This was posted a few months ago. It's a short but fun read:
SR-71 Blackbird Speed Check Story
https://news.ycombinator.com/item?id=36041845
https://www.thesr71blackbird.com/Aircraft/Stories/sr-71-blac...
The SR-71 Blackbird Astro-Nav System worked by tracking the stars
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Re: The SR-71 Blackbird Astro-Nav System worked by tracking the stars
#172Is anyone working on vision-based navigation systems for drones, these days?
Re: The SR-71 Blackbird Astro-Nav System worked by tracking the stars
#173Earlier quoted context omitted.
There's another one in the Museum of Flight in Seattle.
The Museum of Flight has an M-21 - in the Blackbird family but a few feet shorter than the SR-71. It's a truly wonderful plane and I love that you can walk underneath it and get right up close. As I recall they also have one of the engines pulled out to look at as well.
The Museum of Flight also has an entire SR-71 cockpit (salvaged from a crash) that visitors can sit in. It's the only place I know of in the world where regular people are encouraged to touch one.
Re: The SR-71 Blackbird Astro-Nav System worked by tracking the stars
#174Earlier 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.
There's an A-12, the CIA version of the Blackbird, on the deck of the USS Intrepid, in New York. It is indeed a very large aircraft! (I was also impressed by how many aircraft could fit on an aircraft carrier. There was also a Concorde!)
Don't forget the Space Shuttle Enterprise complete with its own separate pavilion; aircraft carriers are indeed ginormous, and that's just an ancient WWII model: https://www.intrepidmuseum.org/Space_Shuttle_Pavilion.aspx
Re: The SR-71 Blackbird Astro-Nav System worked by tracking the stars
#175Earlier quoted context omitted.
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…
As far as I’m aware test shots of both us Air Force and navy icbms off the west coast went to Kwajalein atoll. Some other interesting details… Naval icbms have star tracking for alignment and correction but land based ones do not. The reasoning is that they are all dead reckoning…which requires knowing the initial location. The silo doesn’t move, but the subs do. Their location is tracked with another inertial guidan…
From what I recall land missiles (minuteman) does its own alignment while in the silo to give it what it needs to hit that window in space where the RV detaches. There some documentation and YouTube videos depicting the alignment process.
Re: The SR-71 Blackbird Astro-Nav System worked by tracking the stars
#176Earlier quoted context omitted.
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.
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Re: The SR-71 Blackbird Astro-Nav System worked by tracking the stars
#177It was a huge waste of money, the US was always a paranoid state which was extraordinarily secure. This is precisely what Eisenhower warned about, the rise of the MIC which has its own self-sustaining logic.
Re: The SR-71 Blackbird Astro-Nav System worked by tracking the stars
#178There's a sad poetry that the simplest ICBM guidance is a camera that simply watches the stars.
They are so beautiful though:
https://en.m.wikipedia.org/wiki/LGM-118_Peacekeeper#/media/F...
Re: The SR-71 Blackbird Astro-Nav System worked by tracking the stars
#179You can see one of these up close - both the device, and the airplane! - at the Evergreen Aerospace Museum in McMinnville, OR. They also have on display another Blackbird payload labeled DEF-H. It’s a nondescript white box which you are allowed to look at, but not allowed to know what it does. XD
Had the plane as a wall to wall poster as a kid. And now finding out its next door! Super excited.
Re: The SR-71 Blackbird Astro-Nav System worked by tracking the stars
#180Earlier quoted context omitted.
> when you're at 85,000 feet (as noted, the SR-71's cruising altitude), the concept of a blue "daylight" that blocks the view of space only exists below you, not above you The Astro-Nav System didn't work only at cruising altitude, it tracked stars even when the SR-71 was on the ground. [1] [1] https://airandspace.si.edu/webimages/collections/full/NAS-14...
> The Astro-Nav System didn't work only at cruising altitude, it tracked stars even when the SR-71 was on the ground. [1] > > [1] https://airandspace.si.edu/webimages/collections/full/NAS-14 ... I don't necessarily doubt you, but linking to a 76-page PDF without any indication of where the reader is supposed to find support for your claims is not nearly as convincing as you think it is.
> I don't necessarily doubt you, but linking to a 76-page PDF without any indication of where the reader is supposed to find support for your claims is not nearly as convincing as you think it is.
It's funny you say that, because based on almost all the assertions you read here on HN which are taken for granted without any links to support them, you'd think linking to an authoritative PDF would be more convincing than if I hadn't linked to it. But based on your comment it seems like it works the opposite way (unless I point to the exact place supporting my assertion, presumably).
But sure, fine, I'll take your bait.
I only skimmed the document, so I can't point you to the best place where to look for it. But I can point you to page 31, paragraph 10A-69 which says the following: "When alignment is performed in a hanger, there is a possibility that the system will track false stars (ceiling lights, etc). To prevent this from happening, the INERTIAL ONLY mode is selected and enabled after completion of an alignment. After the airplane taxies into the open, ASTRO INERTIAL mode is selected and enabled". I'm pretty sure this supports my assertion.