Are Ionospheric Scramjets possible?

[Apollo19]

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)?

 

[mfb]

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.

 

[Apollo19]

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.

 

[mfb]

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.

 

[pmacias]

I can say that the concept of Ionospheric Scramjets is certainly possible, but it would require significant technological advancements and challenges to overcome. Scramjets are a type of air-breathing engine that relies on high-speed airflow to ignite and sustain combustion. These engines are typically designed for high-altitude, high-speed flight in the Earth's atmosphere.

At 100km altitude, the ionosphere is indeed rich in atomic oxygen (O) atoms, which can be used as a source of oxidizer for the scramjet's combustion. However, there are several key factors that would need to be addressed for Ionospheric Scramjets to become a reality.

Firstly, the ionosphere is a highly variable and dynamic region of the Earth's atmosphere, with constantly changing levels of O atoms and other gases. This would make it challenging to maintain a consistent and reliable source of oxidizer for the scramjet's combustion.

Secondly, the extremely high speeds and temperatures involved in scramjet flight would require advanced materials and cooling systems to prevent overheating and structural damage. This would be particularly difficult to achieve in the harsh environment of the upper atmosphere.

Lastly, the design and operation of a scramjet in the ionosphere would need to be carefully considered to avoid any potential negative impacts on the Earth's atmosphere and the delicate balance of gases within it.

In summary, while the concept of Ionospheric Scramjets is scientifically possible, it would require significant advancements in technology and careful consideration of various challenges before it can become a practical and feasible option for high-speed flight in the ionosphere.