SR-71 Blackbird fun facts

James Snover

The Ill-Advised Physics Amplification Co
Established Member
Premium Member
Joined
Jan 23, 2008
Messages
8,862
Location
Cypress
The Blackbird predated inertial navigation and GPS. And it went too fast for LORAN and other conventional aviation nav aids. And at the speeds it traveled, a few tenths of a degree of error in the flight path meant hundreds of miles of error at the point you needed the cameras to roll, at the point at which you were supposed to meet up with the tanker, etc. All very bad things.

To solve it, Lockheed developed an automated star-tracking telescope system. It had enough memory for something like 15 constellations, and it could see the brightest stars even in full daylight. It worked, very well. It had a few drawbacks, though. Sometimes, if there were any small holes in the canopy of the covered revetments they housed the Blackbirds in prior to takeoff, as they "spun up" the star tracking system, it would see the small holes, interpret them as a constellation, lock on, and start throwing up all sorts of errors. BNefore it even released the brakes for taxi out to the runway.

There is a myth that the Blackbird could not takeoff with full tanks of fuel. Not true, and on several missions, that was exactly what they did. They reason they didn't was that a full load of fuel increased the weight on the wheels by another 100,000lbs. This increased your takeoff run, it cut the "takeoff abort point" by a huge margin, because the brakes just couldn't slow all that down, and if they lost an engine on takeoff, they're options were severely reduced with regard to doing a go-around and coming in for landing. One engine, at full fuel load, even on full afterburner, could not maintain level flight with the landing gear down. It was far better to take off with minimal fuel, heat up, then meet up with a tanker and top off.

The most critical time element in a Blackbird mission was take-off time. Ironically, despite being the fastest aircraft in the skies, the Blackbird could not make up for lost time in the air. Because it's cruise speed WAS it's max speed, an oddity in the aviation world. There are unsubstantiated reports of Blackbirds temporarily exceeding Mach 3.2 and flying higher than 85,000 feet, but it was only to outrun missiles. And the folks telling me these things usually then say, "It'd do it, but it wasn't happy doing it." Whereas it would happily cruise all day long at Mach 3.2 at 80,000-85,000 feet. In any event, she couldn't go much faster than 3.2 for long before important things, like the engines, began to melt.

They couldn't make the old girl fly truly straight and level. The best the could get was a constant slight climb and descent. So if they were aiming for 80,000 feet altitude, they'd set it up for a slow climb to 85,000, then a slow descent to 75,000, repeat as needed.
 

scott_0

Well-Known Member
Established Member
Joined
Jul 30, 2011
Messages
4,337
Location
Pa
absolutely love this amazing piece of art that is the sr71


Sent from my iPhone using Tapatalk
 

7998

Don't Care
Established Member
Malt Liquor Mafia
Joined
Mar 12, 2008
Messages
3,766
Location
PA
One of my favorite aircraft. What amazes me about the SR-71 and the Space program is what they could accomplish with the resources they had available. It seems all of our modern technology was developed within this period.
@James Snover I'm curious, what is your relation to the SR-71?
 

AustinSN

Well-Known Member
Established Member
Beer Money Bros.
Joined
Jan 29, 2014
Messages
6,408
Location
the plains
One of my favorite aircraft. What amazes me about the SR-71 and the Space program is what they could accomplish with the resources they had available. It seems all of our modern technology was developed within this period.
@James Snover I'm curious, what is your relation to the SR-71?
More than you'd ever expect.

What do you think the SR is for?

SnoveR
 

SonicDTR

Wasn't me.
Established Member
Premium Member
Joined
Sep 23, 2007
Messages
5,244
Location
Midwest
Always love SR-71 facts.

Did you say 100,000 lbs extra for just a full load of FUEL?!
 

James Snover

The Ill-Advised Physics Amplification Co
Established Member
Premium Member
Joined
Jan 23, 2008
Messages
8,862
Location
Cypress
One of my favorite aircraft. What amazes me about the SR-71 and the Space program is what they could accomplish with the resources they had available. It seems all of our modern technology was developed within this period.
@James Snover I'm curious, what is your relation to the SR-71?

None at all. Just over the last forty years I have collected every bit of info on it I can find. Talked to pilots and crew. Bought every book on it I can find.

By far, the best single book on the Blackbird is Ben Rich's autobiography, "Skunkworks." He is the guy who designed the inlets, and designed the aircraft's thermodynamics. He was Kelly Johnson's right-hand man.

That book has so much info on the design and building of the old girl I was surprised it was allowed to be published.

Rich Graham has written a whole series of books on the Blackbird. He was a pilot of the bird, and then he was in charge of the whole program.


Sent from my iPad using the svtperformance.com mobile app
 

CobraBob

Authorized Vendor
Established Member
Premium Member
Single Barrel Sirs
Joined
Nov 17, 2002
Messages
105,349
Location
Cheshire, CT
Nice write-up James. I've always been fascinated with the Blackbird. Pretty much everyone is.
 

ON D BIT

Finish First
Established Member
Joined
Jul 7, 2003
Messages
16,212
Location
Currently in Sonoma County
Love the Entire Skunkworks team, my grandpa was a part of this team and helped design build the SR71. Sadly he past before I knew anything about his work or this plane.
 

James Snover

The Ill-Advised Physics Amplification Co
Established Member
Premium Member
Joined
Jan 23, 2008
Messages
8,862
Location
Cypress
Always love SR-71 facts.

Did you say 100,000 lbs extra for just a full load of FUEL?!
Yep. Distributed throughout various tanks to control the aircraft's center of gravity vs. it's center of lift. By shifting the fuel around, they could trim it out without having to deflect the control surfaces, which would have added a lot of drag. The center of gravity had to be watched constantly because it changes with the speed of the aircraft, too far forward or aft, and at the veary least your fuel consumption goes through the roof, and at the very worst, the plane becomes unflyable and destroys itself.

There was a container of liquid nitrogen onboard, as the fuel was consumed, the tanks were filled with liquid nitrogen so there couldn't be a fire.

The fuel was notoriously un-inflammable. You could fill a bucket with it, drop a match in it, and the match would go out. It absolutely would not catch on fire. So they also used the fuel as coolant, to pull heat away from the hottest parts of the airframe. Thsi alo preheated the fuel, so when it did hit the combustion chambers, it would burn.

On takeoff, though, they had to add a shot of TEB, tetra-ethyl-borane, a chemical compound so nasty it instantly burst into flame on contact with air. That would at least allow the fuel to ignite in cold combustion chambers. Also had to have a shot of TEB when they lit the afterburners, if they had been shut down. The throttle had a counter on it: it displayed the number of shots of TEB available, it counted down from 50. When you ran out of TEB, you could not relight the afterburners. And if the engines flamed out, and you had no TEB, you were very quickly going to be back on the ground because you could not restart the engines without it. They were difficult enough to restart, even with it.

It took up to 25 minutes to refuel once they found the tanker. Oddly, only one half of the windshield had a defroster, and at 30,000 or so feet at -40F, the Blackbird cooled off fast, and the windshield frosted over almost immediately.

EDIT: The fuel was notoriously UN-inflammable was what I meant to say. Corrected it up above, but just so everyone knows: I mis-typed it, originally. No doubt some form of Russian interference, I'm certain ...
 
Last edited:

James Snover

The Ill-Advised Physics Amplification Co
Established Member
Premium Member
Joined
Jan 23, 2008
Messages
8,862
Location
Cypress
Probably past that now. The give away of a pulse engine, the donuts on a rope contrail were seen as far back as the 80’s.


Sent from my iPhone using the svtperformance.com mobile app
Yep. And, even more interestingly, until recently, tracked by ground seismometers looking for earthquakes.
 

Users who are viewing this thread



Top