Author Topic: SLS General Discussion Thread 2  (Read 223541 times)

Offline Jim

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Re: SLS General Discussion Thread 2
« Reply #200 on: 10/03/2015 12:02 PM »
NASA has stated they won't build another LEO space station.

I agree that powerful people (including I think NASA Administrator Charlie Bolden) say that, and it reflects the view of the President of the United States. But in 2020 I do not believe Charlie Bolden will be NASA Administrator, and I am 100% certain President Obama will no longer occupy the Oval Office!

It reflects the view of many at NASA

Offline MP99

Re: SLS General Discussion Thread 2
« Reply #201 on: 10/03/2015 01:33 PM »
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

Somewhere on L2 there was nice overview of the VAB facility and the maximum number of SRB segments allowed in there. I thought it was 10 segments total.

Ok, so I'm not misremembering things. So that would prevent having more than two SLS's in the building at any given time. One of the joys of big SRBs...

~Jon

Each SLS is 10 segments. ;-)

Cheers, Martin

PS am I wrong in vaguely remembering 16 segments (two complete Shuttles) back in the day?

Offline Coastal Ron

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Re: SLS General Discussion Thread 2
« Reply #202 on: 10/03/2015 02:57 PM »
EDIT:  After double-checking a bit, it seems my memory was correct; from what we know, BA-2100 is not close to being light enough for the 53-tonne Falcon Heavy to lift it.  Some sort of upgrade would be required.

Well talk with Bigelow about that, but if the moniker "BA-2100" is what bothers you, change the name to BA-2000, or BA-1782.  Remember it doesn't have a firm requirement - it's notional.
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 oldAtlas_Eguy

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Re: SLS General Discussion Thread 2
« Reply #203 on: 10/03/2015 03:51 PM »
EDIT:  After double-checking a bit, it seems my memory was correct; from what we know, BA-2100 is not close to being light enough for the 53-tonne Falcon Heavy to lift it.  Some sort of upgrade would be required.

Well talk with Bigelow about that, but if the moniker "BA-2100" is what bothers you, change the name to BA-2000, or BA-1782.  Remember it doesn't have a firm requirement - it's notional.
It is speculated that by 2024 SpaceX would have its BFR flying but maybe not the MCT so they could use that vehicle with an interim expendable US to launch SLS sized cargo (15m diameter and 100mt+ weight payloads).

But a BA-2100 may not be what NASA may use for a second generation station. NASA likes proven tech for use with HSF. BA-330s would have collected a few years of operational experience by then so a station based on 3 or 6 of those would be sufficient. If they pack them with equipment and only have 3 crew for each module a 6 BA-330 station would be a crew size of 18 three times the current crew size. That would equate to 12 cargo flights per year and 8 crew flights (3-6 crew each flight) to service the station. US budget per year in cargo and crew = $1.5B + $1.2B for the module(lease or operational support and other NASA operational costs) for a total yearly budget of $2.7B. NASA could not afford anything bigger. Using the CRS and CC capabilities that would be available at the end of life of the ISS in 2024.

There are many options other than using the SLS for a follow on commercial ISS that do not require either the SLS or anything other than existing or close to existing vehicles (CC and FH in 2 years or less [2017], SLS could be considered in this list since first flight is only a year latter in 2018).

Online notsorandom

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Re: SLS General Discussion Thread 2
« Reply #204 on: 10/03/2015 07:38 PM »
Feeling a bit sensitive today? Where did all that come from?

Ha! You should have seen my post before I self-censored it. LOL.

So, now the consensus is that there will only be one ML, thus the minimum time between SLS launches will be however long it takes to stack one up in the VAB. Does anyone have an idea about how long that may be?

Which then brings us back to the Mars mission proposals mentioned in the recent article, as Khadgars kindly pointed out. One proposal has two SLS launches of equipment to Mars in 2034, 2035, and 2036. (Five landers and the EOI stage.)

I'm no orbital expert, but I thought that Mars missions were normally spaced out every two years due to the relationship between Earth's and Mars' orbits. Is it possible to launch large payloads to Mars in the "off" years?

And, going back to the minimum time between SLS launches, how large is the launch window for Mars missions in the "on" years? Is it possible that a delay in the stacking of the second SLS in a sequence would cause it to miss the launch window?

Thanks.
You are correct that the window opens every two years. There can be up to a few months where a launch can make use of it. However we are likely to see any Mars bound depart from LDRO or L2. Over the previous two years the hardware would have been positioned there and assembled. The last launch necessary would likely be the crew. A couple weeks margin could be included in making the Mars window by having the crew launch before the craft needed to leave for Mars. SEP could open the window up a bit more too. Srubs will happen but the planners will account for that and draw the schedules up so that things are not so rushed before the window closes.

Offline sdsds

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Re: SLS General Discussion Thread 2
« Reply #205 on: 10/03/2015 09:11 PM »
NASA has stated they won't build another LEO space station.

I agree that powerful people [...] say that

It reflects the view of many at NASA

I believe that. Let's assume it reflects the views of every technically astute person at NASA. That still tells us almost nothing about the views of the powerful decision makers. ;)

(Note: I don't want NASA to invest in another LEO station. Like so many others I want a cis-lunar station. But I try not to confuse what I want with what I think is likely!)

As regards space stations, like with launch systems, NASA will comply with a law passed by Congress and signed by the President. Those decision makers consider things like the actions of other space agencies. With high probability, Russia will continuously keep a cosmonaut in space after ISS is decommissioned. Congress will want an astronaut to be continuously  in space as well. But nothing supporting that goal will be accomplished until it is almost too late. Then Boeing will offer to use SLS infrastructure at Michoud to manufacture a Skylab II. For those lobbyists, it's going to be almost a "slam dunk."

(Again note: If a United States based commercial station were already operating in LEO, we can hope NASA would use that to house its astronauts. Again though, let's avoid confusing our hopes with our predictions.)

It is speculated that by 2024 SpaceX would have its BFR flying but maybe not the MCT so they could use that vehicle with an interim expendable US to launch SLS sized cargo (15m diameter and 100mt+ weight payloads).

It's all speculation, but I doubt it helps predict the future to discuss an interim upper stage that hasn't been mentioned by the company claiming it will one day make the boost stage! A Bigelow station launched on FH would be quite plausible if there were a buyer for it that wanted to attempt to operate it at a profit. Paint me dubious about that last part, though.
« Last Edit: 10/03/2015 09:12 PM by sdsds »
-- sdsds --

Offline 93143

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Re: SLS General Discussion Thread 2
« Reply #206 on: 10/03/2015 10:15 PM »
EDIT:  After double-checking a bit, it seems my memory was correct; from what we know, BA-2100 is not close to being light enough for the 53-tonne Falcon Heavy to lift it.  Some sort of upgrade would be required.

Well talk with Bigelow about that, but if the moniker "BA-2100" is what bothers you, change the name to BA-2000, or BA-1782.  Remember it doesn't have a firm requirement - it's notional.

This whole discussion is notional, raised in answer to another poster's "obviously".  You're fighting a straw man here.

Offline Proponent

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Re: SLS General Discussion Thread 2
« Reply #207 on: 10/04/2015 10:50 AM »
To exactly which document do you refer?  If to "ESD Integration; Budget Availability Scenarios" dated 19 August 2011 (attached to this post), where does the statement appear?

Right below every sand chart, it says the following:

FY11:  21st CGS = CxP GO; MPCV = CxP Orion + EVA + MO; SLS =Ares I FS (Booster / Avionics), Ares I J-2X (US Engine), SSP SSME (Core Engine), SSP ET (Core Stage), Ares I PM / VI / S&MA / FITO (Prog Integ)

I may have overstated the clarity of the statement somewhat; how would you interpret this?

The notation below each sand chart looks to me like a broad-brush description of the hardware elements.  We can't take it too literally, though.  For example, while SLS's core stage superficially looks just like a Space Shuttle ET, it is in fact quite different, if for no other reason than the very different loads it bears.

Booz Allen Hamilton produced a contemporaneous critique (summary attached, for those who may not have seen it earlier) which described the cost savings NASA assumed for Orion/SLS as poorly justified.  Regardless of whether the criticism was correct, it does show that the ESD budget scenarios assumed future cost savings and were not based solely on Shuttle/Ares costs.

Offline 93143

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Re: SLS General Discussion Thread 2
« Reply #208 on: 10/07/2015 02:33 AM »
For example, while SLS's core stage superficially looks just like a Space Shuttle ET, it is in fact quite different, if for no other reason than the very different loads it bears.

As an aerospace engineer who's been following the SD-HLV saga in some detail since 2007, I'm not quite sure how to respond to this.

I'm not proposing that they copied total costs for the referenced elements exactly; I would assume they used more detailed data as a basis for their estimates, taking the necessary changes into account.

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Booz Allen Hamilton produced a contemporaneous critique (summary attached, for those who may not have seen it earlier) which described the cost savings NASA assumed for Orion/SLS as poorly justified.

Poorly justified in the sense that NASA did not provide sufficient rationale to BAH for the savings they incorporated into the estimates, not in the sense that the savings were unlikely to be realized.  According to people who read it, the actual report was clearer about this distinction than the executive summary.

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Regardless of whether the criticism was correct, it does show that the ESD budget scenarios assumed future cost savings and were not based solely on Shuttle/Ares costs.

Note that the ESD Integration document and the BAH report summary you attached are dated the same day.  Note also that the BAH report talks about the cost estimation cycle that produced the estimates they were critiquing having wrapped up in June of that year.  Case #1 in the ESD Integration document is labeled "6/27/11 ESD Preliminary Cost Estimate"; the others are not.  In other words, what BAH was analyzing was, at most, specifically Case #1.  (I'm not certain we can assume even that, as BAH makes no mention of ESD Integration, instead referring to estimates generated independently by the SLS, MPCV, and 21CGS programs.)

I have already complained about how Case #1 seems to make unexplained assumptions about cost savings that allow it to actually fly missions during Block 2 development with an annual budget for SLS + ground systems of less than $2B in then-year dollars (the 2025 budget for those elements is about $1.3B in 2011 dollars), despite the fact that from Cases #3 and #4 it looks like the basic carrying costs are higher than that.

Case #4, the one I used for my analysis, looks a bit different.  At one flight per year, the 2025 budget for SLS + ground systems is $2.17B in 2009 dollars, compared with $2.06B in 2009 dollars for J-246 at the same flight rate.  As far as fixed costs are concerned, it seems to me that the only major difference between J-246 and SLS is the upper stage; SLS in that document uses a big J-2X-based second stage instead of an RL-10-based EDS.  (I wouldn't expect the DCSS to add much fixed cost, since SLS in this scenario represents a definite minority of its flights.)  The marginal cost of the first flight every year would also be somewhat higher (particularly since it includes two upper stages), but not by a vast amount (for reference, the original ICPS contract had options for two additional flight units, totaling $132M).  And I believe DIRECT's MO was to assume traditional contracting and then pack their numbers with margin (though I'm not sure how much would have been added to running costs as they are easier to predict than development costs).  Unless DIRECT's numbers excluded ground systems ($400M in 2009 dollars), I don't see "large" cost savings assumed here.

Either way, the presence of the element enumeration under Case #1's sand chart does indicate that it probably doesn't mean what I took it to mean.  Good catch.  (This should have been evident to me from Case #1's budget numbers; I'm not sure why I maintained otherwise in the first place...)

Perhaps this is why the document was never officially released.  It is a presentation, after all; perhaps it works better with a presenter available to explain the assumptions...
« Last Edit: 10/07/2015 04:23 AM by 93143 »

Offline Proponent

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Re: SLS General Discussion Thread 2
« Reply #209 on: 10/13/2015 11:37 AM »
Thanks to BAH, we know that NASA built to-be-realized cost efficiencies into at least some of its scenarios.  There is a theoretical possibility that NASA applied those efficiencies only to Case 1 and not to other cases, but that's rather unlikely and would be positively disingenuous.  No justification has yet been presented for "the ESD Integration estimates were based directly on Shuttle and Ares."

You infer that inflation has been built into ESD's estimates.  How do you do that?  With budgets generally flat-lining, except for an explicit in-space-elements "wedge" in later years, it looks to me like everything is priced in FY 2012 dollars.  "RY" might mean "real": I suppose to people who spend their workdays with terms like "FY", "CY" and "TY, " a construction like "RY" might seem reasonable.
« Last Edit: 10/13/2015 05:06 PM by Proponent »

Offline spacenut

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Re: SLS General Discussion Thread 2
« Reply #210 on: 10/13/2015 03:50 PM »
If they are going to build a station, I agree it should be at L1 or L2.  I also wish they would build a rotating station at least with moon gravity.  I would really like them to build one based on Mars gravity, to test long term effects of Martian gravity on humans.  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. 

If it is a LEO station, it should at least be a fuel depot with not only LOX, but liquid methane, and argon or xenon for SEP tug refueling.  It could be manned continuously to monitor the fuels, and make maybe have robotic arms for helping SEP tugs refuel, or various vehicles to dock and refuel for out flights.  It could be a holdover for astronauts going to and from the Moon, an L station or Mars.  If they are going to the moon, they would have time during refueling, to exercise at the station or relax.  Cramped trips to the moon and back, it would be a break.  Eventually reusable moon transports could fly between the LEO refueling station, and an L station.  Then there could be reusable moon landers transporting between an L station and the moon's surface. 

All this can be future planned 100 ton launches from the SLS, to minimize in space assembly.  Smaller components could be launched using existing launchers, FH, and Vulcan.  Until SpaceX gets the BFR going. 

Offline Coastal Ron

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Re: SLS General Discussion Thread 2
« Reply #211 on: 10/14/2015 12:10 AM »
If they are going to build a station, I agree it should be at L1 or L2.  I also wish they would build a rotating station at least with moon gravity.  I would really like them to build one based on Mars gravity, to test long term effects of Martian gravity on humans.

FYI, here are two threads that are more relevant for space stations:

Space Policy Discussion / Re: Space Stations after 2024

Advanced Concepts / Re: Realistic, near-term, rotating Space Station

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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.

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All this can be future planned 100 ton launches from the SLS, to minimize in space assembly.  Smaller components could be launched using existing launchers, FH, and Vulcan.  Until SpaceX gets the BFR going.

I'm not aware of any design for a rotating station that requires 100 ton modular components (i.e. SLS), or even 50 ton components (i.e. FH).  And using Earth analogies, we build the largest buildings in the world using the same sized semi-trailer trucks that we use for much building small houses, so I think $/kg will be the more important metric for determining which type of transportation is used, not size.
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 93143

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Re: SLS General Discussion Thread 2
« Reply #212 on: 10/14/2015 06:40 AM »
No justification has yet been presented for "the ESD Integration estimates were based directly on Shuttle and Ares."

I already acknowledged that the estimate sourcing probably wasn't as direct as I initially thought.  Actually, it seems I was more careful last time I discussed this, but this time I got overzealous and misinterpreted my memory of the discussion...  Sorry about that.

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Thanks to BAH, we know that NASA built to-be-realized cost efficiencies into at least some of its scenarios.

That's assuming the estimate they were reviewing was actually the same one as in the document, which seems reasonable but is not yet solidly established as far as I am aware.

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There is a theoretical possibility that NASA applied those efficiencies only to Case 1 and not to other cases, but that's rather unlikely and would be positively disingenuous.

Unless the bulk of these "efficiencies" involved nerfing the infrastructure and similar measures, as a desperation move to force the annual cost to fit under the budget bogey, rather than technological and contracting improvements.  This does not seem inconsistent with what BAH say in the report, or with the contents of the ESD Integration document itself.

Also, the cost estimators would have been working with BAH prior to the ESD Integration presentation on August 19, so they might have reacted to early feedback by producing additional estimates that relaxed some of the efficiency measures to fill out a more reasonable budget.  It's hard to tell without the verbal presentation (and presumably question period) that would have accompanied the slides at NASA - this was not, after all, an official release...

...

As I explained above, while there may be a modest amount of efficiency gain built into Case #4, it matches J-246 closely enough that I doubt anything radical was present in the numbers.  (BAH didn't specify what exactly they meant by "large"...)  Also keep in mind that this document predates all the reports of stuff that's actually been done, some of which does seem to qualify as radical...

There's a fairly small marginal cost difference evident between #4a and #4b, which makes the huge jump from Case #1 look outright suspicious; hence my assumption that the latter contained additional measures.  However, it occurs to me that it might be somewhat explicable; DIRECT budgeted several hundred million dollars a year in JUS fixed costs, so the lack of a large upper stage might explain most of the difference.  It does not, however, explain how they managed to fit "Competitive Booster" in by 2023...  maybe that's what BAH was complaining about...

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You infer that inflation has been built into ESD's estimates.  How do you do that?  With budgets generally flat-lining, except for an explicit in-space-elements "wedge" in later years, it looks to me like everything is priced in FY 2012 dollars.

Look at what happens in the Senate cases once development ends.  There's a clear inflation in the ops budget lines year-to-year, and it basically matches the 2011 NASA New Start Inflation Index out-year value of 2.6%.

Besides, BAH states that inflation was incorporated into all three program estimates, though MPCV used outdated tables.

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"RY" might mean "real": I suppose to people who spend their workdays with terms like "FY", "CY" and "TY, " a construction like "RY" might seem reasonable.

I looked it up.  It's "real year" dollars, which at NASA means "then year", ie: inflated, dollars.  This is apparently different from how some other organizations use "real year"...

Offline 93143

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Re: SLS General Discussion Thread 2
« Reply #213 on: 10/14/2015 06:44 AM »
I'm not aware of any design for a rotating station that requires 100 ton modular components (i.e. SLS), or even 50 ton components (i.e. FH).

Those are LEO masses.  For an L-point station you'd be looking at much smaller units, unless you postulate additional propulsion technologies (depots, large electric tugs).

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And using Earth analogies, we build the largest buildings in the world using the same sized semi-trailer trucks that we use for much building small houses, so I think $/kg will be the more important metric for determining which type of transportation is used, not size.

http://www.jbis.org.uk/paper.php?p=2003.56.362
« Last Edit: 10/14/2015 07:19 AM by 93143 »

Offline Coastal Ron

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Re: SLS General Discussion Thread 2
« Reply #214 on: 10/14/2015 02:37 PM »
I'm not aware of any design for a rotating station that requires 100 ton modular components (i.e. SLS), or even 50 ton components (i.e. FH).

Those are LEO masses.  For an L-point station you'd be looking at much smaller units, unless you postulate additional propulsion technologies (depots, large electric tugs).

If we're moving construction mass beyond LEO, then using SEP tugs or some other form of more efficient transportation would be used - we don't have to be constrained by the limitations of an upper stage.

Quote
Quote
And using Earth analogies, we build the largest buildings in the world using the same sized semi-trailer trucks that we use for much building small houses, so I think $/kg will be the more important metric for determining which type of transportation is used, not size.

http://www.jbis.org.uk/paper.php?p=2003.56.362

I'm not paying money for some 12 year old random study to try and figure out whether you have a point or not.
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 oldAtlas_Eguy

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Re: SLS General Discussion Thread 2
« Reply #215 on: 10/14/2015 03:16 PM »
I'm not aware of any design for a rotating station that requires 100 ton modular components (i.e. SLS), or even 50 ton components (i.e. FH).

Those are LEO masses.  For an L-point station you'd be looking at much smaller units, unless you postulate additional propulsion technologies (depots, large electric tugs).

If we're moving construction mass beyond LEO, then using SEP tugs or some other form of more efficient transportation would be used - we don't have to be constrained by the limitations of an upper stage.

Quote
Quote
And using Earth analogies, we build the largest buildings in the world using the same sized semi-trailer trucks that we use for much building small houses, so I think $/kg will be the more important metric for determining which type of transportation is used, not size.

http://www.jbis.org.uk/paper.php?p=2003.56.362

I'm not paying money for some 12 year old random study to try and figure out whether you have a point or not.
The point is true but only for the case where the number of total modules flown on the larger booster is less than a factor of 3 than the number of unique module designs. This holds for using a comparison of FHR and SLS where <40mt vs 100mt and a price difference factor for launch of 5.3. The cost of design of a module does not vary due to its size unless you get to very small building elements vs complete large modules. But manufacturing costs do vary based on module size. So for an ISS like station using SLS would be about 50% cheaper than using FHR to put all the same capability up in larger modules than using smaller modules with a smaller booster.

But for a much larger station whose factor of total modules to unique modules is 5 or 10 then using the smaller much cheaper LV gives a savings of 18% to 35% over using larger modules and the more expensive larger booster.

The point is that the economics models have assumptions and that your overall station design can drive one method of launch to be significantly cheaper overall than another. You would have to specify how you would design the station the, number of unique systems and their total weight per system, if the systems can be in smaller units but just more of them or if the units cannot be shrunk and have to be divided into sub-units, and if there are required redundancies involved for the systems or not , etc.

There is no way to definitively make the statement that one launch method will decrease your total station cost vs another unless you have some sort of preliminary design for the systems to be used and all the capabilities to be incorporated. Then you can model out the design economically to determine which direction to go small cheap $/kg launcher vs larger high cost $/kg launcher (we are talking about a factor of grater than 2 in payload size between launchers).

Offline Zed_Noir

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Re: SLS General Discussion Thread 2
« Reply #216 on: 10/14/2015 05:04 PM »
@oldAtlas_Eguy you do realize that a SLS that can put 100mt in LEO is a Block 2 variant. We only have the Block-1 and maybe the Block-1B available for the foreseeable future. I am guessing the SLS can get roughly 50 or 60 mt up to LEO with a non-Block-2 variant.

Offline Mark S

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Re: SLS General Discussion Thread 2
« Reply #217 on: 10/14/2015 05:10 PM »
@oldAtlas_Eguy you do realize that a SLS that can put 100mt in LEO is a Block 2 variant. We only have the Block-1 and maybe the Block-1B available for the foreseeable future. I am guessing the SLS can get roughly 50 or 60 mt up to LEO with a non-Block-2 variant.

No, Block-2 is 130mt. Block-1 is basically the development version. Block-1B is the future workhorse variant, and it will put more than 100mt into LEO.

Mark S.

Offline ThereIWas3

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Re: SLS General Discussion Thread 2
« Reply #218 on: 10/14/2015 05:27 PM »
It could be manned continuously to monitor the fuels, and make maybe have robotic arms for helping SEP tugs refuel, or various vehicles to dock and refuel for out flights.

I do not think it needs to be continuously manned to do those things.  If the USAF is talking about assmbling large structures in space using entirely remotely operated technology.   And continuous occupation at an EM Lagrange point has nasty levels to worry about.
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Online oldAtlas_Eguy

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Re: SLS General Discussion Thread 2
« Reply #219 on: 10/14/2015 05:48 PM »
@oldAtlas_Eguy you do realize that a SLS that can put 100mt in LEO is a Block 2 variant. We only have the Block-1 and maybe the Block-1B available for the foreseeable future. I am guessing the SLS can get roughly 50 or 60 mt up to LEO with a non-Block-2 variant.

No, Block-2 is 130mt. Block-1 is basically the development version. Block-1B is the future workhorse variant, and it will put more than 100mt into LEO.

Mark S.
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.

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