Author Topic: SLS trades lean towards opening with four RS-25s on the core stage  (Read 94172 times)

Online Robotbeat

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This is just a great disappointment. There are no missions of any substance in the planning: flying by and waving at the Moon is not a real mission. It is 51 years after the Apollo 8 mission proving that we cannot match that mission's abilities.

It's been noted more times than I can remember that the mission planning is in work, via Mr Shannon :)
It shows where the real priorities are when the actual mission planning (and hardware, etc) is practically an afterthought compared to the launch vehicle.

Where were your mission plans (and hardware, etc) for anything without SLS?  They had years.
Your question is off-topic, but one example:
http://www.nasaspaceflight.com/2009/09/ula-claim-gap-reducing-solution-via-eelv-exploration-master-plan/
Another:
http://ti.arc.nasa.gov/m/project/neo/pdf/neo_crewed_mission.pdf
« Last Edit: 10/06/2011 12:04 AM by Robotbeat »
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Online Robotbeat

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Good question, Chile. We did ask Mr Shannon for an interview (main angle reflecting on Shuttle), but he refused....

....well PAO said he did, which is probably more to do with them than anything.
Well, I'd certainly be interested in an interview, especially if it focused on the mission studies!
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Mr. Justice

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It is an eternal wait.

It hasn't even been a month.  Give him some time.

No, it has been 20 months since the cancellation of Constellation. Constellation had a mission. It's downfall was Ares. Had we simply modified Ares, in conjunction with commercial crew for LEO, into something more like Jupiter we would be set to return to the Moon. Jupiter could have supplied fuel to eventual depots for NEO missions and then Mars.

Offline 93143

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I know all that.  The problem is that now that we're finally moving forward, and we've actually got people assigned to mission design, you almost instantly claim that it's taking forever.  You're ignoring actual facts and recent events in favour of averaging over the last couple of years.

It reminds me of the people who were complaining that ISS research hadn't changed the world, and that therefore the whole thing was a waste of money, about five minutes after we finished building the thing...
« Last Edit: 10/05/2011 11:25 PM by 93143 »

Offline Jason1701

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the automatic need for the core to be “stretched” – based on the five segment boosters on the configuration
Didn't DIRECT have some configurations that were Heavy (meaning 5-seg) but not Stretched?
      Yes, and the SRB would have attached at the second-segment from the top rather than the first, IIRC, as Shuttle had proposed had it gone to 5-segs. Chris, by use of the word "need" above, do your sources suggest that this config by DIRECT & SSP was judged technically infeasible?

Can any DIRECT people clarify this?

Offline Pheogh

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the automatic need for the core to be “stretched” – based on the five segment boosters on the configuration
Didn't DIRECT have some configurations that were Heavy (meaning 5-seg) but not Stretched?
      Yes, and the SRB would have attached at the second-segment from the top rather than the first, IIRC, as Shuttle had proposed had it gone to 5-segs. Chris, by use of the word "need" above, do your sources suggest that this config by DIRECT & SSP was judged technically infeasible?

Can any DIRECT people clarify this?

I don't believe it has anything to do with technical feasibility. Ultimately what we are seeing is the influence of ATK having a cascading affect. DIRECT ultimately arrived at a 4 engine max config meaning standard ET volumes were adequate, meaning a stretch was not necessary and neither was 5 seg. DIRECT was always optimized for cost, starting from the 5/5 baseline you have already canceled out this optimization. The tail is wagging the dog and that is never a good position to be trading from IMHO.

Offline Downix

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the automatic need for the core to be “stretched” – based on the five segment boosters on the configuration
Didn't DIRECT have some configurations that were Heavy (meaning 5-seg) but not Stretched?
      Yes, and the SRB would have attached at the second-segment from the top rather than the first, IIRC, as Shuttle had proposed had it gone to 5-segs. Chris, by use of the word "need" above, do your sources suggest that this config by DIRECT & SSP was judged technically infeasible?

Can any DIRECT people clarify this?

I don't believe it has anything to do with technical feasibility. Ultimately what we are seeing is the influence of ATK having a cascading affect. DIRECT ultimately arrived at a 4 engine max config meaning standard ET volumes were adequate, meaning a stretch was not necessary and neither was 5 seg. DIRECT was always optimized for cost, starting from the 5/5 baseline you have already canceled out this optimization. The tail is wagging the dog and that is never a good position to be trading from IMHO.
Even with the 5-segment, the core stretch is not necessary.  You can either lift from the bottom, or you can make the attachment point above the LOX dome at the top of the core.  Either option allows you to have a much lighter core structure.
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Offline sdsds

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Even with the 5-segment, the core stretch is not necessary.  You can either lift from the bottom, or you can make the attachment point above the LOX dome at the top of the core.  Either option allows you to have a much lighter core structure.

You're sure the thrust oscillations from the solids can be transferred down into (and thus dampened by) the mass of the LOX?  Is there some obvious structural mechanics proof of this?
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Offline Downix

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Even with the 5-segment, the core stretch is not necessary.  You can either lift from the bottom, or you can make the attachment point above the LOX dome at the top of the core.  Either option allows you to have a much lighter core structure.

You're sure the thrust oscillations from the solids can be transferred down into (and thus dampened by) the mass of the LOX?  Is there some obvious structural mechanics proof of this?
It was a solution studied back in the late 80's, but I have no idea if they had worked on any solutions to the TO.
chuck - Toilet paper has no real value? Try living with 5 other adults for 6 months in a can with no toilet paper. Man oh man. Toilet paper would be worth it's weight in gold!

Offline Herb Schaltegger

You're sure the thrust oscillations from the solids can be transferred down into (and thus dampened by) the mass of the LOX?  Is there some obvious structural mechanics proof of this?

To a first approximation, the whole thing is just a spring-mass system.  However, the ever-shrinking mass of the core stage complicates things.  Find yourself an engineering grad student and have them figure it out.  Shouldn't take them very long.
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Offline Namechange User

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This is just a great disappointment. There are no missions of any substance in the planning: flying by and waving at the Moon is not a real mission. It is 51 years after the Apollo 8 mission proving that we cannot match that mission's abilities.

It's been noted more times than I can remember that the mission planning is in work, via Mr Shannon :)
It shows where the real priorities are when the actual mission planning (and hardware, etc) is practically an afterthought compared to the launch vehicle.

Where were your mission plans (and hardware, etc) for anything without SLS?  They had years.
Your question is off-topic, but one example:
http://www.nasaspaceflight.com/2009/09/ula-claim-gap-reducing-solution-via-eelv-exploration-master-plan/
Another:
http://ti.arc.nasa.gov/m/project/neo/pdf/neo_crewed_mission.pdf

Strange that it would be "off-topic" when it was a direct response to something you decided to bring up. 

But I'll address your examples rather easily.  Those are papers.  One of which is by a company and it is fairly common practice for companies to produce such white papers to show what capabilities they have or could provide for NASA.  They are marketing tactics mostly to help inform the agency. 

In other words those are a far cry from policy and a plan that NASA adopts formally.  That is what has been missing and that is the hole in your argument that is the size of SLS. 
Enjoying viewing the forum a little better now by filtering certain users.

Offline RyanC

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The first escalations occur....soon my pretties, soon we will have ARES V again...

Offline Khadgars

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Designating the launch vehicle requirements (for a new launch vehicle) before having the mission scope/policy/plan/blah done is bass-ackwards. That I pointed that out is not off-topic; your asking for mission plans for anything without SLS was off-topic.

"Hey guys, I'm going to go order curtains from the store, then I'll measure my windows!"

EDIT:I mean, don't get me wrong, I'm glad we're finally measuring the windows, even if we ordered the curtains already.


The STS had no specific mission really until ISS and it flew for 30 years.  Are not all missions designed around the launch vehicles and not the other way around (Apollo era aside)?

Edit: Meant STS not SLS
« Last Edit: 10/06/2011 05:56 AM by Khadgars »

Offline aquanaut99

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Designating the launch vehicle requirements (for a new launch vehicle) before having the mission scope/policy/plan/blah done is bass-ackwards. That I pointed that out is not off-topic; your asking for mission plans for anything without SLS was off-topic.

"Hey guys, I'm going to go order curtains from the store, then I'll measure my windows!"

EDIT:I mean, don't get me wrong, I'm glad we're finally measuring the windows, even if we ordered the curtains already.


The SLS had no specific mission really until ISS and it flew for 30 years.  Are not all missions designed around the launch vehicles and not the other way around (Apollo era aside)?

You mean STS...

Offline Khadgars

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You mean STS...

Indeed I did, sorry about that ;p

Offline MP99

How does a separate CPS fit in the PL 111-267? It is nowhere to be found, and the SLS therein requires "an integrated upper Earth departure stage", not a dedicated second stage and a dedicated in-space stage. Especially when the funds for CPS are to be taken from the SLS budget, and when CPS is being set up as a completely separate project from SLS. Sounds like illegal diversion of funds to me.

I think that this is a case where "Practicable" rears its head.  Given that J-2X is ETO-optimised it may not be possible to abide by that clause of the Act.  As matters go, I don't think that this is a serious issue and it actually makes SLS more flexible as you optimise the upper stage for IMLEO performance and have an BLEO-optimised propulsion module if needed.

Just a thought: Delete the SLS upper stage, attach the CPS directly to the four-engine core and this should be sufficient for orbital missions to LLO or the EML points.  This isn't a capability that is currently required but so little of SLS utilisation is set in stone right now that it might emerge eventually.



Look at it from the other direction - what non-LEO missions can you fly with block 2, and what does it need from the launcher?

1) Single three-stage launch with direct insertion to TLI. Think CxP cargo mission on Ares V launcher, etc. Used for:-

1a) LSR Lunar cargo delivery direct to surface (CxP cargo).

1a) LOR Lunar mission.

1b) EMLR assembly of Lunar or BEO mission.



2) Dual launch EOR TLI with monster CPS on one launch and payload on another. Think DIRECT phase 2.

2a) DIRECT-type Lunar mission.

2b) Delivery of huge mission element for EMLR assembly for BEO mission.



3) Multiple launch EOR.

3a) Mars DRA 5 style assembly of multiple payloads in LEO.




ISTM that SLS is designed for assembly of big missions in LEO (like Mars DRA 5) and/or injecting with SEP instead of chemical (implying HEO or EML rendezvous of crew with the mission stack). But look at the high boiloff & station-keeping requirements of DRM 5.

PL 111-267's "integrated" launcher is more optimised for Lunar and EML-assembled missions. It would make more sense to me if NASA optimised SLS as two-stage 60-ish-mT-through-TLI, since HEFT ended up assembling most of it's missions at EML. Then CPS can be truly "in-space optimised", ie hopefully it can avoid the high boiloff of DRM 5 without the high dry mass penalty of HEFT's CPS, which I suspect is driven by the LEO thermal environment.

cheers, Martin

Offline woods170

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The first escalations occur....soon my pretties, soon we will have ARES V again...

Interesting remark. What makes you think so?

Offline aquanaut99

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The first escalations occur....soon my pretties, soon we will have ARES V again...

If anything, we will have Ares V classic again. Which wasn't such a bad design if taken as a stand-alone heavy lifter. What really did CxP in was insisting to design Ares I in parallel, a booster that merely duplicated EELV performance while being much more expensive. And that finally underperformed so much that Ares V had to be scaled up again and again to compensate.

Remember, monster Ares V rocketzilla was supposed to lift something like 180 tons. We're still a far cry from that.

Also, SLS might never make it to Phase II. In fact, I fully expect that Phase IA (maybe with some slight further upgrades down the line) will end up being the final production version of SLS (with Phase II being the eternal "future upgrade option for once we have the money", designed mainly to satisfy the letter of the law but never actually built).

Such a Phase IA SLS will be at around (standard) Energia-level performance with regards to LEO. Not bad at all, and proably sustainable for NASA (about as much as Shuttle was sustainable...), at least IMO. And it is fully BEO capable with an appropriate CPS.

PS: "Sustainable" for a NASA on current budget. Ofc, if the budget is axed 20% or more, then that's a different story...
« Last Edit: 10/06/2011 12:42 PM by aquanaut99 »

Offline Alexa431

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With this approximate timeline and the blocks, is it safe to assume that NASA is planning to use the SLS for around 30 years or longer??

Offline Ben the Space Brit

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With this approximate timeline and the blocks, is it safe to assume that NASA is planning to use the SLS for around 30 years or longer??

That's a big unknown.  After all, a breakthrough could come tomorrow that could render conventional rocketry as obsolete a technology as the horse-drawn carriage. ;)

Still, the invention of anti-gravity aside, the fact that President Obama talked about missions in the mid-2030s, then we're probably looking at a program with a 25-year timeline even if individual vehicles aren't used for the entire duration.
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