Author Topic: Shuttle Stack vs Space Launch System  (Read 9655 times)

Offline spectre9

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Shuttle Stack vs Space Launch System
« on: 12/12/2012 11:18 AM »
I want to understand how SLS compares to the shuttle stack. They use the same hardware so adding more thrust should make a more capable system.

Obviously there is the difference that shuttle takes engines to orbit and SLS doesn't but you still need those engines to do most of the lift. When the engines are staged with the tank there should be a little boost.

Shuttle lift off weight 110mt+. Take off the SSMEs that's about 95mt there. Obviously you need to add back on the weight of a payload fairing but that makes SLS more aerodynamic than the shuttle stack so that's a boost right?

There's also the weight of the MPS to take into account, shuttle took that to orbit too. It's very difficult to get a good picture of what a directly shuttle derived system should be capable of.

Anybody got the figures on what the highest shuttle lift off weights have been?

SLS is just shy of 9million lbf lift off thrust. That to me says well over 100mt+ and I'm no rocket scientist. It would need some poor Isp not to perform very well.

With DCSS doing a final burn just to get to LEO that payload would get even better yeah?

I think there are more confused posters just like me that would love some to get some more information on exactly how the performance of SLS is derived out of the shuttle hardware.

I'm guilty of spreading FUD about the SLS and I want to apologise for that.

Online QuantumG

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Re: Shuttle Stack vs Space Launch System
« Reply #1 on: 12/12/2012 09:13 PM »
Why do you have to speculate about this?

Shouldn't there be an actual design for the SLS by now?

Shouldn't you be able to just read these numbers from a report?
Jeff Bezos has billions to spend on rockets and can go at whatever pace he likes! Wow! What pace is he going at? Well... have you heard of Zeno's paradox?

Online RotoSequence

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Re: Shuttle Stack vs Space Launch System
« Reply #2 on: 12/12/2012 10:46 PM »
Why do you have to speculate about this?

Shouldn't there be an actual design for the SLS by now?

Shouldn't you be able to just read these numbers from a report?

Why should there be a finalized design and numbers from a final design spec to cite when the program was only officially announced 15 months ago?

Demonstrating your disapproval for the program by asking rhetorical questions that you already have answers to is unbecoming.
« Last Edit: 12/12/2012 10:48 PM by RotoSequence »

Offline spectre9

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Re: Shuttle Stack vs Space Launch System
« Reply #3 on: 12/12/2012 11:03 PM »
I realise this might not be easiest post to answer.

I'm not going to speculate any further until real facts about the evolution of this system are known.

70mt was supposed to be the initial requirement. Just how far has NASA gone over that requirement if at all?

The margins might be all soaked up by something unknown.

Input from posters more knowledgeable than I is greatly appreciated.

Should this be easily explainable or should it be confusing?

If it's going to be confusing that's going to spread FUD without me having to.  :P

Online QuantumG

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Re: Shuttle Stack vs Space Launch System
« Reply #4 on: 12/12/2012 11:46 PM »
Why should there be a finalized design and numbers from a final design spec to cite when the program was only officially announced 15 months ago?

Demonstrating your disapproval for the program by asking rhetorical questions that you already have answers to is unbecoming.

Oh, I'm sorry, it's only been 15 months.. you're obviously right, they couldn't possibly have a design ready in such a short amount of time.


Jeff Bezos has billions to spend on rockets and can go at whatever pace he likes! Wow! What pace is he going at? Well... have you heard of Zeno's paradox?

Online RotoSequence

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Re: Shuttle Stack vs Space Launch System
« Reply #5 on: 12/12/2012 11:54 PM »
Oh, I'm sorry, it's only been 15 months.. you're obviously right, they couldn't possibly have a design ready in such a short amount of time.

While you mean this in a deeply sarcastic sense, you could be surprised just how many things happen in the real world that are built around 18 month milestone schedules, and there is still work to do before finalizing the design of the SLS core. This isn't Apollo; NASA doesn't have an essentially unlimited budget to throw at it, a clear purpose for the endeavor, or a firmly established deadline to maximize the efficacy of their jobs.
« Last Edit: 12/12/2012 11:55 PM by RotoSequence »

Online QuantumG

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Re: Shuttle Stack vs Space Launch System
« Reply #6 on: 12/13/2012 12:21 AM »
So ~30 months before PDR is normal?

Jeff Bezos has billions to spend on rockets and can go at whatever pace he likes! Wow! What pace is he going at? Well... have you heard of Zeno's paradox?

Online RotoSequence

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Re: Shuttle Stack vs Space Launch System
« Reply #7 on: 12/13/2012 12:29 AM »
So ~30 months before PDR is normal?

30 months to work out what the vehicle is supposed to do, what systems will be needed to do what they want the vehicle to do, identifying risks and how to mitigate them, and then ensuring that the technologies they are looking to put together are sufficiently matured, all the needed resources are allocated, and making sure they have the capability to verify system performance before proceeding to the final design stages? That honestly sounds like a reasonable development schedule to me, especially considering the absence of a properly specific mission objective for the rocket to meet from NASA's leadership. When you don't know exactly what you have to do, one would imagine that a high achiever will strive to make the vehicle capable of handling as much as possible.
« Last Edit: 12/13/2012 12:38 AM by RotoSequence »

Offline spectre9

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Re: Shuttle Stack vs Space Launch System
« Reply #8 on: 12/13/2012 12:46 AM »
When nobody knew anything about rocket science in the 50s NASA could tell people that big rockets and bigger rockets are the only way to go BEO.

Now we know you can get a big rocket and do some EOR with your payload and propulsion stage.

Maybe NASA is designing this way to prevent needing to ask for funding twice for the upper stage.

Make the core so powerful that DCSS is useful?

Unfortunately they've just added to their production costs which is something maybe they shouldn't have done?

So because NASA doesn't trust their upper stage will get funded this is the compromise?

Offline edkyle99

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Re: Shuttle Stack vs Space Launch System
« Reply #9 on: 12/13/2012 02:27 AM »
I want to understand how SLS compares to the shuttle stack. They use the same hardware so adding more thrust should make a more capable system.
An orbiter was not just a payload.  It was also part upper stage.  The upper stage mass is usually not included in the payload capability of a launch system. 

An orbiter with an ISS-type payload probably weighed 110 tonnes when it separated from the ET, and probably 3 or 4 tonnes less after it burned OMS propellant to actually enter a stable orbit.  This included probably 15 tonnes for the SSMEs and their plumbing and other 14-18 tonnes for the thrust structure, aft fueselage, OMS pods, OMS/RCS propellant, etc..  The ET itself weighed something like 29.5 tonnes empty, but probably more than 40 tonnes at separation including residual propellant. 

SLS keeps the engines on the core, so that mass (engines and thrust structure, etc.) is automatically subtracted from the "payload" capability.  That, right there, would reduce a Shuttle-equivalent vehicle down to 70-ish tonnes to LEO based on that "bookkeeping" alone.  SLS Block 1 will improve on that 70 tonnes through the addition of extra SRB segments and much more core propellant, burned by an additional engine.  That extra energy will allow Block 1 to get 90 tonnes or so to LEO, or nearly to LEO.

 - Ed Kyle
« Last Edit: 12/13/2012 02:35 AM by edkyle99 »

Offline spectre9

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Re: Shuttle Stack vs Space Launch System
« Reply #10 on: 12/13/2012 03:07 AM »
Thanks for that answer Ed  ;D

That really helps me understand what's going on here.

It's too bad this system isn't that efficient. I can see directly shuttle derived systems have a possibility of not reaching the 70mt requirement but that's why ATK should've be allowed to upgrade the boosters from the start.

Giving NASA any numbers that have to build with causes problems. They should build to the mission and not have to worry about LEO numbers.

Does NASA intend to just keep the Block 1 with the 5m upper stage? Saves building a large fairing if they don't have a large payload that requires it anyway.

Would it be cheaper to just keep upgrading DCSS rather than building the 8.4m upper stage? I guess NASA needs it to get to 130mt.

The requirement could've been "NASA can build a big shuttle derived rocket with an upper stage to be funded in parallel". No numbers at all just let them figure it out and then they can propose vehicles until somebody picks the cheap version.

Offline MP99

Re: Shuttle Stack vs Space Launch System
« Reply #11 on: 12/13/2012 07:19 AM »
Make the core so powerful that DCSS is useful?

That's the wrong way around. DCSS is too small to maximise the capability of a 70mT version, never mind block I.

SLS's unused performance can be used to launch the whole stack (inc core) to a slightly higher Apogee, but that's making the best of the situation rather than well optimised.


Would it be cheaper to just keep upgrading DCSS rather than building the 8.4m upper stage? I guess NASA needs it to get to 130mt.

According to Jon Goff, there's a limit to how much you can stretch a fully-fuelled single-RL10 DCSS before gravity losses on TLI burn start biting into performance.

If you have to start fitting multiple engines, it's not DCSS any more.

cheers, Martin

Offline spectre9

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Re: Shuttle Stack vs Space Launch System
« Reply #12 on: 12/13/2012 07:24 AM »
Extra engines are an upgrade even if you then have to call it something else.

I think it's likely they will go down this road.

Saturn Vs upper stage was the S-IVB and that was only 6.6m.

Sure SLS might be better with a large upper stage but it's not getting one.

Offline TomH

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Re: Shuttle Stack vs Space Launch System
« Reply #13 on: 12/13/2012 08:02 AM »
Why should there be a finalized design and numbers from a final design spec to cite when the program was only officially announced 15 months ago?

Demonstrating your disapproval for the program by asking rhetorical questions that you already have answers to is unbecoming.

Oh, I'm sorry, it's only been 15 months.. you're obviously right, they couldn't possibly have a design ready in such a short amount of time.

While you mean this in a deeply sarcastic sense, you could be surprised just how many things happen in the real world that are built around 18 month milestone schedules, and there is still work to do before finalizing the design of the SLS core. This isn't Apollo; NASA doesn't have an essentially unlimited budget to throw at it, a clear purpose for the endeavor, or a firmly established deadline to maximize the efficacy of their jobs.

So ~30 months before PDR is normal?

The joint strike fighter program was initiated in 1992. The planes coming off the line now are still undergoing assessment by test pilots. Some of them are being labeled as production models, but that is just in name only as the plan specifies that the first "production" planes will roll out before the testing phase has even made much progress. They spent years and years refining the design of this plane. They still haven't made great progress toward the STOL and and especially the carrier variants. This is a $1.5 Trillion program. As these kinds of things go, STS has a miniscule budget and the design is far ahead of where many other programs are after only such a few months. Toyota spends longer than this designing a new car with only minor changes, and we are talking about the most advanced rocket ever conceived. This is not simple stuff; the connotation of the term "Rocket Science" is not a joke; it truly is exceptionally complex.

Offline gospacex

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Re: Shuttle Stack vs Space Launch System
« Reply #14 on: 12/13/2012 09:27 AM »
As these kinds of things go, STS has a miniscule budget and the design is far ahead of where many other programs are after only such a few months.

Phlease!!! The amount of half-truths (aka "lies") in your post is insulting - you think we are all dumb here?

"after only such a few months". You think we aren't aware that NASA worked on a Shuttle derived LV, Ares-V, for SIX YEARS by now (and horribly failed)?

"STS [sic] has a miniscule budget". Tell that to SpaceX, who spent just one billion TOTAL (not "per year"!) to successfully develop two new LV's, one capsule and five new rocket engines; and is well on the way to field a 50-tons-to-LEO heavy LV, to borrow your phrase, after only a few years from now?
« Last Edit: 12/13/2012 09:29 AM by gospacex »

Online RotoSequence

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Re: Shuttle Stack vs Space Launch System
« Reply #15 on: 12/13/2012 10:27 AM »
Phlease!!! The amount of half-truths (aka "lies") in your post is insulting - you think we are all dumb here?

"after only such a few months". You think we aren't aware that NASA worked on a Shuttle derived LV, Ares-V, for SIX YEARS by now (and horribly failed)?

"STS [sic] has a miniscule budget". Tell that to SpaceX, who spent just one billion TOTAL (not "per year"!) to successfully develop two new LV's, one capsule and five new rocket engines; and is well on the way to field a 50-tons-to-LEO heavy LV, to borrow your phrase, after only a few years from now?

SpaceX does not have the baggage associated with the rules and overhead that Government acquisition programs have by law, nor does it have the institutional cultures of established aerospace companies that traditionally compete for these programs; the two are not directly comparable.
« Last Edit: 12/13/2012 10:28 AM by RotoSequence »

Offline MP99

Re: Shuttle Stack vs Space Launch System
« Reply #16 on: 12/13/2012 12:56 PM »
Phlease!!! The amount of half-truths (aka "lies") in your post is insulting - you think we are all dumb here?

"after only such a few months". You think we aren't aware that NASA worked on a Shuttle derived LV, Ares-V, for SIX YEARS by now (and horribly failed)?

I think you are, shall we say, "confused" there.

NASA did pretty much nothing on Ares V during CxP. Plan was that once Ares I was flying, focus would switch and they'd start on Ares V.


"STS [sic] has a miniscule budget". Tell that to SpaceX, who spent just one billion TOTAL (not "per year"!) to successfully develop two new LV's, one capsule and five new rocket engines; and is well on the way to field a 50-tons-to-LEO heavy LV, to borrow your phrase, after only a few years from now?

Again, a little confused here, I think. SpaceX was founded in 2002, and wiki says they announced F9 in 2005. If they fly v1.1 next year that will be eight years (and they must have done work before announcing, probably similar to that put into Ares V & SLS configs before NASA's programme started). Get your facts straight.

Add eight years from start of the SLS program and you have? Yup, around 2019, by which time SLS should have flown and be progressing towards a flight carrying people. Of course, SpaceX's crew capability (LAS, etc), should be available around 11-12 years from the time F9 was announced. That would be 2022-23 in NASA's programme, ie longer than NASA's schedule.



Also, I'm sure I've seen a rule-of-thumb that launcher costs scale somewhat in line with GLOW (someone will correct me if I'm wrong). F9 is about 1/10 of SLS's GLOW, and if you scale SpaceX's budget up by a factor of 10, how far is it out then from F9?

Martin

Offline sdsds

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Re: Shuttle Stack vs Space Launch System
« Reply #17 on: 12/28/2012 04:44 AM »
I scanned this thread, but didn't see some info that seems quite relevant to the original poster's questions. Quoting first from Written Statement for Testimony, Jim Chilton, Boeing Space Exploration Vice President, Program Manager, Space Launch System Stages, September 12, 2012: "To further reduce production costs, Core stage will use conventional rather than exotic materials for primary structure (AL2219 instead of AL2195)." As I understand it, this means tank masses more like the Shuttle LWT rather than the SLWT. NASA says AL2195 allows mass reduction of "large liquid propellant tanks by 25 percent." The SLS core dry mass makes quite a difference in overall performance. Now that they're past PDR, is that value generally available?
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Offline clongton

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Re: Shuttle Stack vs Space Launch System
« Reply #18 on: 12/30/2012 03:53 PM »
It's very difficult to get a good picture of what a directly shuttle derived system should be capable of.

www.directlauncher.org

Don't forget that the publicly released figures included a 15% margin that was built in in addition to all the margins that NASA typically employs. This initially confused the engineers at Aerospace Corp in Los Angles when we went out there at the request of the Augustine Commission because they were coming up with greater capacity than we were publishing. We didn't tell them that up front until they came to us and asked why their numbers were higher than ours (baseball cards). It was important for them to arrive at the actual capability by themselves, which they did. It was actually capable of much greater IMLEO and TLI performance than the baseball cards showed.

Quote
Anybody got the figures on what the highest shuttle lift off weights have been?

Shuttle never launched with it's payload capacity maxed out - far from it. It was limited to what the landing gear could support if it ever had to abort to a landing, either at KSC or anywhere else. It had to be able to land with the payload still in the payload bay.
Chuck - DIRECT co-founder
I started my career on the Saturn-V F-1A engine

Offline Proponent

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Re: Shuttle Stack vs Space Launch System
« Reply #19 on: 12/31/2012 03:29 AM »
I scanned this thread, but didn't see some info that seems quite relevant to the original poster's questions. Quoting first from Written Statement for Testimony, Jim Chilton, Boeing Space Exploration Vice President, Program Manager, Space Launch System Stages, September 12, 2012: "To further reduce production costs, Core stage will use conventional rather than exotic materials for primary structure (AL2219 instead of AL2195)." As I understand it, this means tank masses more like the Shuttle LWT rather than the SLWT. NASA says AL2195 allows mass reduction of "large liquid propellant tanks by 25 percent." The SLS core dry mass makes quite a difference in overall performance.

This illustrates a fundamental problem with SLS's core-plus-boosters design.  The core is lugged all the way to orbit, hence the entire thing is weight-critical:  each extra kilo on it is a kilo of payload lost.  A classic two-stage design wouldn't have this problem, and also wouldn't have such a need for expensive high-performance engines like RS-25s.  It makes more sense for a re-usable design, where you can to re-use the hardware you've invested so much money in making light.

Tags: SLS