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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

#341

Post by mgsouth »

GolfPopper wrote: post #210
ecommerceguy wrote: post #140

Earlier quoted context omitted.

Theres one at Strategic Air Command Museum in Nebraska. https://www.sacmuseum.org/what-to-see/aircraft/sr-71a-blackb...

I've visited that one. As a someone who grew up during the Cold War, the idea that we've got these once super-secret military aircraft just sitting where any old tourist can walk up and take picture from a few feet away always generates some cognitive dissonance.

In Palmdale California, at the corner of 25th St E & E Palmdale Ave [1], there's what is essentially a parking lot with a chain link fence around it. Sitting there are a SR-71, a A-12, a D-21 (supersonic recon drone originally launched from A-12 variant), and a U-2. You can just sit there and take all the pictures you want.

[1] https://www.google.com/maps/@34.6026576,-118.0860601,117m/da...

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

#342

Post by defrost »

doctor_eval wrote: post #255
defrost wrote: post #134

Earlier quoted context omitted.

> to clarify it’s not the international date line but the latitude? Longitude. The vertical one that goes from negative to positive at 180 Longitude East or West. Maybe you should get a map out and have a look.

Right. I do know the difference between latitude and longitude; I just mistyped. I was working in Samoa when they changed the date to align with NZ time, so am quite familiar with the region.

No drama, I'm more and more prone to using the wrong word, adding a 'not', and totally screwing up comments now that I've passed 60.

I mainly intended to clarify for any readers rather than castigate you, and after the initial remark about time zone I got a little blunt.

( FWIW I made several mistakes in this comment and had to edit twice )

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

#343

Post by havercosine »

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...

The most badass story related to 'using basic tools and a steady hand in a pinch' is Buzz Aldrin pulling out a sextant and sliderule to do some calculations in Gemini XII. The description in the article reads "Aldrin pulled out a sextant and his slide rule and put his MIT doctoral research to work."

More details on the link here: https://www.nasa.gov/feature/gemini-xii-crew-masters-the-cha...

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

#344

Post by ezconnect »

frud wrote: post #317
ezconnect wrote: post #135

Earlier quoted context omitted.

They also need an initial fix before take off and that could be day or night depending on the mission.

I think that in order to calculate your latitude and longitude position using what amount to high-tech sextant readings you have to know your local down vector to a high degree of accuracy. That is, the system judges the position of the Blackbird by comparing its local down vector with the angles to the star sightings. If the down vector measurement is off by an arcsecond, the measured latitude and longitude position…

Can it just look at the front and back horizon to estimate the local down vector?

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

#345

Post by tester756 »

drt5b7j wrote: post #339
tester756 wrote: post #327

Earlier quoted context omitted.

What's ur definition of "engineering" then

If you don't know what engineering means, why not check out Wikipedia? https://en.wikipedia.org/wiki/Engineering

I have my interpretation of "engineering" based on my degree, wiki's definition and discussions.

But people have various interpretations of that, especially those who try to act as if for some weird reasons software was not engineering and that's what I'm asking for.

Why so snarky?

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

#347

Post by frud »

ezconnect wrote: post #344
frud wrote: post #317

Earlier quoted context omitted.

I think that in order to calculate your latitude and longitude position using what amount to high-tech sextant readings you have to know your local down vector to a high degree of accuracy. That is, the system judges the position of the Blackbird by comparing its local down vector with the angles to the star sightings. If the down vector measurement is off by an arcsecond, the measured latitude and longitude position…

Can it just look at the front and back horizon to estimate the local down vector?

If you can measure the front and back horizon accurately you can measure the left and right horizons too, and that will give you an accurate down vector.

But I don't think it's possible to measure a horizon that accurately. There are temperature and pressure dependent atmospheric effects at low angles that effect how light refracts and curves through the atmosphere, and these effects will have to be compensated for to measure the angle accurately. Additionally, there are mountains and valleys to compensate for.

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

#348

Post by nojvek »

Ancapistani wrote: post #322
nojvek wrote: post #318

Earlier quoted context omitted.

We will have countries against each other fighting for their borders but world war is v unlikely in our lifetime. We love our cheap goods, cheap-ish energy and ability to change presidents and prime ministers. Yes China, North Korea and Russia banding against the rest of the world is a real threat but China has shown it is selfish too and cares more about its economy.

> We love our cheap goods, cheap-ish energy and ability to change presidents and prime ministers. I'm not saying I don't agree, but this is almost identical to arguments made prior to WW1.

No mutually assured destruction back then.

WW1 was a pretty inefficient war, WW2 got better weapons and communication infra, but modern war fare is seriously destructive.

Intercontinental missiles fired from stealth submarines with nuclear payloads that break apart in air into 20 little payloads that then destroy an entire city 1000s of kms.

Modern warfare doesn’t need armies of millions of men. Whoever can best see their enemy via satellites and oceanic array, direct the most destructive energy using missiles and drones decapitates their enemy.

One nuclear warhead possesses multiple times the energy spent on both world wars combined.

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

#349

Post by TMWNN »

elzbardico wrote: post #61
jacurtis wrote: post #32

> the flight plan was recorded on a punched tape that told the aircraft where to go, when to turn, and when to turn the sensors on and off. This is equally fascinating to me. Before each flight, someone had to generate a flight plan and punch it onto a physical tape, then load it into the plan. T No mid-flight "re-calculating route" if stuff goes wrong. One of the most interesting and under-appreciated aspects of ear…

America was not critical defeating Germany. The soviets did this one.

Hopefully, one of the good things that will come out of the Russia-Ukraine War is the eternal shattering of the smug "Ha ha Americans, everyone knows that it's the Soviets that beat the Nazis" notion. Setting aside the total complicity of the Soviets in helping the Germans to dismember Poland in 1939 and attack themselves in 1941, without massive American and British aid Moscow would have fallen in 1941 and the Soviets would have sued for peace in 1942.

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

#350

Post by chipsa »

freyfogle wrote: post #59
chipsa wrote: post #23

Earlier quoted context omitted.

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…

Best bit of weirdness about UTM is the exception made for zone 32V so that Norway fits into a single zone, see: https://en.osm.town/@opencage/109694749637123570

There's a similar weirdness for Svalbard, which results in 32/34/36X not existing.
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