The Moon or Mars:

Discussion in 'Astronomy, Exobiology, & Cosmology' started by paddoboy, May 20, 2015.

  1. cosmictraveler Be kind to yourself always. Valued Senior Member

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    Lets clean up the Earth first for it is suffering greatly from the ecological disasters that has befallen it due to the greed and ignorance of humankind. We can still research ways to go to Mars but lets us not screw up another planet as we already have our own planet.
     
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  3. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    I agree; and more importantly so do the vast majority of tax payers. If trillions of their money are to be spent, they want the benefits to be here on Earth. Why even if technically feasible to colonize Mars, it will not be done, as I explained earlier, in post 12 here: http://www.sciforums.com/threads/the-moon-or-mars.147640/#post-3300581
     
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  5. paddoboy Valued Senior Member

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    Since you two are going to beat that old horse again, let.s state the obvious....
    Why would anyone on their right mind suggest that our spacefaring progress be halted, considering the benefits and knowledge it has already obtained for mankind, and of course wouldn't it be a lot better to contain and eliminate all militaristic "ventures" here on Earth and the death, disaster, hunger, famine that these militaristic "ventures"bring. Now how much money would that save for cleaning up our planet?

    And to say that we will not colonise Mars without any time frame, suggests of course, that we will never colonise Mars.
    I find that extraordinary. Of course in time it will be done, for the reasons I have explained many times.
     
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  7. paddoboy Valued Senior Member

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    I totally disagree with you, and find the reasons you went into as astonishingly weird.
    I notice in all your pessimistic scenarios, you never mention time.
     
  8. cosmictraveler Be kind to yourself always. Valued Senior Member

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    The thrust of my message is that spending billions of dollars on a trip to Mars isn't prudent when our own planet is in a disaster. Research is needed before any Mars trip is done and that's all that should be done for the time being. Notice how I did not say that we should not go to Mars but only to prepare for going. They need to send a craft to Mars and land then fly back to Earth autonomously before humans go there to insure that going there and returning to Earth is feasible.
     
  9. paddoboy Valued Senior Member

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    The thrust of my message is that all the research is being done, and it is a progressive exersise. Again, I would suggest the greatest benefit would be obtained by a united International effort.
    I sympathise with our problems on Earth.....I also do my small part in alleviating that. Myself and my wife sponsor a child in Africa for starters.
    I just get terribly annoyed that when space exploration is discussed, people continue to raise the earthly problem scenario.
     
  10. billvon Valued Senior Member

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    We should do both. We should clean up our planet AND explore space. In some cases we should do both at the same time (i.e. solar power satellites.)
     
  11. billvon Valued Senior Member

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    We've got one - Curiosity. (Well, the size and weight of a Versa rather than a Hummer, but same self-driving car packed with instrumentation.)
     
  12. paddoboy Valued Senior Member

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    http://www.spacedaily.com/reports/The_Moon_or_Mars_Flawed_Debate_False_Choice___Part_Two_999.html

    The Moon or Mars:
    Flawed Debate, False Choice - Part Two


    New technologies allow us to go back to the Moon at a fraction the cost of Apollo, and now, even private efforts like the Google X Prize contestants are underway to land and execute exploration missions there. There is even a private venture to establish a lunar observatory called the International Lunar Observatory Association(ILOA). NASA has not turned a blind eye to these activities. The Pacific International Space Center for Exploration Systems(PISCES) and their International Lunar Research Park initiative have been executing some groundbreaking simulations here on Earth, and NASA is looking at ways to integrate all these activities under a synergetic program umbrella at the Space Portal, a program developed at NASA Ames Research Center to facilitate such innovation and commercial interaction.

    Now that NASA's Orion spacecraft is nearing commission and the large Space Launch System is nearly built, all eyes will be on building a lander that can service extraterrestrial surfaces. Rather than build it from scratch, NASA might do well to look at the effort well under way at Spacex and at Blue Origin, that has proven it can do wonders with small business budgets and is about to land and reuse the first stage of its Falcon and New Shepard launchers. This technology lays the foundation for both lunar and Mars landers and can greatly speed up development.

    extract:
    Two generations of our best and brightest engineers, now bordering on three, since Apollo, have spent their lives waiting to execute ambitious missions beyond low Earth orbit. Can we continue to postpone missions till we get all the right "good to have" technologies in place, as is the case for Mars, or do we execute missions that we can right now with existing technologies, as is the case for the Moon? It is important to remember that leading edge technologies tend to evaporate, if they are not put to good use in a timely manner.
     
  13. cosmictraveler Be kind to yourself always. Valued Senior Member

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    As well they should. Before going to other planets let us be certain we have our own to return to.
     
  14. billvon Valued Senior Member

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    That's great! Let private industry take over Moon exploration and concentrate public funding on Mars.
     
  15. orcot Valued Senior Member

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    Altough I would rather go to Mars I would choose the Moon for the following reasoning.
    - http://en.wikipedia.org/wiki/Shackleton_(crater) Shackleton crator, Near the moons South pole it has gentle slopes with peaks that are illuminated 80% of the lunar year and debts that haven't seen the sun in millenia and contain hydrogen component (not sure if it's water tough).

    - Because of the distance between earh (moon) and mars you would recieve roughly 2 times more energy at the moon as on mars and because it's illuminated (on average) 80% of the time (instead of the 50% on mars) Makes that the same solar array on the moon and mars would work at 260%. so you can bring less off them.
    - Delta V, it reqruires less delta v to reach then moon then Mars meaning you can either bring more or make the mission cheaper.
    - The (lack of) atmosphere. Altough Mars technically has a atmosphere by definition it's actually a low vacuum http://en.wikipedia.org/wiki/Vacuum#Measurement. That's not really useful on the surface a lack of atmosphere would mean that the solar panels would reduce maintenance (solar cells will remain clean, the soil ones it is compacted will not be as dusty).
    - Travel time is short the apollo travel time was roughly 3 days in stead of 180 days to mars meaning the accomodations could be much simpler, you also won't end up with atrophied people but healthy people that can do their job starting the first day.
    - The communication distance is short. Altough it never gets mentioned theirs robonauts, robots that can be teleoperated from earth meaning some of the landing crafts can be 1-way greatly reducing the costs. It also reduces the essential needs of the base. Whilst humans can outperform a robot, advances are being made and the astronauts eventually returns to earth whilst the robot could opperate for years.

    But that's yust a way of saying that it is easier to set up and maintain a base on the moon in stead of Mars, it doesn't say what we could do onces we are there.
    - Minnerals (well let's get it out of the way helium 3 is interesting to some people altough we won't mine it inmediatly). Hydrogen is much more interesting, if we could mine it we have a source of rocket fuel and water, if we can not find the hydrogen, we can still send up the oxygen part (oxygen makes up 80% of the mass of water). Basicly every rock on the moon contains oxygen and it's extracteble.
    - Science Shackleton itself is a ideal location for certain telescopes having a ground crew would be interesting
    - Energy the moon has a large surface area and no weather if solar panels could be produced it couls beam energy to earth or space.
    - Development of habs many things could be learned from setting up constructions on the moon.
     
    Last edited: May 25, 2015
  16. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    On (1): Please pick one of the reason I have given and tell why it is not valid.
    On (2): When something is IMPOSSIBLE having more time to try does not help. I. e. no reason for me to qualify with phrase like: "Not in next 10,000 years, anyway."

    Before making more totally ridiculous assertions about how micro-technology will solve the cosmic ray problem, please get a little understanding of how cosmic rays inter act with matter by reading this post: http://www.sciforums.com/threads/lo...nd-the-human-brain.145938/page-2#post-3301445
     
    Last edited by a moderator: May 25, 2015
  17. billvon Valued Senior Member

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    True, it's an interesting crater. But we can explore that (and should) with unmanned landers first.
    A few errors here. First, the Moon gets sunlight half the time on each face just like every other planetary body in the Solar System. (Mars too.) You may have misheard a quote by someone who said that if you had a rotating solar array on one of the Moon's poles you could get sun almost 100% of the time, which is true - since the Moon has almost no axial tilt compared to the Sun, you just have to spin the array to get power most of the time. Overall, Mars gets about 60% of the insolation as we do here on Earth.
    Definitely not. Both missions have to get to orbit. Both missions have to break orbit (and it takes almost the same delta-V to break orbit for the Moon than it does for Mars.) However, once you are en route to Mars, you don't need much more fuel. You will aerobrake, then deploy a parachute, then use a ten second burn to decelerate you to landing. For the Moon, you have to burn to kill all your velocity you picked up approaching the Moon.
    The Martian atmosphere:
    1) Shields astronauts from radiation (although nowhere near as well as Earth's does)
    2) can provide aerobraking, thus greatly reducing fuel requirements
    3) can allow for powered lifting flight, making exploration a lot easier
    4) can be used to create fuel from hydrogen
    You can spin the upper stage/lander on a cable and provide weight for the astronauts.
     
  18. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    That is true, but I doubt you would get power from solar cells there very many earth days if the panels are like those used on Earth; and even if you could it would be with much lower efficiency and greater cost than system I have described several times during the last 5 or so years - even in this thread, at http://www.sciforums.com/threads/the-moon-or-mars.147640/#post-3300416 is a brief summary, quoting from one of the older posts. Ironically near the pole is where my system would NOT work.

    It is the nature of solar cells that they MUST absorb most* of the solar photons yet only can convert on small part of their absorbed energy into electrical out put. For simple (and much cheaper) one layer cell, using silicon's band gap the theoretical limit on conversion efficiency is 21%. In practice, they do very well to get half that.

    I.e. about 90% of the energy they receive is degraded into heat, which without many more times their area of a "one side black / one side mostly shinny radiator" would destroy them thermally. This relatively huge heat radiator would also need to rotate to keep the shinny side always pointing at the sun too. Probably best design is each cell is "locally cooled." I.e. individual cell are widely separate one from another. There would be no cooling atmospheric convection as on earth. That destruction is easily done by atomic diffusion, which is much more rapid as they get hot.

    The fraction of the area covered by cells will determine on how long the cells will survive thermal diffusion destruction. I don't have any data on the cell life vs. temperature, but the T^4 limit on getting rid of about nine times more energy by radiation than the electrical energy produced at an operating temperature designed for one month life of the cells, I guess, is that the solar cells occupy less than 5% of the rotating panel (the entire "back side" of which is the black radiator.)

    *At great expense, it is possible to coat the side of cell facing the sun with a dozen or so each PRECISELY thick, layers of alternating index of refraction so that it becomes a wave length selective filter - Lets the photon with the band gap energy pass thru and others are reflected back towards the sun. That would let only the useful photons into the interior of the solar cell, but increase the cost at least 10 fold.
     
    Last edited by a moderator: May 25, 2015
  19. orcot Valued Senior Member

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    It's named: "the peak of eternal sunlight"
    It does exist but is less grandious then it's titel might suggest. Still he solar panels will be In direct sunlight for 80% of the year.
    Even if the martian solar panels can produce 60%. That's still 40% and the martian surface get's a relative even day/night cyclus at least this particulair region on the moon get's 80% sunlight. Also theirs Always going to be weather on mars and dust and clouds will reduce some of it's efficiencies that you would not get on the moon, also even tough the moon is rather dusty onces it is compressed it apears to stay compressed Neil Armstrongs footprint for example would still be recognizable on the moon.
    On mars everything is dusty all the time the wind will bring in more.
    9.3 to reach low earth orbit. 6.4 to reach the moon from there (no return trip as most mass will be cargo) and 9.4 to reach mars (using aerobrakes) each +9.3 and you get 15.7 for the moon and 18.7 for mars. It's a 6% bonus for the moon.
    You will need a hab that can sustain a crew for 180 days you can also go fancy and say that this might contain artificial gravity. The trip to the moon takes 3 days. To be honnest you could strap someone in a chair for 3 days and they should be allright if they are not clausterfobic and know it. They will probably get some space but they would not need a water purification system 180 days worth of food (it takes space), a toilet, excercise equipment or any way to make a hot meal theirs probably other things that aren't necesairy for such a short journey. Also the ability for teleoperation means you can work from earth reducing the number and hours of human presence again reducing costs.
    Meh we will all die one day.
    In general the base would be protected by the lunar body for 50% of the time and it could be covered under meters of dirt. So I imagen it would be less then the people on the ISS recieve (Both mars and lunar missions would travel trough the van allen belt for the same period of time).

    For this particulare location Shackleton_(crater)
    Things are a bit different let's split it up in it's 2 parts (their names are bombastic but that's how they are named) first at the rim you have the peak of eternal light measering 1.25km² in size
    Then over a 5km stretch on a slope of 30° a crater of eternal darkness (this location never sees light and might contain the hydrogen)
    ... It truly is a unique location and it somehow feels like cheating.
    The point is build your base in the darkplace and you should recieve the same radiation like someone that lives inside a cave. (Solar array would have to be in the light offcourse a cable should be lain the distance is acceptable for the value it offers.

    Billy T
    On this particulare location the sunlit side is roughly 373-320°K whilst a small distance away it turns to 50°K. Perhaps theirs a possible advantage in that. Also I could not find any studies for your idea I should think it over.
    http://www.space.com/3296-moonbase-dark-lunar-ice.html
     
  20. billvon Valued Senior Member

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    ?? Commercial crystalline cells are about 18% efficient, and when assembled into modules, are about 16% efficient (the remaining losses come from the fact that the frame and the space between the cells do not contribute to power production.) Single crystal lab grown cells max out at 25% (University of South Wales, 2015.)

    http://upload.wikimedia.org/wikipedia/commons/f/f3/PVeff(rev150519).jpg

    A recent design paper by Dr. Jaffe from the NRL examined (and then tested) the temperature rise for solar power satellites. Assuming 28x28cm "tiles" radiating from both sides, and assuming multijunction cells about 30% efficient, you get a temperature rise of about 50C above radiative ambient - not too different from terrestrial modules.

    http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6187077
     
  21. billvon Valued Senior Member

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    Hmm. I get 3.6km/s for a Mars Hohmann orbit insertion from LEO. I guess we are using different sets of delta V's.
    As you mentioned, both of these assumed cargo transport. Most modern Martian exploration schemes involve several launches on slow orbits to land the return vehicle and a backup. The crew vehicle will be a smaller, faster vehicle.

    Well, not quite. The few-seconds delay means you still can't do real time operation. You could reduce automation compared to a Mars rover though.
     
  22. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    That 50% refers to moon's self blocking of solar flare radiation, and to blocking cosmic rays, which are much more difficult to shield against. The fraction of cosmic rays on trajectory that is going to be blocked by sun and earth is very tiny - quick guess only one of every 5,000.
    I.e. if solar flares were the main problem you would be OK on the surface for about 14 earth days, but not from extreme cold.
    If you say so, OK, but surface is much more reflective than that of a solar cell, which is designed to be strongly absorbing. Again as quick guess, I would think if they must reradiate about 90% of the energy they absorb, their temperature would be at least 500K and diffusion would make them fail in less than a week. More discussion and a suggestion about how to make them survive on the moon, here:
    http://www.sciforums.com/threads/the-moon-or-mars.147640/page-2#post-3301471 (post 35, back a few)

    Solar cells are used in the vacuum of space - I don't know much about how they radiate heat to space, but assume a lot of surface with fins on the back side of their panels. That might not work so well if on the moon, with the IR radiation striking the surface of moon - heating it to some what lesser temperature than if the solar cell were not casting a visible light shadow AND reflecting some IR back to the very black surface it came from. - Quite a different problem than a solar cell on a space craft. What IR it radiates is gone with no return.
     
    Last edited by a moderator: May 25, 2015
  23. paddoboy Valued Senior Member

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    It's utterly totally ridiculous for you to claim it is Impossible.
    In time, yes we will have permanent bases beyond the Earth/Moon system, despite what difficulties need to be overcome.

    http://zapatopi.net/kelvin/papers/letters.html
    Dear Baden Powell

    I am afraid I am not in the flight for “aerial navigation”. I was greatly interested in your work with kites; but I have not the smallest molecule of faith in aerial navigation other than ballooning or of expectation of good results from any of the trials we hear of. So you will understand that I would not care to be a member of the aëronautical Society.

    Yours truly Kelvin
     

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