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The SR-71 Blackbird Astro-Nav System worked by tracking the stars

theaviationgeekclub.com

141–150 of 358 posts

Re: The SR-71 Blackbird Astro-Nav System worked by tracking the stars

#141
post #76
post #9

Earlier quoted context omitted.

I got to see an SR-71 on display in New York several years ago. What really struck me was how BIG it was, seeing pictures of it doesn't really give you sense of scale, it was a massive plane.

You can get close enough to touch (but you mustn’t touch) the SR71 at the Udvar-Hazy center of the Smithsonian!

I have definitely touched the SR-71 at the Evergreen museum in Oregon.

Re: The SR-71 Blackbird Astro-Nav System worked by tracking the stars

#142

Earlier quoted context omitted.

Even more impressive seeing it sweat fuel onto the apron in the afternoon sun for a few hours then engine ignition with Chevy V8 start cart, takeoff followed by low level transonic flyby. Fairford IAT 1989.

What kinda specialised monster engines is that plane running, holy hell.

The fuel doesn't ignite at "low" temperatures, one reason is because the whole airplane leaks fuel until it's at an high enough speed. At that point, maybe because of the surface temperature, or the forces it tackles at Mach 3+, the whole thing becomes airtight.

At least, that's what I remember.

Re: The SR-71 Blackbird Astro-Nav System worked by tracking the stars

#143
post #101

I'm going to replay this from memory without googling it, just to keep the late 20th century air of some people swapping unverifiable facts in a pub: There was an old friend of my mother's, now deceased, who was a retired engineer. He claimed to be the guy who invented the 2-part tuna can, and was known for handing out end chunks of titanium castings left over from some business he ran. At any rate, he had a couple o…

My father worked on the guidance system for the Trident nuclear missile at Singer-Kearfott for many years and this is mostly accurate. There was a lot of geometry involved. They used to test launch the missiles back during the cold war from submarines off of California. The missile would cross the continental US and land in the water off Florida. The Soviets would invariably send "fishing" boats to measure the tests…

It's not just analog tech: it's actual engineering. The hardware we have is amazing, most of our software royally sucks. But software done right is also most impressive.

Re: The SR-71 Blackbird Astro-Nav System worked by tracking the stars

#144

I did a toy implementation of a star camera: https://nickp.svbtle.com/star-cameras

The article seems to skip the matching part. I see it in the source code though. But it looks like it's just using two stars, how does that work? I know ASTAP and Astromentry.Net use three or four stars and compute the angles and distances between them.

Re: The SR-71 Blackbird Astro-Nav System worked by tracking the stars

#147

> the flight plan was recorded on a punched tape that told the aircraft where to go, when to turn, and when to turn the sensors on and off. This is equally fascinating to me. Before each flight, someone had to generate a flight plan and punch it onto a physical tape, then load it into the plan. T No mid-flight "re-calculating route" if stuff goes wrong. One of the most interesting and under-appreciated aspects of ear…

This vastly, vastly oversells the stakes of Midway. Japan lost before the war ever began[1]. By the end of the war the US produced 17 fleet carriers, 9 light carriers, and 76 escort carriers. US strength at Midway was 3 fleet carriers. By the end of 1945 the US would still have built several new Navies as well as the atomic bomb. Japan was struggling to finish China on their side of the Pacific, their armed forces would be totally incapable of securing the sea lanes to the US let alone land such a massive invasion force as to sweep across the whole continent.

The Japanese war plan was strategically inept from the outset - hit the US really hard, then sue for peace from a position of strength. But even if they got the carriers at Pearl Harbor, it was only a matter of time before US industrial output buried them and they failed to account for an enemy committed to total war. The turning point happened at Midway but the specific time and place don't really matter - it was inevitable. For Japan to win the war they would have had to walk an improbable golden path from victory to decisive victory while suffering no irreplaceable losses.

By the way, Germany displayed similar strategic ineptitude. Even if Germany won the Battle of Britain, they would not have been able to supply any invasion force they managed to land on Britain. They had no surface fleet, and they were staring down the largest navy in the world! All the Royal Navy needs to do is contest the Channel for a critical week or two and you've just lost your entire invasion force. As it happens they lost the BoB. Unable to finish the war against a globe-spanning empire, they proceeded to send their entire army into the USSR...

...and while US lend-lease certainly helped, the Soviet counteroffensive at the end of 1941 already inflicted such damage on the Wehrmacht that they started suffering shortages of men and equipment. The unsuccessful German offensive in 1942, Case Blue, was more limited in scope than Barbarossa because of these shortages - attacking in the southern USSR rather than the entire front as in 1941. Case Blue started the same month as the Battle of Midway - the outcome of the two could hardly be linked. With or without lend-lease, by end of '42 they are knee-deep in Russia with no prospect of further advance, while Britain blockades them on the other side.

1: https://www.youtube.com/watch?v=l9ag2x3CS9M

Re: The SR-71 Blackbird Astro-Nav System worked by tracking the stars

#148

Interesting that it’s not confirmed if the SR-71 flew in the Southern Hemisphere. Would be a very bold design if it didn’t and the system wasn’t designed for it.

According to the documentation of the Astro-Nav System, it is designed to operate in polar areas [1].

[1] https://airandspace.si.edu/webimages/collections/full/NAS-14...

Re: The SR-71 Blackbird Astro-Nav System worked by tracking the stars

#149

Earlier quoted context omitted.

We had a great example of this in a recent Geomob London talk: ask Google Maps to route from Wairiki, Fiji (-16.8048, 179.9893) to Welagi, Fiji (-16.7349, -179.9439), two villages on the coastal road of the same island and about 10km apart, but as you can see from the coordinates on opposite sides of the anti-meridian. You get "Sorry, we could not calculate driving directions from "Wairiki, Fiji" to "Welagi, Fiji" ht…

It astounds me that this is still a problem in 2023. I company I coded for surveyed the entire Fiji region in 1997, drafting aircraft at 80m ground clearance in long lines across both sides of the 180 longitude line. Every single bit of commercial US GIS software available at the time was garbage and failed to correctly compute line lengths that straddled the 180 longitude line, areas of rectangles that did the same,…

I'll bet if SV wasn't such a hotspot that such things would be handled better. You can't dogfood this if you're in Mountain View and chances are that the intersection of 'people working on Google Maps' and 'people that use Google Maps in Fiji' is empty.

Re: The SR-71 Blackbird Astro-Nav System worked by tracking the stars

#150
post #101

I'm going to replay this from memory without googling it, just to keep the late 20th century air of some people swapping unverifiable facts in a pub: There was an old friend of my mother's, now deceased, who was a retired engineer. He claimed to be the guy who invented the 2-part tuna can, and was known for handing out end chunks of titanium castings left over from some business he ran. At any rate, he had a couple o…

the "quartz crystals" were likely optical flats and they were connected by wringing-on (like a set of gauge blocks). https://en.wikipedia.org/wiki/Optical_flat#Wringing I'm not sure why you'd use an optical flat in a missle nav system, now I'm curious.
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