Why can't Jet planes fly in space?

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Discussion Overview

The discussion centers around the question of why jet planes cannot fly in space, exploring the roles of lift, atmosphere, and propulsion systems. Participants examine the differences between jet engines and rocket engines, as well as the definitions of flying and space.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants suggest that jet planes cannot fly in space due to the absence of atmosphere, which is necessary for lift and the operation of jet engines.
  • Others argue that thrust is the primary requirement for movement in space, and that rocket engines, which carry their own oxidizers, are designed for such environments.
  • A participant notes that while a jet could technically "fly" in space if placed in orbit, it would not be able to produce thrust or maneuver effectively without atmospheric conditions.
  • There is a discussion about the definition of flying, with some asserting that it requires movement through the atmosphere, while others point out that satellites operate in a near-vacuum and still maintain orbital motion.
  • Some participants propose that if a jet engine could use a fuel that does not require oxygen, it might be possible to operate in space, but others counter that this would effectively make it a rocket.
  • The differences between open and closed system propulsion methods are highlighted, with jet engines relying on atmospheric oxygen and spacecraft being self-contained.
  • One participant mentions the SR-71 as an example of an aircraft that operates at the edge of space, suggesting that definitions of "space" can vary.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the definitions of flying and space, as well as the operational capabilities of jet engines versus rocket engines. The discussion remains unresolved with no consensus reached.

Contextual Notes

There are limitations in the discussion regarding the definitions of "space" and "flying," as well as assumptions about the capabilities of jet engines in different atmospheric conditions.

Arjun Ar
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Why can't Jet planes fly in space?

Is is because it doesn't get lift or is it due to the absence of atmosphere?
 
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What is a jet engine? How does it work?
 
And wings. How do they work?
 
Borek said:
What is a jet engine? How does it work?

D H said:
And wings. How do they work?

That's the difference between chemist and physicist :smile:
 
I guess you guys have not seen "Airplane II" :smile:
 
Arjun Ar said:
Why can't Jet planes fly in space?

Is is because it doesn't get lift or is it due to the absence of atmosphere?

What is the relationship between lift and atmosphere. Your statement seems to imply that they have nothing to do with each other. Is that what you believe?
 
Of course, you don't really need "wings" or "lift" in space. What you need is thrust. The difference between a jet engine and a rocket engine is that the rocket engine contains its own oxygen (perhaps in the form of a chemical) while a jet engine gets its oxygen out of the air.
 
A jet could fly in space. It couldn't produce thrust, maneuver, or keep the cabin pressured in space. Use a rocket to put it into orbit and it will fly until gravity eventually pulls it back down. The strict definition of flying is to move through the atmosphere and there is most certainly atmosphere in orbit.
 
NumericalPain said:
A jet could fly in space. It couldn't produce thrust, maneuver, or keep the cabin pressured in space. Use a rocket to put it into orbit and it will fly until gravity eventually pulls it back down. The strict definition of flying is to move through the atmosphere and there is most certainly atmosphere in orbit.

Depends on how high the orbit is. Above the atmosphere, it would be in a ballistic trajectory and I don't think traveling in a ballistic trajectory is considered flying. It would no more be flying than the moon is flying.
 
  • #10
NumericalPain said:
. The strict definition of flying is to move through the atmosphere and there is most certainly atmosphere in orbit.

The heights that satellites orbit have almost no atmosphere. That's actually one of the points, with minimal atmosphere, satellites don't need to carry as much fuel to compensate for constant frictional forces slowing it down.
 
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  • #11
HallsofIvy said:
Of course, you don't really need "wings" or "lift" in space. What you need is thrust. The difference between a jet engine and a rocket engine is that the rocket engine contains its own oxygen (perhaps in the form of a chemical) while a jet engine gets its oxygen out of the air.

If oxygen is the problem, what if we use some other fuel that doesn't require oxygen for burning? Could we fly the jet plane in space?
 
  • #12
Arjun Ar said:
If oxygen is the problem, what if we use some other fuel that doesn't require oxygen for burning? Could we fly the jet plane in space?
No. They don't carry enough fuel, have enough thrust or the ability to maneuver in space.
 
  • #13
Arjun Ar said:
Why can't Jet planes fly in space?

Is is because it doesn't get lift or is it due to the absence of atmosphere?

Greetings Arjun Ar,

Jet engines employ an “open system” method of propulsion therefore they require the high velocity airflow of atmosphere through their turbine engines from which they make use of its oxygen to allow combustion with the fuel the carry. Additionally, airflow is required to produce lift as well as provide axis control of the jetliner.

Conversely, a spacecraft employs a “closed system” method of propulsion whereby all the elements necessary to produce thrust for acceleration and axis control of the spacecraft are self-contained aboard the spacecraft thereby making its ability to traverse a desired expanse of space 100% independent of its surroundings.
 
  • #14
It depends on what you qualify as "space."
The US has developed the SR-71, which allowed the pilot to see the curvature of the Earth and the blackness of space. There was still, admittantly, a little atmosphere left.
:D
 
  • #15
Arjun Ar said:
If oxygen is the problem, what if we use some other fuel that doesn't require oxygen for burning? Could we fly the jet plane in space?

At the point that you carry all your fuel on board, the "jet engine" becomes a rocket.

The broad definition of a jet engine DOES include a rocket engine, however, so yes, a "jet" engine could indeed fly in space. However, not the more specific turbofan or turbojet that you're thinking of, whose operations rely on an atmosphere with oxygen.
 

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