They figured all of this out without powerful computers and without being able to simulate the speeds on the ground.
How the SR-71's engine works(P&W J58)
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Actually I think the most impressive "non-computer" aspect isn't the speed but the nascent stealth technologies.
Very impressive considering the technology they had way back then.
Actually, even more impressive than the stealth is the "mice" in the intake.
Let me explain: the annular area in the intake, aft of the spike, was critical to Mach 3 flight. The spike had to be positioned with an accuracy of 0.1" for the inlet to function properly, decelerating and compressing the air for the J-58.
They calculated the annular area with a slide rule. But once the tooling was built, and the inlet assembled, changing the size would have required redesign and retooling. So, in case flight test demonstrated that they needed to adjust the area, they built it a hair bigger than calculated, then they added small bumps, the size of mice, were bolted into the throat to slightly reduce its size. They could increase the throat size (annular area) by removing mice to fine tune the inlet.
But the slide rule calculations on pressure and supersonic flow were perfect.
The original mice stayed in place for the entire service life of the airplane. There was no need to ever adjust the inlet size.
Let me explain: the annular area in the intake, aft of the spike, was critical to Mach 3 flight. The spike had to be positioned with an accuracy of 0.1" for the inlet to function properly, decelerating and compressing the air for the J-58.
They calculated the annular area with a slide rule. But once the tooling was built, and the inlet assembled, changing the size would have required redesign and retooling. So, in case flight test demonstrated that they needed to adjust the area, they built it a hair bigger than calculated, then they added small bumps, the size of mice, were bolted into the throat to slightly reduce its size. They could increase the throat size (annular area) by removing mice to fine tune the inlet.
But the slide rule calculations on pressure and supersonic flow were perfect.
The original mice stayed in place for the entire service life of the airplane. There was no need to ever adjust the inlet size.
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Very impressive machine. When I lived in California, (Lancaster/Palmdale), I actually got to see one of these up close and personal.
And just to be clear, it's not that computers allow you to do things that you would not otherwise be able to do (for the most part), it's just that they can do it faster. A calculation is a calculation whether it is done by a fleet of engineers by hand or by a computer. They knew a lot about airflow and aerodynamics in the 50's. It just required a lot more wind tunnel time and test pilots than it does today. Plus they had a lot of experience with other aircraft such as the XB-70 to draw upon.
Not that I really know, but I'm not so sure the Internet stories about "no" computers being used is accurate. They had computers in the 50's that would have been available to large defense contractors of the time. If not digital then surely analog ones, the first SR-71s had an analog computer to control the engine inlet, right?
You certainly couldn't have built a B-2 or even an F-117 back then. But they did know how to build fast airplanes.
Not that I really know, but I'm not so sure the Internet stories about "no" computers being used is accurate. They had computers in the 50's that would have been available to large defense contractors of the time. If not digital then surely analog ones, the first SR-71s had an analog computer to control the engine inlet, right?
You certainly couldn't have built a B-2 or even an F-117 back then. But they did know how to build fast airplanes.
The SR-71 is IMHO the best looking aircraft of all time.
I'm sure it was mistaken for a UFO when being tested at Groom Lake...
I'm sure it was mistaken for a UFO when being tested at Groom Lake...
I agree. It looks fast even when sitting still.
Originally Posted By: RF Overlord
The SR-71 is IMHO the best looking aircraft of all time.
Originally Posted By: RF Overlord
The SR-71 is IMHO the best looking aircraft of all time.
The entire airplane is an engineering tour de force. Definitely my favorite non-combat plane of all time, bar none.
I got to see one in person back in the '80's as a member of the Civil Air Patrol. I was lucky enough to be at Homestead Air Force Base and there was one there being "debriefed"; doing Intel on Cuba no doubt. Though we couldn't get within about a 1/4 mile of it, we were all in absolute awe.
I got to see one in person back in the '80's as a member of the Civil Air Patrol. I was lucky enough to be at Homestead Air Force Base and there was one there being "debriefed"; doing Intel on Cuba no doubt. Though we couldn't get within about a 1/4 mile of it, we were all in absolute awe.
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Fact or fiction...
In the late 1980's, I read in the Wall Street Journal a story that stated that the SR-71 Blackbird was operational and flying for a full two years before it was rumured to exist. Talk about people keeping a secret/
In the late 1980's, I read in the Wall Street Journal a story that stated that the SR-71 Blackbird was operational and flying for a full two years before it was rumured to exist. Talk about people keeping a secret/
Very impressive.
The first of the type were designed as high altitude interceptors, hence the "A 12" dsignation.
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Skunk works by Ben R. Rich is a really enjoyable book for aviation fans. I went to an air show at Beal AFB years ago and was able to get up close to the SR71 and them they did a flight demo. Watching the take off, all I can say is that it has get up and go!!! It seems it should be the Bat plane [bat man]
Originally Posted By: Kuato
Fastest airplane ever, designed on a slide rule. That's sayin' something.
YES!!!!!!!!!!!! fantastic air craft.
Just thinking here, Could the Space Shuttle be the fastest aircraft (glider) once it reentered the earths atmosphere?
Fastest airplane ever, designed on a slide rule. That's sayin' something.
YES!!!!!!!!!!!! fantastic air craft.
Just thinking here, Could the Space Shuttle be the fastest aircraft (glider) once it reentered the earths atmosphere?
Originally Posted By: Astro14
Actually, even more impressive than the stealth is the "mice" in the intake.
Let me explain: the annular area in the intake, aft of the spike, was critical to Mach 3 flight. The spike had to be positioned with an accuracy of 0.1" for the inlet to function properly, decelerating and compressing the air for the J-58.
They calculated the annular area with a slide rule. But once the tooling was built, and the inlet assembled, changing the size would have required redesign and retooling. So, in case flight test demonstrated that they needed to adjust the area, they built it a hair bigger than calculated, then they added small bumps, the size of mice, were bolted into the throat to slightly reduce its size. They could increase the throat size (annular area) by removing mice to fine tune the inlet.
But the slide rule calculations on pressure and supersonic flow were perfect.
The original mice stayed in place for the entire service life of the airplane. There was no need to ever adjust the inlet size.
Have you seen this?
http://www.enginehistory.org/Convention/2013/HowInletsWork8-19-13.pdf
Actually, even more impressive than the stealth is the "mice" in the intake.
Let me explain: the annular area in the intake, aft of the spike, was critical to Mach 3 flight. The spike had to be positioned with an accuracy of 0.1" for the inlet to function properly, decelerating and compressing the air for the J-58.
They calculated the annular area with a slide rule. But once the tooling was built, and the inlet assembled, changing the size would have required redesign and retooling. So, in case flight test demonstrated that they needed to adjust the area, they built it a hair bigger than calculated, then they added small bumps, the size of mice, were bolted into the throat to slightly reduce its size. They could increase the throat size (annular area) by removing mice to fine tune the inlet.
But the slide rule calculations on pressure and supersonic flow were perfect.
The original mice stayed in place for the entire service life of the airplane. There was no need to ever adjust the inlet size.
Have you seen this?
http://www.enginehistory.org/Convention/2013/HowInletsWork8-19-13.pdf
Originally Posted By: chiefsfan1
Originally Posted By: Astro14
Actually, even more impressive than the stealth is the "mice" in the intake.
Let me explain: the annular area in the intake, aft of the spike, was critical to Mach 3 flight. The spike had to be positioned with an accuracy of 0.1" for the inlet to function properly, decelerating and compressing the air for the J-58.
They calculated the annular area with a slide rule. But once the tooling was built, and the inlet assembled, changing the size would have required redesign and retooling. So, in case flight test demonstrated that they needed to adjust the area, they built it a hair bigger than calculated, then they added small bumps, the size of mice, were bolted into the throat to slightly reduce its size. They could increase the throat size (annular area) by removing mice to fine tune the inlet.
But the slide rule calculations on pressure and supersonic flow were perfect.
The original mice stayed in place for the entire service life of the airplane. There was no need to ever adjust the inlet size.
Have you seen this?
http://www.enginehistory.org/Convention/2013/HowInletsWork8-19-13.pdf
That is a great link! No, I've not seen it before, but I've downloaded it onto my iPad to read later. I just remember the anecdote from Ben Rich's book, "Skunkworks", which I read years ago...and I understand a bit on how the inlet works from other sources. The F-14's inlet was designed for lower speed (2.3 IMN) but also for high alpha performance, so many of the principles are the same, but the execution is far different...
Thanks!
Originally Posted By: Astro14
Actually, even more impressive than the stealth is the "mice" in the intake.
Let me explain: the annular area in the intake, aft of the spike, was critical to Mach 3 flight. The spike had to be positioned with an accuracy of 0.1" for the inlet to function properly, decelerating and compressing the air for the J-58.
They calculated the annular area with a slide rule. But once the tooling was built, and the inlet assembled, changing the size would have required redesign and retooling. So, in case flight test demonstrated that they needed to adjust the area, they built it a hair bigger than calculated, then they added small bumps, the size of mice, were bolted into the throat to slightly reduce its size. They could increase the throat size (annular area) by removing mice to fine tune the inlet.
But the slide rule calculations on pressure and supersonic flow were perfect.
The original mice stayed in place for the entire service life of the airplane. There was no need to ever adjust the inlet size.
Have you seen this?
http://www.enginehistory.org/Convention/2013/HowInletsWork8-19-13.pdf
That is a great link! No, I've not seen it before, but I've downloaded it onto my iPad to read later. I just remember the anecdote from Ben Rich's book, "Skunkworks", which I read years ago...and I understand a bit on how the inlet works from other sources. The F-14's inlet was designed for lower speed (2.3 IMN) but also for high alpha performance, so many of the principles are the same, but the execution is far different...
Thanks!
Originally Posted By: Astro14
Originally Posted By: chiefsfan1
Originally Posted By: Astro14
Actually, even more impressive than the stealth is the "mice" in the intake.
Let me explain: the annular area in the intake, aft of the spike, was critical to Mach 3 flight. The spike had to be positioned with an accuracy of 0.1" for the inlet to function properly, decelerating and compressing the air for the J-58.
They calculated the annular area with a slide rule. But once the tooling was built, and the inlet assembled, changing the size would have required redesign and retooling. So, in case flight test demonstrated that they needed to adjust the area, they built it a hair bigger than calculated, then they added small bumps, the size of mice, were bolted into the throat to slightly reduce its size. They could increase the throat size (annular area) by removing mice to fine tune the inlet.
But the slide rule calculations on pressure and supersonic flow were perfect.
The original mice stayed in place for the entire service life of the airplane. There was no need to ever adjust the inlet size.
Have you seen this?
http://www.enginehistory.org/Convention/2013/HowInletsWork8-19-13.pdf
That is a great link! No, I've not seen it before, but I've downloaded it onto my iPad to read later. I just remember the anecdote from Ben Rich's book, "Skunkworks", which I read years ago...and I understand a bit on how the inlet works from other sources. The F-14's inlet was designed for lower speed (2.3 IMN) but also for high alpha performance, so many of the principles are the same, but the execution is far different...
Thanks!
You are welcome!! page 10 has a cool pic of the SR71 I have not seen before. Its the one plane I have never seen fly either. Although on its last retirement flight from LA to DC I calculated the flight time on when it would hit KC. It was cloudy that day but I heard the BOOOM. That night on the news there was a report on it and said from KC to St. Louis was IIRC 7 minutes.
Originally Posted By: chiefsfan1
Originally Posted By: Astro14
Actually, even more impressive than the stealth is the "mice" in the intake.
Let me explain: the annular area in the intake, aft of the spike, was critical to Mach 3 flight. The spike had to be positioned with an accuracy of 0.1" for the inlet to function properly, decelerating and compressing the air for the J-58.
They calculated the annular area with a slide rule. But once the tooling was built, and the inlet assembled, changing the size would have required redesign and retooling. So, in case flight test demonstrated that they needed to adjust the area, they built it a hair bigger than calculated, then they added small bumps, the size of mice, were bolted into the throat to slightly reduce its size. They could increase the throat size (annular area) by removing mice to fine tune the inlet.
But the slide rule calculations on pressure and supersonic flow were perfect.
The original mice stayed in place for the entire service life of the airplane. There was no need to ever adjust the inlet size.
Have you seen this?
http://www.enginehistory.org/Convention/2013/HowInletsWork8-19-13.pdf
That is a great link! No, I've not seen it before, but I've downloaded it onto my iPad to read later. I just remember the anecdote from Ben Rich's book, "Skunkworks", which I read years ago...and I understand a bit on how the inlet works from other sources. The F-14's inlet was designed for lower speed (2.3 IMN) but also for high alpha performance, so many of the principles are the same, but the execution is far different...
Thanks!
You are welcome!! page 10 has a cool pic of the SR71 I have not seen before. Its the one plane I have never seen fly either. Although on its last retirement flight from LA to DC I calculated the flight time on when it would hit KC. It was cloudy that day but I heard the BOOOM. That night on the news there was a report on it and said from KC to St. Louis was IIRC 7 minutes.
oh, for Christmas wifey got me the SR-71 Hallmark ornament! if any are left get one. Its made of metal not plastic.
http://shop.hallmark.com/christmas/christmas-ornaments/lockheed-sr-71-blackbird-1795QXI2853.html
http://shop.hallmark.com/christmas/christmas-ornaments/lockheed-sr-71-blackbird-1795QXI2853.html
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