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 87814 times)

Offline Paul451

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Re: Should NASA refocus on returning to the Moon?
« Reply #420 on: 10/10/2017 07:21 PM »
and no wasting of precious lunar water.
Aren't the estimates of polar ice on the order of several thousand years worth of daily SLS launches?
It's not just the availability of water that is a concern

Blasphemer said "precious".

but the amount of energy that would be required to free it.

From... ice?

2kJ per kg per Kelvin, usually.

[edit: stupid typo]
« Last Edit: 10/10/2017 07:22 PM by Paul451 »

Offline Coastal Ron

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Re: Should NASA refocus on returning to the Moon?
« Reply #421 on: 10/10/2017 08:37 PM »
but the amount of energy that would be required to free it.

From... ice?

2kJ per kg per Kelvin, usually.

Meaning where does all that energy come from? Power sources require their own infrastructure, and the cost of getting them there and set up can be high too.

Which I think is not related to the question at hand, since it's very unlikely that the U.S. would decide to go beyond a basic outpost on the Moon as a first goal.
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 Paul451

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Re: Should NASA refocus on returning to the Moon?
« Reply #422 on: 10/10/2017 10:36 PM »
but the amount of energy that would be required to free it.
From... ice? 2kJ per kg per Kelvin, usually.
Meaning where does all that energy come from?

If the base is outside of the region of permanent shadow, probably the sun. Melting ice is hardly a difficult problem. The rest of fuel production, yeah, energy requirements out the wazzoo. But just melting ice?

Which I think is not related to the question at hand, since it's very unlikely that the U.S. would decide to go beyond a basic outpost on the Moon as a first goal.

If we're talking "likely", NASA/Congress is unlikely to do anything beyond sorties. Flags'n'footprints. Nothing long term, nothing that lasts beyond local sunset. So why discuss anything?

Because you aren't going to have an "outpost", however small, outside of a tiny number of awkward locations at the Sth Pole without a steady night-time power-source like a nuke.  And if you have a nuke, the energy problem is solved wherever you are.

Even at those awkward but well-lit polar sites, you still experience a few days in a row of "night" (not as many, not as often, but some), so without a nuke you'll need buckets of solar and plenty of battery storage. Thankfully, modern solar is cheap/light.

Your big issues will therefore be daytime cooling and the amount of fuel required for transport to support the base.

... Why if only there was a nice pile of cold stuff near those sites which you could dump heat into and it was also stock for producing fuel. Wouldn't that be handy?

[edit: Wouldn't it be even better if that same pile of cold stuff was also of potentially extraordinary scientific importance, and hence the perfect place to locate a science-centric base anyway?]
« Last Edit: 10/10/2017 10:37 PM by Paul451 »

Online TrevorMonty

Re: Should NASA refocus on returning to the Moon?
« Reply #423 on: 10/10/2017 11:53 PM »
Conversion of 1kg water to LH and LOX takes about 7kwhr.  For polar site with 80% sunlight, it works out to be about 1000kg per year for 1kw array. This doesn't cover energy required to extract water from polar craters, but that should be significantly less and maybe able to use surplus heat from the electrolysis process.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20010039031.pdf                  
« Last Edit: 10/10/2017 11:57 PM by TrevorMonty »

Online AncientU

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Re: Should NASA refocus on returning to the Moon?
« Reply #424 on: 10/11/2017 03:11 PM »
Yeah - the 3x SLS launches per year would be the maximum we could ever expect without a major funding boost; making more launchpads, Crawlers, service towers and other infrastructure available, plus upgrading the VAB would be the only way to get better than 3x launches. But 2x SLS launches per year - the accepted 'norm' for now would be okay if the other launches for cargo, propellants etc were done on Commercial rockets such as the Vulcan, Falcon Heavy and New Glenn. 2x only crewed Orions per year should be maxed out for mission endurance; meaning lunar surface missions of at least 14 Earth days to make the expense worth it.

...better than a cold, hard nothin'...

Not really.  If we are going back to the Moon to do 'sorties' -- let's not go.

The reality is, 2-3 SLS flights per year will break the bank -- assuming that it is even feasible to make 10-ish RS-25Es per year, fab 2-3 Orions, prep 2-3 launch vehicles, etc.  Anyway, that won't happen until 2030s...

Several new paradigms are needed:
1. We go back to the Moon to stay.  24/7, 28-day day and all, year after year.  Serious exploration and prospecting a hundred or a thousand kilometers around is the real work to be done.
2. Lunar Village is constructed and expanded by surface equipment and physical labor of the people on the Moon; it's not just a few sardine cans plunked down... where NASA astros hang out for 14 days between rover jaunts around the immediate vicinity.
3. Commercial vehicles, landers, habs, etc. make up the bulk of the effort.  NASA role is more a conductor or choreographer, not playing all the instruments or dancing all the dances.
4. Fuel-rich architecture is a fundamental requirement... as is reusability.  Limitations of one-shot hardware must be overcome.

It is not worth going back to the Moon if we simply 'practice' those activities that will keep us from going further.

This.

Quote
JAXA plans to construct a fuel plant at the lunar south pole & include a human lunar stay of 500days! for a crew of 4 #leag2017 #MoonVillage

https://twitter.com/Capoglou/status/917789236023255040
« Last Edit: 10/11/2017 03:12 PM by AncientU »
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Offline Paul451

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Re: Should NASA refocus on returning to the Moon?
« Reply #425 on: 10/11/2017 05:39 PM »
This doesn't cover energy required to extract water from polar craters, but that should be significantly less and maybe able to use surplus heat from the electrolysis process.

Logically you'd use the surplus heat from the refrigeration process. If you have an extremely low temp heat-sink available, it would be foolish to not take advantage of that to cool the prop gases as much as possible.

[Aside: I suspect they'd start with LOx, dump the hydrogen. Gives you the maximum mass saving for the landers for the minimum infrastructure cost.]

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