Since this topic has been lightly discussed before in various threads, I would like to dedicate this thread to this one subject, testing equipment for planetary missions. Please restrict comments to this topic.

It has been suggested that our Moon should be used to test equipment to be used on other planets, specifically Mars. This has been suggested many times, and even NASA has been credited with the idea, but I have yet to see any detailed credible reason for testing on the Moon.

On the other hand, I find a many valid reasons to do most of the testing for Mars here on Earth. Briefly:

a. Testing could be done far less expensive here on Earth.
b. Testing could be done far safer here on Earth.
c. Testing could be done much faster, and problems corrected much faster here on Earth.
d. The day/night cycle is almost identical.
e. The temperature ranges are relatively similar to certain regions on Earth.

For comparison, here are some basic statistics.
Mars: Gravity is .38 of Earth's, Moon: is .17 of Earth's
Mars: thin atmosphere of CO2, Moon: none
Mars: Large amounts of water at poles and possibly elsewhere, Moon: Probably none
Mars: Plenty of Carbon for growing food, Moon: virtually zero.
Mars: 44% of the harmful radiation that the Moon receives.
Mars: usable wind for wind power, Moon: none
Mars: Day 24 hours 37 minutes, Moon: four weeks
Mars: has two moons, Moon: none

IMO, testing for any and all equipment to be used on Mars can be done here on Earth. Every aspect of Mars, except the .38G gravity, can be simulated using sites such as Devon Island, or in low pressure domes and structures using climate control equipment.

I am interested to see what testing others think can be done better on the Moon, not even counting the cost/safety/time differences.

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Well, I think you have a couple small errors there. The Martian day is slightly longer than Earth's, not shorter. The wind on Mars is probably not capable of being harnessed because of the low pressure. It might be able to pick up dust and skip sand, but it probably can't spin turbines.

You should add that Moon dust is especially troublesome and has no martian analog. That one issue might be enough to make it a bad testbed. Testing mechanical devices in a lunar dust environment makes as much sense as testing them in a Hawaiian hot lava bed, it adds a critical damage characteristic that is not representative of the deployment environment.

The only compelling reasons to test on the Moon are psychological, not physical.

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"What you think you thought you saw you did not see." Agent J, MiB - Manhatten Bureau

Thank you, I corrected the data.

The wind is capable of creating a global dust storm. I am sure it can be harnessed with wind turbines. The Martian atmosphere may be thin, but it extends up a long ways.

Actually, Martian dust is very fine, making it a different problem than the abrasive dust on the Moon.

Please elaborate.

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The atmospheric density on Mars is at best about 1/50th of the density on earth, so for a given size wind turbine you get 1/50th the power. And what does the upper atmosphere have to do with this? The higher you put your turbine the less density and power.

That's basically what he said

Anyways I agree with both of you guys there is no point in testing equipment for mars on the moon because they are so different and better test sites can be found on earth or created in laboratories. Some testing will have to be done in space or on mars, like EDL systems.

However, the wind on Mars blows at up to 200mph. The force created by wind increases as the square of the velocity. Wind turbines on Mars would be a practical auxiliary power source, providing power when the wind was blowing up the dust and obscuring the sunlight from the solar panels.

Not exactly. I was pointing out what those differences are. Martian “fines” create their own special problems, especially with seals.

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The fact that the Martian atmosphere extends higher also means that, as you gain altitude, the density does not decrease as rapidly as on Earth. All lf the weather on Earth occurs within the first 7 miles, but on Mars, the dust storms nearly reach the top of Olympus Mons which is 15 miles high. That means that you can put wind turbines at relatively higher elevations on Mars without losing as high a percentage of the force of the wind.

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It does on Earth from time to time as well.

Given the 1/2 p v ^2 equation for dynamic pressure:

Peak turbine performance on earth is typically at about 33 mph ( 15m/sec )

1.23 kg/m^3 x 15 ^2 = 138 Pa

To match that on Mars - with atmospheric pressure of 0.02 kg/m^3 - you would have to have...

138 = 1/2 * 0.02 * x^2

117 m/sec - 261 mph.

So - to get peak turbine performance as produced by 33 mph winds on Earth - you would require 261 mph winds on Mars. The average wind speed on Earth ( about 6.6 m/sec ) would have to be matched by Martian wind speeds of 51 m/sec (114mph)- which is over the peak value I have seen for observed Martian winds. If you think think the very best way to spend mass budget to the surface of Mars is with wind turbines - you're mad. That they would generate SOME electricity is a certainty, some of the time - but it wouldn't be a lot and they make nowhere near as much sense as they do on Earth. What about when the wind stops? It will from time to time, for periods of time that might be anything between minutes and days - and it's not a case of 'turn off the lights' - it's a case of people dying because of failed life support. Every single iota of power you intend to generate via turbines HAS to be match by non-environmentally variable means ( i.e. small RTG derived platforms such as those proposed for Mars Direct ). If you've got the power you need from those, then why both with turbines at all.

I agree, however, that the moon offers little usefull analogy to the Mars in terms of exploration systems testing. Things the Earth can't provide however - are the UV radiation - the temperature swings - the air pressure - and the simple reality of being 250,000 miles from home when something breaks down. The argument of going to the Moon so as to make going to Mars easier is without merit. But the brutal fact is that there is currently, political will to revisit the moon -and none to visit Mars. When GWB announced the VSE, I think his words describing the lunar visits as a stepping stone to Mars was a programmatic one, not an engineering or practical one.

Doug

Doug,

Give him a break! Of course the air is thinner on Mars--but so is the sunlight! Everything is less good on Mars. That's why Mars is Mars and Earth is Earth. Get used to it. . . .

The only thing that works the same is nuclear. Is that what you propose?
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Mental,

As for testing on the Moon. What is the argument? That we need to blow off the Moon so we can go to Mars? That we can't do both somehow? Like we have to blow off the Azores so we can colonize Massechusetts? What's wrong with the Moon? Why do you hate it so much?

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"Ignorance more frequently begets confidence than does knowledge" -- Charles Darwin

The differences are not "less good" enough to rule them out. The main objection to nuclear on Mars is that it's heavy, so shipping it there is expensive in energy. Solar, as the rovers demonstrate, works and is low-maintainence, the only problems are dust and night. Wind turbines can work on Mars, according to the number-crunchers who have researched it. In terms of reliability and maintainance, it's somewhere between nuclear and solar. No doubt all three will get some use on the red planet.

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"If this were play'd upon a stage now, I could condemn it as an improbable fiction."
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Illuminati's Razor-The most complicatedly evil answer is usually the most correct answer. - Fazor
"Every book is a children's book if the kid can read." - Mitch Hedberg
"Distance doesn’t matter much in space, where if you just start a thing off with the right kind of shove, sooner or later it will get where you want it to go." -Frederik Pohl, Mining the Oort

The efficiency of any wind turbine depends on many factors, including the shape of the blade and the type of turbine. Designs are chosen to maximize efficiency for given location.

Strawman. No one is claiming to “match” or “compare” Earth with Mars, except perhaps you. They are two dramatically different atmospheric environments and each will employ the best design for the location.

Ignoring the Ad Hominem…….. That is another Strawman. I never said, indicated, insinuated or alluded to any such thing.

Once again, Strawman, comparisons with Earth in this respect are irrelevant.

I strongly suspect the wind turbines will stop turning.

Good grief, your Strawman army is growing rapidly. As I specifically pointed out, ” Wind turbines on Mars would be a practical auxiliary power source, providing power when the wind was blowing up the dust and obscuring the sunlight from the solar panels.”. In addition, like most auxiliary power systems, a battery backup, a fueled generator, or a nuclear power system could be included for times when there was no sunlight or wind. There are many ways to store power, including lifting water, batteries, and flywheels.

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Reality: What a concept!……………………..><Ç(((Ç°>

Well, it looks like I'm wrong on this one, and I gladly admit it. The numbers posted by djellison show that even if it's not as good as Earth potential, there is at least some potential for wind turbines on Mars. I had expected them to just sit still in the martian atmosphere. Now, we'd have to make them lightweight and dust-resistent.

Well, djellison got my point. Lunar dust is a different problem. But I suspect that lunar dust will be more of a problem for lunar exploration that martian dust will be for Mars exploration. It's not just type of dust, but the magnitude of the problem. Equipment designed for work on mars would fail prematurely on the moon, which would make the test data useless.

Psychology in terms of both participants and the public. I'm not referring to the Moon as a Mars analog in this respect, just that the advantages in a lunar base outweigh disadvantage of the failure in analogy. The communications lag time is less, allowing for real-time communications when troubleshooting new basic space technology. Establishing an offworld base on the moon will go farther in convincing the public that a Mars colony is feasible. Overcoming obstacles in planetary colonization will be considered generic by the paying public, which will go a long way towards promoting space exploration in all its forms and destinations. If we consider business and the market as strongly driven by psychology, then generating a market for basic space tech by going to the Moon and staying will be enormously helpful in making a Mars trip and colonization later.

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"What you think you thought you saw you did not see." Agent J, MiB - Manhatten Bureau

Hear, hear. And it'll do the same for all future manned space missions and bases.

Plus, having a base on the Moon is useful in and of itself.

__________________
"If this were play'd upon a stage now, I could condemn it as an improbable fiction."
Shakespeare, Twelfth Night
Illuminati's Razor-The most complicatedly evil answer is usually the most correct answer. - Fazor
"Every book is a children's book if the kid can read." - Mitch Hedberg
"Distance doesn’t matter much in space, where if you just start a thing off with the right kind of shove, sooner or later it will get where you want it to go." -Frederik Pohl, Mining the Oort

First off, unless the metal is mined, refined, and constructed there, Mars bases will not have industrial sized 100 ft+ turbines like we have here. An array of smaller sized turbines would work a whole lot better than 1 or 2 huge turbines, and be much easier to transport there. Plus, a Mars base will be built for maximum operating efficiency as possible, not like our energy gobbling systems here on Earth, so they will not need 2 megawatts of wind power to run their systems.

I doubt that. Chances are a colony, a real colony --not a temporary space base-- will be driven by economic considerations that result in suboptimal efficiencies.

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"What you think you thought you saw you did not see." Agent J, MiB - Manhatten Bureau

Thank you. I respect you for that.

From what I have read, the Martian dust is so fine that it would be a problem in several areas. One is that it might be able to work its way into conventional seals, especially seals around rotating parts. Therefore, a new kind of seal may have to be developed. Another thing is that it may cling to clothing, much like talcum powder would, making it difficult to remove the dust when entering the habitat. It might not be healthy to bring that dust into your home. Therefore, special cleansing systems may have to be developed to remove the dust efficiently.

I understand. Education is the key to preventing uniformed emotional reactions from preventing the implementation of practical applications.

It would be preferable to get the troubleshooting phase over with before taking the equipment to the Moon. The Moon would be a really bad place to “work out the bugs”.

True. But establishing a viable colony on Mars would go a lot further.

IMO, the best role for the Moon to play in all of this is in providing processed materials for use in Earth orbit, LaGrange points, Mars orbit, and other space vehicles. The less we have to boost from Earth, the more we can explore for the same money.

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Reality: What a concept!……………………..><Ç(((Ç°>