Author Topic: SLS General Discussion Thread 2  (Read 225539 times)

Offline A_M_Swallow

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Re: SLS General Discussion Thread 2
« Reply #480 on: 05/30/2016 08:30 PM »
An affordable launcher that can lift smaller payloads is more useful than a big one that is too expensive to operate.  In times of tight money, you can scale back to fewer loads, but at least you are making some progress.   
I disagree with your assertion that SLS is "too expensive to operate".  It is being designed to operate on less than the Shuttle budget, involving far fewer workers.  Shuttle flew for three decades.

 - Ed Kyle

Shuttle was not competing for missions with Dragon, CST-100 and Dream Chaser.

Offline Dasun

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Re: SLS General Discussion Thread 2
« Reply #481 on: 05/30/2016 09:10 PM »
Sigh, and SLS is not competing for missions with FH, Dragon, CST-100 and Dream Chaser!!!

SLS was designed, based on NASA requirements,  to support likely Mars mission architectures at relatively low flight rates.  SLS (and NASA) is not in competition with SpaceX - in fact SpaceX is just another aerospace contractor that can meet NASA needs.  Congress seems to have some firm ideas what SLS is going to do - DSH and Luna - in the next decade, lets us see if the money flows and the next POTUS agrees. 
I am vendor neutral, I just want to see spacecraft fly.

Offline gospacex

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Re: SLS General Discussion Thread 2
« Reply #482 on: 05/30/2016 09:30 PM »
SLS (and NASA) is not in competition with SpaceX.

Except that SLS *is* in competition with SpaceX.

By law, NASA can't compete with commercially available products.

As soon as FH flies, some difficult questions will be asked, "why do we pay these insane money for SLS?"
« Last Edit: 05/30/2016 09:30 PM by gospacex »

Offline Dasun

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Re: SLS General Discussion Thread 2
« Reply #483 on: 05/30/2016 09:34 PM »
FH does not compete with SLS - It throws much more upstairs !!!! And I think you will be waiting quite awhile for your "difficult" questions to be asked at the appropriate level for influence to happen!!
I am vendor neutral, I just want to see spacecraft fly.

Offline IRobot

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Re: SLS General Discussion Thread 2
« Reply #484 on: 05/30/2016 09:50 PM »
SLS (and NASA) is not in competition with SpaceX.

Except that SLS *is* in competition with SpaceX.

By law, NASA can't compete with commercially available products.

As soon as FH flies, some difficult questions will be asked, "why do we pay these insane money for SLS?"
For the moment NASA can claim FH does not have a large enough fairing and that the overall GTO performance is lower.

When and if BFR starts flying, SLS is dead.

Offline Coastal Ron

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Re: SLS General Discussion Thread 2
« Reply #485 on: 05/30/2016 09:50 PM »
Sigh, and SLS is not competing for missions with FH, Dragon, CST-100 and Dream Chaser!!!

I would agree with that.

Quote
SLS was designed, based on NASA requirements...

No, NASA was not involved in defining the SLS.  The Senators that wrote S.3729, and their advisors (which supposedly included former NASA Administrator Michael Griffin), created the specs without NASA involvement or coordination.

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...to support likely Mars mission architectures at relatively low flight rates.

Supposedly, but of course Congress has never funded such efforts.

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...in fact SpaceX is just another aerospace contractor that can meet NASA needs.

Maybe it's semantics, but a contractor builds what you need according to your specs.  A service provider already has a service that you require, even if it needs to be tweaked or modified for your requirements.  Based on that, to me SpaceX would be classified as a service provider.

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Congress seems to have some firm ideas what SLS is going to do...

"Congress" is composed of 100 Senators from 50 different states, and 435 Representatives from 435 political districts around the U.S.

The only certain way to know what Congress "wants" is to see what they vote for.  And so far they have not voted to fund any long-term programs that would require the unique services of the government-owned transportation system known as the SLS.

Maybe you have heard individual members of Congress express interest or desire for tasks the SLS would be suited for, but until they put it into legislation for all of Congress to vote on, it doesn't mean anything.

Quote
...lets us see if the money flows and the next POTUS agrees.

Yep.  Because nothing will be added this year.
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline AncientU

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Re: SLS General Discussion Thread 2
« Reply #486 on: 05/30/2016 11:22 PM »
First, SLS is implied as the 'world's most capable rocket.'  FH (with either the 1.7M or 1.9Mlbf thrust booster version) will lift more payload than SLS's first 'block' as shown by your and others' calculations. 
This is simply incorrect.  SLS Block 1 will boost 24.5 tonnes toward the Moon.  (It could, if needed, lift more than 90 tonnes to low earth orbit (70 tonnes is an artifact of the old SLS Block 0 design), but SLS is never going to LEO so that number is irrelevant.)  Falcon Heavy, even in full-expendable mode, would boost probably about 15 tonnes (plus or minus) toward the Moon.  (Falcon Heavy is also listed at only 54.4 tonnes to LEO in full-expendable mode.)

It would take three fully-expendable Falcon Heavies to match the payload of one SLS Block 1B trans-Mars.  It would take four Falcon Heavies to match one SLS Block 2.  I expect that Falcon Heavy and/or others like it will be needed to support deep-space missions, but the missions will be built around the unparalleled deep space throw-weight offered by SLS

 - Ed Kyle

The unparalleled throw weight offered by SLS will be paralleled and exceeded by an architecture that includes refueling on orbit.  Problem with SLS is it was created in the Apollo paradigm -- a paradigm which does not work for Mars.  NASA's own plans require dozens of SLS launches to assembly the pieces for a minimal Human mission to Mars.  You simply must launch early and often, which SLS will never do.

54.4 tonnes to LEO is simply not consistent with three 1.7-1.9Mlbf stages -- that's 2/3rds to 3/4ths of Saturn V liftoff thrust -- even a single core (skinny) F9 outperforms Saturn V in PMF (and delivers double the PMF of SLS).  FH outperforms F9 by a significant margin.  Then cross feed and Raptor powered second stage can be added just as Block 2 will eventually get a better second stage and new boosters.

At $3-4B per year, we are (NASA and Congress are) throwing away our opportunity to go to Mars by betting on a minimally capable launch system and unworkable architecture.  We will see which architecture actually gets us there.
« Last Edit: 05/30/2016 11:25 PM by AncientU »
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Offline spacenut

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Re: SLS General Discussion Thread 2
« Reply #487 on: 05/30/2016 11:27 PM »
Money can't flow unless the economy improves with jobs that create taxpayers (private enterprise jobs).  I'm afraid NASA is not going to get much of a budget increase in the next few years UNLESS the economy improves.  We are about $20 trillion in debt and it can't be kicked down the road forever.  Something has to give sooner or later.  NASA has been plodding along putting one foot in front of the other, while private companies like SpaceX and Blue Origin are making strides in recovery and increased payloads to orbit at LOWER costs.  So has Orbital and now ATK is proposing a new three stage solid to increase payloads at lower costs.  Mars can be done with 20 ton payloads, lots of them, but less than half that many payloads with 40-50 ton payloads from Falcon Heavy and the future Vulcan with ACES.  SLS can only lift about 100 tons to LEO, and they still need an upper stage for deep space probes and operations. 

The cost of SLS can come down IF they launch 3 per year or more, but not at one per year.  There is no vision from the president or a presidential candidate yet.  Without a vision and a goal, SLS will be dead as far as humans going to Mars with only one launch a year. 

Offline edkyle99

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Re: SLS General Discussion Thread 2
« Reply #488 on: 05/30/2016 11:59 PM »
54.4 tonnes to LEO is simply not consistent with three 1.7-1.9Mlbf stages -- that's 2/3rds to 3/4ths of Saturn V liftoff thrust -- even a single core (skinny) F9 outperforms Saturn V in PMF (and delivers double the PMF of SLS).  FH outperforms F9 by a significant margin.  Then cross feed and Raptor powered second stage can be added just as Block 2 will eventually get a better second stage and new boosters.
54.4 tonnes is what the manufacturer says Falcon Heavy can do.  If would lift half that, give or take, if the booster and first stages were recovered.  Your Saturn 5 liftoff thrust comparison doesn't add up because Saturn 5 used high energy liquid hydrogen fueled upper stages.  Falcon Heavy uses lower energy hydrocarbon engines on all of its stages.  It has to carry a heavier upper stage, relatively speaking, to make up the difference.  More liftoff thrust, relatively speaking, is needed to lift the extra mass. 

The key number is Falcon Heavy's 13.6 tonnes trans-Mars (full-expendable).  That's impressive, and can be exploited any number of ways, but it isn't 40 tonnes or 46 tonnes (SLS Block 1B Cargo or SLS Block 2).

 - Ed Kyle
« Last Edit: 05/31/2016 12:00 AM by edkyle99 »

Offline gospacex

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Re: SLS General Discussion Thread 2
« Reply #489 on: 05/31/2016 12:15 AM »
SLS (and NASA) is not in competition with SpaceX.

Except that SLS *is* in competition with SpaceX.

By law, NASA can't compete with commercially available products.

As soon as FH flies, some difficult questions will be asked, "why do we pay these insane money for SLS?"
For the moment NASA can claim FH does not have a large enough fairing...

...large enough *for what*? Can NASA point us to a funded payload which can't fit into FH's fairing?

Offline llanitedave

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Re: SLS General Discussion Thread 2
« Reply #490 on: 05/31/2016 04:11 AM »
SLS (and NASA) is not in competition with SpaceX.

Except that SLS *is* in competition with SpaceX.

By law, NASA can't compete with commercially available products.

As soon as FH flies, some difficult questions will be asked, "why do we pay these insane money for SLS?"

No, it's not.  When/if SpaceX gets it's BFR operational and agrees to release it for NASA missions, then they can talk.  Until then, the SLS has its own market.
"I've just abducted an alien -- now what?"

Offline Coastal Ron

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Re: SLS General Discussion Thread 2
« Reply #491 on: 05/31/2016 04:24 AM »
The key number is Falcon Heavy's 13.6 tonnes trans-Mars (full-expendable).  That's impressive, and can be exploited any number of ways, but it isn't 40 tonnes or 46 tonnes (SLS Block 1B Cargo or SLS Block 2).

We're not going to expand humanity out into space by relying only on direct launch to the destination.  That is Apollo-style thinking, and Apollo only used that method for expediency, not because it was the best way.

Regardless the launchers used, we're going to be assembling spaceships and expeditions in local space before going into deep space.  We've already gained a lot of knowledge how to do this with the 450mT ISS, so we know it's well within our capabilities.  No need to throw away that knowledge and ability...
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline woods170

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Re: SLS General Discussion Thread 2
« Reply #492 on: 05/31/2016 09:09 AM »
When and if BFR starts flying, SLS is dead.
Minor nit:
Only if SpaceX makes BFR commercially available.

Offline Proponent

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Re: SLS General Discussion Thread 2
« Reply #493 on: 05/31/2016 02:25 PM »
54.4 tonnes is what the manufacturer says Falcon Heavy can do.  If would lift half that, give or take, if the booster and first stages were recovered.  Your Saturn 5 liftoff thrust comparison doesn't add up because Saturn 5 used high energy liquid hydrogen fueled upper stages.  Falcon Heavy uses lower energy hydrocarbon engines on all of its stages.  It has to carry a heavier upper stage, relatively speaking, to make up the difference.  More liftoff thrust, relatively speaking, is needed to lift the extra mass. 

The key number is Falcon Heavy's 13.6 tonnes trans-Mars (full-expendable).  That's impressive, and can be exploited any number of ways, but it isn't 40 tonnes or 46 tonnes (SLS Block 1B Cargo or SLS Block 2).

As you implicitly note in mentioning SLS's TMI capabilities, NASA sees fit to break its Mars mission into chunks of less than 50 tonnes.  That begs the question of whether those chunks could be lofted in to LEO by a Falcon Heavy or equivalent and then boosted onward a cis-lunar staging point or directly to Mars after rendezvous and docking with expendable departure stages or perhaps reusable robotic transfer stages.  The latter seems particularly interesting, since the EMC architecture includes reusable transfer stages anyway.

Offline RonM

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Re: SLS General Discussion Thread 2
« Reply #494 on: 05/31/2016 03:18 PM »
SLS (and NASA) is not in competition with SpaceX.

Except that SLS *is* in competition with SpaceX.

By law, NASA can't compete with commercially available products.

As soon as FH flies, some difficult questions will be asked, "why do we pay these insane money for SLS?"
For the moment NASA can claim FH does not have a large enough fairing...

...large enough *for what*? Can NASA point us to a funded payload which can't fit into FH's fairing?

Um, let's see, how about Orion? Of course it doesn't need a fairing, but saying that there are no funded payloads that can't fit into a FH fairing is silly. How about projected payloads needed for a Mars mission. That's a more realistic comparison.

Something as large as a lander would need 8.4 m or 10 m fairings. That will take SLS. Other components could be smaller and launched by commercial rockets. SLS will have a very low flight rate. It will take a combination of SLS and commercial rockets to assemble a Mars mission in a reasonable amount of time.

Offline Coastal Ron

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Re: SLS General Discussion Thread 2
« Reply #495 on: 05/31/2016 03:35 PM »
How about projected payloads needed for a Mars mission. That's a more realistic comparison.

Depends on the architecture you look at.  There are some that assume an HLV will be available, and some that assume existing launchers will be used.

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Something as large as a lander would need 8.4 m or 10 m fairings.

If we're going to Mars in fleets that we assemble in local space, then we might assemble landers in space too.  No need to be limited by the constraints of what can fit on one small HLV.

Quote
It will take a combination of SLS and commercial rockets to assemble a Mars mission in a reasonable amount of time.

It will take a combination of launchers, that we can agree on.  But since NASA is likely decades away from going to Mars on it's own, arguing the dimensions of the lander is premature at best.

And NASA has no idea how to land large landers on Mars anyways.  NASA technology currently maxes out at 899 kg for placing mass on Mars, which is too small for humans.  So it's going to take NASA decades to scale up that capability.

Or, if SpaceX is successful in their Mars endeavors, NASA can just buy a ride to Mars with them.  Regardless, a NASA HLV of any type won't be needed for quite a while to support trips to Mars.
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline RonM

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Re: SLS General Discussion Thread 2
« Reply #496 on: 05/31/2016 03:51 PM »
Or, if SpaceX is successful in their Mars endeavors, NASA can just buy a ride to Mars with them.  Regardless, a NASA HLV of any type won't be needed for quite a while to support trips to Mars.

Yes, I think the biggest problem with SLS is that we really don't need it for at least another decade, if ever, because of a lack of funding. They should have followed Obama's plan to do research for five years before deciding on a launch vehicle. Then fund a commercial heavy launch vehicle and see what SpaceX, ULA, etc. could come up with. Unfortunately, that's not what happened and we have spent billions of dollars on SLS. That wouldn't be bad if Congress had funded payloads suitable for SLS.

Maybe LockMart will talk Congress into their latest idea. That would get us to Mars orbit in a little over a decade.

http://forum.nasaspaceflight.com/index.php?topic=40324.0

Offline Robotbeat

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Re: SLS General Discussion Thread 2
« Reply #497 on: 05/31/2016 04:09 PM »
FH does not compete with SLS - It throws much more upstairs !!!! And I think you will be waiting quite awhile for your "difficult" questions to be asked at the appropriate level for influence to happen!!
The law says that the missions should be designed to accommodate commercial vehicles. So even if SLS does throw slightly more to orbit, that does NOT mean FH doesn't compete with SLS.
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 Khadgars

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Re: SLS General Discussion Thread 2
« Reply #498 on: 05/31/2016 05:07 PM »
The goal post on which SLS will die has continually been moved and talked about ad nauseum.

NASA has already stated they can create the DSH and get humans to Mars under the current budget via Lockheed's Mars Base Camp or something similar to it.  Its the lander that doesn't fit into existing or foreseeable budget.

SLS does and will have payloads.  Getting to Mars is going to take SLS and commercial launchers and the whole industry pulling in the same direction.

Offline oldAtlas_Eguy

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Re: SLS General Discussion Thread 2
« Reply #499 on: 05/31/2016 05:16 PM »
The following shows what a typical NASA program to develop hardware for a Mars mission would look like.

Authorization/Appropriations                   Oct-17
Contract for Authorization Study start           Mar-18
Architecture selected                                   Mar-19
Contract for Design and Development start   Sep-19
PDR                                                           Sep-21
CDR                                                           Sep-24
Hardware build complete                           Sep-29
Launch Earliest Mars Synod                   Feb-31

This is how slow NASA really is. The biggest problem is in program startup. It would take 3 years from now just to get a contractor on contract to start the design work.

SLS would not be used for any payloads like this until the 2030's just like NASA has been stating all along.

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