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: 103

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


Author Topic: Should NASA refocus on returning to the Moon?  (Read 89273 times)

Online ncb1397

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Re: Should NASA refocus on returning to the Moon?
« Reply #340 on: 01/13/2017 02:11 PM »
That part of ISS was highly successful. It's too bad we didn't do more such aid for post-Soviet Russia in the 1990s, we may not have a tyrant in power there and geopolitical frictions like we have today. There really needed to be a post-Cold-War Marshall Plan. (And you could say the same thing about the Rust Belt and Appalachia, especially after the 2008 recession.) Anyway.

Russia has always been that way. If anything, the tyrant would just have more money and a bigger military, and ours would be smaller.

Online ncb1397

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Re: Should NASA refocus on returning to the Moon?
« Reply #341 on: 01/13/2017 02:13 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).

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?

A Mars mission would be 2+ landers although at least one would just be in space only.

Offline RocketmanUS

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Re: Should NASA refocus on returning to the Moon?
« Reply #342 on: 03/06/2017 01:31 AM »
Can we have our cake and eat it too?

F9 with new methane US and reusable tanker.
SX horizontal Lunar lander ( LCH4/LOX ), block I ~ 1,000 lb cargo to Lunar surface, Block II in-space refueling and crew cab.
This could help test out in-space refueling with propellant that ITS would use for Mars.
( Also could increase F9/FH payload to GTO or escape with in=space refueling. )
Tanker could be use as a temporary depot.
Tanker and US are on piece.
If Dragon 2 with FH is successful with their two passenger Lunar mission then Dragon 2 could be used with a modified version of this new US to send crew into LLO.
Note: FH would be a benefit but not needed with in-space refueling.

SX with ITS to Mars ( 1st mission ) by end of 2023

ULA could do the same with Vulcan/ACES with a horizontal Lunar lander with LH2/LOX and Orion launched on Vulcan.

This could be the goto Mars but on a new plan. NASA to seed both companies for Lunar. Later commercial could take over and NASA focus on Mars. If ITS is ready then use ITS. If ITS is not looking like it would be ready by end of 2021 then NASA to look to ULA and others. Use ULA's new in-space propellant transfer and depot and develop a lander/ascender for Mars. Could see crew on Mars by no later than 2030.

Fund both SX and ULA for the new hardware to the first few new Lunar exploration missions. Add in a Lunar base later if Congress wanted one ( experiment to see if people can live off world before sending crew to possibly colonize Mars ).

I originally voted Mars first but on a new plan. This could be the new plan but includes the moon, At least getting crew back to the moon were commercial could take over. This could get some of the needed hardware for both companies to send crew to Mars and be a benefit ( lower cost, reuse, and in-space refueling ) to launching other payloads to space.

Offline gospacex

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Re: Should NASA refocus on returning to the Moon?
« Reply #343 on: 03/06/2017 04:48 PM »
I think the Moon is the only logical choice as a destination for the next several decades at least.  It's close for both travel and communication times, it's a stable platform, it has mineral resources that can provide oxygen, metals, water and protection.

OTOH it lacks carbon, nitrogen, sulfur, chlorine and other volatiles. Hydrogen availability is questionable.

You need carbon and hydrogen to produce any sort of plastics, oils, paints, solvents. Many of them also require nitrogen and/or sulfur. Fertilizers need nitrogen. Chlorine is widely used in industry.

Offline Paul451

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Re: Should NASA refocus on returning to the Moon?
« Reply #344 on: 03/07/2017 08:18 PM »
Can we have our cake and eat it too?
Fund both SX and ULA for the new hardware to the first few new Lunar exploration missions.

Jon Goff speculated about combining SpaceX/ULA architecture. Sx carries the monkeys in Dragon, ULA launches the lunar lander (XEUS) and ACES TLI/TEI-booster.

http://selenianboondocks.com/2017/02/random-thoughts...

Functionally "single-bidder" by FAR standards -- since each contractor is exclusively supplying a discrete component -- while actually funding both systems to increase launcher availability for other missions.

Offline Paul451

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Re: Should NASA refocus on returning to the Moon?
« Reply #345 on: 03/07/2017 08:27 PM »
I think the Moon is the only logical choice as a destination for the next several decades at least.  [...] it has mineral resources that can provide oxygen, metals, water and protection.
OTOH it lacks carbon, nitrogen, sulfur, chlorine and other volatiles. Hydrogen availability is questionable.
You need carbon and hydrogen to produce any sort of plastics, oils, paints, solvents. Many of them also require nitrogen and/or sulfur. Fertilizers need nitrogen. Chlorine is widely used in industry.

WMB was speaking in terms of a few decades. It will take a long time before there's enough industry on the moon (or anywhere else) to convert basic hydrocarbons (CO₂, methane, etc) into the full range of complex plastics, paints, solvents, etc, necessary to compete with specialised materials sent from Earth. Bulk commodities alone -- oxygen, water, hydrolox-prop, bulk nickel-iron (from MM-dust), Lunacrete, etc -- represent enough work for decades of development. Highly processed materials, pressure-grade steel, structural aluminium, clear glass, etc, will take even longer.

Offline Bynaus

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Re: Should NASA refocus on returning to the Moon?
« Reply #346 on: 03/07/2017 08:47 PM »
I think the Moon is the only logical choice as a destination for the next several decades at least.  It's close for both travel and communication times, it's a stable platform, it has mineral resources that can provide oxygen, metals, water and protection.

OTOH it lacks carbon, nitrogen, sulfur, chlorine and other volatiles. Hydrogen availability is questionable.

You need carbon and hydrogen to produce any sort of plastics, oils, paints, solvents. Many of them also require nitrogen and/or sulfur. Fertilizers need nitrogen. Chlorine is widely used in industry.

I think you might find all that in the polar crater deposits - even hydrogen, mostly bound in water. These polar craters are really cold, colder than the surface of Pluto, and even if the volatiles are intermixed with some dirt, it should be easier to get them there than to bring them in from the Earth or somewhere else. Plus, not having any atmosphere, you can expect to find every element which is found in the solar wind (i.e., almost every element) implanted into the regolith layer (hence all the discussion about He-3 on the moon - which is misguided in my view - even though He is one of the most volatile elements).

Offline Coastal Ron

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Re: Should NASA refocus on returning to the Moon?
« Reply #347 on: 03/07/2017 09:21 PM »
WMB was speaking in terms of a few decades. It will take a long time before there's enough industry on the moon (or anywhere else) to convert basic hydrocarbons (CO₂, methane, etc) into the full range of complex plastics, paints, solvents, etc, necessary to compete with specialised materials sent from Earth. Bulk commodities alone -- oxygen, water, hydrolox-prop, bulk nickel-iron (from MM-dust), Lunacrete, etc -- represent enough work for decades of development. Highly processed materials, pressure-grade steel, structural aluminium, clear glass, etc, will take even longer.

Just because we can find building materials doesn't mean we have all we need to set up shop on the Moon.

Sure it's close, but absent living at the poles you have to endure two weeks of either full sun or no sun, and there is no atmosphere to moderate temperatures.

Which brings us back around to asking WHY NASA should refocus on returning to the Moon?

As far as what NASA does well, which is cutting-edge technology development, we've already conquered the Moon.  Returning is a matter of dusting off the Apollo blueprints and updating them for modern technology, but otherwise it's a pretty low bar to go back.

And what need does the U.S. Government have in returning to the Moon?  What does that solve?

At least the journey to Mars holds the possibility that we'll find life there, and Mars is the most Earth-like planet that is close-by.  Yet even all those positives doesn't mean the U.S. Government should increase NASA's budget in order to send government employees there anytime soon.

So it's not so much where we go that is important, but the WHY and WHEN.  Answer those and the WHERE will be obvious.
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 gospacex

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Re: Should NASA refocus on returning to the Moon?
« Reply #348 on: 03/07/2017 09:52 PM »
I think the Moon is the only logical choice as a destination for the next several decades at least.  [...] it has mineral resources that can provide oxygen, metals, water and protection.
OTOH it lacks carbon, nitrogen, sulfur, chlorine and other volatiles. Hydrogen availability is questionable.
You need carbon and hydrogen to produce any sort of plastics, oils, paints, solvents. Many of them also require nitrogen and/or sulfur. Fertilizers need nitrogen. Chlorine is widely used in industry.

WMB was speaking in terms of a few decades. It will take a long time before there's enough industry on the moon (or anywhere else) to convert basic hydrocarbons (CO₂, methane, etc) into the full range of complex plastics, paints, solvents, etc

So, the answer for future Moon colonists "why the hell did we build a colony on a body where a lot of essential materials simply can't be made from local materials?" will be "we did not realize that future will occur"? I thought after Y2000 problem we learned that lesson.
« Last Edit: 03/07/2017 09:53 PM by gospacex »

Offline gospacex

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Re: Should NASA refocus on returning to the Moon?
« Reply #349 on: 03/07/2017 09:55 PM »
I think the Moon is the only logical choice as a destination for the next several decades at least.  It's close for both travel and communication times, it's a stable platform, it has mineral resources that can provide oxygen, metals, water and protection.

OTOH it lacks carbon, nitrogen, sulfur, chlorine and other volatiles. Hydrogen availability is questionable.

You need carbon and hydrogen to produce any sort of plastics, oils, paints, solvents. Many of them also require nitrogen and/or sulfur. Fertilizers need nitrogen. Chlorine is widely used in industry.

I think you might find all that in the polar crater deposits - even hydrogen, mostly bound in water. These polar craters are really cold, colder than the surface of Pluto, and even if the volatiles are intermixed with some dirt, it should be easier to get them there than to bring them in from the Earth or somewhere else.

I propose that we should check this before we commit to Moon colonization effort. Because what if polar deposits are _not_ as good as we hope?

Offline RocketmanUS

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Re: Should NASA refocus on returning to the Moon?
« Reply #350 on: 03/08/2017 04:33 AM »
Can we have our cake and eat it too?
Fund both SX and ULA for the new hardware to the first few new Lunar exploration missions.

Jon Goff speculated about combining SpaceX/ULA architecture. Sx carries the monkeys in Dragon, ULA launches the lunar lander (XEUS) and ACES TLI/TEI-booster.

http://selenianboondocks.com/2017/02/random-thoughts...

Functionally "single-bidder" by FAR standards -- since each contractor is exclusively supplying a discrete component -- while actually funding both systems to increase launcher availability for other missions.
Both SX and ULA to have tankers, so both develop in-space propellant transfer. Both use LOX, ULA uses LH2 and SX uses LCH4 for fuel. That was to seed both companies.

Masten Space Systems could develop a block I LH2/LOX horizontal lander and SX could develop a block I LCH4/LOX horizontal lander. Block I takes it's self from LEO to Lunar surface with about 1,000 lb of cargo ( small version of Athlete ). Later once SX and ULA have tankers block II could land more mass or crew. SX with new LCH4/LOX US could take Dragon to LLO and Earth return. ULA's new Vulcan/ACES could send Orion to LLO and Earth return.

We don't need to put all or eggs in on basket, diversify. In=space refueling is what both companies would need for a future Mars Mission, so this would also seed for Mars.

Block I landers don't need in-space fueling, so they could be developed first and get a rover ( small version of Athlete ) on the moon soon.

I rather have two companies that could possible be ready for commercial missions to the moon. If one companies launcher is grounder for a time the other could still provide rides to Lunar. If the lander or capsule of one company is grounded the other company could supply. This is not just a return to the moon but possible commercial use of the moon. We need more than one supplier. One delivering the lander and the other the capsule does not give a back up or choice for possible future commercial customers. And SX has two east coast launch sites for F9 to handle multiple launches in a short period of time. Once DIVH is retired it might be possible for ULA to add another pad for Vulcan if they have the flight rate for it in the future.

So moon could be first while developing needed tech for Mars and still have crew on Mars by 2030.

Offline Bynaus

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Re: Should NASA refocus on returning to the Moon?
« Reply #351 on: 03/08/2017 04:49 AM »
I think the Moon is the only logical choice as a destination for the next several decades at least.  It's close for both travel and communication times, it's a stable platform, it has mineral resources that can provide oxygen, metals, water and protection.

OTOH it lacks carbon, nitrogen, sulfur, chlorine and other volatiles. Hydrogen availability is questionable.

You need carbon and hydrogen to produce any sort of plastics, oils, paints, solvents. Many of them also require nitrogen and/or sulfur. Fertilizers need nitrogen. Chlorine is widely used in industry.

I think you might find all that in the polar crater deposits - even hydrogen, mostly bound in water. These polar craters are really cold, colder than the surface of Pluto, and even if the volatiles are intermixed with some dirt, it should be easier to get them there than to bring them in from the Earth or somewhere else.

I propose that we should check this before we commit to Moon colonization effort. Because what if polar deposits are _not_ as good as we hope?

It has been tested. From Clementine through LCROSS. You can always test more, of course, but it is clear that there is plebty of volatiles at the poles. Plus, like I said, you have the regolith which can be baked for volatiles.

Offline Paul451

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Re: Should NASA refocus on returning to the Moon?
« Reply #352 on: 03/08/2017 09:48 AM »
Just because we can find building materials doesn't mean we have all we need to set up shop on the Moon.
Sure it's close, but absent living at the poles

I took that to be the standing assumption these day. What else is there?

Which brings us back around to asking WHY NASA should refocus on returning to the Moon?

It will be useful, or it won't.

If it's not useful, it's a people on the moon for the sake of having a People On The Moon. Which will survive only as long as that is a shiny-new-thing, plus a little longer due to corporate-lobbyist-driven political inertia. And then it will end, leaving nothing of significance or value. Apollo on sleeping pills.

At least the journey to Mars holds the possibility that we'll find life there

And if we send humans to look for that life, we'll never know whether it's genuinely Martian, or just a contamination. Sending humans is a terrible, terrible way to do that kind of search.

But even if that wasn't the case, unless the price of launching and operating humans in space plummets, it will always be cheaper to send machines.

(Which is why NASA's sole HSF goal should be lowering the price of accessing and operating in space. Do that and any other goal just dropped out. Nothing else in HSF matters, anything else is merely pushing that goal further away.)

and Mars is the most Earth-like planet that is close-by.

Not enough to waste meaningful amounts of treasure on.

So it's not so much where we go that is important, but the WHY and WHEN.  Answer those and the WHERE will be obvious.

Lower the cost of getting humans in space, and the cost of operating once there, and it doesn't matter why people want to do things, or where they go to do them. It will just happen, even if the reasons are stupid. Over time, the stupid things fail, and the smart things will be self-sustaining, enabling yet more things. And you don't have to pick winners in advance, you don't have to be able to tell the stupid from the smart, you just lower the price to the point that people can waste their own money doing stupid things in space and see what accidentally turns out to be smart.

Offline Paul451

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Re: Should NASA refocus on returning to the Moon?
« Reply #353 on: 03/08/2017 09:55 AM »
WMB was speaking in terms of a few decades. It will take a long time before there's enough industry on the moon (or anywhere else) to convert basic hydrocarbons (CO₂, methane, etc) into the full range of complex plastics, paints, solvents, etc
So, the answer for future Moon colonists "why the hell did we build a colony on a body where a lot of essential materials simply can't be made from local materials?" will be "we did not realize that future will occur"? I thought after Y2000 problem we learned that lesson.

Look at the number of processing steps required for a single type of plastic, paint, solvent, etc, from even the higher hydrocarbons. Then add the steps necessary to get to that beginning complex hydrocarbon from simple volatiles like CO₂ and water. Then multiply by all the hydrocarbon based chemicals the base/habitat/colony would need, which seem to all require their own independent and unique industrial path.

It will be a many, many decades before there's enough demand in the colony to justify local production of those kinds of materials, even if they had crude oil pooling around their feet. And by the time there is that scale of settlement, they'll have decades of waste plastic and other hydrocarbons; which will serve as the seed-stock for reprocessing. That buys you another few decades.

By the time the local industry is actually ready to process raw volatiles (such as CO₂ or methane) into advanced materials (such as plastics), it's so far in the future that there's no way to know what developments have been spawned by the other resources made available from the moon. (Fuel, for example.)

There might be a thriving trade with settlements out in the carbonaceous asteroids. (Or alternatively, there might be enough debris from C-type impactors on the moon itself, just as there's elemental metal from M-type impactors.) Or it might turn out that there's enough carbon monoxide mixed with the polar water, essentially a waste product of the fuel/air/water production, to be transitioned into feedstock for processing (perhaps initially as methane for fuel).

Or rapid development outwards in the solar system might have bypassed the early lunar settlements entirely. They may be abandoned. Or reduced to a few heavily supported scientific outposts.

It's so far in the future that we have no way of knowing which direction things will go. Getting hysterical over it today is pointless.

Offline Paul451

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Re: Should NASA refocus on returning to the Moon?
« Reply #354 on: 03/08/2017 10:01 AM »
I propose that we should check this before we commit to Moon colonization effort. Because what if polar deposits are _not_ as good as we hope?
It has been tested. From Clementine through LCROSS.

The data from Clementine was apparently pretty low grade, the two main instruments on LCROSS reportedly contradicted each other.

It's clear there's water ice. Lots of water ice. It's less clear what else is in there. Ground-truths are necessary before you even consider designing systems to extract even just the water.

That said, it should be scientifically useful. Potentially a chronologically sorted record of hundreds of millions of years of impacts by comets and wet-asteroids. Neatly delineated by thin layers of dust from dry-asteroid impacts. Hence, physically-sorted isotopic samples from countless impactors. A priceless scientific boon.

Offline Bynaus

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Re: Should NASA refocus on returning to the Moon?
« Reply #355 on: 03/08/2017 10:22 AM »
I propose that we should check this before we commit to Moon colonization effort. Because what if polar deposits are _not_ as good as we hope?
It has been tested. From Clementine through LCROSS.

The data from Clementine was apparently pretty low grade, the two main instruments on LCROSS reportedly contradicted each other.

It's clear there's water ice. Lots of water ice. It's less clear what else is in there. Ground-truths are necessary before you even consider designing systems to extract even just the water.

That said, it should be scientifically useful. Potentially a chronologically sorted record of hundreds of millions of years of impacts by comets and wet-asteroids. Neatly delineated by thin layers of dust from dry-asteroid impacts. Hence, physically-sorted isotopic samples from countless impactors. A priceless scientific boon.

Still, if you condense the water, its relatively straightforward you will condense the more volatile stuff as well - but I agree, you can always do better by doing a more thorough investigation.

I have been thinking along the same terms, but I am not sure it will be chronologically sorted - you also have gardening by impacts at the poles which might well destroy and mix the top-layer of the deposits as it forms, and the dust from dry asteroid impacts will not easily find its way to the poles (and if it does, it will likely be strongly diluted by regolith dust ejected by the same impact). However, it might be that volatiles in lunar caves will provide some stratigraphy - protected from impacts, yet very cold, they could be the perfect archives of lunar history (unless the surrounding rock is too warm - so caves near the poles perhaps?). I always wanted to try to model that but never found the time to do it.
« Last Edit: 03/08/2017 10:22 AM by Bynaus »

Offline clongton

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Re: Should NASA refocus on returning to the Moon?
« Reply #356 on: 03/10/2017 06:53 PM »
What would we do on the moon? Think L-O-N-G  T-E-R-M.

I would suggest that the eventual goal would be a functioning interplanetary exploration center and shipyard, where interplanetary spacecraft are built, launched, recovered, refurbished, restocked, re-crewed and launched again. Absence of the deep earth gravity well will eventually enable far more efficient spacecraft designs that what we can build on earth, work real hard to put tiny pieces of it into LEO and then assemble in zero-g. Fighting only only 1/6 g it shouldn't be much problem to outfit engines strong enough to lift the vehicles into LLO before mission departure.

This is, of course, a long term vision, but one that I believe, if you think long term, is practical.
« Last Edit: 03/10/2017 06:58 PM by clongton »
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Offline Paul451

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Re: Should NASA refocus on returning to the Moon?
« Reply #357 on: 03/11/2017 03:44 AM »
[polar ice, because "science!"]
but I agree, you can always do better by doing a more thorough investigation.

I don't think it's just a matter of better. I doubt you could design ISRU equipment without a detailed understanding of the material. I mean, bake a kg and collect a gram, sure. But nothing at the efficiency required for realistic production rates. Too many unknowns.

I am not sure it will be chronologically sorted - you also have gardening by impacts at the poles which might well destroy and mix the top-layer of the deposits as it forms

I agree. Hence "potentially". The saving grace is that micrometeorites are limited in their impact depth (a la Newton's rule of penetration depth), and larger impacts are randomly uneven. Micrometeorites probably won't mix a full layer depth, larger impacts will leave sections intact, and different sections will overlap, allowing a continuous column to be recreated.

Potentially.

(I'm really curious how far back this could go. How stable is the moon's long term axial alignment? Could this go back billions of years?)

and the dust from dry asteroid impacts will not easily find its way to the poles (and if it does, it will likely be strongly diluted by regolith dust ejected by the same impact).

I didn't mean that the dry impacts have usefully layering of each impact. What I meant was that the small amounts of dust kicked up from large impacts, which settle out everywhere on the moon, will serve to delineate the much rarer volatile-rich impacts (especially comets) from each other. Ie, thick layers of the rare comet impacts separated by thin layers from the much more common dry impacts.

You see this in deposit stratigraphy on Earth in, say, lakes. A broad winter layer (lots of run-off sediment) each season, separated by a thin layer of the summer dust blowing over the lake itself. Produces a nice neat, thin, boundary line between winter layers.

(Not sure if I've explained my reasoning any better.)

However, it might be that volatiles in lunar caves will provide some stratigraphy - protected from impacts, yet very cold, they could be the perfect archives of lunar history (unless the surrounding rock is too warm - so caves near the poles perhaps?). I always wanted to try to model that but never found the time to do it.

If you do, please do Mars lava-tubes as well. I've wondered whether they will serve as water-ice traps, analogous to the polar caps, but occurring in more accessible parts of Mars.

(Anything underground tends to maintain a more constant temperature which will be is the average of the surface temperate. The average temperature of equatorial Mars is usually given as -55℃, which is above the boiling point of CO₂. Hence you might see water freeze out, but not CO₂, creating a nice concentrated resource for settlers.)

Offline Paul451

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Re: Should NASA refocus on returning to the Moon?
« Reply #358 on: 03/11/2017 04:03 AM »
I would suggest that the eventual goal would be a functioning interplanetary exploration center and shipyard, where interplanetary spacecraft are built, launched, recovered, refurbished, restocked, re-crewed and launched again.

If there was an industry on the moon, created for some other reason, I can imagine a ship-building industry getting established, but why would operational ships return to the moon for restocking and recrewing?

You don't dry-dock a ship for routine maintenance, hell even fairly significant maintenance is done at ordinary wharfs. And you sure as hell don't dry-dock just to swap out crew and take on supplies.

Fighting only only 1/6 g it shouldn't be much problem to outfit engines strong enough to lift the vehicles into LLO before mission departure.

It's not the "strength" of the engines (well, not just that), it's the fuel. Only chemical engines can land on the moon, and they are very wasteful. At over 2km/s to land, another 2km/s to take off again, even hydrolox engines burn a lot of fuel.

Offline AncientU

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Re: Should NASA refocus on returning to the Moon?
« Reply #359 on: 03/12/2017 12:02 AM »
Refits of in-space vessels should be done at EML-1 (or maybe EML-2).  Easily accessed from Earth, Moon, interplanetary, minimal energy to maintain position, top of gravity well for departure (w/ Oberth burn advantages).  In-spac ship assembly could also be done here -- avoids ships having to be structurally strong enough (and small enough) to depart Lunar surface as well as eliminating the delta-v penalty discussed above.
"If we shared everything [we are working on] people would think we are insane!"
-- SpaceX friend of mlindner

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