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I Exomars orbiter and aerobraking

  1. Apr 12, 2016 #1

    sophiecentaur

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    I heard a talk from a fairly well informed guy about the exomars mission. He was saying that the orbiter will, initially have a very elliptical orbit and that it would be using aerobraking to make it circular (saving a lot of fuel). I have a problem understanding that because aerobraking can only remove energy and the resulting orbital height would (I reckon) bring the orbiter below the fringe of the Martian atmosphere. That would mean it would 'fall down' fairly soon.
    I have to conclude that the aerobraking would only reduce the highest orbital distance to what was required and that some fuel would be used to raise the minimum distance out of the atmosphere. (Perigee and apogee terms only apply on Earth???). Someone here must have definitive answer to this. Am I right?
     
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  3. Apr 12, 2016 #2

    Borg

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  4. Apr 12, 2016 #3

    sophiecentaur

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    Yes. Thank you. That shows a series of orbits with decreasing energy and I understand that process. However, if aerobraking can take place at that height, the drag (with or without the effect of the solar panels) will surely continue to take significant energy. So the lifetime of an orbit at that height will be limited. Is there a way to extract energy by aerobraking that will raise the minimum height as well as lowering the maximum height - away from the drag of the atmosphere?
     
  5. Apr 12, 2016 #4
    Once it's at the lowest point, they use the rockets to add some kinetic energy and push it into a higher orbit away from the atmosphere. It's still a significant fuel savings.

    The atmosphere itself can also be used to push it into a higher orbit. During one of the low passes, if the ship is oriented correctly and hit the atmosphere at the right angle, it can bounce off of it like a stone skipping off of the water. This can also be used to increase altitude.
     
  6. Apr 12, 2016 #5

    sophiecentaur

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    Thanks. Two good answers that I had wondered about.
    Hope it all works as it seems like a bit of a shoestring project, compared with Curiosity.
     
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