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SR71 Engine

09/20/2015 2:43 PM

ever wonder why the engines have a cone at their inlet? I did

https://www.youtube.com/watch?v=F3ao5SCedIk

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#1

Re: SR71 engine

09/20/2015 4:13 PM

Nothing about this spacecraft is ordinary.

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#2

Re: SR71 engine

09/20/2015 4:27 PM

To spear the geese before they enter the engines.

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#3
In reply to #2

Re: SR71 engine

09/20/2015 4:36 PM

every plane needs a cow catcher after 7000 feet

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#4
In reply to #3

Re: SR71 engine

09/20/2015 5:41 PM
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#5

Re: SR71 Engine

09/20/2015 6:50 PM

I could give a short, and inadequate, serious answer to this question but for a better and more complete answer including the design and operation of this SR-41 (Blackbird) Pratt and Whitney Engine go watch the below 5 minute U-Tube video I discovered. Trust me, it will be worth your time

https://www.youtube.com/watch?v=F3ao5SCedIk

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#6
In reply to #5

Re: SR71 Engine

09/20/2015 7:04 PM

Not exactly sure what you are talking about.

Fredski's opening post has the same web link to information about the SR-71 engine.

What's a SR-41?

And his link is live.

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#7
In reply to #5

Re: SR71 Engine

09/20/2015 7:12 PM

clearly nothing gets past you

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#8

Re: SR71 Engine

09/20/2015 8:12 PM

I simply scanned the picture and his comment, totally overlooked the link and went on to review the responses; which, to be honest, seemed to be so off subject that I didn't think any real information had been given on the engine. I will be more diligent next time.

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#9
In reply to #8

Re: SR71 Engine

09/20/2015 8:23 PM

its all good

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#10
In reply to #8

Re: SR71 Engine

09/20/2015 8:26 PM

It's no big thing.

We're a tough audience here and give no quarter.

Hang around and join the fun.

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#11
In reply to #8

Re: SR71 Engine

09/20/2015 8:36 PM

Wait.....there was a picture?

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#12

Re: SR71 Engine

09/21/2015 4:34 AM

I could tell you more about the the J58 but then I'd have to kill you!!!

The technology Kelly Johnson came up with in the early '60s was amazing for his time. And he also used the old tried and true technology- anything "Tarred and Feathered " can and will run really fast !!

Never had the opportunity to crew a SR 71, but a fellow Inspector did and had storied to tell, one that stuck out was when the Black Bird was setting in the hanger the fuel would leak like a sieve out of the wings and was some really nasty $hit to deal with. But still a pretty cool bird!!

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#13

Re: SR71 Engine

09/21/2015 6:11 AM

Designed with slide rules, same as when we went to the moon. Makes ya think!

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#17
In reply to #13

Re: SR71 Engine

09/21/2015 10:09 AM

I spent a good of part of my early engineering career using a slide rule (yes, I admit it, some will say I am "old"; but, I prefer to say "experienced").

In fact, I still have my trusty Post Versalog with its last performance upgrade, a magnifying glass that clips to the viewer so to better interpolate those last 4 digits; and, I am not giving it up because when that emp from the sun hits I am going to be in great demand.

Also, I don't know what the big deal is with portable calculators, my Versalog case came with belt loop.

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#18
In reply to #17

Re: SR71 Engine

09/21/2015 10:21 AM

when you began your career was the building electrified or did you just lite the whale oil lamp?

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#19
In reply to #18

Re: SR71 Engine

09/21/2015 10:32 AM

When I studied chemistry in school, there were just four elements!

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#29
In reply to #17

Re: SR71 Engine

09/21/2015 12:01 PM

I was a materials engineer working on satellites in the days of T squares and drafting tables. Late 60's through late 80's.

I remember seeing 30-40 drafters working on tables with Velum drawings. They all had electric erasers hanging from their tables.

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#41
In reply to #13

Re: SR71 Engine

09/21/2015 7:38 PM

They still work. I still use the 30+ I have in my collection. But few know how to use one any longer.

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#45
In reply to #13

Re: SR71 Engine

09/22/2015 12:58 PM

Were slide rules in existence when they designed the Brooklyn Bridge?

It's still standing.

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#46
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Re: SR71 Engine

09/22/2015 1:34 PM
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#14

Re: SR71 Engine

09/21/2015 8:56 AM

The cone causes a shockwave to form behind it. This shockwave causes an increase in pressure behind the cone. The increased pressure behind the cone causes the cone to be pushed forward......Think about that for a while.

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#15
In reply to #14

Re: SR71 Engine

09/21/2015 9:24 AM

Okay, then we can dispense with the fuel....

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#16
In reply to #15

Re: SR71 Engine

09/21/2015 9:27 AM

Nice, you do have to get to mach 3 first though for it to work.

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#20
In reply to #15

Re: SR71 Engine

09/21/2015 10:55 AM

No, because, at least according to Bernoulli, the exhaust velocity would, at a maximum only equal the inlet velocity. I think that means "No Thrust". I will have to get my slide rule out and verify that though.

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#25
In reply to #20

Re: SR71 Engine

09/21/2015 11:23 AM

The spinning engine parts inlet may not be where you think it is. This engine has 3 separate and discrete functional systems that provide "thrust".

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#28
In reply to #25

Re: SR71 Engine

09/21/2015 11:52 AM

My post was in response to jhotmer's statement and was totally related to the theoretical aspects of the translations from inlet velocity to static pressure to discharge velocity. It was not intended to relate to the actual mechanics of the operating engine.

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#26
In reply to #14

Re: SR71 Engine

09/21/2015 11:43 AM

I don't think the pressure moves the cone. I believe there is an actuator that adjusts the cone position for the airspeed.

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#27
In reply to #26

Re: SR71 Engine

09/21/2015 11:51 AM

Ah; the actuator moves the cone correlated with velocity to place the shockwave for best overall efficiency. I am not an expert, but a co-worker is an actual aerospace engine expert. Its all about efficiency after you get to mach 3.

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#21

Re: SR71 Engine

09/21/2015 11:07 AM

The SR-71: more proof that by putting enormous HP (as in thrust) behind it a Brick can fly.

Or was that the McDonnell-Douglas F-4 Phantom II????? Hehehehheee

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#22
In reply to #21

Re: SR71 Engine

09/21/2015 11:10 AM

who woke you up?

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#23
In reply to #22

Re: SR71 Engine

09/21/2015 11:17 AM

Mr. Coffee did....

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#34
In reply to #21

Re: SR71 Engine

09/21/2015 1:38 PM

I happened to be in the wrong place at the right time when two F-4's scrambled, right behind them when they punched AB, J-79's were impressive.

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#35
In reply to #34

Re: SR71 Engine

09/21/2015 1:46 PM

still have eyebrows?

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#36
In reply to #35

Re: SR71 Engine

09/21/2015 2:00 PM

They grew back. A benefit was, no stinking Key West NAS mosquito's for a while, they must be repelled by burnt hair.

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#24

Re: SR71 Engine

09/21/2015 11:22 AM

About the below the line quote.
I didn't know they had a Mafia problem in Rome during Julius Caesar's reign. If so, were they with him or against him?

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#30

Re: SR71 Engine

09/21/2015 12:10 PM

Naked J bird.

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#31

Re: SR71 Engine

09/21/2015 12:37 PM

Interesting post about one of my favourite all time aircraft, many thanks.

Concorde was not as fast, but carried far more passengers.....

It also had the same problems to get air into its engines, here is a good explanation for anyone interested:-

Concorde's Powerplant

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#32

Re: SR71 Engine

09/21/2015 1:16 PM

I thought these were interesting:

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#33
In reply to #32

Re: SR71 Engine

09/21/2015 1:32 PM

Nice, Thanks.

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#37

Re: SR71 Engine

09/21/2015 2:49 PM

Nice film about the Blackbird...

https://www.youtube.com/watch?v=OBVmYi7mkZM

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#38

Re: SR71 Engine

09/21/2015 4:18 PM

Here's an interesting explanation of how the P&W J-58 engines operate relative to MACH:

http://www.airspacemag.com/military-aviation/how-things-work-supersonic-inlets-35428453/?no-ist

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#39
In reply to #38

Re: SR71 Engine

09/21/2015 5:36 PM

not bad info....for a cement guy

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#42
In reply to #39

Re: SR71 Engine

09/21/2015 7:43 PM

Concrete guy, concrete....

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#43
In reply to #42

Re: SR71 Engine

09/21/2015 7:46 PM

so left out a little aggregate. don't get Psi'd

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#44
In reply to #43

Re: SR71 Engine

09/21/2015 8:02 PM

And water, and admixtures....hehehehhehe

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#40

Re: SR71 Engine

09/21/2015 5:50 PM

Every time I go to San Diego, I visit the SR-71 at San Diego Aerospace Museum.

This is my favorite "ultimate" Blackbird story:

The Ultimate Ground Speed Check - Tales from the Blackbird

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#47
In reply to #40

Re: SR71 Engine

09/22/2015 1:52 PM

Finally got a chance to read the ultimate story. Fast, just doesn't cover it. Thanks.

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#48
In reply to #40

Re: SR71 Engine

09/22/2015 2:08 PM

not too many people have a similar tale

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#49

Re: SR71 Engine

09/22/2015 5:15 PM

A small excerpt:

Written by Brian Schul - former sled (SR-71 Blackbird) driver

Under Attack

Walt continues to update me with numerous reactions he sees on the DEF panel. He

is receiving missile tracking signals. With each mile we traverse, every two

seconds, I become more uncomfortable driving deeper into this barren and hostile

land. I am glad the DEF panel is not in the front seat. It would be a big

distraction now, seeing the lights flashing. In contrast, my cockpit is 'quiet'

as the jet purrs and relishes her new-found strength, continuing to slowly

accelerate. The spikes are full aft now, tucked twenty-six inches deep into the

nacelles. With all inlet doors tightly shut, at 3.24 Mach, the J-58s are more

like ramjets now, gulping 100,000 cubic feet of air per second. We are a roaring

express now, and as we roll through the enemy's backyard, I hope our speed

continues to defeat the missile radars below. We are approaching a turn, and

this is good. It will only make it more difficult for any launched missile to

solve the solution for hitting our aircraft. I push the speed up at Walt's

request. The jet does not skip a beat, nothing fluctuates, and the cameras have

a rock steady platform. Walt received missile launch signals. Before he can say

anything else, my left hand instinctively moves the throttles yet farther

forward. My eyes are glued to temperature gauges now, as I know the jet will

willingly go to speeds that can harm her. The temps are relatively cool and from

all the warm temps we've encountered thus far, this surprises me but then, it

really doesn't surprise me. Mach 3.31 and Walt is quiet for the moment. I move

my gloved finder across the small silver wheel on the autopilot panel which

controls the aircraft's pitch. With the deft feel known to Swiss watchmakers,

surgeons, and 'dinosaurs' (old- time pilots who not only fly an airplane but

'feel it'), I rotate the pitch wheel somewhere between one-sixteenth and

one-eighth inch location, a position which yields the 500-foot-per-minute climb

I desire. The jet raises her nose one-sixth of a degree and knows, I'll push her

higher as she goes faster. The Mach continues to rise, but during this segment

of our route, I am in no mood to pull throttles back. Walt's voice pierces the

quiet of my cockpit with the news of more missile launch signals. The gravity of

Walter's voice tells me that he believes the signals to be a more valid threat

than the others. Within seconds he tells me to 'push it up' and I firmly press

both throttles against their stops. For the next few seconds, I will let the jet

go as fast as she wants. A final turn is coming up and we both know that if we

can hit that turn at this speed, we most likely will defeat any missiles. We are

not there yet, though, and I'm wondering if Walt will call for a defensive turn

off our course. With no words spoken, I sense Walter is thinking in concert with

me about maintaining our programmed course. To keep from worrying, I glance

outside, wondering if I'll be able to visually pick up a missile aimed at us.

Odd are the thoughts that wander through one's mind in times like these. I found

myself recalling the words of former SR-71 pilots who were fired upon while

flying missions over North Vietnam They said the few errant missile detonations

they were able to observe from the cockpit looked like implosions rather than

explosions. This was due to the great speed at which the jet was hurling away

from the exploding missile. I see nothing outside except the endless expanse of

a steel blue sky and the broad patch of tan earth far below. I have only had my

eyes out of the cockpit for seconds, but it seems like many minutes since I have

last checked the gauges inside. Returning my attention inward, I glance first at

the miles counter telling me how many more to go, until we can start our turn

Then I note the Mach, and passing beyond 3.45, I realize that Walter and I have

attained new personal records. The Mach continues to increase. The ride is

incredibly smooth. There seems to be a confirmed trust now, between me and the

jet; she will not hesitate to deliver whatever speed we need, and I can count on

no problems with the inlets. Walt and I are ultimately depending on the jet now

- more so than normal - and she seems to know it. The cooler outside

temperatures have awakened the spirit born into her years ago, when men

dedicated to excellence took the time and care to build her well. With spikes

and doors as tight as they can get, we are racing against the time it could take

a missile to reach our altitude.It is a race this jet will not let us lose. The Mach eases

to 3.5 as we crest 80,000 feet. We are a bullet now - except faster. We hit the turn,

and I feel some relief as our nose swings away from a country we have seen quite enough

of. Screaming past Tripoli , our phenomenal speed continues to rise, and the screaming

Sled pummels the enemy one more time, laying down a parting sonic boom. In seconds,

we can see nothing but the expansive blue of the Mediterranean . I realize that I still

have my left hand full-forward and we're continuing to rocket along in maximum

afterburner. The TDI now shows us Mach numbers, not only new to our experience

but flat out scary. Walt says the DEF panel is now quiet, and I know it is time

to reduce our incredible speed. I pull the throttles to the min 'burner range

and the jet still doesn't want to slow down. Normally the Mach would be affected

immediately, when making such a large throttle movement, but for just a few

moments old 960 just sat out there at the high Mach, she seemed to love and like

the proud Sled she was, only began to slow when we were well out of danger

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#50
In reply to #49

Re: SR71 Engine

09/22/2015 5:25 PM

Absolutely astounding!

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#51
In reply to #49

Re: SR71 Engine

09/22/2015 5:37 PM

A good read. Thanks,

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#52
In reply to #49

Re: SR71 Engine

09/22/2015 9:16 PM

Reminds me of a quote by a former SR-71 pilot:

"You haven't been lost untill you've been lost at Mach 3,"

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#53
In reply to #49

Re: SR71 Engine

09/30/2015 12:12 PM

I remember reading this a while ago. Remind me where it was published - Wings, Airpower? Sadly defunct now.

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