Author Topic: SLS "Swiss Army Launch System"?  (Read 11344 times)

Offline CNYMike

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SLS "Swiss Army Launch System"?
« on: 02/06/2012 04:46 AM »
I am a little confused about something.

The concept of the SLS is it will "evolve" to 130 mt.  But I thought I read somewhere it will be designed to be confiugred to each mission -- so the full size version for one mission, but the next time maybe the 70mt version will do.  Is the SLS designed so that like an EELV on steroids, that you use the specific configuration you want?  Or does it just get progressively more powerful and not go back?  Because the modular, "swiss army knife" version is the more interesting idea.
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Offline 93143

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Re: SLS "Swiss Army Launch System"?
« Reply #1 on: 02/06/2012 05:05 AM »
I believe the advanced boosters are supposed to improve performance, and that's not reversible.  But there's no reason you have to launch with five engines, a Large Upper Stage and a CPS Block II if all you need is a 70-tonne payload in LEO.  It should be, to a certain extent, a dial-a-rocket (though the bottom end is still pretty hefty).

Older documentation from NASA (the ESD Budget Integration document, notably) does show interleaved launches of the 70 t and 130 t versions in some scenarios.  An even older document noted that configurability with common components has certain advantages that can outweigh the penalty of suboptimality in less-stressed configurations (for instance, a core designed for four engines and a 100-tonne payload is overbuilt for three engines and 75 tonnes, but it's still worth it to not have to design, qualify and maintain two distinct cores).  As far as I am aware, all evidence thus far indicates that the upgrades, with the likely exception of the advanced boosters, are intended to be reversible.
« Last Edit: 02/06/2012 05:16 AM by 93143 »

Offline sdsds

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Re: SLS "Swiss Army Launch System"?
« Reply #2 on: 02/06/2012 05:31 AM »
An even older document noted that configurability with common components has certain advantages that can outweigh the penalty of suboptimality in less-stressed configurations (for instance, a core designed for four engines and a 100-tonne payload is overbuilt for three engines and 75 tonnes, but it's still worth it to not have to design, qualify and maintain two distinct cores). 

Good points but to be fair, the core still needs to be designed to fly in two configurations, which is a more challenging design task than designing for a single configuration.  Arguably, it would be easier to design two different cores than to design a single core that meets both requirements.  Next, the cost to flight-qualify (e.g. by a test flight) seems to be paid per-configuration, not per-design.  So there doesn't look to be much savings there.  But your final point about maintaining a system that uses only one core, versus maintaining a system that uses two distinct cores, is super important and easily overlooked or under-estimated.  USAF introduced the aeronautic terminology of "white tail" cores in the context of NASA and DoD sharing EELV manufacturing infrastructure.

I certainly hope the SLS cores coming off the line at Michoud are going to be "white tail" in the sense that any of them could be flown in any of the vehicle's  configurations.
« Last Edit: 02/06/2012 05:32 AM by sdsds »
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Offline Lobo

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Re: SLS "Swiss Army Launch System"?
« Reply #3 on: 02/06/2012 04:09 PM »
An even older document noted that configurability with common components has certain advantages that can outweigh the penalty of suboptimality in less-stressed configurations (for instance, a core designed for four engines and a 100-tonne payload is overbuilt for three engines and 75 tonnes, but it's still worth it to not have to design, qualify and maintain two distinct cores). 

Good points but to be fair, the core still needs to be designed to fly in two configurations, which is a more challenging design task than designing for a single configuration.  Arguably, it would be easier to design two different cores than to design a single core that meets both requirements.  Next, the cost to flight-qualify (e.g. by a test flight) seems to be paid per-configuration, not per-design.  So there doesn't look to be much savings there.  But your final point about maintaining a system that uses only one core, versus maintaining a system that uses two distinct cores, is super important and easily overlooked or under-estimated.  USAF introduced the aeronautic terminology of "white tail" cores in the context of NASA and DoD sharing EELV manufacturing infrastructure.

I certainly hope the SLS cores coming off the line at Michoud are going to be "white tail" in the sense that any of them could be flown in any of the vehicle's  configurations.

Good points both.  Yea, once we go from Block 1 to Block 1A, 70mt to 105mt without needing a 2nd stage, SLS won't go back.  I have some assumptions, although I dn't know if they'll be the case. 
I think they will drop the 3-engine config.  There was an article here a few months ago saying the trades are looking to open with a 4 engine config.  That makes more sense since the stretched tank should be able to feed 4 RS25's all the way to a disposal orbit, just like 3 RS-25's were fed by the shorter ET on STS, or that the Jupiter core woudl have fed 3 engines on the J-130 to a disposal orbit.  I know it also depends on how they are trhottled and all of that, but if the payload is too light to train the tank in time, balast could be added to get to a defined flight profile, as I understand.
I think if there were only 3 RS25's, they can't drain a full core by disposal orbit, even at full thrust.  Such a config could probably put the payload fully into a circular orbit with that extra fuel burning for longer.  But then you'd need ullage motors to dispose of the core.  Sounds like NASA's not looking at doing that.  So, unless they want to develop and include ullage motors, the 3 engien config probably won't happen.  Or at least I can't see a reason for it.

SO they just develop a MPS that can take either 4 RS25's in a square pattern, or 5 RS25's in a  cross pattern like Saturn V's S-IC and S-II.  This should be much more simple than designing the MPS to take a 3 engine config too, becausewhen only going 4 or 5, they can make the center RS25 fixed, and not gimbaled.  If you try to do a 3 engine config, you have to do a slanted inline or something, and maybe have to gimbal the center engine?  Not sure, but it seems much easier to just go 4 to 5, with a center fixed mount that's blocked off on the Block 1A config. 
So if they that, they should be able to design just one core, with one MPS, and have a center mount that can be fitted with an engine, or left blocked off.
Then Block 1A can get pretty much any paylaod we'd need to a disposal orbit, only needed a little circ burn from the paylaod, whether than be Orion's SMME, or a CPS, or an EELV kick stage, or some other engine built into a payload.  The LUS wouldn't even need to be designed or built until NASA realistically stars looking at larger scale missions like Mars, with the funding for them.

Basically, Block 1A -will- be SLS for many decades, with BLock II being more of a upgrade option on the back burner somewhere for later use.  The central motor mount won't get used for quite some time likely.  Which then begs the option, perhaps the BLock 1 and BLock 1A MPS could be designed to take a central engine, and it'd be designed with the idea of adding it in later, but without the actual plumbing or hardware, but with the space and structural allowences for it.   Like a roughed in bathroom in an unfinished basement.  Then later, when BLock II becomes an actual option, then they can add in the plumbing and structure for that 5th engine.  Then every core to roll off the assembly line would be identical, regardless of if it's being used on a BLock 1A 4-engine launch, or a BLock II 5-engine launch.   

Offline spectre9

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Re: SLS "Swiss Army Launch System"?
« Reply #4 on: 02/06/2012 10:13 PM »
Great post Lobo.

It would be nice to know exactly how many engines on how many variants of the  core the SLS team is planning on building.

The 3/5 upgrade path seems to be what they want to do.

Building 2 different configurations might be costly. Some posters have suggested they might just start with 5 and leave it that way.

Offline edkyle99

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Re: SLS "Swiss Army Launch System"?
« Reply #5 on: 02/06/2012 10:34 PM »
I think if there were only 3 RS25's, they can't drain a full core by disposal orbit, even at full thrust. 
If they use only three RS-25 engines, they can't launch a full core.  It would be too heavy at booster burnout.

Four RS-25 engines works, but that creates a rocket that lifts 95-100 tonnes to the injection orbit with five-segment boosters.  The "70 tonne" rocket was the four segment booster plus smaller core with three RS-25 engines (the "4/3") that is not being developed.  The "70 tonne" language is left over from "4/3", but there is no currently planned rocket design actually fits the description - unless the plan is to build a big core, under power it with only three engines, and fly it with partially empty tanks.

95-100 tonnes is a lot of mass.  It seems to me that once such a rocket is flying, there will be little need for improvement for many years, if ever.  That's why I wonder about the "Phase 1b, Phase 2", etc. ideas.

 - Ed Kyle
« Last Edit: 02/06/2012 10:36 PM by edkyle99 »

Offline woods170

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Re: SLS "Swiss Army Launch System"?
« Reply #6 on: 02/07/2012 08:24 AM »
The "70 tonne" rocket was the four segment booster plus smaller core with three RS-25 engines (the "4/3") that is not being developed.  The "70 tonne" language is left over from "4/3", but there is no currently planned rocket design actually fits the description - unless the plan is to build a big core, under power it with only three engines, and fly it with partially empty tanks.

That was exactly the plan. Ongoing trade studies then introduced the fourth SSME, and thus the opportunity to fly SLS core fully fueled from the get-go. So, they pretty much threw the 70 tonnes version of SLS out-the-window.

Offline Lobo

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Re: SLS "Swiss Army Launch System"?
« Reply #7 on: 02/08/2012 04:55 PM »
I think if there were only 3 RS25's, they can't drain a full core by disposal orbit, even at full thrust. 
If they use only three RS-25 engines, they can't launch a full core.  It would be too heavy at booster burnout.

Four RS-25 engines works, but that creates a rocket that lifts 95-100 tonnes to the injection orbit with five-segment boosters.  The "70 tonne" rocket was the four segment booster plus smaller core with three RS-25 engines (the "4/3") that is not being developed.  The "70 tonne" language is left over from "4/3", but there is no currently planned rocket design actually fits the description - unless the plan is to build a big core, under power it with only three engines, and fly it with partially empty tanks.

95-100 tonnes is a lot of mass.  It seems to me that once such a rocket is flying, there will be little need for improvement for many years, if ever.  That's why I wonder about the "Phase 1b, Phase 2", etc. ideas.

 - Ed Kyle

Ed,

Good catch.  I was thinking that they keep talking about a 70mt, 3 RS25 version, so I keep thining 3 engines cant' drain the tank in time.  But, they were talking about short-filling the core when they talked about a 3-engine, 70mt config.  I supposed if they had powerful enough LRB's they could launch it with only 3 engines, then have the core do the full circ burn and delivery payload into a full LEO orbit.  But then you have to dispose of it with ullage motors.  And it doesn't sound like NASA is going that route.  The BLock 1 SRB's probably wouldn't be able to launch it though, as you said.

And yea, since Direct's J-130 was able to get over 70mt to LEO with 3 RS25's and 4-seg SRB's and a smaller core, SLS with 4 RS25's and 5-seg SRB's would have to be a fair amount more than that.

And as Woods said, it would seem pretty obvious the more "streamlined" path would be for the full 4 RS25's and a full tank from the get go.  SLS core is sized for 4 engines, just as the STS ET and Jupiter core were sized for 3 RS-25's.  Fuel is cheap and you are only tlaking 1 more RS25.  Then you don't have to design your MPS to handle a 3-engine config along with a 4 and 5 engine config. 

I would -think- that it would be much easier to design an MPS that could be set up for 4 engines in a square config, with allowences made for the pluming and structure for the 5 engine at some in the future.  SLS block 1A with (or even Block 1) is all NASA will need for a long time, so the 4-engine config will all that would be needed for awhile.  But still design it so that 5th engine with it's associated structure and plumbing can be addeded in later.  So the MPS will have room for it.  So that it won't require a redesign later.  Design it so the 5th engine with associated equipment can be an option to future MPS's rolling off the assembly line after Block II is flying, so they can add it in or not, depending on what config will be flying for that mission.

This makes sense to me with my limited knowledge of such things anyway.  :-)
They could add water balast or something if the payload was less than 100mt for Block 1/1A so they can light it off fully fueled every time for a consistant flight profile.

AS you say Ed, what will be the need for SLS block 1A (I assume you menat 1A not 1B..unless 1B is something new I've not heard of?) or BLock II?  I can't imagine Block II would be needed prior to a MArs mission, and who knows how long that will be, if ever.  I could see a Block 1A upgrade to LRB's, because it improves your logistics (not training in fueled sections from Utah to Florida), commonality with commercial rockets (hopefully...some engines an barrel sections perhaps anyway) and safety (not fueled until it's on the pad, LRB's can be shut down during a pad abort, or in-flight launch abort).  SO LRB's have a  lot of benefits that some in NASA might be wanting, rather than just stick with being married to ATK again forever. 
However, I could see something playing out where if ATK's offering for an advanced booster was the best( or the thumb's on the scale for it anyway) then they award them the contract, but order up a bunch of block 1 boosters in the mean time to actually carry SLS for a few decades until there might be the need for a BLock II, then just do both upgrades at once.. 

The fact they are entertaining LRB's at all tells me perhaps someone at NASA wants them.  IF NASA really didn't want LRB's, there would be lots of smoke they could blow for not bidding them out competatively, and just giving the contract to ATK.  They could say they have a very lengthy history with NASA HSF, and are well understood, and have a great safety record (only one problem in 271 flights of them?  135 STS flights plus 1 Ares-1X flight) and the infrastructure and logistics are already in place, and the ET/core structure is already designed for the way they booster, and it would cost a lot more time and money to not just stick with the new 5-seg booster since it's already developed and more perforamnce out of them won't be needed until Block II, and yadda yadda yadda...  Thers' lots of things they could say that would sound reasonable to most.  But they seem to be pushing for this booster competition pretty quick, and limiting ATK to just 2 pairs of their new 5-seg Ares/STS heritage boosters.  That seems odd to me unless NASA really liking LRB's.
And they were looking at doing LRB's on the Shuttle for the last few decades for the reasons I mentioned above, but just couldn't get the funding for the switch, as I understand.  So they might be writing the LRB upgrade directly into the "Constitution" of SLS, so that it really happens this time, and isn't put off indefinately again like STS. 

Just some food for thought...

Offline Lobo

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Re: SLS "Swiss Army Launch System"?
« Reply #8 on: 02/08/2012 05:10 PM »
HEre's another interesting possibility.  I don't think NASA is looking at this, but maybe they could at some point.

Assume LRB's are chosen and SLS evolves to BLock 1A.  LEt's say that the LRB's, because of their longer burn time and maybe a little better than required efficiency, and thus overall better performance than advanced SRB's, is able to get 130mt to LEO with 4 RS25's and only a relatively minor boost from an upper stage, rather than a good deal of heavy lifting from a large upper stage as SLS block II is planned to do after the 5-engine core burns out.  SO what if, instead of a new LUS being developed, they do some upgrades to CPS.  Stretch it a little, or whatever.  So it can act more like the JUS, but still perform the CPS duties NASA's after. 

Don't know if that's in the rhelm of possibilities, but it seems like it'd be a cheaper LV than current BLock II if it were feasible.

Offline Downix

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Re: SLS "Swiss Army Launch System"?
« Reply #9 on: 02/08/2012 07:15 PM »
I think if there were only 3 RS25's, they can't drain a full core by disposal orbit, even at full thrust. 
If they use only three RS-25 engines, they can't launch a full core.  It would be too heavy at booster burnout.
Depends on how long the booster burn is.  If you're running the 120 seconds of the ATK SRB's, you'd be right.  If you're running the 200 seconds of the ULA derived LRB, now the 3-engine core is no longer too heavy at booster burnout, and would in fact outperform the 4-engine SRB design as a result.
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Offline Patchouli

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Re: SLS "Swiss Army Launch System"?
« Reply #10 on: 02/08/2012 10:12 PM »
I think if there were only 3 RS25's, they can't drain a full core by disposal orbit, even at full thrust. 
If they use only three RS-25 engines, they can't launch a full core.  It would be too heavy at booster burnout.
Depends on how long the booster burn is.  If you're running the 120 seconds of the ATK SRB's, you'd be right.  If you're running the 200 seconds of the ULA derived LRB, now the 3-engine core is no longer too heavy at booster burnout, and would in fact outperform the 4-engine SRB design as a result.

Makes for a good argument to restart those SLI engine projects like the RS-84 and TR-107 the Bush Administration so foolishly axed.

Offline woods170

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Re: SLS "Swiss Army Launch System"?
« Reply #11 on: 02/09/2012 06:41 AM »
I think if there were only 3 RS25's, they can't drain a full core by disposal orbit, even at full thrust. 
If they use only three RS-25 engines, they can't launch a full core.  It would be too heavy at booster burnout.
Depends on how long the booster burn is.  If you're running the 120 seconds of the ATK SRB's, you'd be right.  If you're running the 200 seconds of the ULA derived LRB, now the 3-engine core is no longer too heavy at booster burnout, and would in fact outperform the 4-engine SRB design as a result.

Makes for a good argument to restart those SLI engine projects like the RS-84 and TR-107 the Bush Administration so foolishly axed.
Hindsight is always 20/20
« Last Edit: 02/09/2012 06:41 AM by woods170 »

Offline baldusi

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Re: SLS "Swiss Army Launch System"?
« Reply #12 on: 02/09/2012 01:38 PM »
Makes for a good argument to restart those SLI engine projects like the RS-84 and TR-107 the Bush Administration so foolishly axed.
Hindsight is always 20/20
I think that rather than hindsight is one of strategy. Doing the evolution in decoupled programs is better than monolithic ones. On the other hand, the RS-84 and TR-107 where designed to be reusable, thus, very heavy and expensive for disposable use. A strategy of one reusable and one disposable engine would have covered the bases better. Yet, now most studies are leaning on methane for reusable vehicles.

Offline Lobo

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Re: SLS "Swiss Army Launch System"?
« Reply #13 on: 02/09/2012 04:59 PM »
Makes for a good argument to restart those SLI engine projects like the RS-84 and TR-107 the Bush Administration so foolishly axed.
Hindsight is always 20/20
I think that rather than hindsight is one of strategy. Doing the evolution in decoupled programs is better than monolithic ones. On the other hand, the RS-84 and TR-107 where designed to be reusable, thus, very heavy and expensive for disposable use. A strategy of one reusable and one disposable engine would have covered the bases better. Yet, now most studies are leaning on methane for reusable vehicles.

I think it's ok without the RS-84.  IF ULA were to bid and win the LRB contract, a slightly upgraded US built RD-180 should be able to hit 1 Mlb thrust, so 3 of them on a 5-5.5m AVP2 (or derived) LRB should do fine.  However, the availability of the RS-84 might have allowed ULA to keep using RD-180 on their commercial launches, and RS-84 on their LRB.  HOwever, use of RD-180 on both would have commonality, and then they can transition their commercial to US built RD-180 after their Russian stock is used up.  SO there could be a certain advantage of just one engine accross their whole kerolox line.

If SpaceX were to bid an win the LRB contract, they could then develop the M-2 engine, and use two of them on an 5.5 FX (or derived from FX) LRB should do fine.  I think they want to keep their engine development in-house anyway, so the RS-84 or TR-107 wouldn't have factored in anyway.

If Aerojet/Teledyne were to bid and win the LRB contract, they could use 6XAJ500 engines, and then a new 5-5.5m core.  (Not sure what it might have commonality with in the private sector, but maybe Orbital might have use for such a MLV.)  Aerojet would want to use their AJ engines anyway, so the RS-84 or TR-107 wouldn't have likely factored in there.
Although, they could work with ULA, to develop the 5-5.5m LRB which could use the AJ500 engines.  Then it could fly alone as a MLV with either AJ500 or RD180 engines for ULA's other customers.   ULA is not in the engine making business, so it might not matter much to them one way or the other if Aerojet can beat PWR on engine prices.

Offline spectre9

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Re: SLS "Swiss Army Launch System"?
« Reply #14 on: 02/10/2012 04:07 AM »
Seems like we will get to see all the booster competitors do a static firing as risk reduction as part of the milestones they will be given.

Really hope to get more info about who is competing soon.

Offline gin455res

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Re: SLS "Swiss Army Launch System"?
« Reply #15 on: 02/10/2012 07:32 AM »
Forgetting sunk costs, would there be any advantages to redesigning the system to use 4-6 smaller solid boosters (since the SLS is no longer restricted to having just two srbs to acommodate the orbiter)?

Is the ET design made simpler or more complicated by having two massive boosters, compared to other designs with srbs?

Offline edkyle99

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Re: SLS "Swiss Army Launch System"?
« Reply #16 on: 02/10/2012 02:44 PM »
Forgetting sunk costs, would there be any advantages to redesigning the system to use 4-6 smaller solid boosters (since the SLS is no longer restricted to having just two srbs to acommodate the orbiter)?

Is the ET design made simpler or more complicated by having two massive boosters, compared to other designs with srbs?

I'm sure others have mentioned this.  The core is designed to be "picked up" from the intertank section by the boosters.  As a result, the big LH2 tank is not designed to take the full booster propulsion loads.  That is why Block 1A SLS boosters have to be designed to apply their forces in the same manner as SRBs.  Multiple small strap-on boosters or multiple liquid boosters are not an option for these and other reasons.  Liquids are also limited to 5.5 meters diameter by VAB clearances, and the launch platforms, flame trench, and flame ducts limit where the boosters can be located, etc. 

Composite HTPB solids are going to be tough to beat.  A strong argument could be made that existing 5-segment steel case PBAN boosters could serve just fine for more than a few launches too.

 - Ed Kyle
« Last Edit: 02/10/2012 02:46 PM by edkyle99 »

Offline Lobo

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Re: SLS "Swiss Army Launch System"?
« Reply #17 on: 02/10/2012 04:30 PM »
Forgetting sunk costs, would there be any advantages to redesigning the system to use 4-6 smaller solid boosters (since the SLS is no longer restricted to having just two srbs to acommodate the orbiter)?

Is the ET design made simpler or more complicated by having two massive boosters, compared to other designs with srbs?

I'm sure others have mentioned this.  The core is designed to be "picked up" from the intertank section by the boosters.  As a result, the big LH2 tank is not designed to take the full booster propulsion loads.  That is why Block 1A SLS boosters have to be designed to apply their forces in the same manner as SRBs.  Multiple small strap-on boosters or multiple liquid boosters are not an option for these and other reasons.  Liquids are also limited to 5.5 meters diameter by VAB clearances, and the launch platforms, flame trench, and flame ducts limit where the boosters can be located, etc. 

Composite HTPB solids are going to be tough to beat.  A strong argument could be made that existing 5-segment steel case PBAN boosters could serve just fine for more than a few launches too.

 - Ed Kyle

First yes, that’s all as I’ve heard too.  So there’s really no option to put multiple solid boosters around the core, AJAX style.  Which is too bad, because in my opinion, the AJAX system, ET-like core with multiple attach points for using basically off-the-shelf commercial boosters, would have been the best on many fronts.  It’s too bad, but those are the cards that have been dealt.

So there will only be two boosters.  LRB options are either new boosters that are built to spec (3 million lbs thrust, 5.5m diameter max for the reasons Ed mention, lifting from the top like SRBs, able to support the weight of the core on the pad like the SRBs), or possibly a cluster of like 2 or 3 commercial boosters, mated to a special strongback, that is designed to take the weight of the core on the pad, and attach to the two SRB points, and lift from the top.  The smaller commercial CCB’s then attach to that, and would be more or less off-the-shelf boosters.  Taurus II, Atlas V, or F9.  Basically, a Taurus II-Heavy, Atlas V-Heavy, or Falcon Heavy, with the center core mated to a strongback, and the strongback attached to the core.  The outboard cores would lift on the central core as a typical 3-core heavy config would.
Or, as I said before, ULA, SpaceX, or Orbital designs a new 5 to 5.5m core LV, like FX or AVP2, but they design it to be the LRB for SLS, with that contract money. But they design it also so it can be a stand alone MLV.  It might be a different looking LV than some of their current concepts look like, but it’d be worth it for them to land that SLS contract.

I have no idea how competitive ATK’s advanced solid would be vs. LRB’s.  It might well be “tough to beat”.  But from a general engineer perspective, I’d think there’d be these considerations:

1)   A composite case SRB with new fuel will be a brand new Booster.  It’ll really share little with the STS 4-seg, or Ares 5-seg boosters.  I could see maybe the Ares 5-seg booster being tough to beat, because that’s mostly developed, and not much different than what ATK has been doing for 30 years.  But the advanced SRB would be a whole new animal, from scratch more or less.
2)   The Advanced SRB would really share nothing with anything else.  A clever commercial company like Aerojet or SpaceX could/should submit an LRB design with many shared components to commercial LV’s.  Including using the new LRB itself as a stand along MLV.  But beyond that, common engines and anything else they can make common with other LV’s.  Which would allow cost sharing with other programs, which could possible allow the commercial company to submit a lower bid, knowing they’ll have the advantage of that cost sharing.  What’s ATK going to share the SRB costs with?
3)   LRB’s also have a very clear safety advantage, as well as longer burn time/overall performance advantage.  They’d be wise to play that up hard in the bidding.  LRB’s can be shut down in a pad abort.  Shut down during launch abort, so the crew doesn’t have to worry about burning SRB’s.  They aren’t fueled until on the pad, just prior to launch.  And they aren’t transporting fueled segments clear across the country, or handling them in the VAB.

SO hopefully these things would give LRB’s a good edge over advanced SRB’s…hopefully…

Offline gin455res

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Re: SLS "Swiss Army Launch System"?
« Reply #18 on: 02/10/2012 05:58 PM »
So in summary, the core would have to be redesigned from scratch to take the thrust of 4-6 smaller solids from lower down, is that right?

Just out of curiosity, would this be a more complicated core design than the current design, or a simpler one (ignoring the complication of it's non-existence in comparison to the ET)?

 
Forgetting sunk costs, would there be any advantages to redesigning the system to use 4-6 smaller solid boosters (since the SLS is no longer restricted to having just two srbs to acommodate the orbiter)?

Is the ET design made simpler or more complicated by having two massive boosters, compared to other designs with srbs?

I'm sure others have mentioned this.  The core is designed to be "picked up" from the intertank section by the boosters.  As a result, the big LH2 tank is not designed to take the full booster propulsion loads.  That is why Block 1A SLS boosters have to be designed to apply their forces in the same manner as SRBs.  Multiple small strap-on boosters or multiple liquid boosters are not an option for these and other reasons.  Liquids are also limited to 5.5 meters diameter by VAB clearances, and the launch platforms, flame trench, and flame ducts limit where the boosters can be located, etc. 

Composite HTPB solids are going to be tough to beat.  A strong argument could be made that existing 5-segment steel case PBAN boosters could serve just fine for more than a few launches too.

 - Ed Kyle

Offline edkyle99

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Re: SLS "Swiss Army Launch System"?
« Reply #19 on: 02/10/2012 06:29 PM »
So in summary, the core would have to be redesigned from scratch to take the thrust of 4-6 smaller solids from lower down, is that right?

Just out of curiosity, would this be a more complicated core design than the current design, or a simpler one (ignoring the complication of it's non-existence in comparison to the ET)?

There would have to be attach fittings, and probably a thicker tank, and the launch pad would have to be re-designed extensively to support the core and to provide T-0 hold-downs, etc..  One complication would be in the engineering involved.  Another would involve the likely loss of performance due to the increased core stage dry mass.  A third would be the increased odds of vehicle failure created by the addition of ignition and separation events, etc.

I've long believed http://www.spacelaunchreport.com/blog016.html that a two-stage core-only approach would have worked just fine, using a few more core engines than currently planned, but that would have required accepting a lower maximum LEO performance from each launch.

 - Ed Kyle
« Last Edit: 02/10/2012 06:31 PM by edkyle99 »

Offline hydra9

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Re: SLS "Swiss Army Launch System"?
« Reply #20 on: 02/10/2012 06:35 PM »
I am a little confused about something.

The concept of the SLS is it will "evolve" to 130 mt.  But I thought I read somewhere it will be designed to be confiugred to each mission -- so the full size version for one mission, but the next time maybe the 70mt version will do.  Is the SLS designed so that like an EELV on steroids, that you use the specific configuration you want?  Or does it just get progressively more powerful and not go back?  Because the modular, "swiss army knife" version is the more interesting idea.


SLS configurations will of course be extremely limited until the development of the expendable RS-25E engines and the upper stage are completed in the 2020s. 

Boeing has already conceived configurations that utilize only the 8.4 meter booster without SRBs plus the MPCV Service Module to lift about 20 tonnes into LEO. They use 4 RS-68 engines for the booster but 5 or 6 SSME should be able to provide  similar to superior performance.

And concepts that use up to 4 SRBs to increase payload for a shuttle derived rocket have been around since the 1970s. 

Marcel F. Williams

Offline edkyle99

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Re: SLS "Swiss Army Launch System"?
« Reply #21 on: 02/10/2012 07:37 PM »
Boeing has already conceived configurations that utilize only the 8.4 meter booster without SRBs plus the MPCV Service Module to lift about 20 tonnes into LEO. They use 4 RS-68 engines for the booster but 5 or 6 SSME should be able to provide  similar to superior performance.

Boeing's concepts were limited in that they used no upper stage, or a very small upper stage, and used the bigger core that would be less than optimum for such a mission.

By comparison, an optimized two-stage rocket using five RS-25E engines on the first stage and one J-2X on the second stage should be able to lift nearly 50 tonnes to LEO.  This first stage would only be 55% as tall as the SLS core.  The second stage would carry a little less propellant than the planned Ares I Upper Stage.

Generally speaking, six RS-25E engines (combined with a dual J-2X upper stage) would lift 60 tonnes.  Seven RS-25E engines would get 70 tonnes (this would be a rocket that would still need to be loaded, both stages total, with less propellant than just the SLS core).  More than one person in the space business believes that 70 tonnes is enough for an affordable exploration architecture.

 - Ed Kyle
« Last Edit: 02/10/2012 07:41 PM by edkyle99 »

Offline Jim

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Re: SLS "Swiss Army Launch System"?
« Reply #22 on: 02/10/2012 07:44 PM »

Boeing has already conceived configurations that utilize only the 8.4 meter booster without SRBs plus the MPCV Service Module to lift about 20 tonnes into LEO.

That is not SLS and NASA is not building it

Nor can the MPCV Service Module fly alone.
« Last Edit: 02/10/2012 07:47 PM by Jim »

Offline baldusi

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Re: SLS "Swiss Army Launch System"?
« Reply #23 on: 02/10/2012 07:45 PM »
Generally speaking, six RS-25E engines (combined with a dual J-2X upper stage) would lift 60 tonnes.  Seven RS-25E engines would get 70 tonnes (this would be a rocket that would still need to be loaded, both stages total, with less propellant than just the SLS core).  More than one person in the space business believes that 70 tonnes is enough for an affordable exploration architecture.
And that was not what the law asked. NASA did the design they felt was less risky to comply with the law. There were thumbs in the scale, particularly with how they interpreted the law. But if you believe in DRM 5.0 what they did was very logical.

Offline hydra9

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Re: SLS "Swiss Army Launch System"?
« Reply #24 on: 02/12/2012 06:51 PM »
Boeing has already conceived configurations that utilize only the 8.4 meter booster without SRBs plus the MPCV Service Module to lift about 20 tonnes into LEO. They use 4 RS-68 engines for the booster but 5 or 6 SSME should be able to provide  similar to superior performance.

Boeing's concepts were limited in that they used no upper stage, or a very small upper stage, and used the bigger core that would be less than optimum for such a mission.

By comparison, an optimized two-stage rocket using five RS-25E engines on the first stage and one J-2X on the second stage should be able to lift nearly 50 tonnes to LEO.  This first stage would only be 55% as tall as the SLS core.  The second stage would carry a little less propellant than the planned Ares I Upper Stage.

Generally speaking, six RS-25E engines (combined with a dual J-2X upper stage) would lift 60 tonnes.  Seven RS-25E engines would get 70 tonnes (this would be a rocket that would still need to be loaded, both stages total, with less propellant than just the SLS core).  More than one person in the space business believes that 70 tonnes is enough for an affordable exploration architecture.

 - Ed Kyle

Ed, I'm a big fan of your liquid shuttle derived configurations. Your concepts are extremely interesting and very logical, IMO!

But practical shuttle derived rocket architectures were probably doomed in 2007,  once Griffin committed NASA to develop  5-segment SRBs, in order to enhance the lifting ability of the Ares I.  And this is especially true now after all of the billions already spent on the 5-segment SRBs.  IMO, nothing has screwed up NASA more than Griffin's decision to develop the Ares I.

But I still think liquid shuttle derived architectures, without side-mounted boosters,  will prevail in the long run-- at least for manned vehicles launched to LEO, the Lagrange points, and to  lunar orbit in order to reduce recurring cost. They'll just use the stretched core  and will be able to lift a lot more payload than more practical and  more directly shuttle derived LOX/LH2 concepts. 

Marcel F. Williams


 


Offline spectre9

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Re: SLS "Swiss Army Launch System"?
« Reply #25 on: 02/12/2012 10:04 PM »
ESAS recommended the Ares 1.

In 4 seg version.

For such a big report they really do work hard to ignore it and do what they wanted.

Seems like AVH would've been a much better option but concerns over the RD-180 stopped that.

So why not the DIVH? Too expensive compared to a rocket that didn't exist yet?

Seems like a strange conclusion to me.

Now it seems NASA is so scared they will create a rocket that can't lift Orion they just don't want to even think about having a separate CLV.

Offline edkyle99

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Re: SLS "Swiss Army Launch System"?
« Reply #26 on: 02/13/2012 12:48 AM »
Ed, I'm a big fan of your liquid shuttle derived configurations. Your concepts are extremely interesting and very logical, IMO!

But practical shuttle derived rocket architectures were probably doomed in 2007,  once Griffin committed NASA to develop  5-segment SRBs, in order to enhance the lifting ability of the Ares I.  And this is especially true now after all of the billions already spent on the 5-segment SRBs.  IMO, nothing has screwed up NASA more than Griffin's decision to develop the Ares I.
Ares I went to five segment booster not to increase performance but to save money.  Five segment booster and J-2X were needed for Ares V.  Switching to them for Ares I (from four segment and air-start SSME) avoided the cost of developing those one-off propulsion systems.  In an underfunded program, Griffin had little choice but to switch.  It was a sound engineering manager choice that would have worked just fine, but it drove the schedule backward and development costs forward - a political no-no once anti-Constellation Obama won the Presidency. 

The real problem, entirely in retrospect, was the basic ESAS 1.5 launch architecture, regardless of the rocket design details.  It meant two costly launch vehicle development programs rather than just one.  (Never-mind that NASA is currently funding three new launch vehicle developments (SLS, Falcon 9, Antares) and the modification of a fourth (Delta 4 for Orion Test Flights) rather than "just two".)
Quote
But I still think liquid shuttle derived architectures, without side-mounted boosters,  will prevail in the long run-- at least for manned vehicles launched to LEO, the Lagrange points, and to  lunar orbit in order to reduce recurring cost. They'll just use the stretched core  and will be able to lift a lot more payload than more practical and  more directly shuttle derived LOX/LH2 concepts. 

Marcel F. Williams

As much as I prefer the concept, I don't see a core-only approach happening unless SLS is cancelled, which would be a disaster for NASA all around. 

 - Ed Kyle
« Last Edit: 02/13/2012 12:50 AM by edkyle99 »

Offline QuantumG

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Re: SLS "Swiss Army Launch System"?
« Reply #27 on: 02/13/2012 12:53 AM »
Ares I went to five segment booster not to increase performance but to save money.  Five segment booster and J-2X were needed for Ares V.  Switching to them for Ares I (from four segment and air-start SSME) avoided the cost of developing those one-off propulsion systems.

Wow, that's the first time I've heard that. I was under the impression that they switched from an air-start SSME because it didn't exist and was infeasible to boot. The requirement for the 5-seg solid followed from the decrease in performance. All this happened a while ago, are there any references available to back up this version of history?
I hear those things are awfully loud. It glides as softly as a cloud. What's it called? Monowhale!

Offline spectre9

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Re: SLS "Swiss Army Launch System"?
« Reply #28 on: 02/13/2012 04:43 AM »
But by doing that they found themselves with a vehicle not recommended by ESAS.

Either do another report or stick with what it concluded.

What's the point in having these studies if you can just go.... well we can save some cash by not building the air start SSME....

That should be part of the study.

Offline 93143

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Re: SLS "Swiss Army Launch System"?
« Reply #29 on: 02/13/2012 06:35 AM »
I was under the impression that they switched from an air-start SSME because it didn't exist and was infeasible to boot.

I don't think it was infeasible; as I recall it was difficult but possible to do an air-start SSME.  What was not possible was a restartable SSME - or rather, it would have been basically a new engine.  So the Ares V EDS couldn't use the RS-25, and the whole show collapsed from there, whatever the actual chain of reasoning...

Offline woods170

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Re: SLS "Swiss Army Launch System"?
« Reply #30 on: 02/13/2012 06:50 AM »
Right people... since when has this thread become a Constellation history lesson?  :-[

Offline spectre9

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Re: SLS "Swiss Army Launch System"?
« Reply #31 on: 02/15/2012 08:22 AM »
I think the point of that little sidetrack was to determine whether NASA needs a separate crew launch vehicle for Orion MPCV.

NASA wants to launch it all up with an Earth departure stage to minimise risk.

What configuration of the SLS will be most effective for this?

Will the ICPS become a stock part for crew launching?

Where does J2-X fit into all this?

Offline woods170

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Re: SLS "Swiss Army Launch System"?
« Reply #32 on: 02/15/2012 09:11 AM »
I think the point of that little sidetrack was to determine whether NASA needs a separate crew launch vehicle for Orion MPCV.

1. NASA wants to launch it all up with an Earth departure stage to minimise risk.

2. What configuration of the SLS will be most effective for this?

3. Will the ICPS become a stock part for crew launching?

4. Where does J2-X fit into all this?
1. Correct. That's how SLS was presented last year. Ongoing trades have not (officially) changed this

2. Depends on what you wanna send out to BEO. Is it just Orion? Or Orion and some other 'thingie'? (such as a lunar lander or deep space habitat).

3. ICPS is currently planned for use on the first two manned SLS missions only (with no upper stage) But, the roadmap for missions is still being worked on. This could change. For versions of SLS with an upper stage (regardless of manned or unmanned) the planned earth departure stage is CPS (not the interim version).

4. J-2X is planned for upper stage use. Engine for the CPS (not the interim version) is subject to trades.

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