SR-71 Blackbird .... the engines

[otispunkmeyer]

what are those spikes for at the front of the engine? they move in and out and id read somewhere that at top speed and high altitude that these spikes moved all the way forward and that the engine some how operated as a "scram/ram-jet"

this true?

 

[leftyman]

dont know, i usually fly Jet Blue

 

[Savij]

something about manipulate the shockwave to slow down the air slow enough for it to ignite.

 

[iamwiz82]

Originally posted by: Savij
something about manipulate the shockwave to slow down the air slow enough for it to ignite.

I believe there was just a post about this the other day.

 

[andy9o]

yes, the SR-71 was (I think) the first non-experimental aircraft to use scramjet engines (while in flight)

 

[Savij]

Originally posted by: iamwiz82

Originally posted by: Savij
something about manipulate the shockwave to slow down the air slow enough for it to ignite.

I believe there was just a post about this the other day.

could be...

 

[scorpmatt]

not sure about how that part of the engine works, but I know that below a certain height, it leaked fuel like a squirter on weed

 

[otispunkmeyer]

wait found it


The J58 engines operate as ordinary jets at low speeds, switching to become ramjets at higher speeds above 2,000 m.p.h.

from here SR-71.org

i didnt think it was true, guess it is....would be interesting so know exactly how it did that

 

[iamwiz82]

Originally posted by: Savij

Originally posted by: iamwiz82

Originally posted by: Savij
something about manipulate the shockwave to slow down the air slow enough for it to ignite.

I believe there was just a post about this the other day.

could be...

http://forums.anandtech.com/messageview...atid=38&threadid=1671584&enterthread=y

Found it

 

[OulOat]

The SR-71's inlet configuration was automatically adjusted during supersonic flight to decelerate air flow in the duct, slowing it to subsonic speed before reaching the engine's face. This was accomplished by the inlet's center-body spike translating aft, and by modulating the inlet's forward bypass doors.

read

 

[novasatori]

they slow the air to subsonic speeds before it enters the engine iirc

 

[So]

Definitely NOT a scramjet.

 

[dawks]

Originally posted by: OulOat

The SR-71's inlet configuration was automatically adjusted during supersonic flight to decelerate air flow in the duct, slowing it to subsonic speed before reaching the engine's face. This was accomplished by the inlet's center-body spike translating aft, and by modulating the inlet's forward bypass doors.

read

Yup. They did the same sort of thing on the concorde. It had adjustable panels on its intakes..

You can kind of see them here.

 

[Phoenix86]

From the thread linkage above.

The SR-71's
inlet configuration was automatically adjusted during supersonic flight
to decelerate air flow in the duct, slowing it to subsonic speed before
reaching the engine's face. This was accomplished by the inlet's
center-body spike translating aft, and by modulating the inlet's
forward bypass doors. Normally, these actions were scheduled automatically as a
function of Mach number, positioning the normal shock wave (where air
flow becomes subsonic) inside the inlet to ensure optimum engine
performance.

Without proper scheduling, disturbances inside the inlet could result
in the shock wave being expelled forward--a phenomenon known as an "inlet
unstart." That causes an instantaneous loss of engine thrust, explosive
banging noises and violent yawing of the aircraft--like being in a
train wreck. Unstarts were not uncommon at that time in the SR-71's
development, but a properly functioning system would recapture the shock wave and
restore normal operation.

It's a good read, but sad story.

 

[Gravity]

One of my friends in Fl worked on them for 13 years. he says they were miraculous.

 

[otispunkmeyer]

Originally posted by: dawks

Originally posted by: OulOat

The SR-71's inlet configuration was automatically adjusted during supersonic flight to decelerate air flow in the duct, slowing it to subsonic speed before reaching the engine's face. This was accomplished by the inlet's center-body spike translating aft, and by modulating the inlet's forward bypass doors.

read

Yup. They did the same sort of thing on the concorde. It had adjustable panels on its intakes..

You can kind of see them here.

they do the same kinda thing on all super sonic engines....the blades just arent strong enough to withstand the forces generated by the pressure/sonic booms.

id just read somewhere that it became a scram/ram jet engine....which doesnt use any moving parts, just the way its shaped and the air speed are enough to compress the fuel-air mix enough to make it ignite

 

[GTaudiophile]

Originally posted by: Gravity
One of my friends in Fl worked on them for 13 years. he says they were miraculous.

And my guess is, despite the SR-71 having been retired a decade ago, you'll still probably couldn't get ahold of an engine to examine for kicks and giggles.

 

[GTaudiophile]

The J58, developed in the late 1950s, was selected for the SR-71 Blackbird reconnaissance aircraft. The first engine designed to be flight-qualified at Mach 3 for the Air Force, it required new materials and fuel that could withstand the temperatures and stresses it would encounter. In July 1976, J58 engines powered an SR-71 to a world altitude record of 84,069 feet (25,624 kilometers) and a second Blackbird to a world speed record of 2,193 miles per hour (3,529 kilometers per hour).

A google search for "Pratt & Whitney J58" yields some interesting articles.

Cool Pic!

 

[GTaudiophile]

After having read a little about the engine, it's not the engine itself that was so revolutionary and secret. It was rather the hydraulic "spike" and inlet system that was really revolutionary.

 

[batmang]

Originally posted by: otispunkmeyer

Originally posted by: dawks

Originally posted by: OulOat

The SR-71's inlet configuration was automatically adjusted during supersonic flight to decelerate air flow in the duct, slowing it to subsonic speed before reaching the engine's face. This was accomplished by the inlet's center-body spike translating aft, and by modulating the inlet's forward bypass doors.

read

Yup. They did the same sort of thing on the concorde. It had adjustable panels on its intakes..

You can kind of see them here.

they do the same kinda thing on all super sonic engines....the blades just arent strong enough to withstand the forces generated by the pressure/sonic booms.

id just read somewhere that it became a scram/ram jet engine....which doesnt use any moving parts, just the way its shaped and the air speed are enough to compress the fuel-air mix enough to make it ignite

^^^^

that is incredible.

 

[SVT Cobra]

Originally posted by: So
Definitely NOT a scramjet.

:thumbsup:

 

[GTaudiophile]

Originally posted by: Son of a N00b

Originally posted by: So
Definitely NOT a scramjet.

:thumbsup:

It's referred to as a "turbo-ramjet" engine.

 

[Fenixgoon]

my brother took a class on scramjet technology.. im not sure how interested he was, but it sounds cool