Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

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

theaviationgeekclub.com

Post reply on HN
Print view View original

301–310 of 358 posts

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

#301

Post by grotorea »

wiz21c wrote: post #296

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, myster…

I think we all know that in casual use nation, state, country and nation-state are all synonymous.

Or if you'd prefer, the WW2 interpretation of air warfare probably leans towards treating the entire populace as hostile.

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

#302

Post by alexnewman »

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.

That’s what I thought as well but his articles address those concerns. Very good read if you didn’t read them

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

#303

Post by blincoln »

helpfulContrib wrote: post #256
jonathankoren wrote: post #237

Earlier quoted context omitted.

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…

>EMPs are a fantasy. The Defense Department doesn't agree with you one bit. Russia is the worlds leader in Non-Nuclear EMP/RFW systems: https://apps.dtic.mil/sti/trecms/pdf/AD1124730.pdf Non-nuclear EMP weapons are a thing.

"unique radio-electronic weapons based on new physical principles" sounds an awful lot like the breathless tales of secret Russian Tesla death rays that have been circulating since the 80s, if not earlier.

If Russia could "neutralize entire armies with just one short electromagnetic impulse", or even just "disable missile warheads and onboard aircraft electronics miles away", don't you think they'd be using that capability against Ukraine?

The author of that paper was obsessed with the idea of EMP weapons,[1] so I'd take it with an entire shaker full of salt unless you can find solid supporting evidence elsewhere.

[1] https://www.legacy.com/us/obituaries/washingtontimes/name/pe...

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

#304

Post by 2rsf »

jaybo_nomad wrote: post #195

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…

> For reasons I still can't fathom, a contractor for the Israeli military purchased many copies

The Arrow 3 missile uses a star tracker, maybe previous generations or other missiles used those as well.

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

#305

Post by libertyhouse »

jollyllama wrote: post #297
dboreham wrote: post #21

Earlier quoted context omitted.

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.

Not sure you are were trying to be serious or not, but the DEF-H was one of the defensive systems used to jam surface to air threats. The system had two "modules" with one in the left and one in the right chine.

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

#306

Post by 2rsf »

robbs wrote: post #295
titzer wrote: post #209

Earlier quoted context omitted.

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".

And even they make mistakes, software contains much more moving parts than hardware.

https://space.stackexchange.com/questions/37110/what-was-the...

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

#307

Post by 2rsf »

Full_Clark wrote: post #228
missedthecue wrote: post #109

Earlier 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…

The guidance systems had to account for local variations in gravity as the missile flew to its target. One of the reasons ballistic missile accuracy improved so much was that measurements and mapping of these local anomalies improved so much. Most are due to magma reservoirs or large mineral deposits. Some are well-known in their effect, but their specific cause is still unknown: https://eos.org/science-updates/seism…

That's for Inertial Navigation Systems, they measure acceleration and from that integrate your position.

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

#308

Post by 2rsf »

dredmorbius wrote: post #300
KineticLensman wrote: post #290

Earlier quoted context omitted.

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?

Based on pictures the CEP should be very small, centimeters maybe. This missile doesn't explode, instead it send 6 blades at the target. Pictures show direct hits.

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

#309

Post by grotorea »

Synaesthesia wrote: post #177

It 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.

I partly feel that the real reason it was a waste of money is that after it was finished, the country was too nervous due to Francis Gary Powers' U-2 being shot down to actually try using the SR-71 for its original purpose of flying over the Soviet Union, meaning they were using a very expensive plane for the missions.

Ironically enough, the much cheaper but less impressive U-2 is still in use today.

Post reply on HN