Listed Performance vs Real Performance

[r16]

sticking out my neck without any proof I have claimed in a couple of places that the maximum capabilities for the SR-71 is 58 000 m altitude and Mach 4.5 . Anyhow only once there was a response on that and a poster who had talked to a test pilot said they could cruise at Mach 4.25 .I don't believe a Mach 5 or even higher capability or "Mach 3 over rooftops over Baghdad " as Ben Rich once claimed in Reader's Digest . I am afraid many of the stories can well be hunters' tall tales . SR-71 is a superb aircraft but not that superb.

 

[Lee]

KJ_Lesnick, quoted: "It would appear as if the USAF for one reason or another did not classify it."

Maybe the top brass at the Pentagon thinks the average public isn't smart enough to figure
these things out? I can.





Kj: "The footage I've seen of the blackbird at low altitude seems to suggest it flying at a few thousand feet."

Well, my Air Force correspondants said the leakage wasn't terribly sever, since the fuel was pretty thick in the tanks.





KJ: "Like during the early Archangel and Angel series...?"

I don't know about those programs. (I borrowed a library laptop and I'm both time limited and unfamiliar with it, or I'd research the subject before responding with more precise information. Sorry to be less than knowledgeable.)





KJ: "The A-2 had in addition to a pair of J-58's, a pair of ramjets with pentaborane. That you mean?"

I can say something about that: I do know the X-15 was fitted with a ramjet to experiment on, but whether or not boron-based fuels was burned in it is unknown to me. The Blackbird had pentaborane-burning ramjets? I didn't know that. (I admit there's a lot I don't know about the Blackbird.)





Kj: "Clarence L. "Kelly" Johnson died in 1990 at the age of 80 (b. 1910)."

Well, I knew he was from the same time frame as my Dad. He and his whole design team were smart engineers!! He was quoted as saying to a junior subordinate, "Don't prostitute yourself for the money. Build a plane you believe in." Many engineers probably don't think like him any more. He was an expert.





KJ: "So the airplane would reach 1,000 C to 1,200 C without active cooling during cruise?"

I suppose the Blackbird did if it went Mach 5? But if duration was short at that speed, temperatures would also probably not get that high.





Kj: "Would active cooling (JP-7 circulated through the chines) sh'ave off 450-500 F (like you said pertaining to an aircraft with a 650 C skin temp I think),...

It could. IF enough fuel was circulated to carry away the heat. (This computer won't let me highlight text.) I think it was Bernouilli(spelling?---the Italian physicist) said as much. More fuel means lower temperature UP TO the point where it cokes up and clogs the lines and filters.






KJ: "...or would the cooling benefit be less at such extreme temperatures?"

Flying higher is an easy way to avoid aerodynamic heating. Fuel circulation does benefit from lower speeds, yes.

 

[KJ_Lesnick]

sticking out my neck without any proof I have claimed in a couple of places that the maximum capabilities for the SR-71 is 58 000 m altitude and Mach 4.5 . Anyhow only once there was a response on that and a poster who had talked to a test pilot said they could cruise at Mach 4.25 .I don't believe a Mach 5 or even higher capability or "Mach 3 over rooftops over Baghdad " as Ben Rich once claimed in Reader's Digest . I am afraid many of the stories can well be hunters' tall tales . SR-71 is a superb aircraft but not that superb.

Where did you derive the 58,000 meter figure from if I may ask?

Maybe the top brass at the Pentagon thinks the average public isn't smart enough to figure
these things out? I can.

Well, I doubt it was a serious leak. The Russians after all have seen the Blackbird at it's fastest when frantically trying to intercept it and failing. Although the shock-pattern might have revealed that the J-58 for it's mass-flow, pressure-ratio, etc produced more thrust as well, as engine thrust is a function of the amount of mass being discharged out the back in a given amount of time versus the speed of the exhaust.

I don't know about those programs. (I borrowed a library laptop and I'm both time limited and unfamiliar with it, or I'd research the subject before responding with more precise information. Sorry to be less than knowledgeable.)

The A in A-12 stands for Archangel. There were apparently 12 Archangel-designs with the addition of the Arrow series, and Angel series -- all of which were designed for high-altitude, and high-speed. A-1 was J-58 powered, A-2 had J-58's and large-diameter ramjets as well: Since they used pentaborane, they were done away with.

I can say something about that: I do know the X-15 was fitted with a ramjet to experiment on, but whether or not boron-based fuels was burned in it is unknown to me. The Blackbird had pentaborane-burning ramjets? I didn't know that. (I admit there's a lot I don't know about the Blackbird.)

From what I read it was an axisymmetrical scramjet fitted on the underside of the X-15. I have no idea what kind of fuel it burned but in one high-speed flight the model was melted.

As for the Blackbird, it didn't have pentaborane burning ramjets. One of the Archangel-designs, (A-12 being the first of the Blackbirds) the A-2 featured a pair of pentaborane burning ramjets in addition to two J-58's. It never flew though.

Well, I knew he was from the same time frame as my Dad. He and his whole design team were smart engineers!! He was quoted as saying to a junior subordinate, "Don't prostitute yourself for the money. Build a plane you believe in." Many engineers probably don't think like him any more. He was an expert.

And he didn't prostitute himself to win a contract either! They could have won the F-16 contract for example if they just made a design that fit the specifications the USAF wanted then as time went on simply added extra fuel capacity and made modifications. Ironically the F-16 would feature increases in fuel capacity much as Kelly Johnson assumed would be needed.

It could. IF enough fuel was circulated to carry away the heat. (This computer won't let me highlight text.) I think it was Bernouilli(spelling?---the Italian physicist) said as much. More fuel means lower temperature UP TO the point where it cokes up and clogs the lines and filters.

Honestly I don't know how much fuel was circulated through the chines, or how rapidly it was pumped through the. I assume the passageways the fuel would be cycled through would consist of numerous very small passageways since that would be the more efficient however.

Flying higher is an easy way to avoid aerodynamic heating. Fuel circulation does benefit from lower speeds, yes.

How much heating does it save you at high-altitude? I just thought it saved a little and the major difference was the plane simply heated up slower than at lower altitudes.

I guess the cooling-benefits being better at lower speeds is an example of diminishing returns.


Kendra Lesnick

 

[Lee]

r16, quoted: "...capabilities for the SR-71 is 58 000 m altitude"
KJ_Lesnick, quoted: "Where did you derive the 58,000 meter figure from if I may ask?"
58000m ~= 179,000 ft. I would also ask if that's a typo?



KJ: "The Russians after all have seen the Blackbird at it's fastest when frantically trying to intercept it and failing."
There was a writeup(I think in Aviation Week(?) years ago that I never forgot:
2 Mig Foxbats intercepted a Blackbird and kept the SR-71 from completing its mission. Honest! The Pentagon probably sat up and took notice, to put it mildly. The point I'll try and make here is that the latest engines for the Foxbats and Foxhounds are big enough and have a high enough compressor pressure ratio that speed and low fuel consumption are a positive factor in enabling their success against even the Blackbird. We need an Aurora to get away from the newest Mig-25's and -31's.



KJ: "Although the shock-pattern might have revealed that the J-58 for it's mass-flow, pressure-ratio, etc produced more thrust as well, as engine thrust is a function of the amount of mass being discharged out the back in a given amount of time versus the speed of the exhaust."
Sure, makes sense. As I implied above, adding one or more stages to an engine will benefit top speed of a plane.



KJ: "A-1 was J-58 powered, A-2 had J-58's and large-diameter ramjets as well: Since they used pentaborane, they were done away with.
I would say more information concerning the A-12 was declassified than I thought. Even so, the really important facts are still classified. Here's one from an obsolete design: The top speed of the B-58---for real with no disinformation. I've only heard the rumor of Mach 3 for a few minutes.



KJ: "...an axisymmetrical scramjet fitted on the underside of the X-15. I have no idea what kind of fuel it burned but in one high-speed flight the model was melted."
Can't say I'm surprised at that speed. Boranes have a high heat of combustion, but B2O3 in the exhaust cause more problems than are worth it to try and fix.



KJ: "As for the Blackbird, it didn't have pentaborane burning ramjets. One of the Archangel-designs, (A-12 being the first of the Blackbirds) the A-2 featured a pair of pentaborane burning ramjets in addition to two J-58's. It never flew though."
I never heard of that. Where did you learn of this?



KJ: "They could have won the F-16 contract for example if they just made a design that fit the specifications the USAF wanted then as time went on simply added extra fuel capacity and made modifications. Ironically the F-16 would feature increases in fuel capacity much as Kelly Johnson assumed would be needed."
You know how it is: Politics is politics. Kelly Johnson knew what would work. My dad had a knack for the same thing. He was an aerospace engineer for only about 30 years.



KJ: "Honestly I don't know how much fuel was circulated through the chines, or how rapidly it was pumped through the."
I saw a science experiment in high school:
A small copper tube with high pressure water flowing through it was heated with a butane torch. Nothing happen to the tube until the water pressure was stopped. Tube melted.
My point is: It isn't the type of fluid that carries away the heat, but enough is needed to do the job. Even JP-4 at Mach 6 should be okay as long as the fuel tanks are well insulated.



KJ: "I assume the passageways the fuel would be cycled through would consist of numerous very small passageways since that would be the more efficient however."
That would be reasonable. Added cost, however, might be an engineering tradeoff to be considered as well as possibly increased weight and lower reliability?



KJ: "How much heating does it save you at high-altitude? I just thought it saved a little and the major difference was the plane simply heated up slower than at lower altitudes."
I saw a graph in an old NTRS archived report that showed adding 20,000 ft above about 75,000 would lower aerodynamic nose temperatures by around 10%. Adding another 20,000 more would take off another 10%.



KJ: "I guess the cooling-benefits being better at lower speeds is an example of diminishing returns."
Right. Adding speed after Mach 4.5-5.0 will increase skin temps dramatically.

(I'm trying different things with my responses. Is the Italics a chore to read, KJ? I can go back to what I was doing, but this shortens the length of the 'Web page, which is what I was experimenting with.)

 

[KJ_Lesnick]

Lee,

58000m ~= 179,000 ft. I would also ask if that's a typo?

Uh, I got 190,286.4 ft (58,000m x 3.2808 = 190,286.4ft)

There was a writeup(I think in Aviation Week(?) years ago that I never forgot:
2 Mig Foxbats intercepted a Blackbird and kept the SR-71 from completing its mission. Honest! The Pentagon probably sat up and took notice, to put it mildly. The point I'll try and make here is that the latest engines for the Foxbats and Foxhounds are big enough and have a high enough compressor pressure ratio that speed and low fuel consumption are a positive factor in enabling their success against even the Blackbird. We need an Aurora to get away from the newest Mig-25's and -31's.

When did that happen, what year about?

Is that the one you were talking about where one MiG-25 was in front of the plane and one was behind the MiG-25 as the Blackbird passed by and sprung the trap? I do recall reading about a couple of close calls where the MiG-25's and possibly MiG-31's were able, had they fired their weapons, to shoot down the Blackbird.

Regarding the MiG-25: They actually were able to significantly increase the maximum-speed of the Foxbat over the earlier models? I always thought they were all capable of about the same speed considering the plane had some aluminum in its structure. I also never thought they made any significant modifications to the Tumansky R-15 turbojet either.

I had a feeling though that the MiG-31 would have been faster than the MiG-25 even though it's not acknowledged because it had more titanium in it's structure. I have a feeling the Soloviev D-30-F6 was a dramatically different engine than the regular D-30 that powers the Tu-134 and some Il-62 variants, (And I don't just mean because it has an afterburner, the engine would have to have much higher turbine and compressor inlet temperatures. I guess it has as much in common with the regular D-30 as the JT-9A/J-91 does with the JT9D which are totally different) though!

As an interesting note: While it's been acknowledged, the USAF isn't very fond of admitting it though: The F-15 can achieve the same top-speed the MiG-25 can and was designed as such. Whether it could fly as long a supersonic combat-radius that the MiG-25 could fly, I have no idea though. The windscreen of the F-15 according to what I've been told at least on early models could not withstand prolonged flight at maximum-speed due the high temperatures. However McDonnell-Douglas re-designed a new windscreen and it was at least refitted to some F-15's allowing maximum-performance safely.

Interestingly, in the early 1980's, the USAF performed an excercize called "Eagle-Bait" to see how effective a MiG-25, or an F-15 would be at intercepting a Blackbird (using an F-15) as the F-15 and MiG-25 had the same speed (and apparently provision for the same) altitude capabilities: The excercize unfortunately was totally unrealistic: The Blackbird was to fly in virtually a straight line and at a reduced speed and had limits as to what kind of maneuvers it could do. Needless to say there was lots of whining, bragging, b*tching and moaning that followed. In case you were wondering, at least one F-15 managed to carry out a successful simulated intercept. (The US Navy did a similar excercize with F-14's which while probably slower, have the ultra long-range AIM-54 Phoenix missile -- The F-14 crews, while they definetly wanted to win, were able to handle the whole exercise in a much more sportsmanlike manner)

Sure, makes sense. As I implied above, adding one or more stages to an engine will benefit top speed of a plane.

To the best of my knowledge all J-58's from the first design developed in 1956, to the version that powered the Blackbirds utilized a nine-stage compresor and a twin-stage turbine: Sure the airflow was increased, metallurgy changed, blade-geometry altered, the bleed-bypass system added, air-cooling increased, an engine-trim and de-rich added for the combustor and afterburner, active cooling for the engine compressor and afterburner, and who knows what else... but to my knowledge they all featured a nine-stage compressor, twin-stage turbine. I could be wrong of course...

I would say more information concerning the A-12 was declassified than I thought. Even so, the really important facts are still classified. Here's one from an obsolete design: The top speed of the B-58---for real with no disinformation. I've only heard the rumor of Mach 3 for a few minutes.

Of course. Even if the plane's outdated I guess they don't want it to be known that: "You mean I could have done Mach-5+ without a pure-ramjet, using a cleverly modified turbojet with a bypass system and active cooling instead and I could have built the plane out of just a high-temp titanium alloy and didn't need all this inconel and exotic composites and superalloys!!??" or give anybody ideas.

I've heard claims of Mach-3 capability out of a B-58 as well. I've even heard claims that they could have attained that speed a little bit longer than just a few minutes and possibly some evidence to go with it.


1.) A B-58 early on flew from Washington State to Texas in 70 minutes with an average speed of 1,310 mph.

2.) Numerous claims that the B-58 due to either it's honeycomb structure, or the particulars of it's construction allowing speeds substantially faster than most aluminum-skinned airplanes

3.) The plane's supersonic range was 4,000 nm. Since afterburners consume more gas than dry-power even at low-AB (The J-79 had a five-setting AB) the plane's endurance is much more limited in terms of flight-time which shortens your range unless you go extremely fast. The B-58 actually couldn't quite equal it's subsonic range while supersonic (4,000 nm Supersonic vs 8,000 nm Subsonic), but considering the fuel-burn of 4 J-79's at full power with low-AB, they would have probably had to have gone pretty fast even with all the fuel carried in that pod to have eaten up 4,000 nm. Probably in excess of Mach-2 at least.

4.) Continuous afterburner is not the best choice for sustained supersonic flight with engines of the mid 1950's to late-1960's unless you plan to fly for at mach-numbers in excess of 2.5 typically. For example...
- Boeing 733-197/Boeing 733-290/Boeing 733-390/Boeing 2707-100/B-2707-200: (SST-design -- not built but designed to operate on continuous low-AB) Mach 2.7
- Lockheed L-2000 (SST-design -- not built but designed to operate on continuous low-AB) Mach 3.0
- North American XB-70 Valkyrie: At least Mach 3.0 (Possibly as high as Mach 4: The chief-engineer said the inlets were designed for Mach 4 use, and the J-93 can operate at Mach-4)
- Lockheed A-12/YF-12/SR-71/M-21 Blackbird: Hypersonic

I never heard of that. Where did you learn of this?

I have a couple of books about the Blackbird. I actually don't know which one actually showed the pictures. But at least one or two did.

You know how it is: Politics is politics. Kelly Johnson knew what would work. My dad had a knack for the same thing. He was an aerospace engineer for only about 30 years.

What company did your dad work for?

I saw a science experiment in high school:
A small copper tube with high pressure water flowing through it was heated with a butane torch. Nothing happen to the tube until the water pressure was stopped. Tube melted.
My point is: It isn't the type of fluid that carries away the heat, but enough is needed to do the job. Even JP-4 at Mach 6 should be okay as long as the fuel tanks are well insulated.

Although the flow rate and pressure to carry away the heat is obviously very important, I still figured the fluid being used mattered as well to a point.

That would be reasonable. Added cost, however, might be an engineering tradeoff to be considered as well as possibly increased weight and lower reliability?

I don't know exactly how much room there is in the chine to shuffle fuel through, not counting the aircraft's structure which can be worked around, there also are 4 chine-bays to my knnowledge and a bunch of smaller bays and who knows what else.


I saw a graph in an old NTRS archived report that showed adding 20,000 ft above about 75,000 would lower aerodynamic nose temperatures by around 10%. Adding another 20,000 more would take off another 10%.

Wow. I thought only a small reduction would be present and the only major difference would be how fast you'd heat up.

Right. Adding speed after Mach 4.5-5.0 will increase skin temps dramatically.

Yeah, but honestly I have serious suspicions the Blackbird is capable of flying a lot faster than Mach 5 considering the very special high-temp titanium-alloys used, the fuel circulated through the chines, the active cooling of the engines in combination with all the modifications to the J-58 which before any modifications could do Mach 4.

(While I'm not sure about this part, and maybe I'm wrong here: But considering it takes time for an airframe to heat up, even though it happens faster at high-speeds -- I still wonder if the X-15 flew a bit faster than the speed actually listed if it reached those temperatures during a 90 second, maybe two minute burn especially with a blunt nose that rejects heat better than a sharp one. From what I remember Mach 3 yields you around 500-something temperatures. With a plane designed like the X-15 to reject heat with the chines, 1,200 sounds like a Mach 6 temp in level continuous flight maybe add 250 degrees farenheit.)

(I'm trying different things with my responses. Is the Italics a chore to read, KJ? I can go back to what I was doing, but this shortens the length of the 'Web page, which is what I was experimenting with.)

It's legible, but I guess it's just something to get used to. I guess I'd have to see it a couple of times to get used to it ;D


Kendra

 

[r16]

writing from a web cafe where time really equals money :

I have to read whole topics but I can say I am not to be taken seriously .Still as it was in the that comics page in USAF's official magazine that when an SR-71 asked for a flight level far higher than seemed possible , the controller laughed and cleared it on the basis of "if you can " and the SR-71 pilot declared that he was now descending , it seems reasonable - to me .

Russians didn't need gunfire to bring down a SR-71 , so matching its flight performance is irrelevant .It was always interceptable , right from the start ; though SA-2 is not the proper tool for it . North Vietnamese and Koreans fired them to show that they knew it was there . The untouchibility if I may say of the Blackbird is a huge propaganda issue . And Russians are not intimidated by that CIA object.

and here is what I had written at home to be carried by my flash drive :

after reading the whole topic at home

streching it a bit probably half of the initial points are arguably true ; F-100 wings flew on Mach 2 F-100B or '107 . Likewise the twice faster F-102 is 102B or '106 . Phantoms would be doing Mach 3 if they had arrived in 1966 , in 76 they were a threat to the Eagle which tries to avoid going really fast .Armed maximum speed should be Mach 1.78 and I understand that the pilot actually has to press a button to go faster ; one ( famously ?) lost its wingtip in 1991 while chasing a target over N.Iraq .

but all these cases require massive redesign of the basic airframe in a way not available to the USAF flightline .

a final point about the humble Hun is that it goes faster without a pilot - those drones by Tracor were Mach 1.5 if I remember it correctly.

 

[KJ_Lesnick]

Why do they try to avoid flying the F-15 Eagle really fast?

 

[r16]

while this site is slightly different from say What if Speculative modelling , where I am capable of giving alternative histories and wild explanations I will start again with my homework

-in case of a question about source

"...The F-15 met the Mach 2.5 requirement ,but only with great effort and expense. The maximum speed can only be achieved by flipping a special 'VMAX' switch on the cockpit sidewall , and the engines need to be removed for inspection afterwards .In practical terms , an armed Eagle is limited to Mach 1.78."

Fighter by Jim Winchester ,Parragon 2004 , page 250

regarding Lockheed winning F-16 contract , isn't that the X-27 Lancer ? If so , I really doubt that since it was nearly a decade late in coming ; Johnson did fail in providing a supersonic "fighter" to USAF and Lockheed did make a disservice to West with all that bribing . The Starfighter was spectacular as a fast flying low level attack aircraft , but a lot more pilots would see their grandchildren if Skunk Works had delivered the Lancer earlier . The market was theirs anyhow.

plus the original idea was to have a couple of airframes for testing and maybe some DACT in their later days . It was US Congress that forced large scale purchases against the wishes of American services . Boeing even offered the Mirage 1.Though I have seen on this forum that they also had a supermodel size F-16 , which was the front runner for "buy two" option . When it became clear that the winner was to be for "buy two thousand" option , the Falcon got the nod. Not because it outturned or outrolled the '17 , because it had the F-100 engine . It secured F-15 funding by dropping the unit price of the engines as everyone knows ; what is more J-101 development would give a replacement for J-79s on the Phantom and that would be something undesirable . But for the Swedes and the overwhelming desire to kick Tomcat out in the 21st century F-404 would have remained at 16 000 pounds , assuming of course it was accepted in the first place .

offering a service type aircraft for a decidedly non service type competition isn't foresight . Say in 1968 Lancer would be hugely popular over Vietnam . For a 1978 service introduction it is a bit passe .

one pities Americans for they have to tar and feather their weaponry to replace them in time. I was struck by the Mach 1.78 statement . I really like the AbleFiveDog Skylark ; that is what I call it time to time. It looks better than this Lightning thing . See , USAF still remembers the P-38s over Germany in 1943...

until I am given notice to be more serious I will be telling such tales .

and limiting structural strength to make the aircraft more fiscally reasonable is not an American specialty . Mig-29 becomes a 7G aircraft from a certain speed , according to an assesment by Roy Braybrook in an Air International article .His source was a GD press release .

 

[Lee]

[quote author=KJ_Lesnick,quoted: "Uh, I got 190,286.4 ft (58,000m x 3.2808 = 190,286.4ft)"

I used 3.1 ft/meter from memory. A meter is about 3.3 ft, rounded up. That's why my estimate was low.

Lee: There was a writeup(I think in Aviation Week(?) years ago that I never forgot:...

KJ: "When did that happen, what year about?"

I'm not sure, I think it was in Aviation Week or another industry magazine, but,
I may have heard a rumor???

http://www.wvi.com/~sr71webmaster/mig25.html
http://aeroweb.lucia.it/rap/RAFAQ/MiG-25.html

These sources are giving conflicting information. However, I never forgot what I read because I thought, like everyone else, the Blackbird was impervious to attack from ahead or astern. The mig's convinced the SR-71 pilot to turn back. With the information above, now I don't know. What do you think?





KJ: "As an interesting note: While it's been acknowledged, the USAF isn't very fond of admitting it though: The F-15 can achieve the same top-speed the MiG-25 can and was designed as such."

It was?? Well, I think I can shed some light on the subject. I know the formula to determine the flight characteristics(lift, max. speed., thrust horsepower) to try and prove one way or another that the F-15 can go Mach 3 at, say, 80,000 ft. I can add to this post later or modify it later. Running out of time. Sorry; will keep you posted.





KJ: "What company did your dad work for?"

He started at Boeing in Seattle after graduating from the Univ. of Cincinnati. (They STILL have an aerospace Bachelor's program after over 55 yrs. of instruction.)
Later he went to S. calif to be nearer to his father and worked at McDonnell Douglas. (No longer doing business.)

 

[KJ_Lesnick]

I used 3.1 ft/meter from memory. A meter is about 3.3 ft, rounded up. That's why my estimate was low.

Understood.

http://www.wvi.com/~sr71webmaster/mig25.html
http://aeroweb.lucia.it/rap/RAFAQ/MiG-25.html

These sources are giving conflicting information. However, I never forgot what I read because I thought, like everyone else, the Blackbird was impervious to attack from ahead or astern. The mig's convinced the SR-71 pilot to turn back. With the information above, now I don't know. What do you think?

I do remember reading that there were several times during the 1970's or 1980's, not sure which, in which at least two MiG-25's, maybe MiG-31's, managed to pull off various intercept tactics that had they fired would have likely downed the Blackbird.

But it is very fascinating that in one of those sources it mentions that the claim that the R-15 was designed for a cruise-missile is not actually true; it was designed for a MiG testbed. The thing is, they didn't have any plane that was designed to operate at the speeds the engine was designed for and as a result did not use it for their original intent. Later, it ended up being used as a cruise-missile/drone-engine which then ended up on the MiG-25.

It was?? Well, I think I can shed some light on the subject. I know the formula to determine the flight characteristics(lift, max. speed., thrust horsepower) to try and prove one way or another that the F-15 can go Mach 3 at, say, 80,000 ft. I can add to this post later or modify it later. Running out of time. Sorry; will keep you posted.

At least that's what I was told. And considering the USAF did not want to be bested by the MiG-25 when the F-15 was being developed it seemed to be a likely possibility (Although claims that the MiG-25 was a total shock and was believed to be capable as an air-superiority fighter, all that stuff is bull. It was known very early on that the plane was designed as an interceptor with the primary mission of intercepting the A-12)

I don't know how easy it is to guesstimate the speed of the F-15. Keep in mind...
- The engine's exact thrust levels are not always honestly listed and are quite often listed below their true capabilities.
- The P&W F100, to my knowledge, compared to a J-79 was a pretty small compact engine meaning the inlet duct area is comparitively longer
- The exact contour of the inlet-ramps is classified, in fact it's probably even beyond that, also the ramps are pourous to skim off turbulent flow which improves engine performance. The flow skimmed off is then vented via a vent or two on the top of either engine inlet.
- The inlets consist of ramps and a hinged-lip which actually affect the aerodynamic-characteristics of the plane too
- The wing-body fairings probably play a role in supersonic performance (adding area, blending the wing and body, producing a shockwave ahead of the wing, maybe even producing minor compression-lift effects)

And if too accurate, both of us might get mysterious heart-attacks

He started at Boeing in Seattle after graduating from the Univ. of Cincinnati. (They STILL have an aerospace Bachelor's program after over 55 yrs. of instruction.)
Later he went to S. calif to be nearer to his father and worked at McDonnell Douglas. (No longer doing business.)

Impressive.


BTW: It was really hard to read that last post because the whole thing was in a quote although do-able.
Kendra

 

[Lee]

KJ,

Please keep in mind that various borrowed computers I'm using react to this software differently and will give different presentations as to what I write. I can continue writing quotes with "quotation marks" as you see here if it's easier.
As for the .html sources previously given above, there's a lot of disinformation out there and one should be highly educated so as to discern which a lie and which is truth.
Concerning the J-79 and F100? The J-79 had a 10% bigger intake face and about twice the thrust, which made it a formidable engine for its time. The F100 will have needed a higher pressure ratio (was likely so) in order to compete in terms of thrust/area in lbs./in^2.
Military engines are typically understated in performance. I distinctly remember the newest F-16 engine was reported in Aviation Week to have produced 47,500 lbs of thrust for a few seconds on the test stand.
Yes, that what I read. Also, I never forgot that the F-15 was clocked by radar during certification tests at Mach 1.6 at 66,000 ft. The minimum military requirement was the same speed at 60,000 ft. I think the F-16 can go faster than Mach 2.5 on a Winter day in the tropics, but bear in mind, the manufacturer advertises that L/D falls after about Mach 1.6-1.7, so they say about 75,000 ft is the ceiling.
I suppose the exact inlet geometry of the F-15---and certainly the SR-71---is still classified. I think it's possible for the air inlets to impart up or down thrust moments to a plane, so you could be right about the aerodynamics. The forward chines do play a part in the overall aerodynamics of a wings. That probably why they're so big on the F-18 E/F.
Mysterious heart attack? :-[ :-\ :'( ;D
Maybe the same thing that happened to Steve Fossett, the aeronautic explorer? I hope not!!!! Just kidding.

 

[KJ_Lesnick]

Please keep in mind that various borrowed computers I'm using react to this software differently and will give different presentations as to what I write. I can continue writing quotes with "quotation marks" as you see here if it's easier.

Okay that makes sense...

As for the .html sources previously given above, there's a lot of disinformation out there and one should be highly educated so as to discern which a lie and which is truth.
Concerning the J-79 and F100? The J-79 had a 10% bigger intake face and about twice the thrust, which made it a formidable engine for its time. The F100 will have needed a higher pressure ratio (was likely so) in order to compete in terms of thrust/area in lbs./in^2.

The J-79 produced twice the thrust of the F100? The F100's pressure ratio I figured was to get more thrust out of a smaller engine too in addition to just compensate for frontal area (and the effects of the fan-bypass)

Military engines are typically understated in performance. I distinctly remember the newest F-16 engine was reported in Aviation Week to have produced 47,500 lbs of thrust for a few seconds on the test stand.

Holy s**t! That's a lot of power! (Is this a derivative of the F110 turbofan?) Although I'm not sure if it could produce that thrust level for 5 to 30-minutes straight. Still very impressive.

Also, I never forgot that the F-15 was clocked by radar during certification tests at Mach 1.6 at 66,000 ft. The minimum military requirement was the same speed at 60,000 ft. I think the F-16 can go faster than Mach 2.5 on a Winter day in the tropics, but bear in mind, the manufacturer advertises that L/D falls after about Mach 1.6-1.7, so they say about 75,000 ft is the ceiling.

I don't know how true that statement about the L/D ratio fall-off would be. Those chines/strakes would produce a lot of supersonic lift even as the main-wings would suffer efficiency hits.

Additionally, the L/D ratio isn't the only factor in determining performance -- inlet efficiency and thrust-levels play a big role: The F-4 had a fairly thick wing with a camber (it wasn't swept back as much as a delta wing so the shock would go beyond the wing at high-speeds most likely, and it's leading edges were not the sharpest in the book) for example and it still managed some serious speed because it had a lot of thrust and variable-geometry inlets to help. The F-16's inlet may be fixed but I've been told it worked pretty nice even at high-speeds, and it has a lot of thrust at it's disposal.

You know, part of me wonders if the F-16 is capable of all the things the F-104 could do combined with superior low-speed handling (including super-maneuverability) thrust/weight ratio, bomb and weapons capacity and subsonic endurance.

I suppose the exact inlet geometry of the F-15---and certainly the SR-71---is still classified. I think it's possible for the air inlets to impart up or down thrust moments to a plane, so you could be right about the aerodynamics.

In regards to the F-15's inlet I was talking largely about the fact that the inlet has that hinged lip up top, and at low-speed it's angled down a bit and the air-flowing over the top of it would be have much like it was flowing over a droop.

The forward chines do play a part in the overall aerodynamics of a wings.

True! In a number of ways
-They can produce lift supersonically, and providing a trimming function (The Lockheed L-2000, and SR-71 definetly did use strakes/chines for such a purpose)
-They can produce powerful vortices which can shield the wing from a stall and allow high-alpha flight (With the F-16, F-18, MiG-29, and Su-27 allows for super-maneuverability)


Kendra

 

[Lee]

KJ, quoted: "The J-79 produced twice the thrust of the F100?"

Sorry, I was misunderstood. The J75 produced twice as much as the J79. The F100-PW-229 produces about 29,000 lbs of thrust and is more powerful and possibly lighter than the J75.





KJ: "The F100's pressure ratio I figured was to get more thrust out of a smaller engine too in addition to just compensate for frontal area (and the effects of the fan-bypass)..."

It does. Advanced materials, I think, are the key.

Military engines are typically understated in performance. I distinctly remember
Lee: "the newest F-16 engine was reported in Aviation Week to have produced 47,500 lbs of thrust for a few seconds on the test stand.

KJ: "Holy s**t! That's a lot of power! (Is this a derivative of the F110 turbofan?)

Derived from the F100, thusly: http://en.wikipedia.org/wiki/Pratt_&_Whitney_F100

I was referring to the F-16.





KJ: "Although I'm not sure if it could produce that thrust level for 5 to 30-minutes straight. Still very impressive.

No, not that long. RPMs were probably over 100% during the test. You're right, though, it's quite a bit of emergency thrust.





KJ: "You know, part of me wonders if the F-16 is capable of all the things the F-104 could do combined with superior low-speed handling (including super-maneuverability) thrust/weight ratio, bomb and weapons capacity and subsonic endurance."

All but the straightaway speed at 50,000-70,000 ft. The F-104 was designed as an interceptor. The F-16 is better than that as an attack platform, owing to its maneuverability.









Lee: "The forward chines do play a part in the overall aerodynamics of a wings."
KJ: "True! In a number of ways,"
-They can produce lift supersonically, and providing a trimming function (The Lockheed L-2000, and SR-71 definitely did use strakes/chines for such a purpose)"
-They can produce powerful vortices which can shield the wing from a stall and allow high-alpha flight (With the F-16, F-18, MiG-29, and Su-27 allows for super-maneuverability)"

Agreed to all that. Americans and others are experimenting with 'relaxed aerodynamic parameters' lately to improve survivability of aircraft.

 

[KJ_Lesnick]

KJ, quoted: "The J-79 produced twice the thrust of the F100?"

Sorry, I was misunderstood. The J75 produced twice as much as the J79. The F100-PW-229 produces about 29,000 lbs of thrust and is more powerful and possibly lighter than the J75.

You're talking about listed afterburner figures right? Either way, I would not be suprized if the F-100 was drastically lighter than the J-75 due to it's superior pressure-ratio and it's a more advanced design.

It does. Advanced materials, I think, are the key.

Air-cooling is also highly important in addition to advanced materials.

Derived from the F100, thusly: http://en.wikipedia.org/wiki/Pratt_&_Whitney_F100

I was referring to the F-16.

Wow, most of the F-16's used F-110's at least awhile back. I guess they went with an F-100 derivative. Still that's an amazing amount of power.

No, not that long. RPMs were probably over 100% during the test. You're right, though, it's quite a bit of emergency thrust.

Although I would still suspect they could get a lot of thrust out even with Military-Power! Although probably not as much as it did on the test stand.

All but the straightaway speed at 50,000-70,000 ft. The F-104 was designed as an interceptor. The F-16 is better than that as an attack platform, owing to its maneuverability.

Actually from what I remember the F-104 was designed as an air-superiority fighter hard as that is to believe, the Japanese did use them as interceptors however.

Even if the F-16 couldn't manage the straightaway speed, I would not be surprised if they could get pretty close.

Agreed to all that. Americans and others are experimenting with 'relaxed aerodynamic parameters' lately to improve survivability of aircraft.

Do you mean relaxed stability?

 

[Lee]

KJ, quoted: "You're talking about listed afterburner figures right?"

Right, at least the published figures.





KJ: "Either way, I would not be surprised if the F-100 was drastically lighter than the J-75 due to it's superior pressure-ratio and it's a more advanced design."

Exactly. It's a much newer engine.





KJ: "Air-cooling is also highly important in addition to advanced materials."

Sorry, that's right. Higher temps on the turbines mean higher thrust.





KJ: "...Still that's an amazing amount of power."

Aviation Week can give a researcher unusual information not easily available elsewhere. The Univ. of AZ, in my home town, has almost a full set of archived back issues for student and public research.









KJ: "Actually from what I remember the F-104 was designed as an air-superiority fighter hard as that is to believe, the Japanese did use them as interceptors however."

I'm confident the exceptional maximum speed at altitude had something to do with their using it that way.





KJ: "Even if the F-16 couldn't manage the straightaway speed, I would not be surprised if they could get pretty close."

I'm not sure. I do know the high wing loading of the F-104 allowed a whole lot of speed, but not a lot of maneuverability.





KJ: "Do you mean relaxed stability?"

That a better way of putting it, yes.

 

[KJ_Lesnick]

Right, at least the published figures.

Which probably are inaccurate in themselves. The J-79 is almost certainly more powerful. I remember something regarding the thrust to weight ratio of I think the F-104 or B-58 to suggest that they were a bit more powerful than listed.

Exactly. It's a much newer engine.

Plus turbofans generally have higher power-to-weight ratios.

Sorry, that's right. Higher temps on the turbines mean higher thrust.

Yup, and higher mach-numbers.

Aviation Week can give a researcher unusual information not easily available elsewhere. The Univ. of AZ, in my home town, has almost a full set of archived back issues for student and public research.

Really? I wouldn't think that a published magazine would be so reliable. But if it is, it is.

I'm confident the exceptional maximum speed at altitude had something to do with their using it that way.

Not to mention the fact that it can cruise supersonic (~M=2.0) without afterburner and has the same radius supersonic as subsonic. Good quality for an interceptor to have.

I'm not sure. I do know the high wing loading of the F-104 allowed a whole lot of speed, but not a lot of maneuverability.

It was kind of un-maneuverable at low-speed, though at high-speeds it wasn't so bad -- In the air superiority-role the U.S. intended to use it in, it's dogfighting style kind of reminds me of what I heard about the Me-262: Fast, and effective so long as it didn't try to out-turn the propeller-driven fighters (This was talking about the Me-262; with the F-104 it would be substituted with subsonic jet-fighters).

Basically it used it's speed with high indicated airspeed to yield high degree-per-second turn rates (even though the arc was fairly wide). The F-104 unlike the Me-262 though had a very good thrust/weight ratio and could climb very steeply, and avoid losing significant speed during turns. It also had a very good roll-rate (which was partially due to it having some anhedral). Generally the strategy involved using 'slashing' maneuvers. It was not the most stereotypical, orthodox dogfighter.

Interestingly, the F-16 even despite it's lighter wing-loading (and a tendency for such wings to not maneuver as nicely at high-speed without losing lots of speed), still probably maneuvers very well in terms of abrupt and even continuous maneuvers, even at high airspeeds, due to it's even superior thrust/weight ratio over the F-104, and it's aerodynamic-instability.

I don't know exactly how it's straight-line dash-performance compares to the F-104 exactly, but considering the F-16's inlets are said to be pretty-efficient and work particularly well at high-speed, as I said I have a feeling it would be pretty close.

That a better way of putting it, yes.

Gotcha

 

[Lee]

KJ: "Plus turbofans generally have higher power-to-weight ratios."

I wonder if the inverse cube ratio comes into play when an engine is scaled up to a great extent? SSTO's are prone to scaling effects. A modest increase in payload increases gross liftoff weight(GLOW) in a big hurry.




KJ: "Really? I wouldn't think that a published magazine would be so reliable. But if it is, it is."

They cater to professional engineers who know what's what. That's why I read the magazine at the library.




KJ: "Not to mention the fact that it can cruise supersonic (~M=2.0) without afterburner..."

The Foxbat could do the same thing. Mach 2 without A/B for quite some distance, particularly with the latest engines available.
(The Foxbat is maneuverable at 80,000 ft---more so than the Blackbird, since it was built strong enough to handle low level penetration missions. Mach 1.2+ at sea level, I think(?) Something like that.


KJ: "It also had a very good roll-rate (which was partially due to it having some anhedral). Generally the strategy involved using 'slashing' maneuvers.

The manufacturer was playing around with the idea of a larger wing for the F-104. Better maneuverability at all altitudes was the goal.




KJ: "I don't know exactly how it's straight-line dash-performance compares to the F-104 exactly, but considering the F-16's inlets are said to be pretty-efficient and work particularly well at high-speed, as I said I have a feeling it would be pretty close."

Published figures may or may not be useful. Intelligent, educated calculations may be necessary to arrive at a judgement.

 

[KJ_Lesnick]

I wonder if the inverse cube ratio comes into play when an engine is scaled up to a great extent? SSTO's are prone to scaling effects. A modest increase in payload increases gross liftoff weight(GLOW) in a big hurry.

I don't know actually. But it would seem that turbofans have a higher thrust to weight ratio than turbofans.

They cater to professional engineers who know what's what. That's why I read the magazine at the library.

Maybe I should read it when I can find it.

The Foxbat could do the same thing. Mach 2 without A/B for quite some distance, particularly with the latest engines available.
(The Foxbat is maneuverable at 80,000 ft---more so than the Blackbird, since it was built strong enough to handle low level penetration missions. Mach 1.2+ at sea level, I think(?) Something like that.

It could do around 5 G's at that speed/altitude from what I remember. From what I remember it could do somewhere in the ballpark Mach 2.35 to 2.50 without afterburner, (i've heard figures of 2.35, 2.40, and 2.50) which is pretty impressive.

Regarding the engines the Foxbat used, some of the more advanced versions of the R-15 were to the best of my knowledge not used on production planes. Could be wrong though. There was at least one model that might have been used (could be wrong here too) -- The R-15BV-300

The manufacturer was playing around with the idea of a larger wing for the F-104. Better maneuverability at all altitudes was the goal.

Yeah, but wouldn't you generally need more engine power to avoid excessive speed-losses during hard turns at the higher speeds for that to work, no?

Published figures may or may not be useful. Intelligent, educated calculations may be necessary to arrive at a judgement.

That is of course the case in any circumstance

 

[overscan (PaulMM)]

Topic is locked. There is too much speculation and not enough hard facts in this discussion. This is a conversation better suited to ATS forum, email or msn messenger than this forum.