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  1. #1
    David Knisely's Avatar
    David Knisely Guest

    Default Sampling Mars Surface???



    Bert posted:


    It is VERY important, as any geologist will tell you. The rocks rovered-to
    and analyzed by the Sojourner rover were sometimes different from each other.
    You can't analyze what you can't get to.


    6 wheels means multiple redundancy in case one motor fails or one wheel get
    hung-up on something. The engineering is based on Pathfinder rover technology
    which worked pretty well last time.


    That sounds half-baked (too heavy). Again, unless you can go to something you
    can see, you won't know anything more about it than what it looks like.


    That would require a substantial lander (and heavy). Again, it would not tell
    you anything more than what was 20 feet directly under the lander. If the
    lander landed in a spot where there was no water 20 feet down, but there was a
    water-bearing layer not far away, there would be no way to get to it.


    Yes it is, as was proven by the Sojourner rover at Sagan Station.


    No, it is not. The overall terrain shape might be similar, but the rocks are
    different depending on where you *go*. It is the difference and where the
    various rock types are found which tell the story of the geologic history of
    the planet.


    It can be "greener" in that on one side of the crater Gusev (where MER-1 is
    targeted) there is a volcano, and on the other side is a breach in the wall
    where the outflow channel Ma'adim Vallis begins. That makes for a heck of a
    difference in what might be found on the crater floor.
    --
    David W. Knisely KA0CZC@navix.net
    Prairie Astronomy Club: http://www.prairieastronomyclub.org
    Hyde Memorial Observatory: http://www.hydeobservatory.info/

    **********************************************
    * Attend the 10th Annual NEBRASKA STAR PARTY *
    * July 27-Aug. 1st, 2003, Merritt Reservoir *
    * http://www.NebraskaStarParty.org *
    **********************************************




  2. #2
    David Knisely's Avatar
    David Knisely Guest

    Default Sampling Mars Surface???

    Bert posted:


    Hardly. Try going to http://mars.jpl.nasa.gov/mer/ and reading what is
    there. I have seen TIME produce articles which are oversimplified and, in
    some cases, a bit inaccurate.


    That is too bad, because they are about the right size (10 inches in
    diameter). Too large and they would not fit in the lander package. Too small
    and they might not function under the weight of the rover or allow it to go
    over some rocks.


    You need size to carry things like the multiple instruments, the solar panels,
    the computers, the cameras, the masts, the arm, ect. Its not very big, and
    under the weaker Martian gravity, it should do fine.


    Yea, right, using a golf cart on Mars. Talk about a stupid idea. This is a
    scientific mission to a dangerous world, not an 18 hole jaunt down some smooth
    grassy fairways!


    That is the entire development and construction cost, and not just the cost of
    the hardware.


    It may travel that much (or somewhat more, as its maximum daily "range"
    (barring stops for obstacles) is close to 100 meters), and then again, if
    there is a small area that has a lot to be investigated, the rover may not
    travel very far during a particular day.


    The next probe to Mars will be an orbiter (Mars Reconnaissance Orbiter) and
    not a lander. The next landing attempt *may* be another attempt to fly a
    modified version of the backup spacecraft from the Mars Polar Lander Project,
    now deemed "Phoenix", to the polar regions of Mars.

    --
    David W. Knisely KA0CZC@navix.net
    Prairie Astronomy Club: http://www.prairieastronomyclub.org
    Hyde Memorial Observatory: http://www.hydeobservatory.info/

    **********************************************
    * Attend the 10th Annual NEBRASKA STAR PARTY *
    * July 27-Aug. 1st, 2003, Merritt Reservoir *
    * http://www.NebraskaStarParty.org *
    **********************************************



  3. #3
    David Knisely's Avatar
    David Knisely Guest

    Default Sampling Mars Surface???

    Bert posted:


    They have something better: the rock abrasion tool. It can cut into a rock
    and sample what is beneath the surface. It also has a variety of instruments
    to analyze the composition of the rock, as well as a geologic microscope to
    give images of the structure of the rock.


    The solid "crust" (ie: bedrock) is exposed in a number of places on the
    Martian surface, so there is little need to drill in order to find it. All
    that is needed is the ability to move something over to the rock outcropping
    and analyze what is there. That ability is provided by the MER-class rovers.


    Most of our deficit's recent expansion is coming from Bush's little excursion
    into Iraq. The cost of the probes we are sending isn't enough to even show as
    a line on a pie chart of the total federal budget. As for the probes, nothing
    ventured, nothing gained.
    --
    David W. Knisely KA0CZC@navix.net
    Prairie Astronomy Club: http://www.prairieastronomyclub.org
    Hyde Memorial Observatory: http://www.hydeobservatory.info/

    **********************************************
    * Attend the 10th Annual NEBRASKA STAR PARTY *
    * July 27-Aug. 1st, 2003, Merritt Reservoir *
    * http://www.NebraskaStarParty.org *
    **********************************************




  4. #4
    David Knisely's Avatar
    David Knisely Guest

    Default Sampling Mars Surface???

    Bert posted:


    Bert, have you ever actually *looked* at the pictures from Viking or
    Pathfinder? There are rocks EVERYWHERE.


    It isn't 500 lbs. Its 190 lbs (remember, Mars gravity is 0.38 that of Earth).


    --
    David W. Knisely KA0CZC@navix.net
    Prairie Astronomy Club: http://www.prairieastronomyclub.org
    Hyde Memorial Observatory: http://www.hydeobservatory.info/

    **********************************************
    * Attend the 10th Annual NEBRASKA STAR PARTY *
    * July 27-Aug. 1st, 2003, Merritt Reservoir *
    * http://www.NebraskaStarParty.org *
    **********************************************




  5. #5
    David Knisely's Avatar
    David Knisely Guest

    Default Sampling Mars Surface???

    Bert posted:


    There were also a number of BIG rocks. There is no need to go "1.8 miles
    away" to find a rock.


    Irrelevant. The rover won't get stuck for just being too heavy as you imply.
    The rover has been tested under conditions which are a close match to those
    on Mars. Its basic roving design is based on the successful Pathfinder rover.
    It should work on Mars at least as well (if not better) than the Pathfinder
    rover did.


    The Pathfinder rover (with similar but smaller wheels) had no trouble moving
    around the surface of Mars. It moved over low dust dunes, over surfaces with
    small rocks, and over flat compacted soil. Where it encountered bigger rocks,
    it either drove around them, or stopped and called home for instructions. The
    wheels are wider than the wheel an Earth vehicle is, and the wheel is
    specifically designed to perform well on the Martian surface.


    Its not the wheels that give the "push". Its the electric drive motors, and
    they are more than adequate for the job. If the rover can drive around on the
    Earth's rough surface (as engineering models were shown demonstrating their
    abilities), they can easily do so on Mars. The lunar rovers couldn't drive on
    Earth (without assistance), but they did a very nice job of it on the moon.
    They needed bigger wheels due to the speed which they needed to travel over
    the surface. The Mars Exploration Rovers don't need to go fast, they just
    need to "go".
    --
    David W. Knisely KA0CZC@navix.net
    Prairie Astronomy Club: http://www.prairieastronomyclub.org
    Hyde Memorial Observatory: http://www.hydeobservatory.info/

    **********************************************
    * Attend the 10th Annual NEBRASKA STAR PARTY *
    * July 27-Aug. 1st, 2003, Merritt Reservoir *
    * http://www.NebraskaStarParty.org *
    **********************************************




  6. #6
    David Knisely's Avatar
    David Knisely Guest

    Default Sampling Mars Surface???

    Bert posted:


    TIME is incorrect. The lander has a mass of 170 kg (weighs about 375 lbs on
    Earth, but only 142 lbs on Mars). It is smaller than many golf carts. The
    tallest segment is the Pancam Mast Assembly (containing cameras), which, when
    deployed, will stand about 1.4 meters above the ground (about 4.6 feet). The
    rest of the rover is less than half this high.
    --
    David W. Knisely KA0CZC@navix.net
    Prairie Astronomy Club: http://www.prairieastronomyclub.org
    Hyde Memorial Observatory: http://www.hydeobservatory.info/

    **********************************************
    * Attend the 10th Annual NEBRASKA STAR PARTY *
    * July 27-Aug. 1st, 2003, Merritt Reservoir *
    * http://www.NebraskaStarParty.org *
    **********************************************




  7. #7
    David Knisely's Avatar
    David Knisely Guest

    Default Sampling Mars Surface???

    Bert blurted out:


    It is when you imply that the rover will somehow not be able to move. If it
    has enough ability to move around on the Earth, it certainly will be able to
    move around on Mars. It will weigh (force) less on Mars, so it should be able
    to move a little more easily without getting stuck, as your comments about the
    wheels imply.


    Tracks would work if the darn thing was a tank. It isn't. The wheels are set
    on pivoting rockers which allow it to go over obstacles without tilting
    excessively or getting upset. It is more able to go over things than
    something small with tracks. With fixed tracks, it might get one set over a
    rock and then cause the vehicle to tilt to such a degree that it would fall
    over. The rocker bogie system that the wheels are mounted on makes better
    sense than tank tracks.


    No, both probes are landing closer to the equator. The polar regions will
    have to wait until the Phoenix lander tries again in 2007.


    --
    David W. Knisely KA0CZC@navix.net
    Prairie Astronomy Club: http://www.prairieastronomyclub.org
    Hyde Memorial Observatory: http://www.hydeobservatory.info/

    **********************************************
    * Attend the 10th Annual NEBRASKA STAR PARTY *
    * July 27-Aug. 1st, 2003, Merritt Reservoir *
    * http://www.NebraskaStarParty.org *
    **********************************************




  8. #8
    Odysseus's Avatar
    Odysseus Guest

    Default Sampling Mars Surface???

    David Knisely wrote:
    Tracked vehicles are also prone to 'throwing' their tracks while
    negotiating obstacles; on the Mars probes there's no crew to get out
    and remount or tighten them if they get out of whack. On an unmanned
    vehicle I think a limited but reliable system should generally be
    preferable to a high-performance but finicky one, whether it be for
    propulsion, sampling, or any other 'mission-critical' function.

    --
    Odysseus

  9. #9
    David Knisely's Avatar
    David Knisely Guest

    Default Sampling Mars Surface???

    Bert posted:


    Because that is what you do. You "burt" out without doing any real research
    to back up what you say. You make gross generalizations based on your limited
    experience and then are surprised when others object to what you "blurt out".
    Do your homework and you might be surprised as to what you might learn!


    You would have to have one heavy gyro to keep such a thing from going over.
    That adds to the weight and adds to the power budget to keep the darn thing
    spinning.


    Oh, so you mean that the rover should drive off a cliff then or fall over when
    attempting to climb over a rock that is too big for it? The rover is smart
    enough to rove to a given location without help, and *only* if it finds
    something in that path isn't quite right for some reason, it calls for help to
    let *us* decide what to do. Tracks or wheels, its all the same. There are
    some things which the rovers simply can't get past, and that requires human
    intervention.


    Gad, why do you keep saying such stupid things. Traction isn't necessarily an
    issue, but going over (or around) large rocks *is*. The wheels are designed
    to work and they should work as well or better than some tracked vehicle.


    I do know a *lot* more physics (and better physics) than you do, and from the
    looks of things, the situation is unlikely to change anytime soon. Get thee
    to a library!


    They are *not* landing both rovers on the Martian Equator! They are landing
    in near-equatorial *regions* but not on the equator. The first one is landing
    at about 14 degrees south latitude on the floor of the crater Gusev, and the
    second one is landing slightly closer to the equator in the Meridiani Terra
    region. NASA is taking some chances even sending the rovers there, but
    without taking chances, there is no chance of answering the questions about Mars.


    Where did you get that idea? I have criticises NASA but at least I have been
    able to see that from a scientific standpoint, most of the engineers and
    scientists who work in the various programs are smarter than I am, and from
    your postings, it is quite obvious that they are HUGELY smarter than you are!
    --
    David W. Knisely KA0CZC@navix.net
    Prairie Astronomy Club: http://www.prairieastronomyclub.org
    Hyde Memorial Observatory: http://www.hydeobservatory.info/

    **********************************************
    * Attend the 10th Annual NEBRASKA STAR PARTY *
    * July 27-Aug. 1st, 2003, Merritt Reservoir *
    * http://www.NebraskaStarParty.org *
    **********************************************




  10. #10
    David Knisely's Avatar
    David Knisely Guest

    Default Sampling Mars Surface???

    Bert posted:


    Not if it gets hung up on a rock! It is fairly likely, so it had better not
    try to drive around many big ones (or even very small ones). A small rock
    which gets pulled into the inside of the track could jam the track wheels and
    bring the whole thing to a halt. Odysseus is correct; wheels are better.


    So? The current rover can drive over sand. It was tested under a variety of
    conditions and in a variety of terrains.


    What exactly do you know about these wheels? I think the designers know just
    a little bit more than you do about designing something to rove about on Mars
    than you do.


    Oh, so now instead of golf carts, you want to send toy trains to Mars? (Gad,
    talk about a gross oversimplification!!)


    Not if you intend to use the gyro's angular momentum to keep the heavy rover
    from tipping over! There is also the power issue. You still don't know what
    you are talking about.

    --
    David W. Knisely KA0CZC@navix.net
    Prairie Astronomy Club: http://www.prairieastronomyclub.org
    Hyde Memorial Observatory: http://www.hydeobservatory.info/

    **********************************************
    * Attend the 10th Annual NEBRASKA STAR PARTY *
    * July 27-Aug. 1st, 2003, Merritt Reservoir *
    * http://www.NebraskaStarParty.org *
    **********************************************




 

 
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