Author Topic: SLS General Discussion Thread 2  (Read 225657 times)

Offline Jim

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Re: SLS General Discussion Thread 2
« Reply #160 on: 09/28/2015 07:55 PM »
1.  Someone said, somewhere here, that when facility to manufacture Saturn V 1st and 2nd stages were for 6 Saturn V's per year.  So, the facility can at least do 6.

2.  The VAB can process at least 4 at a time.  It has 4 bays.  They would have to build at least 4 platforms.   

1.  Not true.  Space/volume does not determine capability.  The tooling does.  Anyways, it is a shared facility and there are other users

2.  See above. The 4 bays were never fully outfitted and even during shuttle, only two were outfitted.  Also, there is not only one pad for SLS.

Online Coastal Ron

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Re: SLS General Discussion Thread 2
« Reply #161 on: 09/28/2015 07:55 PM »
Someone said, somewhere here, that when facility to manufacture Saturn V 1st and 2nd stages were for 6 Saturn V's per year.  So, the facility can at least do 6.

The production line for a 2015 Ford Mustang is not the same as the production line that was used for the 1968 Ford Mustang, and so it is with the Saturn S-IC and the SLS 1st stage.  The amount of space that they need maybe completely different between the two.

And as a point of reference, at least according to Wikipedia:

"It took roughly seven to nine months to build the tanks and 14 months to complete a stage."

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So, can ATK manufacture 12 solid boosters a year to match?

I'm not sure why anyone is worried about being able to build enough SLS.  If the money is there, American industry can do just about anything - and the SLS is not a very complicated structure to build compared to what American industry has already done.  Your worry should be directed at the politicians that so far have not funded any production SLS flights, nor approved any missions that require the SLS.  If Congress coughs up the money, Boeing and it's suppliers will build it.

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I guess if they are going to Mars using SLS, they are probably going to have to use other launchers to launch components, fuel, SEP tugs, habitats, or something to LEO or to L2 and assemble to go to Mars.

The current NASA Mars proposal only assumes using the SLS.  No commercial or partner launchers.

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More SLS launches would equal less in space assembly.

There are trade-offs that negate that potential advantage.
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Online Endeavour_01

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Re: SLS General Discussion Thread 2
« Reply #162 on: 09/28/2015 08:54 PM »
NASA simply desgined the factory for SLS and for an flight rate of 1-2 an year and it likely was an attractive thing to do(complies with the law--which states nothing about production rate). President not actively engaged(not his baby) and does nothing to further his goal(commercialization of human spaceflight). Saves money(designing for smaller scales of production is cheaper than larger scales). All parties are fine with it.

It isn't one tool, it is the whole thing.

The evolvable Mars campaign has a maximum of 3 SLS launches during certain years. Do we really need to up the SLS production rate beyond 2 a year? Assuming NASA only uses SLS they could store extra cores made during the decade of once a year flights and then use them for the years that require 3 flights. Block 2B uses the same core and upper stage as Block 1B.

Alternatively you could tag team SLS with Vulcan and Falcon to launch some elements of the mission. That should get rid of the need to launch more than 2 SLS's a year.

From where I am sitting the production rate is fine for what is needed to have robust cis-lunar and Mars missions.
I cheer for both NASA and commercial space. For SLS, Orion, Falcon 9, Falcon Heavy, Dragon, Starliner, Cygnus and all the rest!
I was blessed to see the launch of Space Shuttle Endeavour on STS-99. The launch was beyond amazing. My 8-year old mind was blown. I remember the noise and seeing the exhaust pour out of the shuttle as it lifted off. I remember staring and watching it soar while it was visible in the clear blue sky. It was one of the greatest moments of my life and I will never forget it.

Online Coastal Ron

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Re: SLS General Discussion Thread 2
« Reply #163 on: 09/28/2015 10:07 PM »
The evolvable Mars campaign has a maximum of 3 SLS launches during certain years. Do we really need to up the SLS production rate beyond 2 a year? Assuming NASA only uses SLS they could store extra cores made during the decade of once a year flights and then use them for the years that require 3 flights. Block 2B uses the same core and upper stage as Block 1B.

Speaking from a production scheduling standpoint, sure, you probably could do that.  However from a budget standpoint that increases your spending upfront, and it decreases your vehicle flexibility to a certain degree (i.e. units built years in advance don't have current improvements).

But if the Mars plan gets approved, the cost of expanding the SLS production line will likely be assumed as part of the plan, and overall would probably only be in the single digits as far as overall program cost.

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Alternatively you could tag team SLS with Vulcan and Falcon to launch some elements of the mission. That should get rid of the need to launch more than 2 SLS's a year.

Sure, or even go all commercial.  Letting commercial launchers into the mix opens Pandora's box for NASA, since it will highlight the disadvantages of a government-run HLV transportation system - chief of which would be cost and redundancy.  Quite the conundrum...
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Online Endeavour_01

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Re: SLS General Discussion Thread 2
« Reply #164 on: 09/28/2015 10:18 PM »

Sure, or even go all commercial.  Letting commercial launchers into the mix opens Pandora's box for NASA, since it will highlight the disadvantages of a government-run HLV transportation system - chief of which would be cost and redundancy.  Quite the conundrum...

To quote Judge Dredd, "I knew you'd say that."   ;)

Going all commercial wouldn't work IMHO. You would run into capacity and volume issues that I have pointed out previously. A number of payloads as well as manned Orion launches wouldn't work on a Falcon Heavy or a Vulcan. The best bet is to use commercial to supplement SLS.
I cheer for both NASA and commercial space. For SLS, Orion, Falcon 9, Falcon Heavy, Dragon, Starliner, Cygnus and all the rest!
I was blessed to see the launch of Space Shuttle Endeavour on STS-99. The launch was beyond amazing. My 8-year old mind was blown. I remember the noise and seeing the exhaust pour out of the shuttle as it lifted off. I remember staring and watching it soar while it was visible in the clear blue sky. It was one of the greatest moments of my life and I will never forget it.

Offline 93143

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Re: SLS General Discussion Thread 2
« Reply #165 on: 09/28/2015 10:49 PM »
...We were discussing marginal costs associated with changes in flight rate...

What was the original supposition that lead to this discussion about "marginal cost"?  I think it's been a while, and I've forgotten.

It was suggested that it might be worthwhile to use SLS as a substitute for Delta IV Heavy to launch large DoD payloads, considering that SLS would already exist for unrelated reasons, whereas DIVH wouldn't:

http://forum.nasaspaceflight.com/index.php?topic=38021.msg1425851#msg1425851

The question about DIVH doesn't seem to turn exclusively or even primarily on the marginal cost question, but the marginal cost question was apparently contentious on its own.

There was an earlier discussion in another thread, sparked by an offhand comment I made in a post on a different subject:

http://forum.nasaspaceflight.com/index.php?topic=38171.msg1424057#msg1424057

It was off topic there, but it's not off topic here, so here it is.

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Is "marginal cost" something that will play into the discussion about the future of the SLS?  In other words, is a future NASA Administrator going to be called in front of Congress and asked what the "marginal cost" is of the SLS, and that their answer will determine whether an additional SLS is authorized?

Or are we talking about something that only accountants get excited about?

The marginal cost we've been discussing is the cost incurred by the U.S. Government in changing the SLS flight rate.  If you wanted to put a DoD payload on SLS, with sufficient lead time of course, this is what you'd pay to do that.  If you wanted to double the launch rate from one per year to two, this is what you'd pay every year to do that.  Exclusive of payload costs, of course...

This could easily come up in front of Congress, because unless someone's talking about cancelling the program outright, marginal cost is the only cost associated with SLS that actually affects overall budget allocations (how the money is distributed between agencies is a separate issue).

...of course, that's only technically true below the current maximum production rate.  Going above that is a bit different, because in addition to the marginal cost (which is higher because of the infrastructure delta), you also have the one-time capital cost of the upgrade...

EDIT: It's probably more likely that Congress would ask about the total cost of a plan, and the marginal cost of increasing the SLS flight rate to execute the plan would be rolled into the estimate, perhaps implicitly.  It's still important that anyone contemplating a use for SLS understand the difference between total cost and marginal cost, so as to properly forecast what the effect of a change will be.

Do we really need to up the SLS production rate beyond 2 a year?

Do we really need a space program at all?

Jupiter was supposed to fly six times per year, two J-130s for ISS runs and four J-246es for two Constellation-class lunar surface sorties (or two of each configuration; apparently J-130 could loft Orion+Altair to LEO if they did separate circ burns).  And the flight rate could easily increase if anything else wanted doing.

Now, we probably don't need SLS making milk runs to the ISS.  But I see no reason why a couple of heavy lunar landers per year (perhaps developed from existing upper stage technology, so as to save money vs. Altair) should be out of scope, except that Obama's "vision" seems to have sucked all the hope out of everybody.  Add depots (with tankers), and you've freed up a couple of launches, but you still have to go past two per year if you want to do literally anything else on top of your six-month moon base rotation.  Like, say, launch scientific probes to the outer planets, or large space telescopes, or BA-330s to cislunar space, or BA-2100s to LEO, or the notional giant black payloads that have been hinted about, or, y'know...  go to Mars.  Especially every two years...

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More SLS launches would equal less in space assembly.
There are trade-offs that negate that potential advantage.

Trade-offs?  Sure, though the big one is the mere existence of SLS and its budget line (again, marginal cost proves relevant).  Negate?  Not necessarily.  Remember, you're adding a lot of design and development, a lot of extra hardware and extra mass, and a lot of extra on-orbit operations, and the result may even end up less capable and/or less robust because of all the hardware overhead.

Parkinson and Hempsell (2003) claim that "space station acquisition costs are dominated by the level of modularization and in orbit assembly, to the extent that in a mixed launcher fleet it pays to use the largest launch system regardless of any impact on launch costs" (emphasis added).  This of course assumes that the HLV already exists, so development costs are excluded.  Mark Hempsell has backed off from this position somewhat, and as of 2011 seems to have believed that the combination of inflatable structures and a successful Skylon makes the tradeoff with an HLV "finely balanced".

Now, a Mars mission is not a space station.  But plainly the in-space assembly question cannot be carelessly handwaved away.
« Last Edit: 09/29/2015 12:02 AM by 93143 »

Online Coastal Ron

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Re: SLS General Discussion Thread 2
« Reply #166 on: 09/28/2015 11:10 PM »
Going all commercial wouldn't work IMHO. You would run into capacity and volume issues that I have pointed out previously.

As I've mentioned previously, I don't see any capacity issues for the SLS.  Sure there would be a cost to expanding the current production capabilities, but it would be doable, and probably for a cost less than what this initial capacity cost.

For commercial launchers there are no capacity issues either.  I've heard the number 160 thrown around, and if that was over a period of 10 years that's only 16 flights per year, which would be 8/year if divided between two providers.  That's doable with the current ULA and SpaceX production capabilities, even with other customers in the mix.  And both ULA and SpaceX have stated they can expand their production capabilities if needed.  From my manufacturing operations perspective, this is a non-issue.

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A number of payloads as well as manned Orion launches wouldn't work on a Falcon Heavy or a Vulcan.

Already the Mars proposal has elements that could fly on existing launchers, and Orion could fly on the upcoming Falcon Heavy - which is planned to be operational before the SLS is.  Obviously something like ULA's Distributed Launch concept would need to be used, but that is a launch vehicle-independent technique that is needed for expanding humanity out into space anyways, so perfecting it sooner rather than later is good.

As to other payloads, we don't really know how we're going to land large amounts of mass on Mars yet, so we don't know if 8m diameter payloads are necessary.

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The best bet is to use commercial to supplement SLS.

I would simplify that even more.  Redundancy should be a priority, meaning the loss of any launch family should not stop our progress.
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Online Endeavour_01

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Re: SLS General Discussion Thread 2
« Reply #167 on: 09/29/2015 12:28 AM »
Do we really need to up the SLS production rate beyond 2 a year?

Do we really need a space program at all?

Now, we probably don't need SLS making milk runs to the ISS.  But I see no reason why a couple of heavy lunar landers per year (perhaps developed from existing upper stage technology, so as to save money vs. Altair) should be out of scope, except that Obama's "vision" seems to have sucked all the hope out of everybody.  Add depots (with tankers), and you've freed up a couple of launches, but you still have to go past two per year if you want to do literally anything else on top of your six-month moon base rotation.  Like, say, launch scientific probes to the outer planets, or large space telescopes, or BA-330s to cislunar space, or BA-2100s to LEO, or the notional giant black payloads that have been hinted about, or, y'know...  go to Mars.  Especially every two years...

Look I am all in favor of flying 3 or 4 SLS's a year. I just wanted to point out that we don't necessarily have to increase production more than 2 per year in order to achieve certain mission plans (EMC). I keep hearing the argument, "it can only launch twice a year so lets cancel it and yada yada yada." I just wanted to counter that argument. You could do a purely cislunar mission with a lunar space station and lunar lander with a two launch per year cadence. To do Moon, Mars, and elsewhere or a combination of them you need more than 2 SLS flights per year.
I cheer for both NASA and commercial space. For SLS, Orion, Falcon 9, Falcon Heavy, Dragon, Starliner, Cygnus and all the rest!
I was blessed to see the launch of Space Shuttle Endeavour on STS-99. The launch was beyond amazing. My 8-year old mind was blown. I remember the noise and seeing the exhaust pour out of the shuttle as it lifted off. I remember staring and watching it soar while it was visible in the clear blue sky. It was one of the greatest moments of my life and I will never forget it.

Offline 93143

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Re: SLS General Discussion Thread 2
« Reply #168 on: 09/29/2015 12:58 AM »
Fair enough.  It is certainly possible to do interesting missions under the current constraints.

I'm just a bit annoyed that they've baked in such an anemic maximum, or rather that they've been forced to do so by budget pressure and lack of vision.  It seems such a waste of potential to go to all the trouble to build an HLV and then barely use it.

...well, it's better than one flight every two years, as was the projection not so long ago...
« Last Edit: 09/29/2015 01:26 AM by 93143 »

Offline MarcAlain

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Re: SLS General Discussion Thread 2
« Reply #169 on: 09/30/2015 02:29 AM »
I'd rather see a focus on landing on the Moon, practicing base building there, and developing a L2 station than trying to do a bare bones trip to Mars.

Offline sdsds

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Re: SLS General Discussion Thread 2
« Reply #170 on: 09/30/2015 04:12 AM »
I'd rather see a focus on landing on the Moon, practicing base building there, and developing a L2 station than trying to do a bare bones trip to Mars.

Take heart! Sure NASA talks of Mars, and has a plan which will, "Keep Mars in view." But look at the capabilities of the system they're building. It produces one launch a year, sometimes bursting to two. And nothing they're building today is useful solely for Mars missions. In fact "all the wood" right now is behind the proving ground "arrow."

Only once there's substantial progress on a deep space habitat will it make sense to ask, "What sort of system for transport to the surface of a planetary body comes next?" If the time comes and the budget can support these amazing Mars missions, then sure let's go for it. But more realistically, you're likely to get your wish!
-- sdsds --

Offline Hog

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Re: SLS General Discussion Thread 2
« Reply #171 on: 09/30/2015 05:20 PM »
1.  Someone said, somewhere here, that when facility to manufacture Saturn V 1st and 2nd stages were for 6 Saturn V's per year.  So, the facility can at least do 6.

2.  The VAB can process at least 4 at a time.  It has 4 bays.  They would have to build at least 4 platforms.   

 Also, there is not only one pad for SLS.
Clarification please.
Are you saying there is one pad, or more than 1 pad for SLS?
Paul

Offline Mark S

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Re: SLS General Discussion Thread 2
« Reply #172 on: 09/30/2015 08:59 PM »
1.  Someone said, somewhere here, that when facility to manufacture Saturn V 1st and 2nd stages were for 6 Saturn V's per year.  So, the facility can at least do 6.

2.  The VAB can process at least 4 at a time.  It has 4 bays.  They would have to build at least 4 platforms.   

 Also, there is not only one pad for SLS.
Clarification please.
Are you saying there is one pad, or more than 1 pad for SLS?

I'm pretty sure that Jim meant "there is now only one pad for SLS", since NASA leased pad 39A to SpaceX. The implication is that SLS cannot have a higher launch rate e.g. Shuttle because of the limitation of a single SLS launch pad 39B.

However, SLS is not Shuttle and it will have a clean pad with no FSS or RSS. So it seems to me that the limitation would be in the number MLPs, not pads. If NASA needed to launch multiple SLSes in hurry, they just need more MLPs. Roll up, hook up, launch. At least, that's the theory. :) I'm sure the reality would be a non-trivial amount of time between launches, even with a clean pad.

Mark S.

Offline spacenut

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Re: SLS General Discussion Thread 2
« Reply #173 on: 09/30/2015 09:21 PM »
So if they had two MLP's and used two bays to set up a couple of SLS's, they could what launch 1 a week?  If they had unlimited cores and boosters coming in.  So, it seems to me the bottleneck for launching more than two a year is production at McCloud facility.  Don't know about ATK production of boosters.  I understand once the steel boosters are gone, they will go to the Black Knights.  Now is seems they should have designed a clean sheet with reusable boosters and core, or at least a return pod with the engines. 

Offline Jim

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Re: SLS General Discussion Thread 2
« Reply #174 on: 09/30/2015 09:37 PM »
So if they had two MLP's and used two bays to set up a couple of SLS's, they could what launch 1 a week? 

No, booster stacking takes longer than that.  Add in upper stage and payload and VAB time is much more than Shuttle. 

Online Coastal Ron

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Re: SLS General Discussion Thread 2
« Reply #175 on: 09/30/2015 09:40 PM »
So, it seems to me the bottleneck for launching more than two a year is production at McCloud facility.

Don't fall into the trap of thinking that just improving one "bottleneck" automatically means you can launch an SLS weekly.  NASA paid their contractors to build a production system based on a limited flight rate, because NASA does not have any visibility into the true need the future flight rate.  No one does until Congress approves the allocation of money to make it happen.

What that means is that money will be needed throughout the supply chain to increase production.  How much?  We in the public don't know, but on average it should be less per unit produced than the current rate.  And likely there is an upper end where new facilities and transportation systems will be needed.

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Now is seems they should have designed a clean sheet with reusable boosters and core, or at least a return pod with the engines.

Reusable SLS 1st stage?  Are you serious?
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 Mark S

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Re: SLS General Discussion Thread 2
« Reply #176 on: 10/01/2015 02:04 PM »
So if they had two MLP's and used two bays to set up a couple of SLS's, they could what launch 1 a week? 

No, booster stacking takes longer than that.  Add in upper stage and payload and VAB time is much more than Shuttle.

Assume NASA has two high bays in the VAB for SLS stacking, and two MLPs to put them on. And it stacks two SLS vehicles complete with boosters, EUS, and payload/Orion. You now have two SLS ready to launch on their own mobile platforms sitting in the VAB, and a single clean pad to launch them from (39B).

Assuming just one CT, what would be the minimum interval of time between launching the two fully stacked and prepped SLS on the single pad 39B? My guess is certainly more than a week, but hopefully less than a month.

What would have to take place between the two launches? Clearly there would need to be a lot LH2 on hand. :) Does the LH2 tank hold enough for two launches? If not, how long would it take to top it off?

And I'm sure there's a lot of work to hook utilities, data, and piping up to the MLP once it is delivered to the clean pad.

Remember that this is just a thought exercise. Please be kind. :)

Mark S.

Offline jongoff

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Re: SLS General Discussion Thread 2
« Reply #177 on: 10/01/2015 11:04 PM »
1.  Someone said, somewhere here, that when facility to manufacture Saturn V 1st and 2nd stages were for 6 Saturn V's per year.  So, the facility can at least do 6.

2.  The VAB can process at least 4 at a time.  It has 4 bays.  They would have to build at least 4 platforms.   

1.  Not true.  Space/volume does not determine capability.  The tooling does.  Anyways, it is a shared facility and there are other users

2.  See above. The 4 bays were never fully outfitted and even during shuttle, only two were outfitted.  Also, there is not only one pad for SLS.

Also, IIRC doesn't the quantity-distance rules on the SRBs mean they are only allowed to have two SLS vehicles in the VAB at one time, or am I misremembering that detail?

~Jon
« Last Edit: 10/01/2015 11:07 PM by jongoff »

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Re: SLS General Discussion Thread 2
« Reply #178 on: 10/02/2015 03:39 PM »
I'm pretty sure that Jim meant "there is now only one pad for SLS", since NASA leased pad 39A to SpaceX. The implication is that SLS cannot have a higher launch rate e.g. Shuttle because of the limitation of a single SLS launch pad 39B.

There is one pad and one ML. Original maps of Complex 39 show locations for 5 potential pads, but it is doubtful in the extreme that any more would ever be developed. Even if they wanted to, environmental impact reviews would most surely prevent it anyway.

Offline Mark S

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Re: SLS General Discussion Thread 2
« Reply #179 on: 10/02/2015 05:47 PM »
I'm pretty sure that Jim meant "there is now only one pad for SLS", since NASA leased pad 39A to SpaceX. The implication is that SLS cannot have a higher launch rate e.g. Shuttle because of the limitation of a single SLS launch pad 39B.

There is one pad and one ML. Original maps of Complex 39 show locations for 5 potential pads, but it is doubtful in the extreme that any more would ever be developed. Even if they wanted to, environmental impact reviews would most surely prevent it anyway.

Wow, I didn't think it was that hard of a question. Or that the possibility of a second ML being built was so far out there. And I never said anything about building any more launch pads. I just wanted to know if making a clean pad was of any benefit whatsoever to possible future launch rates.

So now that we know that NASA will never build another ML or have more than one launch pad. How long will it take NASA to launch all of the SLS needed for one complete current Mars DRM mission, given one ML, one pad, and one VAB high bay. Have they gotten the number of launches below 10 yet?

Remember, we're on a Journey to Mars(TM)!!

Thanks.

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