Dedicated SLS Block 1B Thread

[Khadgars]

Thought it might be prudent to create a thread for the SLS Block 1B since it often strays off topic in others.  After hearing lots of discussions about other variants it seems like this is the most straight forward path to creating the most capable LV.  How much more cost effective is it when compared to the 1A?  Does it free up enough funding for other payloads?

-Khad

[sdsds]

I think it makes sense to quote the article Chris Bergin wrote regarding the definition of "Block 1B."

notes on the L2 SLS section [...] have revealed a Block 1B configuration, one that continues to use RSRMV (solid) boosters, an 8.4m core with four RS-25D/E engines, an 8.4m Cryogenic Propulsion Stage with four RL10A-4-2 engines, and either an Orion MPCV or a payload under a 8.4m fairing. This vehicle would also be aiming to launch 105mt to LEO. However, the new stage can perform part of the ascent as well as TLI (Trans Lunar Injection).

The notes add that there are enough RS-25D engines in stock to support four missions, and enough RSRMV material (casings, etc.) to support 10 missions.

Selecting the SLS Block 1B over the Block 1A would result in delaying the advanced boosters until the 2030s, depending on the flight rate that is to be determined by the currently undefined Exploration Roadmap.

So 1B means a delay in any competitive procurement for SLS. The upper stage would be designed and built under the Boeing "stages" contract. RS-25 engines would come from PWR; there is no other supplier. Ditto (presumably) for RL-10 engines. RSRMV can only come from ATK. Only 1A involves a competitive procurement of an "advanced" booster. (I place "advanced" in scare quotes because IMHO it would be fine if ATK offered new steel cases for additional boosters.)

But maybe you wanted to discuss 1B without discussing how it would be procured?

[Khadgars]

Thanks for posting that.  I was just looking to create a thread to discuss anything relating to block 1B since it seems to be the preferred spec going forward.

I'm curious, in Chris's article, it states there are enough SRB material to support 10 missions.  Does that mean using the existing 4 seg material for the new 5 seg boosters?

[TomH]

I'm curious, in Chris's article, it states there are enough SRB material to support 10 missions.  Does that mean using the existing 4 seg material for the new 5 seg boosters?

My understanding is yes. There are at least 100 casing segments available, but less than 110. Two boosters X 5 casings each = 10 casings per launch x 10 launches = 100 casings required. This is casing, not propellant. The casings are refurbished and refilled. My understanding is that the internal configuration of the propellant differs between the 4 segment STS booster and the 5 segment Ares/SLS booster.

[Zed_Noir]

I'm curious, in Chris's article, it states there are enough SRB material to support 10 missions.  Does that mean using the existing 4 seg material for the new 5 seg boosters?

My understanding is yes. There are at least 100 casing segments available, but less than 110. Two boosters X 5 casings each = 10 casings per launch x 10 launches = 100 casings required. This is casing, not propellant. The casings are refurbished and refilled. My understanding is that the internal configuration of the propellant differs between the 4 segment STS booster and the 5 segment Ares/SLS booster.

I thought the SRBs for the SLS is not going to be recovered?

[sdsds]

There are at least 100 casing segments available [...] The casings are refurbished and refilled.

I thought the SRBs for the SLS is not going to be recovered?

Correct. There is no plan to recover them after SLS flights.

My understanding is that the internal configuration of the propellant differs between the 4 segment STS booster and the 5 segment Ares/SLS booster.

It isn't a matter of going back to 4 segment RSRM boosters. That's not going to happen. But the five segment RSRMV design would apparently also perform well with the center segment removed (the so-called RSRMV-1). I think one compelling desire though is to get as much flight data as possible on the five segment design. So even if early missions didn't need five segments of solid booster impulse they would still be flown that way. (Plus, certifying the RSRMV-1 would almost certainly require one or more ground test firings.)

So I think it's 10 flights combined of Block 1 and Block 1B before the existing inventory of steel cases are expended. But frankly I would look with suspicion on any claim that qualifying new-built steel cases for use in the RSRMV would be costly or time consuming....

[STS Tony]

Thought it might be prudent to create a thread for the SLS Block 1B since it often strays off topic in others.  After hearing lots of discussions about other variants it seems like this is the most straight forward path to creating the most capable LV.  How much more cost effective is it when compared to the 1A?  Does it free up enough funding for other payloads?

-Khad

The SLS guys have spoken about this in L2 a lot. I think they prefer to only talk in there, so you might need to wait for Chris to do another article if you're not a L2 member, and if not you should be

[Lobo]

So 1B means a delay in any competitive procurement for SLS. The upper stage would be designed and built under the Boeing "stages" contract. RS-25 engines would come from PWR; there is no other supplier. Ditto (presumably) for RL-10 engines. RSRMV can only come from ATK. Only 1A involves a competitive procurement of an "advanced" booster. (I place "advanced" in scare quotes because IMHO it would be fine if ATK offered new steel cases for additional boosters.)

But maybe you wanted to discuss 1B without discussing how it would be procured?

Yea, I’ve wondered why NASA seems to be putting so much money/time into both Block 1B and 1A.  If the advanced boosters would be put off so far, why award the study contracts for advanced liquid boosters they have?  Seems like they’d wait until they’ve finished their evaluations on which path forward before they started doing that.

But maybe there’s some organizational reason they need to pursue 1A to a certain point, and those awards are a part of that?

Anyway, just wild speculation here, if they go with Block 1B, I figure liquid advanced boosters would be put off for like 10 years, while they develop the 1B stage.  Then they’d do a study between restarting steel SRB casing production, advanced solids, and LRB’s.
It might not be a competition per se, but more like some rough budget numbers.  I would imagine restarting production of the steel casings would be the least expensive option, and they’d go with that, shelving both advanced solid and advanced liquid.  As we saw with STS, once they have something in place, NASA is very reluctant to make any major changes.  Small, incremental improvements, yes.  But they’d been studying swapping SRB’s for LRB’s for most of the time STS was flying and it never happened.  I have a hunch once 5-segs are flying for 10 launches, it will be baked into the cake enough that they’ll stick with it, despite the safety and performance advantages of LRB’s. 
Although, depending on what ATK proposes for advanced boosters, there might be a case for going to the advanced boosters after the 10 5-segs have flown, because after that –something- will have to start being produced again, old steel casings, or new composite casings.  And advanced solids would likely be very similar with size and weight to 5-segs, so they probably could be swapped in with very minimal impact on the whole process compared to LRB’s.  I will –guess- that they’d be transported the same way from Utah to Florida, handled and stacked all the same way they’d be doing for the steel SRB’s, and fit right into all the existing scaffolding in the VAB, and match up perfectly with the flame ports and umbilicals on the ML.  They’d have to re-qualify them, but the impact on the whole system would be pretty minimal I would think. So there might be a study to restart steel casing production vs. swapping over to advanced solids at that time.  If the decision is made to restart steel casings, we probably won’t see any swap to anything else for a long time, if ever. 

[MP99]

Yea, I’ve wondered why NASA seems to be putting so much money/time into both Block 1B and 1A.  If the advanced boosters would be put off so far, why award the study contracts for advanced liquid boosters they have?  Seems like they’d wait until they’ve finished their evaluations on which path forward before they started doing that.

But maybe there’s some organizational reason they need to pursue 1A to a certain point, and those awards are a part of that?

Maybe they just don't have enough hard engineering data at the moment to be able to quantify the impacts on SLS's core & payloads of the various options. Advanced boosters would give both core & payload (& crew) a bit of stick compared to the gentler thrust profile of the less powerful boosters with greater burnout mass with an upper stage on top.

While Block 1B has the advantage of BLEO capability and 100t+ LEO all-in-one (instead of both budgeting both advanced boosters and CPS), that's not to say some show-stopper won't come out of the woodwork. It makes a lot of sense to me to understand the trades in enough depth to make an informed decision between the two options.

Anyway, just wild speculation here, if they go with Block 1B, I figure liquid advanced boosters would be put off for like 10 years, while they develop the 1B stage.

IIRC Chris' article said Block 1B would move advanced boosters back to the 2030s.

Quite frankly, this makes sense to me. Congress set the programme up such that SRBs would be used in the initial vehicle configuration. NASA can either budget continuous upgrades of SLS for the next decade-and-a-half, or build something that works well enough and then switch the budget over to actual missions.

cheers, Martin

[TomH]

I thought the SRBs for the SLS is not going to be recovered?

These are casings that already have been recovered from STS use and are going to be refilled. They will be refilled in a differing internal pattern. They will not be recovered again. Some have said that even with the different pattern, the center of the five could be removed and flown in a 4 segment arrangement. How that would compare/contrast to thrust profile of the STS configuration, I do not know.

[HappyMartian]

I think it makes sense to quote the article Chris Bergin wrote regarding the definition of "Block 1B."

notes on the L2 SLS section [...] have revealed a Block 1B configuration, one that continues to use RSRMV (solid) boosters, an 8.4m core with four RS-25D/E engines, an 8.4m Cryogenic Propulsion Stage with four RL10A-4-2 engines, and either an Orion MPCV or a payload under a 8.4m fairing. This vehicle would also be aiming to launch 105mt to LEO. However, the new stage can perform part of the ascent as well as TLI (Trans Lunar Injection).

The notes add that there are enough RS-25D engines in stock to support four missions, and enough RSRMV material (casings, etc.) to support 10 missions.

Selecting the SLS Block 1B over the Block 1A would result in delaying the advanced boosters until the 2030s, depending on the flight rate that is to be determined by the currently undefined Exploration Roadmap.

....

Why "an 8.4m Cryogenic Propulsion Stage with four RL10A-4-2 engines" and not six RL10A-4-2 engines like the J-246SH?

Will the four RL10A-4-2 engines eventually be replaced by four RL-60s/MB-60s or four Next Generation Engines?

 
"Mitsubishi Heavy Industries (MHI) and Pratt & Whitney Rocketdyne (PWR) have been co-developing the MB-60 cryogenic upper stage engine since 1999. This engine is sized to provide 267 kN (60 Klbf) of vacuum thrust using liquid hydrogen and liquid oxygen propellants. Key features of this engine include: robust/reliable design, high specific impulse, low weight, and multi-restart capability all combined in an affordable package. On the MB-60 engine, these design objectives are satisfied by combining components that draw on key technologies integrated into a system that is powered using the expander-bleed (or open expander) cycle."

And, "This paper serves to document the world class capability of the MB-60 engine and establish its readiness for continued development."

From: The MB-60 Cryogenic Upper Stage Engine - A World Class Propulsion System  By William Sack, Kenji Kishimoto, Akira Ogawara, Kimito Yoshikawa, and Masahiro Atsumi    2009 
At: http://archive.ists.or.jp/upload_pdf/2009-a-03.pdf



And thanks to:

at the thread Air Force's "Next Generation Engine" program (RL10 replacement?)

Propulsion  "Next Generation Engine (NGE)" "MB-60 Engine" Page 25 of
A Study of CPS Stages for Missions beyond LEO   By Mark Schaffer May 16, 2012
At: http://spirit.as.utexas.edu/~fiso/telecon/Schaffer_5-16-12/Schaffer_5-16-12%20Rev%20A.pdf
 

[oldAtlas_Eguy]

A misconception is occuring here. One of the 4 segments cassings of the SRB is a specialized cassing that goes only on the bottom. The other three are basiclly interchangable. So with 104 casings a set of 26 total 4 segment boosters, there are 26 specialized nozzel segments and 78 generic segments. That is only enough generic segments to create 19 complete 5 segment boosters or 9 flight sets of 2 (one spare booster).

Another 4 segment booster added to the total a 27th booster for a total of 108 segments would allow the creation of 20 5 segment boosters. Normally these guys come in pairs not singles.

9 flights would be one flight 2017 another in 2019 and then 1 per year through 2026. A new advanced SRB or LRB development must (using NASA's long development cycle of 8 years for such things) start in 2018 to allow for flights in 2027. From a budget point of veiw easily doable.

A side note is that four more sets of flight hardware can be done if 10 generic steel casings are manufactured before 2026 (there are four additional sets of nozzel cassings and caps not used with the first 9 sets of 5 segment SRB's as well as 6 generic cassings not used), alowing flights through 2030.

[Hyperion5]

I think it makes sense to quote the article Chris Bergin wrote regarding the definition of "Block 1B."

notes on the L2 SLS section [...] have revealed a Block 1B configuration, one that continues to use RSRMV (solid) boosters, an 8.4m core with four RS-25D/E engines, an 8.4m Cryogenic Propulsion Stage with four RL10A-4-2 engines, and either an Orion MPCV or a payload under a 8.4m fairing. This vehicle would also be aiming to launch 105mt to LEO. However, the new stage can perform part of the ascent as well as TLI (Trans Lunar Injection).

The notes add that there are enough RS-25D engines in stock to support four missions, and enough RSRMV material (casings, etc.) to support 10 missions.

Selecting the SLS Block 1B over the Block 1A would result in delaying the advanced boosters until the 2030s, depending on the flight rate that is to be determined by the currently undefined Exploration Roadmap.

....

Why "an 8.4m Cryogenic Propulsion Stage with four RL10A-4-2 engines" and not six RL10A-4-2 engines like the J-246SH?

Will the four RL10A-4-2 engines eventually be replaced by four RL-60s/MB-60s or four Next Generation Engines?

Actually why not just make the entire stage modular?  There's a possibility, if the engines were spaced out properly, that NASA could give itself a relatively easy upper stage upgrade option.  It might be able to stick a fifth US engine in between the four other ones as a minimal upgrade option.  It'd look a bit like a Falcon 5 or Saturn V layout.  Alternative possibilities with that layout would include 7 and 9 engines, which should see any SLS overtake the Saturn V in LEO payload lift. 

If you can make the stage upgradable in terms of engine count and there's enough space to accept larger engines in the same format, you could have a lot of flexibility in the design.  I wonder if the guys working on the SLS Bloc IB have considered the possibilities of simply modifying the Bloc IB's CPS as needed for heavier payloads.  They could probably avoid the need for J-2X engines on the second stage that way if Mars missions required some serious performance upgrades (provided the boosters are upgraded).

[RotoSequence]

They could probably avoid the need for J-2X engines on the second stage that way if Mars missions required some serious performance upgrades (provided the boosters are upgraded).

I keep seeing this point come up over and over again - using the RL-10 and derivatives to power the upper stage of the SLS as was recommended by Direct, but after investing millions and millions of dollars developing J-2X, which I have the impression of being a powerful and capable rocket engine, why on earth wouldn't NASA want to use it for the upper stage of the SLS?

[Lobo]

A misconception is occuring here. One of the 4 segments cassings of the SRB is a specialized cassing that goes only on the bottom. The other three are basiclly interchangable. So with 104 casings a set of 26 total 4 segment boosters, there are 26 specialized nozzel segments and 78 generic segments. That is only enough generic segments to create 19 complete 5 segment boosters or 9 flight sets of 2 (one spare booster).

Another 4 segment booster added to the total a 27th booster for a total of 108 segments would allow the creation of 20 5 segment boosters. Normally these guys come in pairs not singles.

9 flights would be one flight 2017 another in 2019 and then 1 per year through 2026. A new advanced SRB or LRB development must (using NASA's long development cycle of 8 years for such things) start in 2018 to allow for flights in 2027. From a budget point of veiw easily doable.

A side note is that four more sets of flight hardware can be done if 10 generic steel casings are manufactured before 2026 (there are four additional sets of nozzel cassings and caps not used with the first 9 sets of 5 segment SRB's as well as 6 generic cassings not used), alowing flights through 2030.

Great info on the 5-segs.  Thanks!

[Lobo]

They could probably avoid the need for J-2X engines on the second stage that way if Mars missions required some serious performance upgrades (provided the boosters are upgraded).

I keep seeing this point come up over and over again - using the RL-10 and derivatives to power the upper stage of the SLS as was recommended by Direct, but after investing millions and millions of dollars developing J-2X, which I have the impression of being a powerful and capable rocket engine, why on earth wouldn't NASA want to use it for the upper stage of the SLS?

Well, as I understand it (which could be wrong) the J2X is really a 2nd stage engine powerful enough and designed to do a significant amount of the ascent through the atmosphere.  It's almost 300K lbs of thrust, and weighs 2.5mt.
The RL-10 is a higher isp engine, lighter, and better for in-space propulsion where isp is king, and not a lot of thrust is needed.
A Block 1B stage with four RL-10's would have 100Klbs of thrust, and mass just over 1mt.
The J2X has 3X as much power and 2.5X the mass of a four RL-10 cluster.

Yes, they spent a lot of money on it.  But that was really under CxP as I understand it, where it was needed for Ares 1.  RL-10 just couldn't do what Ares 1 needed done. 
A block II SLS as they have as the current PoR would need it too for the large 2nd stage.
But...if they go with a Block 1B stage as the PoR for a decade or more, it's just not need, nor even a good choice.   It'd work, but RL-10, which exists and in current production, is a -better- choice.  The'd probably have to throttle it down so it wouldn't accelerate too fast.
RL-10 will cost share with USAF as well. 
RL-10 will be the engine on the iCPS as well, and commercial crew Atlas V/Centaur, so it will already be man-rated.
RL-10 would likely be involved in a lunar architecture, whether as a CECE variant on a lander, or powering a crasher stage. 

I think the deal with J2X, is it was significantly already developed by the time CxP was cancelled.  And there was probably a contract to complete development that couldn't be cancelled until there was a new PoR in place after CxP.  (Or something...these government contracting processes always confuse me)
So, it was probably easier/cheaper/more simple to finish development.  Expecially since they as of now still haven't formally decided on any other SLS version than the current PoR...which calls for a J2X powered LUS for Block 2.  So you might sorta have to keep developing it untill you are 100% sure you DON'T need it.  Otherwise, you need to resstart development, and maybe that has higher cost than just finishing it.

*shrug*.

[TomH]

Well, as I understand it (which could be wrong) the J2X is really a 2nd stage engine powerful enough and designed to do a significant amount of the ascent through the atmosphere.

As I understand it, the vehicle is pretty much in vacuum by the time the J-2 kicks in, but it is still fighting gravity losses, so velocity rather than atmosphere seems to be the variable. Remember that the S-IV on Saturn I had 6 RL-10s with a total of 90k lb. thrust and ISP of 410. The Saturn I could put 19,800 lb. in LEO. The S-IV was replaced with the S-IVB which had a single J-2 @ 232K lb. thrust @ ISP of 421 and could place 41,000 lb. in LEO. On Saturn I-B the single J-2 on the S-IVB was able to place well more than twice the payload to LEO as 6 RL-10s on the S-IV of the Saturn I.

Even on Saturn V, the S-IVB still had to contribute a Delta Vee of over 3000 mph to reach temporary parking orbit before its restart as an EDS, so during that first burn, it was fighting more severe gravity losses than during its TLI burn.

I think the main issue on the Saturn I-B version of the S-IVB is that as an US, its  purpose was to reach LEO, not to be an EDS. The single J-2 was able to fight gravity loss much better than the combined 6 RL-10s. On lunar mission Saturn Vs, if the S-II had been able to place the payload into LEO, perhaps the third stage could have employed an RL-10 as that EDS would not have to fight gravity loss very much during TLI.

It seems to me that what has not been well defined on SLS is whether a second stage would be used

A.) solely for reaching LEO.
B.) solely as an EDS.
C.) as a restartable stage which has a substantial first burn to reach LEO prior to a 2nd (Earth Departure) burn.
D.) as a restartable stage which has a short first burn for circularization prior to a 2nd (Earth Departure) burn.

If the objective is A or C, then the J-2X (ISP 448) would seem better in fighting gravity losses. If the objective is B or D, then the RL-10B2 (ISP 462) has a 14 sec ISP advantage.

Of course any discussion of an upper stage must consider what booster is being used: 5-seg solid, ATK adv. SRB, AJ adv. LRB, Dynetics adv. LRB. ATK just said their advanced SRB could not meet the high profile Mars objectives unless the core uses 5 RS-25Es. The latest from NASA was an intent always to use 4 RS-25s on the core. The more powerful Dynetics booster may have the ability to make any US purely an EDS, thereby enabling a low number of RL-10B2s.

In terms of the J-2X, this engine was going to be used both on the US of Ares I as well as Ares V, so on Ares I the J-2X was facing a fight against gravity losses, while on Ares V those would be less. If memory serves correctly, some ISP had to be sacrificed in order to increase maximum thrust so the underpowered Ares I could reach LEO. This was to the detriment of the engine's use on the Ares V US. Again, if memory is correct, when CxP was cancelled, but J-2X kept alive, there was some discussion about reversing those parameters to that in its use primarily as an Earth Departure engine, J-2X could be pushed back to its earlier specs with a higher ISP. If anyone has details on this, please advise.

[RotoSequence]

As I understand it, the vehicle is pretty much in vacuum by the time the J-2 kicks in, but it is still fighting gravity losses, so velocity rather than atmosphere seems to be the variable. Remember that the S-IV on Saturn I had 6 RL-10s with a total of 90k lb. thrust and ISP of 410. The Saturn I could put 19,800 lb. in LEO. The S-IV was replaced with the S-IVB which had a single J-2 @ 232K lb. thrust @ ISP of 421 and could place 41,000 lb. in LEO. On Saturn I-B the single J-2 on the S-IVB was able to place well more than twice the payload to LEO as 6 RL-10s on the S-IV of the Saturn I.

<additional helpful stuff that's truncated for reasons of length>

That's the kind of detailed explanation I was hoping for. Thanks

[sdsds]

Elsewhere

Ed Kyle has made a compelling case for an SLS derived launcher with a single J-2X powering an appropriately sized middle stage topped by a DIVH derived iCPS. For a single launch that's going to be difficult to beat. The engine count is low (leading to high reliability) and the performance would be darn awful good.

In a dual launch architecture you could take that same single J-2X middle stage and put a single-use depot on top (replacing the iCPS and payload). Then when the payload is delivered to LEO by the second launcher (a Block 1 SLS) the J-2X stage could be reloaded with propellant from the depot. After dropping the depot and docking with the payload, J-2X might be a well sized engine for the LEO departure burn. No need for the "advanced" booster competition, though of course it could only improve performance over flying more steel-case RSRMV.

(I'm guessing the IMLEO of the docked stack could be as high as 150 tonnes, half of which would be propellant for the departure burn. It would be nice to do the maths for that, though!)

EDIT to add:

Read this:

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110015783_2011016690.pdf

More particularly, read the "Engine Implications" slide on page 9.

[MP99]

They could probably avoid the need for J-2X engines on the second stage that way if Mars missions required some serious performance upgrades (provided the boosters are upgraded).

I keep seeing this point come up over and over again - using the RL-10 and derivatives to power the upper stage of the SLS as was recommended by Direct, but after investing millions and millions of dollars developing J-2X, which I have the impression of being a powerful and capable rocket engine, why on earth wouldn't NASA want to use it for the upper stage of the SLS?

Well, as I understand it (which could be wrong) the J2X is really a 2nd stage engine powerful enough and designed to do a significant amount of the ascent through the atmosphere.  It's almost 300K lbs of thrust, and weighs 2.5mt.
The RL-10 is a higher isp engine, lighter, and better for in-space propulsion where isp is king, and not a lot of thrust is needed.

RL-10 has higher Isp for the in-space portion, but you have to remember that J-2X's higher thrust would probably allow a larger total u/s + payload mass to make it to orbit. You'd expect the RL-10 u/s to be gravity-loss limited during the ascent phase. [Edit: as per TomH's post #16]

To a large extent that could compensate for greater dry mass of the J-2X (and the associated larger tank structure).

But...if they go with a Block 1B stage as the PoR for a decade or more, [J-2X is] just not need, nor even a good choice.   It'd work, but RL-10, which exists and in current production, is a -better- choice.  The'd probably have to throttle it down so it wouldn't accelerate too fast.
RL-10 will cost share with USAF as well.

I suspect that T/W at burnout is indeed the determining factor that selects RL-10 over J-2X - low thrust is set out as a requirement in the NTRS documents on CPS [edit: which I now see sdsds has posted just above this]. Although J-2X can throttle, it can't get down to RL-10 levels.

cheers, Martin

Edit: really must remember to read subsequent posts before speaking myself.