NASA's Artemis Program Updates and Discussion Thread 4

[yg1968]

Architecture is important, but it’s not “first”.  Form follows function.  Goals first.

I should add that I am not convinced that this annual architecture review will have much of an impact.

It’s hard to see how the vague, amorphorous goals that Melroy put out could drive any architecture decisions or changes.

Artemis has a single, overriding, unambiguous and well-articulated goal, and the goal does indeed drive the architecture. The goal is to provide ongoing justification for the funding of SLS/Orion. All other goals are secondary and will be evaluated in terms of how they support the primary goal. The problem for those in the industry who want to work toward a viable and sustainable lunar presence is how to present suitable secondary goals in the hopes that they can eventually replace SLS/Orion. This is all very disheartening to those of us on the sidelines who would like to see the money spent effectively.

That's not true. The Artemis program inherited SLS and Orion. Neither Bridenstine, nor VP Pence really liked SLS and were even willing to consider alternatives.

Sorry, I was unclear. I did not specify who had this overriding goal. It was not any of the people you mentioned.

I guess that you can argue that is the goal of certain members of Congress but it isn't the goal of NASA. The goal of NASA was explained yesterday by Melroy and it is the "sustained human presence and exploration throughout the solar system" (see the link below). For reasons that I have explained before, I believe that goal is sound. You can argue that SLS and Orion do not further that goal but I don't think that you can argue that the goal is the problem. 

https://forum.nasaspaceflight.com/index.php?topic=57221.msg2422857#msg2422857

You are ignoring the golden rule: "the one with the gold, rules". NASA cannot propose an Artemis architecture that is not centered on SLS/Orion until something changes at the congressional level. This is the mandated core of the Artemis architecture. The program is built around the numbered missions, and each numbered mission is centered on an SLS/Orion launch. Melroy's statement of a different (and laudable) goal does not change the underlying architecture of Artemis in this decade.

Right but the goals can have an impact on future programs such as the lunar surface habitats. It is important that habitats be a private, public partnership. For the time being, surface habitats is my biggest concern in the upcoming decisions related to Artemis. I am anxious to see what will be proposed in the 2022 architecture review.

[DanClemmensen]

You are ignoring the golden rule: "the one with the gold, rules". NASA cannot propose an Artemis architecture that is not centered on SLS/Orion until something changes at the congressional level. This is the mandated core of the Artemis architecture. The program is built around the numbered missions, and each numbered mission is centered on an SLS/Orion launch. Melroy's statement of a different (and laudable) goal does not change the underlying architecture of Artemis in this decade.

Right but the goals can have an impact on future programs such as the lunar surface habitats. It is important that habitats be a private, public partnership. For the time being, surface habitats is my biggest concern for Artemis. I am anxious to see what will be proposed in the 2022 architecture review.

But the underlying architecture only allows for a crew do 4 every year at the most, and unless something changes, this will get rolled into the specifications for the habitats. I would like to see a habitat/Moonbase that is specified for continuous occupation by overlapping crews of 20 launching every 2 months for four-month missions, or some such. But that implies the end of SLS/Orion and you apparently cannot even discuss it. So we will end up with a habitat that less roomy than a Starship HLS.

[yg1968]

You are ignoring the golden rule: "the one with the gold, rules". NASA cannot propose an Artemis architecture that is not centered on SLS/Orion until something changes at the congressional level. This is the mandated core of the Artemis architecture. The program is built around the numbered missions, and each numbered mission is centered on an SLS/Orion launch. Melroy's statement of a different (and laudable) goal does not change the underlying architecture of Artemis in this decade.

Right but the goals can have an impact on future programs such as the lunar surface habitats. It is important that habitats be a private, public partnership. For the time being, surface habitats is my biggest concern for Artemis. I am anxious to see what will be proposed in the 2022 architecture review.

But the underlying architecture only allows for a crew do 4 every year at the most, and unless something changes, this will get rolled into the specifications for the habitats. I would like to see a habitat/Moonbase that is specified for continuous occupation by overlapping crews of 20 launching every 2 months for four-month missions, or some such. But that implies the end of SLS/Orion and you apparently cannot even discuss it. So we will end up with a habitat that is less roomy than a Starship HLS.

It doesn't necessarily imply the end of SLS and Orion as you could have a commercial HLV and spacecraft in addition to SLS and Orion. For the surface habitats, it's important that NASA allow private astronauts to use them. So I hope that the surface habitats are acquired by NASA as a service and that other users are also encouraged to use them.

[clongton]

It doesn't necessarily imply the end of SLS and Orion as you could have a commercial HLV and spacecraft in addition to SLS and Orion. For the surface habitats, it's important that NASA allow private astronauts to use them. So I hope that the surface habitats are acquired by NASA as a service and that other users are also encouraged to use them.

Emphasis mine.
The surface habitats need to be commercially owned and operated, and maybe NASA could occasionally rent space in them. But looking long term (which we should all be doing), what we actually need is commercially owned and operated mines, smelters and manufacturing and food production facilities - on the moon. Then the people that are working on the moon, whether permanently or in 6-12 month shifts, could make their own stuff for a fraction of the price than we could make it here and then ship it to the moon for people there to use. The goal of lunar bound flights should be to support the people working there as they build a lunar economy to the point where they don't need earth-based HLVs anymore, just personnel and logistical support on commercially owned and operated spacecraft. That's what Artemis should be aiming for, to enable something like that.

[DanClemmensen]

You are ignoring the golden rule: "the one with the gold, rules". NASA cannot propose an Artemis architecture that is not centered on SLS/Orion until something changes at the congressional level. This is the mandated core of the Artemis architecture. The program is built around the numbered missions, and each numbered mission is centered on an SLS/Orion launch. Melroy's statement of a different (and laudable) goal does not change the underlying architecture of Artemis in this decade.

Right but the goals can have an impact on future programs such as the lunar surface habitats. It is important that habitats be a private, public partnership. For the time being, surface habitats is my biggest concern for Artemis. I am anxious to see what will be proposed in the 2022 architecture review.

But the underlying architecture only allows for a crew do 4 every year at the most, and unless something changes, this will get rolled into the specifications for the habitats. I would like to see a habitat/Moonbase that is specified for continuous occupation by overlapping crews of 20 launching every 2 months for four-month missions, or some such. But that implies the end of SLS/Orion and you apparently cannot even discuss it. So we will end up with a habitat that is less roomy than a Starship HLS.

It doesn't necessarily imply the end of SLS and Orion as you could have a commercial HLV and spacecraft in addition to SLS and Orion. For the surface habitats, it's important that NASA allow private astronauts to use them. So I hope that the surface habitats are acquired by NASA as a service and that other users are also encouraged to use them.

So one of the regularly-scheduled bi-monthly HLS(v2.0) flights will pick up the Orion crew in NRHO when it picks up the twenty passengers from the bi-monthly passenger Starship? And this justifies SLS/Orion?

[deadman1204]

All the stuff about what the program needs and what we want ignores the elephant in the room.
Congress won't fund NASA sendig anyone to the moon when it DOESN'T use SLS/Orion. How can all this other stuff happen when 80% of the HLS budget is for SLS/Orion

[yg1968]

You are ignoring the golden rule: "the one with the gold, rules". NASA cannot propose an Artemis architecture that is not centered on SLS/Orion until something changes at the congressional level. This is the mandated core of the Artemis architecture. The program is built around the numbered missions, and each numbered mission is centered on an SLS/Orion launch. Melroy's statement of a different (and laudable) goal does not change the underlying architecture of Artemis in this decade.

Right but the goals can have an impact on future programs such as the lunar surface habitats. It is important that habitats be a private, public partnership. For the time being, surface habitats is my biggest concern for Artemis. I am anxious to see what will be proposed in the 2022 architecture review.

But the underlying architecture only allows for a crew do 4 every year at the most, and unless something changes, this will get rolled into the specifications for the habitats. I would like to see a habitat/Moonbase that is specified for continuous occupation by overlapping crews of 20 launching every 2 months for four-month missions, or some such. But that implies the end of SLS/Orion and you apparently cannot even discuss it. So we will end up with a habitat that is less roomy than a Starship HLS.

It doesn't necessarily imply the end of SLS and Orion as you could have a commercial HLV and spacecraft in addition to SLS and Orion. For the surface habitats, it's important that NASA allow private astronauts to use them. So I hope that the surface habitats are acquired by NASA as a service and that other users are also encouraged to use them.

So one of the regularly-scheduled bi-monthly HLS(v2.0) flights will pick up the Orion crew in NRHO when it picks up the twenty passengers from the bi-monthly passenger Starship?

As is the case for commercial crew, I would expect private astronauts to fly on separate non-NASA HLS missions. Private astronaut missions could come to the lunar surface when NASA isn't there, in order to be able to use some of the assets that NASA normally uses (such as surface habitats).

[freddo411]

You are ignoring the golden rule: "the one with the gold, rules". NASA cannot propose an Artemis architecture that is not centered on SLS/Orion until something changes at the congressional level. This is the mandated core of the Artemis architecture. The program is built around the numbered missions, and each numbered mission is centered on an SLS/Orion launch. Melroy's statement of a different (and laudable) goal does not change the underlying architecture of Artemis in this decade.

Right but the goals can have an impact on future programs such as the lunar surface habitats. It is important that habitats be a private, public partnership. For the time being, surface habitats is my biggest concern for Artemis. I am anxious to see what will be proposed in the 2022 architecture review.

But the underlying architecture only allows for a crew do 4 every year at the most, and unless something changes, this will get rolled into the specifications for the habitats. I would like to see a habitat/Moonbase that is specified for continuous occupation by overlapping crews of 20 launching every 2 months for four-month missions, or some such. But that implies the end of SLS/Orion and you apparently cannot even discuss it. So we will end up with a habitat that less roomy than a Starship HLS.

I question the assumption that surface assets will *necessarily* be encumbered with requirements that specifically draw from Orion/SLS limitations.    Sure, it's possible it turns out that way, but it is also possible that a surface habitat could be built to to function for Orion-length visits/cadences but ALSO be able to host longer stays.

Case in point, is the gateway built in such a way that visitors can only stay 4 weeks per year?   Or could it host visitors for 8 weeks a year (with appropriate supplies)?

Another case:   Could the HLS lander handle 6 astronauts instead of 4?  Just because the requirements are for 2 astronauts, doesn't mean that vehicle is limited to that.

I would argue that "sustainable" could and should be understood to mean (among other things) fit for future purposes beyond what is immediately planned for today.    ISS for example has hosted tourists, although it was not designed for it.

[DistantTemple]

You are ignoring the golden rule: "the one with the gold, rules". NASA cannot propose an Artemis architecture that is not centered on SLS/Orion until something changes at the congressional level. This is the mandated core of the Artemis architecture. The program is built around the numbered missions, and each numbered mission is centered on an SLS/Orion launch. Melroy's statement of a different (and laudable) goal does not change the underlying architecture of Artemis in this decade.

Right but the goals can have an impact on future programs such as the lunar surface habitats. It is important that habitats be a private, public partnership. For the time being, surface habitats is my biggest concern for Artemis. I am anxious to see what will be proposed in the 2022 architecture review.

But the underlying architecture only allows for a crew do 4 every year at the most, and unless something changes, this will get rolled into the specifications for the habitats. I would like to see a habitat/Moonbase that is specified for continuous occupation by overlapping crews of 20 launching every 2 months for four-month missions, or some such. But that implies the end of SLS/Orion and you apparently cannot even discuss it. So we will end up with a habitat that is less roomy than a Starship HLS.

It doesn't necessarily imply the end of SLS and Orion as you could have a commercial HLV and spacecraft in addition to SLS and Orion. For the surface habitats, it's important that NASA allow private astronauts to use them. So I hope that the surface habitats are acquired by NASA as a service and that other users are also encouraged to use them.

So one of the regularly-scheduled bi-monthly HLS(v2.0) flights will pick up the Orion crew in NRHO when it picks up the twenty passengers from the bi-monthly passenger Starship?

As is the case for commercial crew, I would expect private astronauts to fly on separate non-NASA HLS missions. Private astronaut missions could come to the lunar surface when NASA isn't there, in order to be able to use some of the assets that NASA normally uses (such as surface habitats).

Commercial doesn't just mean tourist. It could include other international governmental teams. These may possibly be trained by Polaris and SX. After Polaris 3 what next? If Isaacman wants to offer full professional astronaut training.....  (Isaacman has mentioned  being involved with Mars) Will he help "bring on" a suitable habitat with sufficient volume.... for more than the NASA, "4"?
This is not specific, just suggesting a (ISTM) plausible scenario for commercial habitats, and a funding stream.

[DanClemmensen]

You are ignoring the golden rule: "the one with the gold, rules". NASA cannot propose an Artemis architecture that is not centered on SLS/Orion until something changes at the congressional level. This is the mandated core of the Artemis architecture. The program is built around the numbered missions, and each numbered mission is centered on an SLS/Orion launch. Melroy's statement of a different (and laudable) goal does not change the underlying architecture of Artemis in this decade.

Right but the goals can have an impact on future programs such as the lunar surface habitats. It is important that habitats be a private, public partnership. For the time being, surface habitats is my biggest concern for Artemis. I am anxious to see what will be proposed in the 2022 architecture review.

But the underlying architecture only allows for a crew do 4 every year at the most, and unless something changes, this will get rolled into the specifications for the habitats. I would like to see a habitat/Moonbase that is specified for continuous occupation by overlapping crews of 20 launching every 2 months for four-month missions, or some such. But that implies the end of SLS/Orion and you apparently cannot even discuss it. So we will end up with a habitat that less roomy than a Starship HLS.

I question the assumption that surface assets will *necessarily* be encumbered with requirements that specifically draw from Orion/SLS limitations.    Sure, it's possible it turns out that way, but it is also possible that a surface habitat could be built to to function for Orion-length visits/cadences but ALSO be able to host longer stays.

Case in point, is the gateway built in such a way that visitors can only stay 4 weeks per year?   Or could it host visitors for 8 weeks a year (with appropriate supplies)?

Another case:   Could the HLS lander handle 6 astronauts instead of 4?  Just because the requirements are for 2 astronauts, doesn't mean that vehicle is limited to that.

I would argue that "sustainable" could and should be understood to mean (among other things) fit for future purposes beyond what is immediately planned for today.    ISS for example has hosted tourists, although it was not designed for it.

At this point we are piling speculations on top of each other. In particular I am speculating that the NASA habitat requirements will be based on the SLS/Orion cadence and crew limitations, so any vendor's design that meets these requirements can remain in contention. This is consistent with the Appendix P HLS and the Option B HLS requirements. Sure, any vendor might choose to bid a more capable habitat or HLS, but this would be in spite of NASA's goals, not because of them. If NASA truly had a goal of "sustainable human presence", there would be a strong preference for a bigger habitat or a bigger Moonbase and for a bigger Appendix P HLS.

Gateway is a side show. It exists because the Artemis architecture is centered on SLS/Orion and SLS/Orion cannot land a crew on the Moon directly. If Artemis could sustain a human presence on the Moon, I doubt anyone would want to stay on Gateway.

[TheRadicalModerate]

It doesn't necessarily imply the end of SLS and Orion as you could have a commercial HLV and spacecraft in addition to SLS and Orion. For the surface habitats, it's important that NASA allow private astronauts to use them. So I hope that the surface habitats are acquired by NASA as a service and that other users are also encouraged to use them.

Emphasis mine.
The surface habitats need to be commercially owned and operated, and maybe NASA could occasionally rent space in them. But looking long term (which we should all be doing), what we actually need is commercially owned and operated mines, smelters and manufacturing and food production facilities - on the moon. Then the people that are working on the moon, whether permanently or in 6-12 month shifts, could make their own stuff for a fraction of the price than we could make it here and then ship it to the moon for people there to use. The goal of lunar bound flights should be to support the people working there as they build a lunar economy to the point where they don't need earth-based HLVs anymore, just personnel and logistical support on commercially owned and operated spacecraft. That's what Artemis should be aiming for, to enable something like that.

You can't look too long-term, because commercially owned and operated habs and other infrastructure only make sense if they turn a profit.  In the late 2020's to early 2030's timeframe, they probably can't.

That makes the NASA architecture vitally important, because it's the vehicle through which NASA can put up parts of the infrastructure for either public/private partnerships or pure commercial use.  However, unlike the LEO-based CRS/CCP programs, which could feed directly into a fairly vibrant market for LEO and GEO transport, there's no "dual use" business case for the Moon--yet.  So the architecture will wind up dictating what pieces-parts get built when, which in turn will let the private sector figure out how to leverage them to make real money.

I suspect that the low-hanging fruit is a more end-to-end transport system, EVA suits, and power/thermal systems.  Unlike habs and specific pieces of industrial infrastructure, all of that stuff scales very cleanly, which is what investors want.  If they can invest at low scale and turn a modest profit, it limits their time horizon and risk, which is what makes the IRR look good on the bottom line of the spreadsheet.

That doesn't mean that NASA won't build out their own rovers, habs, and interesting ISRU experiments.  Indeed, that sounds like a great way to divert the savings from cheaper transport back to the snouts that are already in the trough, which in turn lessens the embarrassment and economic pain caused by SLS/Orion getting gradually (or not-so-gradually) supplanted.  And as those experiments bear fruit, there will be other interesting public/private plays, which in turn will lead to better business cases for industrialization.

But none of this happens without the NASA architecture being rational and designed with the end in mind.  Without them, it's a crappy private investment.

[TheRadicalModerate]

At this point we are piling speculations on top of each other. In particular I am speculating that the NASA habitat requirements will be based on the SLS/Orion cadence and crew limitations, so any vendor's design that meets these requirements can remain in contention. This is consistent with the Appendix P HLS and the Option B HLS requirements. Sure, any vendor might choose to bid a more capable habitat or HLS, but this would be in spite of NASA's goals, not because of them. If NASA truly had a goal of "sustainable human presence", there would be a strong preference for a bigger habitat or a bigger Moonbase and for a bigger Appendix P HLS.

Gateway is a side show. It exists because the Artemis architecture is centered on SLS/Orion and SLS/Orion cannot land a crew on the Moon directly. If Artemis could sustain a human presence on the Moon, I doubt anyone would want to stay on Gateway.

It should probably be noted that the LSS can pretty much be its own hab.  Appendix P is written so that NASA can actually get a second source, and that requires a hab, so that a little dinky HLS offering is viable.  But assuming that LSS works, building its crew module out to be a viable hab is a lot easier than building a standalone one.

Mind you, I think that App. P and the things needed to make it viable (habs, the Gateway, standalone power systems, etc.) are necessary, because they're how money gets funneled to the incumbents as SLS and Orion dry up and blow away.  But if NASA and SpaceX sat down together to design a single-source architecture, it would look a lot different.

FWIW, Gateway may be a side show, but it's also a very nice piece of risk-reduction for SpaceX if they want to design a transport architecture that stages LSS from LEO instead of NRHO, allowing the crew to be brought to/from LEO by an F9/D2.  That requires a post-ascent refueling somewhere in cislunar.  If that refueling takes place in NRHO, then the crew can use the Gateway as a lifeboat if something goes wrong with refueling.  Again, a second LSS would work perfectly well as a lifeboat as well, but in the real world, finding as many semi-useful non-SpaceX gewgaws as possible is essential to Congress shelling out the big bucks.

[Zed_Noir]

<snip>
But none of this happens without the NASA architecture being rational and designed with the end in mind.  Without them, it's a crappy private investment.

The NASA Lunar architecture isn't rational as long as it is saddle with the SLS/Orion Lunar orbit crew transport approach. Which is too expensive and flies infrequently to sustain any sort Lunar surface program with maybe 4 occasional persons staying on the Lunar surface for about 30 days every 18 months or so.

NASA or anyone else needs cheaper way to get more people on the Lunar surface and staying longer than 30 days for a sustainable Lunar program. Otherwise it is just a glorified boots & flag program.

[lykos]

Let NASA do its job amd let the politics play with their super expensive toy.
Finally it will come like it came with the SpaceShuttle and the ISS.

In the end of the 20th there will still be 4 SLS/Orion/NASA-Astronauts for a few weeks a year on the moon and dozens of Starship/SX-passengers from all of the world every month walking arround in the craters.

At the end they will bury there rocket like they have burred the Shuttle and will bury the ISS and they will rent a Starship.

[yg1968]

At this point we are piling speculations on top of each other. In particular I am speculating that the NASA habitat requirements will be based on the SLS/Orion cadence and crew limitations, so any vendor's design that meets these requirements can remain in contention. This is consistent with the Appendix P HLS and the Option B HLS requirements. Sure, any vendor might choose to bid a more capable habitat or HLS, but this would be in spite of NASA's goals, not because of them. If NASA truly had a goal of "sustainable human presence", there would be a strong preference for a bigger habitat or a bigger Moonbase and for a bigger Appendix P HLS.

I disagree that a more capable HLS was in spite of NASA's goals. NASA had minimal HLS requirements (landing of 4 crew) but providers are not discouraged from providing extra capabilities. One of the goals for HLS was for NASA to be one of many customers and a more capable HLV helps in that respect.

The same is true for habitats, I don't think that NASA will discourage providers from having extra space. But I hope that a modular design will be encouraged. I hope that modular habitat-campers are possible.

[DanClemmensen]

At this point we are piling speculations on top of each other. In particular I am speculating that the NASA habitat requirements will be based on the SLS/Orion cadence and crew limitations, so any vendor's design that meets these requirements can remain in contention. This is consistent with the Appendix P HLS and the Option B HLS requirements. Sure, any vendor might choose to bid a more capable habitat or HLS, but this would be in spite of NASA's goals, not because of them. If NASA truly had a goal of "sustainable human presence", there would be a strong preference for a bigger habitat or a bigger Moonbase and for a bigger Appendix P HLS.

I disagree that a more capable HLS was in spite of NASA's goals. NASA had minimal HLS requirements (landing of 4 crew) but providers are not discouraged from providing extra capabilities. One of NASA's goals for HLS was also to be one of many customers and a more capable HLV helps in that respect.

The same is true for habitats, I don't think that NASA will discourage providers from having extra space. But I hope that a modular design will be encouraged. I hope that modular habitat-campers are possible.

I did not say Starship HLS is overqualified in spite of NASA's requirements (it was happenstance.) I said HLS Appendix P and option B, which I am speculating will stick to the "sustainable" requirements that are constrained to the Orion crew size instead of being increased to something more consistent with a more ambitious goal.

[yg1968]

At this point we are piling speculations on top of each other. In particular I am speculating that the NASA habitat requirements will be based on the SLS/Orion cadence and crew limitations, so any vendor's design that meets these requirements can remain in contention. This is consistent with the Appendix P HLS and the Option B HLS requirements. Sure, any vendor might choose to bid a more capable habitat or HLS, but this would be in spite of NASA's goals, not because of them. If NASA truly had a goal of "sustainable human presence", there would be a strong preference for a bigger habitat or a bigger Moonbase and for a bigger Appendix P HLS.

I disagree that a more capable HLS was in spite of NASA's goals. NASA had minimal HLS requirements (landing of 4 crew) but providers are not discouraged from providing extra capabilities. One of NASA's goals for HLS was also to be one of many customers and a more capable HLV helps in that respect.

The same is true for habitats, I don't think that NASA will discourage providers from having extra space. But I hope that a modular design will be encouraged. I hope that modular habitat-campers are possible.

I did not say Starship HLS is overqualified in spite of NASA's requirements (it was happenstance.) I said HLS Appendix P and option B, which I am speculating will stick to the "sustainable" requirements that are constrained to the Orion crew size instead of being increased to something more consistent with a more ambitious goal.

We have had this discussion before but I disagree that it was coincidence/happenstance that Starship won Option A. Being overqualified is a good thing and worked in SpaceX's favor. I also disagree that the requirements should be increased over what was described for the sustainable lander in Appendix H.

The one thing that I don't like is that NASA is allowing an Appendix P provider to offer a 2 person and 4 person variants of its HLS (see the link below). Presumably, being difficult to upgrade to 4 persons would be considered in the evaluation of the proposal but I think that NASA should have required a 4 person lander from the outset. A 2 person HLS variant shouldn't even exist.

https://forum.nasaspaceflight.com/index.php?topic=56067.msg2409402#msg2409402

[TheRadicalModerate]

<snip>
But none of this happens without the NASA architecture being rational and designed with the end in mind.  Without them, it's a crappy private investment.

The NASA Lunar architecture isn't rational as long as it is saddle with the SLS/Orion Lunar orbit crew transport approach. Which is too expensive and flies infrequently to sustain any sort Lunar surface program with maybe 4 occasional persons staying on the Lunar surface for about 30 days every 18 months or so.

NASA or anyone else needs cheaper way to get more people on the Lunar surface and staying longer than 30 days for a sustainable Lunar program. Otherwise it is just a glorified boots & flag program.

It's pretty easy to get rid of SLS/Orion and replace it with something more rational.  That replacement doesn't have to mess up the rest of the lunar surface components.

[Steven Pietrobon]

It means that the "experiment" of landing a vehicle on the Moon under propulsion followed by a close visual inspection was performed six seven* times during the Apollo era, and there was no evidence at all that lunar regolith did any damage to the lander.

The regolith damaged the Apollo 15 Descent Stage engine on landing.

"At touchdown, the lunar module was located partially inside a small crater with the rim of the crater directly underneath the descent engine skirt. The descent engine skirt buckled during landing."

https://www.hq.nasa.gov/alsj/a15/a15mr-7.htm

[JohnFornaro]

There was a LOT of discussion of the LM's ascent engine and it was tested over and over again.

As I mentioned above, sounds like a good test regimen, which apparently removed everything that could go wrong, defeating Murphy, the well-known opponent.

It's different with the Starship
(1) the descent engines ARE the ascent engines and, even though they're higher up, are exposed to any flying debris resulting from the landing.
(2) the propellants are NOT hypergolic and igniting the engines requires the successful completion of a whole series of ignition sequence events. If any one of them fails to complete there is no ignition.

(1)  There is no atmo to speak of, hence no eddies in wind currents causing debris to circle back and hit the engines.  I think. All the debris would be spewed radially away from the descent stage.

(2)  Plus, they have to be throttable, right?  Adding some complexity.  I don't think an "engine room" is viable because of the extra mass and even more complexity required.  How would the engine room interface with the ladder to get to the surface?  And inspection would have to be accompanied by the ability to repair whatever went wrong, suggesting additional mass of spares.

I don't know how, but the ignition sequence needs to be failsafe.