Space Station Vs. Moon Base

Why is the idea of putting a station in orbit more appealing then putting on on the moon? I understand the want to test things in low gravity. But what about cost wise? I know that the ISS has to change it's direction every now and then to avoid random junk floating in space, and I understand it would take more fuel to get something to the moon. Is there anything more to the equation then this or is it just that the cost of getting something to the moon and back is much more expensive then maintaining an orbital station?

Thanks for your time.
 

DaveC426913

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Why is the idea of putting a station in orbit more appealing then putting on on the moon? I understand the want to test things in low gravity. But what about cost wise? I know that the ISS has to change it's direction every now and then to avoid random junk floating in space, and I understand it would take more fuel to get something to the moon. Is there anything more to the equation then this or is it just that the cost of getting something to the moon and back is much more expensive then maintaining an orbital station?

Thanks for your time.
It's a long climb out of Earth's gravity well.
It's a long way to the Moon once out.
It's a long way back out of the Moon's well. Why spend all that energy getting out of a well only to plunge back into one?

Other than access to some raw materials, what, if any, are the advantages of the Moon?
 

Nabeshin

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Other than access to some raw materials, what, if any, are the advantages of the Moon?
One that comes to mind immediately is the use of the far side for telescopic observations. I haven't the numbers but it seems plausible that construction of a scope on solid ground would be cheaper and allow us to have more aperture for a given dollar amount than deploying a space telescope.
 
Like I was saying before, I thought one advantage was that they wouldn't have to have the station change it's path to avoid junk every couple of months like they do with the ISS. I was just asking if the main reason was that it required so much energy.

And Nabeshin, apparently they are planning a far side of the moon radio telescope array specifically for the purpose to block out all the interference from Earth. It's coming no time in the near future, but it would seem your suggestion is right.
 

D H

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One that comes to mind immediately is the use of the far side for telescopic observations. I haven't the numbers but it seems plausible that construction of a scope on solid ground would be cheaper and allow us to have more aperture for a given dollar amount than deploying a space telescope.
Even better, you could construct a truly huge antenna array on the Moon.
 

DaveC426913

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I haven't the numbers but it seems plausible that construction of a scope on solid ground would be cheaper and allow us to have more aperture for a given dollar amount than deploying a space telescope.
Even better, you could construct a truly huge antenna array on the Moon.
Again I ask, what advantages does the Moon offer that space does not? Other than access to some materials, you're going to have to haul everything in and out of one more gravity-well.

You seem to be stuck in the mind-set that solid-ground somehow equates with cheaper cost. The Moon is not Earth.

A space telescope will require fewer, lighter materials and be more stable than any ground-based scope.

As for dodging debris, that is only an issue in low Earth orbit.
 
You could more easily build an array of optical telescopes designed to do interferometry on the Moon.
 

DaveC426913

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You could more easily build an array of optical telescopes designed to do interferometry on the Moon.
You mean because they would be stable wrt each other? OK, I'll grant that. That's one specific use.
 
Nasa is planning for a moon base for 2024 using the orion spacecraft they are currently desinging. I would find that building colonys on the moon would help us because we could build a moon city so it could free up some of the land on earth. Overpopulation is a threat to the survival of the human race. We also could possible use the moon as a space base to launch to mars and other plantets.
 

DaveC426913

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Yes, this is the other thing that the Moon has over orbit: long-term habitability due to gravity. But the key is long-term.
 

Nabeshin

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You're completely right about the materials part, DaveC. In looking for information about lunar-based telescopes, I found this:
http://www.space.com/businesstechnology/080716-tw-lunar-telescope.html

Which appears to be the most legitimate proposal for any such telescope.

My initial thought was that it would be cheaper to install and maintain an accurate guidance system on a stable surface than use gyroscopes such as those used on Hubble. (Just a thought, I have no information as to the relative cost of terrestrial and space tracking systems)
 

mgb_phys

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The problem with putting a telescope on the moon is that the 'day' is 14days long - so half of the time the sun is in the sky and the rest of the time the Earth is in the way.
Putting a telescope at L2 is much less of a lift and has a lot more sky available
It might be worth it for a few radio frequencies to out a telescope on the dark side of the moon where emissions from Earth are blocked.
 
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russ_watters

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Actually, stability is not an advantage of being on the moon. The moon isn't 100% stable and there can be nothing as stable as floating in space, with nothing touching the telescope.
 
Other than access to some raw materials, what, if any, are the advantages of the Moon?
One limitation of orbital telescopes is the relatively short "integration time." An Earth based scope can keep itself pointed at the same patch of sky for hours and hours -- much longer than Hubble. Conceivably, a Moon based one could do so for days and days. When the object of the game is to collect photons, time is just as important as aperture.

However, I have no idea how moonquakes throw a monkey wrench into that consideration.

Another advantage is that when the far side of the Moon is in darkness, it's really dark. I think the only kind of light pollution you have to worry about is zodiacal light (reflections from all the stuff in farther out in the star system itself).

Of course, whether or not such things justify the expense is another matter.
 

mgb_phys

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One limitation of orbital telescopes is the relatively short "integration time." An Earth based scope can keep itself pointed at the same patch of sky for hours and hours -- much longer than Hubble. Conceivably, a Moon based one could do so for days and days. When the object of the game is to collect photons, time is just as important as aperture.
It's the other way around.
A ground based observation (unless you are at the pole) is limited to one night, and because you don't want to be observing through too much air mass (you want the object high in the sky) you are generally limited to 4-6hours.
For an object outside the ecliptic (ie near North/South poles) like the Hubble Deep field you can observe continually. For a telescope not in LEO, like NGST/Kepler, you can observe most of the sky indefinitely.

Another advantage is that when the far side of the Moon is in darkness, it's really dark.
The Dark side of the moon is pointed at the sun for 14days/month - it's only 'dark' in the sense of not seen from earth (dark=unknown)
 

turbo

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Another advantage of Earth orbit is that the Earth's magnetic field shields ISS from the worst of the Sun's trantrums. We were pretty lucky during the Apollo program. We can't gamble astronauts' lives on "being lucky", and it's pretty darned expensive to loft dense shielding out of the Earth's gravity well. We'd have to be prepared to rely on "being lucky" once again if we put people on the moon to construct facilities, and start excavating caves and tunnels immediately so that we could shield those people with lots of moon-rock. Hard-rock mining is a pretty dangerous occupation. Anybody want to try it in a vacuum in low-gravity while wearing pressure-suits?
 

russ_watters

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Russ, can you this in space:

http://en.wikipedia.org/wiki/Very_Large_Telescope#Interferometry_and_the_VLTI

And, of course, what I mean is that you want to go far beyond what the VLT can do. So, you want to use more telescopes that are furhter apart so that you get a higher angular resolution and you can image objects that are much fainter.
Absolutely! In fact, that is another example of a shortcoming of the moon vs being in space. Out in space, your options for telescope placement are far less limited. You could, for example, place a telescope on the Lagrange point opposite the earth from the sun, giving you a 2 AU baseline.

Interferometry is a developing field, but space-based, very long baseline interferometers are on the drawing board, though still a ways' off.

[edit] Here's the scientific paper proposing the concept. It was funded by NASA for a while, but near as I can tell hasn't been funded since 2007. The proposal is for 5 telescopes, one at each Lagrange point: http://web.mit.edu/wsimmons/www/documents/simmons_spie2004.pdf

Here's the author's website: http://newworlds.colorado.edu/

Less ambitious space-based interferometer concepts are in the design phase and will be launched over the next 10 years or so. The success of these could be a stepping stone to the more ambitious 2 AU interferometer.
 
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mgb_phys

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But low earth orbit is nasty for electronics.
The south atlantic anomaly is a bit of the Earth's magnetic field near Brazil where the radiation belts come a lot lower. When Hubble flies through it the interference takes out some the instruments for about 20% of that orbit.
 

Redbelly98

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The problem with putting a telescope on the moon is that the 'day' is 14days long - so half of the time the sun is in the sky and the rest of the time the Earth is in the way.
Why is that a problem? There is no atmosphere to scatter the light, so just don't point the telescope directly at the sun or Earth when/if they are visible.

You could, for example, place a telescope on the Lagrange point opposite the earth from the sun, giving you a 2 AU baseline.
How would we communicate with it? Have another satellite in Earth's orbit, 90o from Earth?
 
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Another advantage of Earth orbit is that the Earth's magnetic field shields ISS from the worst of the Sun's trantrums. We were pretty lucky during the Apollo program. We can't gamble astronauts' lives on "being lucky", and it's pretty darned expensive to loft dense shielding out of the Earth's gravity well. We'd have to be prepared to rely on "being lucky" once again if we put people on the moon to construct facilities, and start excavating caves and tunnels immediately so that we could shield those people with lots of moon-rock. Hard-rock mining is a pretty dangerous occupation. Anybody want to try it in a vacuum in low-gravity while wearing pressure-suits?
How does the orion 2024 whatever program plan to address this problem?
 

russ_watters

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How would we communicate with it? Have another satellite in Earth's orbit, 90o from Earth?
You could, though if you read on, I found the proposal I was thinking of, which had 5 satellites...

...presumably one could be used to relay data from another, but that seems like a relatively minor issue to me compared with the need for precise station-keeping.
 

turbo

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How does the orion 2024 whatever program plan to address this problem?
Do you have links or references? As of now, I know of no viable proposal (even remotely) to build permanent or long-term temp-habitation facilities any place outside of Earth's magnetic field.

When W tried to polish his credentials by claiming that a goal of NASA should be to send men to Mars, every physicist should have flooded their TV outlets with estimates of the costs of the raw materials for fuel, shielding and engineering costs. At the same time, biologists and medical doctors should have been factoring in the costs of air, water, food, energy for hydroponics, etc, and lofting all that out of Earth's gravity. It's pretty apparent that we can't send our brave Marstonauts out there with years' worth of cans of Spaghettios and ramen noodles. Frankly the people in NASA (and other physical sciences) dropped the ball big-time to let the dope play "visionary scientist president".

There are huge engineering challenges that we face, not the least is low-mass, low-energy shielding systems for vessels in interplanetary space. There is also the huge cost of fuel to get stuff pried away from the Earth, and the "danger factor" that we send people and valuable payloads into orbit sitting on top of complex controlled-bombs that may or may not behave. I love Science Fiction, and a personal favorite is Babylon 5 (with Harlan Ellison consulting). Unlike some, I don't place a lot of faith in the possibility of the plot-line.
 
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For an object outside the ecliptic (ie near North/South poles) like the Hubble Deep field you can observe continually.
Oh cool! I didn't know that. That's a really interesting point. Has Hubble always had that capability or was that added in one of the repair/service missions? If I recall correctly, the WFPC can't do that.

The Dark side of the moon is pointed at the sun for 14days/month - it's only 'dark' in the sense of not seen from earth (dark=unknown)
:smile: Either you didn't understand what I wrote, or you're trying to refute something I haven't claimed. I wrote "[W]hen the far side of the Moon is in darkness, it's really dark." I was just suggesting that night on the far side of the Moon is much darker than night on Earth, and no human-generated light pollution would affect the telescope. I'm not suggesting that the Moon doesn't rotate. :smile:
 
We were pretty lucky during the Apollo program. We can't gamble astronauts' lives on "being lucky", and it's pretty darned expensive to loft dense shielding out of the Earth's gravity well.
That's a really good point, but I think you're articulating the reasons why manned spaceflight's days are numbered. Our robots will be doing all the exploring and telescope building. I just wonder if they'll be annoyed at being asked to share with us what they learn.
 

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