Prediction: Technical realities will result in selection of SLS-launched HLS

[jadebenn]

It's late at night, so I'll keep this brief.

Consider the following:
1. To maximize payload, a 3-stage lander design will need to use slow, low-energy transfers
2. Slow, low-energy transfers are not compatible with cryogenic fuels
3. Non-cryogenic fuels are not compatible with Artemis objectives of Lunar ISRU and the "soft" objective of maximal reuse of landing architecture
4. The aggressive 2024 deadline makes in-space cryogenic refueling non-viable, and to change the fuel type at a later date would require a total redesign of most of the lander.
5. The extreme mass constraints imposed by launching each of the three fueled components on existing CLVs leaves them with very little growth potential

In addition, the new head of HEOMD has been reviewing the Lunar architecture, and was supposed to have released a new plan internally on the 14th, with a public release upcoming sometime in March. I'm putting my money on the possibility we're going to be seeing some heavy revision in regards to HLS, EUS, and the SLS flight manifest and cadence in general.

Anyway, I know this will probably be an unpopular prediction, but I think it's fairly likely we might see one of the currently-announced bidders that was angling for a three-stage design come out with a newer two-stage revision that launches on a cargo Block 1B SLS, considering all the difficulties with the 3-stage approach.

[Proponent]

If the NRHO used has an altitude varying between 3000 and 7000 km, then a worst-case Hohmann-like transfer to LLO would be a approximately a 8700x1800-km ellipse (radii, not altitudes, at apolune and perilune).  Half the orbital period of such an ellipse is about 5 h.  That's not terribly long, and is certainly much shorter than the minimum acceptable maximum surface stay time.  I mean, you're going to want your crews to hang out on the moon for at least a few days.  Hence, I think it's surface stay times rather than orbital transfers that affect propellant choices.  That's to say that the ascent stage in a 2-stage lander and both the transfer and ascent stages in a 3-stage lander will need lengthy viability times.  The descent stage in either architecture may not, and, indeed, the Blue Origin/Lockheed/Northrop Grumman/Draper plan involves a hydrolox descent stage.  Methalox is nominally space storable and was originally baselined for Constellation's Orion capsule and Altair lander.  The BO/Lock/NG/D lacks a suitably sized methalox engine, however, so I would guess its transfer and ascent stages will burn the usual hypergols.

It's not clear to me that ISRU is going to be part of Artemis.  It's explicitly not part of H.R. 5666 (the House's proposed NASA authorization bill), and S. 2800 (the Senate's) refers to the vague term "sustainability" but not to ISRU.  Both bills require EUS and neither mentions 2024: two good reasons to believe that neither 2024 nor anything close to it will happen.

I think you may be right that 3-stage landers will fade from discussion.  Boeing wants 2 stages, and Congress seems to listen to Boeing.  Not that Congress should be specifying architectures at all, but....

[Lar]

Prediction: Technical Political realities will result in selection of SLS-launched HLS

Fixed that for you.

The technically "right" lander is a one stage lander. It's being built in Boca Chica as we speak.

[su27k]

Non of the technical reasons given make any sense:

1. NASA's DAC2 architecture analysis has 2-stage and 3-stage landers (IP 08 and 17) that do not use slow transfer to NRHO
2. DAC2 has a SLS based architecture that requires keeping LOX/CH4 fuel cool for 8 to 12 months (IP 03), so cryogenic fuel is compatible with slow transfer to NRHO
3. ISRU doesn't even appear in the HLS RFP. Reusability was mentioned as an option for post-2024 landing in early draft, but it was removed from the final version. So none of these will be used in selecting the winners.
4. 3 CLV launches can put more mass through TLI than a single SLS Block 1B, so it is Block 1B solution that is mass constrained.

Note everybody in the public has been using the 15t to TLI number, which is a conservative value from NASA LSP for FH. That number was published before the first Block 5 FH even flew, very likely the current FH can put a few more tons than this, that's assuming they don't uprate it, which I think is quite possible. I think this will be the biggest surprise once HLS bids are revealed: It would turn out the 15t to TLI constraint is wrong.

As for Doug Loverro's review, I don't think it will change anything major to HLS, since if he did, it would require a re-compete, which will slow things further (it's already slowed comparing to their original target date). And if NASA really wants to use SLS Block 1B, they wouldn't propose to postpone EUS in president's budget.

I'm betting if NASA does select more than one provider, then at least one provider won't be using SLS Block 1B, that's just common sense, otherwise SLS becomes a single point of failure.

[jadebenn]

Prediction: Technical Political realities will result in selection of SLS-launched HLS

Fixed that for you.

The technically "right" lander is a one stage lander. It's being built in Boca Chica as we speak.

I actually originally wanted to title this thread "Technical (not political) realities will result in selection of SLS-launched lander," but the character limit was too low for it, and I figured the meaning was well enough implied. I guess not.

I refuse to let this devolve into another Starship vs. SLS "discussion," so all I'll say is it will not be available for a crewed Lunar mission on this timescale.

[jadebenn]

4. 3 CLV launches can put more mass through TLI than a single SLS Block 1B, so it is Block 1B solution that is mass constrained.

You're not considering the mass penalties making each element autonomous and free-flying imposes. I'll admit the impact isn't equal on every module. The transfer stage shouldn't have too much problem fitting in a 15t payload. The ascent and descent stages are another story.

Note everybody in the public has been using the 15t to TLI number, which is a conservative value from NASA LSP for FH. That number was published before the first Block 5 FH even flew, very likely the current FH can put a few more tons than this, that's assuming they don't uprate it, which I think is quite possible. I think this will be the biggest surprise once HLS bids are revealed: It would turn out the 15t to TLI constraint is wrong.

Would be interesting, but how much more could be realistically squeezed out of it? 1t? 2t?

An expendable FH bid would also be interesting, but I don't expect to see that. Not with its fairing.

As for Doug Loverro's review, I don't think it will change anything major to HLS, since if he did, it would require a re-compete, which will slow things further (it's already slowed comparing to their original target date). And if NASA really wants to use SLS Block 1B, they wouldn't propose to postpone EUS in president's budget.

NASA didn't propose the end of EUS, the administration did, and there's virtually no chance that sticks (it didn't the last time they tried).

You're also not considering the possibility that this is on the bidder side. There's nothing stopping a bidder from changing their LV at this point in time if they make the trades and they come up positive.

I'm betting if NASA does select more than one provider, then at least one provider won't be using SLS Block 1B, that's just common sense, otherwise SLS becomes a single point of failure.

I could see the benefits of dissimilar redundancy, here, but it'd depend a lot on the specifics of the proposals and the weightings NASA uses, methinks.

[meberbs]

Prediction: Technical Political realities will result in selection of SLS-launched HLS

Fixed that for you.

The technically "right" lander is a one stage lander. It's being built in Boca Chica as we speak.

I actually originally wanted to title this thread "Technical (not political) realities will result in selection of SLS-launched lander," but the character limit was too low for it, and I figured the meaning was well enough implied. I guess not.

If you didn't want this to be political, you shouldn't have based your argument on a political 2024 date (and Congress rejecting that date out of politics,) and ISRU (removed in part by politics) etc. You jumped straight into the politics of the situation with your justification. The parts that you mention which are actually technical are also wrong as pointed out above.

I refuse to let this devolve into another Starship vs. SLS "discussion," so all I'll say is it will not be available for a crewed Lunar mission on this timescale.

As I know you are aware, I have already covered examples of how commercial rockets today provide better architectures than the SLS. While Starship clearly would be better in every way, and is developing at a rapid pace, it is fine to ignore it as a ground rule. It remains unreasonable from my perspective to even use SLS to launch Orion to the moon, but it is simply contradictory to the facts in evidence to think that SLS would somehow have spare capacity to launch other hardware as well if you stick to the 2024 timescale, and there is no plan to have EUS ready by then.

[armchairfan]

Note everybody in the public has been using the 15t to TLI number, which is a conservative value from NASA LSP for FH. That number was published before the first Block 5 FH even flew, very likely the current FH can put a few more tons than this, that's assuming they don't uprate it, which I think is quite possible. I think this will be the biggest surprise once HLS bids are revealed: It would turn out the 15t to TLI constraint is wrong.

Would be interesting, but how much more could be realistically squeezed out of it? 1t? 2t?

An expendable FH bid would also be interesting, but I don't expect to see that. Not with its fairing.

My quick-n-dirty guestimate would be that Falcon Heavy Expendable could push more than 20t through TLI. That's just based on comparing NASA's LSP performance curve with the "16.8t to Mars" currently mentioned on the SpaceX capabilities webpage and assuming a Mars C3 of 12 km²/s². That's a 5t difference between the LSP and SpaceX payload figures for trans Mars injection. Since the curve is steeper for low C3 (TLI C3 ~ -3), it's probably more than 15+5=20t. Expending (only) the center core takes about a 10% hit though perhaps more at TLI C3. So I'd just call it 20t even.

There are probably better estimates elsewhere on this forum. There's been a lot of reverse sleuthing trying to figure out various stage dry masses and the like from the published payload mass and velocity profile from prior missions.

[su27k]

Note everybody in the public has been using the 15t to TLI number, which is a conservative value from NASA LSP for FH. That number was published before the first Block 5 FH even flew, very likely the current FH can put a few more tons than this, that's assuming they don't uprate it, which I think is quite possible. I think this will be the biggest surprise once HLS bids are revealed: It would turn out the 15t to TLI constraint is wrong.

Would be interesting, but how much more could be realistically squeezed out of it? 1t? 2t?

An expendable FH bid would also be interesting, but I don't expect to see that. Not with its fairing.

My quick-n-dirty guestimate would be that Falcon Heavy Expendable could push more than 20t through TLI. That's just based on comparing NASA's LSP performance curve with the "16.8t to Mars" currently mentioned on the SpaceX capabilities webpage and assuming a Mars C3 of 12 km²/s². That's a 5t difference between the LSP and SpaceX payload figures for trans Mars injection. Since the curve is steeper for low C3 (TLI C3 ~ -3), it's probably more than 15+5=20t. Expending (only) the center core takes about a 10% hit though perhaps more at TLI C3. So I'd just call it 20t even.

There are probably better estimates elsewhere on this forum. There's been a lot of reverse sleuthing trying to figure out various stage dry masses and the like from the published payload mass and velocity profile from prior missions.

Yeah, Steven Pietrobon also estimated 20.8t through TLI in this post.

[GWH]

While not a bidder that we know of, Tory Bruno of ULA has made many comments implying long stage life of ACES like this one
https://www.reddit.com/r/ula/comments/96uoax/what_is_aces/e44r8a9/

Also inherent longevity of 5 years in space without refueling. And electrical power availability of around 20x of a conventional stage

I believe most of that life was due to the Multi Layer Insulation they intend to use and less so how ACES deals with boil off.

At least some in industry think they can deal with boil off, I would expect that to have  been one of the first items bidders looked at before proposing an architecture.

[su27k]

4. 3 CLV launches can put more mass through TLI than a single SLS Block 1B, so it is Block 1B solution that is mass constrained.

You're not considering the mass penalties making each element autonomous and free-flying imposes. I'll admit the impact isn't equal on every module. The transfer stage shouldn't have too much problem fitting in a 15t payload. The ascent and descent stages are another story.

Each element of the two stage lander on SLS will need its own propulsion systems too, and there needs to be a sort of "docking" interface between them so that the two can be separated, so some of that mass penalty applies to SLS single launch architecture too.

Note everybody in the public has been using the 15t to TLI number, which is a conservative value from NASA LSP for FH. That number was published before the first Block 5 FH even flew, very likely the current FH can put a few more tons than this, that's assuming they don't uprate it, which I think is quite possible. I think this will be the biggest surprise once HLS bids are revealed: It would turn out the 15t to TLI constraint is wrong.

Would be interesting, but how much more could be realistically squeezed out of it? 1t? 2t?

An expendable FH bid would also be interesting, but I don't expect to see that. Not with its fairing.

See discussion above about possible TLI capability of stock FH.

As far as I can see all the NASA planning for the CLV launched lander used FH as reference LV, so I don't see why fairing would be an issue.

As for Doug Loverro's review, I don't think it will change anything major to HLS, since if he did, it would require a re-compete, which will slow things further (it's already slowed comparing to their original target date). And if NASA really wants to use SLS Block 1B, they wouldn't propose to postpone EUS in president's budget.

NASA didn't propose the end of EUS, the administration did, and there's virtually no chance that sticks (it didn't the last time they tried).

You're also not considering the possibility that this is on the bidder side. There's nothing stopping a bidder from changing their LV at this point in time if they make the trades and they come up positive.

NASA is part of the administration, they're the same thing. The president's budget request is basically NASA's answer to congress about how much it would cost to do Artemis, there's no way NASA didn't have a say in what's in the budget.

The bids were submitted months ago, I don't think bidders can change it before winners are selected. It is possible that they can change it after being selected, but then given NASA really doesn't like to rely on EUS for 2024, I don't see why they would want to given the alternatives.

[Proponent]

4. 3 CLV launches can put more mass through TLI than a single SLS Block 1B, so it is Block 1B solution that is mass constrained.

The transfer stage shouldn't have too much problem fitting in a 15t payload. The ascent and descent stages are another story.

What about refueling with non-cyro propellants?  It:

    1. Makes the stages much lighter;
    2. Is a demonstrated technology; and
    3. Is required anyway for truly sustainable operations (though admittedly we don't really know what the Senate's authorization bill means by "sustainable":  if it's meant in a political sense, then probably anything that continues to fund Orion and SLS is "sustainable").

Note everybody in the public has been using the 15t to TLI number, which is a conservative value from NASA LSP for FH. That number was published before the first Block 5 FH even flew, very likely the current FH can put a few more tons than this, that's assuming they don't uprate it, which I think is quite possible. I think this will be the biggest surprise once HLS bids are revealed: It would turn out the 15t to TLI constraint is wrong.

Would be interesting, but how much more could be realistically squeezed out of it? 1t? 2t?

An expendable FH bid would also be interesting, but I don't expect to see that. Not with its fairing.

As for Doug Loverro's review, I don't think it will change anything major to HLS, since if he did, it would require a re-compete, which will slow things further (it's already slowed comparing to their original target date). And if NASA really wants to use SLS Block 1B, they wouldn't propose to postpone EUS in president's budget.

NASA didn't propose the end of EUS, the administration did, and there's virtually no chance that sticks (it didn't the last time they tried).

You're also not considering the possibility that this is on the bidder side. There's nothing stopping a bidder from changing their LV at this point in time if they make the trades and they come up positive.

I'm betting if NASA does select more than one provider, then at least one provider won't be using SLS Block 1B, that's just common sense, otherwise SLS becomes a single point of failure.

I could see the benefits of dissimilar redundancy, here, but it'd depend a lot on the specifics of the proposals and the weightings NASA uses, methinks.
[/quote]

[TrevorMonty]

While not a bidder that we know of, Tory Bruno of ULA has made many comments implying long stage life of ACES like this one
https://www.reddit.com/r/ula/comments/96uoax/what_is_aces/e44r8a9/

Also inherent longevity of 5 years in space without refueling. And electrical power availability of around 20x of a conventional stage

I believe most of that life was due to the Multi Layer Insulation they intend to use and less so how ACES deals with boil off.

At least some in industry think they can deal with boil off, I would expect that to have  been one of the first items bidders looked at before proposing an architecture.

A long life ACES stage can take slow route (3months) and deliver payload direct to Gateway for 3.1km/s compared to 3day 3.7km/s. That is significant performance increase for no additional mass to US as IVF system saves mass compared to current Centuar systems.

Also payload doesn't need propulsion and avionics for TLI - Gateway trip so more mass savings.

[Lar]

Prediction: Technical Political realities will result in selection of SLS-launched HLS

Fixed that for you.

The technically "right" lander is a one stage lander. It's being built in Boca Chica as we speak.

I actually originally wanted to title this thread "Technical (not political) realities will result in selection of SLS-launched lander," but the character limit was too low for it, and I figured the meaning was well enough implied. I guess not.

My take on the technical reasons put forward is that none of them hold up to scrutiny, so I'm comfortable with the recharacterization, but you go ahead and have fun trying...

I refuse to let this devolve into another Starship vs. SLS "discussion,"

People don't own threads. They go where they will. We mods will try to help keep things focused but only to a point. You can't wall off people pointing out that other alternatives are better.  PS, putting scare quotes around things doesn't make your case for you at all.

so all I'll say is it will not be available for a crewed Lunar mission on this timescale.

I'm willing to put my money where my mouth is, and (in a well structured way) bet that it will be ready for a crewed lunar mission before SLS will be... I never get any takers on my offers to bet, no idea why....

[JohnFornaro]

If you didn't want this to be political, you shouldn't have based your argument on a political 2024 date...

Is there some magical date that is NOT political?  1776?  1492? 2001?  Short answer:  No.  But 2024 is the date we have to work with at the moment.

Whether or not 2024 is "agressive" or not depends on the willingness of the aerospace community to work towards that date.  In my view, the first two women could certainly land on the Moon by 2024, if the damn community would simply work together instead of fighting each president since, I guess, George Washington.

[meberbs]

If you didn't want this to be political, you shouldn't have based your argument on a political 2024 date...

Is there some magical date that is NOT political?  1776?  1492? 2001?  Short answer:  No.  But 2024 is the date we have to work with at the moment.

Whether or not 2024 is "agressive" or not depends on the willingness of the aerospace community to work towards that date.  In my view, the first two women could certainly land on the Moon by 2024, if the damn community would simply work together instead of fighting each president since, I guess, George Washington.

Of course all dates are political, but my point was just that the claim from jadebenn that the arguments were purely technical and not political was inherently wrong.

I agree that despite the politics, 2024 could happen, but the limited flight rate of SLS means that adding to the role of SLS will make the date slip, conversely reducing its role can increase schedule confidence depending on what it is replaced with.

[Coastal Ron]

If you didn't want this to be political, you shouldn't have based your argument on a political 2024 date...

Is there some magical date that is NOT political?  1776?  1492? 2001?  Short answer:  No.

The first two of those were driven "need by" dates, they were "this is when it happened" dates. NOT politically driven.

But 2024 is the date we have to work with at the moment.

Not if Congress doesn't fund it.

Whether or not 2024 is "agressive" or not depends on the willingness of the aerospace community to work towards that date.

1. Why should the "aerospace community" care about the 2024 date? In this current effort they assume risk that doesn't translate into reward regardless if they meet the 2024 date or not. I see ZERO incentive for them.

2. In time of war or acknowledged "National Imperative" the private sector has stepped up to support their country in a time of need. This 2024 goal is NOT something the nation "needs", it is a political desire.

In my view, the first two women could certainly land on the Moon by 2024, if the damn community would simply work together instead of fighting each president since, I guess, George Washington.

The repeated use of gender pronouns is not enough for the private sector to risk $Millions on a political activity. And that is what the current NASA plan is, a "co-investment" strategy that requires private companies to risk their own money to attain a purely political goal. No wonder there is hesitation...

[JohnFornaro]

If you didn't want this to be political, you shouldn't have based your argument on a political 2024 date...

Is there some magical date that is NOT political?  1776?  1492? 2001?  Short answer:  No.  But 2024 is the date we have to work with at the moment.

Of course all dates are political, but my point was just that the claim from jadebenn that the arguments were purely technical and not political was inherently wrong.

I agree that despite the politics, 2024 could happen, but the limited flight rate of SLS means that adding to the role of SLS will make the date slip, conversely reducing its role can increase schedule confidence depending on what it is replaced with.

Well, maybe jadebenn could have tightened up his summary.

I'm not addressing the technical problems other than to broadly, but not specifically, agree that cryo boil-off would be a technical problem with low energy, *lazy* transfers.  It takes three and a half days to get to the Moon's surface. Go ahead and add an extra day to assemble pieces in LEO, then send 'em up to the Moon post haste.  If that's not the plan, then they're not really trying to get back to the Moon, as I see it.

I think it was Planetary Resources who proposed using low energy orbits for their project?  I skyped the lead tech guy once, and questioned him on the economic viability of six month transfer orbits, to find out that they hadn't considered the tinme value of money, but I digress.

I think what we're seeing at HEOMD and all, is simply the same-old same-old.  Sigh.

[JohnFornaro]

If you didn't want this to be political, you shouldn't have based your argument on a political 2024 date...

Is there some magical date that is NOT political?  1776?  1492? 2001?  Short answer:  No.  But 2024 is the date we have to work with at the moment.

Not if Congress doesn't fund it.

Really?  What role does Congress play in all this?  You're saying that the President cannot propose a date?

[rakaydos]

If you didn't want this to be political, you shouldn't have based your argument on a political 2024 date...

Is there some magical date that is NOT political?  1776?  1492? 2001?  Short answer:  No.  But 2024 is the date we have to work with at the moment.

Not if Congress doesn't fund it.

Really?  What role does Congress play in all this?  You're saying that the President cannot propose a date?

Without congressional support, the president proposing a date has considerbly less weight than Elon Musk proposing a date. It's federal Separation of Powers at work.