F-22 Raptor speed

sferrin · by **sferrin** » 29 Sep 2006, 01:04

Probably a can of worms but...

A quote from another board:

Some snippets from that article

Raptor Rocks
Airspacemag Aug-Sept 2006

Shower was joined at Oshkosh that day by Col. Thomas Bergeson, who entertained us with high-speed, excruciatingly loud passes in another Raptor while Shower flew off to collect his airplane for its next stunt. One of them he calls "the helicopter." The airplane is falling straight down, but rotating in a spin. This is one of Shower’s favorites—the guy must have a stomach made of titanium.

The jet can sustain over 30 degrees per second of yaw, he marvels. "Thirty degrees per second in an F-15? The beeper’s going off and I’m in an uncontrollable spin. But in an F-22, it’s totally controllable, and you’re just going ‘dit da dit da duh,’ " he hums. "And I’ll push the pedal the other way, and it will just stop and go 30 degrees in the opposite direction." Shower laughs in gleeful disbelief that an airplane will allow him to have this much fun.....

He’s seen demos and videos of performances by the Russian MiG 29 and Sukhoi Su 35, and admits that their maneuverability is probably on a par with the F-22. "I can do everything they can do and vice versa," he says. "We can all do some pretty neat stuff. But I love this part of it: That’s all they have. They don’t have the stealth , they don’t have the supercruise, they don’t have the integrated sensors, the avionics. We have an aircraft that does everything a fighter pilot has ever wanted to do. It has it all—you can tell by the price tag," he says, (about $137 million per copy, or $338 million if you count in all the Air Force's research costs).

For their performance, which started at 2:40 p.m., Shower and Bergeson took off from Langley, 800 miles away, at about 1:25. "We were going slow," Shower says. "We were only doing about .9 Mach. Over the continental United States, there’s only a couple of places we’re allowed to go supersonic so we don’t scare everybody. But we did the math and figured we could be there if we supercruised in about 25 or 30 minutes.

25 minutes = 1920 mph
30 minutes = 1600 mph

Informed comments preferred please. (I can come up with all the uninformed ones myself thanks

)

LinkF16SimDude · by **LinkF16SimDude** » 29 Sep 2006, 01:20

But we did the math and figured we could be there if we supercruised in about 25 or 30 minutes."

25 minutes = 1920 mph
30 minutes = 1600 mph

And that's prolly in the mid to high 40's. Above the commerical stuff. Take it to something 'round 50K to 60K (where the Mach is lower) and it may even be a touch faster! :twisted:

idesof · by **idesof** » 29 Sep 2006, 01:26

Definitely a can of worms. Now, I am pretty certain the Raptor can do Mach 2 supercruise despite all the naysayers (based on a variety of sources including Dozer's now deleted remarks, which I will not repost out of respect). Now, as for the figures above, quite simply, no f*cking way. Just, impossible. Speed of sound at 30,000 ft. is 678.2 mph. That means 1,600 mph is Mach 2.36. No way. Even LESS way is 1,920 mph, which is MACH 2.83!!! Are you sure it's 800 miles away, and not 800 kilometers. Hey, if NASA and Lockheed can f*ck up metric and English measurements and lose a billion-dollar spacecraft, I'm sure a reporter and/or a couple of pilots can as well!

idesof · by **idesof** » 29 Sep 2006, 01:30

What IS interesting, and revealing (and I think these two pilots may be court-martialed, by the way), is that they talk about supercruising for 25 to 30 minutes. I've read some ridiculous figures that maintain the Raptor can only supercruise for five minutes (!!!). If it can supercruise for at least 25 to 30 minutes, do the math. It's range, as I've maintained, is very impressive then, even at Mach 1.72, its generally-accepted supercruise speed.

sferrin · by **sferrin** » 29 Sep 2006, 01:33

idesof wrote:Definitely a can of worms. Now, I am pretty certain the Raptor can do Mach 2 supercruise despite all the naysayers (based on a variety of sources including Dozer's now deleted remarks, which I will not repost out of respect). Now, as for the figures above, quite simply, no f*cking way. Just, impossible. Speed of sound at 30,000 ft. is 678.2 mph. That means 1,600 mph is Mach 2.36. No way. Even LESS way is 1,920 mph, which is MACH 2.83!!! Are you sure it's 800 miles away, and not 800 kilometers. Hey, if NASA and Lockheed can f*ck up metric and English measurements and lose a billion-dollar spacecraft, I'm sure a reporter and/or a couple of pilots can as well!

Well firstly since it's a DIRECT quote of the Raptor pilot who made the flight I'd assume he'd know how far he had to fly. Secondly I double checked the as-the-crow-flies distance with Google Earth and got 799 miles. (If you were wondering about Google Earth's accuracy I was able to zoom in on a parked B-2 and measure it's wingspan at 172 feet so it ain't too shabby

idesof · by **idesof** » 29 Sep 2006, 01:37

sferrin wrote:Well firstly since it's a DIRECT quote of the Raptor pilot who made the flight I'd assume he'd know how far he had to fly. Secondly I double checked the as-the-crow-flies distance with Google Earth and got 799 miles. (If you were wondering about Google Earth's accuracy I was able to zoom in on a parked B-2 and measure it's wingspan at 172 feet so it ain't too shabby

All I can tell you, then, is that this is going to be all over the net, people are going to be freaking out, there will be chaos and mayhem in the streets, and these pilots will be court-martialed. I am only slightly exaggerating. If there isn't some sort of mistake, and these pilots didn't just loose their math marbles, this is seriously, seriously f*cked up. Unbelievable. As in, I just can't believe it. There must be some reasonable explanation...

LordOfBunnies · by **LordOfBunnies** » 29 Sep 2006, 01:52

Guys, if you can find me the nose angle on the F-22, I can tell you max design Mach number. It's called the Theta-Beta-Mach relation. It's in every basic aerodynamics book. There's this really cool looking graph you get to use and everything. I have a strange feeling that information is classified so I really don't want to know.

sferrin · by **sferrin** » 29 Sep 2006, 02:51

LordOfBunnies wrote:Guys, if you can find me the nose angle on the F-22, I can tell you max design Mach number. It's called the Theta-Beta-Mach relation. It's in every basic aerodynamics book. There's this really cool looking graph you get to use and everything. I have a strange feeling that information is classified so I really don't want to know.

You sure there aren't exceptions? Look at the Shuttle. It's got a pretty dull nose and it goes pretty fast. Then consider things like Talos (Mach 3) and ASALM (Mach 5.5). Forget the F-22 for the moment, do those match up to the "Theta-Beta-Mach" relation? I think we'd both agree that sharp doesn't necessarily mean fast (X-3) but does dull or not as sharp always mean slow?

LordOfBunnies · by **LordOfBunnies** » 29 Sep 2006, 03:08

You WANT an oblique shock on the F-22 or any other jet. This is because you'll get less wave drag, pressure loss, aero heating with oblique shocks. That would mean the flow would be subsonic around at least part of the jet which would cause all sorts of weird things. When dealing with things that are meant to go supersonic, sharp means better because you'll get less drag. Oblique shocks are just normal shocks at an angle, but you get better aerodynamic properties with them.

Its all about analysis, if you need a round nose for say IR tracking, well you'll need a more powerful rocket motor to get it up to that speed. But you can also use the rocket motor as part of your explosive if you're trixy about it and have any of it left. You can't go as fast with a normal shock in front of you. I can go into a full aerodynamics lecture on this subject, but I'd have to wait until the weekend (homework and all that fun stuff).

As for the shuttle, well it's design condition is for blunt body reentry. That's why it has the ginormous rocket engines to get it into space. It reenters at about Mach 30 or so. With the normal shock relations you get a temperature rise of about 17000 K. This would normally melt EVERYTHING, but the air ionizes and only rises about 7000 K or something like that. It uses this to slow down, if it were a sharp shape, you'd get even larger temperature rises on the leading edge.

My main point is, you just need more power to go with a normal shock, it's not impossible just harder. The F-22 WILL generate oblique shocks just like every other fighter (except maybe the early ones like Me-262 and F-86).

Arrrrr, the laws of science be a harsh mistress.

sferrin · by **sferrin** » 29 Sep 2006, 03:18

LordOfBunnies wrote:You WANT an oblique shock on the F-22 or any other jet. This is because you'll get less wave drag, pressure loss, aero heating with oblique shocks. That would mean the flow would be subsonic around at least part of the jet which would cause all sorts of weird things. When dealing with things that are meant to go supersonic, sharp means better because you'll get less drag. Oblique shocks are just normal shocks at an angle, but you get better aerodynamic properties with them.

Its all about analysis, if you need a round nose for say IR tracking, well you'll need a more powerful rocket motor to get it up to that speed. But you can also use the rocket motor as part of your explosive if you're trixy about it and have any of it left. You can't go as fast with a normal shock in front of you. I can go into a full aerodynamics lecture on this subject, but I'd have to wait until the weekend (homework and all that fun stuff).

As for the shuttle, well it's design condition is for blunt body reentry. That's why it has the ginormous rocket engines to get it into space. It reenters at about Mach 30 or so. With the normal shock relations you get a temperature rise of about 17000 K. This would normally melt EVERYTHING, but the air ionizes and only rises about 7000 K or something like that. It uses this to slow down, if it were a sharp shape, you'd get even larger temperature rises on the leading edge.

My main point is, you just need more power to go with a normal shock, it's not impossible just harder. The F-22 WILL generate oblique shocks just like every other fighter (except maybe the early ones like Me-262 and F-86).

Arrrrr, the laws of science be a harsh mistress.

I understand that but take a look at the noses of Talos and ASALM they're both relatively squat.

PhillyGuy · by **PhillyGuy** » 29 Sep 2006, 03:20

idesof wrote:What IS interesting, and revealing (and I think these two pilots may be court-martialed, by the way), is that they talk about supercruising for 25 to 30 minutes. I've read some ridiculous figures that maintain the Raptor can only supercruise for five minutes (!!!). If it can supercruise for at least 25 to 30 minutes, do the math. It's range, as I've maintained, is very impressive then, even at Mach 1.72, its generally-accepted supercruise speed.

There really would be no point to trump the Raptor's supercruise capability and to put such an emphasis on it, design and performance wise, if it could only do it for five minutes, so I think those figures are bull. And I don't think the fact that the F-22 can supercruise for an extend period of time is that unknown either. Just last night the History Channel had a special about stealth aircraft and mentioned that the F-22 can supercruise for nearly a half an hour.

Also, as I understood it Dozer said there were a few places in the CONUS where they could go supersonic, perhaps they included that in their time calculation? It would make sense, time wise. BTW (in my personal opinion) I think the F-22 can probably supercruise around Mach 1.8

LordOfBunnies · by **LordOfBunnies** » 29 Sep 2006, 03:40

AHA I've figured out the mysteries of the Talos and ASALM. They are both ramjet powered, the Talos is designed to generate a normal shock at the entrance to the ramjet section. A ramjet requires that to work properly. It then generates obliques everywhere else that's needed. You see sloped surfaces around what seems to be the engine entrance to generate obliques around the normal.

The ASALM (which is a bit** and a half to find pictures of) also seems to be rather sharp where it counts. It's also ramjet powered, so it has to generate a normal shock in front of its entrance. It seems pointy enough to generate the right oblique shocks (top and bottom). Design condition is where the oblique shock hits the engine lip. It might generate strong oblique shocks (most oblique shocks are called weak shocks) on the sides, but again, I'd need more precise measurements of the angles in question.

It's the big missile looking thing under the wing.

sferrin · by **sferrin** » 29 Sep 2006, 03:53

Yeah ASALM is one of those things that make me go "WTF were they thinking when they cancelled it". Anyway think I'd rather end this "what is a shockwave" line and get back to the original topic (not that I don't find it interesting but I'd rather have the original topic addressed rather than the subtopic as I'd rather not have the thread waunder.)

Raptor_One · by **Raptor_One** » 29 Sep 2006, 04:10

Why do you guys insist on trying to predict an aircraft's performance capabilities based on statements like these? They tell you nothing. Aircraft don't start off at point A at their cruising altitude and cruising airspeed, nor do they end at point B at those conditions. The distance covered in climb and descent (especially in airspace dominated by lots of civilian traffic) is not insignificant.... not at all. You're also not taking into account the distance covered actually accelerating up to maximum supercruise velocity (whatever that may be). They accelerate in AB, but even so it's not going to be an insignificant distance covered. You cannot infer anything from these kinds of statements. There are too many variables that are unknown. I don't understand the need to convince oneself that an aircraft can go really really fast. At least not in this fashion. It's not an engineering analysis so holds no real merit. It's just silliness.

sferrin · by **sferrin** » 29 Sep 2006, 04:16

Raptor_One wrote:Why do you guys insist on trying to predict an aircraft's performance capabilities based on statements like these? They tell you nothing. Aircraft don't start off at point A at their cruising altitude and cruising airspeed, nor do they end at point B at those conditions. The distance covered in climb and descent (especially in airspace dominated by lots of civilian traffic) is not insignificant.... not at all. You're also not taking into account the distance covered actually accelerating up to maximum supercruise velocity (whatever that may be). They accelerate in AB, but even so it's not going to be an insignificant distance covered. You cannot infer anything from these kinds of statements. There are too many variables that are unknown. I don't understand the need to convince oneself that an aircraft can go really really fast. At least not in this fashion. It's not an engineering analysis so holds no real merit. It's just silliness.

So are you saying you know more about what the F-22 can or can't do than the PILOT? You spend a lot of effort and bluster in an attempt to force people to agree with you it seems without ever addressing the issue. Why did the pilot say what he did?