Author Topic: Reusability effect on costs  (Read 131921 times)

Offline john smith 19

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Re: Reusability effect on costs
« Reply #620 on: 09/01/2017 02:54 PM »
I expect refurb after each ten, retirement after 100.
Both Shotwell and Musk have been very quiet on refurb procedures. SX spent a very long time getting the first couple of boosters ready for re-flight. I'm not sure they actually have any refurb procedures worked out for this generation, although I'm sure they learned all (nearly all?) they need to ensure the next generation can be done fairly straightforwardly.

Quote from: JamesH65
No-one (except SpaceX) has ANY idea of the refurb costs after each ten flights.
True, and that represents a significant (but difficult to value) piece of IP for SX. Although I suspect the technicians involved could give a fair guestimate.

Quote from: JamesH65
Forgive another car analogy, but I'd expect the refurb to be on the order of a new set of brake pads. Not an every day occurrence, but certainly not a transmission rebuild which is often not cost effective.
I suspect more like what happens if there are a dozen brake pads and they are all glued in and you have to scrape them off before re-gluing the new set.  :(

Time will tell if the current, or the next, or the next, or the next generation of F9 will deliver that 100 reuse target. If the current hardware can already deliver it I'd expected a much more positive presentation by now.

"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Online oldAtlas_Eguy

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Re: Reusability effect on costs
« Reply #621 on: 09/01/2017 08:12 PM »
Their long-term aim is at least 100 reflights of each booster core, and I heard this directly from the SpaceX VP of business development at the CRS-8 launch viewing on the OMB-II verandah.
Well so far they Shotwell on the Space Show said they are looking to do 3 launches off a booster and V5 will be good for 10 without major

So either V5 will do that with a lot of refurb work above "inspection" or they are at least another generation to go from 10 to 100.  :(

I expect refurb after each ten, retirement after 100. No-one (except SpaceX) has ANY idea of the refurb costs after each ten flights. Forgive another car analogy, but I'd expect the refurb to be on the order of a new set of brake pads. Not an every day occurrence, but certainly not a transmission rebuild which is often not cost effective.
Going with the brake pad analogy the items that are the ones receiving the most degradation from use are the engines, grid fins, and landing legs. I would expect significant replacement (re-manufacturing) of these parts. Basically replace all the engines, the grid fins and legs. Send them off for evaluation to determine if they can be individually refurbished or just cheaper to scrap. The then refurbished stage has new or like new engines, grid fins and legs. The other item the tank and avionics are such that failed avionics are replaced as needed regardless of what the flight number. The tank if down checked, then the stage is basically scrapped by removing all the usable parts putting them back into inventory. That can also happen at anytime or even the stage (tank) could fly more than 100 times. The real nature of re-flying tanks multiple times is not well known (except for the the two flights is almost completely unknown).

There is just a lot of unknowns.
Info is such that F9 can reliably do at least 2 flights. The refurb time from info on last re-flight was 2 months with new info that should be forthcoming on the next that give light of whether the time and manpower/ related costs are leveled out or continue to decline.
This then represents that the cost/flight for the 1st stage is currently at ~60% of the manufacturing cost of a new stage. Once stages fly 3 times that could lower to ~35%. At 5 times <25%. At 10 times <15%. At 20 times <10% (including extensive refurbish work at 10 flights). Past 20 flights there will not be much lowering of the costs. Just the logistical availability of stages to support higher flight rates

Offline john smith 19

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Re: Reusability effect on costs
« Reply #622 on: 09/02/2017 09:57 AM »
Going with the brake pad analogy the items that are the ones receiving the most degradation from use are the engines, grid fins, and landing legs. I would expect significant replacement (re-manufacturing) of these parts. Basically replace all the engines, the grid fins and legs. Send them off for evaluation to determine if they can be individually refurbished or just cheaper to scrap. The then refurbished stage has new or like new engines, grid fins and legs. The other item the tank and avionics are such that failed avionics are replaced as needed regardless of what the flight number. The tank if down checked, then the stage is basically scrapped by removing all the usable parts putting them back into inventory. That can also happen at anytime or even the stage (tank) could fly more than 100 times. The real nature of re-flying tanks multiple times is not well known (except for the the two flights is almost completely unknown).
That sounds about right. One thing you may not have factored in is how much data the avionics can collect. In aircraft the addition of maintenance data recorders, capturing many more channels than the crash rated "black boxes," shifted the whole basis of maintenance from scheduled to "when necessary" or "when predicted" once data patterns showing impending faults started to be recognized.

I think the subtle point is in recognizing which sensors you can afford to remove from the stage because they are not improving your ability to predict its reliability and are therefor redundant excess mass.

I'd expect SX have done a lot of work on this. I presume they continuously monitor the stage till it lands but I don't think this has near the bandwidth to transmit in real time all the data they are collecting.

Little by little they should be building a minimal list of sensors (above what are already needed) that predict stage and engine health with high accuracy, although I suspect this is still a "work in progress,"  and will continue to be for some time.

Quote from: oldAtlas_Eguy
There is just a lot of unknowns.
Info is such that F9 can reliably do at least 2 flights. The refurb time from info on last re-flight was 2 months with new info that should be forthcoming on the next that give light of whether the time and manpower/ related costs are leveled out or continue to decline.
True, and SX is currently the only company in the world with any actual data on what the real issues are, in the same way that Air France and British Airways were the only airlines that acquired actual data on what it takes to really operate a large M2.2 passenger aircraft over decades.

It's difficult to put a price on the data, but it's very hard to acquire.

I think you're spot on with replacing what can be replaced or if the structure is gone then salvaging everything that can for refurbishment and reinstallation on the next one.

My instinct with refurbishment is the problem areas are the ones you can't easily remove. The structure itself and any TPS tha's been directly bonded to it.

Ideally SX have identified the main areas of TPS erosion. The really simple answer is "let it happen." IOW put on enough to survive X flights and when it's too eroded the stage is scrapped.
Option 2 is put it on removable panels. Literally like a brake pad.

But that adds weight and they may be in awkward corners. Historically the X-15 programme did some tests with repairing the spray-on ablator they used for some of the higher speed flights (M6.15 IIRC). Rather than strip right back to the bare metal they were able to strip to virgin ablator and roughen the surface well enough that a fresh layer would key into it and bond well, but the ablator was a PITA to use.  :(

Today, given all the geometry is in a big CAD model, I'd guess some kind of machine with one or more router heads and sensors to scan the surface, find the damage layer depth and machine it off, or all the way down to the metal.

The other biggie has got to be the structure, especially what the landing does to it. 
In principal all landings (sea or land, calm sea or rough weather) are the same , but IRL that's simply not true. The legs can only damp so much of the loads and over time some members of the "fleet" (of boosters) will have had an easier time of it than others.

AFAIK outside of SX I don't think anyone has any idea of what that does to the structural integrity of the stage. I'm pretty sure that a barge landing is even worse than a combat aircraft landing on a carrier.

I don't know of any other situation where people slam large partially filled light weight tanks (at quite high speed) into a fixed stop.
I have a dim recollection (from Clarkes "Ignition" ?) about a suspected slosh induced explosion which was simulated by using an instrumented,  partly loaded tanker car and driving it into a set of buffers.  Full tanks were no problem, but the partly filled ones had the liquid compress the vapour to ignition point. The air in the car did the rest.
LOX and RP1 are much more tolerant of such behavior, but I don't think anyone really checked what happens to the tanks.  :(

personally I'd also love to know what happens to the engines.

The gas generator normally runs highly fuel rich to keep the temperatures down and pictures I've seen of old GG rocket engines suggest it's pretty smoky. OK for a few test firings and then one shot use but what does that do to the turbine blades over many test and operating runs? Pretty much what a car with an oil leak into the  cylinders does to the pistons?
AFAIK SOP is LRE turbine blades are uncooled, but all big gas turbine blades are cooled, certainly anything as high a thrust as a Merlin would be. This is legacy of the missile/ICBM design process.  My instinct is cool the blades and run leaner with less fouling.

The other big (potential) issue with the engines is the fuel baking onto the insides of the cooling channels, sapping power (the pumps have to work harder as the channels are narrower) and cutting heat flow from the inside surface of the combustion chamber, potentially leading to catastrophic failure when there's a burn through.
RP1 was partly developed to counter this (let's hear it for the worlds first Low Sulfur kerosene  :) ) and I think there have been programmes to develop cleaning procedures to deal with this but I suspect they are a PITA to apply.  :(
As per the thread title unless this is automated that's likely to burn a lot of technician time, raising costs.

If  you're not using LH2 but you do want reusability I find it very hard to understand why you would not use LOX cooling. AFAIK all other LRE's use the oxidizer for the cooling, some of which are very nasty.
Both Rotary Rocket and NASA ran LOX cooling tests in the early 90's, without mishap, including deliberate leaks into the CC, but the folklore around this subject is very tenacious and the facts difficult to get hold of.  :(
BTW thanks for that figure of $500/day for staff costs.
With fairing reuse on the verge of happening it might time for a new version of my cost modelling game.
« Last Edit: 09/02/2017 09:59 AM by john smith 19 »
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline Krankenhausen

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Re: Reusability effect on costs
« Reply #623 on: 09/07/2017 10:35 AM »
If  you're not using LH2 but you do want reusability I find it very hard to understand why you would not use LOX cooling. AFAIK all other LRE's use the oxidizer for the cooling, some of which are very nasty.
Both Rotary Rocket and NASA ran LOX cooling tests in the early 90's, without mishap, including deliberate leaks into the CC, but the folklore around this subject is very tenacious and the facts difficult to get hold of.  :(
BTW thanks for that figure of $500/day for staff costs.
With fairing reuse on the verge of happening it might time for a new version of my cost modelling game.

Quite interesting post. But isn't the lack of use of LOX cooling quite easily explained if you take into consideration that the Merlin engine was designed by a start-up and that it is also designed to be affordable in expendable mode. If you look at it that way LOX cooling would have added significant development risk. Furthermore the Raptor engine uses Methane which does not have the disadvantages of RP-1. Methane should contain (almost) no sulfer and deposit much less carbon.

And how does LOX cooling affect TWR?

Edit: Fixed broken quote
« Last Edit: 09/07/2017 04:35 PM by Krankenhausen »

Offline livingjw

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Re: Reusability effect on costs
« Reply #624 on: 09/08/2017 12:47 AM »
The norm for LREs is to use the fuel for cooling the CC, not LOX.

John

Offline john smith 19

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Re: Reusability effect on costs
« Reply #625 on: 09/08/2017 04:34 PM »
The norm for LREs is to use the fuel for cooling the CC, not LOX.

John
When I posted
Quote
AFAIK all other LRE's use the oxidizer for the cooling, some of which are very nasty.
I meant all other LRE's that do not use LOX as an oxidizer.
AFAIK all stages of the Titan used NTO (the oxidizer) for chamber cooling. The Russians did the same for their ICBMS I think. The British used HTP for the Gamma rocket engines on Black Arrow.


My apologies for not being clearer
« Last Edit: 09/09/2017 12:38 PM by john smith 19 »
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline john smith 19

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Re: Reusability effect on costs
« Reply #626 on: 09/08/2017 04:55 PM »
If  you're not using LH2 but you do want reusability I find it very hard to understand why you would not use LOX cooling. AFAIK all other LRE's use the oxidizer for the cooling, some of which are very nasty.
Both Rotary Rocket and NASA ran LOX cooling tests in the early 90's, without mishap, including deliberate leaks into the CC, but the folklore around this subject is very tenacious and the facts difficult to get hold of.  :(
BTW thanks for that figure of $500/day for staff costs.
With fairing reuse on the verge of happening it might time for a new version of my cost modelling game.
Quite interesting post. But isn't the lack of use of LOX cooling quite easily explained if you take into consideration that the Merlin engine was designed by a start-up and that it is also designed to be affordable in expendable mode.
In fact the first Merlin was ablatively cooled. Which is an even odder choice for a design if you're planning to make reusable, which has always been Musks goal.  :(

Quote from: Krankenhausen
If you look at it that way LOX cooling would have added significant development risk.
It certainly would have added significant fear of a development risk.  :(
Quote from: Krankenhausen
Furthermore the Raptor engine uses Methane which does not have the disadvantages of RP-1. Methane should contain (almost) no sulfer and deposit much less carbon.
I guess that will depend on where they source it from and wheather it's doses with Mercaptans to give a clearly detectable odor, and how well they remove it.

Carbon can be a remarkably temperature resistant element. Metal balls with a thin carbon film hung from a wire survived a nuclear explosion by the carbon being ablated by the blast (it was an early test of the theory behind the "Orion" nuclear explosion powered space ship). 

Carbons thermal conductivity can also vary substantially between through and across crystal layers, something like 3:1 IIRC. So combustion heat goes through the metal wall and spreads out through the layer of carbon deposited in a cooling channel, rather than into the Methane. Time will tell how big a problem that turns out to be.
Quote from: Krankenhausen
And how does LOX cooling affect TWR?

Edit: Fixed broken quote
Ask HMX. His company built a test engine to do this.  :)

However slightly more helpfully.
Obvious parameters are:
Density and change of density with temperature
SHC and change of SHC with temperature
Viscosity and change of viscosity with temperature  and cooling channel layout.

A study during the SSME program found a revised cooling channel layout could cut pump power (for the same wall temperature) by about 50%, needing less gas flow to drive the pump or (for an SC design) causing less obstruction to the flow into the Main Combustion Chamber (US terminology) or "afterburner" (Russian usage).

Personally when I looked at the MCC of the SSME I thought "That is the mother of all afterburners," but that is not common US usage. :)
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Online Robotbeat

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Re: Reusability effect on costs
« Reply #627 on: 09/09/2017 04:09 AM »
 :) :) :) :) :)
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Offline tdperk

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Re: Reusability effect on costs
« Reply #628 on: 09/11/2017 12:07 AM »
If  you're not using LH2 but you do want reusability I find it very hard to understand why you would not use LOX cooling. AFAIK all other LRE's use the oxidizer for the cooling, some of which are very nasty.
Both Rotary Rocket and NASA ran LOX cooling tests in the early 90's, without mishap, including deliberate leaks into the CC, but the folklore around this subject is very tenacious and the facts difficult to get hold of.  :(
BTW thanks for that figure of $500/day for staff costs.
With fairing reuse on the verge of happening it might time for a new version of my cost modelling game.
Quite interesting post. But isn't the lack of use of LOX cooling quite easily explained if you take into consideration that the Merlin engine was designed by a start-up and that it is also designed to be affordable in expendable mode.
In fact the first Merlin was ablatively cooled. Which is an even odder choice for a design if you're planning to make reusable, which has always been Musks goal.  :(

I think not in light of the fact his overarching goal is to lower space access costs until he can settle Mars/make humanity a multi-planet species.

He was at the point he needed launch history to inform the lean decision making tree, and possibly needed assurance of success towards future income.  So he launched with what was ready.

As long as you are alive, improvement can come later.
« Last Edit: 09/11/2017 12:08 AM by tdperk »

Offline AncientU

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Re: Reusability effect on costs
« Reply #629 on: 09/11/2017 12:14 AM »
His first goal was to lower the cost of access to space.

His zeroth goal was go get to space...

Pragmatism is his mantra.
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Offline speedevil

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Re: Reusability effect on costs
« Reply #630 on: 09/14/2017 12:56 PM »
https://twitter.com/elonmusk/status/908254079092002816
Quote
Long road to reusabity of Falcon 9 primary boost stage…When upper stage & fairing also reusable, costs will drop by a factor >100.

This seems considerably more certain than prior pronouncements.
And clearly means that upper/lower/fairing each can't have >100K spent on them to refurb and get back to the launch site. (counting fuel)


Offline AncientU

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Re: Reusability effect on costs
« Reply #631 on: 09/14/2017 02:54 PM »
https://twitter.com/elonmusk/status/908254079092002816
Quote
Long road to reusabity of Falcon 9 primary boost stage…When upper stage & fairing also reusable, costs will drop by a factor >100.

This seems considerably more certain than prior pronouncements.
And clearly means that upper/lower/fairing each can't have >100K spent on them to refurb and get back to the launch site. (counting fuel)

Yup... when, not if.
"If we shared everything [we are working on] people would think we are insane!"
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Offline john smith 19

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Re: Reusability effect on costs
« Reply #632 on: 09/16/2017 09:14 AM »
https://twitter.com/elonmusk/status/908254079092002816
Quote
Long road to reusabity of Falcon 9 primary boost stage…When upper stage & fairing also reusable, costs will drop by a factor >100.

This seems considerably more certain than prior pronouncements.
And clearly means that upper/lower/fairing each can't have >100K spent on them to refurb and get back to the launch site. (counting fuel)
It's a truism of launch vehicle economics.

If I were guessing I'd say the team have a firmer handle on the physics of US reentry and they are ready to give it a serious try. But we've been here before. Let's see how they handle the 26x bigger energy dissipation problem that orbital entry has over booster recovery.
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline livingjw

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Re: Reusability effect on costs
« Reply #633 on: 09/16/2017 05:13 PM »
https://twitter.com/elonmusk/status/908254079092002816
Quote
Long road to reusabity of Falcon 9 primary boost stage…When upper stage & fairing also reusable, costs will drop by a factor >100.

This seems considerably more certain than prior pronouncements.
And clearly means that upper/lower/fairing each can't have >100K spent on them to refurb and get back to the launch site. (counting fuel)

It's a truism of launch vehicle economics.

If I were guessing I'd say the team have a firmer handle on the physics of US reentry and they are ready to give it a serious try. But we've been here before. Let's see how they handle the 26x bigger energy dissipation problem that orbital entry has over booster recovery.

Same way the Space Shuttle, Buran, X-37B and Dream Chaser does it, with some type of reusable TPS. Its not like we haven't done this before. It is different in that it is more of lifting body (smaller aero-surfaces).

John

Online Robotbeat

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Re: Reusability effect on costs
« Reply #634 on: 09/16/2017 06:12 PM »
And Dragon.
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Online oldAtlas_Eguy

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Re: Reusability effect on costs
« Reply #635 on: 09/16/2017 06:16 PM »
And Dragon.
Yes all reentry vehicles past and present have been lifting bodies of various shapes. The near future ones will continue with tryout of new shapes and new TPS. Looking for that combination that enables good payload capability and lower costs/launch.

Offline Semmel

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Re: Reusability effect on costs
« Reply #636 on: 09/16/2017 07:49 PM »
I also dont see the problem in the heat shield material. There is not much magic involved. What has not been done before is: A second stage with 7000+ m/s dV that has a shape and structural strength which allows it to reenter. When you compare all reentry vehicles done so far, all of them were relatively compact structures with aerodynamic shape optimized for reentry. The F9 second stage is neither rigid nor compact. I dont believe that just slamming some TPS on the outside would work. I think S2 would have to be completely redesigned. Basically what SpaceX does (presumably) with ITSy.

Offline john smith 19

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Re: Reusability effect on costs
« Reply #637 on: 09/16/2017 09:28 PM »
Same way the Space Shuttle, Buran, X-37B and Dream Chaser does it, with some type of reusable TPS. Its not like we haven't done this before. It is different in that it is more of lifting body (smaller aero-surfaces).
All of which have several things in common.

They were all designed to reenter. No US has ever been designed that way.

Their payload to structure ratio is much lower. Suttle was 20% payload, 80% structure. This makes them much stiffer than the US, which is what 3-5% structure?

Because of their VTOHL they are all strong in 2 main axes, which partly explains their weight.

All are glide landings. None have significant propellant on board, so no major slosh issues.

Only DC is an actual lifting body, the other have defined wings. All are "lifting" reentries, as is Dragon.

It comes down to this. All the other designs have very much lower ballistic coefficients (or wing loading as it's usually called when things have wings). All the other designs executed (or will execute for DC) high angles of attack entries to lose speed. This has never been a design case for any US, which would probably crumple like an empty soda can that's been slapped on the side. Between minimal changes to the stage to make it survive those side loads, understanding and controlling those propellant slosh loads and generally coping with a PE and KE load 26x bigger than the equivalent for booster stage it's not surprising that SX have not been able to make this work yet.

However ultimately this is OT for the thread title. 

Yes reusability will lower costs, as always with the caveat that the  refurb costs are not too high.  If a US costs around $15-17m reusing it twice means it costs SX $7.5-8.5m. For n reuses the cost is roughly 1/n +nX, where X is the refurb cost.

The question is how much of those cost reductions will appear as price reductions to SX customers. 



 
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline guckyfan

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Re: Reusability effect on costs
« Reply #638 on: 09/16/2017 09:52 PM »
The second stage can be pressurized which gives cheap rigidity. The Shuttle and the capsules don't have that option.

Offline livingjw

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Re: Reusability effect on costs
« Reply #639 on: 09/16/2017 11:48 PM »
Wingless reentry vehicle designs exist, including quite large and long ones. Slosh baffles exist. Pressurized tanks are rigid. Payload bay with doors will be a little heavier than F9's carbon composite inter-stage. Windward TPS will weigh no more than 10 kg/m^2. SuperDracos exist for landing. Lots of work, but nothing way out. I have attached a Russian reusable vehicle similar in shape to what we might expect for a reusable S2. This is not that different from BFS.

John
« Last Edit: 09/16/2017 11:54 PM by livingjw »

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