SpaceX to NASA quote : simplified mission architecture : Technical discussion

[rsdavis9]

I think we are chasing nitpicks worrying about boiled prop.  If it's that close the mission is a no-go because there's not enough redundancy when human lives are on the line.

Refuel on the moon's surface, just like we would on Mars surface, and there's prop enough for any scenario, including a tanker falling over on the moon in a moonquake (just not all of them).

This gives us massive redundancy, which is FAR safer for humans.  The only critical things left are TLI burn, moon landing, and return EDL (even the insertion burn you can loop back to earth somehow usually, c.f. apollo 13 - and EDL can involve aerobrake to lower orbit if there's a problem detected early in the entry).

Failure to launch on the moon?  Backup EDL capable starship already there.  too much fuel boiled off?  Extra fuel on the moon.

It so happens this is how you would efficiently run a lunar colony instead of a one off plant the flag mission (which we already did) .  So much the better.

The only reason I nitpicked was because everybody was talking about boiling and not mentioning pressure which in space is meaningless. On earth containers holding stuff at 1 atm is the norm because ...

In space you can have any pressure in a vessel and the pressure determines what temp it boils at. If raptor likes 80K LOX because the mass flow works the best than just make sure your container in space(depot) is at the correct pressure and it will by default be the correct temp. Even with cryocooling is it a good idea to cool below boiling? I assume cryocooling would work similar to ground atmosphere systems. Take in gas and output liquid. Gas has to come from the boiling of the liquid.

[TheRadicalModerate]

AIUI the answers for Mars include "use the CO₂ in the atmosphere to make fuel"...

Minor quibble:  "Use CO₂ and water to make fuel."  You have to have hydrogen available.  There's disagreement whether full methalox or LH2 should be imported to begin with, whether robotic water mining is possible, or if human crews are required to be stranded until they learn how to mine water.

But that just shows how unlike the Mars technology chain is from the lunar one, at least to begin with.

[Vultur]

AIUI the answers for Mars include "use the CO₂ in the atmosphere to make fuel"...

Minor quibble:  "Use CO₂ and water to make fuel."  You have to have hydrogen available.  There's disagreement whether full methalox or LH2 should be imported to begin with, whether robotic water mining is possible, or if human crews are required to be stranded until they learn how to mine water.

But that just shows how unlike the Mars technology chain is from the lunar one, at least to begin with.

For Starship/Raptor, this is true. It *is* possible to make rocket propellant on Mars without hydrogen (CO fuel + O2 oxidizer) and this might be pursued if having people wait to set up water mining before return wasn't acceptable. (SpaceX is thinking a settlement model, so there's no real cost to waiting in that model. A pure exploration model would be different.)

Having an atmosphere with C, O, and N available makes a big difference for the practicality of ISRU.

Also, water mining on Mars is probably much easier than on the Moon, since solar power is available in the same place as the water ice and you're working in more like Antarctic winter temperatures than Pluto winter temperatures.

Moon ISRU isn't that near term, I don't think. It's not available for the first few Artemis missions even with Starship's large landed mass capacity.

[TheRadicalModerate]

In space you can have any pressure in a vessel and the pressure determines what temp it boils at. If raptor likes 80K LOX because the mass flow works the best than just make sure your container in space(depot) is at the correct pressure and it will by default be the correct temp. Even with cryocooling is it a good idea to cool below boiling? I assume cryocooling would work similar to ground atmosphere systems. Take in gas and output liquid. Gas has to come from the boiling of the liquid.

Let's suppose that the depot has infinite cooling power, so the prop remains subcooled at 4-6bar, and the density is optimized.

What happens when the prop is transferred into the target, which almost certainly doesn't have infinite cooling power?  The answer to that depends on how long the transfer takes, how long it takes to do undocking, back-away prox ops, and pre-burn checkout, before the actual burn takes place.

Starship on the ground can only hold a brief period after the tanks are fully filled, because the prop expands as it warms up and liquid coming out of the vents is bad.  There's no requirement that the tanks be fully filled in space, so you can in theory make that time between filling and burning be arbitrarily long.

But that's effectively equivalent to loading the prop at a lower density, which is what reduces the effective prop mass, and therefore the total available delta-v.  How much is that penalty?  We know that subcooling generally adds ~8%¹ more mass to the prop load, but maybe the the prop only warms up enough to reduce that to 7% or 6%--we don't know the number--in the time it takes from transfer beginning to when the burn starts.

An accurate number is a big deal.  An ~8% reduction in the prop load for a v3 is 1493t instead of 1600t, 107t less.  That's more than 2200m/s before burnout for a 125t inert mass.  For a v4, it's 154t less.  If the inert mass of the HLS is 135t (dry mass, crew module, returned samples, sump and ullage prop that's unusable), that's about 230m/s of extra delta-v.  If the time between when transfer begins and the burn starts is short, it's less of a big deal.

Update: Removed delta-v braino and replaced it with better numbers.

___________
¹I'm uncertain of this 8% number.  I believe it was mentioned by Elon at some point wrt F9, but densifying kerolox is different from densifying methalox.

[InterestedEngineer]

Can light weight fully fueled V4 go from LEO to moon landing and back to LEO? What is mass fraction should be?

I can't even imagine this happening in time for a
Artemis "simplification", but the short answer is no.

The GREATEST simplification here isn't technology, it's schedule.  The current fake schedule is a joke, quit trying to match it, it just leads to heartache, huge costs, and one-time-only missions with no point to them besides plant the flag (which we already did).

When you are embracing promising new tech, you have to abandon schedule to someone you trust.  I've been in Elon's position before (at a FAR smaller scale mind you), you have to trust your technologists to deliver.  Eventually.  I have two pretty successful products I was either a lead on or THE lead architect on that was done this way.  The kind where you gamble the entire company on it.  Losing is terrible, but winning is awesome.

Instead, embrace the change, trusting it'll work, that the new space way of doing things (stop throwing things away, mass production and the redundancy it allows (= safety), cheap launch costs) means you can actually have a permanent antarctic-style research base for the cost of of an old-space plant-the-flag mission.

So dump the artificial fake schedule that is currently Artemis.  It's the best simplification.  All else falls out from that.

Wait (not much longer and possibly shorter than Artemis's real schedule), and you have a far safer mission that does what we need to do for Mars, so we get to practice locally.

And yes, I know there's no carbon on the moon so no ISRU, we have to ship in fuel.  It changes almost nothing, as the fuel requirements are lower, you still have to transfer the fuel to the landed ship, landing ships could blow up your fuel depot, etc etc etc - all problems we'll have on Mars.   In fact it's simpler, there's no ISRU to depend on.

[InterestedEngineer]

To put it in standard project management terms: 

Scope, Schedule, Cost:  Pick any two you want to fix (preferably prioritizing one), the other variables you can't control:

If the new tech is 10× better, the rational tradeoff is:

Fix scope + fix cost, let schedule slip.

Reason:
• Scope is the whole point — cutting it destroys the 10× advantage.
• Cost is usually bounded by funding reality (in our case Starlink and federal budgets are huge)
• Schedule is the only elastic variable; bleeding-edge programs always take longer because unknowns dominate.

In short: protect the breakthrough, protect the budget, eat the delay.

[redneck]

And yes, I know there's no carbon on the moon so no ISRU, we have to ship in fuel.  It changes almost nothing, as the fuel requirements are lower, you still have to transfer the fuel to the landed ship, landing ships could blow up your fuel depot, etc etc etc - all problems we'll have on Mars.   In fact it's simpler, there's no ISRU to depend on.

I would suggest that there is no readily identifiable carbon on the moon that can be economically accessed at this time. Eventually, in a few decades, carbon deposits from asteroid impactors  will be located. IF it becomes economically feasible, they will be mined.

It would make no sense to incorporate that future possibility into current plans. There are all kinds of possible resources that are conjecture at this time that should not be part of serious planning.

[wes_wilson]

This is where expendable starships start to shine.  End of life starships land on the moon carrying cargo OR fuel.  The lack of a need to return to llo, nrho, leo, or earth increases the landed mass significantly. 

Substituting in <some> expendable starships as part of the design eases margins. 

Run the math on how much cargo a fully fueled in LEO starship can park on the moon if nothing is reserved for return.  Ignore, for the moment, side issues like debris, landing radius's, moving the cargo once it's landed. 

[rsdavis9]

And yes, I know there's no carbon on the moon so no ISRU, we have to ship in fuel.  It changes almost nothing, as the fuel requirements are lower, you still have to transfer the fuel to the landed ship, landing ships could blow up your fuel depot, etc etc etc - all problems we'll have on Mars.   In fact it's simpler, there's no ISRU to depend on.

I would suggest that there is no readily identifiable carbon on the moon that can be economically accessed at this time. Eventually, in a few decades, carbon deposits from asteroid impactors  will be located. IF it becomes economically feasible, they will be mined.

It would make no sense to incorporate that future possibility into current plans. There are all kinds of possible resources that are conjecture at this time that should not be part of serious planning.

So the moon doesn't have carbonate rocks? Like limestone?

https://en.wikipedia.org/wiki/Geology_of_the_Moon#Lunar_rocks

I guess not. Mostly  olivine, pyroxene, and plagioclase feldspar (anorthite).

[Greg Hullender]

AIUI the answers for Mars include "use the CO₂ in the atmosphere to make fuel"...

Minor quibble:  "Use CO₂ and water to make fuel."  You have to have hydrogen available.

I was really looking forward to coal-burning rockets, though! :-)

[TheRadicalModerate]

To put it in standard project management terms: 

Scope, Schedule, Cost:  Pick any two you want to fix (preferably prioritizing one), the other variables you can't control:

If the new tech is 10× better, the rational tradeoff is:

Fix scope + fix cost, let schedule slip.

It's not a single piece of tech, it's multiple pieces.  With lunar surface rendezvous, you're adding new pieces of tech:  high-reliability precision landing (note that "high reliability != "precision"), debris mitigation, and surface prop transfer, which in turn implies some kind of tanker vehicle, because there's zero chance you're getting close enough to do direct ship-to-ship prop transfer.

Reason:
• Scope is the whole point — cutting it destroys the 10× advantage.

But adding new tech is increasing the scope.  That's a Project Management 101 mistake.

Nobody's proposing that we reduce the scope.  We're looking for ways to maintain the scope, which is to prove out the transportation of humans to and from the Moon in a sustainable fashion, as a precursor to doing a lot of the things you want to do.

• Cost is usually bounded by funding reality (in our case Starlink and federal budgets are huge)
• Schedule is the only elastic variable; bleeding-edge programs always take longer because unknowns dominate.

Point of order:  The purpose of "simplification", which is what we're discussing here, is to accelerate the existing schedule.  If you're doing things that increase the schedule (and you definitely are, with your plan), then you're not meeting the requirements stipulated in the thread topic.  You're also not doing anything that accelerates the overall acquisition of a base and all the things you want to do; you're just chunking multiple phases together, which always increases schedule risk.

In short: protect the breakthrough, protect the budget, eat the delay.

What part of the breakthrough needs protecting?  AFAICT, the breakthrough is oribital refueling with a robust landing capability.  That's still needed in any of the simplification / acceleration schemes we've been discussing.

We may be eating delay no matter what.  Increasing the scope just increases that delay.

I have no problem with a lunar base; I want one ASAP.  I also have no problem with lunar surface refueling, although I don't think it makes a lot of sense unless we can make lunar LOX, either through water electrolysis or, better still, through metal oxide reduction.  I also have no problem with doing the things that are necessary to have a properly phased program that advances as quickly as possible.

My problem is that your proposal does none of those things.  It's not making prop, it's importing it.  It's not setting up a lunar base, it's going down a path that's needed only for early Mars return missions, and maybe not even then.  And it's guaranteeing additional schedule slip to fulfill requirements that aren't current requirements, and don't really provide more functionality.  It's classic mission creep, which they also teach you to avoid in Project Management 101.

[TheRadicalModerate]

This is where expendable starships start to shine.  End of life starships land on the moon carrying cargo OR fuel.  The lack of a need to return to llo, nrho, leo, or earth increases the landed mass significantly. 

I have no problem with expendable Starship HDLs.  When I've analyzed the costs of expending an HDL on the lunar surface vs. returning it to Earth, the cost per tanker launch needs to be well under $10M for the additional refueling to make the mission cheaper, so expending them is a no-brainer.

But you need to be expending them on something that makes sense.  It's your application (and InterestedEngineer's) that I'm objecting to.

Run the math on how much cargo a fully fueled in LEO starship can park on the moon if nothing is reserved for return.  Ignore, for the moment, side issues like debris, landing radius's, moving the cargo once it's landed.

Unless you're only landing propellant, which is a silly application (see up-thread), you're limited by two things:

1) The amount of payload you can launch, which is going to be no more than 150t, and likely less.  There's no capability for aggregating payloads in orbit, and creating such a capability should be way, way down on the list of things to do.

2) The packaging of the payload.  All of the HDL payloads under consideration are well below 20t.  Anything above that value requires careful engineering, which likely takes more time than just sending more Starships with quick-and-dirty, non-optimized payloads, which still have to fit through the hatch.

[InterestedEngineer]

To put it in standard project management terms: 

Scope, Schedule, Cost:  Pick any two you want to fix (preferably prioritizing one), the other variables you can't control:

If the new tech is 10× better, the rational tradeoff is:

Fix scope + fix cost, let schedule slip.

It's not a single piece of tech, it's multiple pieces.  With lunar surface rendezvous, you're adding new pieces of tech:  high-reliability precision landing (note that "high reliability != "precision"), debris mitigation, and surface prop transfer, which in turn implies some kind of tanker vehicle, because there's zero chance you're getting close enough to do direct ship-to-ship prop transfer.

Reason:
• Scope is the whole point — cutting it destroys the 10× advantage.

But adding new tech is increasing the scope.  That's a Project Management 101 mistake.

The scope is the same as Mars.  The end goal IS Mars. Anything else is increasing the scope.  One off moon missions that have custom throw away hardware are increasing the scope.

Without a ready source of carbon, the moon will NEVER be anything more than an antarctic style research outpost.  We are carbon life forms, we need carbon, and plenty of it. (turns out rockets do too, if you want tanks that are reasonably sized, rocket engines that are simple, low cost, and well tested, etc)

Nobody's proposing that we reduce the scope.  We're looking for ways to maintain the scope, which is to prove out the transportation of humans to and from the Moon in a sustainable fashion, as a precursor to doing a lot of the things you want to do.

Ah, we agree on that  goal at least.  One off throw away flag planting missions are the opposite of that goal.

• Cost is usually bounded by funding reality (in our case Starlink and federal budgets are huge)
• Schedule is the only elastic variable; bleeding-edge programs always take longer because unknowns dominate.

Point of order:  The purpose of "simplification", which is what we're discussing here, is to accelerate the existing schedule.  If you're doing things that increase the schedule (and you definitely are, with your plan), then you're not meeting the requirements stipulated in the thread topic.  You're also not doing anything that accelerates the overall acquisition of a base and all the things you want to do; you're just chunking multiple phases together, which always increases schedule risk.

Right.  I fundamentally disagree with the premise of the thread if it's trying to bring in the schedule.  Fixing the schedule is a fundamental project management mistake for this type of development, where the new tech (reusable rockets) is 10x better than the existing tech (it's more like 100x, but 10x is good enough to justify)

Fundamentally, shortening the schedule is doing stuff the old space way.  It's a waste of time and money, and  our flag is already on the moon, so there's no political value.

The moment you introduce throw-away custom brand new rockets (HLS, cough), you are doing it the old-space way.  (I have no problem with throwing away used standard rockets that have paid for themselves).

In short: protect the breakthrough, protect the budget, eat the delay.

What part of the breakthrough needs protecting?  AFAICT, the breakthrough is oribital refueling with a robust landing capability.  That's still needed in any of the simplification / acceleration schemes we've been discussing.

We may be eating delay no matter what.  Increasing the scope just increases that delay.

I have no problem with a lunar base; I want one ASAP.  I also have no problem with lunar surface refueling, although I don't think it makes a lot of sense unless we can make lunar LOX, either through water electrolysis or, better still, through metal oxide reduction.  I also have no problem with doing the things that are necessary to have a properly phased program that advances as quickly as possible.

My problem is that your proposal does none of those things.  It's not making prop, it's importing it.  It's not setting up a lunar base, it's going down a path that's needed only for early Mars return missions, and maybe not even then.  And it's guaranteeing additional schedule slip to fulfill requirements that aren't current requirements, and don't really provide more functionality.  It's classic mission creep, which they also teach you to avoid in Project Management 101.

The distractions are of making a throwaway HLS, and moon refueling rendezvous that have zero to do with Mars, and dealing with non-EDL returns from the moon which are in the long run never going to be financially viable due to the very large amount of fuel needed near Luna, and the transfer of astronauts between ships, the non-redundancy of the entire Artemis architecture and its derivatives, probably not an inclusive list here, I'm sure I've missed some distractions.

The initial manned missions to Mars will likely include return fuel.  So will ones to the moon.  They will all have redundancy made financially possibe by mass manufacturing of cheap rockets.

Long term, I'd love to have fuel generation on the moon.  When someone finds a cheap source of carbon, then go for it. 

I'd love to see EM-L1 fuel depots helping with moon and interplanetary speedy transfers.  But that is definitely schedule creep, not needed for the first few missions.

[TheRadicalModerate]

The distractions are of making a throwaway HLS, and moon refueling rendezvous that have zero to do with Mars, and dealing with non-EDL returns from the moon which are in the long run never going to be financially viable due to the very large amount of fuel needed near Luna, and the transfer of astronauts between ships, the non-redundancy of the entire Artemis architecture and its derivatives, probably not an inclusive list here, I'm sure I've missed some distractions.

You seem to think that there's no evolution for either the Moon or Mars, and that everything has to be done immediately to the way you envision the system will stabilize.  Why do you think that?  Do you really think that more than 5 of the first 50 Starships on Mars are returning?  Do you really think that a propulsive return to LEO from the Moon is the endpoint?

Phasing stuff is good.  It's essential to iterative development.  When you try to do everything at once, you get... Orion.

The initial manned missions to Mars will likely include return fuel.  So will ones to the moon. 

Yup.  But why do you think that prop will be delivered to the surface?  v4 will be able to depart from LEO, land on Mars, and return to LMO, all on one tank of prop.  v3 HLS will do essentially the same thing, doing LEO-LS-LLO.

[Twark_Main]

Run the math on how much cargo a fully fueled in LEO starship can park on the moon if nothing is reserved for return.  Ignore, for the moment, side issues like debris, landing radius's, moving the cargo once it's landed.

Unless you're only landing propellant ... you're limited by ... The amount of payload you can launch, which is going to be no more than 150t, and likely less.  There's no capability for aggregating payloads in orbit...

A bit sloppy in the reasoning here. This would become correct if you delete the word "only."

If you land propellant and cargo (both "payload mass") then you can clearly land more payload than 150 tonnes, because you can aggregate the propellant in orbit.

[spacenut]

There is oxygen on the moon.  Oxygen has more mass and can be produced on the moon.  Methane and even hydrogen can be brought to the moon.  Both have far less mass than oxygen.  Bring methane as part of the "cargo" and refill with oxygen on the moon to use to get back to either the Artemis station or an L1 station. 

Ok, from what you guys are saying, there will be a need at whatever fuel depot is used or multiple depots, for refrigeration equipment as well as shading.  Neither is impossible.  Shading can be done with solar panels.  The electricity produced can re-cool the fuel and oxygen stored at the depot.

Enough fuel stored at say a modified Starship depot, to completely refuel a lunar Starship or a Mars bound Starship.  For lunar, another fuel depot at the Artemis station can again refuel a lunar Starship for landing and return to the station.

Again, nothing is impossible.  Timing is the key.  Eventually a large slow spinning to create artificial gravity fuel depot could be built that could store oxygen, methane, and hydrogen for any spacecraft to stop and refuel for outbound ships.  Only other options are to use hypergolic fuels that can be stored and transferred for in space only hypergolic powered spacecraft or nuclear powered spacecraft. 

[InterestedEngineer]

There is oxygen on the moon.  Oxygen has more mass and can be produced on the moon.  Methane and even hydrogen can be brought to the moon.  Both have far less mass than oxygen.  Bring methane as part of the "cargo" and refill with oxygen on the moon to use to get back to either the Artemis station or an L1 station. 

Ok, from what you guys are saying, there will be a need at whatever fuel depot is used or multiple depots, for refrigeration equipment as well as shading.  Neither is impossible.  Shading can be done with solar panels.  The electricity produced can re-cool the fuel and oxygen stored at the depot.

Enough fuel stored at say a modified Starship depot, to completely refuel a lunar Starship or a Mars bound Starship.  For lunar, another fuel depot at the Artemis station can again refuel a lunar Starship for landing and return to the station.

Again, nothing is impossible.  Timing is the key.  Eventually a large slow spinning to create artificial gravity fuel depot could be built that could store oxygen, methane, and hydrogen for any spacecraft to stop and refuel for outbound ships.  Only other options are to use hypergolic fuels that can be stored and transferred for in space only hypergolic powered spacecraft or nuclear powered spacecraft.

No carbon though.  Plenty of H2O and O2, some He3.

So if you want to get carbon to the moon, liquid methane is the easiest choice (317kgC/m^3, 0.75 carbon fraction), then kerosene is the next easy choice (860kg/m^3, 0.85 mass fraction), but the best in still liquid form would be a kerosene/graphite slurry that's 40% graphite by volume..  That gets you 1300kg/m^3 of carbon and 0.95 mass fraction of carbon.  That'd be far easier than transporting carbon bricks.

Just for visualization, a 2300t full load of fuel on a StarshipV4 contains 375t of carbon (16.3%), which is two starship full to get that slurry to LEO (versues 500t of LCH4, or 3 loads).    Not a huge delta (33%).

I suspect that you would initially just ship LCH4 to the surface of the moon and then eventually if you need high volume of fuel on or near the moon you'd ship it in as a kerosene/graphite slurry and make LCH4 on the moon (along with the LOX).

Still we're talking about $120/kg (12x the cost to LEO) for carbon delivered to the moon assuming full reuse everywhere on the chain.   That's pretty spendy.  Can one sustain a long term colony that has to import all its carbon?

[Lampyridae]

And yes, I know there's no carbon on the moon so no ISRU, we have to ship in fuel.  It changes almost nothing, as the fuel requirements are lower, you still have to transfer the fuel to the landed ship, landing ships could blow up your fuel depot, etc etc etc - all problems we'll have on Mars.   In fact it's simpler, there's no ISRU to depend on.

I would suggest that there is no readily identifiable carbon on the moon that can be economically accessed at this time. Eventually, in a few decades, carbon deposits from asteroid impactors  will be located. IF it becomes economically feasible, they will be mined.

It would make no sense to incorporate that future possibility into current plans. There are all kinds of possible resources that are conjecture at this time that should not be part of serious planning.

So the moon doesn't have carbonate rocks? Like limestone?

https://en.wikipedia.org/wiki/Geology_of_the_Moon#Lunar_rocks

I guess not. Mostly  olivine, pyroxene, and plagioclase feldspar (anorthite).

It is estimated that there are about a half-dozen sizable (>1km) CC asteroid impact sites on the Moon, given bombardment rates and the odds of hitting just slow enough at the right angle, but we don't have the appropriate remote sensing data to know where they might be. Lunar Trailblazer might have provided the appropriate high-res NIR data but it was lost.

Once these potential CC impact sites are discovered, there may be more significant C and N resources on the Moon than the 10¹⁰ kg polar ice:

Still, if a substantial fraction of C and N were to remain trapped within the solid projectile fragments, despite transient heating to above their vaporisation temperatures, then our models predict ∼1.2 × 10¹⁰ kg of C and ∼1.2 × 10⁹ kg of N for the same 1-km diameter CI impactor; the corresponding values for a CM impactor are ∼5.5 × 10⁹ kg and ∼2.3 × 10⁸ kg, respectively.

Plus, they would be much easier to access than painfully baking out several hundred square km of ice. They'd literally just be a sort of ore lying on or just beneath the surface. This of course is all well into the future.

https://www.sciencedirect.com/science/article/pii/S0032063324000692

[TheRadicalModerate]

There is oxygen on the moon.  Oxygen has more mass and can be produced on the moon.  Methane and even hydrogen can be brought to the moon.  Both have far less mass than oxygen.  Bring methane as part of the "cargo" and refill with oxygen on the moon to use to get back to either the Artemis station or an L1 station. 

Ok, from what you guys are saying, there will be a need at whatever fuel depot is used or multiple depots, for refrigeration equipment as well as shading.  Neither is impossible.  Shading can be done with solar panels.  The electricity produced can re-cool the fuel and oxygen stored at the depot.

Enough fuel stored at say a modified Starship depot, to completely refuel a lunar Starship or a Mars bound Starship.  For lunar, another fuel depot at the Artemis station can again refuel a lunar Starship for landing and return to the station.

Again, nothing is impossible.  Timing is the key.  Eventually a large slow spinning to create artificial gravity fuel depot could be built that could store oxygen, methane, and hydrogen for any spacecraft to stop and refuel for outbound ships.  Only other options are to use hypergolic fuels that can be stored and transferred for in space only hypergolic powered spacecraft or nuclear powered spacecraft.

No carbon though.  Plenty of H2O and O2, some He3.

So if you want to get carbon to the moon, liquid methane is the easiest choice (317kgC/m^3, 0.75 carbon fraction), then kerosene is the next easy choice (860kg/m^3, 0.85 mass fraction), but the best in still liquid form would be a kerosene/graphite slurry that's 40% graphite by volume..  That gets you 1300kg/m^3 of carbon and 0.95 mass fraction of carbon.  That'd be far easier than transporting carbon bricks.

Just for visualization, a 2300t full load of fuel on a StarshipV4 contains 375t of carbon (16.3%), which is two starship full to get that slurry to LEO (versues 500t of LCH4, or 3 loads).    Not a huge delta (33%).

I suspect that you would initially just ship LCH4 to the surface of the moon and then eventually if you need high volume of fuel on or near the moon you'd ship it in as a kerosene/graphite slurry and make LCH4 on the moon (along with the LOX).

Still we're talking about $120/kg (12x the cost to LEO) for carbon delivered to the moon assuming full reuse everywhere on the chain.   That's pretty spendy.  Can one sustain a long term colony that has to import all its carbon?

We're now even more wildly off-topic than before.

Returning to the OP, which had the following snippet from the SpaceX press release:

Since the contract was awarded, we have been consistently responsive to NASA as requirements for Artemis III have changed and have shared ideas on how to simplify the mission to align with national priorities. In response to the latest calls, we’ve shared and are formally assessing a simplified mission architecture and concept of operations that we believe will result in a faster return to the Moon while simultaneously improving crew safety.

Emphasis mine.

So you may think that going straight to a base with ISRU-based refueling is the best course, but it doesn't appear that SpaceX agrees with you.

FWIW, I'd love to see a real base, complete with pads that allowed EDL-capable Starships to land without debris problems, and maybe even directly on Raptors.  I'd also love to see it have enough power to produce LOX via reduction of the metal oxides in regolith.  But expecting that to happen before test landings using HLS is just crazy talk.

[InterestedEngineer]

We're now even more wildly off-topic than before.

Returning to the OP, which had the following snippet from the SpaceX press release:

Since the contract was awarded, we have been consistently responsive to NASA as requirements for Artemis III have changed and have shared ideas on how to simplify the mission to align with national priorities. In response to the latest calls, we’ve shared and are formally assessing a simplified mission architecture and concept of operations that we believe will result in a faster return to the Moon while simultaneously improving crew safety.

Emphasis mine.

So you may think that going straight to a base with ISRU-based refueling is the best course, but it doesn't appear that SpaceX agrees with you.

FWIW, I'd love to see a real base, complete with pads that allowed EDL-capable Starships to land without debris problems, and maybe even directly on Raptors.  I'd also love to see it have enough power to produce LOX via reduction of the metal oxides in regolith.  But expecting that to happen before test landings using HLS is just crazy talk.

First, I've already said the first missions will be refueled with fuel launched from LEO.  Yes we did go wildly off topic speculating about long term stuff, but no ISRU - probably not for the first decade.

Second, the way I parse "faster return to the moon" is "faster than the real schedule", not "faster than the fake schedule we have been telling congress and fooling ourselves with".