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

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

#271

Post by hoseja »

KMag wrote: post #239
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…

I interned at the Charles Stark Draper Laboratory 20+ years ago. One of the guys was telling me at lunch about his work that day. He had to run some simulations to tell the Navy if their Trident guidance system needed to be sent back for re-manufacturing after a forklift operator dropped it. My understanding is that the handling crate had some kind of integral rough handling detector. (I presume calibrated weights on…

An enthusiastic guy on youtube was trying to drop an egg from the edge of space and got shutdown for developing a terminal guidance system. So it's not so much about the only use being weapons, it's that weapons have state monopoly on precision guidance.

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

#272

Post by Sharlin »

KaiserPro wrote: post #266
hbarka wrote: post #232

Off tangent here but I thought I'd mention that yesterday a replica of a traditional Polynesian ocean-going canoe, the Hokulea, sailed into San Francisco, navigated with non-instrument methods including star observations. https://www.sfchronicle.com/bayarea/article/hokulea-polynesi... The Hokulea's maiden voyage was in 1975 and since then it has made global voyages to demonstrate and preserve ancient Polynesian wayfi…

Polynesian navigation is Wild. I think its well known that it almost died out, as its something that needs ideally to be taught in the (sea) field. However there are now people in their 30s who can navigate by the stars, sound, wave shape and pattern, cloud layout and birds https://manoa.hawaii.edu/exploringourfluidearth/physical/nav... Similarly there are people who can navigate the desert, even though the dunes are…

> Similarly there are people who can navigate the desert, even though the dunes are mostly ever shifting.

To be clear, most deserts don't feature dune seas at all, and even the Sahara is mostly rocky plateau, dune seas comprising about 10% of its surface area.

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

#273

Post by wnkrshm »

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…

Regarding your other comment: why wouldn't a high-altitude detonation, even outside the atmosphere cause an EMP? I feel like the gamma photons emitted in space will eventually hit the atmosphere and with that cause electrons to spiral along field lines. Isn't the question just one of intensity?

Or is it largely dependent on multi-photon interactions to impart enough impulse on the electrons?

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

#274

Post by drt5b7j »

jacquesm wrote: post #143
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…

It's not just analog tech: it's actual engineering. The hardware we have is amazing, most of our software royally sucks. But software done right is also most impressive.

Do you think the "software engineering" people are giving engineering a bad name?

"Christian scientists" are Christians who attach themselves to the word science because science has such a powerful reputation. In their case I'm not worried about their trickery because everyone recognizes this. Everyone knows that Christian scientists are not scientists.

With software engineering it's not as clear. It's possible to create software applying engineering principles, but that's not what 99%+ of what is called "software engineering" is. And because most people don't recognize this, I think eventually this might run off "engineering".

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

#275

Post by Sharlin »

jjoonathan wrote: post #52
mat_epice wrote: post #17

ICBMs have used celestial guidance since the 50s. https://airandspace.si.edu/collection-objects/snark-guidance...

No GPS in the apocalypse. Ring Laser Gyroscopes are another nifty nav tool in this space: https://en.wikipedia.org/wiki/Ring_laser_gyroscope#/media/Fi...

No GPS in the 50s either.

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

#276

Post by chipsa »

NamTaf wrote: post #187
spookie wrote: post #142

Earlier quoted context omitted.

The fuel doesn't ignite at "low" temperatures, one reason is because the whole airplane leaks fuel until it's at an high enough speed. At that point, maybe because of the surface temperature, or the forces it tackles at Mach 3+, the whole thing becomes airtight. At least, that's what I remember.

Yup, at Mach 3+ the fuselage expands so significantly that gaps need to exist when it’s stationary, otherwise it’d buckle. So the gaps mean it leaks fuel when stationary.

It's not supposed to leak. It just that the sealant to bridge the gaps wasn't perfect, so it'd get some leaks through the sealant.

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

#277

Post by taneq »

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.

The best software comes from a small team of top level devs who are also top level subject matter experts on the software’s domain. This doesn’t happen very often.

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

#278

Post by littlestymaar »

Modern IBCM also correct their trajectories this way: they don't need too much accuracy (because of the large blast radius of nuclear warheads) and they are hypersonic during re-entry which limits the possibilities, so they use inertial guidance, but to improve accuracy they correct the trajectory at the peak of the ballistic trajectory using the stars.

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

#279

Post by Steve44 »

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…

There is much of a Chevaline, an upgrade to Polaris, in the Museum of Berkshire Aviation [1] which is near Reading, about 50 miles west of London. They also have some of the navigation systems, such as gyroscopes you can get a good look at.

I find the level of engineering fascinating, it's not often you get to see such detail close up.

I took a few photos[2] when visited about 10 years ago. Being a small museum it's quitehiggledy-piggledy but they also have a range of unusual exhibits such as a model of the Miles M.52 and a real Fairey Jet Gyrodyne.

[1] https://museumofberkshireaviation.co.uk/html/exhibits/cheval...

[2] https://www.flickr.com/photos/stevecargill/albums/7217772030...

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

#280

Post by keepamovin »

keepamovin wrote: post #204
avs733 wrote: post #166

Earlier quoted context omitted.

As far as I’m aware test shots of both us Air Force and navy icbms off the west coast went to Kwajalein atoll. Some other interesting details… Naval icbms have star tracking for alignment and correction but land based ones do not. The reasoning is that they are all dead reckoning…which requires knowing the initial location. The silo doesn’t move, but the subs do. Their location is tracked with another inertial guidan…

So the confrontational is more because of the perceived shift to offensive ("unprovoked") first strike over "defensive" second strike, rather than any perceived loss of a deterrent second strike capability?

Just want to note that the front page top 10 - 15 the last 24 hours or so has been disproportionately full of US government and military related posts. Something must be coming, some big news. BOLO
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