Author Topic: Prediction: Technical realities will result in selection of SLS-launched HLS  (Read 55231 times)

Offline Coastal Ron

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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?

Congress writes the funding laws, and Presidents can only sign them or veto them. There is some flexibility, but for the most part an administration can award all the contracts they want, but there won't be money to pay the contractors unless Congress authorizes the programs.

So sure, a President can propose any date they want, and any activity they want. But funding laws - how and when money is spent - that comes from Congress.
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline jadebenn

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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....
Well, you've got one now.
« Last Edit: 02/22/2020 06:36 pm by jadebenn »

Offline jadebenn

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I'm seeing a whole lot of "should" and "believe". Now, I am by no means the sole authority on the subject, but I know some things that may be of use for grounding this conversation. Some of my observations, in no particular order:

The reference design I am most familiar with had a descent element over the 15 t limit, and the transfer element was right at the edge. Both designs were working with some relatively low TRL inclusions.

The amount of hydrogen boiled off over the 100+ day mission is low enough to justify using a passive system and accepting some boiloff, rather than using an active system (cryocoolers) to try and get ZBO.

The 15 t limit is the "updated" number. The internal estimate was higher.

Even before accounting for the 15 t launch vehicle restriction, the performance of this HLS design was not particularly reassuring, with landed payload mass far less than some of the AE sizing I saw in Appendix H solicitation. I would have to go back and look more carefully to see why that is. I also don't know enough about AE design closure to say how much of a problem that would be.

I am not aware of any analysis on stack height and how that relates to the crew. That could pose a risk if the lander needs to be squatter and fatter.

Switching to storables would require accelerating development of a pump-fed engine. Most of the research dollars have gone to cryogenic systems.

Methane and Liquid Hydrogen have very different implications for thermal design. A hydrogen design may end up with design closure issues that the methane design does not have. It is not as bianry as cryogenic vs storable.

Regardless of how many pieces there are and how they fit together, the elements are going to have a reasonably large structural component that is not tanks and feed systems. Making comparisons to launch vehicle stages is likely going to end in disappointment.

Things that produce power also produce heat. That heat has to go somewhere and generally the propellant is not where you want to put it. Exceptions exist. 

Total mass is, IMHO, not as relevant as the mass of the DE element, which is really what is going to drive most of the architecture decisions.

If you want my opinion, designs are going have severe difficulty closing under the 15 t limit without an extra "something" even with some of the low TRL bells and whistles baked in. The Appendix H reference documentations have several examples of what that extra something can be. It is my intuition that the larger launch vehicle is probably going to be substantially easier than some of the other "somethings". Note that larger launch vehicle doesn't necessarily mean SLS, but SLS is one option.
Good point that a larger LV doesn't necessitate SLS. It's in the latest phase of development for a vehicle of its size, but you also have slightly less-powerful designs that are around the same maturity and should be available by 2024, such as Vulcan and New Glenn. Starship is a bit of a wild card here, as cargo Starship could be ready to launch a separate lander payload by then, I think, but I don't think SpaceX would find that option very attractive.

Do we know New Glenn's payload to TLI, actually? I'd imagine, considering the rocket's size and its use of an LH2 upper stage, that it would be able to throw more mass to lunar orbit than non-expendable FH. That might be enough for the National Team to stick with the 3-element design with little difficulty. Of course I already believed they were the least likely to switch out of all the bidders, considering the specifics of their partnership.
« Last Edit: 02/22/2020 06:12 pm by jadebenn »

Offline ZChris13

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 don't think Starship is a good choice for Lunar Lander beyond the fact that it would:
A. exist
B. be able to send itself to the surface and back with significant payload via a refueling scheme

There are black marks against it too, I personally don't understand the exhaust impingement crater issue well but there are a lot of very smart people doomsaying regarding it. Using Starship as a TLI stage or maybe even a command/reentry module is a much more promising architecture, but requires additional development, which would negate the primary benefits so I guess we're back to letting better be the enemy of good enough.

I hope the first lunar cargo Starshp attempt is soonish, should be enlightening.

EDIT: whoops I forgot to make this on-topic.
I disagree with the ideas presented in the OP. Cryo boil-off doesn't seem to be as big of an issue as people think it is when you're not trying to use liquid hydrogen.
« Last Edit: 02/22/2020 06:38 pm by ZChris13 »

Offline GWH

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Do we know New Glenn's payload to TLI, actually? I'd imagine, considering the rocket's size and its use of an LH2 upper stage, that it would be able to throw more mass to lunar orbit than non-expendable FH. That might be enough for the National Team to stick with the 3-element design with little difficulty. Of course I already believed they were the least likely to switch out of all the bidders, considering the specifics of their partnership.

Short answer, not really. They state 13 tonnes to GTO, somewhere I saw 10-12 tonnes to TLI recently but I can't remember where for the life of me.

As big of a rocket it is, the 1st stage will have to stage at a lower velocity than say Delta IV or Atlas V, so its very large 2nd stage starts dropping in capabilities fast.

Of course other threads suggest they may be sandbagging:
https://forum.nasaspaceflight.com/index.php?topic=41146.1520
https://forum.nasaspaceflight.com/index.php?topic=43073.100

They also need to deliver class C payloads for NSSL of 6.6 tonnes direct to GEO, which doesn't really correspond with the payload ration between the LEO and GTO figure. 
This suggests 2 possibilities: either they really are sandbagging or they have something else up their sleeve. BE-7 is very well suited for used as a 3rd stage, which they plan to use for the transfer element and is pretty much the ideal 3rd stage/tug. See my thoughts on that here: https://www.reddit.com/r/BlueOrigin/comments/eukh8g/thoughts_on_the_blue_originnorthrop_grumman/


« Last Edit: 02/22/2020 09:51 pm by GWH »

Offline Lar

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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....
Well, you've got one now.
Check your PMs.  I'll try to remember where that thread we used was.
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
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Offline JohnFornaro

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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.

It's not a matter of weight.  It's a matter of date. 2024, first woman on the Moon.  All the pieces are well underway, but they lack integration and coordination, and most importantly, the will to achieve the proposed landing date, 2024.

Look at this thread.  Who is arguing to return humanity to the Moon in 2024?  A tiny mainority.  It appears that most of NASA's rank and file, like NASA's leadership, simply do not want there to be a lunar landing by 2024.  Prove me wrong. 
Sometimes I just flat out don't get it.

Offline JohnFornaro

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

Not if Congress doesn't fund it.

... You're saying that the President cannot propose a date?

... So sure, a President can propose any date they want ....

Thanks for sharing your enthusiasm.  With your help, mankind will surely stay on Earth.  Have a nice planet.
Sometimes I just flat out don't get it.

Offline Markstark

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I agree with your prediction that one of the HLS selections will be an SLS launched lunar lander. Furthermore, it will likely be a two stage lander. The SLS will feature a different upper stage and but not necessarily a Boeing-EUS.

Offline GWH

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If you want my opinion, designs are going have severe difficulty closing under the 15 t limit without an extra "something" even with some of the low TRL bells and whistles baked in. The Appendix H reference documentations have several examples of what that extra something can be. It is my intuition that the larger launch vehicle is probably going to be substantially easier than some of the other "somethings". Note that larger launch vehicle doesn't necessarily mean SLS, but SLS is one option.

As much as I love trying to unravel a good mystery, there look to be a few dozen attachments in the Appendix H bid solicitation.
Any hints as to which ones to look at?

Offline rakaydos

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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.

It's not a matter of weight.  It's a matter of date. 2024, first woman on the Moon.  All the pieces are well underway, but they lack integration and coordination, and most importantly, the will to achieve the proposed landing date, 2024.

Look at this thread.  Who is arguing to return humanity to the Moon in 2024?  A tiny mainority.  It appears that most of NASA's rank and file, like NASA's leadership, simply do not want there to be a lunar landing by 2024.  Prove me wrong.
Let me introduce you to the Golden Rule.

He who has the gold, makes the rules.

Congress has the power of the purse, recent constitutional crisis concerning "national state of emergency" aside, which means they decide if anyone gets paid to get to the moon by 2024.

We are in a capitalist society. If noone's getting paid to do something, it wont happen. (hence the need for social saftey nets in capitalisim, to make sure the money is there for basic humanitarian concerns)

On the other hand, Elon must definately has the will, and is expected to have the money, to practice moon landings while waiting for mars windows to open. Starship isnt at all optimised for the moon, but it has the capacity to brute force a solution in any number of ways. (dropping skycrane pad builders via apollo 10 trajectory, or intentional crashes of various kinds that lets a pad builder emerge safely, or additional nose (vertical) or belly (horizontal) mounted landing engines, or other approaches)

Once Elon's figured out landing on the moon (and mars), well, he's got no reason to go back to the moon unless someone pays him. But I bet the price will be less than an SLS launch, if anyone's interested.
« Last Edit: 02/23/2020 05:10 pm by rakaydos »

Offline jadebenn

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If you want my opinion, designs are going have severe difficulty closing under the 15 t limit without an extra "something" even with some of the low TRL bells and whistles baked in. The Appendix H reference documentations have several examples of what that extra something can be. It is my intuition that the larger launch vehicle is probably going to be substantially easier than some of the other "somethings". Note that larger launch vehicle doesn't necessarily mean SLS, but SLS is one option.

As much as I love trying to unravel a good mystery, there look to be a few dozen attachments in the Appendix H bid solicitation.
Any hints as to which ones to look at?
I believe he's referring to the several different reference architectures in one of the attachments.

Offline JohnFornaro

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

Not if Congress doesn't fund it.

Without congressional support, the president proposing a date has considerbly less weight than Elon Musk proposing a date. ...

It's not a matter of weight.  It's a matter of date. ...  All the pieces are well underway, but they lack ... the will to achieve the proposed landing date, 2024.

... Who is arguing to return humanity to the Moon in 2024?


Let me introduce you to the Golden Rule. He who has the gold, makes the rules.


I'm gonna write that one down.

Quote from: rakaydos
We are in a capitalist society. If noone's getting paid to do something, it wont happen.

No.  Capitalism does not explain, in a short, non-exhaustive list, the failure of Constellation, the gratuitous change of the OML for Orion, the slow process of SLS, the continuing delays of JWST, yada yada.  People are getting paid plenty; they end up wasting the money they are given.

In my view, Congress would be more generous with the purse strings if they thought NASA would accomplish the goal that the President has stated.  As it stands, NASA's budget is rising, but on this site and elsewhere, that budgetary increase is mocked.

In turn, let me introduce you to another saying:

Do not bite the hand that feeds you.
Sometimes I just flat out don't get it.

Offline envy887

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I'm seeing a whole lot of "should" and "believe". Now, I am by no means the sole authority on the subject, but I know some things that may be of use for grounding this conversation. Some of my observations, in no particular order:

The reference design I am most familiar with had a descent element over the 15 t limit, and the transfer element was right at the edge. Both designs were working with some relatively low TRL inclusions.

The amount of hydrogen boiled off over the 100+ day mission is low enough to justify using a passive system and accepting some boiloff, rather than using an active system (cryocoolers) to try and get ZBO.

The 15 t limit is the "updated" number. The internal estimate was higher.

Even before accounting for the 15 t launch vehicle restriction, the performance of this HLS design was not particularly reassuring, with landed payload mass far less than some of the AE sizing I saw in Appendix H solicitation. I would have to go back and look more carefully to see why that is. I also don't know enough about AE design closure to say how much of a problem that would be.

I am not aware of any analysis on stack height and how that relates to the crew. That could pose a risk if the lander needs to be squatter and fatter.

Switching to storables would require accelerating development of a pump-fed engine. Most of the research dollars have gone to cryogenic systems.

Methane and Liquid Hydrogen have very different implications for thermal design. A hydrogen design may end up with design closure issues that the methane design does not have. It is not as bianry as cryogenic vs storable.

Regardless of how many pieces there are and how they fit together, the elements are going to have a reasonably large structural component that is not tanks and feed systems. Making comparisons to launch vehicle stages is likely going to end in disappointment.

Things that produce power also produce heat. That heat has to go somewhere and generally the propellant is not where you want to put it. Exceptions exist. 

Total mass is, IMHO, not as relevant as the mass of the DE element, which is really what is going to drive most of the architecture decisions.

If you want my opinion, designs are going have severe difficulty closing under the 15 t limit without an extra "something" even with some of the low TRL bells and whistles baked in. The Appendix H reference documentations have several examples of what that extra something can be. It is my intuition that the larger launch vehicle is probably going to be substantially easier than some of the other "somethings". Note that larger launch vehicle doesn't necessarily mean SLS, but SLS is one option.

A lot of interesting stuff here, and I think this post could be a full page of itself.

Is Appendix H or another summary of the considered architectures available anywhere public? In particular, I wonder if increasing the AE wet mass to the 15+ t limit and using part of that on descent was considered, to mitigate DE mass growth.

Offline FiniteBurn

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The Appendix H solicitation included a number of reference documents under Attachment A. One of them is the Analyses of Alternatives. I believe it has been posted and discussed on this forum before.

Offline rakaydos

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No.  Capitalism does not explain, in a short, non-exhaustive list, the failure of Constellation, the gratuitous change of the OML for Orion, the slow process of SLS, the continuing delays of JWST, yada yada.  People are getting paid plenty; they end up wasting the money they are given.
Nothing to do with the 2020 date, and the president's lack of ability to back it up with money.

Quote
In my view, Congress would be more generous with the purse strings if they thought NASA would accomplish the goal that the President has stated.  As it stands, NASA's budget is rising, but on this site and elsewhere, that budgetary increase is mocked.
Why would you believe that? Congress has no problem throwing NASA money, but not for 2024 moon missions. They throw NASA money because it's welfare that they can pretend isnt welfare, and those "good paying jobs" might vanish if we ever actually accomplished anything.
« Last Edit: 02/26/2020 03:59 pm by rakaydos »

Offline GWH

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The Appendix H solicitation included a number of reference documents under Attachment A. One of them is the Analyses of Alternatives. I believe it has been posted and discussed on this forum before.

Thank you, Second BAA draft, Attachment A12 Architecture Analysis of Alternatives (August 7 2019) https://beta.sam.gov/opp/cd53a248201b96671d9599dd268fdc47/view
PDF Download Link

Coles notes:
Considered Alternatives:
- Sub-TLI launch, individual elements finish the burn
- Make the transfer element do more (partial crasher stage, or pick up the ascent element in LLO)
- Higher capacity launch vehicle
- in space propellant transfer
- 4 element launch is also considered
- Passive Cryogenic Fluid Management with deployable sun shield to reduce boil off rates of cryogens
- Active Cryogenic Fluid Managenement
- Launch vehicle upper stage derived transfer element (this includes Centaur specifically)
- Reusable landing gear as part of the ascent element
- Drop tanks for the ascent element or a combined Ascent/Decent element
- Combined ascent/descent element and 2 transfer elements
- "Super tug" built off launch vehicle upper stage. Pretty deep split kind of contradicts a statement about not considering deep dV splits

Not considered alternatives
- Single stage
- Any kind of Earth Orbit rendezvous including single stage*
- Deep split ascent/descent elements (aka a true crasher stage)
- SEP tugs

Commercial launch vehicle graphics are initially a very Falcon Heavy looking outline, then on slide 41 on are New Glenn's with the logo stripped off (strakes and all).

*Earth Orbit rendezvous wasn't considered due to high thermal loads and orbital debris concerns.



Overall this makes me more excited and curious to see these proposals come out. The sub-TLI launch option I think would be favorable to Blue Origin's proposal as a BE-7 would have great ISP and New Glenn's second stage is going to have a lot of dry mass due to its shear size. Drop tanks and re purposed upper stages both would make for some very neat architectures.
« Last Edit: 02/24/2020 10:33 pm by GWH »

Offline JohnFornaro

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No.  Capitalism does not explain, in a short, non-exhaustive list, ... yada yada.  People are getting paid plenty; they end up wasting the money they are given.


Nothing to do with the 2020 date, and the president's lack of ability to back it up with money.

And by 2020, you mean 2024, right?  And it's not the President's "lack of ability" to secure funding.  As everybody here knows, the President proposes, and Congress disposes.

Quote from: JF
In my view, Congress would be more generous with the purse strings if they thought NASA would accomplish the goal that the President has stated.  ...

Quote from: rakaydos
Why would you believe that? Congress has no problem throwing NASA money, but not for 2020 [2024?] moon missions. They throw NASA money because it's welfare that they can pretend isn't welfare, and those "good paying jobs" might vanish if we ever actually accomplished anything.

Well, yeah.  I have this old fashioned idea that success is rewarded, failure not.
Sometimes I just flat out don't get it.

Offline ZChris13

Quote from: rakaydos
Why would you believe that? Congress has no problem throwing NASA money, but not for 2020 [2024?] moon missions. They throw NASA money because it's welfare that they can pretend isn't welfare, and those "good paying jobs" might vanish if we ever actually accomplished anything.
Well, yeah.  I have this old fashioned idea that success is rewarded, failure not.
It's important to keep in mind Congress' definition of success and failure in this matter.

Offline RonM

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Well, yeah.  I have this old fashioned idea that success is rewarded, failure not.

Then you should be supporting a 2028 moon landing instead of 2024. Vice President Pence pulled the 2024 date out of his you know what just so President Trump could have a moon landing during his second term (assuming he is reelected). 2024 will get us a flag and footprints mission because of the rush to get it done. 2028 could lead to a sustainable program.

Getting back on topic, I think political realities will have SLS used to launch crew on Orion while everything else will be done on commercial launchers. HLS will not be launched on SLS because of cost.

Tags: HLS Artemis 
 

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