totm dec 2023 Artemis Discussion Thread

[AtomicTech]

4 minutes ago, tater said:

Unfortunately (for SLS), yes.

I can probably come up with a 3 stage Starship variant for this use case, Kerbal-style. Stage 3 in this case is just breaking Starship into 2 parts, the usual tank/engines bit, and the top as it's own vehicle with descent engines—which LSS (as currently shown) already has. Think I might have a while ago.

Ooh! That sounds very doable!

[tater]

If they could get Starship to LEO with 203t of payload in addition to the vehicle, we can imagine the top bit is 33 tons dry (ring count mass, plus some fitting out with slop—and rings could be lighter, no need for reentry), then we have a vehicle that would need engines with an I_sp of 327 to be able to fly from LEO tot he lunar surface. Course some of the dv could come before staging using Raptors.

 

[AtomicTech]

Just now, tater said:

If they could get Starship to LEO with 203t of payload in addition to the vehicle, we can imagine the top bit is 33 tons dry (ring count mass, plus some fitting out with slop—and rings could be lighter, no need for reentry), then we have a vehicle that would need engines with an I_sp of 327 to be able to fly from LEO tot he lunar surface. Course some of the dv could come before staging using Raptors.

 

And you could always just have an empty habitable space and bring all of the habitat compontents you'd need to install in subsequent missions.

[tater]

If expended SS/SH can in fact do 250-300t, then we make the hab with the required dv for LOI/landing props, and burn the engine/tank section to completion as part of TLI.

Just now, AtomicTech said:

And you could always just have an empty habitable space and bring all of the habitat compontents you'd need to install in subsequent missions.

Ideally it would be best to have the thing on the lunar surface ready to go I think. It would look sorta like many old Mars/Lunar concepts, except with a "hat" on top (the nose cone).

Land one as a habitat, land another designed to just garage a huge, pressurized rover (rest filled with supplies, or maybe materials to make a landing pad?).

[darthgently]

32 minutes ago, tater said:

Land one as a habitat, land another designed to just garage a huge, pressurized rover (rest filled with supplies, or maybe materials to make a landing pad?).

This is the real value of LSS in the long term:  Structures left in place for labs, industry, supply stockpiles, higher scale ISRU etc.  If the fuel tanks aren't useful for reuse as water or other storage with some in-place mods, then perhaps a more involved in-place SkyLab-like conversion could be done to turn them into near ground level rover hangars, storage, even hydroponics and more habitats.  This would potentially be a huge amount of internal space over time.

Once something with so much internal space has been expensively landed on another body why spend more to remove it?

Add pressurized tubes to connect multiple repurposed LSS craft and you have Mayberry on the Moon.  Big win

[StrandedonEarth]

15 minutes ago, darthgently said:

This is the real value of LSS in the long term:  Structures left in place for labs, industry, supply stockpiles, higher scale ISRU etc.  If the fuel tanks aren't useful for reuse as water or other storage with some in-place mods, then perhaps a more involved in-place SkyLab-like conversion could be done to turn them into near ground level rover hangars, storage, even hydroponics and more habitats.  This would potentially be a huge amount of internal space over time.

Once something with so much internal space has been expensively landed on another body why spend more to remove it?

Add pressurized tubes to connect multiple repurposed LSS craft and you have Mayberry on the Moon.  Big win

This is the way. Don’t forget to bring some bulldozers to bury stuff for protection. 

[darthgently]

45 minutes ago, StrandedonEarth said:

This is the way. Don’t forget to bring some bulldozers to bury stuff for protection. 

When I read this I had an image of a vertical tunneling machine with the Boring logo drilling a ~9m+ diameter vertical shaft into the surface that an LSS would (very) carefully land into resulting in the tanks being below the surface and the rest above.   Tailings from hole could be used to selectively berm around upper portion

[magnemoe]

49 minutes ago, darthgently said:

When I read this I had an image of a vertical tunneling machine with the Boring logo drilling a ~9m+ diameter vertical shaft into the surface that an LSS would (very) carefully land into resulting in the tanks being below the surface and the rest above.   Tailings from hole could be used to selectively berm around upper portion

Think digging an trench put down the modules and covering it is much more practical. 
And thought of making some LSS as purposeful base modules.  Living modules would be arranged for lying down, probably want to reinforce fuel and oxidizer tanks for wet workshop, like having an cover there you can place an huge hatch to drive even stuff like bulldozers into for service. 

[DAL59]

What do you think are the odds of SLS III actually happening are? II is mostly built with a designated crew and will almost certainly happen, but III is currently a mission with no set plan or place to go. 

[SunlitZelkova]

24 minutes ago, DAL59 said:

What do you think are the odds of SLS III actually happening are? II is mostly built with a designated crew and will almost certainly happen, but III is currently a mission with no set plan or place to go. 

Artemis III actually has some landing sites chosen. They plan to go in 2025, but realistically it will probably be 2028.

They have already started building the Orion MPCV for Artemis III, so it is most likely happening. Unless some radical political change occurs, SLS is here to stay for awhile.

[RCgothic]

I've been messing about with a design I might have chosen in 2011 instead of SLS. It keeps the 5-segment SRBs and 8.4m form factor to keep congress happy, but the first stage uses 3x RD-171Ms (or maybe a 171M and 4 RD180s) and the 2nd stage uses 7x J2s.

It would be capable of throwing 285t payload to LEO.

With an optional 285t 3rd stage (2x J2-X) it could throw around 120t to TLI in a single launch (in this case the 3rd stage ignition would need to begin prior to achieving LEO), and would weigh 4180t on the pad and stand ~95m tall to the 3rd stage payload adaptor.

The 3rd stage can be placed fully fuelled into LEO to meet a payload already there. 200t to TLI or 120t to TMI. Credible Mars missions and lunar surface bases? Yup.

These are all within the transporter crawler and VAB margins, would have though there might be a challenge with the SRBs bridging two stages and RD engines would probably have run into foreign issues by now. Fun exercise

Edited October 4, 2023 by RCgothic

[tater]

Kerolox would have made everything about SLS better.

But then no sustainer, shorter stage and dump it.

[sevenperforce]

4 hours ago, RCgothic said:

I've been messing about with a design I might have chosen in 2011 instead of SLS. It keeps the 5-segment SRBs and 8.4m form factor to keep congress happy, but the first stage uses 3x RD-171Ms (or maybe a 171M and 4 RD180s) and the 2nd stage uses 7x J2s.

It would be capable of throwing 285t payload to LEO.

With an optional 285t 3rd stage (2x J2-X) it could throw around 120t to TLI in a single launch (in this case the 3rd stage ignition would need to begin prior to achieving LEO), and would weigh 4180t on the pad and stand ~95m tall to the 3rd stage payload adaptor.

The 3rd stage can be placed fully fuelled into LEO to meet a payload already there. 200t to TLI or 120t to TMI. Credible Mars missions and lunar surface bases? Yup.

These are all within the transporter crawler and VAB margins, would have though there might be a challenge with the SRBs bridging two stages and RD engines would probably have run into foreign issues by now. Fun exercise

I like the sound of it. Of course anything with kerolox in the first stage is going to do better than SLS simply because it can hold more propellant. One of the biggest problems with SLS is the height limitation: hydrolox is so fluffy that the first stage takes up way more height than a corresponding mass of methalox or kerolox.

What are you figuring for dry mass of the first stage? The SLS core had to have some major strengthening to it compared to the light weight of the Shuttle external tank, and increasing the amount of props you're carrying in the first stage makes that even worse.

If we were back in 2011, one nifty option would have been to do another "Cluster's Last Stand" a la Saturn I, where tooling for existing tank designs was used with upper and lower thrust plates. Three Atlas V common core tanks will fit into the 8.4-meter footprint of the Shuttle external tank. Then maybe a shortened version of the Shuttle external tank could be used as the basis for an 8.4-meter second stage. I don't know if we had any J-2 engines in 2011 though.

A VERY fancy aspirational design would have been to put a pair of RS-25s underneath a Delta IV common core booster hydrogen tank and have it fire through an annular thrust plate. The thrust plate would hold a ring of small kerolox tanks (maybe from Falcon 1 which was available at the time) that wrap around the core tank, with appropriate kerolox engines underneath. Then a shortened version of the Shuttle external tank would sit on top of the common core booster and feed into it. At launch, the side boosters and kerolox engines and RS-25s all fire together. Once the kerolox tanks run dry, the entire ring is jettisoned and falls away, while the RS-25s continue thrusting to orbit.

[RCgothic]

Hey kids, you too can design a rocket with fantasy performance if you make an error in the 1st stage dry mass figure used for the DV calculations! The gross mass at burnout figure was correct, but later where the spreadsheet used dry mass for the DV calc it wasn't using the same figure.

More reasonable values for payloads were 2-stage 165t to LEO and 75t direct to TLI.  It's still got multiple useful applications though, unlike SLS. The 205t 3-stage payload might be a little low on the TWR side at liftoff though - down to 1.13. 

Apologies for the quality, I applied a filter to soften the raster a bit.

@sevenperforce  I've got 1st stage dry mass about 5% plus engines, 2nd & 3rd stages 8% plus engines, both significantly heavier than the STS super lightweight external tank. The reason it's not J2-X on the 2nd stage is 6-7 don't fit at an 8.4m diameter.

 

Edited October 5, 2023 by RCgothic

[Exoscientist]

 Price discrepancy on the cost of the SLS solid rocket boosters:

This article says the  costs of the SLS are likely to increase: 

NASA should consider commercial alternatives to SLS, inspector general says
"NASA’s aspirational goal to achieve a cost savings of 50 percent is highly unrealistic."
ERIC BERGER -  10/13/2023, 3:07 PM
https://arstechnica.com/space/2023/10/inspector-general-on-nasas-plans-to-reduce-sls-costs-highly-unrealistic/

 

 There is a  cost discrepancy in this image from the article in regards to the SRB’s. It says the SRB contract, whose total cost is in the last column, is for 10 SRB’s over the five missions from Artemis IV to VIII. That total cost is given as $3 billion. But that means each SRB costs $300 million. But each mission requires two SRB’s. That should mean the per mission cost is $600 million. Yet in the column for the cost of that item per Block 1B launch its only given as $300 million for the two SRB’s. So what’s the resolution of the discrepancy?
 

Bob Clark

  

 

Edited October 17, 2023 by Exoscientist

[Meecrob]

The contract value does not equal the Cost of Deliverables per Launch.  There would be no reason for NASA to award these contracts if they could just go to the store and buy all these items off-the-shelf with zero R & D required. One of the main reasons that SLS costs so much is because they cannot just use Shuttle parts. Its probably very much akin to how Falcon heavy is not just 3 Falcon 9's strapped together.

[Exoscientist]

38 minutes ago, Meecrob said:

The contract value does not equal the Cost of Deliverables per Launch.  There would be no reason for NASA to award these contracts if they could just go to the store and buy all these items off-the-shelf with zero R & D required. One of the main reasons that SLS costs so much is because they cannot just use Shuttle parts. Its probably very much akin to how Falcon heavy is not just 3 Falcon 9's strapped together.

 Ok, but the conclusion you still draw is amortized over flights, the cost for a pair of SRB’s is $600 million per flight. In other words, it’s getting twice as bad as time goes on.

     Bob Clark

Edited October 16, 2023 by Exoscientist

[RCgothic]

1 Exploration Upper Stage for Artemis IV

Contract Value: $9.7B

Number of articles: 1

Cost per SLS1B: $482m

That isn't how maths works. NASA keep trying to pretend tax dollars spent on R&D don't count, but actually they do.

[Exoscientist]

On 10/4/2023 at 9:44 AM, RCgothic said:

I've been messing about with a design I might have chosen in 2011 instead of SLS. It keeps the 5-segment SRBs and 8.4m form factor to keep congress happy, but the first stage uses 3x RD-171Ms (or maybe a 171M and 4 RD180s) and the 2nd stage uses 7x J2s.

It would be capable of throwing 285t payload to LEO.

With an optional 285t 3rd stage (2x J2-X) it could throw around 120t to TLI in a single launch (in this case the 3rd stage ignition would need to begin prior to achieving LEO), and would weigh 4180t on the pad and stand ~95m tall to the 3rd stage payload adaptor.

The 3rd stage can be placed fully fuelled into LEO to meet a payload already there. 200t to TLI or 120t to TMI. Credible Mars missions and lunar surface bases? Yup.

These are all within the transporter crawler and VAB margins, would have though there might be a challenge with the SRBs bridging two stages and RD engines would probably have run into foreign issues by now. Fun exercise

 

 A dense-propellant first stage would be preferred, but using hydrolox engines would save on development costs for a commercial replacement for the SLS:

NASA should consider commercial alternatives to SLS, inspector general says
"NASA’s aspirational goal to achieve a cost savings of 50 percent is highly unrealistic."
https://arstechnica.com/space/2023/10/inspector-general-on-nasas-plans-to-reduce-sls-costs-highly-unrealistic/

 First key thing is to eliminate the SRB’s. As I have argued large solid rocket boosters are not cost effective. Amortized costs for the SLS solid side boosters are $600 million for two, based on the $3 billion contract to Northrop Grumman for 10 of them.

 Instead, for a commercial replacement keep the hydrolox core stage but replace the expensive SSME’s with RS-68’s, to save on costs. Five RS-68’s would be required to enable lift-off.

 It could also be done with 7 SSME’s but the so-called “improved” versions now have bloated prices of ~$150 million per engine, compared to the original price of $50 million each. Seven of them would be a billion dollars just in engines alone.

 The RS-68 in contrast costs in the range of $10 to $20 million each, So 5 would be just $50 to $100 million. Note the RS-68 was considered for the SLS but its ablatively cooled nozzle would not handle well the extreme heating from the side boosters. But without the side boosters, that’s no longer an issue.

 A regeneratively cooled nozzle version of the RS-68 was investigated. It would raise the vacuum Isp to  ~421.5s compared to the 412s of the current version, and increase thrust about 20 tons. You would want to do this at some point to improve reusability.

 For the upper stage, we could use the Delta IV core, or the Boing EUS, or the Ariane 5 core. I favor the Ariane 5 core because it has both a high mass ratio and high vacuum ISP.

 I estimate in the range of 100 tons to LEO.

  Robert Clark

Edited October 17, 2023 by Exoscientist

[Royalswissarmyknife]

46 minutes ago, Exoscientist said:

NASA should consider commercial alternatives to SLS, inspector general says

I wonder what other Super Heavy Lift vehicles are in active development in the USA. 

[tater]

22 hours ago, Exoscientist said:

 Ok, but the conclusion you still draw is amortized over flights, the cost for a pair of SRB’s is $600 million per flight. In other words, it’s getting twice as bad as time goes on.

The current cost is more like $950M per flight (contract cost divided by boosters).

1 hour ago, Royalswissarmyknife said:

I wonder what other Super Heavy Lift vehicles are in active development in the USA. 

Yep, there's the problem right there, only 1 possible vehicle.

Note that NG could absolutely fly the Orion CSM to LEO. Not that Orion does any good in LEO. Then again, that was the CONOPS for Constellation. EOR architecture.

[RCgothic]

The key to a cost-effective replacement for SLS is for the love of Jeb never award any more business to Boeing, Aerojet Rocketdyne or Northrop Grumman.

[tater]

1 hour ago, RCgothic said:

The key to a cost-effective replacement for SLS is for the love of Jeb never award any more business to Boeing, Aerojet Rocketdyne or Northrop Grumman.

 

Nothing cost-plus, anyway.

[Meecrob]

On 10/16/2023 at 3:48 PM, Exoscientist said:

 Ok, but the conclusion you still draw is amortized over flights, the cost for a pair of SRB’s is $600 million per flight. In other words, it’s getting twice as bad as time goes on.

     Bob Clark

No, dude, go back to that chart and multiply any of those numbers out. They do not add up because they do not account for R & D.  They said the contract costs "x" and also the cost per flight is "y." They didn't say that they included all contract costs in the "per flight" costs. Or maybe I'm wrong and its not R & D, but something else. My point is that they never said that y times the number of flight articles equals x.

 

I agree SLS is extremely expensive for its capabilities, but lets base our criticisms in reality.

 

Edit: This is what I'm talking about.

On 10/16/2023 at 4:16 PM, RCgothic said:

1 Exploration Upper Stage for Artemis IV

Contract Value: $9.7B

Number of articles: 1

Cost per SLS1B: $482m

That isn't how maths works. NASA keep trying to pretend tax dollars spent on R&D don't count, but actually they do.

Edited October 18, 2023 by Meecrob

[Kerballlistic07]

20 hours ago, Royalswissarmyknife said:

I wonder what other Super Heavy Lift vehicles are in active development in the USA. 

Hmm, I’m not sure. I don’t think there are any. Definitely not a big shiny water tower…