Originally posted by Figher Master FIN
I've read a lot about the F/A 22 or the "Raptor"... I was jsut wondering what the Raptors real top-speed is... On several sites I've seen taht the top-speed only would be from 1.7-2 mach... But ATS claims that the plane is capable of Mach 3 preformance... What is the truth...?

I wouldnt believe most things you read on ATS, especially if its presented without credible sources. Personally, no, I dont think the F-22s top speed is as high as mach 3, maybe mach 2.5 yes but not mach 3. Why? Because theres a hell of a leap between 2.5 and 3, much more than 2 and 2.5 and I believe that stealth and manoueverability is worth more in todays forces than high top speeds.

The Raptor's top speed has not been published however we can make a pretty good guess using the information already available on it.
The Raptor has a lot of power, in fact it has a better power to weight ratio than the SR-71 Blackbird.

Stealth has actually slowed the Raptor down a bit because in order to be more stealthy, it has no variable geometry inlets which can force air into the engine faster than the airspeed of the plane - this is the technique used by the Blackbird to reach it's record setting speeds of Mach 3 +.

Before I knew this (as some of my older posts can prove) I too thought the Raptor must have a top speed in the Mach 3 range but the lack of variable geometry inlets changes everything.

A good "guesstimate" would be maybe Mach 2.0 - 2.3.

There have been rumors it is capable of flying at Mach 3 very briefly (due to the materials used, lack of an especially designed cooling system, no special design measures to operate continuously at that speed, it could never do so prolongued). These are just rumors however, see the above posts considering lack of variable geometry inlets for why even that is unlikely.

[edit on 23-7-2005 by Simon666]

ok, good so we can draw the line between 2.0-2.5 mach...

Does speed have anything to do with the RAM coating coming off

There is widespread use of composites, which are basically usually either glass fibers or carbon fibers reinforcing a plastic matrix. Even if nomex is used as matrix, it will decompose above around 400 degrees celsius or 800 fahrenheit. Even the aerodynamically especially designed SR-71 experienced temperatures of 600 degrees fahrenheit at prolongued flight on some parts of the airframe. The F-22's shape is optimized for stealth, not for Mach 3 performance, nor has it black paint to radiate part of the heat away or specially designed cooling. Even if it could fly some time at mach 3, it would better not do so long.

If the F-22 can reach mach 3, I wonder what the YF- can reach....

The Raptor has good thrust to weight ratio that is why it can go Mach 1.6 without afterburners. Now with afterburners on I think it can go from mach 2-2.5 but not much more than that.

I would think the US military would Classified the real top speed of the Raptor. after all it is a brand new aircraft, we won't know the real top speed for a while.

Originally posted by WestPoint23
The Raptor has good thrust to weight ratio that is why it can go Mach 1.6 .

Why talk about the thrust to weight ratio when that is only importent for the exeleration but not for the maximum speed which depends much more on the thrust to air resistens or drag ratio (which depends on the aerodynamics)

Truly the max speed depends on from the weight but inderectly and much more slightly. More weight would mean that the wing must produse more lifting forses and that means it will also produse more drag (it either has to be bigger or use some mechanics) which brings us back to the thrust to drag ratio.

IIRC the F-22 is now actually limited to Mach 1.78 because of it's fixed engine inlets.

It will, however, get up to Mach 1.78 faster than anything else in the air, due to it's thrust/weight ratio.

IIRC, xmotex....that 1.78 is coming from an official USAF site, a government site, aircraft magazine, etc.?

Would the USAF or the US actually allow such classified information to be released as "official"?

Various 'unofficial' reports, ranging from actual Raptor pilots and aircraft media sources have put the estimated top speed of the F-22 Raptor at 2.0 or better with afterburner. Perhaps your 1.78 figure is in non-afterburner mode, which would be supercruise?

Anyhow, what is almost sure, is that the F-22 will reach whatever speed probably faster than most aircraft in the air today.







seekerof

[edit on 23-7-2005 by Seekerof]

I believe the aircraft's frame becomes too instable over Mach 1.8, so it's limited to only 1.8 max, but I could be wrong though.

I am not sure where I got the 1.78 figure actually, I remember reading an article a while ago describing how the production F/A-22 differed from the YF-22 prototype, IIRC fixed inlets (limiting dash speed) were one of the changes. I think 1.78 is just a figure I have seen mentioned a few times on other boards.

It's deceptive using dash speed to describe how "fast" a fighter is anyway, a fighter that can cruise at Mach 1.6 for extended periods is effectively "faster" than a fighter that can do Mach 2.5 for a short time.

If afterburners were only used for pure speed, that would be true, but they are also used for acceleration. As I said before, the Mach 1.78 figure may not be accurate, but it wouldn't shock me much either. The F-22 is not a intended to be a sprinter (the F-15 is almost certainly faster WRT absolute top speed) but a marathon runner.

[edit on 7/24/05 by xmotex]

Originally posted by Simon666
Even if nomex is used as matrix, it will decompose above around 400 degrees celsius or 800 fahrenheit. Even the aerodynamically especially designed SR-71 experienced temperatures of 600 degrees fahrenheit at prolongued flight on some parts of the airframe. The F-22's shape is optimized for stealth, not for Mach 3 performance, nor has it black paint to radiate part of the heat away or specially designed cooling. Even if it could fly some time at mach 3, it would better not do so long.

you talk a lot about heat...is that really a problem???

Obviously since the Raptor uses composites and titanium the structure itself will have no problem with any heat. Composites are great for a lot...like strength, longevity, high temps. and Titaniums melting point is 3,020 degrees F, for comparison mach 4 is around 1,200 degrees, so there no problem there.

I would think that the paint could withstand quite abit...I would think by now they would have paint that could stand up to more heat then the airframe.

O damn, back to square one... so you think it could "only" go 1.78 mach...?

I mostly agree with murcielago regarding heat and the Raptors ability to withstand it, of course the airframe will generate heat at very high speeds and that will act like a big flashing 'Here I am' sign to any opponent with the right equipment, ie most of them.

There will though be times when a high speed dash is required and I expect the Raptor to be able to hit mach 2 at such times. The reason I have for not expecting it to go much faster than that is not to do with RAM or paint but simply aerodynamics. Having a large internal weapons bay gives the Raptor an unavoidably higher cross section than an aircraft that doesn't, you know how the fuselage is quite boxy and all.

Despite very advanced CAD techniques making this as efficient as possible it is still a bit of a problem regarding inherent induced drag at high speeds and that will be the limiting faqctor in regards top speed. Because of its need to carry stuff on the inside the Raptor has to use a great deal of muscle to get to speeds that other lesser aircraft can reach more easily. Of course it has that muscle as it was designed to but the effort required to push such a boxy shape towards mach 3 will be beyond even the Raptor.

Dont forget, Concorde, for one, was long and thin as a fashion statement.