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

Post by seryoiupfurds » Mon, Sep 25, 2023, 11:49 PM UTC

mk_stjames wrote: post #86

freyfogle wrote: post #53

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…

Interesting, is the ring road around Tavuki Island THE only road that falls on the anti-meridian, at all? A quick look along the line and it looks like it. It's wild that on google maps, even dropping a pin on the Tavuki road and trying to drag it across the line, it just stops, hitting this invisible wall. Something about this experience makes me want to go there....

Post by numpad0 » Mon, Sep 25, 2023, 11:52 PM UTC

porphyra wrote: post #48

jpm_sd wrote: post #43

Earlier quoted context omitted.

Probably by flying above most of the atmosphere.

That makes sense. What kind of sensor does it use to track the stars though? Stars are very dim.

Post by krisoft » Mon, Sep 25, 2023, 11:56 PM UTC

PaulHoule wrote: post #63

_moof wrote: post #35

Earlier quoted context omitted.

The International Date Line and the 180-degree line of longitude have bitten a _lot_ of folks who don't think to test at the boundaries.

I was working on a program that sales managers would use to divide sales territories up between salespeople and one feature was the ability to select all territories a certain distance from a point and using the most simplistic algorithm the code would crash if the circle crosses the 180 line so we had to use a somewhat more complicated algorithm than we first thought for this, even though all of the U.S. is one one…

Post by Arainach » Tue, Sep 26, 2023, 12:00 AM UTC

influx wrote: post #81

cushychicken wrote: post #4

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 another one in the Museum of Flight in Seattle.

Post by hutzlibu » Tue, Sep 26, 2023, 12:03 AM UTC

ComputerGuru wrote: post #96

hutzlibu wrote: post #88

Earlier quoted context omitted.

Well, good point, but every moment in history had its fixed south and north stars, you could find easily, if you were familiar with the sky. Which everyone was back then. As well as some animals, who also use the stars for navigation.

There’s no good reason to assume that in the absence of an extremely bright star that happens to be north-aligned that a culture navigated the stars with a north-anchored reference ;)