Why hasn't the maximal speed of jets go up in decades?

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#1
It has been a while since the maximal speed of jet fighters stay the same. Ever since 1970s, the top speed of fighter jets are always around mark 2. It is already 2016, it hasn't changed for the jets. While there are already some hyper sonic vehicles, missiles, etc. being developed which can go beyond the speed of mark 5~10, there is no word of any new fighter jets will get such feat.

Imagine if a fighter jet will go at the speed of mark 5+, no current anti-aircraft missiles will be able to catch it unless it's "off-guard". In a hyper sonic fighter jets, you can easily outrun all air defense missiles. Correct me if I am wrong, most air defense missiles have a maximal speed of mark 2.5~3.5.

So why nobody has even tried to increase the speed of jets to out run the missiles?
 
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Unless I am wrong I think it has to do with the G effects on the human body, that and it might be down to making something capable of those speeds efficient.

Nether-the-less I am sure the US military are working on something capable of those speeds. Efficient or not.
 
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It has to do with the design of the warplanes and the aerodynamics of the warplanes at high altitude. A faster warplane at mach 3 or more would no doubt evade antiaircraft missile batteries but its gunner accuracy and fuel efficiency would be decreased. The design criteria of warplanes also takes into account the curvature of the earth's surface with the aim of optimizing the speed for optimum delivery.
 
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Unless I am wrong I think it has to do with the G effects on the human body, that and it might be down to making something capable of those speeds efficient.

Nether-the-less I am sure the US military are working on something capable of those speeds. Efficient or not.
The G effects is only for maneuverability. That is, when the aircraft suddenly turns, it will create a high G effect. It doesn't matter when your jet is going straight or change direction slowly. When the jet is faster than the missile, it doesn't even need to maneuver at all unless the missile is coming from the front or calculated the jet's (future) position. The jet can just keep going and without worrying the missile at all.

It has to do with the design of the warplanes and the aerodynamics of the warplanes at high altitude. A faster warplane at mach 3 or more would no doubt evade antiaircraft missile batteries but its gunner accuracy and fuel efficiency would be decreased. The design criteria of warplanes also takes into account the curvature of the earth's surface with the aim of optimizing the speed for optimum delivery.
What about the hyper sonic vehicles multiple countries are developing? From what I have heard, the US, Russia, China have all tested such weapon many times. While these weapons are meant to carry a payload only (no onboard pilot), it at least proves the fuel problem is not there.

As for gunner accuracy, I don't even recall when was the last time a modern air to air battle involved gun firing. It was all done by missiles. The pilots just need push the button to fire off the missiles which will be guided to the enemy through either radar lock, or some other means of guidance. Human (manual) aiming is not needed at all.
 
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The G effects is only for maneuverability. That is, when the aircraft suddenly turns, it will create a high G effect. It doesn't matter when your jet is going straight or change direction slowly. When the jet is faster than the missile, it doesn't even need to maneuver at all unless the missile is coming from the front or calculated the jet's (future) position. The jet can just keep going and without worrying the missile at all.
That makes sense. I understand about G forces on the body when the aircraft in manoeuvring. I was thinking about the effects of being forced into the back of the seat sort of thing.

I was saying about efficiency and remembered something about the MiG-25/31 which was capable of speeds matching those of the SR-71. I read or heard somewhere that when did those speeds the engines needed to be changed once it landed. Maybe this is why US for example is looking at stuff like SCRAM jets.
 

cao cao

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Okay , Let's put the hypothesis that the fighter jets will be the speed of 5 Mach , the human body can not afford this speed its hardly bear speeds like 2, 2.5 mach .. Not only that .. even the jet's body can't afford this speed too , and remember today our Fighter have a Problem in the range Because of low load of fuel , and with 5 mach speed what will happen ?!
 
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Okay , Let's put the hypothesis that the fighter jets will be the speed of 5 Mach , the human body can not afford this speed its hardly bear speeds like 2, 2.5 mach .. Not only that .. even the jet's body can't afford this speed too , and remember today our Fighter have a Problem in the range Because of low load of fuel , and with 5 mach speed what will happen ?!

I disagree.
Think about space shuttles. They couldn't have escaped the earth gravity without going at least 7.9km/second (correct me if I am wrong), and that is more than 20x the speed of sound. The astronauts are totally fine with that speed, because the space shuttles do not do sudden large maneuvering. Now if the fighter jets or bombers can go at even just Mark 5.0, they can be faster than all the air defense missiles.
 
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I disagree.
Think about space shuttles. They couldn't have escaped the earth gravity without going at least 7.9km/second (correct me if I am wrong), and that is more than 20x the speed of sound. The astronauts are totally fine with that speed, because the space shuttles do not do sudden large maneuvering. Now if the fighter jets or bombers can go at even just Mark 5.0, they can be faster than all the air defense missiles.
Very good point, I almost forgot about the space shuttles and the speeds they go to get out of our atmosphere and into space.

Lets say that the USA does have an aircraft capable of these speeds and all known air-defence systems cannot tackle it. Would countries be looking at laser weaponry in order to deal with it or will a missile be developed that can catch it?
 
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I am suspecting that they may be some critical issues involved pertaining to the machine and crew operating at the increased level. Is the human body able to cope with the increased pressure? Will the aircraft be able to physically withstand the pressure and will it be able to consistently be able to function effectively at this level? The other consideration is that if the missiles can be effective at bringing down aircraft at the speed, then I don't see a problem that there could be developed missiles that could be effective against at a greater speed.
 
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I imagine it has to do with the fact that the basic laws of Physics have remained the same. Notice that the maximum speed for piston engines hasn't gone up either. The laws of aerodynamics have remained the same. Steam locomotives are still limited to about the same speeds. New technologies may well offer higher speeds. There is some limited room for improved materials and design,
When we develop new technology, expect new technology in air defense systems
 

vash

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Very good point, I almost forgot about the space shuttles and the speeds they go to get out of our atmosphere and into space.

Lets say that the USA does have an aircraft capable of these speeds and all known air-defence systems cannot tackle it. Would countries be looking at laser weaponry in order to deal with it or will a missile be developed that can catch it?
In my opinion, every weapon will have a counter... over time at least. So when someone suddenly come up with hyper sonic jet fighters, someone else might come up with the same thing after some years. Or a missile to catch up to it. Direct energy weapon will definitely be useful against super speed targets. But everything takes time to develop.

I am suspecting that they may be some critical issues involved pertaining to the machine and crew operating at the increased level. Is the human body able to cope with the increased pressure? Will the aircraft be able to physically withstand the pressure and will it be able to consistently be able to function effectively at this level? The other consideration is that if the missiles can be effective at bringing down aircraft at the speed, then I don't see a problem that there could be developed missiles that could be effective against at a greater speed.
Well my previous response works here too. Think about when were F117, F22, B2, developed and deployed. It has been decades, now there is still no operational stealth fighters from other countries. Sure, multiple countries are developing them at this moment, but they are nowhere near mass production.

I am sure eventually there will be hyper sonic AA missile too, or even energy weapons suggested by Susimi. But every piece of sophistic weaponry takes decades to develop. Even back in WWII, if the Germans could come up with their jet earlier, they might win the war, but it wasn't entirely up to them. By the time they were able to deploy their first jet fighter, it was a little too late for the war.