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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

#291

Post by mauvehaus »

legitster wrote: post #243
jimt1234 wrote: post #103

Earlier quoted context omitted.

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...

The A-12 was the original single seat version developed for the CIA. But eventually the Air-Force was given all responsibility over the planes and they re-designated the plane and added a second seat to fit their pilot philosophy. There were supposed to be more variants, even tactical bombers but military politics and budget constraints and yadda yadda yadda.

The Air Force museum in Dayton has a YF-12, which was the prototype of the interceptor variant. It's readily distinguishable from the A-12 and SR-71 because the chines don't extend to the front of the nose. This so that the nose cone could be made of material that is transparent to radar.

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

#292

Post by orbital-decay »

jonathankoren wrote: post #258
irjustin wrote: post #248

Earlier quoted context omitted.

I wonder if the parent is talking about pure EMP without the nuke because those are pure fantasy. Kill all electronics w/o all the fallout.

No. That’s not what I mean. I’m talking about big boogeyman of an EMP attack that destroys the either the North American electrical grid and assorted electronics or merely all electronics in a city. There is no nonnuclear EMP weapon. Every proposed EMP attack is literally a hydrogen bomb delivered via an ICBM and detonated at extremely high altitude. That is the only way to deliver one to the proper place and the onl…

> Even then, the actual effect at ground level, is unpredictable because of simple shielding and atmospheric turbulence.

https://en.wikipedia.org/wiki/Soviet_Project_K_nuclear_tests

>EMP ran to thousands of amps, damaged at least 570 km of telephone lines, 1000 km of buried power lines, and caused the destruction of the Karaganda power plant.

A 300kt blast at 290km was able to induce 1.5 to 4.5kA in the unshielded power line buried underground at 2m, over the area hundreds of kilometers across. Imagine what it could do to the areas that are a bit more populated than Kazakh steppes in 60's.

So yeah, while the nuclear EMP is probably not going to be used as a primary weapon in a global nuclear strike as you said, it's not a huge stretch for one of the warheads to be dedicated for the EMP over some large but less important area, not necessarily as a decapitating strike, so preparing for it makes sense. Besides, there would be at least local EMPs in the area after the "ordinary" nuclear strike, which can be really disabling if unprepared for.

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

#293

Post by krisoft »

jonathankoren wrote: post #258
irjustin wrote: post #248

Earlier quoted context omitted.

I wonder if the parent is talking about pure EMP without the nuke because those are pure fantasy. Kill all electronics w/o all the fallout.

No. That’s not what I mean. I’m talking about big boogeyman of an EMP attack that destroys the either the North American electrical grid and assorted electronics or merely all electronics in a city. There is no nonnuclear EMP weapon. Every proposed EMP attack is literally a hydrogen bomb delivered via an ICBM and detonated at extremely high altitude. That is the only way to deliver one to the proper place and the onl…

Yeah. So you are probably correct that it is unlikely that someone only sends a single warhead to do an EMP attack. What I don't understand is why you would think that it is unlikely that they send their whole volley, and some warheads are programmed to hit targets while some others are programmed to detonate to maximise EMP damage.

Sure there is MAD, but if you are a military leader would you like to hang your hat entirely on that? After armageddon when you climb out of your bunker would you like to be the one who still has tanks to command, or the one who can't command anyone because all your radios have fried?

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

#294

Post by hammock »

13of40 wrote: 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…

>cylinders of ground quartz crystal, so flat ... their navigation worked by what you'd expect: Looking at the stars and comparing them to a super accurate timestamp, plus some core memory logarithmic tables or whatever

I didn't expect that, can someone explain? Sounds like some kind of dead reckoning system, I don't get why you need flat quartz discs to read the stars though?

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

#295

Post by robbs »

titzer wrote: post #209
PNewling wrote: post #193

Earlier quoted context omitted.

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.

It doesn't have to be a small team. See "They Write The Right Stuff".

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

#296

Post by wiz21c »

FTA:

> to collect information about hostile and potentially hostile nations using cameras and sensors.

I will sound very picky but, well, I'm pretty sure a rather big part of all civilians of all nations are not hostile. So I disagree with the wording. A nation is not hostile. A fraction of it is.

This was tuesday's afternoon rant. Thanks for clapping.

But well, the SR71 was really impressing when I was a kid, mysterious too.

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

#297

Post by jollyllama »

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.

The DEF-H module contains the Diesel Exhaust Fluid for the truck.

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

#298

Post by alexnewman »

At planet.com we had star scanner and we also calibrated our camera with the moon. When you traverse the horizon in 15 minutes , I think about 30k mph from what I remember , knowing exactly where you are is tough. Knowing where you point the camera is even harder. And no gps didn’t really work well up there

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

#299

Post by grotorea »

jonathankoren wrote: post #254
sonthonax wrote: post #252

Earlier quoted context omitted.

> Why would anyone trade an EMP for all their cities? ICMBs were a theoretical threat. Cold War doctrine had a more realistic (and less apocalyptic) WWIII that would be fought by tactical nukes and tanks through Europe.

Bullshit. They’ve been demonstrated. Repeatedly, and publicly. That’s the whole point of having them. Also, there is no difference between a tactical and strategic nuke from an escalatory perspective. Once the genie is out, it’s out.

In that case, why both sides of the Cold War spent fortunes on conventional forces along the Iron Curtain?

Like yes it is playing with (nuclear) fire, and maybe they were wrong, but there plenty of professionals who, maybe biased by their positions, who felt the need to get ready for limited nuclear war. And I'm not really convinced either side would want to risk destroying human civilization over Frankfurt.

> Also, there is no difference between a tactical and strategic nuke from an escalatory perspective. Once the genie is out, it’s out.

I mean, why? Why shouldn't tactical and strategic be separate steps on the ladder?

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

#300

Post by dredmorbius »

KineticLensman wrote: post #290
dredmorbius wrote: post #212

Earlier quoted context omitted.

CEP: Circular error of probable or probability. The radius of a circle within which 50% of rounds will be found. For the V-2 rocket this was 4.5 km. For the Minuteman III missile, 240m. Blast effects decrease with the cube of the radius, so a more accurate weapon means a smaller effective warhead. The "Flying Ginsu" AGM-114 Hellfire missile has a CEP of 5 meters or less, and uses blades rather than explosives to mini…

That would be the AGM-114R9X. Most hellfire variants use explosive warheads.

Thanks. I was going off Wikipedia's designation, and don't know the full list of variants and their designations.

Would you know CEP for the 9X variant?

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