How Does Aerobraking Work for the ExoMars Orbiter?

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Discussion Overview

The discussion centers on the aerobraking process for the ExoMars orbiter, specifically how it transitions from an elliptical to a circular orbit while managing fuel efficiency and atmospheric interactions. Participants explore the mechanics of aerobraking, its implications for orbital height, and the potential need for additional propulsion.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about how aerobraking can effectively lower the maximum orbital height without causing the orbiter to fall into the Martian atmosphere, suggesting that some fuel would be necessary to raise the minimum height afterward.
  • Another participant references a previous example of aerobraking, indicating that the process involves a series of orbits with decreasing energy.
  • A participant questions whether aerobraking can also raise the minimum orbital height while lowering the maximum height, given the drag from the atmosphere.
  • One participant explains that after reaching the lowest point, rockets can be used to add kinetic energy and push the orbiter into a higher orbit, highlighting the fuel savings involved.
  • Another participant elaborates that the atmosphere can be utilized to increase altitude if the orbiter is oriented correctly during low passes, comparing the maneuver to a stone skipping on water.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the mechanics of aerobraking and its effects on orbital height, with multiple competing views and uncertainties remaining regarding the process and its implications.

Contextual Notes

There are unresolved questions about the specific mechanics of aerobraking, including the effects of atmospheric drag and the conditions under which the orbiter can effectively raise its minimum orbital height.

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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Something like this? - MGS Aerobraking.

brakeprof2.gif
 
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?
 
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.
 
newjerseyrunner said:
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.
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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