Heats generated during atmospheric entry

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Discussion Overview

The discussion revolves around the effects of atmospheric density on the frictional heating experienced by a standard sphere during its atmospheric entry on a hypothetical planet. Participants explore various aspects of atmospheric properties, including density, buoyancy, and the nature of the atmosphere itself, while considering the dynamics of entry from infinity.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant poses a question about the optimal atmospheric density for maximizing frictional heating during atmospheric entry.
  • Another participant introduces the concept of neutronium but questions its classification as an atmosphere.
  • A different participant suggests that a gaseous atmosphere, with density varying by altitude, is more relevant to the discussion.
  • One participant asserts that at high energy, all materials behave as fluids, indicating that higher density correlates with increased friction.
  • Another participant proposes that higher density could lead to increased buoyancy, slower entry due to friction, and greater heat conduction.
  • One participant clarifies that when dropping an object from infinity, gravity determines entry speed, and a thicker atmosphere primarily affects the deceleration and heat generation upon entry, dismissing buoyancy and conduction as factors.

Areas of Agreement / Disagreement

Participants express differing views on the role of atmospheric density, buoyancy, and the nature of the atmosphere, indicating that multiple competing perspectives remain without consensus.

Contextual Notes

Some assumptions about the nature of the atmosphere and the conditions of entry are not fully explored, and the discussion includes varying interpretations of how different factors interact during atmospheric entry.

Loren Booda
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Consider a hypothetical planet of given radius and mass. What atmospheric density would generate the most frictional heating on a standard sphere falling from infinity to the planet surface?
 
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Neutronium, although I don't think that most people would categorize it as an 'atmosphere'.
 
Wouldn't neutronium, not being a fluid, inhibit the sphere from falling to the planet? I was thinking more of a gaseous atmosphere, whose density at anyone altitude (for the hypothetical planet mentioned) happens to be dependent on its depth, or total mass
 
At high energy, everything is a fluid. The question doesn't have an answer other than higher density = more friction.
 
How about higher density --> 1. more buoyancy; 2. slower entry (due to friction overall); 3. greater heat conduction
 
Last edited:
If you're dropping the object from infinity, the entry speed is determined by gravity. A thicker atmosphere doesn't change that, it just slows the object down faster once it gets there (generating more heat).

Buoyancy is not ever a factor.

Conduction and convection are not factors.
 

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