Are Ionospheric Scramjets possible?

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Discussion Overview

The discussion revolves around the feasibility of using scramjet technology in the ionosphere, particularly at altitudes around 100 km, which is near the Kármán line. Participants explore the implications of operating scramjets in an environment with low atmospheric density and high speeds.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant notes that while the ionosphere contains high levels of oxygen, it is extremely thin, which could limit lift and necessitate very high speeds to maintain flight.
  • Another participant questions the viability of a scramjet at Mach 25 in the ionosphere, suggesting that at such altitudes, the aircraft would effectively become a satellite due to the required orbital speed.
  • A participant raises the idea that even at low atmospheric density, a scramjet might still intake some oxygen at high speeds, inquiring about the potential for operation despite low thrust.
  • One participant emphasizes that while combustion might be possible, the thin air and relevant drag at high speeds present significant challenges.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility of scramjets operating in the ionosphere, with no consensus reached on the practicality or effectiveness of such a concept.

Contextual Notes

Participants highlight limitations related to atmospheric density, drag, and the implications of operating at orbital speeds, but these aspects remain unresolved.

Apollo19
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I was doing some Wikipedia browsing, and I came across the concept of Scramjets for spaceplanes. The highest estimate for a top speed of a scramjet in atmosphere is Mach 25, which is approximately orbital velocity. The ionosphere contains high levels of O, so would it be possible to fly a scramjet aircraft in it (at approx. 100km)?
 
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High fraction does not mean high amount - the ionosphere is extremely thin. You don't get much oxygen there, and not much lift. You need a very high speed to counter this. 100km is at the Kármán line, where the required flight speed reaches the orbital speed - your "plane" becomes a satellite.
 
Thanks. Thing is that at Mach 25, surely even though it is very thin, you are taking in some? Do you know if such a scramjet would work, even if it had very low thrust? And for the sake of the theory, assume that there is no drag.
 
I'm sure you can burn something, but airplanes are always a quantitative problem.
The air is thin, but at that speed drag is relevant.
 

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