Author Topic: SLS General Discussion Thread 2  (Read 223543 times)

Offline 93143

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Re: SLS General Discussion Thread 2
« Reply #220 on: 10/14/2015 09:06 PM »
The basic point I was trying to make was about the validity of the economic model. To say using one LV over another would be generally less total cost cannot be made, it is a specific case by case situation.

Did you read the paper or is that your opinion?  You do kinda sound like you have a source for your numbers...

I was referencing the abstract, not to prove that SLS is always better but to show that $/kg is not necessarily the more important metric as Coastal Ron suggested.

Offline oldAtlas_Eguy

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Re: SLS General Discussion Thread 2
« Reply #221 on: 10/14/2015 11:37 PM »
The basic point I was trying to make was about the validity of the economic model. To say using one LV over another would be generally less total cost cannot be made, it is a specific case by case situation.

Did you read the paper or is that your opinion?  You do kinda sound like you have a source for your numbers...

I was referencing the abstract, not to prove that SLS is always better but to show that $/kg is not necessarily the more important metric as Coastal Ron suggested.
I just created my own simplistic eco model of the problem and relationships and checked what the results were. It showed that while the $/kg difference between the two launchers is important it is not the controlling factor but the factor of total modules to unique module designs. Its another form of economies of scale. If the quantities are high enough the high costs of design for each unique design can be overcome by the high number of identical modules reducing the total cost of the system. Launch costs are actually only a portion of the total costs at most 50% or even a lot less at almost 10%. Like I said because of the multiple variables at play singling out any one variable as the definitive decider is an error. Because launch costs are an additional cost and not the most significant cost reduction of launch costs does not have as much effect as some would believe and in some cases other cost increases are greater than the cost savings using a cheaper launcher.

The only somewhat rule of thumb is if the larger launcher is also the cheaper $/kg then it may be the best solution but watch out for volume (faring space for the payload) may be a limiting item on the larger LV making a smaller booster that also has a large volume to payload weight possibly a better value.

Offline Coastal Ron

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Re: SLS General Discussion Thread 2
« Reply #222 on: 10/15/2015 12:35 AM »
I just created my own simplistic eco model of the problem and relationships and checked what the results were. It showed that while the $/kg difference between the two launchers is important it is not the controlling factor but the factor of total modules to unique module designs.

This assumes the construction method is based on assembling modules, and that may not be the ultimate design, or at least not a majority of the ultimate design.  For instance, with a rotating space station quite a bit of the total mass will likely be taken up by supports and floors and such, not living space, and those would likely be more mass dense than living space modules would be (with no real designs, "likely" is the operative word).

However, this discussion about rotating space stations is really premature, since based on my calculations the mass of such stations, even if they are only .5G or so, would be far, far bigger than the mass of the ISS, which is 450mT.  And I don't see any funded need for such a structure in the near future.
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 oldAtlas_Eguy

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Re: SLS General Discussion Thread 2
« Reply #223 on: 10/15/2015 02:35 PM »
I just created my own simplistic eco model of the problem and relationships and checked what the results were. It showed that while the $/kg difference between the two launchers is important it is not the controlling factor but the factor of total modules to unique module designs.

This assumes the construction method is based on assembling modules, and that may not be the ultimate design, or at least not a majority of the ultimate design.  For instance, with a rotating space station quite a bit of the total mass will likely be taken up by supports and floors and such, not living space, and those would likely be more mass dense than living space modules would be (with no real designs, "likely" is the operative word).

However, this discussion about rotating space stations is really premature, since based on my calculations the mass of such stations, even if they are only .5G or so, would be far, far bigger than the mass of the ISS, which is 450mT.  And I don't see any funded need for such a structure in the near future.
Actually the eco module applies to even a single large unit flown on SLS where it takes 3 unique units flown on FHR. But if it was 3 identical units flown on SLS and then 3 flights each of 3 unique units on FHR there may be a cost savings using FHR over that of SLS. Like I said it is a case by case economic analysis problem to determine which will be cheaper due to the added costs of designing multiple units vs a single larger unit. It is that last that is the economic problem. If the larger unit can be substituted by using say 3 identical smaller units then SLS losses hands down in total costs for the system (Launch + unit development+unit manufacturing+on orbit assembly(if needed)). This problem is basically due to the high cost of development vs the cost of manufacture once the design has been done. This ratio is usually somewhere around 5 (development/design to manufacturing). This means that quantity and cost of launch are related to total system costs. High quantity and smaller lower launch costs will equal lower total system costs but exactly where this crossover point is for any given unit is a function of the costs for the unit (design and manufacturing + the number of launches at a launch cost for a specific booster).

Here Unit = a unique payload of some kind

Offline A_M_Swallow

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Re: SLS General Discussion Thread 2
« Reply #224 on: 10/21/2015 08:17 PM »
Quote
The L point station should also be modular enough to have replacements periodically for continuous operations.  It should also be able to expand into a fuel depot for Mars transits, and a warehouse type depot for Mars cargo departures.

Using Earth analogies, we don't combine hotels with gas stations, for a number of reasons, but even in space I'm not sure there would be enough synergy or need to combine them.

Since it is for short stay and for work rather than play the spacestation would be more a motel than hotel.

In Britain motels and petrol stations are combined - they are called motorway service stations. I do accept the food & bedrooms are low quality and the fuel is expensive. Different buildings but on the same campus.
« Last Edit: 10/21/2015 08:19 PM by A_M_Swallow »

Offline rayleighscatter

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Re: SLS General Discussion Thread 2
« Reply #225 on: 10/22/2015 10:32 PM »
So since the adapter/interstage is shown as being foam covered as well as the core would the two likely be joined before foam is applied or can the foam be applied to both and then connect the two parts?

Offline Mark S

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Re: SLS General Discussion Thread 2
« Reply #226 on: 10/23/2015 03:49 AM »
So since the adapter/interstage is shown as being foam covered as well as the core would the two likely be joined before foam is applied or can the foam be applied to both and then connect the two parts?

I don't think the adapter is foam covered. It's just painted orange to match the tanks for some reason. It has to be painted, so why not orange (other than flying carrot jokes)?

But in my opinion, it should be white. The tanks are only orange because that's the natural color of the foam insulation, and they don't want to paint it, in order to save weight. Not because orange is the cool color now. Or ever, in spite of OITNB.

Mark S.

Offline ISP

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Re: SLS General Discussion Thread 2
« Reply #227 on: 10/23/2015 05:39 AM »
So since the adapter/interstage is shown as being foam covered as well as the core would the two likely be joined before foam is applied or can the foam be applied to both and then connect the two parts?

I don't think the adapter is foam covered. It's just painted orange to match the tanks for some reason. It has to be painted, so why not orange (other than flying carrot jokes)?

But in my opinion, it should be white. The tanks are only orange because that's the natural color of the foam insulation, and they don't want to paint it, in order to save weight. Not because orange is the cool color now. Or ever, in spite of OITNB.

Mark S.

The LVSA is covered in foam now. Not sure why, but it is, per this:

http://www.nasa.gov/press-release/nasa-completes-critical-design-review-for-space-launch-system

Quote
Critical design reviews for the individual SLS elements of the core stage, boosters and engines were completed successfully as part of this milestone. Also as part of the CDR, the program concluded the core stage of the rocket and Launch Vehicle Stage Adapter will remain orange, the natural color of the insulation that will cover those elements, instead of painted white.

Offline sdsds

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Re: SLS General Discussion Thread 2
« Reply #228 on: 10/23/2015 05:50 AM »
Given the anticipated production rate why not paint each LVSA with a unique color pattern, so in photos of the vehicles it will always be easy to identify them? Or maybe to get that retro "Jupiter" look they seem to love they could paint on the vehicle's serial number in big black letters using H-U-N-T-S-V-I-L-E-X code?
-- sdsds --

Offline Proponent

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Re: SLS General Discussion Thread 2
« Reply #229 on: 10/23/2015 09:11 AM »
As an aside, the image above is likely reversed, the actual designation being AMXHA.

EDIT:  Corrected link.
« Last Edit: 10/24/2015 02:04 PM by Proponent »

Offline Mark S

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Re: SLS General Discussion Thread 2
« Reply #230 on: 10/23/2015 06:04 PM »
So since the adapter/interstage is shown as being foam covered as well as the core would the two likely be joined before foam is applied or can the foam be applied to both and then connect the two parts?

I don't think the adapter is foam covered. It's just painted orange to match the tanks for some reason. It has to be painted, so why not orange (other than flying carrot jokes)?

But in my opinion, it should be white. The tanks are only orange because that's the natural color of the foam insulation, and they don't want to paint it, in order to save weight. Not because orange is the cool color now. Or ever, in spite of OITNB.

Mark S.

The LVSA is covered in foam now. Not sure why, but it is, per this:

http://www.nasa.gov/press-release/nasa-completes-critical-design-review-for-space-launch-system

Quote
Critical design reviews for the individual SLS elements of the core stage, boosters and engines were completed successfully as part of this milestone. Also as part of the CDR, the program concluded the core stage of the rocket and Launch Vehicle Stage Adapter will remain orange, the natural color of the insulation that will cover those elements, instead of painted white.

Thanks for the correction! I missed that.

Like you, I have no idea why they would put foam on the LVSA. Does anyone else have any insight on that decision?

Mark S.

Offline TomH

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Re: SLS General Discussion Thread 2
« Reply #231 on: 10/26/2015 09:20 PM »
I have no idea why they would put foam on the LVSA. Does anyone else have any insight on that decision?

The answer is in Chris' and Chris's new article.

Quote
The post-CDR design does include more foam on the top end of the rocket after an additional decision included a call for the LVSA (Launch Vehicle to Stage Adaptor) to have foam on the outside, based on the latest thermal analysis.

Given the LVSA has the core stage LOX tank below it, the ICPS LOX tank inside, and the ICPS LH2 tank above it, it is expected this area of the rocket will become cold during the final countdown and form ice on the outside.
« Last Edit: 10/26/2015 09:24 PM by TomH »

Offline TomH

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Re: SLS General Discussion Thread 2
« Reply #232 on: 10/26/2015 09:23 PM »
And from today's new article:

Quote
Presently, SLS Near-Term Look-Ahead schedules show that the VAC will be turned over from the construction contractor ESAB to Boeing at the end of this week on 31 October.

Delivery on Halloween Day, hope this doesn't turn out to be a Trick or Treat? delivery.

Offline dror

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Re: SLS General Discussion Thread 2
« Reply #233 on: 10/27/2015 05:38 PM »
Quote
... because for every pound of paint applied, a pound of payload delivery ability would have been removed from SLSís capability.

Is that correct ?
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Online notsorandom

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Re: SLS General Discussion Thread 2
« Reply #234 on: 10/27/2015 06:12 PM »
Quote
... because for every pound of paint applied, a pound of payload delivery ability would have been removed from SLSís capability.

Is that correct ?
It is close to correct. Mass saved from the last rocket stage of any rocket will be close to the amount of extra payload mass. In the case where it has no upper stage the core is the last stage so not painting will add payload mass roughly equal to the mass of the unused paint. However SLS will also fly with the ICPS and EUS upper stages. So when flying in those configurations the mass savings in paint will increase payload but not at a near 1:1 ratio. It will still add a bit of payload mass though since the core is jettisoned late in flight. That paint needs to be hauled through a good amount of the imparted delta V.

Online BrightLight

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Re: SLS General Discussion Thread 2
« Reply #235 on: 10/28/2015 05:27 PM »
With the CDR for the SLS core passed as well as the Orion EM-2 in process - I'm getting to the point I believe SLS will actually fly!


Offline rayleighscatter

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Re: SLS General Discussion Thread 2
« Reply #236 on: 11/10/2015 01:49 AM »


Like you, I have no idea why they would put foam on the LVSA. Does anyone else have any insight on that decision?

Mark S.
From a NASA blog post today, for what it's worth:
Quote
Also insulated with the orange foam is the Launch Vehicle Stage Adapter, the conical section that connects the core stage with the upper stage. Because this section widens so much from top to bottom, it will experience extreme aerodynamic heating during launch, and the foam will protect the metal underneath from the high temperatures.

Offline llanitedave

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Re: SLS General Discussion Thread 2
« Reply #237 on: 11/10/2015 03:51 PM »
That's interesting.  I wonder what makes launch heating on the SLS adapter more problematic than it would have been on the Saturn V second-third stage adapter.
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Offline Proponent

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Re: SLS General Discussion Thread 2
« Reply #238 on: 11/10/2015 03:59 PM »
Maybe the use of SRBs increases aero heating?

Offline Starlab90

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Re: SLS General Discussion Thread 2
« Reply #239 on: 11/11/2015 12:08 AM »
That's interesting.  I wonder what makes launch heating on the SLS adapter more problematic than it would have been on the Saturn V second-third stage adapter.

I'm pretty sure it's because SLS will have a higher max Q than the Saturn V did, but I need to double-check the numbers.

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