break something if you swing on it. Whereas Mars-g just high enough to engage Earth reflexes to reduce such misjudgements.)

[JohnFornaro]

If you're going to build a rotating space station that is specifically for tourism, then you should be identifying WHAT such tourists would not only want, but enjoy paying for. ...

A. One of the supposed benefits of being in space is the ability to observe space, but in order to do that on a rotating space station the tourist must have access to a non-rotating part of the station. And don't count on them wanting to watch space on screens from the comfort of their rooms, because they could do that on Earth for a LOT less money. No, they need to see non-rotating space with their eyeballs, which means zero-G.

If one wants to see non-rotating space, I agree.  If one doesn't mind seeing rotating space, then windows in the Ring Station become required.  My RS doesn't quite have such windows; the ones it does include are blinded by the sun during the "day" and show only the inner rings of the station by "night".

In my earliest conception of an RS, before the development of my current idea of an SSPO, or sun synchronous precessional orbit, I mused that the honeymoon suite would have the Earth in one porthole and the Moon in another.  This would be a geocentric orbit which would make the PV panel array far more complicated than I presently show.

As to the activities in the honeymoon suite, I suppose there would be gravitational and non-gravitational options.  It is still not known what the health effects of successful activities may be.  Do embryos require a gravitational field, or will AG suffice?

But back to the rotating view; one or one point four revolutions per minute would not be disorienting.  A non-rotating hub would be absolutely necessary for a non-rotating view.  I'm wondering if I should this complexity to my design.

[JohnFornaro]

Zero-gee sports, not just floating in zero gee.

One word:  Baseball.

OK, two more words: Coriolis effect.