Author Topic: How should NASA evolve the SLS?  (Read 178692 times)

Offline Hyperion5

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How should NASA evolve the SLS?
« on: 12/06/2012 11:28 pm »
We pretty much now know what the SLS Bloc I is going to look like.  It's going to feature two 5-segment SRBs derived from the Shuttle's 4-segment SRBs, the first stage will be the largest ever built and be powered by 4 SSMEs, and the upper stage is a donated Delta Cryogenic Second Stage.  It's a rocket, that, depending on whom you believe, either puts up 70 mt or up to 100 mt (I'm personally think it'll do around 90 mt).  With the first version mostly set, how should NASA evolve the SLS to be of the greatest benefit? 

We've already got several choices with the first upgrade step. 

Block IA – Supposedly would add two things, the first being a 8.4 m Cryogenic Propulsion Stage powered by either a J-2X or multiple RL-10 equivalent engines.  The second would be either advanced solid rocket boosters from ATK or liquid rocket boosters from companies like Aerojet (AJ-1) or Rocketdyne (F-1A).  Various payloads listed for this version range from 105 mt to 120 mt. 

Block IB - This is the minimum change variant which simply has a 8.4 m CPS with 4 RL-10 engines.  It's supposed to be able to launch 105 mt. 

Block II – It might feature a lengthened core stage along with an additional RS-25E powering it.  Beyond that there is some talk of using two-three J-2X engines to give it a robust Earth Departure Stage.  Depending on boosters, it could launch 130-150 mt to low earth orbit. 

So the question again is, how would you evolve the SLS for NASA's maximum benefit?  For instance, do you stay with solid boosters or switch to LRBs?  Kill the J-2X or employ it?  What fairing sizes do you employ?  You get the idea of how it goes on. 

--------

My personal preference is to keep the flight rate up while maximizing initial payload capabilities.  If I were evolving it I'd add the relatively cheap Bloc IB upgrade first.  From there I'd add LRBs, and to upgrade the US further I'd simply up the number of next-gen US engines from 4 to 9 to keep maximum commonality between EELVs and the SLS. 
« Last Edit: 12/06/2012 11:29 pm by Hyperion5 »

Offline TomH

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Re: How should NASA evolve the SLS?
« Reply #1 on: 12/06/2012 11:39 pm »
I think there needs to be a defined mission before the LV is evolved.

Offline Hyperion5

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Re: How should NASA evolve the SLS?
« Reply #2 on: 12/07/2012 12:32 am »
I think there needs to be a defined mission before the LV is evolved.

It's true they need a defined mission, but let's say the new President comes into power in 2017 and decides they want to do lunar missions.  What evolution would you recommend then?  There's a limited number of deep-space missions to consider anyways.  You've got missions to a possible EML2 space station, missions to the lunar surface, missions to LLO, missions to asteroids, and then missions to Mars (both orbit and surface). 

How would your ideal SLS differ if you were considering lunar surface missions versus missions to an asteroid or to Martian orbit?  In my opinion you could get away with the SLS Bloc IB for many of the initial deep space missions.  However, if you're going to the moon, you'll probably want something even more capable like a full-fledged Bloc IA with plenty of RL-10 engines on the US and LRBs on the sides. 

Offline spectre9

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Re: How should NASA evolve the SLS?
« Reply #3 on: 12/07/2012 01:09 am »
Launch Vehicle

Block 2B

F-1 LRBs, RL-10 upper stage

Mission

Mars

NASA will be tasked to use the whole payload in new creative ways like they worked out how to do Apollo with what was then just a Saturn C-5. People didn't figure out that LOR method overnight. They did it because of the tremendous amount of resources being poured into that singular goal. Get to the moon.

Once NASA can focus on Mars they'll show us how they can make the SLS useful for those missions.

It's very difficult to show SLS as useful for moon missions when others are coming up with ways to go to the moon without a heavy lifter.

Offline giskard03

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Re: How should NASA evolve the SLS?
« Reply #4 on: 12/07/2012 01:22 am »
Boeing's already designing for a Block 1B Core Stage, which envelopes Block 1A loads as well.  So the real question is how do you get from a Block 1B vehicle to a Block 2 vehicle?  I think given the current funding levels, NASA will figure out how to "shoe-horn" a Block 2 Core Stage from the Block 1B design through some combination of load reduction (uncertainty reduction from flight data from the first couple of Block 1 launches), reduced factors of safety, modification of the trajectory, etc...

Offline sdsds

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Re: How should NASA evolve the SLS?
« Reply #5 on: 12/07/2012 03:42 am »
The first step would be to upgrade the "figure of merit" measure by which alternatives are analysed. For SLS as NASA intends to use it, mass delivered to LEO is not as useful a measure as mass delivered to a cis-lunar rendezvous orbit.
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Offline Hyperion5

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Re: How should NASA evolve the SLS?
« Reply #6 on: 12/07/2012 04:55 am »
The first step would be to upgrade the "figure of merit" measure by which alternatives are analysed. For SLS as NASA intends to use it, mass delivered to LEO is not as useful a measure as mass delivered to a cis-lunar rendezvous orbit.

Here's another interesting question: what are the likely TLI numbers for the SLS Bloc I, Bloc IB or Bloc IA?  I'd expect the SLS Bloc IB to have some serious numbers thanks to having four RL-10 engines.  It's like having a Super Centaur stage up top.  Archibald mentioned over in the "How would Russia go the Moon?" thread that it's about a 1:1 match between propellant used to TLI payload delivered with centaur stages.  That would suggest to me that you might get close to matching a Saturn V's 45 mt TLI capacity with just the SLS Bloc IB. 

I am fairly confident an SLS Bloc IA with the same upper stage and advanced boosters, especially LRBs, would match or better the Saturn V's TLI numbers.  Now wouldn't that be something? 
« Last Edit: 12/07/2012 04:56 am by Hyperion5 »

Offline Ben the Space Brit

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Re: How should NASA evolve the SLS?
« Reply #7 on: 12/07/2012 09:45 am »
My understanding of the current SLS evolution path was this (excuse me if I'm wrong).

Block-I - Three SSMEs, iCPS (modified DCSS) and 5-seg RSRM-V solid boosters; 70t IMLEO, 30t TLI
Block-IA - Four or five RS-25E, CPS and 5-seg RSRM-V; 105t IMELO, 40t+ TLI
Block-IB - As Block-IA but with Next-generation boosters (NGBs); 120t IMLEO, 50t TLI
Block-II - Includes 3 x J-2X upper stage & CPS becomes third stage, if included in stack; 130t IMLEO

Now, I'm sceptical on whether the program can be sustained for such a long path.  My own preferred upgrade path removes the advanced boosters.  I'm no fan/friend of ATK.  However, the RSRM-V is sufficient and, IMHO at least, pursuit of excellence should not slow the project.  Additionally, the J-2X-powered mid-stage isn't strictly required in the near- or even mid-term.  Development should only proceed if a solid mission appears that absolutely requires >100t IMLEO per launch.  Such a mission does not exist at present.

I would also fund a common CPS between the EELVs and SLS on the theme of ULA's ACES system.  By sharing the U/S development costs with DoD for the EELV Phase-I project, more cash can be spared for payloads.  It would not greatly impair the performance of SLS as the SLS core could launch the entire spacecraft/ACES combo into initial parking orbit with little or no use of the CPS's engines.  So, you'd be able to get the full 40t+ through escape.

So, my SLS Block-II would be: 4 x RS-25E & RSRM-V booster; 4 x RL-10B-2/-10C on 5.4m-diameter ACES-41 upper stage.

Block-III, if required, would add a 2 x J-2X 8.4m-diameter upper stage but would not be developed unless a need arose.

My motive is solely to get SLS to a position where it can be usefully utilised as soon as possible without a multi-decade development program.


[edit]
Fixed typo
« Last Edit: 12/07/2012 09:47 am by Ben the Space Brit »
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Offline truth is life

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Re: How should NASA evolve the SLS?
« Reply #8 on: 12/07/2012 02:17 pm »
I would also fund a common CPS between the EELVs and SLS on the theme of ULA's ACES system.  By sharing the U/S development costs with DoD for the EELV Phase-I project, more cash can be spared for payloads.  It would not greatly impair the performance of SLS as the SLS core could launch the entire spacecraft/ACES combo into initial parking orbit with little or no use of the CPS's engines.  So, you'd be able to get the full 40t+ through escape.

It would also provide potentially improved performance and cost for payloads using the Atlas or Delta, like unmanned payloads. The idea of using ACES as the CPS is at once obvious and something I hadn't thought of, but it seems like a probably good idea.

I had heard that there were some production limits on the five-segment boosters that made advanced boosters (whether liquid or solid) necessary at some point?

Online edkyle99

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Re: How should NASA evolve the SLS?
« Reply #9 on: 12/07/2012 02:50 pm »
So the question again is, how would you evolve the SLS for NASA's maximum benefit? 
Develop Block I, then add an improved second stage to make Block 1B.  The result will be a highly capable launch vehicle, the world's most capable, developed using propulsion that essentially already exists.  After that, stop forever "developing" and just fly the thing.

 - Ed Kyle

Offline ChileVerde

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Re: How should NASA evolve the SLS?
« Reply #10 on: 12/07/2012 02:56 pm »
My understanding of the current SLS evolution path was this (excuse me if I'm wrong).

Block-I - Three SSMEs, iCPS (modified DCSS) and 5-seg RSRM-V solid boosters; 70t IMLEO, 30t TLI
Block-IA - Four or five RS-25E, CPS and 5-seg RSRM-V; 105t IMELO, 40t+ TLI
Block-IB - As Block-IA but with Next-generation boosters (NGBs); 120t IMLEO, 50t TLI
Block-II - Includes 3 x J-2X upper stage & CPS becomes third stage, if included in stack; 130t IMLEO


How would this path map onto the SLS Top Level Milestone Schedule NASA presented to its Advisory Committee Council three weeks ago? The attachment below is cut and pasted from the three slides of that presentation.

IOW, if we assume that the Milestone Schedule is somewhat real, which of the four SLS missions shown use Block-I, -IA, -1B as characterized above?

Edit: Corrected bureaucratic solecism.
« Last Edit: 12/07/2012 04:22 pm by ChileVerde »
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Offline Lars_J

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Re: How should NASA evolve the SLS?
« Reply #11 on: 12/07/2012 03:53 pm »
So the question again is, how would you evolve the SLS for NASA's maximum benefit? 
Develop Block I, then add an improved second stage to make Block 1B.  The result will be a highly capable launch vehicle, the world's most capable, developed using propulsion that essentially already exists.  After that, stop forever "developing" and just fly the thing.

The sooner people understand that "flying the thing" is not the main objective with SLS, the better. The primary objective with SLS has always been getting funds to congressional districts and the contractors. Being in a constant development mode becomes just a convenient excuse to not flying, which they would prefer not to do since it is risky.

And who wants to risk the sweet deal of getting billions of $ per year for doing very little? But they do have to fly sometimes to put up an appearance - thus the laughable a-mission-every-18-months schedule in that ChileVerde posted.
« Last Edit: 12/07/2012 03:55 pm by Lars_J »

Offline sdsds

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Re: How should NASA evolve the SLS?
« Reply #12 on: 12/07/2012 06:34 pm »
My understanding of the current SLS evolution path was this (excuse me if I'm wrong).

Block-I - Three SSMEs

I wish that were true, but am pretty sure the plan of record calls for all of the initial SLS cores to fly with four SSME. With four per vehicle, NASA will need to "upgrade" to new-production core engines sooner.
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Offline ChileVerde

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Re: How should NASA evolve the SLS?
« Reply #13 on: 12/07/2012 08:23 pm »
My understanding of the current SLS evolution path was this (excuse me if I'm wrong).

Block-I - Three SSMEs

I wish that were true, but am pretty sure the plan of record calls for all of the initial SLS cores to fly with four SSME. With four per vehicle, NASA will need to "upgrade" to new-production core engines sooner.

In a recent discussion, it was suggested that, if "new-production core engines" means RS-25E, the lead time between start of development and delivery of the first flight units would be something like seven years. 

But, if it's decided to stick with SSME RS-25Ds -- just make more of them -- what would the lead time then need to be between signing the contract and delivery of the first new unit?  If the first new unit is needed in the mid-2020s, can the RS-25D production capability be put on ice between now and then? Or could it be recreated de novo when needed?
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Offline Lobo

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Re: How should NASA evolve the SLS?
« Reply #14 on: 12/07/2012 10:11 pm »
Boeing's already designing for a Block 1B Core Stage, which envelopes Block 1A loads as well.  So the real question is how do you get from a Block 1B vehicle to a Block 2 vehicle?  I think given the current funding levels, NASA will figure out how to "shoe-horn" a Block 2 Core Stage from the Block 1B design through some combination of load reduction (uncertainty reduction from flight data from the first couple of Block 1 launches), reduced factors of safety, modification of the trajectory, etc...

Agreed.  I think they will see about getting 130mt from a Block1B with Advanced boosters at some point down the road to meet the NAA2010 madate without needing a 5th RS-25 on the core or a J2X powered 2nd stage.  The F-1 Dynetics boosters with a Block 1B upper stage should hit that no problem.  Not sure about the ATK Advanced Booster, but NASA could put out the RFQ to specifiy enough advanced booster performance so the Block 1B core and upper stage can hit 130mt without needing to be upgraded.  That eliminates the Block II core redesign to strengthen it for the additional bending loads of the LUS added length, and the MPS redesign to add the 5th RS-25, and the LUS development entirely.

Offline Lobo

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Re: How should NASA evolve the SLS?
« Reply #15 on: 12/07/2012 10:32 pm »
My understanding of the current SLS evolution path was this (excuse me if I'm wrong).

Block-I - Three SSMEs, iCPS (modified DCSS) and 5-seg RSRM-V solid boosters; 70t IMLEO, 30t TLI
Block-IA - Four or five RS-25E, CPS and 5-seg RSRM-V; 105t IMELO, 40t+ TLI
Block-IB - As Block-IA but with Next-generation boosters (NGBs); 120t IMLEO, 50t TLI
Block-II - Includes 3 x J-2X upper stage & CPS becomes third stage, if included in stack; 130t IMLEO

 

I think you have a couple of these off here.

Block 1 is four RS-25’s, iCPS, and the 5-seg SRB.
Block 1A is the same four RS-25’s, the same iCPS, but with advanced boosters.
Block 1B  is the same as Block 1, but with a new 8.4m upper stage/EDS powered by [likely] four RL-10’s or some other high performance NGE.
Block II [currently]has advanced boosters, a 5th RS-25 on the core, a J2X powered large upper stage (like the Saturn S-II stage), and then a dedicated CPS on top of that for EDS duties.  (This is a very long stack)

Block 1, Block 1A, and Block II are current Program of Record, until that changes.  Block 1B is an alternate to Block 1A being evaluated, but not officially part of the PoR as far as I know.

Once evaluations have been done, NASA will choose what will succeed Block 1, Block 1A or Block 1B.  And then they’ll choose what succeeds that.  A “Block IIB” would probably add powerful enough advanced boosters to Block 1B in order to get 130mt to LEO, and then they can eliminate the current PoR of a 5th RS-25 and the J2X powered Large upper stage. 
I think the current Block II PoR concept was before Dynetics came out with their super booster concept that opened the door to the boosters being powerful enough to not have to upgrade the core again and develop a brand new J2X powered Large upper stage.  And I’d be pretty surprised if it didn’t get axed soon considering the developments over the last year, and replaced with basically a Block II with powerful enough advanced boosters to only need a new Block 1B style upper stage, and the same four RS-25’s on the core as Block 1.  But that will probably wait until NASA’s finished with it’s evaluations of the different 1A and 1B options.

And that’s really the best way to go.  That means the core only gets designed once, and is designed for the Block 1B or 1A loads (although the booster interfaces will need to be upgraded for the advanced boosters).  One new upper stage, and that’s it.  That drops several development paths from the current Block II PoR. 

Offline spectre9

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Re: How should NASA evolve the SLS?
« Reply #16 on: 12/08/2012 02:00 am »
So the question again is, how would you evolve the SLS for NASA's maximum benefit? 
Develop Block I, then add an improved second stage to make Block 1B.  The result will be a highly capable launch vehicle, the world's most capable, developed using propulsion that essentially already exists.  After that, stop forever "developing" and just fly the thing.

 - Ed Kyle

ATK isn't advantaged in the booster comp. That's the law. It has to be fair. It doesn't matter if it benefits NASA. It matters that private companies get a fair chance to break this booster monopoly that's older than I am.

Offline Hyperion5

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Re: How should NASA evolve the SLS?
« Reply #17 on: 12/08/2012 02:15 am »

Once evaluations have been done, NASA will choose what will succeed Block 1, Block 1A or Block 1B.  And then they’ll choose what succeeds that.  A “Block IIB” would probably add powerful enough advanced boosters to Block 1B in order to get 130mt to LEO, and then they can eliminate the current PoR of a 5th RS-25 and the J2X powered Large upper stage. 
I think the current Block II PoR concept was before Dynetics came out with their super booster concept that opened the door to the boosters being powerful enough to not have to upgrade the core again and develop a brand new J2X powered Large upper stage.  And I’d be pretty surprised if it didn’t get axed soon considering the developments over the last year, and replaced with basically a Block II with powerful enough advanced boosters to only need a new Block 1B style upper stage, and the same four RS-25’s on the core as Block 1.  But that will probably wait until NASA’s finished with it’s evaluations of the different 1A and 1B options.

And that’s really the best way to go.  That means the core only gets designed once, and is designed for the Block 1B or 1A loads (although the booster interfaces will need to be upgraded for the advanced boosters).  One new upper stage, and that’s it.  That drops several development paths from the current Block II PoR. 

That's certainly a very feasible upgrade path and one I could approve.  It's interesting that you and Ed disagree on just how far to take the SLS though.  He says to upgrade once to Bloc IB and then max the flight rate.  You seem to be holding to the 2010 NASA Authorization Act figures a lot more.  Is that because you think SLS will genuinely need 130 mt of lifting capability or because NASA has to hold to its authorizing legislation? 

If it's for capabilities, what kind of capabilities do you envision as being enabled with your Bloc II SLS that you can't enable with the Bloc IB SLS? 
--------

Btw, what are the likely TLI numbers on either version?  The Saturn V could lift 120 mt to LEO and had a 45 mt TLI capability.  Interestingly, modemeagle found if you ditched the third stage it still would have put 120 mt into LEO.  It was only because it needed to go to the moon that it had a third stage, however it sent things to the moon with a much less efficient J-2 (420 sec Isp) up top.  Given we're looking at four RL-10 engines with a minimum Isp of 452 seconds, what TLI or TMI numbers are we looking at?  I'm betting the Bloc II SLS with those engines could top 50 mt TLI capabilities. 

Online edkyle99

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Re: How should NASA evolve the SLS?
« Reply #18 on: 12/08/2012 02:38 am »
So the question again is, how would you evolve the SLS for NASA's maximum benefit? 
Develop Block I, then add an improved second stage to make Block 1B.  The result will be a highly capable launch vehicle, the world's most capable, developed using propulsion that essentially already exists.  After that, stop forever "developing" and just fly the thing.

 - Ed Kyle

ATK isn't advantaged in the booster comp. That's the law. It has to be fair. It doesn't matter if it benefits NASA. It matters that private companies get a fair chance to break this booster monopoly that's older than I am.
So compete the five-segment boosters.  ATK doesn't have to build them.  Just don't spend $10 billion more, or whatever, to develop an all-new design, again.

 - Ed Kyle
« Last Edit: 12/08/2012 02:42 am by edkyle99 »

Offline sdsds

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Re: How should NASA evolve the SLS?
« Reply #19 on: 12/08/2012 03:01 am »
So compete the five-segment boosters.  ATK doesn't have to build them.  Just don't spend $10 billion more, or whatever, to develop an all-new design, again.

Right. Chris has I think indicated the possibility of ten flights using existing RSRMV hardware. My hope is that an upper stage will be available by then, so there will be no need for high-performance boosters. The need would be for low cost, high reliability boosters.
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