What is the best path to a 130 ton (Block II) SLS?

[spectre9]

NASA is being urged to accelerate development of 130 ton configuration.

The 70mt+ SLS will only be used for test flights.

So how should NASA go about this?

Upgrade to 5 engines?

Go with F-1 liquid boosters?

The current plan is 2 flights with 5-seg boosters and 4 flights with the ICPS.

Will NASA have to start work on the upper stage early?

Block 1A/B might not have the performance to meet the mandate.

[MATTBLAK]

NASA should only build either the 70 metric ton version or the full 130 ton version - they shouldn't mess with in-between.

(This could potentially be a very interesting thread! But: I'm really afraid that a few posts after this, someone will be mentioning the 'Elephant in the Room' - this fine website (I believe the best of its type) nonetheless has some very active SLS-haters who will invade every thread about it, push it off course and end up causing it to be locked).
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I'm certainly willing to stay on topic including - hopefully - the kind of payloads and missions the 130 ton Block II version would be best for.

[MATTBLAK]

I think they'll always keep to a 4 engine Core. Since lightweight Alum/Lith is now out of the question, future upgrades might have to include the RS-25's capable of '114 or 115%' percent thrust and advanced boosters of the ATK all-composite type or the liquid boosters.

The cheapest (there probably is no 'best' - you're asking for an argument around here) way to get close to the 130 ton mark is to use 5 meter Delta IV tooling for the liquid boosters. And the engines? It remains to be seen which would be cheaper, development cost wise: Clustered Aerojet AJ26-500s or pairs of PWR F-1Bs. The cheapest upper stage might be a stretched Delta IV upper stage with 2x RL-10s - the current one only uses 1x engine and other alternatives might be 2x MB-60s instead.

I only didn't mention the J-2X for budgetary reasons - it would require an all-new stage and I doubt that engine could just 'drop in' to another existing stage. If there had to be a budgetary 'sacrificial lamb' for SLS - I vote the J-2X and its unique stage.

Now; I'm not qualified to (accurately) crunch the numbers for the various configs but can anyone else around here do that?

1# - SLS 4x RS-25 corestage with 2x ATK 'black' composite SRBs & twin engined Delta IV upper stage (2x RL-10B2)
2# - As above, but with 2x MB-60s in upper stage.
3# - SLS with 2x liquid boosters; each with 4x AJ26-500 engines and 2x RL-10B2 upper stage.
4# - As above, but upper stage with 2x MB-60s.
5# & 6# - SLS with liquid boosters powered by 2x F-1B and the two upper stage engine options.

'Rocket Lego' - here we go again!!

[Hyperion5]

I think they'll always keep to a 4 engine Core. Since lightweight Alum/Lith is now out of the question, future upgrades might have to include the RS-25's capable of '114 or 115%' percent thrust and advanced boosters of the ATK all-composite type or the liquid boosters.

The cheapest (there probably is no 'best' - you're asking for an argument around here) way to get close to the 130 ton mark is to use 5 meter Delta IV tooling for the liquid boosters and the engines? It remains to be seen which would be cheaper, development cost wise: Clustered Aerojet AJ25-500s or pairs of PWR F-1Bs. The cheapest upper stage might be a stretched Delta IV upper stage with 2x RL-10s - the current one only uses 1x engine and other alternatives might be 2x MB-60s instead.

Cheapest is probably a Bloc IB SLS upgraded with advanced SRBs, though if you're looking for the cheapest long-term operating costs and cost per kg to orbit, you'd be hard-pressed to beat a Bloc IB upgraded to Bloc II with a pair of F-1B boosters.  The stack would be much lighter, it wouldn't require any special handling, and you wouldn't have to worry about the mandate.  A Bloc II like that would put up 155 mt into LEO, and even advanced SRBs should get you to 133 mt into LEO at a minimum.  It looks to me like it will only take NASA a pair of upgrades to meet the mandate, so I'm not too worried.  I'd prefer a pair of LRBs, because that'd give handling and performance bonuses, but you can meet the mandate with only two upgrades even with ATK's composite SRBs (see Chris' story and thread on "Black Knights"). 

I only didn't mention the J-2X for budgetary reasons - it would require an all-new stage and I doubt that engine could just 'drop in' to another existing stage. If there had to be a budgetary 'sacrificial lamb' for SLS - I vote the J-2X and its unique stage.

Already been sacrificed according to another poster and a Boeing report, or at least the two J-2X 2nd stage below the upper stage.  The Bloc II SLS as it stands right now is envisioned as a Bloc IB (four RL-10 engine upper stage upgrade of Bloc I) with more powerful advanced boosters.  Only the Bloc IIA SLS is envisioned with a single J-2X engine upper stage, and with a pair of F-1B engines and the Bloc I SLS core, you can fling up 178 mt into LEO.  The catch is that it isn't as capable in BEO flight compared to a Bloc II SLS with the same boosters and the IB's upper stage.  J-2X only gets you to 58 mt through TLI compared to 61 mt with the other upper stage. 

Now; I'm not qualified to crunch the numbers for the various configs but can anyone else around here do that?

1# - SLS 4x RS-25 corestage with 2x ATK 'black' composite SRBs & twin engined Delta IV upper stage (2x RL-10B2)
2# - As above, but with 2x MB-60s in upper stage.
3# - SLS with 2x liquid boosters; each with 4x AJ26-500 engines and 2x RL-10B2 upper stage.
4# - As above, but upper stage with 2x MB-60s.
5# & 6# - SLS with liquid boosters powered by 2x F-1B and the two upper stage engine options.

'Rocket Lego' - here we go again!!

Boeing's way ahead of you on some of this.  I summed up their report on currently envisioned SLS variants here: http://forum.nasaspaceflight.com/index.php?topic=30554.180

Here's another summary for everyone:

SLS Bloc I
Core Stage (4 SSMEs)+iCPS (Modified Delta IV 2nd stage with 1 RL-10B-2)
Payload to LEO: 70 mt (Ed Kyle's estimate: 90 mt)
BEO Payload: 19 mt
Year available: 2017

SLS Bloc IA
Core Stage+advanced boosters (appears to be LRBs)-upper stage
Payload to LEO: 105 mt
BEO Payload: 0 mt
Year available: 2022 (if advanced booster program is funded)

SLS Bloc IB
Core stage+8.4 m CPS (8.4 m stage with four RL-10 engines)
Payload to LEO: 118 mt
BEO Payload: 43 mt
Year available: 2019 (if upper stage is funded)

SLS Bloc II
Core stage+8.4 m CPS (from Bloc IB)+advanced boosters (LRBs)
Payload to LEO: 155 mt
BEO Payload: 61 mt
Year available: 2022 (if boosters+CPS are funded)

SLS Bloc IIA
Core stage+8.4 m J-2X stage+advanced boosters (LRBs)
Payload to LEO: 178 mt
BEO Payload: 58 mt
Year available: 2027 (if boosters+J-2X stage funded)

[TomH]

I think any upper stage needs to be solely an Earth Departure stage (whose mass is included in the 130 mT "payload"). The core needs to reach a V which requires nothing more of the "payload" than a circularization burn. A 5th RS-25 may burn through the HydroLox too fast and require a US burn to reach LEO. This almost certainly requires use of J-2X. It would seem to this rank amateur that the best way to reach LEO is a 4 engine core with the Dynetics boosters. Now, any US is strictly for Earth departure and can employ an RL-10 variant. With little gravity loss to fight, number of engines (and engine mass) is kept down while ISP is high.

It would seem that any other path is somehow going to require either two upper stages (2nd to reach LEO and 3rd as Earth departure) OR use of a second stage whose 1st burn contributes significant ΔV to reach parking orbit and whose 2nd burn is for Earth departure (much like S-IVB on Saturn V). The thing is, both of these scenarios require J-2X and neither takes full advantage of RS-25's qualities as a sustainer all the way to orbit.

Since advanced boosters are going to be required anyway, it just seems logical to get the maximum total thrust possible out of boosters by going Dynetics 5.49 m dual F-1B, get that 130 mT to LEO with nothing more than boosters and 4 engine core, then have a single US whose sole purpose is as EDS and which can let RL-10 do what it does best-depart LEO yet not have to assist in reaching LEO. J-2X is not used.

If components are to be assembled @ LEOR, the US will not always be part of the stack. Let's say the 1st phase of a Mars mission is being assembled; that unmanned assembly may then be sent on slow departure via SEP, prior to later manned portion of the mission.

[MATTBLAK]

So foregoing an 8.4 meter EDS all together; would a 'Super-stretched' Delta IV upper stage holding 45-50 metric tons of propellant and powered by a pair of RL-10B2 or MB-60 engines be good enough to a 35-40 metric payload BEO?

[93143]

Why RL-10?  By the time CPS flies, won't the Air Force have switched to the NGE?

[MATTBLAK]

Well I really hope so - but with budget cuts and delays, I'm hedging my bets against it not coming to pass. I only mentioned the Mitsubishi MB-60 because it has similar thrust levels, performance and was mostly developed (like the RL-60).

[hkultala]

I think they'll always keep to a 4 engine Core. Since lightweight Alum/Lith is now out of the question, future upgrades might have to include the RS-25's capable of '114 or 115%' percent thrust and advanced boosters of the ATK all-composite type or the liquid boosters.

The cheapest (there probably is no 'best' - you're asking for an argument around here) way to get close to the 130 ton mark is to use 5 meter Delta IV tooling for the liquid boosters. And the engines? It remains to be seen which would be cheaper, development cost wise: Clustered Aerojet AJ26-500s or pairs of PWR F-1Bs. The cheapest upper stage might be a stretched Delta IV upper stage with 2x RL-10s - the current one only uses 1x engine and other alternatives might be 2x MB-60s instead.

'Rocket Lego' - here we go again!!

2 RL-10's is too little thrust to be as an upper stage for reaching orbit for such big rocket.

It the upper stage has to do 2km/s impulse,
accelerating just 130 tonne payload + means it would have to be accelerating for 1182 seconds = 19 minutes just to accelerate the payload. But it also has to accelerate itself and the initial fuel(more than 60 tons to have enough fuel for such long burn), so it becomes something like 27 minutes.

So the gravity losses would be terrible, and might be too bad that it might not reach orbit. Such weak second stages only work for really small orbit circularization burn and as EDS stage.

It the upper stage only had 1km/s job to do, then it would still need something like 13 minutes burn with 2 RL-10's.

[MATTBLAK]

That's all true. So we're back to the MB-60 or RL-60 again. I doubt that 4x RL-10 would fit on the 5 meter Delta IV upper stage without major redesign, taking it into clean-sheet territory.

[Ben the Space Brit]

That's all true. So we're back to the MB-60 or RL-60 again. I doubt that 4x RL-10 would fit on the 5 meter Delta IV upper stage without major redesign, taking it into clean-sheet territory.

Four RL-10B-2s could fit on an 5.4m-diameter ACES stage, so four of the smaller (and crew-rated) A-4s should definitely fit on the 5.1m-diameter DIVHUS.  There would probably have to be a modest tank length stretch, though.

[RotoSequence]

NASA is being urged to accelerate development of 130 ton configuration.

They are? Do you have a link?

[ChileVerde]

NASA is being urged to accelerate development of 130 ton configuration.

They are? Do you have a link?

Not to step in for spectre9, but

http://spaceref.com/news/viewsr.html?pid=43563

Explanatory Statement for the Senate Substitute Continuing Resolution (NASA Excerpts)

    Source: Senate Appropriations Committee
    Posted Tuesday, March 12, 2013

<snip>

SLS vehicle development.-- Support for NASA's evolvable SLS development approach, which will provide a 70 ton SLS configuration by 2017 and build to a 130 ton configuration as work is completed on an upper stage and advanced booster system, is reiterated. However, NASA is urged to identify and implement ways to accelerate the schedule for the attainment of the 130 ton configuration. To enable better congressional oversight of NASA's progress, language from the House report regarding requirements for quarterly SLS funding reports is adopted by reference.

<snip>

Further discussion of this is probably best done on the politics forum, where I think I'll start a thread about it.

[spectre9]

http://forum.nasaspaceflight.com/index.php?topic=28750.msg1025223#msg1025223

It's in the CJS statement. This thread is just to discuss the hardware.

NASA might be forced to redesign their block upgrade path.

I say just go for LRBs from the start but they might want to upgrade to 5 engines early to make sure advanced solids can meet the performance requirements.

Once you start using more and more engines you become less efficient than a RAC2 (Saturn V) style vehicle which is what I don't like.

[Lobo]

NASA is being urged to accelerate development of 130 ton configuration.

The 70mt+ SLS will only be used for test flights.

So how should NASA go about this?

Upgrade to 5 engines?

Go with F-1 liquid boosters?

The current plan is 2 flights with 5-seg boosters and 4 flights with the ICPS.

Will NASA have to start work on the upper stage early?

Block 1A/B might not have the performance to meet the mandate.

Hyperion5 beat me to it and stole my thunder.  But X2 on all he said!  Well said Hyperion.  To the performance options he listed at the bottom, add a Block II with ATK advanced SRB’s at about 133mt to LEO.

Block 1 will be over 90mt, not 70mt like they are “officially saying”.  Take a look at LV26 and LV27 studied under ESAS.  LV26 is the crew+cargo version, and was rated at 91.3mt to 28.5 deg inc.  And LV27 was the cargo only version rated at 96.7mt to 28.5 deg. Inc.  They both have four RS-25’s on stretched cores with 5-seg SRB’s.  Neither has the iCPS though, they basically do the full insertion burn with the core I’m assuming, or they assume the payload does the circ burn. With the ICPS doing a bit of the ascent burn, it might actually improve the full LEO payload closer to the 100mt side of that range.

Because of Block 1’s real performance, I’m assuming that’s why Boeing is stating Block 1B’s real performance will be 118mt.  ATK’s advanced solids supposedly will add about 15mt to the LEO capacity of SLS,  That puts that “Block II” capacity at 133mt at least.  And there you are.

So what will “Block II” look like?  I’m over 90% sure Block II will be Block 1B with the single upgrade of advanced boosters over the defunct 5-seg SRB’s (defunct because the equipment doesn’t exist any more to make more casings.)  This has a lot of advantages I think NASA is realizing over their current PoR Block II, which I think will be axed as soon as NASA gets around to formally announcing their new official plans. 
Four RS-25’s on the stretched core means the core can fly all the way to orbit.  Adding a 5th RS-25 means you need the upper stage to do a large part of the ascent.  Which basically negates the advantage of using a hydrolox sustainer stage, which is to make it basically a ground lit 2nd stage.  Putting too many engines on it and needed a large 2nd stage powered with J2X engines to get to LEO just blows out the advantages of that system.  Might as well scrap the boosters entirely and make the 8.4m core kerolox with new F-1 engines if you are going to have a J2X powered 2nd stage.  Be more simple and probably cheaper than the current PoR Block II.  So use the system as it was meant to be used.  And I think they are seeing that out now.
That means the core MPS doesn’t need redesigned for the 5th RS-25…which is a decent savings.  That also means the J2X powered new large upper stage is deleted completely.  Which is a substantial savings.  It also means the core designed for block 1B loads should be able to handle the block II loads because the stack wont’ be any taller.  I’ve heard they are designing the core from the start with at least the Block 1B loads in mind.  And that, that might be able to handle Block II loads as well, if the stack isn’t any longer.  Which it shouldn’t be…or at least not much.  The PLF might be a little longer.  But who knows?  Maybe NASA it throwing in some margin into Block 1B so that it will also handle the extra loads of Block II payload mass and a little longer PLF.  If they really want to add advanced boosters to Block 1B, that would make sense.

I like LRB’s, but since ATK’s advanced solids will get this “Block II” over 130mt, I really don’t see how they aren’t chosen over brand new LRB’s.  They’ll basically be drop in replacements, so all of the equipment and infrastructure that will be there to handle the 5-segs can stay in place.  They’ll be able to use the existing SLS ML, where LRB’s will require a new ML (so I’ve heard).  So unless ATK just goes nuts on their proposed costs, I don’t see how they don’t get chosen just from the existing infrastructure cost savings.
But who knows.  Certainly a pair of Dynetics boosters bringing back the old F-1’s again get me excited.  I just think they’d have to come in dirt cheap to really look better than advanced solids.  And I don’t know how you can make a brand new 5.49m booster with two quasi-brand new liquid engines each for super cheap.  But I wish them luck.

[newpylong]

Well said!

[RyanC]

I only didn't mention the J-2X for budgetary reasons - it would require an all-new stage and I doubt that engine could just 'drop in' to another existing stage. If there had to be a budgetary 'sacrificial lamb' for SLS - I vote the J-2X and its unique stage.

Not really. We already have a large diameter 8.4m hydrolox stage -- the SLS Core Stage. Design a shortened version that uses J-2X.

Results: we use the SLS CS tooling to produce not one, but two stages. Everyone is happy.

[TomH]

I only didn't mention the J-2X for budgetary reasons - it would require an all-new stage and I doubt that engine could just 'drop in' to another existing stage. If there had to be a budgetary 'sacrificial lamb' for SLS - I vote the J-2X and its unique stage.

Not really. We already have a large diameter 8.4m hydrolox stage -- the SLS Core Stage. Design a shortened version that uses J-2X.

Results: we use the SLS CS tooling to produce not one, but two stages. Everyone is happy.

The question remains whether this 8.4 m US is going to be placed in near LEO by the core or whether a significant burn by this stage is required to reach parking orbit.

If this stage requires a significant first burn to reach parking orbit, that requires J-2X. The RS-25s are not used to their full advantage as sustainers. The second J-2X burn for Earth departure does not have the best ISP and a high mass engine is absorbing more of the thrust than an RL-10 variant.

If this second stage attains significant V from the core, the US engine needs only to do a circularization burn and an Earth departure burn, thus an RL-10 variant is a much better engine.

Any US which by itself is designed to contribute significant ΔV to LEO and then do an Earth Departure burn is an US that is not able to contribute to component assembly via LEOR. The S-IVB version used on Saturn V worked well for the LOR approach. It would not have worked so well in an EOR approach. What do you do with several half fueled H2 upper stages?

The SLS core needs to be able to accelerate everything stacked above that core to almost orbital V; the core falls into the ocean and a small circularization burn stabilizes the payload. This way, a dedicated US with high ISP/low mass (RL-10 variant) engine could provide the ΔV for a single stack lunar mission, while for LEOR component assembly the stage is not utilized.

I am no rocket scientist, yet from my POV, it seems that J-2X provides no utility in a scheme that also involves EOR assembly.

[Lobo]

I only didn't mention the J-2X for budgetary reasons - it would require an all-new stage and I doubt that engine could just 'drop in' to another existing stage. If there had to be a budgetary 'sacrificial lamb' for SLS - I vote the J-2X and its unique stage.

Not really. We already have a large diameter 8.4m hydrolox stage -- the SLS Core Stage. Design a shortened version that uses J-2X.

Results: we use the SLS CS tooling to produce not one, but two stages. Everyone is happy.

The question remains whether this 8.4 m US is going to be placed in near LEO by the core or whether a significant burn by this stage is required to reach parking orbit.

If this stage requires a significant first burn to reach parking orbit, that requires J-2X. The RS-25s are not used to their full advantage as sustainers. The second J-2X burn for Earth departure does not have the best ISP and a high mass engine is absorbing more of the thrust than an RL-10 variant.

If this second stage attains significant V from the core, the US engine needs only to do a circularization burn and an Earth departure burn, thus an RL-10 variant is a much better engine.

Any US which by itself is designed to contribute significant ΔV to LEO and then do an Earth Departure burn is an US that is not able to contribute to component assembly via LEOR. The S-IVB version used on Saturn V worked well for the LOR approach. It would not have worked so well in an EOR approach. What do you do with several half fueled H2 upper stages?

The SLS core needs to be able to accelerate everything stacked above that core to almost orbital V; the core falls into the ocean and a small circularization burn stabilizes the payload. This way, a dedicated US with high ISP/low mass (RL-10 variant) engine could provide the ΔV for a single stack lunar mission, while for LEOR component assembly the stage is not utilized.

I am no rocket scientist, yet from my POV, it seems that J-2X provides no utility in a scheme that also involves EOR assembly.

I think Block 1B is pretty much going with four RL-10’s.  Boeing looked at J2X on the Block 1B stage, but basically made the argument that four RL-10’s was better from pretty much every direction.  Lead time, cost, performance, etc. 

Like you said, the RS-25’s are great engines with great vacuum performance.  Let them do the work for as long as they can.  Just do the last little bit of the ascent with the Block 1B stage after dumping the core is disposal orbit, around the same place the Shuttle dumped the ET.  Four engines are optimal for that with the stretched core, where three engines would have been for an ET-sized core.  That’s how you take advantage of those expensive but high performance RS-25 engines and the whole sustainer stage concept. 
Which is why I never understood Ares V/LV27.3, the official SLS Block II PoR, or anything that doesn’t allow the core to put everything above it into LEO in a sustainer stage type LV using RS-25’s.

[93143]

The question remains whether this 8.4 m US is going to be placed in near LEO by the core or whether a significant burn by this stage is required to reach parking orbit.

Note that the LEO payload of the Block 1B is quoted as 118 tonnes, more than 20 tonnes higher than Block 1.  So evidently the upper stage is at least capable of burning to orbit if the payload on top is heavy enough to warrant it.

DIRECT's JUS was far too heavy for the core to put it in orbit even with nothing on top.  The result was a larger payload through TLI (in DIRECT's two-launch architecture) than could have been achieved with an in-space stage launched on a J-130.