Author Topic: SLS trades lean towards opening with four RS-25s on the core stage  (Read 143056 times)

Offline Chris Bergin

http://www.nasaspaceflight.com/2011/10/sls-trades-opening-four-rs-25s-core-stage/

At least two more articles to come on SLS hardware. Starting to feel like the "good old days" of shuttle processing level of content to write up in L2.
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Offline alexw

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http://www.nasaspaceflight.com/2011/10/sls-trades-opening-four-rs-25s-core-stage/
At least two more articles to come on SLS hardware. Starting to feel like the "good old days" of shuttle processing level of content to write up in L2.

   Are they planning *two* complete new NASA-only upper stages?
    1) the "CPS", "NASA designed on-orbit stage... Enables Exploration missions", to be used for Block 1A+
    2) the "Upper Stage", with 3 * J-2X, "This Upper Stage burns out prior to orbit insertion (ala Saturn V)."

    plus, additionally,
    0) "iCPS", the DIVHUS with new avionics, "Requires Delta IV flight computer redesign."

                ?
              -Alex

Offline Chris Bergin

Noting they are trading (I feel like I have to keep saying that) the Block II shown on the presentation has a 3xJ-2X Upper Stage, with the CPS on orbit stage on top inside the fairing.
« Last Edit: 10/05/2011 04:41 am by Chris Bergin »
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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?

How much clearance will there be between the top of the Block II and the ceiling of the VAB?
« Last Edit: 10/05/2011 04:50 am by Jason1701 »

Offline Chris Bergin

Direct had lots of configs, including four segs, if memory serves :)
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Offline alexw

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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?

Quote
How much clearance will there be between the top of the Block II and the ceiling of the VAB?
     Good question. And by how much will the stretched core stage clear the MAF doors?
          -Alex

Offline aquanaut99

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Noting they are trading (I feel like I have to keep saying that) the Block II shown on the presentation has a 3xJ-2X Upper Stage, with the CPS on orbit stage on top inside the fairing.

So the full-up SLS-Block II is actually a 3 stage rocket plus boosters? Am I reading this right?

Offline Jamie Young

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Core with boosters. Second Stage (Upper Stage) and EDS, right?

Offline FinalFrontier

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Those liquids sure look like Atlas V CCBs ;)  ;)  ;)
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Offline sdsds

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Would it be OK to call it "LV 27"?

http://www.nasa.gov/pdf/140637main_ESAS_06.pdf
Page 420 (60 of 150 in the pdf).

Wait, that can't be right.  That was the plan back in November of 2005....
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Offline Tez

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Quote
     Good question. And by how much will the stretched core stage clear the MAF doors?
          -Alex

About 11ft, taking door height as 122m (400ft) and block 2 as 389ft.
« Last Edit: 10/05/2011 07:49 am by Tez »
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Offline MP99

Noting they are trading (I feel like I have to keep saying that) the Block II shown on the presentation has a 3xJ-2X Upper Stage, with the CPS on orbit stage on top inside the fairing.

Broken record, but I still wonder how this really meets the requirements of PL 111-267:-

Quote
(1) IN GENERAL.—The Space Launch System developed pursuant to subsection (b) shall be designed to have, at a minimum, the following:

(A) The initial capability of the core elements, without an upper stage, of lifting payloads weighing between 70 tons and 100 tons into low-Earth orbit...

(B) The capability to carry an integrated upper Earth departure stage bringing the total lift capability of the Space Launch System to 130 tons or more.

...given that the upper & EDS functions are separated into two different stages rather than integrated.

cheers, Martin

Offline uko

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Great article Chris, thanks!

I wonder what will the crew configuration look like after Block 1?
What kind of upper stage will it have?
In theory, there's no difference between theory and practice, but in practice, there is !

Offline MP99

Noting they are trading (I feel like I have to keep saying that) the Block II shown on the presentation has a 3xJ-2X Upper Stage, with the CPS on orbit stage on top inside the fairing.

So the full-up SLS-Block II is actually a 3 stage rocket plus boosters? Am I reading this right?

Given CPS doesn't burn during ascent, I don't believe it's a true third stage. That makes SLS a LEO-only vehicle, but CPS can be optimised for longer loiter. For instance, refer Mars DRA 5 for CPS's heritage as a modified AVUS (but using RL-10s instead of J-2X in order to provide the required Isp).

Given also that Block 2's upper stage is disposed of sub-orbitally, the upper stage won't require a restart. ISTM using 2x air-start RS-25 instead of 3x J-2X would be quite suitable in this application, and would increase commonality between core and upper stage (refer HEFT2.pdf).

cheers, Martin

Offline Ben the Space Brit

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Noting they are trading (I feel like I have to keep saying that) the Block II shown on the presentation has a 3xJ-2X Upper Stage, with the CPS on orbit stage on top inside the fairing.

That's what I call the SLS-SH configuration (the 3 x SSME being the SLS-M, the 4 x SSME being the SLS-H).  That's pretty much intended to be a one-launch lunar cargo version, much like how Ares-V was intended to be towards the end of the CxP era.

Given CPS doesn't burn during ascent, I don't believe it's a true third stage. That makes SLS a LEO-only vehicle, but CPS can be optimised for longer loiter. For instance, refer Mars DRA 5 for CPS's heritage as a modified AVUS (but using RL-10s instead of J-2X in order to provide the required Isp).

I've suspected for a while that talking about SLS's BEO performance was a red herring.  The type is an LEO cargo launcher - Only its' payload will perform escape burns, not any part of the launch vehicle itself.

That said, I wonder if it is possible for CPS to act as a third stage.  That might push up the payload throw if required.  I'm sure there is a 'sweet spot' balance that allows CPS to be used on ascent but still allows optimum escape burn performance.

Just out of interest, has there been even the slightest hypothetical discussion of using J-2XD instead of RL-10 on CPS? That would increase commonality across both SLS and BEO spacecraft applications.

I wonder what will the crew configuration look like after Block 1?
What kind of upper stage will it have?

It won't need one.  Indeed, the SLS-CLV will probably have a ballast drum in place of the DIVUS in the faux-Apollo PLF just so the crew won't be pulped by the g-loadings from launching a < 30t crew vehicle on a 100t IMLEO launcher.



[edit]
Added reply to Uko
« Last Edit: 10/05/2011 09:18 am by Ben the Space Brit »
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Offline mike robel

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Good article Chris.  Most imformative.

Offline Mark S

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Noting they are trading (I feel like I have to keep saying that) the Block II shown on the presentation has a 3xJ-2X Upper Stage, with the CPS on orbit stage on top inside the fairing.

Broken record, but I still wonder how this really meets the requirements of PL 111-267:-

Quote
(1) IN GENERAL.—The Space Launch System developed pursuant to subsection (b) shall be designed to have, at a minimum, the following:

(A) The initial capability of the core elements, without an upper stage, of lifting payloads weighing between 70 tons and 100 tons into low-Earth orbit...

(B) The capability to carry an integrated upper Earth departure stage bringing the total lift capability of the Space Launch System to 130 tons or more.

...given that the upper & EDS functions are separated into two different stages rather than integrated.

cheers, Martin

Yes, I have been asking the same question for a while now, and get nothing back but stony silence.

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.

Sorry, this just looks like the same old MSFC gigantism fetish all over again. And a lot of responsibility for that lies with the Senate and House, who both had plenty of opportunities to clarify that "tons" in the law's language refers to short tons (2000 lbs), not metric tonnes. And that "total lift capability" means IMLEO, not usable payload capacity. Those two ambiguities in the law gave the gigantists the wiggle room they needed to turn a reasonable J-130/J-241H back into Ares-V (ESAS LV-27).

Unless this approach is reversed, I don't see how SLS will be able to fit within the given budget. Sigh.

Offline Ben the Space Brit

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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.


[edit]
Corrected typos
« Last Edit: 10/05/2011 01:08 pm by Ben the Space Brit »
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Offline aquanaut99

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Unless this approach is reversed, I don't see how SLS will be able to fit within the given budget. Sigh.

Simple, by deferring Block II to never-never land. After all, the law only requires the rocket to be upgradable to 130 mT, not the 130 mT version actually flying, no? I thought only the 70 mT (Block I) has a law-mandated deadline?

We could already do plenty with Block I SLS alone. And Block IA with a good CPS could cover virtually all our HSF needs for the next 30 years at least, since I can't see any manned Mars mission (which would require Block II) before that time-frame anyway.
« Last Edit: 10/05/2011 01:10 pm by aquanaut99 »

Offline demorcef

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Fantastic article Chris!  Another stellar piece of journalism from you.  It really makes me feel good to see real progress being made.  I hope the funding keeps up with the designs this time.  There might actually be light at the end of the sad tunnel we have been stuck in these past few years.

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