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

theaviationgeekclub.com

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

#21

Post by dboreham »

cmiller1 wrote: post #9
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

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.

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.

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

#23

Post by chipsa »

eastbound wrote: post #10
darth_avocado wrote: post #2

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.

Is it true that military branches (navy, airforce) from around equator use a grid-square reference system for radars and have issues when going further north, while triangle-based reference systems are a really good model in polar countries that doesn’t scale well when going South? It’s a problem so predictable that I can’t believe I have been told the truth, and it’s impossible to find the right keywords to search t…

The military does use a grid square reference system, Military Grid Reference System (MGRS), and to resolve the issues when sufficiently far north, the grid squares stop being aligned with the latitudes and longitudes, but rather just sit lined up with the 0/90/270/180 longitudes, as a sort of circular cap cut out of grid paper. (Properly speaking, it's Universal Transverse Mercator (which is a series of 60 Mercator projections) between 80S and 84N, and Universal Polar Stereographic near the poles).

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

#25

Post by omginternets »

fidotron wrote: post #6
darth_avocado wrote: post #2

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.

The F22 had an unintentional problem of being unable to cross the international date line, which was discovered when attempting to fly from Hawaii to Japan. Given that it may very well be better to assume that anything untested doesn't work at all and to live within those restrictions.

Something about non-monotonic software clocks?

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

#26

Post by [deleted] »

dboreham wrote: post #21
cmiller1 wrote: 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.

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.

[deleted]

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

#27

Post by davidw »

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

I'm not much into planes, in particular, but that museum is really cool.

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

#28

Post by [deleted] »

blackhaz wrote: post #20
malfist wrote: post #15

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.

[deleted]

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

#29

Post by thsksbd »

blackhaz wrote: post #20
malfist wrote: post #15

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.

The hardest part would be doing the image recognition, but that wouldn't be that bad since the position (and therefore expected picture) is already known, a priori, to a good accuracy.

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

#30

Post by Ductapemaster »

malfist wrote: post #15

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…

What software do you use to accomplish this?
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