j58

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SR-71...

Reply to
Rufus

wow, a old boston friend worked on it. that's basically an engine that uses a jet to fire the main motor? kind of a ram jet?

Reply to
e

wow, a old boston friend worked on it. that's basically an engine that uses a jet to fire the main motor? kind of a ram jet?

The J58 was a turbojet engine (ass opposed to turbofan engine used in most modern fighters). However, it was equipped with ducts that bypassed the compressor at high speed operation, directing the aurflow to the combustion chamber and acting in a ramjet mode.

Remove "spamkill" from my e-mail address to reply.

Reply to
JRSJLS

so it was fiendishly simple in concept. and i bet hard to get right. most hand built?

Reply to
e

I wouldn't think so...I bet it borrowed heavily from the J-79, as far as the turbojet concept went. Sizing the duct/bypass for the design mach (and then actually getting there...) would be the tricky bit.

Reply to
Rufus

i'll ask my friend. he did work at the lynne plant. very cool place, i bet you've been there.

Reply to
e

I wouldn't think so...I bet it borrowed heavily from the J-79, as far as the turbojet concept went. Sizing the duct/bypass for the design mach (and then actually getting there...) would be the tricky bit.

Reply to
JRSJLS

"JRSJLS" wrote

How about the fact that the nomenclature system assigns numbers sequentially, and 58 comes before 79?

KL

Reply to
Kurt Laughlin

Naw...I was stuck in Evil...er...I mean Evendale...at the large engine plant.

Speaking of LARGE engines, the GE-4 is HUGE. It was the GE candidate for the SST. Basically a scaled up J-79...six-foot plus diameter, afterburning turbojet.

Reply to
Rufus

Uh...no. The numbers mean nothing - especially given that they were produced by two different manufacturers.

But I wouldn't doubt that the two (GE and P&W) may have had to compete for the contract. Being a USAF platform, the winner would have been sort of "obvious".

Reply to
Rufus

Even though I wasn't around at the time these two engines were originally developed, I can state with confidence that the J58 did not borrow from the J79. For starters, they were developed by different companies: the J58 was developed by Pratt & Whitney; the J79 by General Electric. The J79 was a conventional turbojet, developed for fighter/interceptor aircraft that only "occasionally" flew at supersonic speed. The J58 was designed for sustained operation at high migh mach number (and at at much higher altitude than a fighter attained) - hence the bypass system. This was just one of many differences brought on by the harsh environment of sustained supersonic operation. For example, the hydraulic fluids, lubricants, and fuel (both for the aircraft and the engine) had to be tailored for the mission. The design challenges for both were difficult, but were based on significantly different requirements and therefore led to different solutions.

Which drove Rufus to reply:

Having done some design work for GE I can attest that all designers (and just plain smart buisnessmen) watch thier competition. The J-79 as I understand it was the first truly successful afterburning turbojet produced in numbers in the USA - many engines after it utillized some if not most of it's features (most if not all of which incidently can be traced back to the JUMO-004). Given that the design was also produced under contract for the Gov, I would also wager that the Gov reserved the right to hand any aspect of the design to a second source at any time - I personally wittessed this happen with the F-404 while at GE. So, cross pollination within the industry...happens.

Not saying that what you point out about the fuel and engine having to be taylored is wrong, but you need to remember that the tech at the time to sustain combustion above mach 1.0 was a serious (if not out of reach) stretch - even today, it's not really "easy". Not to mention that designing a turbine engine for operation at a supersonic inlet speed would also have been a TOTAL stretch...and still is today. It's just the physics of it.

Therefore, I would submit that there really isn't much that is extrordinary about the design of the J-58 other than that it is an afterburning turbojet, encased within in a ramjet which augments and replaces turbine produced thrust above design mach. In fact, you can calulate the design mach for the inlet based on the half angle of the inlet cone, but I'd guarantee you that the inlet mach to the turbine is maintained at less than or equal to 1.0 over the entire envelope - given the tech of the time.

If you do much reading about the SR-71, you'll run across stories of inlet unstart problems...and how the inlets actually produce some thrust. All the turbine is there for is to get the sled up to design speed for the ram to take over - then I'd bet you could theoretically shut it down and cruise on ram alone...given that you design the flowpath of the ramjet to account for the solidity of the freewheeling turbine, and/or used the afterburner at the combustor for the ramjet.

...but I'm just guessing based on what I've read, and what I've designed. Don't know any sled-drivers...or I'd ask them.

Reply to
Rufus

"Rufus" wrote

That's incorrect. The numbers mean everything. Designators for military aircraft (and tank) engines have been assigned by the Government since before World War II. Don't you find it curious that both GE and P&W both "just happened" to decide upon "Jxx" to designate their engine models? The fact is the J58 was the P&W JT11D while the J79 was the GE X-24A.

Check out:

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KL

Reply to
Kurt Laughlin

you didn't love lynne, city of sin with the ptomaine parlor and f*ck motel right at the bridge? one of the winter hill boys was found in his caddy about 22 feet down under the bridge. damndest "accident".

Reply to
e

I'll buy the "J" part, but I'd still associate the number with a contract - keep in mind that the contracts were being let fast and furious in those days, and that manufacturers were plenty. Also - note the missing numbers in the "sequence".

Just based on the few engine designs I've been associated with and done design work on for GE...they were ALL prefixed "GE", and sequenced by design study; sometimes within a contract, sometimes just by where they fell on the calendar if they were in-house R&D. Or the NASA sponsered "E-cubed" project - Energy Efficient Engine. I hear this study eventually led to the engines for the 777...

Usually the numerical sequence at GE derived from a family of designs scaled from a core engine design - the F101, F110 (formerly the F101DFE

- Derivitive Fighter Engine - as originally proposed by GE), and the CFM-56 all share the same core, for example. Looking at the progression of the manufacturer's numbers in the table for the link you provided makes me think they do/did the same thing at Pratt.

That's the way I know it was true as of the early 80's. I think the system you reference has since gone by the wayside - though the manufactuerers codes still seem to hold - F404-GE-xxx and F414-GE-xxx, for instance in the case of the F/A-18; F101-GE-xxx for the B1, and F110-GE-xxx (or Pratt's F100-PW-129) for the F-15, F-16, and F-14 (GE only). That's the way they show up in the pubs today...that's how it is with aircraft, anyway - tankers may do something different.

BTW - CFM stands for "Commercial Fan Motor", if I remember right; it's interesting your reference lists GE's "TF39" (the full designation of which is TF39-GE-1C) for the C5 as the "CTF39" - I know that GE sued the gov and won for the right to incorporate C5 engine tech into their CF6 series engins for commercial use/sale...which set some landmark legal precident for industry...an opened up whole families of engines based on cores developed for the military. Once such is in the commercial domain, it's a short step to the "cross pollination" of design philosophies between companies that I mentioned previously.

Reply to
Rufus

Ah yes, the Winter Hill Gang......I used to love execution bridge in Medford, two blocks east of the police station and it would take 20-30 minutes for the sirens to start once the automatic weapons stopped firing......

Reply to
Ron

I never got to work in Lynne; had a bud that transfered there to get closer to his gal, though. In Evendale we had the Darling Co. - an animal waste rendering plant - just across our eastern fence line.

When the wind was blowing just right (which was most of the time...), it smelled like they were burning dirty rubber women's underwear...by the ton. One of the reasons I left.

Reply to
Rufus

Oh you'd love it at NRL in DC then, literal asshole of the city because the only thing below it are the shitponds for Blue Plains sewage treatment plant.......and there is no such thing as the wind blowing just right there, the smells pervades almost everything, especially on Mondays!

Reply to
Ron

...no sweat. I spent 18 of the longest months of my life working at NAS Pax River. BEFORE the NAVAIR invasion...

Reply to
Rufus

or mefford as the natives say. whenever i meet a somervillan, the may they say smmaville tells whether they are from winter hill or the high school. cappy's in everett is another great "croosroads" for automatic weapons fire. shoot around the rotary.

Reply to
e

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