Vast, a Startup for "human habitation, first in LEO, and then beyond"

[Twark_Main]

The public has an idea of what a rotating AG space station looks like, and that ain't it.

I'll say.  AC Clarke had it right.

Different designs for different purposes. See the quote in my footer.

The Vast prototype could be one of the spokes of a ring station. The central hub doesn't look right, however.

Yes, I think those "ellipses" (both geometric and typographic, get it??) are meant to show that the design concept is scalable in that way.

This station would be useful for determining the physiological requirements for gravity, RPM, etc. You need to know these curves before you design a giant station.

They might re-use actual hardware. If each module is its own independent spacecraft and no assembly EVAs are required, then reconfiguring is almost free. Swapping in an upgraded core section would be a piece of cake.

More likely IMO they'd design an iterated vehicle for that role, based on their learnings from this one (a la Falcon 1 to Falcon 9).

Despite its large size, methinks this is still just the "Falcon 1" of artificial gravity! 

[Coastal Ron]

Baton style stations have the end-to-end rotation as their primary axis of rotation, but no natural secondary axis of rotation.

This design solves that with large solar panel wings.

Actually, no it doesn't. Otherwise the docking port would be in line with the solar panels. Now the solar panels and the vehicle that docks will be in competition to be the secondary axis. And the body of the "baton" will swing after the vehicle is attached, and still create a concern for when it detaches.

I'm not understanding that at all. Because in that case you'd think they would focus on module length by creating a 3.5m diameter station x 17.24m long modules that can fit in the Starship, and have LOTS of room left over on the outside.

Minimum viable size. It's a balance, obviously.

We'll see. No doubt they have their reasons, but it means they will have far less available space per "floor" of the station, which means far less space in high gravity areas to validate their assumptions.

The Chinese space station is based off of the Soviet zero-G space stations, and both of those were designed on limitations that likely don't apply today for 1st generation rotating space stations.

True! It's also unrelated to my point about exterior design flexibility.

OK. That still doesn't mean you explained why you brought up the Chinese zero-gravity space station design as justification for a rotating space station design.

Everything about the ISS was expensive because A) it was HUGE, and B) it relied on a transportation system that cost (on average) $1.2B per launch. Lower the cost of launch, and use existing crew transportation systems, and EVA's won't be anywhere near as expensive.

If launch costs go down, then the cost of everything goes down. So there's still no "competitive advantage" for EVAs.

EVAs aren't expensive because of launch costs. They're expensive because of operational costs (lost astronaut time, planning, safety, etc).

There is no competition going on here, so "competitive advantage" has nothing to do with deciding to do EVA's.

And as for cost, the operational cost of the EVA's is directly affected by the operational cost of keeping humans in space, since once you have a human and a spacesuit in space, the cost of an EVA is just consumables and depreciation.

Don't believe me that assembly EVAs are undesirable. Believe NASA: https://nexis.gsfc.nasa.gov/workshop_2010/day2/Sam_Scimemi/ISS_Assembly_Lesson_Learned.pdf

My point was that reducing the diameter of a space station module so that external hardware can be attached to the exterior of the module on Earth doesn't seem like a good tradeoff to me, since EVA's are a proven construction method - and as I just showed, the cost is really negligible once you have the human and the spacesuit in space.

Of course my bias is maximizing volume in rotating space station designs, because my assumption is that even 8m diameter modules are too small for permanent habitation. Meaning module sizes smaller than 8m are really just for testing purposes, not for permanent occupation.

[Twark_Main]

Actually, no it doesn't. Otherwise the docking port would be in line with the solar panels.

No, you misunderstand me.

As long as the solar panels have more total leverage than the docked vehicle, there is no intermediate axis problem.

it means they will have far less available space per "floor" of the station, which means far less space in high gravity areas to validate their assumptions.

Depends what assumptions hypotheses they're validating testing.

If your goal is characterizing an effect at different gravity levels (eg to figure out how much gravity is really needed), then it's perfect!

OK. That still doesn't mean you explained why you brought up the Chinese zero-gravity space station

Sorry to disappoint, but there's no big mystery here: because that Scott Manley video is where I got the idea. He described it very well, so I linked to his video.

Just to be clear, I don't think Vast is cheating off CNSA's homework. I'm saying their design will benefit from an oversized fairing, like it has for CNSA.

There is no competition going on here, so "competitive advantage" has nothing to do with deciding to do EVA's.

Hence my use of scare quotes. I know there's no "real" competition between firms. That's obvious. I'm talking about the cost comparison between EVAs vs other station costs.

Reducing all costs by the same factor doesn't change the relative costs of EVA-based assembly vs automated assembly.

And as for cost, the operational cost of the EVA's is directly affected by the operational cost of keeping humans in space, since once you have a human and a spacesuit in space, the cost of an EVA is just consumables and depreciation.

Tell NASA that.

It's a bit split-brained that you want "proven" EVAs, but you won't listen to the lessons learned by the people who actually proved it.

The entire reason we "prove" technologies first is to follow those lessons, not ignore them.

My point was that reducing the diameter of a space station module so that external hardware can be attached to the exterior of the module on Earth doesn't seem like a good tradeoff

If the engineering trade was solely between "maximum possible size" and "external hardware" then I would agree.

IMO that's not the whole trade, or even the main trade.

Of course my bias is maximizing volume in rotating space station designs, because my assumption is that even 8m diameter modules are too small for permanent habitation. Meaning module sizes smaller than 8m are really just for testing purposes, not for permanent occupation.

It's no surprise, really. If your prime goal is "scale for scaling's sake," you're not going to endorse a "right-sized" design method.

This is exactly why Vast is so rarified. Their goal seems to be low cost (therefore size is bad), in a field where almost everyone else thinks size is good.

[Paul451]

Baton style stations have the end-to-end rotation as their primary axis of rotation, but no natural secondary axis of rotation.

This design solves that with large solar panel wings.

Actually, no it doesn't. Otherwise the docking port would be in line with the solar panels. Now the solar panels and the vehicle that docks will be in competition to be the secondary axis. And the body of the "baton" will swing after the vehicle is attached, and still create a concern for when it detaches.

If the solar panels have more potential angular momentum than the docked vehicle, then the panels are the second axis of inertia. Since they are in the plane of rotation, the design would be stable.

However, since the design assumes Starship is cheap enough to use for building this station, it presumably assumes Starship for supplies/personnel. There's no way the panels have more potential angular momentum than Starship, even with their longer radius, so it would be unstable in docking. Unless there's some kind of dynamically controlled, internal mass-balancing system, it must despin during vehicle docking. That also means there's no escape vehicle for personnel when the station is spinning. The latter is a show-stopper, IMO.

[Coastal Ron]

Actually, no it doesn't. Otherwise the docking port would be in line with the solar panels.

No, you misunderstand me.

As long as the solar panels have more total leverage than the docked vehicle, there is no intermediate axis problem.

I'm not sure you understand how forces are applied in space.

There are no "clocking positions" that keep the station from rotating until there is a greater force, any force applied will affect the orientation of the cylindrical part of the station until some form of equilibrium is achieved.

And to add to the worries, as soon as the vehicle docks, and imbalances start the rotation, the rotation of the cylindrical part of the station could continue to "oscillate" back and forth unless some external force (like thrusters) help the entire station find a new equilibrium. The end result though will still mean that the vehicle will no longer be perpendicular to the plane of rotation - which maybe is something they are planning on handling, but their drawing doesn't provide enough detail.

Oh, and since the solar panels are diametrically opposed, they don't really contribute to a preferred orientation, so a vehicle docking would likely become the predominate secondary axis. Physics, you can't cheat... 

...it means they will have far less available space per "floor" of the station, which means far less space in high gravity areas to validate their assumptions.

Depends what assumptions hypotheses they're validating testing.

If your goal is characterizing an effect at different gravity levels (eg to figure out how much gravity is really needed), then it's perfect!

You are conflating having multiple levels with the amount of room at each level. An 8m diameter "floor" will have more than twice the area than a 6m diameter "floor" (and I'm subtracting the same wall thickness from both to be more realistic).

Floor space, which also is a factor in storage space, is important for long duration tests. For instance, let's say they are able to use all 6m of a diameter, which equals 28.27m2, or 304 sqft. That is not a very large area, especially if you have equipment, furnishings, storage, bathrooms, etc.

There is no competition going on here, so "competitive advantage" has nothing to do with deciding to do EVA's.

Hence my use of scare quotes. I know there's no "real" competition between firms. That's obvious. I'm talking about the cost comparison between EVAs vs other station costs.

Reducing all costs by the same factor doesn't change the relative costs of EVA-based assembly vs automated assembly (with optional interior assembly tasks).

Then...

And as for cost, the operational cost of the EVA's is directly affected by the operational cost of keeping humans in space, since once you have a human and a spacesuit in space, the cost of an EVA is just consumables and depreciation.

Tell NASA that.

It's a bit split-brained that you want "proven" EVAs, but you won't listen to the lessons learned by the people who actually proved it.

The entire reason we "prove" technologies first is to follow those lessons, not ignore them.

I read that NASA slide deck you referenced above, and I don't see what they are talking about cost. In fact when comparing EVA's to the robotic arms (which were supposed to reduce the amount of EVA's) NASA said:

For ISS, the investments made in EVA over many years made EVA assembly tasks the preferred mode of operation

If you think I missed the part about cost, please point it out.

[Twark_Main]

There's no way the panels have more [moment of inertia] than Starship, even with their longer radius, so it would be unstable in docking.

Starship is also unlikely to have their custom 3m x 3m hatch, so it can't be used for oversize cargo anyway.

To solve both problems, an MPLM-like strategy might be used (except it's an independent vehicle). The MoI can then be chosen as needed. It also enables resupply by New Glenn, etc.

For crew escape, the MPLM-alike could just dock with a Starship loitering in formation nearby (at a safe distance), using whatever docking interface Starship is normally equipped with.

If you're building your modules as independent spaceships anyway, essentially the only "add" is a Starship-compatible docking port.

[Twark_Main]

There are no "clocking positions" that keep the station from rotating until there is a greater force

With the solar panels, there is. Rotating the cylinder axially would need to push the panels "up" in the artificial gravity field.

Oh, and since the solar panels are diametrically opposed, they don't really contribute to a preferred orientation

The two halves don't cancel. They would both need to go "up" for the station to rotate, so the effect is reinforced.

An 8m diameter "floor" will have more... area

Yep. That's true.

I read that NASA slide deck you referenced above, and I don't see what they are talking about...

I thought it would be seen as too hand-holding to quote a 6-page Powerpoint, but sure:

From a top level, if we were again to ever craft a complex mission that requires assembly, we should

  – Limit the number of assembly missions; less than 10

  – Require EVA's only when absolutely necessary

That says it right there.

(no, I'm not taking the bait about "cost" where you make up endless fake requirements for what a citation "must" say; I'm not playing that (boring) game with you )


NASA doesn't like assembly EVAs. Feel free to do your own research as to why, but at this point it's really drifting off-topic for this thread.

[JohnFornaro]

Baton style stations have the end-to-end rotation as their primary axis of rotation, but no natural secondary axis of rotation. Then you have the long cylinder which can "spin" along the long access (call it the 3rd axis of rotation), and there is nothing that stops it from doing that.

Well, it won't start rotating around its long axis unless there's a force.  docking could be that force, readily counteracted by anti-rotation jets.

But anyhow, if the station rotates around a bearing such that the central docking area is in a table frame of reference, then problem solved.

There would have to be a circular or rotating airlock, so it would be an engineering challenge.

[JohnFornaro]

See the quote in my footer...

There's a viewpoint that the universe we live in is suitable for "all sites, people, and situations". 

This station would be useful for determining the physiological requirements for gravity, RPM, etc. You need to know these curves before you design a giant station.

The station could instantiate zero, 1/6, 1/3 and one gee environments.  ya gotta live in the "curve" before you can know the curve.

If each module is its own independent spacecraft...

My armchair here is totally adjustable.  Once I set it, I forget it.  The ability to reconfigure the station seems more to be an additional degree of unnecessary difficulty.  Build the station, and start using it. Is there some good reason to be able to take it apart?

[JohnFornaro]

This is exactly why Vast is so rarified. Their goal seems to be low cost (therefore size is bad), in a field where almost everyone else thinks size is good.

I don't know why they did not come up with what  I think is the obvious solution, a ring station.  But note that their design can be, as I mentioned above, expanded such that the tubes as proposed "evolve" into the spokes of a ring station.

Whtever their funding source is, it is a finite source and the first design is not the ultimate design.

[JohnFornaro]

If the solar panels have more potential angular momentum than the docked vehicle, then the panels are the second axis of inertia. Since they are in the plane of rotation, the design would be stable.

We all don't have enough info to compare those masses and moments, but your point still holds.  There would have to be a mass balancing system, along the lines of orbital station keeping.  They would need it anyway, to stabilize the rotation as various masses move up and down the spoke.

[Lampyridae]

Spin-stabilised solid stages for satellites often have a dampening system (basically a ball in a fluid-filled C-channel) that helps deal with perturbations. I imagine something similar could be worked out for a rotating space station.

[Paul451]

There would have to be a mass balancing system, along the lines of orbital station keeping.  They would need it anyway, to stabilize the rotation as various masses move up and down the spoke.

Only for docking. Not for stability. A baton-station is still stable even if you have extra mass up one end. It just moves the Centre-of-Rotation along the length towards that extra mass, there's no instability per se. Even if everyone climbs down to one end of the station ("party in the alpha-arm! come to 1g level!"), you only shift the CoR a few metres in that direction, the baton is still otherwise stable.

You only care that the CoR matches the position of the docking adaptor during docking ops. (Assuming you don't despin during docking. Otherwise you don't even care about that.) That's the only time you need to move some mass around to rebalance the station, and make sure no-one moves around too much during final approach. (Which is going to happen anyway; docking is a specific danger to the station, so everyone would be in their safety/evac positions anyway, with hatches between sections closed in case of collision/breach.)

Or course, you might not want large changes in CoR. For example if you have a low-g/zero-g lab and/or experiments that need a very specific g-load. But that's a secondary reason, not "stability". And only requires a pair of water-tanks, pipes between them, and a slow pump. It doesn't need to be a fast reacting system, nor capable of fine adjustments.

There's no way the panels have more [moment of inertia] than Starship, even with their longer radius, so it would be unstable in docking.

Starship is also unlikely to have their custom 3m x 3m hatch, so it can't be used for oversize cargo anyway.
To solve both problems, an MPLM-like strategy might be used (except it's an independent vehicle). The MoI can then be chosen as needed. It also enables resupply by New Glenn, etc.
For crew escape, the MPLM-alike could just dock with a Starship loitering in formation nearby (at a safe distance), using whatever docking interface Starship is normally equipped with.

Can't see any sign of such a vehicle on their site. No radiators either. Indeed, they are vague or absent in most details. (Which is odd since it's apparently not one-man-in-his-basement-with-no-funding, like the Gateway Foundation, they should be much further along with their design than the single image suggests. Or not odd, if they aren't trying to raise money and don't need to exaggerate the size/capabilities of their "Foundation". <shrug>)

[Coastal Ron]

There are no "clocking positions" that keep the station from rotating until there is a greater force

With the solar panels, there is. Rotating the cylinder axially would need to push the panels "up" in the artificial gravity field.

Show me the physics that supports "clocking positions" for masses that are in space.

Look, even the solar panels won't be perfectly balanced from a purely mechanical standpoint (i.e. imperfections, etc.), so the weight and weight distribution will be slightly different on each side (and this ignores how the inside of the station is balanced with cargo and crew).

But let's say that the solar panels are perfectly balanced. When the vehicle is attached to the side of the station, perpendicular to the solar panels, it won't be balanced by another vehicle (or mass) on the opposite side, so the equilibrium that existed before the vehicle docked will no longer exist, and a new equilibrium will need to be found - which will likely result in the station rotating 90 degrees so that the vehicle is now "following" the long axis in rotation.

Oh, and since the solar panels are diametrically opposed, they don't really contribute to a preferred orientation

The two halves don't cancel. They would both need to go "up" for the station to rotate, so the effect is reinforced.

From a physics standpoint they are just masses hanging off a larger mass, and if the amount of solar panels on each side, by mass, is the same, then their masses cancel out.

I read that NASA slide deck you referenced above, and I don't see what they are talking about...

...NASA doesn't like assembly EVAs.

Yet they do them, and depend on them for keeping the ISS operational. I think you are reading too much into one slide deck... 

Besides, if properly designed, I think the entire VAST station could be connected together in a day or two with a team of two astronauts on EVA. Considering how much traffic there will be to the station to get it stocked and occupied, that is not a lot of complication.

[Paul451]

Look, even the solar panels won't be perfectly balanced from a purely mechanical standpoint (i.e. imperfections, etc.), so the weight and weight distribution will be slightly different on each side (and this ignores how the inside of the station is balanced with cargo and crew).
But let's say that the solar panels are perfectly balanced.
[...]
From a physics standpoint they are just masses hanging off a larger mass, and if the amount of solar panels on each side, by mass, is the same, then their masses cancel out.

The solar panels don't been to be perfectly balanced, nor do their masses "cancel out".

They are in the plane of rotation, which adds momentum to the plane of rotation, increasing the stability, reducing any non-planar rotation. In effect, it's making the baton more like a wheel or Frisbee. Thus the secondary/intermediate axis is in the plane of rotation, which is an inherently stable mode. (The most stable.)

They won't out-mass Starship, but they should have enough inertia (especially if they include radiators on the back) to have more rotational inertia than a small capsule/module docked close to the centre.

(I'm emphasising rotational inertia over mass, because radial distance increases rotational inertia vs the same mass closer to the centre.)

When the vehicle is attached to the side of the station, perpendicular to the solar panels, it won't be balanced by another vehicle (or mass) on the opposite side

"Balance" is irrelevant to the intermediate axis issue. If you had a balancing mass on the opposite side, it would increase the total potential rotational inertia in that axis, increasing the likelihood that is has more inertia than the axis with the solar arrays, thus increasing the likelihood that it will become the new secondary/intermediate axis, making the structure unstable.

[Coastal Ron]

I'm going to re-order the conversation, for a reason:

They won't out-mass Starship, but they should have enough inertia (especially if they include radiators on the back) to have more rotational inertia than a small capsule/module docked close to the centre.

A Starship will never dock with this station. Never. Too dangerous.

Why? The Starship is not built to be stable when rotating, and besides the buttload of weight at one end of the ship (i.e. the engines), you have large tanks with lots of propellant that can slosh around and change momentum and center of gravity in ways that are likely unpredictable.

No captain of a Starship in their right mind would try to mate to a rotating space station.

What I think they will use, and what I'm assuming for my designs, is what you also suggested - some sort of small capsule/module to transfer cargo and crew. It could be a vehicle they keep at the station, which shuttles between the station and the visiting vehicle. Or it could park away from the station when not used. That is also what my plans call for.

Look, even the solar panels won't be perfectly balanced from a purely mechanical standpoint (i.e. imperfections, etc.), so the weight and weight distribution will be slightly different on each side (and this ignores how the inside of the station is balanced with cargo and crew).
But let's say that the solar panels are perfectly balanced.
[...]
From a physics standpoint they are just masses hanging off a larger mass, and if the amount of solar panels on each side, by mass, is the same, then their masses cancel out.

The solar panels don't been to be perfectly balanced, nor do their masses "cancel out".

They are in the plane of rotation...

They are in the plane or rotation no matter what orientation to the station they are in. Rotate the panels 90 degrees on the body of the station and they are still in the same exact plane of rotation for the body of the station. That is because there are an equal number of them on either side of the body of the station, so they don't affect the center of gravity for the cross section of the station, regardless what rotational position they are in.

...which adds momentum to the plane of rotation...

Take any point on the solar panel, then measure across the center of gravity for the cross section of the station, and you'll find the momentum change is likely negligible regardless how the panels are rotated.

And speaking of rotation, if this station is in orbit around the Earth, and the station itself is rotating, how the heck are the panels they show going to be effective? Are they going to be swiveling at the rpm of the stations, as well as the rpm of the orbit around the Earth?

Not sure I understand their solution yet... 

When the vehicle is attached to the side of the station, perpendicular to the solar panels, it won't be balanced by another vehicle (or mass) on the opposite side

"Balance" is irrelevant to the intermediate axis issue. If you had a balancing mass on the opposite side, it would increase the total potential rotational inertia in that axis, increasing the likelihood that is has more inertia than the axis with the solar arrays, thus increasing the likelihood that it will become the new secondary/intermediate axis, making the structure unstable.

I only mention balance to describe how the panels are not really a factor in regards to a vehicle docking at the station. The vehicle docking at the station will add weight/mass perpendicular to the direction of rotation, though because the station is a cylinder, the cylinder can easily rotate to bring the vehicle into the plane of the rotation.

If that happens, then undocking becomes far more difficult without using station thrusters to reorient the station so that the vehicle can leave to the side (just as it arrived). But relying on station thruster means that you have to have the propellant onboard in order to release the visiting vehicle - not really fail safe.

[Paul451]

The solar panels don't been to be perfectly balanced, nor do their masses "cancel out".
They are in the plane of rotation...

They are in the plane or rotation no matter what orientation to the station they are in. Rotate the panels 90 degrees on the body of the station and they are still in the same exact plane of rotation for the body of the station. That is because there are an equal number of them on either side of the body of the station, so they don't affect the center of gravity for the cross section of the station, regardless what rotational position they are in.

...which adds momentum to the plane of rotation...

Take any point on the solar panel, then measure across the center of gravity for the cross section of the station, and you'll find the momentum change is likely negligible regardless how the panels are rotated.

I was confused by what you are saying, until I read this...

And speaking of rotation, if this station is in orbit around the Earth, and the station itself is rotating, how the heck are the panels they show going to be effective? Are they going to be swiveling at the rpm of the stations, as well as the rpm of the orbit around the Earth?

The panels (and the station) rotate in a flat plane. The rotational axis points in a constant direction. Point it at the sun and the panels are always perpendicular to the sun. They don't need to rotate at all. And indeed, might be fixed in place.

I don't think you are picturing the rotational axis of the pictured station correctly. So everything else is going to confuse you.

"Balance" is irrelevant to the intermediate axis issue. If you had a balancing mass on the opposite side, it would increase the total potential rotational inertia in that axis, increasing the likelihood that is has more inertia than the axis with the solar arrays, thus increasing the likelihood that it will become the new secondary/intermediate axis, making the structure unstable.

I only mention balance to describe how the panels are not really a factor in regards to a vehicle docking at the station. The vehicle docking at the station will add weight/mass perpendicular to the direction of rotation, though because the station is a cylinder, the cylinder can easily rotate to bring the vehicle into the plane of the rotation.

And to do so, it has to rotate the solar arrays out of the plane of rotation, "uphill" from an energy stand-point. That's why the relationship between the rotational inertia of the arrays and the inertia of the vehicle matters. If the vehicle has more inertia going "downhill" than the panels going "uphill", then the station is unstable. If the vehicle has less inertia going "downhill" than the panels going "uphill", then it won't, and the station is stable.

[edit: fixed bung quote]

[Twark_Main]

See the quote in my footer...

There's a viewpoint that the universe we live in is suitable for "all sites, people, and situations".

I think you're misunderstanding the quote.

It is meant as antithetical to the "magic bullet" fallacy, where there is imagined to be one big solution that is appropriate in any context and for any purpose.

The station could instantiate zero, 1/6, 1/3 and one gee environments.  ya gotta live in the "curve" before you can know the curve.

Exactly. You get all those experimental environments simultaneously.

The ability to reconfigure the station seems more to be an additional degree of unnecessary difficulty.

Modern modular stations have lots of reasons to reconfigure, mainly during assembly. The only question is how to accomplish that.

I'm guessing the degree of redundancy, flexibility, and contingency optionality it offers makes it worth the trade.

Axiom seems to think so too. Not to mention all the Russian / historic USSR space stations, which have always used modules that are independent spacecrafts (including the Russian ISS modules). Ditto for China.

The USOS "dumb can" modules are the exception, not the rule.

[Twark_Main]

Can't see any sign of such a vehicle on their site.

Unsurprising, since the station render itself was only posted a few days ago.

Absence of evidence is not evidence of absence. Point is, there are possible solutions to the show-stopper.

No radiators either.

As mentioned, I suspect the radiators are on the backside of the PV. If you look closely, you'll note that the "PV" is actually made up of two slightly different size panels, one in front of the other.

Putting more mass out on the wings helps stability, of course. It also makes double use of some hardware. The tradeoff is complexity.



It looks like the panels might not pivot. Possibly another ISS "lesson learned," since those rotary joints were notoriously problematic.

The other possibility is that the panels articulate during free-flight, but not while the station is under rotation. Avoiding constant motion should improve reliability.

[Twark_Main]

Show me the physics

In addition to what Paul wrote, this video might be useful:



Also this blog post: https://highfrontierblog.com/2014/07/30/rotational-dynamics/

I think you are reading too much into one slide deck

I didn't get it from the slide deck. I first heard it in a NASA interview, but (as usual) you can't find anything twice on the internet nowadays. 

The rendering appears to show independent spacecraft, with an RCS pod on one end similar to Axiom. If they're doing independent spacecraft, they're halfway there. I assume they'll take NASA's hard-won lessons to heart and minimize (or better yet eliminate) EVAs. Why wouldn't they? It's easy enough to route pipes and cables inside instead of outside.

The secret is to keep the airtight utility pass-throughs, but just pass through into the pressurized vestibule instead of outside. That way you never find yourself scrambling to unplug wiring when you need to close a door and isolate a leaking module.