Poll

Should NASA ditch asteroids and Mars to help lead the strong international interest for Lunar missions?

Stay with the current Mars plan
18 (17.5%)
Go to Mars but on a new plan
17 (16.5%)
Go to the Moon solo
21 (20.4%)
Join in an international Moon quest
47 (45.6%)

Total Members Voted: 102

Voting closed: 02/12/2016 08:01 pm


Author Topic: Should NASA refocus on returning to the Moon?  (Read 129290 times)

Offline ncb1397

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Re: Should NASA refocus on returning to the Moon?
« Reply #280 on: 12/24/2016 05:46 pm »
Just to flesh out ideas on how Moon and Mars don't have to be in conflict with each other. And you can do both using assets and technology that NASA already has or is over half-way through the development pipeline.





























mods: I used a photo from one of your articles for the picture of RS-25 engines on slide 12...feel free to delete that slide if you want to. Just wanted to show that a lot of the stuff we need(about 50%) is real existing working hardware that exists today in physical reality(not powerpoint).
« Last Edit: 12/28/2016 08:53 pm by ncb1397 »

Offline ncb1397

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Re: Should NASA refocus on returning to the Moon?
« Reply #281 on: 12/24/2016 06:06 pm »
I always questioned this assumption. Sure, supersonic atmospheric entry and supersonic atmospheric retro-propulsion introduces all kinds of problems in the design of a lander, but why not do the following:

1.)zero out the horizontal/vertical velocity at 25 km altitude.

You'd have to use a lot of fuel to do that, so that's your tradeoff.  Especially if you mandate that every kg of mass you want on the surface of Mars has to use this method.  So using the Mars atmosphere reduces the amount of fuel that you need to bring along with you (or ship ahead).

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In my opinion, propulsive EDL and ascent on Mars is completely doable(total delta-v is less than earth to LEO) and supersonic entry and supersonic retro-propulsion will lead to all kinds of compromises in terms of design that will mean a whole new system will be required for doing anything else efficiently(whether that is in-space maneuvers or landing on anything that isn't Mars).

Of course if you perfect being able to land on Mars and Earth using retropropulsion, then those same vehicles can obviously land on an airless world too - which is what Musk has stated.  So whoever wants to use one for going to the Moon would be able use one (and Musk might even sell to them).

But otherwise it's a question of money as to what method is used, and Musk has decided what he wants to use...

Landing a vehicle designed for aerodynamic entry on the moon wastes fuel/payload. Stripping the heatshield and aeroshell out of it adds payload pound for pound. It is the same situation as using a lander optimized for airless landing in an thin atmosphere. What tips the balance is that most surfaces in the solar system are either not survivable or not covered in an atmosphere. Saturn and Jupiter have too much atmosphere while Moon, Pluto, Ceres have too little atmosphere. There are very few surfaces that are in the goldilocks zone where a vehicle optimised to transport cargo to a surface using aerobraking can land with that method and humans/vehicles can survive on the surface. The only "goldilocks" bodies are Mars, Earth and Titan while the number of bodies in total is vast: https://en.wikipedia.org/wiki/List_of_Solar_System_objects_by_size.

Offline Coastal Ron

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Re: Should NASA refocus on returning to the Moon?
« Reply #282 on: 12/24/2016 06:29 pm »
Landing a vehicle designed for aerodynamic entry on the moon wastes fuel/payload.

Designing, building, testing and operating only one vehicle is far less costly than having to do that with two designs.  Being less efficient with fuel is an acceptable tradeoff, especially when you operate your own fuel depot system.

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Stripping the heatshield and aeroshell out of it adds payload pound for pound.

The proposed SpaceX ITS is planned to be able to land almost 1,000,000 lb of cargo on the surface of Mars, I'd say that should meet the needs of any lunar activity for quite a while, even if it still has to carry a heatshield.

And normally you only optimize transportation systems once you understand your needs, and early on when we finally do return to the Moon we'll need general transports more than specific-use ones.  And you can waste a lot of money trying to optimize before you know what you're optimizing for.

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What tips the balance is that most surfaces in the solar system are either not survivable or not covered in an atmosphere.

This discussion is only about NASA returning to our Moon.  What SpaceX may or may not do beyond our Moon is OT.
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 ncb1397

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Re: Should NASA refocus on returning to the Moon?
« Reply #283 on: 12/24/2016 06:36 pm »
This discussion is only about NASA returning to our Moon.  What SpaceX may or may not do beyond our Moon is OT.

I think you mean NASA, not SpaceX? Anyways, I think if a Mars optimized lander architecture is more of a dead-end than a Moon optimized lander architecture, it merits being considered in the "stay with Mars or switch to the Moon" debate.

Designing, building, testing and operating only one vehicle is far less costly than having to do that with two designs.  Being less efficient with fuel is an acceptable tradeoff, especially when you operate your own fuel depot system.

Which is exactly why any lander that NASA develops shouldn't be optimized for one location. You don't want to build something for each destination.

The proposed SpaceX ITS is planned to be able to land almost 1,000,000 lb of cargo on the surface of Mars, I'd say that should meet the needs of any lunar activity for quite a while, even if it still has to carry a heatshield.

The ITS has borderline fantasy specs. The tanker ship doesn't just have single-stage-to-orbit...it is single-stage-to-GTO. At minimum, it is operating on razer-thin margins on a finicky construction material with no abort capability.
« Last Edit: 12/24/2016 07:06 pm by ncb1397 »

Offline Coastal Ron

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Re: Should NASA refocus on returning to the Moon?
« Reply #284 on: 12/24/2016 07:35 pm »
Just to flesh out ideas on how Moon and Mars don't have to be in conflict with each other.

Your slide deck is like every other hardware-oriented slide deck - it ignores the most important question.  Why should the U.S. Taxpayers fund NASA to go back to the Moon?

The reason we haven't returned to the Moon is not because of a lack of hardware concepts or ideas, nor the technical ability.

What we have lacked is the national need.  Identify that, get everyone to buy into it, and the hardware part will take care of itself...
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 ncb1397

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Re: Should NASA refocus on returning to the Moon?
« Reply #285 on: 12/24/2016 08:05 pm »
Just to flesh out ideas on how Moon and Mars don't have to be in conflict with each other.

Your slide deck is like every other hardware-oriented slide deck - it ignores the most important question.  Why should the U.S. Taxpayers fund NASA to go back to the Moon?

The reason we haven't returned to the Moon is not because of a lack of hardware concepts or ideas, nor the technical ability.

What we have lacked is the national need.  Identify that, get everyone to buy into it, and the hardware part will take care of itself...

So, not only does "everyone" have to agree on what it is we are going to do, the motivation has to be the same as well? In some perfect utopian/orwellian idealistic society, that may be possible, but it is an impossible standard to achieve.

Does everyone agree on the F-35 program? And not only do they all agree that f-35 should continue, the reasons why it will continue are all the same? Person A doesn't support it because of jobs in his districts, person B doesn't support it because of fear of China/Russia, person C doesn't support it because the CEO of Lockheed Martin is considered a personal friend? That is not the case. Bernie Sanders and the congressman in this letter(https://www.documentcloud.org/documents/3144751-10-4-2016-Letter-to-Conference.html#document/p1) probably have very different reasons to support it.

Really it could actually only come down to a handful of people. Take the Europa mission. Hardly anybody in the government wanted it but some scientists in the decadal survey placed it on a priority list. It really came down to one person, Rep. John Culberson, whether it happened or not. Same thing with Apollo. It was one person: Kennedy. Or STS: Nixon. Nixon might have approved STS because they could steal soviet satellites while other people supported it for scientific applications.

Anyways, a Moon program doesn't require a constitutional amendment that needs anything like 3/4s of the states. Really all you need is simple majorities in a few committees and a president that isn't completely hostile to the idea.

The fact is, you can get hawks and doves to support human space flight in general and human space exploration specifically. Doves can support it as a model of cooperation of an international coalition of peaceful coexisting governments. Hawks can support it to maintain the high ground over the Chinese/Russians. They don't need the same reason.

edit: Most of the debate is on destinations and missions, not whether we will do human space flight or not. That is why you should build a completely destination agnostic approach. That way, a change in destination doesn't require some massive decade long engineering effort to accomplish. The flexible path is a good one. The systems that NASA is working on today have multiple flight profiles and possible utilization schemes.

« Last Edit: 12/24/2016 08:33 pm by ncb1397 »

Offline Coastal Ron

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Re: Should NASA refocus on returning to the Moon?
« Reply #286 on: 12/24/2016 09:51 pm »
So, not only does "everyone" have to agree on what it is we are going to do, the motivation has to be the same as well? In some perfect utopian/orwellian idealistic society, that may be possible, but it is an impossible standard to achieve.

Everyone in the funding loop.  Even the public was not enamored with the Apollo program until just before it succeeded, but the political need was known to the politicians, and they gave it a tremendous amount of funding because of the perceived need.

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Does everyone agree on the F-35 program?

The F-35 was originally funded because it was going to solve a national need.  It was always going to be a massive program, and I would wager no one is surprised that it has had problems.  But it is still going to be solving a national need, which in this case is defense of our nation.

What is the need that sending government employees to the Moon solves (or Mars for that matter too)?  Apparently nothing bad happened during the past 45 years since we left the Moon, so waiting another 45 shouldn't be a problem, right?

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Really it could actually only come down to a handful of people.

NASA is not going anywhere beyond LEO without a significant increase to it's budget, and I see that you recognize that too.  Significant budget increases require significant political discussions, and not just with a few people in Congress.

I think the SLS and Orion programs have made people forget how hard normal programs are to get funded, since the SLS and Orion were funded, essentially, as a subset of the Constellation program as it was getting cancelled.  So no new funding was required for NASA, just a shuffling of funds.  And that was done by a few Senators.  But otherwise a new major program will cause discussion and debate in Congress.

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Take the Europa mission. Hardly anybody in the government wanted it but some scientists in the decadal survey placed it on a priority list. It really came down to one person, Rep. John Culberson, whether it happened or not.

It may seem that way to you, but without a sponsor in the Senate, and support from the Appropriations committees, it wouldn't have happened even if Culberson wanted it.  The Europa mission is one of the NASA "Flagship Program" missions, which Congress has been supporting, so all Culberson did was move it along as others have done.  And if he stopped it, well they it would have been pushed out to some undefined future date.  Not a big deal, right?

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Anyways, a Moon program doesn't require a constitutional amendment that needs anything like 3/4s of the states. Really all you need is simple majorities in a few committees and a president that isn't completely hostile to the idea.

Not when you are talking about spending $Billions more on NASA for decades to come.  There are fights in Congress over far less funding all the time.

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The fact is, you can get hawks and doves to support human space flight in general and human space exploration specifically. Doves can support it as a model of cooperation of an international coalition of peaceful coexisting governments. Hawks can support it to maintain the high ground over the Chinese/Russians. They don't need the same reason.

No one in our military buys into the idea of the Moon being "the high ground", and there is little appetite with Republicans today to do international partnerships - especially not with the incoming Trump administration.

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edit: Most of the debate is on destinations and missions, not whether we will do human space flight or not. That is why you should build a completely destination agnostic approach. That way, a change in destination doesn't require some massive decade long engineering effort to accomplish. The flexible path is a good one.

I agree.

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The systems that NASA is working on today have multiple flight profiles and possible utilization schemes.

I disagree.  The SLS is too expensive to use, and the Orion is limited to the region of our Moon and too expensive to use too.  Plus both are NASA-only assets, which means the private sector won't use them, nor would possible international partners.  Which is why they are actually a liability for NASA, not assets.  IMHO.
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 ncb1397

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Re: Should NASA refocus on returning to the Moon?
« Reply #287 on: 12/24/2016 10:02 pm »
I disagree.  The SLS is too expensive to use, and the Orion is limited to the region of our Moon and too expensive to use too.  Plus both are NASA-only assets, which means the private sector won't use them, nor would possible international partners.  Which is why they are actually a liability for NASA, not assets.  IMHO.

I disagree that SLS and Orion are NASA-only assets. The private sector use of the ISS is an example of that, even though NASA operates the vehicle, commercial use is not precluded. Also, I seem to remember a member of the Saudi Royal family riding on STS, and so not even space tourism would be out of the question. As far as operational cost of these programs, it seems you have information that others don't. What is the operational cost of SLS and Orion?
« Last Edit: 12/24/2016 10:04 pm by ncb1397 »

Offline Coastal Ron

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Re: Should NASA refocus on returning to the Moon?
« Reply #288 on: 12/24/2016 11:20 pm »
I disagree that SLS and Orion are NASA-only assets.

Certainly there is no law saying other departments or agencies of the U.S. Government can't use the SLS, or that the private sector couldn't buy a launch or two.

But for all practical purposes there is no other USG department or agency that plans to use the SLS, and the only private sector entities that would need the capabilities the SLS provides are planning on building their own space transportation systems.  So by process of elimination there are no other potential users for the SLS.

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The private sector use of the ISS is an example of that, even though NASA operates the vehicle, commercial use is not precluded.

Commercial use is one of the planned goals of the ISS.  And the key word here is "planned", whereas the SLS has no real forecasted need that it satisfies, and it was definitely not built with the private sector as a potential customer.

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Also, I seem to remember a member of the Saudi Royal family riding on STS, and so not even space tourism would be out of the question.

Everyone that flew on the Shuttle flew for free, or as part of a barter agreement with other nations.  Justification for free flights included standard political type stuff, which I would imagine included the Saudi citizen.

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As far as operational cost of these programs, it seems you have information that others don't. What is the operational cost of SLS and Orion?

No one in the public knows for sure, and NASA is even keeping Congress in the dark.  But we have lots of recent analogies that can be applied, such as Shuttle program costs that are comparable, and the fact that both the SLS and Orion are 100% expendable vehicles.  As someone that has a background in product cost rollups, this is not hard stuff to estimate.  YMMV
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 gbaikie

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Re: Should NASA refocus on returning to the Moon?
« Reply #289 on: 12/25/2016 04:10 am »
So, not only does "everyone" have to agree on what it is we are going to do, the motivation has to be the same as well? In some perfect utopian/orwellian idealistic society, that may be possible, but it is an impossible standard to achieve.

Everyone in the funding loop.  Even the public was not enamored with the Apollo program until just before it succeeded, but the political need was known to the politicians, and they gave it a tremendous amount of funding because of the perceived need.

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Does everyone agree on the F-35 program?

The F-35 was originally funded because it was going to solve a national need.  It was always going to be a massive program, and I would wager no one is surprised that it has had problems.  But it is still going to be solving a national need, which in this case is defense of our nation.

What is the need that sending government employees to the Moon solves (or Mars for that matter too)?  Apparently nothing bad happened during the past 45 years since we left the Moon, so waiting another 45 shouldn't be a problem, right?

F-35 was fifth generation fighter jet.
Roughly, F-35 is same reason you get new car models each year.

There is no need to send governmental employees to the Moon.
There are reasons to explore the Moon and reasons to explore Mars.
Since time after Apollo we have had the Shuttle and ISS program.
The Shuttle program is over, and ISS is planned to end.
And one could ask what is next?
Really the same kind of question in regard to F-35  program
One reason [not only reason] the shuttle program ended was because "we" wanted to do something other
than just stay in LEO.
One could argue that we can redo the Shuttle and continue ISS for decades more.
One could also argue that "we" tried to do the LEO thing and it didn't have much upside to it.
But it seems we will not redo Shuttle and ISS will be terminated with 10 years or so.
So it's not as if NASA not being doing stuff for 45 years. And one could ask should NASA continue to exist- or should NASA actually try to explore the space beyond LEO.
A purpose of Shuttle program was to lower cost of access to LEO. A purpose of ISS was to prepare for manned mission beyond LEO and see if there could be commercial applications of micro-gravity and the vacuum of LEO.
One could say that ISS has degraded to being something to do with foreign policy/international relations- or at least that is benefit commonly mentioned which is said important which is associated with ISS, rather than other things which may be being accomplished with ISS program.

So exploring the Moon doesn't "have to" have crew, but it makes sense to use crew in order to explore the Moon.
There are many things which could be done with the Moon in the future, but a near terms question is does the Moon have minable water. If it does, then one can do many things on the Moon.
In terms of Mars, people might live on Mars in the future, and NASA should explore Mars to determine if such possibility is viable.

Offline ncb1397

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Re: Should NASA refocus on returning to the Moon?
« Reply #290 on: 12/25/2016 09:27 pm »
Quote
The private sector use of the ISS is an example of that, even though NASA operates the vehicle, commercial use is not precluded.

Commercial use is one of the planned goals of the ISS.  And the key word here is "planned", whereas the SLS has no real forecasted need that it satisfies, and it was definitely not built with the private sector as a potential customer.

No, commercial use of the ISS is a fact today. Just as an example, the movie "A Beautiful Planet" was filmed on the ISS, and grossed at least 9 million wordwide in theaters. Sure, that is only .3% of the the roughly 3 billion per year that ISS costs to operate, but it is also only one example. Cubesats deployed from ISS is another example and Urthecast registered 41.1 million in revenue in 2015. Certainly, break-even by any metric is far off but that goes without saying.

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As far as operational cost of these programs, it seems you have information that others don't. What is the operational cost of SLS and Orion?

No one in the public knows for sure, and NASA is even keeping Congress in the dark.  But we have lots of recent analogies that can be applied, such as Shuttle program costs that are comparable, and the fact that both the SLS and Orion are 100% expendable vehicles.  As someone that has a background in product cost rollups, this is not hard stuff to estimate.  YMMV

NASA isn't hiding anything. They don't know what the costs will be just as they didn't know what the costs of STS would be. And Orion isn't 100% expendable.
« Last Edit: 12/25/2016 09:34 pm by ncb1397 »

Offline Oli

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Re: Should NASA refocus on returning to the Moon?
« Reply #291 on: 12/25/2016 09:56 pm »
Just to flesh out ideas on how Moon and Mars don't have to be in conflict with each other. And you can do both using assets and technology that NASA already has or is over half-way through the development pipeline.

1.5MW is not sufficient for crew transfer given that kind of mass.

Or what are the SEP specs?

Offline Phil Stooke

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Re: Should NASA refocus on returning to the Moon?
« Reply #292 on: 12/25/2016 11:37 pm »
"What is the operational cost of SLS and Orion?"

"No one in the public knows for sure, and NASA is even keeping Congress in the dark."

As stated just above, NASA is not hiding the cost, they don't know it yet.  The unit cost of a launch is closely related to the frequency of launch, which is to a great extent controlled by Congress. 

Offline Coastal Ron

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Re: Should NASA refocus on returning to the Moon?
« Reply #293 on: 12/25/2016 11:42 pm »
F-35 was fifth generation fighter jet.
Roughly, F-35 is same reason you get new car models each year.

That supports building a next generation space station to replace the ISS, but the SLS is not replacing any capability NASA already had - the Shuttle could only put into LEO the same payload that existing commercial launchers can, both in size and weight.  So if anything that supports the claim that the private sector has replaced the Shuttle.

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One could argue that we can redo the Shuttle and continue ISS for decades more.
One could also argue that "we" tried to do the LEO thing and it didn't have much upside to it.

The mission of the ISS is to provide a foothold in space for humanity, and to help humanity figure out how to survive in space.  And we have learned a lot.  But we haven't learned enough yet, and it is certainly an open question whether we'll have enough time to figure out the missing pieces before the end of the ISS (whenever that is).

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So exploring the Moon doesn't "have to" have crew, but it makes sense to use crew in order to explore the Moon.

I agree from the standpoint that at some point the cost of getting to the Moon, and doing things on the Moon, will be low enough that sending humans to the Moon will be affordable.  But from a cost standpoint we're not there yet.

For instance, I would advocate that "we" (humanity, or some subset of it) needs to invest in creating a reusable transportation system to the region of the Moon first.  Why reusable?  Because from the cost estimates I've seen NASA would spend too much of it's budget going to the Moon if it had to only use the SLS and Orion.  Plus, we are missing everything else that is needed to sustain humans on the Moon, and that will take time to develop (and lots of money).

So from a cost standpoint NASA, and the rest of the world, is not yet ready to afford going beyond LEO.  Elon Musk thinks that they may have solved that problem, but he's doing for his own needs (i.e. colonizing Mars), and it's not proven out yet.

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There are many things which could be done with the Moon in the future, but a near terms question is does the Moon have minable water. If it does, then one can do many things on the Moon.

NASA is not a mineral extraction and processing agency, so I would let the private sector figure this out.  If the U.S. Government wants to be a customer, great, but otherwise there is no demand to merit funding this yet.  And while it could be argued that funding such an operation would be like funding the Transcontinental Railroad, I would argue that from a cost standpoint that we are still too far out from having discounted fuel be enough of an incentive for human expansion out into space.

Remember in 2013 when at a House hearing, Thomas Young (former EVP of Lockheed Martin) was asked how long it would take NASA to put a human on Mars with it's current budget.  His response was "Never."

NASA's budget hasn't changed significantly since then, and going to our Moon is not that much easier, so his testimony helps to validate my estimates.

As I've said many times, we've had the ability to return to the Moon since 1972, we just haven't had the interest in spending the money to go back.  Convince Congress we should go back and it will happen...
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 Coastal Ron

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Re: Should NASA refocus on returning to the Moon?
« Reply #294 on: 12/26/2016 12:03 am »
As stated just above, NASA is not hiding the cost, they don't know it yet.  The unit cost of a launch is closely related to the frequency of launch, which is to a great extent controlled by Congress.

My career has been in manufacturing operations, which includes doing product costing.  The SLS is not that complicated a product, so I know that NASA knows how much the SLS costs.

As to the frequency of launch, at the current funding levels that has already been determined:

"Boeing has Michoud set up to stamp out enough stages for one SLS a year — two at most with the factory’s current manufacturing capabilities, and then only if NASA pours more money and personnel into the facility."

And that matches NASA's mandated launch rate of no-less-than once per year for a safe flight cadence.

So initially at least, once they get out of testing and into operational mode, the flight rate is once per year.  That provides one end of the price range.

And you can see from that article quote that NASA has already taken into account the contingency that NASA will be asked to increase the SLS flight rate, so the factory could, with the current manufacturing capabilities, be increased to two per year.  I would expect Orbital ATK would be able to support that for the SRM's, and we know the launch pad can support that rate.

The final missing piece is how much Congress will allow NASA to buy in advance in order to lock in lower prices.  For instance, during the Shuttle program NASA was allowed to buy years worth of material, which is really the only way to run a transportation system.

Another example is that NASA has asked Aerojet Rocketdyne to restart production of the RS-25 engine, and NASA would have the cost data for that too.

NASA knows enough to provide Congress, and the public, with good estimates of what the SLS costs.  There is no question about that.
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 vapour_nudge

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Re: Should NASA refocus on returning to the Moon?
« Reply #295 on: 12/26/2016 12:20 am »
I still think NASA will choose to go back to the Moon in the next decade and do many other things with SLS. But, not because it is easy, because it is hard
« Last Edit: 12/26/2016 02:02 am by vapour_nudge »

Online oldAtlas_Eguy

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Re: Should NASA refocus on returning to the Moon?
« Reply #296 on: 12/26/2016 04:47 pm »
Returning to the Moon requires that the US gov will (Congress willingness to budget) intersects with the NASA cost projection of a return to the Moon.

Currently, the will is too low and the costs are too high. The level of will is unlikely to change. This leaves changing the cost to fit the level of will. A COTS like Public/Private partnerships could do it, but not a full NASA cost+ directed program. What this basically means is that while SLS/Orion exist there will only be sporadic Lunar missions probably of only limited robotic probes to the surface. SLS/Orion is sucking up all the gov will. We saw this with the budget conflicts of SLS/Orion and Commercial Crew. Because overlaps were perceived the budget will went to  SLS.

Offline ncb1397

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Re: Should NASA refocus on returning to the Moon?
« Reply #297 on: 12/28/2016 09:04 pm »
Just to flesh out ideas on how Moon and Mars don't have to be in conflict with each other. And you can do both using assets and technology that NASA already has or is over half-way through the development pipeline.

1.5MW is not sufficient for crew transfer given that kind of mass.

Or what are the SEP specs?

These were the specs that I was working off of:
fuel - 35,000 kg Xenon
solar power - 1500 MW @ 1 AU
engine power - 1375 MW
engine thrust - 23 N
isp - ~9500 seconds
Mars- ~50% power
Earth- 100% power

Which would yield approximate maneuver times of the manned interplanetary leg of:
-LEO to EML-1 - 7000 m/s (SEP ~30 months)...unmanned
-EML-1 to TMI - 650 m/s (chemical, PL stage 1), 200 m/s (SEP ~1 month)
-TMI to HMO - 600 m/s (chemical, PL stage 1), 600 m/s (SEP ~3 months)
-HMO to TEI -140 m/s (chemical, ITV main engine, PL stage 2), 1350 m/s(SEP ~5 months )
-TEI to earth/moon capture - 1300 m/s (SEP ~3 months)

It is a bit sluggish at Mars(5 months for TEI). If you look at slide 7 that I updated on the slide deck, that is a potential upgrade path but it uses TRL 6 150 W/kg solar panels vs TRL 9 80 W/kg. That would give you 80% SEP thrust at Mars. Otherwise, to save chemical fuel for TEI, you might look at aerobraking in other maneuvers with the solar array or a second tug that does the TMI burn(which adds a SHLV launch).

Offline Oli

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Re: Should NASA refocus on returning to the Moon?
« Reply #298 on: 12/29/2016 03:00 am »
Just to flesh out ideas on how Moon and Mars don't have to be in conflict with each other. And you can do both using assets and technology that NASA already has or is over half-way through the development pipeline.

1.5MW is not sufficient for crew transfer given that kind of mass.

Or what are the SEP specs?

These were the specs that I was working off of:
fuel - 35,000 kg Xenon
solar power - 1500 MW @ 1 AU
engine power - 1375 MW
engine thrust - 23 N
isp - ~9500 seconds
Mars- ~50% power
Earth- 100% power

Which would yield approximate maneuver times of the manned interplanetary leg of:
-LEO to EML-1 - 7000 m/s (SEP ~30 months)...unmanned
-EML-1 to TMI - 650 m/s (chemical, PL stage 1), 200 m/s (SEP ~1 month)
-TMI to HMO - 600 m/s (chemical, PL stage 1), 600 m/s (SEP ~3 months)
-HMO to TEI -140 m/s (chemical, ITV main engine, PL stage 2), 1350 m/s(SEP ~5 months )
-TEI to earth/moon capture - 1300 m/s (SEP ~3 months)

It is a bit sluggish at Mars(5 months for TEI). If you look at slide 7 that I updated on the slide deck, that is a potential upgrade path but it uses TRL 6 150 W/kg solar panels vs TRL 9 80 W/kg. That would give you 80% SEP thrust at Mars. Otherwise, to save chemical fuel for TEI, you might look at aerobraking in other maneuvers with the solar array or a second tug that does the TMI burn(which adds a SHLV launch).

Ah, so it's a hybrid?

600m/s + 650m/s = 1.25km/s.

A huge amount of fuel is needed for that, given the first vehicle is roughly 105t+104t+16t at departure. Does it come from the lander? If yes how to land?

Offline Robotbeat

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Re: Should NASA refocus on returning to the Moon?
« Reply #299 on: 12/29/2016 03:03 am »
I don't think NASA should, but it probably will. If a lander gets built. Which is really the only big thing we need now.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

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