Author Topic: Artemis III and refuel in LEO  (Read 13635 times)

Offline jfri

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Artemis III and refuel in LEO
« on: 12/15/2023 02:56 pm »
I have encountered claim that 17 fuel refill missions is needed to get the lunar lander from LEO to the moon

This is obviously wrong. From what I have seen it's about one refuel. But in what way has he got it wrong ?
And exactly is this going to be done during the Artemis III mission ?

Offline VSECOTSPE

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Re: Artemis III and refuel in LEO
« Reply #1 on: 12/15/2023 08:34 pm »

So the Lunar Starship lander will refuel once from a Starship depot in Earth orbit before heading to the Moon. But that depot requires somewhere between high single digit (according to Musk/SpaceX) and high teen (according to a recent NASA presentation) Starship tanker launches/visits to fuel up.

No one knows the exact number of tanker launches/visits required because it depends on the performance of a lot of things that are still in development:  the exact performance of Starship tankers to orbit (how much propellant can go up per launch), the exact performance of the Starship depot (how much stored propellant does it lose per unit of time), and the launch cadence of Starship tankers (how long does the Starship depot have to wait between Starship tanker visits).  Even those in the know — even SpaceX and NASA leadership — have only estimates and ranges on these figures with which to make educated guesses at this time.

The guy in that YouTube video is making an overly simplistic argument about complexity and reliability.  He is right that a lunar lander that requires refueling is more complex _operationally_ than one that does not.  But there’s also systems complexity.  With only one type of engine, a stainless steel structure, gobs of mass margin, etc., Starship is a relatively simple system compared to, say, SLS, which uses three different engines each launch (and arguably four or five different engines over its life-cycle), requires advanced welding techniques, has little margin to spare if any significant payload rides with Orion, etc.  There’s also more to reliability than operational and systems complexity.  Experience and redundancy also play huge roles.  A system that can launch a lot, like Starship is intended to, provides a lot more workforce experience and a lot more opportunities to recover from accidents than a system that launches only once every year or two, like Orion/SLS.  If someone wanted to do a real engineering analysis, instead of speak to a few slides with some folksy wisdom, the trade offs would be much more complex and nuanced than what is depicted in that video (which really shows no trade offs at all).

The video also ignores a few other hard realities that have nothing to do with complexity and reliability.

One, if we’re ever going send humans to Mars, or frankly, do more at the Moon than Apollo did, we need heavy launch vehicles (HLVs) with high launch rates.  NASA’s own Mars Design Reference Mission 5.0 (NASA’s last comprehensive study of a human Mars mission architecture) requires at least 7-8 HLV launches, and somewhere in the teens depending on transit propulsion choices, to assemble and fuel the Mars mission stack in Earth orbit over the course of about a year and a half.  At best, SLS launches once every year or so — it’s utterly incapable of doing the Mars job.  Even if we ignore Mars, the best case Orion/SLS launch rate will be about half that of Apollo, and likely worse when Murphy inevitably rears his ugly head.  We may not need an HLV that has as high a launch rate as Starship plans for.  But we sure as heck need something better than what we’ve got in SLS.

Two, mass cryogenic propellant storage, transfer, and management is on the critical path to Mars and pretty much everywhere else we’d like to send astronauts.  And it’s probably on the critical path to substantive lunar activities like in situ propellant production from ice or regolith as well.  You don’t take a vacation in the family car by hitching an 18-wheel tank truck filled with gas to that car.  You gas up along the way.  (Or if you’re a explorer or settler, you graze your horse or oxen along the way; you don’t carry a barn’s worth of feed.)  Outside of very limited, Apollo-type missions, the same is even more true of human space missions because of the triple tyranny of Earth’s high gravity, thick atmosphere, and the rocket equation.  Again, most of the HLV launches in NASA’s own Mars DRM 5.0 were for fueling the mission stack in Earth orbit.  We have to learn and perfect that capability, or we’re stuck with sub-Apollo missions ad infinitum.

Third, budgets and costs matter.  Orion/SLS has consumed most of NASA’s human space exploration budget for the last decade and a half and will continue to do so for the foreseeable future just to get a few astronauts into lunar orbit once every year or two.  That leaves little for the other, arguably as critical if not more important, elements of a lunar architecture.  When NASA finally went to procure a lander, Lunar Starship was the only proposal that NASA could afford with the paltry less than a couple billion dollars that was left over after Orion/SLS had been consuming (and is still projected to consume) $4-5 billion-plus annually.   It took a couple more years and much lobbying before NASA could afford to contract for a second lander.

To close, there’s just a lot of unreality ignored reality in that video.  If a refuelable industry lander is too operationally complex, then where does the money come from to afford a non-refuelable one?  The last time NASA tried such an architecture under Constellation a couple decades ago, the cost estimators were spitting out $20-25B estimates to develop the Altair lander alone.  If a refuelable industry lander is too operationally complex, then where do we get the second SLS launch to put a big Altair-like lander up in parallel with an Orion capsule when SLS is struggling just to get to one or two launches per year?  If a refuelable industry lander is too operationally complex now, then when, where, and with what money are we going to prove out these refueling technologies and techniques that are one the critical path to Mars and substantive lunar activities, anyway?  Do we really think a launch vehicle that is as complex, expensive, and rarely flown as SLS is the path to those future architectures?  (Or heck, even a good way to redo Apollo compared to the simpler Saturn V?)

Engineering analyses and life in general are a lot more complex and nuanced than what a keynote or YouTube presenter and their handful of slides would have you believe.  There is no single, simple, good solution, only trade offs between more and less worse options.  You have to place your bets and takes your chances.  But whatever you do, don’t buy the snake oil from luncheon speaker and YouTube hucksters.
« Last Edit: 12/15/2023 08:37 pm by VSECOTSPE »

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Re: Artemis III and refuel in LEO
« Reply #2 on: 12/15/2023 09:33 pm »
Caveat: I didn't watch the video.

Beyond that, I first want to express appreciation for your commentary, both here and in general on the forum: the views are consistently well-informed and well articulated.

Nit-picking at one part of your commentary, particularly relevant to the "17 tanker missions" claim:
[...] if we’re ever going send humans to Mars, or frankly, do more at the Moon than Apollo did, we need heavy launch vehicles (HLVs) with high launch rates.

Yes, and I particularly appreciate your use of the term HLV. In that category I would put Falcon Heavy, DIV-H, SLS Block 1 and perhaps a few others in the past or, like New Glenn, in the near future.

Precisely because of on-orbit propellant transfer, we don't absolutely need super-heavy launch vehicles. What we need are launch systems that either through high individual flight capacity and/or through high flight rates provide large amounts of mass delivered to orbit inexpensively.

How to get there is still an open question. For optimal efficiency rockets and rocket engines "want" to be big. For optimal manufacturability there's a constraint on vehicle and engine size. If the metric were "tons delivered to orbit per week" it's still unclear what size or type vehicle can do that at the lowest cost..
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Offline jfri

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Re: Artemis III and refuel in LEO
« Reply #3 on: 12/15/2023 11:25 pm »

So the Lunar Starship lander will refuel once from a Starship depot in Earth orbit before heading to the Moon. But that depot requires somewhere between high single digit (according to Musk/SpaceX) and high teen (according to a recent NASA presentation) Starship tanker launches/visits to fuel up.

And my question is how many Moon going Starship can be refueled by the filled Starship depot ?
Also from what I understand is what we are seing in the presentation below is the Starship capsule plus the second rocket stage
https://www.spacex.com/vehicles/starship/
Will they somehow fill the rocket stage with new fuel ?
Also this is stated as unmanned tasks. Is that not very complicated and risky ?

Offline eeergo

Re: Artemis III and refuel in LEO
« Reply #4 on: 12/16/2023 09:03 am »
This forum section is about SLS.

There's a Moon Missions section two places down which has threads dealing with HLS Option A (i.e. Moon Starship / "Moonship").

In the Starship section down in the SpaceX subforum there's also some threads dealing with concepts for deport architectures for this spacecraft.

Mods please move accordingly.
-DaviD-

Offline VSECOTSPE

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Re: Artemis III and refuel in LEO
« Reply #5 on: 12/17/2023 03:52 pm »
And my question is how many Moon going Starship can be refueled by the filled Starship depot?

The Starship Depot is essentially a gas station.  It can refuel as many Lunar Starship missions as its service life allows.  (I don’t how many that is.)

If you’re asking how many Lunar Starships could be refueled at a Starship Depot before the depot needs refueling, it may be two.  Don’t quote this, but I’ve seen numbers bandied about that the Starship Depot will hold ~2500t of propellant.  The wet mass of a Starship at launch is ~1200t.  So if a Lunar Starship is also refueled with 1200t of propellant after reaching orbit, a full Starship Depot could do that twice before needing refueling itself.

In practice, this probably won’t happen.  Gas stations don’t normally wait until their underground tanks are nearly empty before refilling and neither will a Starship Depot.

Quote
Also from what I understand is what we are seing in the presentation below is the Starship capsule plus the second rocket stage

A Starship launch consists of two stages.  The first stage is called Superheavy and it is intended to return to the launch site, like a Falcon 9 first stage can do.

The second stage is the Starship proper.  It does not have a separate capsule (or third stage, transit stage, etc.).  The entire Starship second stage goes to orbit, and if it needs to go farther, it refuels at a Starship Depot.  A Lunar Starship lander is essentially a Starship second stage that refuels at a Starship Depot and is modified to go farther, land on, and take off from the lunar surface.

Quote
Will they somehow fill the rocket stage with new fuel ?

Yes.  We do smaller versions of this today.  The stationkeeping capability of the International Space Station is refueled via Progress visits.  You can think of Starship Depot as a much bigger, cryogenic version of that operation.

Quote
Also this is stated as unmanned tasks. Is that not very complicated and risky ?

Most human space flight tasks are run from the ground and/or by computers.  For example, rendezvous and docking at the ISS can be completely automated (current Dragon capsules) or involve berthing, capture, and docking via the astronaut-operated Canadarm (original Dragon capsules).

The devil is always in the details.  US automated rendezvous and docking systems have very few (any?) anomalies, whereas the Russian KURS systems had quite a few.

Offline VSECOTSPE

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Re: Artemis III and refuel in LEO
« Reply #6 on: 12/17/2023 04:10 pm »
Yes, and I particularly appreciate your use of the term HLV. In that category I would put Falcon Heavy, DIV-H, SLS Block 1 and perhaps a few others in the past or, like New Glenn, in the near future.

Precisely because of on-orbit propellant transfer, we don't absolutely need super-heavy launch vehicles. What we need are launch systems that either through high individual flight capacity and/or through high flight rates provide large amounts of mass delivered to orbit inexpensively.

How to get there is still an open question. For optimal efficiency rockets and rocket engines "want" to be big. For optimal manufacturability there's a constraint on vehicle and engine size. If the metric were "tons delivered to orbit per week" it's still unclear what size or type vehicle can do that at the lowest cost..

I agree.  At the small end of the spectrum, in theory a depot could even be refueled with a steady stream of something like this:

https://www.thespacereview.com/article/544/1

https://en.m.wikipedia.org/wiki/Aquarius_(rocket)

https://newspaceeconomy.ca/2023/12/06/aquarius-the-ultra-low-cost-space-launch-that-never-was/?amp=1

https://www.thespaceshow.com/loral-aquarius

Online Robotbeat

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Re: Artemis III and refuel in LEO
« Reply #7 on: 12/17/2023 04:46 pm »
And my question is how many Moon going Starship can be refueled by the filled Starship depot?

The Starship Depot is essentially a gas station.  It can refuel as many Lunar Starship missions as its service life allows.  (I don’t how many that is.)

If you’re asking how many Lunar Starships could be refueled at a Starship Depot before the depot needs refueling, it may be two.  Don’t quote this, but I’ve seen numbers bandied about that the Starship Depot will hold ~2500t of propellant.  The wet mass of a Starship at launch is ~1200t.  So if a Lunar Starship is also refueled with 1200t of propellant after reaching orbit, a full Starship Depot could do that twice before needing refueling itself.


So actually I don’t think the depot can do 2 lunar starship fills, at least not for a round trip.

If we look at the LEO-NHRO-Surface-NHRO-disposal delta-v, it’s actually about 9.6km/s. A filled out Starship (ie with 100tonnes of furnishings/cargo/etc) can do “only” 6.9km/s. Where does that 2.7km/s come from?
-lower cargo/furnishings for HLS than 100t
-slower transit (doesn’t help much since you have cryogen boiloff to keep in mind)
-reduced delta-v for disposal burn than the assumed 0.45km/s.

Even with all that, there’s still likely a 2-2.5km/s gap to make up.

So the solution is the refueling happens in a GTO-like orbit, not LEO. Alternatively, the Depot acts like a stage and boosts HLS to a GTO-like orbit.

With such a strategy, the 2500t of capacity is enough to refuel HLS *and* put it in a near-GTO-like elliptical orbit. But not to do so twice. (On the other hand, you could still do 2 LEO refuelings of one-way cargo HLSes.)
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Re: Artemis III and refuel in LEO
« Reply #8 on: 12/17/2023 05:39 pm »
-reduced delta-v for disposal burn than the assumed 0.45km/s.

First, thanks for sharing the NASA slide comparing LLO and NHRO delta-v requirements! Where's that from?
It implicitly makes the assumption that "all delta-v is equal." While true for Starship-like systems that rely solely on methalox in a single-stage vehicle, it could be deceiving for systems that use a combination of e.g. hydrolox and storable propellants for different phases of the mission and discard some stages along the way.

Regarding the disposal burn from NHRO, are you estimating that delta-v to escape, or to DRO?
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Re: Artemis III and refuel in LEO
« Reply #9 on: 12/17/2023 05:43 pm »
-reduced delta-v for disposal burn than the assumed 0.45km/s.

First, thanks for sharing the NASA slide comparing LLO and NHRO delta-v requirements! Where's that from?
It implicitly makes the assumption that "all delta-v is equal." While true for Starship-like systems that rely solely on methalox in a single-stage vehicle, it could be deceiving for systems that use a combination of e.g. hydrolox and storable propellants for different phases of the mission and discard some stages along the way.

Regarding the disposal burn from NHRO, are you estimating that delta-v to escape, or to DRO?
I’m just assuming the NHRO to Earth burn in that slide is equivalent to a worst case disposal delta-v requirement.

The slide shows the decomposition of the delta-v, so you can of course pick a different Isp for each leg if you like.
« Last Edit: 12/17/2023 05:49 pm by Robotbeat »
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Re: Artemis III and refuel in LEO
« Reply #10 on: 12/18/2023 01:57 pm »
-reduced delta-v for disposal burn than the assumed 0.45km/s.

First, thanks for sharing the NASA slide comparing LLO and NHRO delta-v requirements! Where's that from?
It implicitly makes the assumption that "all delta-v is equal." While true for Starship-like systems that rely solely on methalox in a single-stage vehicle, it could be deceiving for systems that use a combination of e.g. hydrolox and storable propellants for different phases of the mission and discard some stages along the way.

Regarding the disposal burn from NHRO, are you estimating that delta-v to escape, or to DRO?
I’m just assuming the NHRO to Earth burn in that slide is equivalent to a worst case disposal delta-v requirement.

The slide shows the decomposition of the delta-v, so you can of course pick a different Isp for each leg if you like.

Ah, yes, disposal via Earth atmospheric re-entry is almost certainly a good "worst case" estimate.

And (for the benefit of other readers) answering the question about the origin of the presentation slide: Jason Crusan!
https://www.nasa.gov/wp-content/uploads/2016/05/20181207-crusan-gateway-reduced-v4tagged.pdf
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Offline jfri

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Re: Artemis III and refuel in LEO
« Reply #11 on: 12/18/2023 02:34 pm »
And my question is how many Moon going Starship can be refueled by the filled Starship depot?

If you’re asking how many Lunar Starships could be refueled at a Starship Depot before the depot needs refueling, it may be two.  Don’t quote this, but I’ve seen numbers bandied about that the Starship Depot will hold ~2500t of propellant.  The wet mass of a Starship at launch is ~1200t.  So if a Lunar Starship is also refueled with 1200t of propellant after reaching orbit, a full Starship Depot could do that twice before needing refueling itself.

Is it possible that the starship don't need to be fully tanked for going to the Moon ?
Is double amount fuel sufficient for going to Mars ? They claim that Starship can reach Mars aand even beyond that.

Offline VSECOTSPE

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Re: Artemis III and refuel in LEO
« Reply #12 on: 12/18/2023 03:19 pm »
Is it possible that the starship don't need to be fully tanked for going to the Moon ?

Lunar Starship will need some amount of refueling in Earth orbit to reach the Moon.  We don’t know yet whether that will require a complete topping of the tanks or something less than that.

Quote
Is double amount fuel sufficient for going to Mars ? They claim that Starship can reach Mars aand even beyond that.

Starship’s concept of operation at Mars requires refueling on the Martian surface in order to return to Earth.  Given a power source, carbon dioxide in the Martian atmosphere can be extracted and turned into methane and oxygen.  Starships headed to Mars will either carry a power source and processing equipment with them or land near the same from earlier missions.

As a rough rule of thumb, it takes about the same amount of energy (or more) to reach Earth orbit as it does to travel from Earth orbit to most targets of interest for human space flight in the solar system.

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Re: Artemis III and refuel in LEO
« Reply #13 on: 12/18/2023 03:31 pm »
And my question is how many Moon going Starship can be refueled by the filled Starship depot?

If you’re asking how many Lunar Starships could be refueled at a Starship Depot before the depot needs refueling, it may be two.  Don’t quote this, but I’ve seen numbers bandied about that the Starship Depot will hold ~2500t of propellant.  The wet mass of a Starship at launch is ~1200t.  So if a Lunar Starship is also refueled with 1200t of propellant after reaching orbit, a full Starship Depot could do that twice before needing refueling itself.

Is it possible that the starship don't need to be fully tanked for going to the Moon ?
Is double amount fuel sufficient for going to Mars ? They claim that Starship can reach Mars aand even beyond that.
Even for one-way missions to both destinations, it actually takes less propellant to send stuff to land on Mars than it does the Moon, due to Mars’ atmosphere.

Measured by propulsive delta-v, travel to Mars is “closer” than traveling to the Moon. Doubly so for round trip missions because volatiles are more readily available on Mars than the Moon (we’ve already demonstrated making oxygen and CO fuel on Mars from the Martian CO2 atmosphere), cutting the delta-v potentially in half.

The Delta-V from LEO to NHRO and to the moon’s surface and back to NHRO is about the same as the delta-v from LEO to Mars’ surface and back to Mars orbit.

So once SpaceX demonstrates Artemis 3 and 4 plus successful Earth recovery of a Starship from orbit, they basically are ready for Mars (uncrewed to start).
« Last Edit: 12/18/2023 03:33 pm by Robotbeat »
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Offline jfri

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Re: Artemis III and refuel in LEO
« Reply #14 on: 12/18/2023 04:26 pm »
And my question is how many Moon going Starship can be refueled by the filled Starship depot?

If you’re asking how many Lunar Starships could be refueled at a Starship Depot before the depot needs refueling, it may be two.  Don’t quote this, but I’ve seen numbers bandied about that the Starship Depot will hold ~2500t of propellant.  The wet mass of a Starship at launch is ~1200t.  So if a Lunar Starship is also refueled with 1200t of propellant after reaching orbit, a full Starship Depot could do that twice before needing refueling itself.

Is it possible that the starship don't need to be fully tanked for going to the Moon ?
Is double amount fuel sufficient for going to Mars ? They claim that Starship can reach Mars aand even beyond that.
Even for one-way missions to both destinations, it actually takes less propellant to send stuff to land on Mars than it does the Moon, due to Mars’ atmosphere.

Measured by propulsive delta-v, travel to Mars is “closer” than traveling to the Moon. Doubly so for round trip missions because volatiles are more readily available on Mars than the Moon (we’ve already demonstrated making oxygen and CO fuel on Mars from the Martian CO2 atmosphere), cutting the delta-v potentially in half.

The Delta-V from LEO to NHRO and to the moon’s surface and back to NHRO is about the same as the delta-v from LEO to Mars’ surface and back to Mars orbit.

So once SpaceX demonstrates Artemis 3 and 4 plus successful Earth recovery of a Starship from orbit, they basically are ready for Mars (uncrewed to start).

Two things come to my mind.
Moon gravity is less than Mars
Mars atmosphere is very thin. Does that not limit aerobraking significantly ?

Offline whitelancer64

Re: Artemis III and refuel in LEO
« Reply #15 on: 12/18/2023 04:43 pm »
And my question is how many Moon going Starship can be refueled by the filled Starship depot?

If you’re asking how many Lunar Starships could be refueled at a Starship Depot before the depot needs refueling, it may be two.  Don’t quote this, but I’ve seen numbers bandied about that the Starship Depot will hold ~2500t of propellant.  The wet mass of a Starship at launch is ~1200t.  So if a Lunar Starship is also refueled with 1200t of propellant after reaching orbit, a full Starship Depot could do that twice before needing refueling itself.

Is it possible that the starship don't need to be fully tanked for going to the Moon ?
Is double amount fuel sufficient for going to Mars ? They claim that Starship can reach Mars aand even beyond that.
Even for one-way missions to both destinations, it actually takes less propellant to send stuff to land on Mars than it does the Moon, due to Mars’ atmosphere.

Measured by propulsive delta-v, travel to Mars is “closer” than traveling to the Moon. Doubly so for round trip missions because volatiles are more readily available on Mars than the Moon (we’ve already demonstrated making oxygen and CO fuel on Mars from the Martian CO2 atmosphere), cutting the delta-v potentially in half.

The Delta-V from LEO to NHRO and to the moon’s surface and back to NHRO is about the same as the delta-v from LEO to Mars’ surface and back to Mars orbit.

So once SpaceX demonstrates Artemis 3 and 4 plus successful Earth recovery of a Starship from orbit, they basically are ready for Mars (uncrewed to start).

Two things come to my mind.
Moon gravity is less than Mars
Mars atmosphere is very thin. Does that not limit aerobraking significantly ?

Mars' atmosphere is thin, but it is sufficient to reduce most of Starship's velocity. After reentry Starship will only need approximately 1 km/s dV to land.
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Offline TrevorMonty

Re: Artemis III and refuel in LEO
« Reply #16 on: 12/19/2023 04:38 pm »



Precisely because of on-orbit propellant transfer, we don't absolutely need super-heavy launch vehicles. What we need are launch systems that either through high individual flight capacity and/or through high flight rates provide large amounts of mass delivered to orbit inexpensively.


Something F9R has well and truly proven.
Most of mass any BLEO mission is fuel, dry mass of vehicles isn't that great unless wanting to place skyscraper on lunar surface .
20mt to LEO is more than enough for dry mass of crew OTV, crew lander,  in space tankers and depots.

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Re: Artemis III and refuel in LEO
« Reply #17 on: 12/19/2023 04:56 pm »



Precisely because of on-orbit propellant transfer, we don't absolutely need super-heavy launch vehicles. What we need are launch systems that either through high individual flight capacity and/or through high flight rates provide large amounts of mass delivered to orbit inexpensively.

But economies of scale are real. That's the reason container ships have grown ever larger even though the size of a container has not changed, or why supertankers grew to ridiculously large sized before finally running into physical limits. The measure for tanker rockets will be total cost/kg of delivered propellant.

Something F9R has well and truly proven.
Most of mass any BLEO mission is fuel, dry mass of vehicles isn't that great unless wanting to place skyscraper on lunar surface .
20mt to LEO is more than enough for dry mass of crew OTV, crew lander,  in space tankers and depots.

Offline VSECOTSPE

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Re: Artemis III and refuel in LEO
« Reply #18 on: 12/19/2023 06:38 pm »
But economies of scale are real. That's the reason container ships have grown ever larger even though the size of a container has not changed, or why supertankers grew to ridiculously large sized before finally running into physical limits. The measure for tanker rockets will be total cost/kg of delivered propellant.

Economies of scale are real, but they can take the form of physical dimensions or of quantity (or both).  Throughput is what matters in the end.  You can try to build the biggest, most capable HLV with the tech base you’ve got, but if it can only puts 70-130t into LEO once every year or two (cough...SLS...cough), you’re better off going with a less capable HLV that can put 60t to LEO 5+ times a year for 300t+ annually (cough...F9H actually did or will do this in 2023...cough).

Also, infrastructure, nature, and neighbors put limitations on physical size.  Yeah, there are some really big supertankers, but they can only visit certain ports.  If they’re honest, Airbus will tell you that the A380 was a mistake.  Australians can run several trailers behind their tractors, but you can’t do that on US roads.  Etc.

To be clear, I have no idea if Starship will prove too big or launch too infrequently or something else.  I’m just saying that in the abstract, big is not always better.  NASA human space flight has paid dearly by not heeding that advice and doing the analysis before going down blind alleys on STS size, Orion size, Ares V, and now SLS.

FWIW...

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Re: Artemis III and refuel in LEO
« Reply #19 on: 12/19/2023 06:45 pm »
But economies of scale are real. That's the reason container ships have grown ever larger even though the size of a container has not changed, or why supertankers grew to ridiculously large sized before finally running into physical limits. The measure for tanker rockets will be total cost/kg of delivered propellant.

Economies of scale are real, but they can take the form of physical dimensions or of quantity (or both).  Throughput is what matters in the end.  You can try to build the biggest, most capable HLV with the tech base you’ve got, but if it can only puts 70-130t into LEO once every year or two (cough...SLS...cough), you’re better off going with a less capable HLV that can put 60t to LEO 5+ times a year for 300t+ annually (cough...F9H actually did or will do this in 2023...cough).

Also, infrastructure, nature, and neighbors put limitations on physical size.  Yeah, there are some really big supertankers, but they can only visit certain ports.  If they’re honest, Airbus will tell you that the A380 was a mistake.  Australians can run several trailers behind their tractors, but you can’t do that on US roads.  Etc.

To be clear, I have no idea if Starship will prove too big or launch too infrequently or something else.  I’m just saying that in the abstract, big is not always better.  NASA human space flight has paid dearly by not heeding that advice and doing the analysis before going down blind alleys on STS size, Orion size, Ares V, and now SLS.

FWIW...
That's the reason I said "The measure for tanker rockets will be total cost/kg of delivered propellant." All of your points get rolled into total cost/kg. As of now, we are beginning to see limits on the number of launches per year from a site. This scarcity will begin to increase the cost of using a launch slot, in which case bigger is better, aside from any intrinsic economies of scale.

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Re: Artemis III and refuel in LEO
« Reply #20 on: 12/19/2023 09:08 pm »
I would prefer a metric involving rate, e.g. dollars per ton per week,  $/(t⋅wk). Less focus on a ton of cargo delivered; more on the rate at which tons of cargo are delivered.
« Last Edit: 12/19/2023 09:14 pm by sdsds »
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Re: Artemis III and refuel in LEO
« Reply #21 on: 12/19/2023 10:12 pm »
I would prefer a metric involving rate, e.g. dollars per ton per week,  $/(t⋅wk). Less focus on a ton of cargo delivered; more on the rate at which tons of cargo are delivered.
In the context of the thread title, neither of these is valid. There is a specific mission and it has specific requirements, e.g.,  a certain amount of propellant available in a certain orbit at a certain date and time. The metric is the bid price to fulfill those requirements.

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Re: Artemis III and refuel in LEO
« Reply #22 on: 12/20/2023 03:28 am »
But economies of scale are real. That's the reason container ships have grown ever larger even though the size of a container has not changed, or why supertankers grew to ridiculously large sized before finally running into physical limits. The measure for tanker rockets will be total cost/kg of delivered propellant.

Economies of scale are real, but they can take the form of physical dimensions or of quantity (or both).  Throughput is what matters in the end.  You can try to build the biggest, most capable HLV with the tech base you’ve got, but if it can only puts 70-130t into LEO once every year or two (cough...SLS...cough), you’re better off going with a less capable HLV that can put 60t to LEO 5+ times a year for 300t+ annually (cough...F9H actually did or will do this in 2023...cough).

Also, infrastructure, nature, and neighbors put limitations on physical size.  Yeah, there are some really big supertankers, but they can only visit certain ports.  If they’re honest, Airbus will tell you that the A380 was a mistake.  Australians can run several trailers behind their tractors, but you can’t do that on US roads.  Etc.

To be clear, I have no idea if Starship will prove too big or launch too infrequently or something else.  I’m just saying that in the abstract, big is not always better.  NASA human space flight has paid dearly by not heeding that advice and doing the analysis before going down blind alleys on STS size, Orion size, Ares V, and now SLS.

FWIW...
That's the reason I said "The measure for tanker rockets will be total cost/kg of delivered propellant." All of your points get rolled into total cost/kg. As of now, we are beginning to see limits on the number of launches per year from a site. This scarcity will begin to increase the cost of using a launch slot, in which case bigger is better, aside from any intrinsic economies of scale.
I'm not sure that we're near the limits of number of launches per year. The FAA and the range have drastically increased launch rate capacity, higher than they had even planned for this year. And SpaceX has not chosen to invest in more droneships or upper stage reuse, even though both would probably help increase launch rate... Because they believe Starship is the future and those other investments would either distract from Starship (opportunity cost) or they wouldn't have time to pay back given that they think Starship will be ready soon. Maybe we're seeing a limit to the *rate of increase* in launches per year.
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Online DanClemmensen

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Re: Artemis III and refuel in LEO
« Reply #23 on: 12/20/2023 03:45 am »
But economies of scale are real. That's the reason container ships have grown ever larger even though the size of a container has not changed, or why supertankers grew to ridiculously large sized before finally running into physical limits. The measure for tanker rockets will be total cost/kg of delivered propellant.

Economies of scale are real, but they can take the form of physical dimensions or of quantity (or both).  Throughput is what matters in the end.  You can try to build the biggest, most capable HLV with the tech base you’ve got, but if it can only puts 70-130t into LEO once every year or two (cough...SLS...cough), you’re better off going with a less capable HLV that can put 60t to LEO 5+ times a year for 300t+ annually (cough...F9H actually did or will do this in 2023...cough).

Also, infrastructure, nature, and neighbors put limitations on physical size.  Yeah, there are some really big supertankers, but they can only visit certain ports.  If they’re honest, Airbus will tell you that the A380 was a mistake.  Australians can run several trailers behind their tractors, but you can’t do that on US roads.  Etc.

To be clear, I have no idea if Starship will prove too big or launch too infrequently or something else.  I’m just saying that in the abstract, big is not always better.  NASA human space flight has paid dearly by not heeding that advice and doing the analysis before going down blind alleys on STS size, Orion size, Ares V, and now SLS.

FWIW...
That's the reason I said "The measure for tanker rockets will be total cost/kg of delivered propellant." All of your points get rolled into total cost/kg. As of now, we are beginning to see limits on the number of launches per year from a site. This scarcity will begin to increase the cost of using a launch slot, in which case bigger is better, aside from any intrinsic economies of scale.
I'm not sure that we're near the limits of number of launches per year. The FAA and the range have drastically increased launch rate capacity, higher than they had even planned for this year. And SpaceX has not chosen to invest in more droneships or upper stage reuse, even though both would probably help increase launch rate... Because they believe Starship is the future and those other investments would either distract from Starship (opportunity cost) or they wouldn't have time to pay back given that they think Starship will be ready soon. Maybe we're seeing a limit to the *rate of increase* in launches per year.
Of course. SpaceX has chosen to go big. The counter-argument seems to be that lots of smaller LVs will be or would have been  more cost-effective. I don't see it. SpaceX also claims that Starship (specifically including its "stage 0") is designed for full and rapid reuse. They seem to have about a 5-year head start. They have designed for multiple launches per day from a single pad, which translates to at least 600 launches per year from each pad. I just don't see a path for a competitor to beat them in sending propellant to orbit, by any measure. Certainly not in the Artemis III context.
« Last Edit: 12/20/2023 05:20 am by DanClemmensen »

Offline TrevorMonty

Re: Artemis III and refuel in LEO
« Reply #24 on: 12/20/2023 03:52 pm »


But economies of scale are real. That's the reason container ships have grown ever larger even though the size of a container has not changed, or why supertankers grew to ridiculously large sized before finally running into physical limits. The measure for tanker rockets will be total cost/kg of delivered propellant.

Economies of scale are real, but they can take the form of physical dimensions or of quantity (or both).  Throughput is what matters in the end.  You can try to build the biggest, most capable HLV with the tech base you’ve got, but if it can only puts 70-130t into LEO once every year or two (cough...SLS...cough), you’re better off going with a less capable HLV that can put 60t to LEO 5+ times a year for 300t+ annually (cough...F9H actually did or will do this in 2023...cough).

Also, infrastructure, nature, and neighbors put limitations on physical size.  Yeah, there are some really big supertankers, but they can only visit certain ports.  If they’re honest, Airbus will tell you that the A380 was a mistake.  Australians can run several trailers behind their tractors, but you can’t do that on US roads.  Etc.

To be clear, I have no idea if Starship will prove too big or launch too infrequently or something else.  I’m just saying that in the abstract, big is not always better.  NASA human space flight has paid dearly by not heeding that advice and doing the analysis before going down blind alleys on STS size, Orion size, Ares V, and now SLS.

FWIW...
That's the reason I said "The measure for tanker rockets will be total cost/kg of delivered propellant." All of your points get rolled into total cost/kg. As of now, we are beginning to see limits on the number of launches per year from a site. This scarcity will begin to increase the cost of using a launch slot, in which case bigger is better, aside from any intrinsic economies of scale.
I'm not sure that we're near the limits of number of launches per year. The FAA and the range have drastically increased launch rate capacity, higher than they had even planned for this year. And SpaceX has not chosen to invest in more droneships or upper stage reuse, even though both would probably help increase launch rate... Because they believe Starship is the future and those other investments would either distract from Starship (opportunity cost) or they wouldn't have time to pay back given that they think Starship will be ready soon. Maybe we're seeing a limit to the *rate of increase* in launches per year.
Of course. SpaceX has chosen to go big. The counter-argument seems to be that lots of smaller LVs will be or would have been  more cost-effective. I don't see it. SpaceX also claims that Starship (specifically including its "stage 0") is designed for full and rapid reuse. They seem to have about a 5-year head start. They have designed for multiple launches per day from a single pad, which translates to at least 600 launches per year from each pad. I just don't see a path for a competitor to beat them in sending propellant to orbit, by any measure. Certainly not in the Artemis III context.

Need someone to pay for missions that use all the propellant delivered to orbit. At this stage its just odd NASA manned lunar mission which requires use of SLS+Orion.

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Re: Artemis III and refuel in LEO
« Reply #25 on: 12/20/2023 04:33 pm »


But economies of scale are real. That's the reason container ships have grown ever larger even though the size of a container has not changed, or why supertankers grew to ridiculously large sized before finally running into physical limits. The measure for tanker rockets will be total cost/kg of delivered propellant.

Economies of scale are real, but they can take the form of physical dimensions or of quantity (or both).  Throughput is what matters in the end.  You can try to build the biggest, most capable HLV with the tech base you’ve got, but if it can only puts 70-130t into LEO once every year or two (cough...SLS...cough), you’re better off going with a less capable HLV that can put 60t to LEO 5+ times a year for 300t+ annually (cough...F9H actually did or will do this in 2023...cough).

Also, infrastructure, nature, and neighbors put limitations on physical size.  Yeah, there are some really big supertankers, but they can only visit certain ports.  If they’re honest, Airbus will tell you that the A380 was a mistake.  Australians can run several trailers behind their tractors, but you can’t do that on US roads.  Etc.

To be clear, I have no idea if Starship will prove too big or launch too infrequently or something else.  I’m just saying that in the abstract, big is not always better.  NASA human space flight has paid dearly by not heeding that advice and doing the analysis before going down blind alleys on STS size, Orion size, Ares V, and now SLS.

FWIW...
That's the reason I said "The measure for tanker rockets will be total cost/kg of delivered propellant." All of your points get rolled into total cost/kg. As of now, we are beginning to see limits on the number of launches per year from a site. This scarcity will begin to increase the cost of using a launch slot, in which case bigger is better, aside from any intrinsic economies of scale.
I'm not sure that we're near the limits of number of launches per year. The FAA and the range have drastically increased launch rate capacity, higher than they had even planned for this year. And SpaceX has not chosen to invest in more droneships or upper stage reuse, even though both would probably help increase launch rate... Because they believe Starship is the future and those other investments would either distract from Starship (opportunity cost) or they wouldn't have time to pay back given that they think Starship will be ready soon. Maybe we're seeing a limit to the *rate of increase* in launches per year.
Of course. SpaceX has chosen to go big. The counter-argument seems to be that lots of smaller LVs will be or would have been  more cost-effective. I don't see it. SpaceX also claims that Starship (specifically including its "stage 0") is designed for full and rapid reuse. They seem to have about a 5-year head start. They have designed for multiple launches per day from a single pad, which translates to at least 600 launches per year from each pad. I just don't see a path for a competitor to beat them in sending propellant to orbit, by any measure. Certainly not in the Artemis III context.

Need someone to pay for missions that use all the propellant delivered to orbit. At this stage its just odd NASA manned lunar mission which requires use of SLS+Orion.
Nope, not "all the propellant". You only need someone to pay enough for the mission to be profitable. If your tanker can lift 20 tonne or 150 tonne, but the customer only needs 10 tonne, that's still OK if you charge enough.  You only get into trouble if the customer needs 20 tonne and you can only deliver 19 tonne in one launch.

Since we appear to be generalizing beyond Artemis III, there is also the possibility of long-term depot storage. Send up full loads to depot for whatever tanker you have and sell the customer whatever amount they want from depot. (There is the tiny little problem that the depot's orbit may not match the customer requirement...)

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Re: Artemis III and refuel in LEO
« Reply #26 on: 12/21/2023 11:01 am »
Isn't there is another downside of smaller launchers to assemble a "structure" is that you have to design and link the sections in space, which is still a labour intensive operation?

The US main structure part of ISS could have been assembled with a few (5?) Saturn V class launches. Instead of maybe 20 Shuttles (structure)  and lots of supporting flights to connect things up.

Then you end up with a more complex end product.
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Re: Artemis III and refuel in LEO
« Reply #27 on: 12/28/2023 03:30 am »
Isn't there is another downside of smaller launchers to assemble a "structure" is that you have to design and link the sections in space, which is still a labour intensive operation?

Assembling modules in space has not appeared to be very time consuming, or about an hour of time for modules that use the Common Berthing Mechanism (see the Post-launch section here on Wikipedia)

Quote
The US main structure part of ISS could have been assembled with a few (5?) Saturn V class launches. Instead of maybe 20 Shuttles (structure)  and lots of supporting flights to connect things up.

Instead of looking backwards to the Saturn V, which was out of production when the ISS was approved to be built, instead look at the alternatives we have today which include the Falcon 9 and larger launchers like New Glenn, Vulcan, and Starship. But of course NASA doesn't want to build ISS v2.0, so this really doesn't answer any important questions...  ;)

Quote
Then you end up with a more complex end product.

If you ignore launch costs, then sure, maybe they should have used Saturn V rockets to launch much bigger ISS modules. And maybe NASA could use the SLS to launch up-sized modules, but both of those rockets were/are VERY expensive. The SLS costs $4B per launch, whereas you could launch Falcon 9 something like 50 times for the same cost as one SLS. So the overall cost would be less going with commodity launchers instead of the unique (and very costly) SLS.

And of course there are new launchers coming online soon that will have payload volumes larger than Falcon 9, so we don't lack the ability to build larger structures in space, we lack the MONEY.

So while the engineering viewpoint is always to maximize something, when you're talking about doing things in space we need to focus more on VALUE - how much we can do with the limited money we have.
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline TheRadicalModerate

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Re: Artemis III and refuel in LEO
« Reply #28 on: 12/28/2023 09:24 pm »
And my question is how many Moon going Starship can be refueled by the filled Starship depot?

The Starship Depot is essentially a gas station.  It can refuel as many Lunar Starship missions as its service life allows.  (I don’t how many that is.)

If you’re asking how many Lunar Starships could be refueled at a Starship Depot before the depot needs refueling, it may be two.  Don’t quote this, but I’ve seen numbers bandied about that the Starship Depot will hold ~2500t of propellant.  The wet mass of a Starship at launch is ~1200t.  So if a Lunar Starship is also refueled with 1200t of propellant after reaching orbit, a full Starship Depot could do that twice before needing refueling itself.


So actually I don’t think the depot can do 2 lunar starship fills, at least not for a round trip.

If we look at the LEO-NHRO-Surface-NHRO-disposal delta-v, it’s actually about 9.6km/s. A filled out Starship (ie with 100tonnes of furnishings/cargo/etc) can do “only” 6.9km/s. Where does that 2.7km/s come from?
-lower cargo/furnishings for HLS than 100t
-slower transit (doesn’t help much since you have cryogen boiloff to keep in mind)
-reduced delta-v for disposal burn than the assumed 0.45km/s.

Even with all that, there’s still likely a 2-2.5km/s gap to make up.

So the solution is the refueling happens in a GTO-like orbit, not LEO. Alternatively, the Depot acts like a stage and boosts HLS to a GTO-like orbit.

With such a strategy, the 2500t of capacity is enough to refuel HLS *and* put it in a near-GTO-like elliptical orbit. But not to do so twice. (On the other hand, you could still do 2 LEO refuelings of one-way cargo HLSes.)

A few things:

1) The slide you have is for a non-BLT trip to lunar orbit.  BLT drops the delta-v for orbital insertion from 450m/s down to below 100m/s, and increases the TLI by 100-200m/s.  If you have good boiloff control (a BLT takes 60-120 days), there's some savings here.

Somewhere, there's a very similar slide with BLT options on it.  Too lazy to look for it right now, but its format is very similar to the one you attached, so I suspect it's from the same group.

2) Any portion of the conops containing humans is going to have increased flight performance reserves.  I can only guess what these are.  Two different levels of guesses:
a) I'd guess that non-crew segments required allowance for 2-3σ underperformance, while crewed segments would be at 3-4σ.
b) Since we don't know the performance distribution, I usually use 0.75% extra delta-v for non-crew segments, and 1.5% for crewed segments.  Note that by expressing these as percentages, they scale cleanly as other performance-affecting parameters vary.

3) You also have to include boil-off, sump losses, and ullage gas losses.  Boil-off is highly dependent on where the vehicle is parked.  Sump losses are anybody's guess--I've been using 1t of Starship, which is probably conservative.  I've been figuring ullage losses conservatively at 6bar for Starship, but a good case can be made for 3bar.  3bar saves somewhere between 2-4t, depending on how big you decide the lunar Starship tankage is.

4) Using these assumptions, an LSS dry mass of 95t, crew module of 15t, 2t up-mass and 1t down-mass ("up" and "down" being earth-relative), and Isp=369s average (assumes 50% throttle of one of the center RSLs), a single LEO refueling of a 1200t LSS doesn't even come close to being acceptable.  I've worked out the following use cases in this spreadsheet:

a) A 1200t Option A test article, assuming only 200m/s of delta-v after ascent, to make it as cheap as possible.  Launch-LEO-refuel-TLI BLT-NRHO-LS-ascentTest-crash.

b) A 1200t tankage LSS, single refueling in a low HEEO (the max HEEO reachable with no LEO refueling): Launch-HEEO-refuel-TLI BLT-NRHO-loiter-LS-NRHO. 

c) Two refuelings for a 1200t LSS, one in LEO and a second in a higher HEEO: Launch-LEO-refuel-HEEO-refuel-TLI BLT-NRHO-loiter-LS-NRHO.

d) A single refueling of an LSS with at least 1500t tankage: Launch-LEO-refuel-TLI BLT-NRHO-loiter-LS-NRHO.  I've been assuming that this has the same dry mass, since just rearranging the domes will still yield an LSS "garage" that's about 2m high, which should be fine for crew ops and small unpressurized payloads.

e) RB, you once argued that a 1200t LSS could refuel only in LEO if its dry mass was extremely low.  I modeled that:  dry+crew module would have to be 92t to work.  Not impossible, but unlikely, IMO.  Launch-LEO-refuel-NRHO-loiter-LS-NRHO.

f) Expendable Starships for HDL or CLPS missions, Launch-LEO-refuel-LS.  They're cheaper than reusing them.

g) An LSS used as an orbital transfer vehicle, with up to 4 crew brought up by an F9/D2, with the D2 capable of loitering uncrewed in LEO for up to 6 weeks.  This is an SLS/Orion replacement:  LEO-refuel-NRHO-LEOpropulsive.

h) When Starship becomes crew-certified for launch and EDL, it seems reasonable to look at an EDL-capable Starship (vanilla Starship with all the LSS features, re-engineered to support translunar reentry with 1500t tankage--call it 145t dry mass).  Launch (with crew)-LEO-refuel-TLI fast-LS-LLO-refuel-EDL.
 
i) It seems reasonable that SpaceX will based the LSS on the v2 Starship, which will have some stretch to the tanks, including outer mould line changes.  I haven't modeled this; I can't guess how the stretch plus mass savings will net out in terms of dry mass, so I didn't do this one.

j) All of these scenarios assume that all the necessary prop magically appears in the depot just before the LSS needs it.  In reality, it'll be accumulated over a period of at least weeks, more likely months, and we have no idea how much boiloff will occur during that accumulation period.  I've included a pretty-close-to-worst-case boiloff estimate for a 90-day campaign, which is then tweaked to come out to an integral number of tanker launches.  I can have almost 4t/day of boiloff and still do a mission that requires only 12 tankers.

6) I've posted this before, but it's relevant to this thread:  NASA did a trade study a few years back, which had extremely precise delta-v budgets for all phases of cislunar flight.  They took it down, but I squirreled away a copy hereHere's a Google sheet with the same info.

Note that I'm assuming that these numbers do not include FPR.  If they do, then I'm being too conservative by quite a bit.


Offline TheRadicalModerate

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Re: Artemis III and refuel in LEO
« Reply #29 on: 12/28/2023 09:58 pm »

To close, there’s just a lot of unreality ignored reality in that video.  If a refuelable industry lander is too operationally complex, then where does the money come from to afford a non-refuelable one? 

In addition, it should be noted that the current Blue Origin / National Team architecture drank the entire giant tub of Kool-Aid wrt to refueling.  Its architecture is now essentially equivalent to SpaceX's, albeit with a set of much smaller vehicles.
« Last Edit: 12/29/2023 05:06 am by TheRadicalModerate »

Offline TheRadicalModerate

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Re: Artemis III and refuel in LEO
« Reply #30 on: 12/28/2023 10:30 pm »
And my question is how many Moon going Starship can be refueled by the filled Starship depot?

If you’re asking how many Lunar Starships could be refueled at a Starship Depot before the depot needs refueling, it may be two.  Don’t quote this, but I’ve seen numbers bandied about that the Starship Depot will hold ~2500t of propellant.  The wet mass of a Starship at launch is ~1200t.  So if a Lunar Starship is also refueled with 1200t of propellant after reaching orbit, a full Starship Depot could do that twice before needing refueling itself.

Is it possible that the starship don't need to be fully tanked for going to the Moon ?
Is double amount fuel sufficient for going to Mars ? They claim that Starship can reach Mars aand even beyond that.

Depends on the mission.  As it turns out, for the Option A (Artemis III) mission, an HLS Starship with only 1200t of tankage not only needs to be fully tanked, it needs to be fully tanked in a highly eccentric earth orbit with a considerably higher apogee than LEO.  Refueling in HEEO adds additional complexity.

I think the answer to this is that the HLS Starship will get more tankage, so it's able to take on about 1500t of prop.  Then it can do LEO-NRHO-LS-NRHO on one tank.

When the HLS Starship is reusable (this is the so-called Sustainable Lunar Transportation contract, and would likely first occur on Artemis VI), the missions go NRHO-refuel-LS-NRHO, and the Starship only needs about 520t of prop.  But that prop needs to be brought to NRHO from Earth, and that requires almost 1800t of prop to get it there and return the tanker back to Earth.

Note that it's actually cheaper, in terms of propellant that has to be brought to LEO, to send a new HLS Starship from LEO for each mission.  That essentially makes them expendable, but that might turn out to be more economical.  An extra couple of tankers almost certainly costs less than a new HLS Starship for every mission, but there are other considerations:

1) It's going to be a while before SpaceX can judge the longevity of an HLS Starship.  Will lunar dust degrade its performance and reliability?  How will its avionics and solar panels stand up to years in NRHO, with its more intense radiation environment?  What happens when its propellant tanks boil completely dry?  What kinds of consumables need to be resupplied?  All of these issue may require the HLS Starship to be overdesigned, which increases its cost.

2) The other major problem is that there's no way (currently) to reload the HLS Starship with large, unpressurized cargo for the next mission.  You can bring pressurized cargo up and transfer it through the Orion docking tunnel, but that constrains its dimensions and weight.  On the other hand, if the HLS Starship launches from Earth, it can carry large payloads like rovers, habs, etc., which can then be deployed by the crew.  That's a pretty big advantage.
« Last Edit: 12/28/2023 10:41 pm by TheRadicalModerate »

Offline tbellman

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Re: Artemis III and refuel in LEO
« Reply #31 on: 12/29/2023 01:58 pm »
2) The other major problem is that there's no way (currently) to reload the HLS Starship with large, unpressurized cargo for the next mission.  You can bring pressurized cargo up and transfer it through the Orion docking tunnel, but that constrains its dimensions and weight.  On the other hand, if the HLS Starship launches from Earth, it can carry large payloads like rovers, habs, etc., which can then be deployed by the crew.  That's a pretty big advantage.

It is true there is no way to transfer large amounts of cargo, whether pressurized or unpressurized, to the HLS Starship once it is in space.  But that is not a problem, never mind a major problem.

For it to be a problem, there would need to a) exist any such large cargo, and b) be a benefit to bring said cargo on the HLS lander together with the crew.

On the contrary, sending large cargo on dedicated cargo landers is both the plan, and the better solution.  If NASA and partners ever manages to get the money to do so, that is.

Rovers, both pressurized like the expected JAXA rover, and unpressurized like the not-yet-awarded Lunar Terrain Vehicle, are better delivered before the crew arrives.  That way they can be tested without crew, and be used for reconnaissance, exploration, and/or other scientific examinations before crew arrival.  (And consistent with NASA trying to not buy a rover, but contracting rover-as-a-service, it will be the responsibility of the LTV provider to deliver their rover to the Moon.)

Habitat modules are unlikely to even fit in the "garage" of the HLS Starship and fit through the planned door (approximately 3m×3m), and are certainly not going to fit on the planned elevator.  A dedicated cargo ship can deliver much larger modules.  (Besides, there's currently no money in sight for separate habitats.)

Likewise any power systems: better to deliver and deploy them robotically before sending crew on the expensive and rare (once per year) SLS+Orion.

Offline TheRadicalModerate

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Re: Artemis III and refuel in LEO
« Reply #32 on: 12/29/2023 07:36 pm »
On the contrary, sending large cargo on dedicated cargo landers is both the plan, and the better solution.  If NASA and partners ever manages to get the money to do so, that is.

Rovers, both pressurized like the expected JAXA rover, and unpressurized like the not-yet-awarded Lunar Terrain Vehicle, are better delivered before the crew arrives.  That way they can be tested without crew, and be used for reconnaissance, exploration, and/or other scientific examinations before crew arrival.  (And consistent with NASA trying to not buy a rover, but contracting rover-as-a-service, it will be the responsibility of the LTV provider to deliver their rover to the Moon.)

Habitat modules are unlikely to even fit in the "garage" of the HLS Starship and fit through the planned door (approximately 3m×3m), and are certainly not going to fit on the planned elevator.  A dedicated cargo ship can deliver much larger modules.  (Besides, there's currently no money in sight for separate habitats.)

Likewise any power systems: better to deliver and deploy them robotically before sending crew on the expensive and rare (once per year) SLS+Orion.

Fair point that very large systems aren't going to fit in the garage, and that dedicated HDL or CLPS missions are the way to go there.  But there's almost certainly a wide array of equipment that's too big to go through an IDSS docking ring and safely stow in microgravity, but small enough to be stowed in the garage, using payload processing best practices, and deployed via the elevator.  That class of stuff could probably be batched together and transported with one large-ish HDL mission, but it'll likely be cheaper to co-manifest it with a crewed mission.

(BTW: We haven't seen what an automated deployment of a large module off of a cargo LSS would look like.  I suspect they'll blow the nose and fairing off early in the flight, then land with the payload exposed.  That still leaves the question of how you get a payload that's 30m above the ground deployed:  Internal crane with counterweight or counter-cantilever?  Ramp?  Super-gigando elevator, also with counterweight?  External crane?)

And I still think it's a while before NASA and SpaceX agree on the lifecycle of an SLT-class LSS.  A crewed LSS is obviously going to a lot more expensive in terms of quality control than an HDL/CLPS version, but how much of that expense will be driven by making it reusable vs. expendable?

Offline tbellman

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Re: Artemis III and refuel in LEO
« Reply #33 on: 12/29/2023 09:12 pm »
Fair point that very large systems aren't going to fit in the garage, and that dedicated HDL or CLPS missions are the way to go there.  But there's almost certainly a wide array of equipment that's too big to go through an IDSS docking ring and safely stow in microgravity, but small enough to be stowed in the garage, using payload processing best practices, and deployed via the elevator.  That class of stuff could probably be batched together and transported with one large-ish HDL mission, but it'll likely be cheaper to co-manifest it with a crewed mission.

Do you have any concrete examples of such equipment?  (And remember that it needs to be equipment that NASA would like to use within the Artemis program, and can potentially afford.)

Quote from: TheRadicalModerate
(BTW: We haven't seen what an automated deployment of a large module off of a cargo LSS would look like.  I suspect they'll blow the nose and fairing off early in the flight, then land with the payload exposed.  That still leaves the question of how you get a payload that's 30m above the ground deployed:  Internal crane with counterweight or counter-cantilever?  Ramp?  Super-gigando elevator, also with counterweight?  External crane?)

On the last page of the Starship Users Guide there is a picture of Starship delivering two or possibly four Space Exploration Vehicles to the Moon, using an elevator.  (There exists a larger version of that picture, but I'm too lazy to find a copy right now.)  Granted, that is an early concept picture, and the SEV probably doesn't count as a large module in this context.

Beyond that, you probably have to think about how large and heavy individual modules will be.  A 30 tonne module should not be too difficult to hoist down using an internal crane.  And I think it will be quite some time until we are sending larger singular pieces of cargo to the Moon.

Offline Phil Stooke

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Re: Artemis III and refuel in LEO
« Reply #34 on: 12/29/2023 09:25 pm »
"Do you have any concrete examples of such equipment?  (And remember that it needs to be equipment that NASA would like to use within the Artemis program, and can potentially afford.)"

Not difficult to think of things like this once we get past the first few landings.  The build-up to Artemis Base Camp would require lots of infrastructure: solar power towers, habitat components, regolith-moving equipment, big rovers, ISRU plants, science equipment like telescopes or large drills.  That's just plucked out of my cranium with one of those Claw toys, so I'm sure more could be added.

Offline TheRadicalModerate

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Re: Artemis III and refuel in LEO
« Reply #35 on: 12/29/2023 10:21 pm »
Do you have any concrete examples of such equipment?  (And remember that it needs to be equipment that NASA would like to use within the Artemis program, and can potentially afford.)

Nothing specific, but I can think of all kinds of science experiments that would do poorly being manhandled through the docking tunnel, and might need a while to equilibrate from 1bar to a few nPa before the crew could calibrate and/or use them in the time allotted for the mission.  Also, stuff that has to survive the vibration and shock loads of a lunar landing is better integrated onto PAFs on the ground, rather than being stowed in a crew volume.

Think about stuff that was deployed unpressurized from an Apollo LM descent stage and you'll have the right scale.

Quote
On the last page of the Starship Users Guide there is a picture of Starship delivering two or possibly four Space Exploration Vehicles to the Moon, using an elevator.  (There exists a larger version of that picture, but I'm too lazy to find a copy right now.)  Granted, that is an early concept picture, and the SEV probably doesn't count as a large module in this context.

Yeah, I put about as much confidence in that picture as I put in the picture of the ITS sitting on a jovian icy moon.  That was back in the days of the stubby landing legs.

Don't get me wrong:  I think there are solutions.  I just don't know what they are.  It's a fairly important missing piece before you can start thinking about the dividing line between pressurized cargo, garage-deployed cargo, and HDL/CLPS-deployed cargo.

Quote
Beyond that, you probably have to think about how large and heavy individual modules will be.  A 30 tonne module should not be too difficult to hoist down using an internal crane.  And I think it will be quite some time until we are sending larger singular pieces of cargo to the Moon.

At the risk of drifting even further off-topic, my guess is that we won't see a piece of deployable cargo much bigger than 10t in the Artemis timeframe.  Anything bigger than that, the Starship is the cargo, with whatever you want built into the payload bay, never to be removed.  There may be deployable power and heat rejection, or maybe those are just hookups to a nascent base infrastructure.  But deploying massive equipment is going to take more than just a nascent base; it'll need a real one, with decent port facilities.

Offline Ciber

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Re: Artemis III and refuel in LEO
« Reply #36 on: 01/14/2024 04:10 am »
For very large payloads, I Imagine you could manage something that involves an unpressurized cargo bay with large hatches on either end that allow crane segments to telescope out, with one side acting as a counterweight. Ideally, I think you use a container filled with smaller cargo as the counterweight, that way once the main payload is lowered you can unpack and lower individual smaller counterweight packages. Maybe a Starship variant with extra large landing legs for stability?

Re: Artemis III and refuel in LEO
« Reply #37 on: 04/19/2024 07:45 pm »
For whatever it's worth, I think we're being a bit too harsh on Destin (the guy in the video in the first post). Yes his points about the lander and the complexity of the mission are dubious, and rather backwards looking / Apollo-centric.

But his overall point is, "Hey, if this program is supposed to land humans on the Moon in 2 years, why is there still so much uncertainty?", and that's an extremely valid point which needs to be made more often.
« Last Edit: 04/19/2024 07:46 pm by JEF_300 »
Wait, ∆V? This site will accept the ∆ symbol? How many times have I written out the word "delta" for no reason?

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