Author Topic: Upper Stage for SLS  (Read 15667 times)

Offline Proponent

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Upper Stage for SLS
« on: 10/07/2010 05:05 AM »
[This is intended to be the continuation of a discussion that has been quite rightly booted out of an L2 forum for being OT.]

The Senate's FY2011 authorization bill specifies that SLS is to be flown into earth orbit by 2016.  It also specifies that an upper stage, enabling SLS to go beyond earth orbit, is to be developed but sets no timetable.  This wishiwashiness about building a beyond-earth-orbit-capable vehicle leaves me concerned about the following scenario.  Circa 2016, SLS does indeed fly to LEO.  The necessary trio of presidential will, Congressional sentiment and economic reality, however, fails to coalesce behind building an upper stage anytime soon.  Key SLS constituencies being well served by SLS's existence, regardless of whether it flies much or ever leaves LEO, SLS languishes without an upper stage for years, all the while consuming limited funds.  If this goes on too long, SLS's lack of accomplishment may ultimately even catch up with its political benefits, the result being termination.

That's my nightmare.  I'd be less worried if the Senate bill at least specified a date for an upper stage.  That not being the case, I'll be a happier space cadet if someone can convince me that my fears are unjustified.
« Last Edit: 10/07/2010 05:08 AM by Proponent »

Offline pathfinder_01

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Re: Upper Stage for SLS
« Reply #1 on: 10/07/2010 05:10 AM »
No date for an upper stage to my knowlege or specifications. 70 tons to LEO is useless. 30 tons to l1/l2 or the moon is another story.  All SLS needs to do is lift Orion, be able to lift 70 tons to LEO without upper stage, and be able to grow to 130 tons with upper stage.

Hopefully someone at NASA will straighten this out. It is part of the reason I am so anti SLS.

Online MickQ

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Re: Upper Stage for SLS
« Reply #2 on: 10/07/2010 05:48 AM »
Would the safest path be for NASA to concentrate solely on the LEO vehicle but make it able to accept a comercially available upper stage for the BEO role eg. ACES 41/71/181 as the mission requires ???  I mean, does the legislation actually direct NASA to develop the upper stage or just to be able to use one to go BEO ???

Mick.

Offline pathfinder_01

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Re: Upper Stage for SLS
« Reply #3 on: 10/07/2010 05:59 AM »
Would the safest path be for NASA to concentrate solely on the LEO vehicle but make it able to accept a comercially available upper stage for the BEO role eg. ACES 41/71/181 as the mission requires ???  I mean, does the legislation actually direct NASA to develop the upper stage or just to be able to use one to go BEO ???

Mick.

The problem with the commercial route is I don't think any are available. ACES if I recall correctly wanted NASA to pay for it. ULA would then use ACES on all its boosters. The ACES 70 would fit in well with SLS, but not sure NASA has the funds and the clout to kick money over to that route.

Offline sdsds

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Re: Upper Stage for SLS
« Reply #4 on: 10/07/2010 06:14 AM »
does the legislation actually direct NASA to develop the upper stage or just to be able to use one to go BEO ???

SLS must have "the capability to carry" an upper stage that would bring its LEO capability to 130 t. [302(c)(1)(B)].

In meeting that requirement NASA must "to the extent practicable" extend or modify existing contracts. [302(b)(2)]  So for example there is an existing contract with PWR to develop J-2X, an upper stage engine.

The act does not seem to preclude NASA from also using other upper stages on SLS, an approach that might make sense if early missions do not require the full capability described in 302(c)(1)(B).
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Offline Downix

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Re: Upper Stage for SLS
« Reply #5 on: 10/07/2010 06:19 AM »
Would the safest path be for NASA to concentrate solely on the LEO vehicle but make it able to accept a comercially available upper stage for the BEO role eg. ACES 41/71/181 as the mission requires ???  I mean, does the legislation actually direct NASA to develop the upper stage or just to be able to use one to go BEO ???

Mick.

The problem with the commercial route is I don't think any are available. ACES if I recall correctly wanted NASA to pay for it. ULA would then use ACES on all its boosters. The ACES 70 would fit in well with SLS, but not sure NASA has the funds and the clout to kick money over to that route.
You mean, you don't think any are available, other than the upper stages we are already using, aka Delta IV US, and Centaur, correct?

I'd already done the math, it is more than possible to fit 3 Centaur under the Jupiters shroud, as either a mate-up upper stage, or to enable multiple payloads.  As SLS is similar to Jupiter, it would go without saying that, yes, we do have upper stages available, just not optimized ones.  (Heck, even a single DIVUS makes moon operations possible)
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Offline Ben the Space Brit

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Re: Upper Stage for SLS
« Reply #6 on: 10/07/2010 07:30 AM »
The only significant BEO time-line that exists presently (AFAIK) is President Obama's proposal that BEO pathfinder missions begin in the early 2020s with the first NEO encounter in 2025 and the Phobos encounter/Mars orbiter in 2030 with a human landing on Mars "soon thereafter".  IMO, that means that the upper stage needs to get to hardware testing in space really no later than 2018/19.

There are basically three options for the upper stage right now:

* 5.4m Centaur-heritage with 2, 4 or 6 RL-10C engines (ACES family);

* 5.5m AIUS-heritage with 1 x J-2X or 4 x RL-10 (I suspect this is the Senate's choice, from the language in the authorisation bill);

* 8.4m with 6 x RL-10 (JUS).

As stated above, I suspect that the political winds are behind AIUS (I call it 'Ares-IA').  Nonetheless, the ACES family, including the stretched-length version for the Atlas-V Phase 3A, is probably the best choice from a programmatic standpoint and the JUS from a standpoint of capability.

With respect to the ACES family, does the stretched version used on the Atlas-V P3A have a specific designation?
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Offline alexw

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Re: Upper Stage for SLS
« Reply #7 on: 10/07/2010 08:57 AM »
The only significant BEO time-line that exists presently (AFAIK) is President Obama's proposal that BEO pathfinder missions begin in the early 2020s with the first NEO encounter in 2025 and the Phobos encounter/Mars orbiter in 2030 with a human landing on Mars "soon thereafter".  IMO, that means that the upper stage needs to get to hardware testing in space really no later than 2018/19.

There are basically three options for the upper stage right now:

* 5.4m Centaur-heritage with 2, 4 or 6 RL-10C engines (ACES family);

* 5.5m AIUS-heritage with 1 x J-2X or 4 x RL-10 (I suspect this is the Senate's choice, from the language in the authorisation bill);

* 8.4m with 6 x RL-10 (JUS).

As stated above, I suspect that the political winds are behind AIUS (I call it 'Ares-IA').  Nonetheless, the ACES family, including the stretched-length version for the Atlas-V Phase 3A, is probably the best choice from a programmatic standpoint and the JUS from a standpoint of capability.

With respect to the ACES family, does the stretched version used on the Atlas-V P3A have a specific designation?

   The ACES tanks are probably now 5.1m, not 5.4m; the latter would have matched the Atlas V payload fairing (and would have required new tooling in San Diego, I assume), the former would be built with the Delta IV tooling in Decatur, and I guess would fit under the fairing.

    Barr and Kutter says explicitly that there are actually two competing ULA families of stages: "Common Centaur" or "Common Upper Stage" (I think these refer to the same thing), and the full-blown ACES.  The point of the Common stage is to consolidate Centaur and (4m) DCSS for cost savings and probably get rid of the 4m payload fairing versions of Atlas and Delta, with the performance bought back (and then some) by prop options from 21mt-41mt. SEC and DEC both possible; I presume that SEC would win out *unless* CST-100 or NASA emerged as wanting engine-out or the increased performance (something like +2mT right now for Atlas xx2 if DEC was flying). It seems like the Common stage might happen on its own from ULA for cost reasons; one would think that Commercial Crew will bring this forward rather than pay to do the work for conventional (3m) DEC.

    ACES is actually separate, and enormously capable (bigger fairings, tanker, depots, low-boiloff, modular family, etc.) and that's the upper stage that almost certainly wouldn't happen unless NASA paid for it to support exploration. Might not even use RL-10C -- ULA speaks of interest in 2,4,6, even 9-engine clusters of a newer 25klbs-class engine, or even bigger (by which they presumably mean RL-60 or MB-60 (I'm not sure these are the same thing), or possibly Vinci, or maybe even Raptor).

   JUS is conceived to be like ACES.

    I really don't know what the 5.5 AIUS-derived is supposed to be like; HEFT speaks of making it into something with RL-10 and very low boiloff, but after removing the orange foam I'm not sure what it retains in common with AIUS.

    See Barr & Kutter 2010 (the recent Atlas V Phase II paper), and also the rev10a and rev11 (2010) versions of the Atlas V User's Guide.
    -Alex


Offline Ben the Space Brit

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Re: Upper Stage for SLS
« Reply #8 on: 10/07/2010 10:20 AM »
    I really don't know what the 5.5 AIUS-derived is supposed to be like; HEFT speaks of making it into something with RL-10 and very low boiloff, but after removing the orange foam I'm not sure what it retains in common with AIUS.

It would have the 5.5m barrel, the avionics ring and the common bulkhead propellent tanks in common.

Regarding ACES, I might be wrong, but it was my impression that the were to have a 5.4m diameter because that maches the OML of the Atlas-V 5m PLF.
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Offline A_M_Swallow

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Re: Upper Stage for SLS
« Reply #9 on: 10/07/2010 09:50 PM »
When a Solar Electric Propulsion (SEP) tug with changeable payload flies that can be used as an upper stage.  The first few SEP designs are likely to be too small for the SLS.  When the 100 metric ton (mT) VASIMR tug flies 70mT will provide quite a payload and propellant.  A reusable SEP could rendezvous with the 'package' left in LEO by the SLS.

Offline alexw

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Re: Upper Stage for SLS
« Reply #10 on: 10/07/2010 10:45 PM »
    I really don't know what the 5.5 AIUS-derived is supposed to be like; HEFT speaks of making it into something with RL-10 and very low boiloff, but after removing the orange foam I'm not sure what it retains in common with AIUS.
It would have the 5.5m barrel, the avionics ring and the common bulkhead propellent tanks in common.
     The bulkhead might well change in design if the thing is supposed to have essentially ZBO while spiraling up from LEO to EML1 over the course of a year.

Quote
Regarding ACES, I might be wrong, but it was my impression that the were to have a 5.4m diameter because that maches the OML of the Atlas-V 5m PLF.
   It looks like that was the old plan, possibly because if new tooling was required, might as well match the OML.

   However, look at the 2010 (rev11) revision of the Atlas V User's Guide -- it doesn't speak of ACES, but does say on p.8-1 under "Common Upper Stage": "Conceptually, the vehicle diameter is 5.1 m (17.2 ft) to accommodate current aluminum production capabilities at our Decatur, Alabama production facility." Barr and Kutter say only "5m", but that looks a like a 1-sig fig rounding that glosses over the change in build location. It seems doubtful that Common Centaur would be built 5.1m, but ACES would get all new tooling for 5.4m.

    If you're going to build new tooling for ACES, of course, it doesn't have to be 5.4m -- the EELVs have been investigated with 6 & 7 meter fairings. There might even be some argument for this in order to better use it on SLS. HEFT was looking at a ~7m CPS (??), which is neither the 5.5m AIUS tooling nor the 8.4m core tooling.
   -Alex

Offline jml

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Re: Upper Stage for SLS
« Reply #11 on: 10/07/2010 11:29 PM »

There are basically three options for the upper stage right now...

There are a few ways to make an 8.4m SLS upper stage.
One is the performance-optimized ACES-heritage JUS.

Another is to build the upper stage at MAF as essentially a shortened version of the 8.4m ET/Core using the existing tooling, but with the SRB attachment beam deleted from the inter-tank area, a thrust structure and propellant feed lines sized for the smaller upper stage engine(s), and the tank barrel walls milled somewhat thinner than the core.

Disadvantages: Heavier and lower performing than designs using a common inter-tank bulkhead like AIUS or Centuar or ACES. May require 5-seg SRBs and/or stretched-core and/or J-2X to meet, say, CxP's LOI mass requirements. Does not have inherent low-boiloff advantages of ACES design.

Advantages: Better suited to the "NASA should focus on designing and building `to cost' versus overall performance" philosophy of the Authorization Act (as stated in the Senate Committee's companion report). Requires less development effort than an all-new upper stage, and, at expected flight/production rates, does not require a separate production line, possibly saving a good $500 million or so per year of fixed costs over an ACES-style JUS.

Beyond this, of course, we could consider hybrid designs using, say, the core-stage LM-built barrel sections and core-stage tank domes on the top and bottom of the stage, but with the inter-tank completely replaced with an 8.4m diameter variant of the Boeing Ares I US composite common bulkhead.

Offline alexw

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Re: Upper Stage for SLS
« Reply #12 on: 10/07/2010 11:47 PM »
Interesting; thanks for pointing that out.

The problem with such a stage -- basically a latter-day SIVB? -- is that it probably eliminates EOR architectures, or use of propellant depots. That's leaves LOR for lunar surface. (Or, I suppose, MOR...)

You might be able to use it with staging out of EML, but you'll have to develop a completely different stage entirely to loiter to or tank at EML, probably obviating the cost benefits.

But maybe it's worth thinking about. Suppose you did an immediate burn from LEO to EML, not consuming all propellant, but pulling away from the Earthshine ASAP? What would the boiloff losses drop to during the T-EML-I orbit? Would a sunshield (like that proposed for Atlas V 4x1 unencapsulated Centaur) help?

Sounds ugly, but any option that could reduce costs is worth considering.
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Offline Proponent

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Re: Upper Stage for SLS
« Reply #13 on: 10/08/2010 02:39 AM »
Guys, this is all very interesting, but the issue raised in the OP is not which upper stage is best for SLS but rather is there much hope of ever getting an upper stage built in the first place.  I can't really say anybody's OT, since the thread's title is general (my fault; I was trying to make it emotionally neutral), but this is the topic in which I'm particularly interested.

The L2 thread whence this this thread came contained the following exchanges.  I've edited them for brevity; if either Jorge or kraisee believes I have misrepresented any of his statements, I hope he will correct me.

if the backers of SLS/Orion are seriously interested in going beyond LEO and they're setting deadlines, they ought at to set a deadline for a BEO-capable system (SLS with an upper stage), not for an LEO-only system.

The past is littered with bills that set deadlines so far in the future they became meaningless. CxP and Obama's FY11 proposal share that same flaw.

No more. It is time we focus on regaining base capability, setting realistic near-term deadlines, and not getting too far ahead of ourselves.

Jorge is spot-on regarding the point that anything in these bills referring to a time beyond a few years into the future is pretty meaningless.

During DIRECT, the term we use for anything beyond the current 4-year Presidential cycle, was "fantasyland".

At best, NASA will get a steady path until the next President is elected, or until both Congressional Houses change parties.

I don't know how Congress will look next year, so I can't even begin to predict what might happen there.

I do not expect Obama will win a second term, so I expect NASA has until no later than the middle of the next President's first year (mid-2013) to nail this new program down hard enough that it can't be uprooted.

This is the main reason why I simply do not believe that a 6-8 year Ares-V development effort can survive to operational flights, while a 3-4 year Jupiter-130 'foundational system' has a real chance of success.   IMHO, once you have that basic capability set in stone, an upgrade (Jupiter 24x) really becomes more a matter of 'when', not 'if' -- you may have to wait for a NASA-friendly President/Congress to get the J-24x upgrades, but they won't cancel the basic J-130 capability if it is already flying when they come into power.

After all, the Saturn V flew all up on its very first flight in 1967, and that was with all-new first and second stages.  This little change would make me feel a heck of a lot better about the Senate bill.

The Saturn V had several times the budget SLS will. The plain facts are that in this budgetary environment, the upper stage must be developed serially, *after* the core elements.  Therefore it is foolish to specify a deadline for it because it is too far in the future. This is not a "little" change.

It seems to me that the gist of what Jorge is saying, at least some of which kraisee agrees with, is that nobody knows what's going to happen several years down the road, and the development of an upper stage is further in the future than we can see clearly.

So far I pretty much agree.  But then Jorge seems to say that even setting a goal, a target date for an upper stage is counterproductive.  That I'm having trouble understanding.  But what's really worrying is that kraisee's post seems to say that, given budgetary reality, the viable strategy is to build an LEO-capable SLS and then hope, pray, cross your fingers and press your thumbs that the stars will align to permit the construction of an upper stage.  This scares me, and I think it's a terrible strategy.  If that's the best we do, if we can't even talk about a target date for a BEO-capable SLS, then I submit that the plan is incompatible with budgetary reality to begin with.  More precisely, the plan is compatible with budgetary reality if viewed as a plan to build a large HLV for getting to LEO; viewed as a plan for exploring beyond earth orbit it seems incompatible.

Anybody got a counterargument that will help me sleep?
« Last Edit: 10/08/2010 02:58 AM by Proponent »

Offline Robotbeat

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Re: Upper Stage for SLS
« Reply #14 on: 10/08/2010 03:46 AM »
I have no such argument. Jorge is right. Set a goal out to far, and it's meaningless, including an advanced upper stage. Proponent, you're right that that means no BLEO exploration.

The only answer (to allow BLEO exploration) is to use a cheap upper stage, which basically means one we already have. That's what I think OV-106 has been hinting at. Is that correct?
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