ESA needs to save NASA’s Moon plans.

[tater]

2 minutes ago, wumpus said:

Expecting rational project goals from them doesn't make sense, and the rush to build turns out to be a strength of Apollo and not a weakness (NASA had no reason to listen to every senator's pet requirement).

I'd disagree with the first part, their goals were entirely rational, but not the same as "our" goals of sustainable humans in space, Moon bases, or what have you. Their goals were accomplished—they increased shareholder value.

"Old space" gets thrown around, but they are not somehow bad or less innovative because they have some "old" mindset, they have an entirely different incentive structure. They are large, publicly held companies. They can't play around in this market with "build it and they will come," that works for mass markets, but not a niche like this. They will always have to operate based on what can generate revenue within some fairly short time horizon. Apollo was the once in a generation (possibly one ever) situation where they had some cost limitations, but pretty close to a free hand to build a vehicle.

I want to see BO succeed because I want to see 2 players in the situation where they are building spaceflight capability for no business reason whatsoever. In the meantime, there is only SpaceX operating in this way.

WRT to the refilling ops and the current HLS, and the OP concept of an Ariane core as SLS S2, if Super Heavy can fly at all—forget recovery and reuse—making any kooky kerbal SLS variants is pointless, just use expendable SH and an expendable "starship" as S2. SS/SH with an expended upper stage is already on the table, and such an upper stage would be substantially lighter than SS and could be used to assemble a vehicle in LEO.

[wumpus]

2 hours ago, tater said:

"Old space" gets thrown around, but they are not somehow bad or less innovative because they have some "old" mindset, they have an entirely different incentive structure. They are large, publicly held companies. They can't play around in this market with "build it and they will come," that works for mass markets, but not a niche like this. They will always have to operate based on what can generate revenue within some fairly short time horizon. Apollo was the once in a generation (possibly one ever) situation where they had some cost limitations, but pretty close to a free hand to build a vehicle.

Old space (and the entire military industrial complex typically operates this way) create new rockets as a government funded project.  If they tried to build a rocket for some "fairly short time horizon", they'd be "new space" (like Orbital long before Spacex).  Things like Atlas, Delta, and SLS simply aren't designed with the "old space" contractors paying the bills and hoping to make money  with in the future.  Much of the reason is that you can never know which way NASA is going to go: every 2 years a "new" Congress gets elected (with almost always the same faces), and the committee's that control NASA's (and DoD launches) budget changes.  So they might want a completely different rocket, and be willing to pay a competitor to design one.  So while the Pegasus might be the type of rocket that could fit this "return on investment in a short horizon", it wasn't "old space"

Even the Falcon 9's design budget was paid for by NASA . Although, considering what a shoestring budget it was, it probably never occurred to NASA that they were going to design a medium lift orbital rocket with just those funds.  Pretty sure spacex is far too big to do it again, although I'd be curious to see what the design costs of the Neutron are.

Disclosure:  I currently work for a military industrial complex company who oddly enough, *does* design products on its own budget.  I was fairly shocked at the concept, but it allows for modular products that can be reconfigured to sell for multiple roles instead of forced into a narrow role to meet an entire committee's requirements.  It helps that they are relatively small: don't try this with a plane, ship, or tank.

[Exoscientist]

On 6/10/2022 at 11:48 AM, StrandedonEarth said:

Is the Ariane 5 engine:

Vacuum optimized?

Man-rated?

Capable of aerial start?

(probably not in order of importance)

 As discussed in the first part of my cited blog post, ESA believes the Vulcain on the Ariane 5/6 can be made air startable as an upper stage since that was required for the proposed Liberty rocket:

Budget Moon Flights: Ariane 5 as SLS upper stage.

http://exoscientist.blogspot.com/2013/07/budget-moon-flights-ariane-5-as-sls.html

 Note the Liberty rocket was intended to also be crewed so the Ariane would have had to be man-rateable:

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

 Robert Clark

[Exoscientist]

On 6/10/2022 at 11:49 AM, Beccab said:

That's wrong: the EUS makes SLS go from block 1 to block 1b, not block 2. That part is for the advanced SRB.Which the very phrase quoted calls unlikely, and even if it were to happen, what's the issue? SLS ain't going to fly more than once a year, ever"Hey ESA, do you have some free time? I need someone to build me an upper stage, all you need to do is to make an entirely new engine, reinforce the structure to make it suitable for the flight, slap on it an adapter and invent a way to send it to Cape Canaveral. You already have the tanks for Ariane 5, so it should be pretty easy. Love, NASA.
P.S. You need to pay for it too, and preferibly assemble it before 2026 so that I can maintain my schedule. Thanks!""It's how Apollo did it so it's right" isn't a great argument, considering you're talking about a program that could only do the definition itself of a flags & footprints series of mission before being cancelled for its unsustainable costs. Add to that the fact that the only way Lunar Orbit Rendezvous was considered better than EOR (i.e. multiple launches) was in that it was more likely to fulfill the lunar landing goal in this decade despite costing quite a bit more, and it's a pretty meaningless phraseThat's not how it works, at all. This is the least thought out part of the article (which isn't thought out a lot by itself), so I will focus on this in part specifically.
Given that you haven't, let's start by putting some math here:
- ICPS is 13 meters high, and the ariane 5 core is 31m; replacing one with the other will bring the full stack up of, at the very least, 18 meters
- the full SLS is now 116 meters high, or five more than Block II Cargo. This means a higher launch tower, which means a higher cost both to develop and per launch, but the article makes no mention of how this would reduce expenses so let's just ignore money, as there's more absurd parts here.
You have now obtained an almost a hundred and twenty meters high monstruosity (probably by 2030 or so, very optimistically) that has the capability to launch Orion by itself in a TLI, enter NRHO and then... do nothing. That's because in the whole article you forgot to adress the premise itself: where's the lander? In those 116 meters there's no free space whatsoever for nothing but some cubesats, surely not for a lander that can go NRHO -> lunar surface -> NRHO. You need to make some space for it by making the rocket higher and adding a long interstage to comanifest the lander.
However, you run into a second issue of this nonsensical architecture: the Ariane 5's radius is much smaller than the one of SLS, so small that it's only 15 mere centimeters more than Orion. With EUS you'd have a 9 meter fairing in which to fit your comanifested lander, but now, you have to make it fit into 5 meters instead.
The LEM had almost 7 meters to fit in thanks to the fantastic S-IVB, and it had to only go to LLO; this one needs to go all the way to NRHO thanks to Orion's absimal service module. Let's say that this adds only 15 more meters; this is more or less the height of the National Team lander, which couldn't fit at all into this fairing diameter, but let's keep it because I'm an optimistic person - maybe ESA can help NASA by finding two more meters inside a 5 meters fairing.
Your monstruosity is now 131 meters tall; thankfully the VAB doors are 138 meters high, so that's not a problem, right? But unfortunately, this rocket doesn't have wheels, and can only move above one of those NASA crawlers that carried shuttles, saturns and now SLS. That's an issue, because the 6-8 meters of the crawler make your rocket go above the top of the door; add to that the fact that you *also* need the Mobile Tower specifically built for this rocket, and you're probably a full 10 meters above the limit.
Now you have a 145ish meters rocket on the pad, a semi destroyed VAB door and a few thousand tons of LH2 and LOX waiting to send four brave people to the moon. What's still missing, however, is the lander: cause again, you started with the premise that you need to do this to solve the lander problem, but there's no lander that could work with this architecture. I don't mean one that is being built, mind you: there are zero lunar lander designs with enough fuel to go from NRHO to the moon and back that fit into a 5 x 14 fairing. There's exactly 0 chances that someone could design, build and test a crewed lander by 2025 starting from scratch - hell, I doubt someone could do that by 2028 by the time EUS will probably launch. 
I'm sorry but, this post really wasn't thought out much

 Correct the SLS with the Exploration Upper Stage(EUS) was to be the SLS 1B. The version that also has upgraded SRB’s was SLS 2.  Still the SLS 1B was supposed to be 365 feet high:

 The difference in height between the  Interim Cryogenic Propulsion Stage(ICPS) currently on the SLS and the Ariane 5/6 would put it at only a couple of meters beyond the 365 feet planned for SLS 1B, and well less than the height of the Vehicle Assembly Building 456 feet high doors.

The width of the Ariane 5 is actually slightly more than the interim cryogenic stage now on the SLS so that’s not a problem. 

The ESA is supposed to be partners with NASA in the Artemis lunar plans, and the ESA is even more interested in Moon colonization than NASA. I then argue they would be amenable to adapting the Ariane for the SLS if it made a Moon lunar flight possible. Note also they were interested in providing the upper stage for the Liberty rocket that was intended to be crew delivery vehicle:

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

  Robert Clark

 

 

On 6/10/2022 at 11:52 AM, RealKerbal3x said:

EUS takes SLS from Block 1 to Block 1B. Block 2 may come later, it includes changes such as composite boosters and upgraded RS-25 engines.

Regardless, EUS is already funded and the first articles are under construction. It's currently planned to fly first on Artemis IV. 

https://www.nasa.gov/exploration/systems/sls/fs/sls.html

….

 

 The development cost of the EUS is still not fully funded. Many knowledgeable industry observers feel it will never be fully funded due to its expense.

  Robert Clark

Edited June 13, 2022 by Exoscientist

[wumpus]

58 minutes ago, Exoscientist said:

 As discussed in the first part of my cited blog post, ESA believes the Vulcain on the Ariane 5/6 can be made air startable as an upper stage since that was required for the proposed Liberty rocket:

Budget Moon Flights: Ariane 5 as SLS upper stage.

http://exoscientist.blogspot.com/2013/07/budget-moon-flights-ariane-5-as-sls.html

 Note the Liberty rocket was intended to also be crewed so the Ariane would have had to be man-rateable:

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

 Robert Clark

Didn't NASA get into the SLS trap by trying to play KSP with existing rockets?

edit: maybe they could get Orbital as the prime for this new rocket.  Orbital has been remarkably successful in putting together rockets out of surplus parts and existing rockets.

Edited June 13, 2022 by wumpus

[tater]

1 hour ago, Exoscientist said:

 The difference in height between the  Interim Cryogenic Propulsion Stage(ICPS) currently on the SLS and the Ariane 5/6 would put it at only a couple of meters beyond the 365 feet planned for SLS 1B, and well less than the height of the Vehicle Assembly Building 456 feet high doors.

The issue IMO would be the MLS. Block 1 and Block 1B require different MLS, so this variant would as well. So another few years and another billion.

[SunlitZelkova]

On 6/12/2022 at 11:48 AM, tater said:

All this is semi-off topic for this thread—though the current Artemis plan with Starship as the lander is a "sustainable" (ish, lol) plan that no improved SLS fixes. If Starship manages to do HLS, SLS is entirely obviated.

I get the point about choosing a more sustainable initial lunar architecture during the Apollo era, but as a counterfactual, I don;t think it holds water. Apollo was precisely what could be done give the political situation in the US. Minus the time limit ("before the decade is out"), Apollo never happens, nor anything more interesting.

Explaining why Apollo was bad was meant to demonstrate why it is not necessarily to be imitated in Artemis as per the OP's argument.

I don't think a sustainable lunar architecture in the Apollo era was possible at all. A lunar landing with no constant nagging and raised eye brows from Congress in the "ideal" world I described wouldn't come around until the 1980s or 1990s.

On 6/12/2022 at 12:38 PM, wumpus said:

The "extended stay missons" (with LM hab) lasted 3 days maximum ("J missions, Apollo 14 & Apollo 15).  I suspect that docking in Earth orbit and flying the entire contraption to the Moon would make more sense.  The real issue is exactly when they could pull resources off Apollo 11 (just getting the boots and flag to the Moon before the USSR) and start building a new hab.  No way they will complete the hab and integration before Apollo gets canceled (regardless of how they plan to deliver the new hab to the Moon.

As far as I know, Saturn 1B was a cheaper and more efficient means to orbit than the Space Shuttle (and Saturn V would have been far superior in assisting the building of ISS, although if it wasn't launched from 1975 to 1985 it would have been effectively impossible to launch at all, thanks to some of those sustainability issues.  No idea how long you could go between launches but it was far less than 10 years).  The sins of sustainability and efficiency were largely political (being easier to cancel than the sunk costs of the Shuttle).  Rushing the job meant that they didn't have the time  to add the bloat in costs and inefficiency of the SLS.  Old space (and the rest of the US military industrial complex) has very weak links between performance and funding.  Expecting rational project goals from them doesn't make sense, and the rush to build turns out to be a strength of Apollo and not a weakness (NASA had no reason to listen to every senator's pet requirement).

 

Extended stay missions referred to the J-class missions with slight improvements to the LM, those were the 3 day maximum ones. What I was talking about was the LM Shelter/Early Lunar Shelter. These would last two weeks to a month.

If they wanted to, I don't think it would have been too economically outlandish to do the LM Shelter instead of Skylab. Apollo would end with a two week mission to the Moon in 1972 instead of another J-class mission. No Skylab though, which might make justifying Space Station Freedom- and thus the ISS- harder in the future.

I disagree that the lack of a decadal goal would have led to delays. X-15 and Mercury are examples of programs that did fine without a date as a goal. In the "ideal" world I described, there would still be a drive to do things before or to match the Soviets, just with no date.

------

Btw, when I say "ideal" I don't mean it is something I think should have happened, merely that it would have been more "sustainable" than Apollo.

I describe this alternate world to point out the problems Apollo had. Of course, these are only problems only as long as one desires for "newer stuff" to happen in space exploration.

Edited June 13, 2022 by SunlitZelkova

[Beccab]

5 hours ago, Exoscientist said:

The width of the Ariane 5 is actually slightly more than the interim cryogenic stage now on the SLS so that’s not a problem

Man sorry but just, no. As the reply you are quoting explaining why that won't work says, the ICPS does not comanifest anything and you can't fit any of the proposed NRHO lunar landers in a 5.4 meters fairing, plus the height problem if you add a large enough interstage. I'm not sure if you read the page long textwall you are quoting, but that's very much not a rebuttal of what I wrote

Edited June 13, 2022 by Beccab

[tater]

A Centaur based lander is a good thing, but there is no way to comanifest one with Orion with the available volume. BTW, if you were to pick a 5.4m hydrolox stage to act as stage 2, why use Ariane 5/6, just use Vulcan's upper stage—which is a 5.4m Centaur.

Anyway, you're still not going to have a stack that is an additional 14m, then stick a Centaur lander on top (sideways, presumably as the XEUS concept was), then Orion. Then you need the whole stack to TLI, and the lander has to do the LOI burn for itself, plus Orion.

Any change to 8.4m tanks means EUS, effectively, so that's off the table for this discussion.

I'm not seeing any possible way to make SLS work as a single stack Moon vehicle (surface mission) unless Orion is dumped. Then the dev cycle includes a lander, and a CSM so that the whole thing works in whatever limited TLI throw it has.

@Exoscientist, IMO, the most important thing that your blog posts lack is specifics on the actual payload, and subsequent throw to TLI. You say 130-150t to LEO. OK, go with that (though the upper stage is then doing substantially more work than ICPS is just to get to parking orbit—which I will completely ignore). Your concept uses an engine with an I_sp of 432-440s. We can look at 130t in LEO to 150t in LEO, largely residuals. Ariane core is 12-14 t, but we need interstage for lander, etc, call it 15t being generous. Orion is ~27t (not counting the LES). So our LEO stack is 130-150t minus 42t for dry mass plus the CSM. That's 88t-108t to play with for the lander, plus residuals in S2 for the TLI burn.

These are masses assuming operation from NRHO. So the min comanifested lander to NRHO is 41t, upper limit 50t.

So now of 88-108t, we have our stage 2 prop reserves as 38t to 47t props for the 130t to LEO estimate, and 58t to 67t for the 150t to LEO estimate.

Try the min mass 2 stage lander. The TLI stack has a dry mass now of 42+41=83t. 47t of props, and we'll use the best case I_sp, 440. Our Ariane in LEO has ~1900m/s dv. Nope, not getting to TLI. For that stack (note I was being really generous saying 65-70t to TLI), the 150t to LEO won't do it either (~2500 m/s). For the Orion plus minimum lander stack to work, we need 83t to TLI, which means ~175t to LEO, any less than that, and a single stack SLS to the lunar surface—assuming Orion—is impossible.

So this idea is a nonstarter for the 2 stage.

The 3 stage lander has a lower minimum mass. Using all the lowest masses, the 130t to LEO does not close (screwed up sleepy last night) at ~2300 m/s (need 3200) even with RL-10. 150t to LEO doesn't work, either, even with a less massive 3 stage lander.

So we need to get the mass to LEO at or very close to 160 tonnes to LEO for any SLS mod to work.

If Orion could be dumped, then all we need is ~50t to TLI (and stock SLS is still garbage, but some variant might work). Then we need a new CSM and a small Apollo style lander.

 

Edited June 13, 2022 by tater

[Exoscientist]

13 hours ago, tater said:

The issue IMO would be the MLS. Block 1 and Block 1B require different MLS, so this variant would as well. So another few years and another billion.

The issue with the Mobile Launch Tower 2 is really bad now with the cost nearly tripling. Is there a way to upgrade the current tower by strengthening the base and making the umbilicals telescoping and rotatable? We could use it in the current form for the upcoming test flight. Then have 3 years to complete modification to upgraded form.

  Robert Clark 

Edited June 13, 2022 by Exoscientist
Clarity

[tater]

41 minutes ago, Exoscientist said:

The issue with the Mobile Launch Tower 2 is really bad now with the cost nearly tripling. Is there a way to upgrade the current tower by strengthening the base and making the umbilicals telescoping and rotatable?

No idea. The height is another huge issue.

Look at my next post, though. The goal was a 1 stack, Apollo-like lunar mission, right? You need maybe 160t to LEO, or better put (SLS not optimized for LEO delivery), you need a bare minimum of 78t to TLI to accomplish that mission goal assuming Orion is the capsule. No way around it.

This math should have been clear to SLS proponents from the start. If going to the lunar surface was ever a thing for SLS, it MUST throw nearly 80t to TLI.

(I used a dry mass for the S2 of 15t, so that could possibly be reduced to make it close at a lower mass to LEO assuming "not Ariane" as S2 has a lower mass.)

Edited June 13, 2022 by tater

[Exoscientist]

10 hours ago, Beccab said:

Man sorry but just, no. As the reply you are quoting explaining why that won't work says, the ICPS does not comanifest anything and you can't fit any of the proposed NRHO lunar landers in a 5.4 meters fairing, plus the height problem if you add a large enough interstage. I'm not sure if you read the page long textwall you are quoting, but that's very much not a rebuttal of what I wrote

 The name of the game is using existing space assets to save on costs. For both NASA and the ESA there are existing propulsion stages and crew modules that could be used to create a compact sized lander that can fit easily within a 5.4 meter fairing.

   Robert Clark

[tater]

13 minutes ago, Exoscientist said:

 The name of the game is using existing space assets to save on costs. For both NASA and the ESA there are existing propulsion stages and crew modules that could be used to create a compact sized lander that can fit easily within a 5.4 meter fairing.

The minimum lander mass is apparently 36 tonnes, per NASA, assuming NRHO staging orbit.

If you want to fly from LLO, then the lander needs to do the LOI burn for the lander/Orion stack. Probably comes out in the wash with the min NRHO lander, so similar, huge lander required.

There is no compact lander where the crew vehicle is the 27 ton Orion CSM.

Edited June 13, 2022 by tater

[tater]

44 minutes ago, Exoscientist said:

 The name of the game is using existing space assets to save on costs. For both NASA and the ESA there are existing propulsion stages and crew modules that could be used to create a compact sized lander that can fit easily within a 5.4 meter fairing.

   Robert Clark

Existing assets to save costs for a lunar surface exploration/base mission in  polar region (aka Artemis)?

If we could spend the SLS money, but NOT on SLS, this would be fairly easy. If SLS is in the mix, then once a year we get crew to NRHO with SLS, and the rest of the year we do our lunar program with "not SLS" and spend less money to do so.

We've had "not SLS" lunar discussions here quite a bit. @sevenperforce did the math on "naked Falcon Heavy" as a TLI stage. Build our components in LEO, rendevous/dock with FH stage 2 in parking orbit, send gear to TLI. Right now "existing" gets pretty difficult, since there are not enough Atlas V vehicles to allow that to be existing, and Vulcan/NG don't exist yet. Ariane 5 is pretty meh, but could contribute. Really is Falcon 9 and FH. If you allow Ariane 6, Vulcan, and New Glenn, then you might as well also allow Staship/Super Heavy (closer to flying than either). If SS/SH works at all, it obviates all the others, because even as an expendable it gets more to LEO than SLS. Minus tiles, flaps, and minus the 4mm steel for reuse (3mm? Thinner?) SS could easily get 160t+ to LEO. Launch lander under a fairing, dock with crew vehicle (Orion?) in LEO, use the hundreds of tons of props for TLI, then LOI. Done.

Edited June 13, 2022 by tater

[RCgothic]

Scrapping Orion, I think they could have made a decent architecture with a launcher capable of 19t to TLI:

 

19t to TLI gets you an Apollo-style LM capable of braking itself into LLO for rendezvous.

19t to TLI gets you a CM *twice* the mass of Apollo, plus a CSM easily capable of LOI, TEI, and lunar rendezvous manoeuvres.

19t to TLI gets you ~4.7t of emplaced downmass in an Apollo-style descent stage for mission extension modules.

 

19t to TLI is within Falcon Heavy's capabilities.

Or the launch vehicle can get away with just 52t all-up to LEO if the departure stage is a Centaur V with 27t of residuals.

 

A much smaller, cheaper, launch vehicle that can launch more often is going to be far more useful overall than SLS.

Edited June 13, 2022 by RCgothic

[tater]

4 minutes ago, RCgothic said:

Scrapping Orion, I think they could have made a decent architecture with a launcher capable of 19t to TLI:

That requires 2 launches for every mission, however.

But, yeah.

[Exoscientist]

On 6/12/2022 at 10:49 AM, tater said:

Won't work for a few reasons.

1. The delta v of that Ariane core stage, depending on what engines (440 vs 432 Isp) and prop mass is something like 4800 m/s. assuming the payload on top of that is ~65 tonnes (70 would be better, drops dv to 4.5 km/s). The payload needs to be ~65+ tons for a 1 launch lunar mission, because the Orion CSM is awful. You'd also then have everything above SLS core down to 5.4m.

Anyway, this puts the Arianne upper stage, plus lander, plus CSM at ~235t. Since SLS core can't put 235t into LEO, the upper stage would have to do some of that, and it's going to use more dv that it will have.

2. Orion. Any single launch architecture that looks more like Apollo that includes Orion needs a huge lander, since Orion can't function like the Apollo CSM. All it can do is fly home, LOI has to be done by the lander—just like Altair, since Orion is from Constellation. BTW, I agree, SLS should have been designed to accomplish, landing on the Moon is the only interesting human mission to cislunar space.

3. As soon as you add a 23.5m stage, the added ~15m of height means that we need a new MLS. That's apparently a few years, and a billion $ (OIG just ripped Bechtel a new one on MLS-2). So delay, plus all the design, testing, etc required.

4. We still need a lander that masses ~38-43t, can do the needed LOI burn, land, then return to LLO, AND fit in a 5.4m interstage.

  I did a preliminary calculation that suggests 60 tons or more payload to TLI with a 175 ton propellant load Ariane 5 as upper stage. Note this means it would not need the upgraded SRB’s. I’d like to see though a Kerbal simulation to confirm that TLI payload though. Payload capability this high expands the possibilities for accomplishing the mission,

 The Orion service module only has about half the propellant load of the service module of Apollo, surprising since it’s a heavier capsule:

European Service Module.

“In comparison with the Apollo command and service module, which previously took astronauts to the Moon, the European Service Module generates approximately twice as much electricity (11.2 kW vs 6.3 kW), weighs nearly 40% less when fully fuelled (15,461 kg,^[24] vs 24,520 kg) and is roughly the same size (4 m in length excluding engine^[25] and 4.1 m vs 3.9 m in diameter) supporting the environment for a slightly (45%) larger habitable volume on the crew module (8.95 m³ vs 6.17 m³) though it will carry 50% less propellant for orbital maneuvers (8,600 kg usable propellant vs 18,584 kg).” 

https://en.wikipedia.org/wiki/European_Service_Module

 I think the lowered propellant load was specifically so that the Orion could do its circumlunar test flight and the interim upper stage had limited payload to TLI capability.

 A new mobile launch tower was always planned for the SLS with EUS so that’s nothing new. In this regard, though I wonder if it would be possible to upgrade the current one rather than constructing a whole new one.

 The lander does not have to be as heavy as the Altair when it is only doing landing to the lunar surface from lunar orbit and back again, The propellant load of the Orion service module though would have at least to be doubled to be able to get the entire stack into lunar orbit.

  Robert Clark

[tater]

2 minutes ago, Exoscientist said:

  I did a preliminary calculation that suggests 60 tons or more payload to TLI with a 175 ton propellant load Ariane 5 as upper stage. Note this means it would not need the upgraded SRB’s. I’d like to see though a Kerbal simulation to confirm that TLI payload though. Payload capability this high expands the possibilities for accomplishing the mission,

Yeah, so not enough. It's possible to imagine a sortie lander—lander as taxi to surface—and you pre-deploy a hab. The problem is abort contingencies because Orion is limited to awful orbits. Any abort has to include phasing issues, so many days of crew support. So a lander that from LLO might only need to have consumables for some number of hours, or maybe a day (assuming a hab the crew moves to for surface ops), has to have a weeks worth of consumables if they need to wait for the next NRHO Gateway/Orion pass, or if they abort landing, and need to phase for rendezvous.

[tater]

They have said current SS might get ~150t to LEO reusable. That's not including the vehicle which is ~100+t. Making the upper stage expendable (no landing stuff, thinner steel, stage off fairing), and optimizing the engine number for expendable use (fewer Raptors, all vacuum engines), that could easily add 20t to LEO. Expending SH (the plan for a while regardless) vs boostback and recovery will be a huge difference as well (RTLS is a 40% hit to F9). That means our expendable SS can probably get nearly 300t to LEO.

Get Orion to LEO using literally anything not SLS.

Launch lander under SS fairing. Dock with Orion, go to LLO (SS does LOI). Looks like you could have a 30-40 ton lander.

[sevenperforce]

19 minutes ago, Exoscientist said:

I think the lowered propellant load was specifically so that the Orion could do its circumlunar test flight and the interim upper stage had limited payload to TLI capability.

The lowered propellant capacity was originally because Orion was supposed to be paired with Altair and so it only needed to come back from LLO in the first place.

35 minutes ago, Exoscientist said:

The propellant load of the Orion service module though would have at least to be doubled to be able to get the entire stack into lunar orbit.

Making the service module twice as long, which adds about four meters to the height of the stack.

And even that wouldn't get what you needed.

Let's suppose a direct TLI to LLO, and let's generously double the propellant but only increase the dry mass by 50%.  Since the ascent module wouldn't have to go back to NRHO they could probably get it down to 7 tonnes, and since the ascent module weighs less the descent module could probably get by at 13 tonnes. So let's imagine a 20-tonne two-stage lander that magically fits inside this tiny fairing.

Current Orion's injected mass to TLI is 26.52 tonnes. Double the propellant and grow the dry mass of the ESM by 50% and that brings us up to 45.41 tonnes. So the launch vehicle needs to throw 66 tonnes to TLI.

Even so, getting the 900 m/s of dV you need to go from TLI to LLO is going to require the ESM to burn 16.9 tonnes of propellant. Suppose the lander descends to the surface and then returns. Orion now has just 300 kg of propellant, giving it a measly 32.3 m/s of dV when it tries to make the return to Earth.

[tater]

11 minutes ago, sevenperforce said:

Even so, getting the 900 m/s of dV you need to go from TLI to LLO is going to require the ESM to burn 16.9 tonnes of propellant. Suppose the lander descends to the surface and then returns. Orion now has just 300 kg of propellant, giving it a measly 32.3 m/s of dV when it tries to make the return to Earth.

Yeah, with Orion in the mix the throw to TLI needs to be entirely outside the range of SLS.

It's so frustrating they signed off on it without doing the math. We'd still have all the cost and delays—but we'd have a decent rocket that was useful for our trouble.

[RCgothic]

1 hour ago, sevenperforce said:

The lowered propellant capacity was originally because Orion was supposed to be paired with Altair and so it only needed to come back from LLO in the first place.

Making the service module twice as long, which adds about four meters to the height of the stack.

Increase in ESM diameter? It could be flush with Orion or even bi/co-conic like Gemini. 

Edited June 13, 2022 by RCgothic

[tater]

36 minutes ago, RCgothic said:

Increase in ESM diameter? It could be flush with Orion or even bi/co-conic like Gemini. 

Problem is that any increase in SM mass just borrows from the lander in the above calculations. Total TLI mass remains unchanged, it's just where the props are, in the SM, or in the lander or on a LOI stage for said lander—or drop tanks—then the lander doesn't need another set of engines.

[kerbiloid]

1.
Is the (trans)lunar Starship supposed to be refueled in high-eccentricity elliptic orbit on its way to home?

2.
Is the (trans)lunar Starship supposed to enter the atmosphere, aerobrake, and land, rather than be a long-living orbital tug?
Or Orion will be the only aerobraking thing?

3.
What if the crewed aerobraking vehicle had lost the safe re-entry corridor, and its descent from controlled (at 7..12 g) became ballistic (20..35 g) ?

[tater]

If we have the ability to put pretty substantial stages in LEO for relatively low cost soon, all this becomes moot.

Launch Orion in Starship, along with maybe an Orbital Module that can be pretty huge. No crew. Orbital module has docking on both sides.

Launch lander in Starship.

Launch a TLI stage in Starship.

Launch crew with commercial crew vehicle. Assemble the 3 above parts, go to Moon.