Hi Brian,
The only way I see to get a copy of this is through the CIA. It is declassified and is listed as an article on their web site. If you are interested, I could go through the process to attempt to get a copy and see what it says.

Hello Lyman,
I agree with your reasoning.

The increase in engine thrust at the afterburner nozzle (gross) is, I believe although not quoted, of the same order as the airflow increase. I guess the a/b temperature did not change significantly, otherwise the jet velocity contribution to the engine thrust would have had a more noticeable effect on the engine thrust.

Thanks for the stimulation.

Can't you old-timers just talk about golf and Ensure?

Disregard previous post (tongue-in-cheek or not) - this stuff's fascinating!

Ike - if you haven't worked it out yet, the so-called "old-timers" always have the best stories.

They certainly think so.

Actually, most of the contributors to this thread tend to be the most self-effacing on PPRuNe. And in this case, they really do have the best stories.

I :mad: you not - if you ignore this thread, you're missing out.

@Dozy
You seemed to be estonished when I wrote some months ago that the first AF447 threads were the best : Old-timers were the first who were able to analyse the few informations we had before the black boxes were found.
I am glad to read your last post

TNX, Rouli, we dinosaurs needed that!

I joined the old farts after the AF447 accident because I have always been interested in an accident involving a FBW aircraft. Being in the "charter members" of the first operational aircraft with full FBW, I felt I could both learn and contribute. I have my engineer diploma and then a lot of hours in real planes, and remember there's no such thing as a "dumb fighter pilot".

We may have to search the archives, but I suggested early on once the wreckage pattern was shown that it seemed the thing hit in a classic "deep stall". Turned out it wasn't quite that simple, but humans and not the aero characteristics of the jet caused the crash.

I continue to value the contributions and experience of the old farts when they post on these forums.

multi-cycle motor
 

While we were examining Dr. Abernathy's neat way to keep the motor going above 3.0 M, GE was testing their new motor that implements some of the same concepts and reflects my view of the annular bypass.

"Superjet" variable cycle jet engine could power future fighter aircraft

Worth a look to see motor concepts of the next century compared with what the good Doctor did 50 years ago!

My own view is not to have an extra "fan" disk but use the outside duct as a true "ram jet" and same sorta inlet configuration the Blackbird had. CAUTION!! Don't get all excited, Lyman.

roulishollandais

I'd say about half the input turned out to be right in the early threads. The discussion started to go somewhere after the recovery of the flight recorders. I don't think the age of the contributors was as big a deal as it is in this thread though... :)

Yes Doze, it's a sobering thought that the most rookie pilot or engineer ever involved in supersonic civil transport must be at least in his/her fifties. And roughly the same applies to Mach 3+ in the military?

I hope he won't mind me saying this, but given that Clive - no rookie at the time - comes across as eternally engaged and excited by the subject (not to mention sprightly in general) and is clearly keeping abreast of things, it would appear that working on projects of that ilk can confer a certain extended "youthful" outlook. Long may it continue! :)

The M3+ military projects were effectively rendered obsolete much faster by the advent of the space programme. I'm sure that the engineers to come that are worth their salt will be smart enough to engage with their predecessors and their work. I barely understood half of the stuff in this thread and I'm still hooked!

Last SR-71 pilot I had dinner with was my age at the time - 40 years old when he lost an engine and landed at my base.. A student of mine 5 years younger flew the beast over Libya in 1986 ( El Dorado Canyon, I believe - Brian Shul), so would have been in late 30's.

Only the shuttle guys were lots older than the early days of NASA. My roomie flew first hop back in '87 or '88, and would have been in his late forties, but had been selected about 8 years earlier. He then flew on the MIR about 8 years after that, so figure it out.

Make no mistake, experience counts. However, that experience must involve a few instances of abnormal systems or situations. Our profession exposed us to many while we were very young, and they turned the keys over to us when we were 22 or 23 years old. Think about a troop in his late 20's flying a Raptor or Lightning that costs about as much as many airliners.

Wasn't that because they erred heavily on the side of caution regarding the effects of zero-G on health and fitness? I'm assuming that because Skylab gave them hard data to work with it became less of an issue by the time of STS-1.

Actually, Doze, the problem had to do with the snail's pace of the shuttle program and not physical condition.

Cooper in Mercury was 36 and White was 35 in the Gemini spacewalk. I knew White, as his brother was a classmate in my squad at USAFA and was the one that convinced me I could make it if I tried.

The Mercury, Gemini and Apollo guys moved ahead very quickly. From selection to first flight was three or four years at most. Shuttle was 7, 8 9 years.

My roomie was selected at age 40 and flew 9 years later! Of course, he had to stand down for two years due to the Challenger disaster.

but I digress......

gums
Fascinating stuff, but when one reads the article it becomes clear that the engine is for military use. Cutting down the airflow to increase thrust at take-off is the last thing you want to do if your problem is airfield noise!

Dozy

Knock it off Joe, it is becoming embarrassing - besides, the spirit is willing but the flesh is weak :ouch:

Well here's the Hollywood pitch:

PpruNe pensioners crowd-source a replica SR-71 from souvenir paper-weight components, a junk airframe and lashings of old-timer Skunk Works / Concorde physics. Having learned that a craven State Department is delaying vital surveillance of a rogue state nuclear programme, Gums battles his demons to eventually dust off his G-Suit for One Last Mission, sanctioned only by PPruNe, and to finally fly this historic marvel. Suspense builds, because the audience know that PpruNe thread-lurkers from Iran have just completed a YF-12 based on the same data.

Gums gets the crucial recon. pictures but, unarmed of course, finds the YF-12 on his tail. Just when all seems lost he gambles on the expertise of his PpruNe pals, and pulls a manoeuvre just beyond the stated structural limits of the airframe. The YF-12 has to pull the same manoeuvre to achieve missile-lock, and comes apart. Credits roll over a PpruNe guard of honour at the culmination of Gum's Presidential ticker tape parade.

In flashback, the young CliveL will be played by Simon Pegg, based on his performance as Scotty in the Star Trek reboot...

Good grief, Robs!

@ Clive: Yeah, and the ADVENT uses the extra air for a higher bypass ratio and not to help the burner. Seems to make it more like the TF-41, which gave the Sluf super range/loiter time compared to the Double Ugly, Thud, Hun, et al.

OK, no more after that, I promise (as agreed). But, just this once and with all due respect - take the bleedin' compliment!

gums

One thing I do know is that during the Apollo era, the late, great Alan Shepard was at the top extreme of what NASA would allow when he commanded Apollo 14 at 47 years of age. Because the surviving Mercury 7 tended to retire during the Apollo era in their early 40s I'd wager that he was actually probably over what they originally intended, but Deke Slayton didn't have the heart to deny him after fighting his way back to flight status following experimental surgery for Ménière's disease - which had until then left him grounded.

Hi gums,

Thanks for the ADVENT video, it is indeed rather interesting. IMO, It is the wave of the future for military combat aircraft engines.

GE Aviation completed testing its engine core for the ADaptive Versatile ENgine Technology (ADVENT) program with the U.S. Air Force Research Laboratory on Feb. 6, achieving the highest combination of compressor and turbine temperatures ever recorded in aviation history.

The accomplishment is a result of GE's most advanced core propulsion technologies including lightweight, heat-resistant ceramic matrix composite (CMC) materials. These core technologies, along with an adaptive low pressure spool, result in a 25 percent improvement in fuel efficiency, a 30 percent increase in operating range and a five-to-10 percent improvement in thrust compared to today's fixed-cycle engines.

I do want to point out this technology is not new and has been in the works for a long time. Following initial studies by Gerhard Neumann in the 1960s, GE's YJ101 was the first full engine to demonstrate variable cycle capabilities in 1976 (see report below). The YJ101 was the forerunner of the F404 engine for the Navy's F-18 fighter.

Access forbidden!

The next engine to use the variable technology was the GE YF120 engine under a demonstration contract for the Advanced Tactical Fighter (ATF). An engine is on display at the USAF Museum and was one of two YF120 engines installed on the YF-23, Northrop-McDonnell Douglas' entry to what is the F-22 Raptor fighter. The contest was lost to Lockheed YF-22 and P&W's F119 engine.

The technology then carried over to the Joint Strike Fighter (JSF)(F-35) program where a collaboration between GE Aircraft Engines, Allison Advanced Development Company, and Rolls-Royce. Allison provided components and some technology for the engine core and low pressure turbine; Rolls-Royce designed and manufactured the fan module, but the overall design was based on the variable cycle YF-120 engine. Again though, P&W was awarded the engine contract using the F119 engine.

I've been lurking on this forum for awhile and found it an interesting pastime. As I came across this discussion on the SR's thrust, I figured I'd add my 2 cents. I flew the Blackbird from '86 to the close of the program in '90. The thrust generated to attain Mach 3+ came from the combination of inlet, turbine, and AB/nozzle section. Rich Graham's 3rd book ( 4th available in May) is your best source on specifics from a pilots point of view. As an example, when things started to go wrong thrust wise, the first item checked was the inlet (spike, forward doors, aft bypass), then the AB/nozzle, then the turbine. More than 50% of thrust was produced by the inlet, +/-30% by the AB nozzle, the rest via the J-58. Our last SR lost (21 Apr '89) was via a turbine blade failure with the loss of #2 and B hydro and the slow loss of #1 and A hydro due to blades cutting those lines. The initial indication was only a fluxing yaw moment at level off at speed and altitude. There were 65 bold face procedures for this aircraft. I now have 3 on the 757/767. How times have changed.

At last, someone who knows what he's talking about. Welcome 749, I'm guessing you're now taking on the task of answering a deluge of questions. No question from your tag as to where your heart lies. Looking forward to whatever contribution you deign to make. Magical aircraft.

I second all of Brian's remarks.

I wish to say thank you to Lyman for forcing me to contemplate where I stood in this discussion, and erred I might add. Off line discussion with other contributors are also to be thanked – they know who they are.

How I view it at the moment.

Briefly, the engine, taken in isolation as per Abernethys Patent, is a pure turbojet with afterburner. Just about every axial turbine requires compressor bleed to control stall or surge, and are normally closed when at operating RPM. The J-58 requires compressor bleed to unchoke the compressor when operating above 1.8 to 2.0 Mach. Up to that point it’s your regular pure turbojet with afterburner. It is not a bypass engine in the general understanding of the term.

Even though Abernethy himself says, “Bypass the bleed air around the compressor at high Mach number into the afterburner and it would solve the surge problem, provide cool air to afterburner and increase the mass flow and thrust significantly. Actually it converted the engine into a partial ramjet with capability above Mach 3”, the J-58 taken in isolation, as on the test bed, does not have a ramjet mode, partial or otherwise. Abernethys use of the “ramjet” word I take as being recognition of the type of inlet that would be necessary to make his Patent a viable high supersonic powerplant. When combined with that inlet it does give the J-58 a “partial ramjet” feature.

A ramjet requires the inlet to “start” in order to become operational. The SR-71 inlet “starts” between 1.6 and 1.8 Mach, so once the bleed opens at 1.8 to 2.0 Mach, the J-58 can be said quite correctly to have a “partial ramjet” feature.

Sorry Lyman that we were at cross purposes re the patent. I was viewing the installation in its entirety (inlet, J-58, afterburner, nozzle) rather than the J-58 as a stand alone item. The J-58 was after all, purpose designed for one particular aircraft. If that can be taken as an excuse. :)

This may or may not help the discussion. Speaking from the operators point of view. In an earlier posted graph you will note a line depicting the supersonic shock wave from the tip of the spike meeting the lip of the intake as speed increases and the spike retracts. Looking three dimensionally, it is a conical shockwave forcing all the air molecules into the inlet. We are flying in around 4 mm of mercury. 70% of this supersonic air is routed around the J-58 via 6 ducts, compressed and dumped into the AB section where fuel is added then ignited. This produces 54% of the thrust. The remaining 30% of this supersonic air passes through a, internal to the inlet, shock wave and comes out subsonic. Here's where the pilots work load really starts. We refer to the bypasses as the "forward doors" and the "aft bypass". The forward doors allow air to exit external to the engine nacelle. The aft bypass take excess air off the turbine face and routes it around the J-58, internal to the nacelle, and dump it in to the AB section. The objective is to feed the J-58 14 psi of air pressure while at speed and altitude. The J-58 thinks it is at sea level on a hot day. 427*c CIT max limit. Interestingly, the J-58 is rated at max rpm - continuos, max AB - continuos. If one over pressures the turbine, you get an "unstart" of that inlet. That is to say the spike is automatically/manually driven full forward, you lose 54% of your thrust on that side and the "fun" begins as she, SR-71, hits you up the side of the head. Followed quickly by a slap to the other side of your head as the opposite side sympathetically follows suit. The worst "unstarts" are at max Q of 2.6 mach in the climb while accelerating. Obviously, bleeding air external to the nacelle creates drag and depending on OAT you want them closed. The aft bypass allows a manual selection of varying amounts of air bypassed to close the forward doors. With extremely cold temps we may,believe it or not, actually want to bleed air externally to keep the mach within desired flight planed speeds. Just to make it more interesting, the left/right inlets have no common settings. At speed this 1950s technology produced 500,000 lbs of thrust.

Thank you 749Connie! Absolutely fascinating. I've read Col. Graham's books and they're excellent.

A couple of dimensions to add to the data bank, Clive/ Brian.

I was at Duxford a while ago and there are 2 J-58s under the Blackbird.
Someone thoughtfully displayed them with one nozzle fully closed and the other fully open.
Closed dia 33", open 45".
Who knows what they really are with the cooling layer. Maybe an inch less.
Or how they grow when hot.

Do let me know if you find the numbers useful at all. I suspect not as effective nozzle areas have to be calculated from other stuff.

Thanks Peter. I'll plug it into the sums and see what difference it makes.

Since raising this question (ie what did David Campbell mean...) over a year ago (post #1) I can now tie up my loose ends. I have concluded his statements are most insightful. I hope I've interpreted them correctly.

It revolves around an afterburning turbojet reaching the flight speed at which the engine becomes a "drag item" (compressor still at 100% mechanical RPM but fuel flow now limited by "new-high" (J58 1300 F) comp delivery temperature and existing "redline" turbine entry temp (J58 2000 F). The afterburner is still getting 100% flow together with its temperature rise of about 1700 degF (P.Law's presentation Fig. 9).

So, ref D. Campbell "engine is inducing flow and heating it up with maximum afterburner".
He was not referring to the secondary flow as I originally thought but the main engine flow.
Engine is pumping (but not much else, in terms of thrust production that is, except the very necessary cooling flow for the afterburner, at 1050 F instead of at EGT 1450) at 100% speed, ie flow part of thrust. Afterburner is enabling airframe secondary nozzle to provide the velocity part.

ref D. Campbell "If the AB is reduced to minimum AB, the engine would actually be dragging on the engine mounts at high Mach numbers."
The engine is already a "drag item" at this speed because even with min AB the force on the mounts (ie complete engine incl AB) is still a drag.
Perhaps the engine "drag" is intimated by the engine pressure ratio being less than one? (see P.Law's Fig. 17 epr 0.9 at cruise). High Mach number still obtainable since thrust still from 100% flow and airframe secondary nozzle still has high pressure ratio.

ref D. Campbell "Further reduction of engine thrust below military power will result on no propulsive thrust on the aircraft".
The engine has been throttled back so reduced flow means high intake losses from off design, amongst many other things. No net thrust.

Comments welcome. Always trying to learn.

Peter

We studied the SR-71 installation back in my college days (~40 years ago). As noted, most of the 'thrust' comes from the inlet and exhaust, not the engine itself (at least at cruise Mach).

On the SR-71, the engine is there mainly to initiate the airflow through the ducts and to get the airplane up to speed. At ~Mach 3, ram jets are quite efficient, the problem being getting the aircraft going ~ Mach 2 so that the ram jet will actually work.

At cruise Mach numbers, the engine itself is of minimal benefit, except to provide hydraulics and electrical power. If not for the need for electrical and hydraulic power, and the weight of the associated hardware, it would probably be better for net thrust fuel efficiency to simply close off the inlet to the J58, let all the airflow go around, and make it a pure ramjet.
Of course, there would also be the concern of getting at least one of the jet engines running again at the end cruise (not trivial, after a prolonged high altitude cold soak :uhoh:) for landing....:sad:

No cold soaking in the cruise on this baby, quite the reverse.

tdracer

Thank you for your comments.

Russian turboramjet experiments of the same era using a MIG-21 engine kept the engine windmilling after transition to a ramjet. They identified the bearing temperatures as being the main problem (needing oil cooling above M3.2 even though there was no friction heat from high RPM and axial loads).
Didn't see the sfc trade offs though.
https://www.cso.nato.int/Pubs/rdp.asp?RDP=AGARD-LS-194

Hello Brian,

I have gone through old posts to see what I missed.......

The engine didn't need any ram to run in its cruise operating mode, just the right inlet temperature and pressure. It did it on the ground. Nobody would have signed it off as flightworthy if it hadn't.

Whatever the operating mode of the engine as part of the complete propulsion system at cruise it would also have had to have been run in the same modes in isolation on the ground to qualify it for flight since it was the primary thrust producer for the aircraft (not test engine on an FTB).

Since it ran at cruise design-point inlet conditions on the ground it would have operated in the same modes as in flight. See use of J57/J79 exhaust, etc to condition inlet air SR-71 J-58 Powerplant

I presume it would have had to run a 50 hour endurance test (called a PFRT) to qualify it for flight throughout the envelope including some hours of continuous running at the cruise design point plus some margins.
The engine would have been stripped and inspected before every detail in that particular design build got the OK to fly.

The value of the cruise part of the PFRT is that the engine is running in cruise mode (and will show up problems) but it happens to be on the ground with no ram from a Mach 3 intake.

Fully agree Peter. :ok:

Since starting this topic, which generated a lot of discussion on the relevance of ramjet terms in describing the engine, I've done a lot of digging so why keep it to myself when a few of you showed interest in applying various partial/turbo/ramjet appellations. The question I set myself was "Is there anything unique about the J58 installation which warrants any ramjet term?"

Brian in an early post identified the Lockheed-originated "It's a ramjet" from KJ. KJ didn't give an explanation though. I now know that he wasn't interested in the workings of the engine, not surprising with the weight he carried on his shoulders. I have just bought his book "Kelly, More Than My Share of It All". Quote "..bypassing the high compressor..and flying as a ramjet....with no machinery obstructing the flow...". I think it's worth pointing out this red herring because it could well be the mother that spawned the most common 'understanding' out there.
(P&W documentation tells us 80% of what went into the afterburner was turbine exhaust. About 13% was cooling air from the compressor and 7% was compressor air for burning)

As a baseline for judging uniqueness I used the only other flight-tested afterburning turbojet installation we know about which was designed for Mach 3, the J93 in the Valkerie.
What happened to the air going through the intakes and ejector nozzles was much the same. In both compressors the air hit all the blades at the right angles, despite running at design 100% mechanical RPM and very high inlet temperature. The afterburners were a bit different though as the J58 was the forerunner of high boosts seen in future fan engines, with cooling air cooler than EGT and reduced EGT at entry.

Is this significant? Well we know the machinery was a drag item at cruise, ref D.Campbell's "F-12 Series Aircraft Propulsion System Performance and Development". And just noticed another reference to this in "SR-71 Revealed" quote "at cruise the rotor of the engine actually had a small negative thrust load on the engine" (I wont quote the sentence before that :E). So it seems that the J58 had just gone over the edge of conventional operation with the afterburner now assuming a greater relative importance than ever before, even making up for a thrust shortfall from the machinery. This could well be what makes it unique. The Valkerie wasn't there yet with its still-positive epr (stick my neck out with fig3 pumping characteristics Emission Measurements of a J93 Turbojet Engine )

So, is the COMBINED thrust upon exceeding mach 2-x ... 400,000 - 500,000 ...?
Per 749CONNIE remark (unchallenged) above..? It'd seem more plausible

...(based on all the "common sense" I LACK regarding the behavior of 150,000 pound vehicles going fast enough to have 45,000 lbs of friction (in the mach 2.6+ range) making the inertial frame of reference about 195,000 pounds ... which needs to still accelerate another 250mph to reach mach 3.0 (cruising speed) as they accelerated to mach 3.2 (quite easily apparently) as the default reaction to missile launch-alerts .... WITHOUT any other changes to their trajectory).

This couldn't POSSIBLY have been done on less thrust than an F-22s max ... and weighing 2.5x as much, CAN IT!?

Literally TRANSCRIPTS of an SR-71 Pilot from the video
Blackbird: The Fastest Spy Plane (Extended Cut) - SR-71@ 12:53. www youtube com /watch?v=mHjhgeyhuKk(Replace spaces with . between www + com)

TO READ ONLY TRANSCRIPTS, ARE ALL INDENTED, BELOW

Video TRANSCRIPT & EXACT TIMES of statements (FORMER SR-71 PILOT) written VERBATIM, below:
To include a phrase analogous to "J58s PULLED him through the air more than the turbines pushed!".
Did he just know how to fly it and not understand the engine's physics for thrust..?
The video / talk is good irrespective this one snippet. Skeptical of my claim? exact times & verbatic text below.


All from:
Blackbird: The Fastest Spy Plane (Extended Cut) - SR-71

Hi TrumanHW,

I should think all Blackbird pilots were exceptionally well qualified and understood the engine's physics better than yourself.

If you read all the previous posts including Post #8, Brian Abraham explains that "During high-speed flight in the Blackbird, compression of air in the inlets generated most of the vehicle’s thrust. At Mach 2.2 the inlet produced 13 percent of the overall thrust with the engine and exhaust ejector accounting for 73 and 14 percent, respectively. At Mach 3 cruising speeds the inlet provided 54 percent of the thrust and the exhaust ejector 29 percent. At this point the turbojet continued to operate but provided only 17 percent of the total motive force."

Later he explains that this was only possible because the J58 "vacuum cleaned" the high pressure from the back of the inlet. The "thrust" they refer to is that which is transferred into the airframe by various parts of the inlet, engine and exhaust ejector.

See also M2Dude's explanation of Concorde's power plant.
"The engine itself now only generates 8% of the total thrust, a mere shadow of its subsonic glory. The now divergent secondary nozzle produces a sizeable 29%, this being produced in a similar way to how the intake subsonic diffuser produces its thrust. (The main difference in the case of the secondary nozzle is that instead of a subsonic decelerating flow, we now have a supersonic accelerating flow). A huge 75% OF THE TOTAL THRUST is produced by the intake subsonic diffuser section, this being due to the huge rise in static pressure that is occurring in this section. The 'negative thrust' from the forward ramp section this time is 12%, produced by the supersonic compression forces acting on the divergent section of the intake, resulting in an intake thrust component of 63%. So it can be seen that the vast majority of the Mach 2 thrust forces are transmitted to the airframe not via the engine mountings, but via the mountings of the intake, and to a lesser extent the TRA nozzle. It might seem that the two cases, and in particular the latter one, are very demeaning to the role of the engine, but nothing could be further from the truth. By the laws of conservation of energy, thrust (or any other force for that matter) cannot be created out of thin air, the whole process is about maximising the powerplant thrust that is potentially 'on tap'. (O.K. I know, this entire subject is about providing thrust from thin air!!). Without the engine, the entire process of course falls apart and all components of the powerplant produce exactly the same amount of thrust - ZERO! It is also doubtful if any engine currently in existence could do the supersonic job anywhere near as effectively as the OLYMPUS 593. (Not bad for a design that can be traced back over fifty-four years!). The 593 produces the necessary gas flows to produce these stated levels of thrust, and in the final analysis all powerplant thrust of course is really generated by the engine, what we have been looking at how this thrust is transmitted to the airframe."

To put the record straight Connie should have said "horsepower" rather than "thrust". The oft quoted comparison is in cruise each J-58 engines was producing more horse power than the RMS Queen Mary (160,000 SHP).