241–250 of 358 posts
The crazy thing about this system too is that, like everything on the SR-71, it was done on a shoestring budget (relatively) and crazy fast. So a navigation system like this was done as a necessary workaround to traditional navigation of the time.
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Compared to the rest of the engineering, I don’t think the computation is all that hard. It doesn’t need to be that fast since you only need to do a correction maybe every 10-20 minutes or so. The math was innovative in that they invented the Kalman filter for these types of computations. You pick your star such that it’s by far the brightest one in its neighborhood. So the image processing is just finding the bright…
Did the units in question even have pixels?
The Trident I used a Vidicon tube (what they used to use for TV cameras before CCDs were invented) [2] The Trident approach was to shoot a single star once in the flight.
The Trident II uses a CCD. The first version of the guidance system for that missile (The Draper Mark 6) used a 90x90 CCD [3]. That has been replaced with the Mark 6 Mod 1, which they say has increased resolution but they don't give a figure [4]
[1] NAS-14V2 ANS System Manual, Page 10A-49 https://airandspace.si.edu/webimages/collections/full/NAS-14...
[2] Inventing Accuracy, Page 290
[3] The Trident II (Mk-6) Guidance System, Page 1460 https://sci-hub.se/https://doi.org/10.2514/6.1991-2761
[4] Modifying the MARK 6 Guidance System Part 1 https://www.electronicdesign.com/home/article/21201730/modif...
You 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
There's an A-12 Blackbird at the San Diego Air & Space Museum in Balboa Park. Not an expert, but my understanding is the A-12 was basically the beta version that eventually lead to the SR-71. https://sandiegoairandspace.org/collection/item/lockheed-a-1...
There were supposed to be more variants, even tactical bombers but military politics and budget constraints and yadda yadda yadda.
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To be fair, you can do a lot when you throw a near endless supply of money at things. Definitely impressive though.
To get great software, you need a small team and give them extremely clear requirements of what it should do with an assload of extremely clear testcases.
When I first heard of astro-nav (for missiles) I thought it was so future sounding, like star trek. But now that I do astrophotography regularly it's just another tool that I use. It's super simple to do, I can take a photo of the night sky, and if I know the focal length and pixel size of my camera I can figure out exactly where my telescope is pointed in seconds, with an accuracy 2.5 arcseconds. You can even do it…
OK. Now please do the same with a Z-80 class CPU.
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For reasons I still can't fathom, a contractor for the Israeli military purchased many copies, apparently so their tanks and troops could remain oriented after all other electronic systems failed. Possibly in case of EMP attack?
EMPs are a fantasy. Absolutely and unreservedly a complete fantasy. ZERO have ever been tested, and there’s literally a better use for a nuclear warhead. Not only is it a a completely hypothetical attack, it would look identical to a normal nuclear ICBM attack, and absolutely would result in a traditional retaliatory attack. Why would anyone trade an EMP for all their cities? Literally doesn’t make sense. No one in t…
Wait what? There were specific nuclear EMP tests. And sure, in any realistic nuclear war scenario EMP is just an unpredictable byproduct like your link says, but that doesn't make it fantasy I believe?
Semi-related tangent: During the early 1990's I developed a star chart and ephemeris for the (momentarily) fashionable Windows Mobile platform called "Pocket Stars" that calculated one's geographical position from three or more sextant observations, mainly as backup for offshore sailors should their GPS system fail. For reasons I still can't fathom, a contractor for the Israeli military purchased many copies, apparen…
I wasn’t around for the 90s edition of windows phone (at least not enough to understand any of the tech) — i guess for lack of a camera and compass +gyro, would the observations be done out of band and just put into a form?
I was ... and worked on mobile apps and windows CE. I proposed an app like Tinder back then, but management decided there was no market for it.
I guess execution is everything.
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EMPs are a fantasy. Absolutely and unreservedly a complete fantasy. ZERO have ever been tested, and there’s literally a better use for a nuclear warhead. Not only is it a a completely hypothetical attack, it would look identical to a normal nuclear ICBM attack, and absolutely would result in a traditional retaliatory attack. Why would anyone trade an EMP for all their cities? Literally doesn’t make sense. No one in t…
>ZERO have ever been tested Wait what? There were specific nuclear EMP tests. And sure, in any realistic nuclear war scenario EMP is just an unpredictable byproduct like your link says, but that doesn't make it fantasy I believe?
In this case, I went to Duxford a day before this was posted on HN. I visited the #962 SR-71 in person. At the day this was posted, I also discussed about the SR-71 with a neighbour and how it was stationed at RAF Mildenhall here in the UK.
With that said, SR-71 is such an awesome machine, it contains so many breakthroughs and innovations. It was so advanced that even the tooling, methods, paint and even fuel had to be invented specifically for this aircraft.
Earlier quoted context omitted.
For reasons I still can't fathom, a contractor for the Israeli military purchased many copies, apparently so their tanks and troops could remain oriented after all other electronic systems failed. Possibly in case of EMP attack?
EMPs are a fantasy. Absolutely and unreservedly a complete fantasy. ZERO have ever been tested, and there’s literally a better use for a nuclear warhead. Not only is it a a completely hypothetical attack, it would look identical to a normal nuclear ICBM attack, and absolutely would result in a traditional retaliatory attack. Why would anyone trade an EMP for all their cities? Literally doesn’t make sense. No one in t…