Originally posted by FredT
We are getting a bit off topic, but I was watching a show that talked about a british proposal in WWII to make an aircraft carrier out of a water sawdust slurry that would have been big enought to launch B-17's from and if kept in cold climates would never melt

Yes, Roosvelt and Churchill wanted to use it for D-day invasion, but it was cancelled it 1943. It should be 660 meters long with 3590 crew and 200 planes! So more like a floating base than aircraft. They actually build 20 meter long model for test in Canada and it performed well.
Also the Russian wanted to build concrete submarine during 90ties. Concrete should be cheaper and more presure resistant (it should be able to withstand direct torpedo hit). I made thread about it in weaponry 6 months ago.

[edit on 20-2-2005 by longbow]

Originally posted by Lamagraa
I dont think we know the SR-71's top speed I've heard over mach 7 dont know if thats true or not if so thats UBER fast

No, the melting point of the titanium would be reached well before then as well the flashpoint for the fuel that it usues extensivly for cooling the airframe.

Several chronicles point to an A-12 that had a mechanical error in its air speed samplaling and exceeded Mach 3.5 I think and upon landing found that most of the wiring esp in the wing areas were burth almost to the point of failure.

going back a few posts regarding the drag of internal v external weapons.

Its got more to do with cross section, the total cross section of an aircraft (that is to say the total frontal area measured in cubic centimeters) with internal weapons is significantly greater than one without them, even including the weapons and their pylons. It can be thought of in this way, even with internal weapons there must be some space between them inside the bay, this space is contained within the fuselage and adds to the total overall cross section by a much greater amount than the space occupied by a pylon and a bomb say, more cross section always equals more drag. The drag of pylons and missiles is actually smaller because they add less to the overall cross section. The benefits of internal carriage are mainly due to stealth considerations. This was why, after such 50's planes as the Buccaneer, F-102 and F-105 had all had internal weapons bays the format was abandoned in favour of external hardpoints almost universally afterwards. The sole benefit being that external carriage allowed aircraft to be made with smaller frontal areas. The rise of stealth considerations in the last couple of decades, coupled with advances in aerodynamics, has reversed the trend. Though thanks to the law of diminishing returns re thrust and weight it still presents quite an obstacle to acceleration to mach 2 and beyond.


The lack of variable inlets would also be significant in this respect as without flexible airflow management the efficiency of the intake becomes compromised at higher speeds.

The two reasons I've outlined above are, incidentally, also the reason why the Harrier is firmly subsonic despite a thrust/weight ratio well beyond most mach 2 capable fighters. Clearly aerodynamiics have moved on since the Harrier was designed but the laws of physics remain the same.

Originally posted by waynos
going back a few posts regarding the drag of internal v external weapons.

Its got more to do with cross section, the total cross section of an aircraft (that is to say the total frontal area measured in cubic centimeters) with internal weapons is significantly greater than one without them, even including the weapons and their pylons.

Maximun speed is a function of coefficient of drag and frontal area roughly equally. While an internal system will have more frontal area (assuming the weapons are not stacked front to back - which they likely are) - it's cd will be signifigantly lower.

Unless someone on this board has a supersonic capable wind tunnel and perfect scale models of each of these aircraft it is really impossible to tell which is more aerodynamic.

well quite, I was aiming more to present the idea of how external mounts could equate to higher speed, which seems alien to those who have commented upon how fast the Raptor ought to be able to go. I even forgot to mention the reduced structure weight of a 'slimmer' aircraft which would also benefit the planes top speed.

I'm sure the Raptor will do everything asked of it just fine and dandy but sometimes us 'fanboys' can get carried away with our expectations

Originally posted by waynos
I'm sure the Raptor will do everything asked of it just fine and dandy but sometimes us 'fanboys' can get carried away with our expectations

I beginning to think the same, for those of us who dont know how to calculate, we do get carried away. I hate it when someone say oh the SR-71 is so great... it could do mach 5,7,9 etc. Come on, think a little. Just as an example, the J58 engine never exceeded mach 3.6 in known and declassified tests. I have only heard of the SR-71 doing mach 3.8 under SPECIAL conditions, when it was flying over the North pole where the air temperatures are much lower, so the CIT would be less of a problem. What we really need is someone with knowledge of aerodynamics to estimate the potential of the F-22 raptor due to its weight, drag and thrust. I would love to see some calculations.

Originally posted by longbow
Goverment never said that F-22 has 1.4 Mach supercruise. In fact they said it is able to reach 1.58.

Now that i think about it, I have seen some sites say it could do mach around 1.58 in SC and over mach 2 in AB. But I have no doubt it could do more then mach 2 though, probably around mach 2.5-3.0 clean.

Also, STOP GOING OFF TOPIC, please... this is in the aircraft section remember so stop talking about carriers.

[edit on 20-2-2005 by beyondSciFi]

Well, they are aircraft carriers!

Originally posted by Realist05
Well, they are aircraft carriers!

lol, Yeah but can we please be serious? This is about the F-22 and nothing else. So please try and say something that contributes to the discussion.

Back on topic: The should be at least as fast as the F-15, it has more thrust and better aerodynamics(?). The F-15 could do around mach 2.5 under normal conditions if I remember correctly.

[edit on 20-2-2005 by beyondSciFi]

Remember the F/A-22's weight, drag, and thrust (officially) are probably also classified.

Also, the fastest any jet engine can ever get up to is ABOUT Mach 3.5 After that, even state-of-the-art turbine materials start to break down. Also, the pilot themself kind of fades out. Also, a pilot can only go horizontally soooo fast before they actually will pass out and then die even.

To go up to like Mach 4, 5, and 6, you need a ramjet. After that, you need a scramjet to get up to like Mach 20 or 25 but that is the theoretical speee last I checked.

Basically a ramjet works like this: the air flows into the engine constantly (because the jet engine has already taken the craft or missile up to Mach 3.5 and thus shut down). As the air flows into the engine, the inlet funnels the air and basically "rams" it into a space so quickly that it compresses itself. This compression generates a lot of heat because the airflow speed drops so quickly (to mix with the fuel) and thus generates a lot more pressure which means a lot more thrust, hence the up in speed to Mach 6.

The problem is that the faster you go, the hotter the air gets when compressed by the ramjet, and at Mach 6, the air reaches a temperature of 6,000 degrees Fahrenheit (3,300 degrees Celsius).

This basically leads to chemical dissociation. The air rams into the space, begins to combust with the fuel, but because it is so hot, water doesn't form. If water formed at that heat level, a great deal more pressure and thus thrust would be generated. But INSTEAD, the reaction produces free radicals that have a much lower pressure and thrust. Thus, at Mach 6, the ramjet is at its limit and the aircraft will actually start slowing down.

You then need what's called a scramjet. These, theoretically, would allow a speed up to Mach 20 or 25. A scramjet is basically a ramjet that has an inlet valve that takes the air in, but doesn't make the decrease in airflow speed as severe as in the ramjet. Thus, the temperature doesn't go so high as to kill the combustion process.

The problem with a scramjet is the combustion. The air is going at a supersonic speed, yet it has to literally mix with the fuel and combust, all in milliseconds. This is where the engineering details are classified by NASA and the likes.

Missiles have utilized rocket engines and then switch over to ramjets for supersonic flight (to save fuel as rockets burn it up fast).

Basically a theoretical new spacecraft-shuttle would use jet engines, then a ramjet, then a scramjet, then a rocket, to achieve the speed to leave Earth's orbit (thus saving a lot on fuel I guess).

Maybe if Intelgurl is reading, she can expand more.

[edit on 20-2-2005 by Broadsword20068]

Yes, I agree with you that the biggest problems of traveling faster are heat and very little time for the fuel to mix with the air. Although a simple way to avoid excessive heat is to go higher, as the air density decreases there is less friction with the skin of the aircraft therefore allowing greater speeds. Although I dont not see any of these problems for the F-22 as it still uses 'conventional' jet engines and goes well below mach 3.5 where temperature becomes a real problem flying at under 100,000 feet or so. With its SC ability of over mach 1.7 the F-22 should be able to get anywhere around twice as fast as most military jets which is a great leap to say the least.

Yeah; the F/A-22 is meant for improvement though I am sure, so I mean I am sure they could add even newer engines to it in the future and improve upon the design. Also, a LOT of work went into the F/A-22's design, so I am sure they have taken all of these things into account.

This is random, remember in the movie "Indepence Day," when Will Smith pilots the alien aircraft fighter for the first time and he pulls back on the steering wheel and the thing shoots forward and he's like, "I HAVE GOT TO GET ME ONE OF THESE!!" I love that part.

LOL I love that movie. I like all movies with a lot of destruction and aliens. Hehe this being one of the best combinations

Anyway, back on topic. Does anyone what other modern airplanes are capable of super cruising??? I know there are but their names escape me at the moment. Also are they any faster then the F-22 in SC or AB? I would love to know.

Originally posted by longbow
Also the air intakes have not variable geometry (it is hard to make it stealth). So maybe 2.2 mach maximum. The engines are very powerfull, but the aerodynamics allows it not.

Actually the intakes certainly must be variable internally...That engine cannot withstand the direct shock waves produced above mach without variability to break each wave. I am positive there is an internal ramp system that has no effect on stealthy capabilities...Even the F-15 only has one external variable ramp, and 3 others internal that move and schedule on their own.

Originally posted by beyondSciFi
Anyway, back on topic. Does anyone what other modern airplanes are capable of super cruising??? I know there are but their names escape me at the moment. Also are they any faster then the F-22 in SC or AB? I would love to know.

This isn't a definitive list, its just off the top of my head (hey, if you want research go do it )

The first supercruiser was the English Electric P.1 (1954) and its Lightning derivative (RAF 1958 -1988) - Both slower than F/A-22 without afterburners.

Concorde could sustain cruise at mach 2 on dry thrust so thats a faster one (though it used afterburners to reach mach 2 in the first place so its not quite the same thing).

The Eurofighter Typhoon F.2 is the only other service fighter I can think of today that supercruises but it also does so at a lower speed than the F/A-22.

Well according to that link the MiG is massively slower than the Raptor AND the Typhoon on dry thrust alone (the Sea Harrier is only 20 mph slower than the MiG on those figures) but it also states that the F-22 is unable to perform attack missions and this is plain wrong so who knows how valid those figure are?

max speeds are often quoted at 30,000 ft and in many sources these are accompanied by sea level figures as well.

I believe that the Convair B-58 Hustler could maintain supersonic speed after pod detachment and afterburner shut off on it's J-79 engines.
And, at the risk of being scolded for straying off topic, I have also been told that a CARRIER based North American RA-5C version Vigilante could do it, too.
But maybe it go only go that fast if the carrier that launched it was travelling 55 knots!

[edit on 21-2-2005 by Realist05]