The SR-71 Blackbird Astro-Nav System worked by tracking the stars
theaviationgeekclub.com
theaviationgeekclub.com
I was ... and worked on mobile apps and windows CE. I proposed an app like Tinder back then, but management decided there was no market for it.
I guess execution is everything.
Possibly in case of EMP attack?
All that said, GPS denial is a very real thing, and has been repeatedly demonstrated in an operational context. It’s relatively trivial to do. You just need a regular ground based antenna, and not a particular strong transmitter because satellite signals are weak. Just broadcast a different timing signal and voilà! You now tricked someone into thinking they’re 50 miles away from where they really are.
https://medium.com/war-is-boring/the-overrated-threat-from-e...
https://www.c4isrnet.com/opinion/2022/07/22/why-isnt-russia-...
Wait what? There were specific nuclear EMP tests. And sure, in any realistic nuclear war scenario EMP is just an unpredictable byproduct like your link says, but that doesn't make it fantasy I believe?
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 only way to deliver the required energy. That’s just the physics. Even then, the actual effect at ground level, is unpredictable because of simple shielding and atmospheric turbulence. But the undetermined effects aren’t what makes an EMP fantastical. It’s fact that it’s delivered by an ICBM!
The premise of an EMP attack is that somehow the attacker could surprise their enemy and land a catastrophic knockout blow near instantaneously (where “instantaneous” is defined as “between 10 and 30 minutes” (i.e. the flight time of either an SLBM or ICBM)) with little to no retaliation. A Launch on Warning policy (i.e. launch a retaliatory strike when an incoming missile is detected in the air) along with ground and space based surveillance systems makes attempting to execute an EMP attack suicidal.
Missile launch detection systems have been operationally deployed and maintained since the 1960s. They work. Launch on Warning has been the policy of the United States since the 1960s. Implicit in a LOW policy is that the retaliatory strike order is given in minutes from a detected launch. This means the retaliatory nuclear weapons are already sent on their irreversible course before any incoming detonation occurs. This is the defense posture a hypothetical EMP attacker is lobbing an ICBM into. This isn't fantasy. This isn't just math. It’s the explicit nuclear posture of the United States for the past 60 years. It’s what makes Mutually Assured Destruction (MAD) work, and arguably has maintained peace between nuclear states for 70 years.
If an attacker has decided to launch a nuclear laden ICBM they just started a full on nuclear exchange, because that’s the response. No one is waiting to see where it goes. It’s “The missiles are flying. Hallelujah, Hallelujah.” Now. Given that you’re in an inevitable nuclear exchange, is it reasonable to waste a nuke on a roll of the dice on whether it actually do anything when you could actually blow something up? Nay! Knowing that you are being blown up?
On a related note, this is the exact situation why the proposed Prompt Global Strike weapon is suicidal. An ICBM armed with high explosives, looks exactly like an ICBM armed with nuke. Similarly, a kinetic energy hypersonic glide vehicle is not suicidal specifically because it doesn’t travel on a ballistic arc.
False. There are non-Nuclear EMP's, and the USA even has a bit of experience with the Russian variants ..
Or is it largely dependent on multi-photon interactions to impart enough impulse on the electrons?
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.
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?
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.
Also, there is no difference between a tactical and strategic nuke from an escalatory perspective. Once the genie is out, it’s out.
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?
Not if you happened to be the relevant parts of Europe!
― Albert Einstein
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.
I'm not saying I don't agree, but this is almost identical to arguments made prior to WW1.
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.
I really want to believe that. But the same logic did not stop the first world war.
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.
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...
No, and that's entirely the point.
Their non-use of their advanced weapons systems is as equally interesting a subject as their forward-deployment of expendable, less advanced systems.
The Russian military certainly have their inefficiencies - as all modern militaries do, including "our own" - but they also have capabilities that are going to be more important to use against NATO/USA, than Ukraine.
The Russian mindset appears to support the idea that World War Three is well and truly under way and has been since the West illegally invaded Iraq, in 2003. Ukraine is merely the latest in this conflagration that has been rendering 'lesser nations' asunder, for two decades already. The whole world has been watching not only American/NATO, but also Russian doctrine in play for decades.
So I guess the doctrine is, don't play your best hand first .. and reserve your big muscle for when you fight big muscle.
NATO is adding its muscle to Ukraine, no question. But I wouldn't expect to see Russian - or NATO - advanced weapons systems in use until there is actually direct, open conflict between Russia and NATO.
Only then would non-nuclear EMP's, and indeed tactical ("micro") nukes, and other such more 'advanced' weaponry end up on the battlefield, if there is even one after the first few hours of 'real war'.
Now they're buying equipment from Iran (!?) and North Korea.
Russia, in their deep USA envy thought they'd have their own Shock and Awe! 3 day SMO.
Instead they overestimated themselves, and massively underestimated Ukraine.
The cupboard is empty. The only thing they have left is nuclear weapons, which they're quite rightly terrified of using. All that remains now is a long slow and grinding defeat as Putin expends every available Russian male in his desperate attempt to remain in power and not back down.
I don't believe that's the case. Russian military doctrine has always been to reserve the best systems for the end-game, and front 'fodder' in the beginning stages of things.
I see Russia's war theatre manifest also in Syria, where the very same tactics are utilized to suppress the field.
"Shock and Awe" is a US doctrine. Russian is more "Shake and Hold".
"Massively overestimating themselves/underestimating themselves", is very difficult to contextualize, if you don't actually speak Russian.
>The cupboard is empty.
I'm sorry, I really don't agree. You might want to take a deeper look:
https://www.cna.org/reports/2021/10/Russian-Military%20-Stra...
You must, of course, steel yourself for some whiplash. The world is not entirely as it "seems".
> I don't believe that's the case. Russian military doctrine has always been to reserve the best systems for the end-game, and front 'fodder' in the beginning stages of things.
This still doesn't explain the BMP-T's, the T90's and S300's that are deployed to Ukraine and destroyed in Ukraine.
>>The cupboard is empty.
> I'm sorry, I really don't agree. You might want to take a deeper look: > https://www.cna.org/reports/2021/10/Russian-Military%20-Stra... > You must, of course, steel yourself for some whiplash. The world is not entirely as it "seems".
If the cupboard isn't empty then why are there ~80 smoldering T62's in Ukraine.
https://slate.com/technology/2015/10/u-s-naval-academy-reins...
The Arrow 3 missile uses a star tracker, maybe previous generations or other missiles used those as well.
j/k; I'm [almost] not ashamed to admit that I also developed for WinMo once upon a time.
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 but the coast guard would never shoo them away -- they wanted the Soviets to know just how accurate these missiles were. And they were accurate.
It blows my mind what was possible with analog tech.
I love analog tech, simple but generally insanely robust when done right.
https://space.stackexchange.com/questions/37110/what-was-the...
"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".
Not to be confused with Christianity and science, Christians in Science, Christians in science and technology, or Scientology.
Christian Science is a set of beliefs and practices which are associated with members of the Church of Christ, Scientist. Adherents are commonly known as Christian Scientists or students of Christian Science, and the church is sometimes informally known as the Christian Science church. It was founded in 19th-century New England by Mary Baker Eddy, . . .
Software development usually seems far more controlled than that was.
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?
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 guidance system but that adds error, so they use the star tracking.
Overall, the inertial navigation systems in modern icbms are not the limited in accuracy.
My favorite…there was a lot of pushback inside the us military on investing in increasing the accuracy of naval ICBMs. Doing so was seen as communicating/implying a shift in strategic goal from targeting cities (lower required accuracy) to targeting hardened facilities (higher required accuracy). That was seen as confrontational because sun based nuclear weapons had been generally treated as a second strike capability, but the primary reason to have the ability to target hardened facilities was for a first strike
The book "Inventing Accuracy" covers this in detail. Fascinating historical perspective.
The most interesting boring book I’ve ever read.
https://missilethreat.csis.org/us-navy-test-fires-trident-ii...
https://www.thedrive.com/the-war-zone/34043/france-just-test...
Generally the logic is don’t launch on trajectories over land unless you have to. I believe all of the land based is ICBMs are still tested from vandenberg on the (most beautiful section of) California coast near Lompoc for the same reason. Vandenberg doesn’t have any deployed ICBMs, they all fly to kwaj for testing. Same reason nasa/spacex/seemingly everyone but China make it a goal to not have launches go over populated areas.
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/seismologists-search-for-the...
I’m imaging most on here have read some/all of the secret history of Silicon Valley posts, but if you haven’t they are great
https://navsource.org/archives/08/PolarisHistoryGEX1.htm (see bottom / appendix for examples of Polaris-era INS)
Given the CEP they were aiming for, and amount of time they had to fiddle with them, I'd guess they started very carefully with the physical precision of components.
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 minimise any unintended casualties.
But then withdrawn from service due to treaty, because with that accuracy, first striking your target's silos and hardened facilities starts to be a viable option.
Sometimes you can be too accurate.
Also, related, the W76-1/Mk4A height-adjusting fuze solved this this in a different way, by recognizing that there's a 3D kill-volume (above and around the target) rather than a 2D kill circle.
Consequently, if you aim beyond the target and have your warhead measure actual height vs expected once on a ballistic trajectory, you can adjust the fuzing height to detonate within the volume, even if you overshot the target. See figures 2 and 3. https://thebulletin.org/2017/03/how-us-nuclear-force-moderni...
Un/fortunately, this puts us back into viable first-strike territory.
Would you know CEP for the 9X variant?
<https://www.kabulpress.org/article89242.html>
<https://metinmediamath.wordpress.com/2013/10/10/missile-accu...>
I was told that once above most of the atmosphere, the MIRV bus guidance unit pops the lens off and takes a snapshot of the stars. The MIRV bus is rotating at that point, so the telescope scans a good section of the sky, but it takes a snapshot at a very specific time and is only interested in a rather small patch of sky. It compares what it sees with a stored copy of what it should see, and uses that to re-calibrate the inertial measurement unit.
The way it was described to me was that one rotation checked the star field, the IMU was re-calibrated, the very next rotation was used to double-check the IMU calibration, and right after that, the MIRV bus started popping off the individual warheads. It seems strange to me that they would use such a short observation window to re-calibrate the IMU, rather than having a long period of continuous re-calibration. It's also highly possible that the guy explaining it to me was giving intentional misinformation to avoid accidentally disclosing TS/SCI to a non-cleared intern.
The nitty-gritty of guidance is fascinating. It's unfortunate that the main use cases for ultra-accurate guidance are in weapons.
There was a pendulous integrating gyroscopic accelerometer from the Apollo IMU sitting in a glass case in the lab... a shame given how few people were allowed into the lab.
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...
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?
[it] was so powerful that it could see the stars even in daylight
[1] http://hyperphysics.phy-astr.gsu.edu/hbase/atmos/blusky.html
There are actually some interesting patents related to the star sensor in the devices, particularly related sky background gradients. Northrop’s patents are more interesting than Lockheed’s, IMHO. In all cases the patents mention using an IR-pass filter to improve contrast.
The sensor is essentially an analog lock-in/synchronous detector with a rotating shutter and a wedge prism that nutates the star field about the boresight. the patented component in most cases is the shutter (there are different patterns, and Northrop came up with some clever designs).
You end up with a frequency modulated signal from the photomultiplier tube (carrier is from the shutter, modulation frequency the difference between the prism and shutter).
By measuring the phase and magnitude of the modulated signal, you can steer the telescope onto the star, and the “coding gain” from the lock-in is substantial.
Edit, previous comments:
For context: learning about carriers, modulation frequency in relation to audio synthesis [acknowledging there is more than one type of 'FM' in relation to audio but nonetheless similar]).
It seems to me that there's an interesting problem that the Blackbird goes so fast that its down vector changes dramatically over the course of a typical flight, so I'm wondering how it accurately updates its down vector reference. Jets can go through arbitrary and wobbly 3-d trajectories, accelerating in any direction, so it can't be a simple measurement of gravity. It would have to be a accelerometer combined with inertial and gyro and elevation readings all summed up.
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.
The Astro-Nav System didn't work only at cruising altitude, it tracked stars even when the SR-71 was on the ground. [1]
[1] https://airandspace.si.edu/webimages/collections/full/NAS-14...
>
> [1] https://airandspace.si.edu/webimages/collections/full/NAS-14...
I don't necessarily doubt you, but linking to a 76-page PDF without any indication of where the reader is supposed to find support for your claims is not nearly as convincing as you think it is.
It's funny you say that, because based on almost all the assertions you read here on HN which are taken for granted without any links to support them, you'd think linking to an authoritative PDF would be more convincing than if I hadn't linked to it. But based on your comment it seems like it works the opposite way (unless I point to the exact place supporting my assertion, presumably).
But sure, fine, I'll take your bait.
I only skimmed the document, so I can't point you to the best place where to look for it. But I can point you to page 31, paragraph 10A-69 which says the following: "When alignment is performed in a hanger, there is a possibility that the system will track false stars (ceiling lights, etc). To prevent this from happening, the INERTIAL ONLY mode is selected and enabled after completion of an alignment. After the airplane taxies into the open, ASTRO INERTIAL mode is selected and enabled". I'm pretty sure this supports my assertion.
Not at all, your comment was strictly better for including that link, thanks for including it. It was neat to briefly skim the PDF, even if I don't have time to read the 76 pages of technical documentation.
> I only skimmed the document, so I can't point you to the best place where to look for it. But I can point you to page 31, paragraph 10A-69 which says the following: "When alignment is performed in a hanger, there is a possibility that the system will track false stars (ceiling lights, etc). To prevent this from happening, the INERTIAL ONLY mode is selected and enabled after completion of an alignment. After the airplane taxies into the open, ASTRO INERTIAL mode is selected and enabled". I'm pretty sure this supports my assertion.
Maybe. But that whole paragraph is hard to understand. How were they doing alignment in a hangar to start with, were these roofless hangars?
I don't think so.
You can read more about alignment in page 7, paragraph 10A-23 and the following pages. It'd usually involve using test equipment and manually inputting the current coordinates (e.g. heading, position, altitude, date/time, ...) into the system, from what I understand.
Regardless, the paragraph I mentioned in my previous comment clearly instructs to enable ASTRO mode after the alignment is completed and the airplane is taxiing in the open. It also mentions that in ASTRO mode, the system can confuse the ceiling lights of the hangar for stars (hence why it needs to be disabled inside the hangar), which means that ASTRO mode does track stars on the ground.
(which is also why the sky is blue-- or really UV, if we could see it)
The software for plate solving is pretty good. I've had some fun taking movie screenshots and figuring out if the stars are real, and if they're the right hemisphere. (can't be used for location without the time and orientation of the camera)
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
Fairford IAT 1989.
[1] https://www.thesr71blackbird.com/Aircraft/Engines/starting-t...
At least, that's what I remember.
The whole plane is an engineering tour-de-force, especially considering it was designed with slide rules
https://www.thesr71blackbird.com/Aircraft/Engines/starting-t...
https://www.sacmuseum.org/what-to-see/aircraft/sr-71a-blackb...
[1] https://www.google.com/maps/@34.6026576,-118.0860601,117m/da...
Was it rough or smooth? It looked smooth but I wonder if it felt rough!
(I was also impressed by how many aircraft could fit on an aircraft carrier. There was also a Concorde!)
(The real question being, of course, what is the DEF-G?)
There aren’t many details but it’s some kind of electronic countermeasures/data collection system.
See the museum exhibit here:
Quantum navigation systems could also determines position from quasi-stable astral signal sources FWIU. https://news.ycombinator.com/item?id=36222625
Sunstone: https://en.wikipedia.org/wiki/Sunstone_(medieval)
Amplituhedra and cost of calculation: https://en.wikipedia.org/wiki/Amplituhedron
https://sandiegoairandspace.org/collection/item/lockheed-a-1...
How did it fly for 10hrs (based on the parent article) at high speeds without a ton of space for fuel?
They refueled in-flight, and the high speeds they are referring to probably weren't sustained for 10 hours... I think it is more like "while traveling at high speeds and for up to ten hours"...
As far as fuel goes (a) in a three-dimensional object, "volume adds up fast," and (b) aerial refueling.
(p.s. My dad was a US Navy pilot in the early 60s when celestial navigation was still core curricula.)
There were supposed to be more variants, even tactical bombers but military politics and budget constraints and yadda yadda yadda.
The Hokulea's maiden voyage was in 1975 and since then it has made global voyages to demonstrate and preserve ancient Polynesian wayfinding methods.
Here's a video where a local news channel covered an earlier voyage of the Hokulea (2014) and summarized how the ancient sailors would have used the stars as reference points: https://youtu.be/dla3RoQo37M
The waves do dissipate, but the dissipation and attenuation is what makes the best waves. In the storm the waves are huge and messy with all kinds of frequencies interfering with each other. Attenuation means the high frequency / small amplitude waves dissipate the quickest and the lowest frequency / high amplitude waves dissipate the slowest.
By the time they've moved a long way, all that's left are the lowest frequencies which makes for a clean smooth wave. The amplitude will have reduced compared to the original storm, but that original long period is still there creating nice long gaps between the waves. This is why surfers care about the period of an incoming swell - it's a proxy for how the swell has cleaned up on it's travels.
The best waves come from the biggest storms the furthest away.
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 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.
Also, fun fact - in 2025 we will cross over into a period of history where the SR-71 first flew closer to the Wright Flyer than to the present day.
Edit: Ben Rich, not Joe Rich. Thanks runjake!
App: https://www.celestialprogramming.com/apps/celestialfix/sexta...
Talk (with very low audio): https://www.youtube.com/watch?v=5kAqcZYmWjA&t=5s
Given that it may very well be better to assume that anything untested doesn't work at all and to live within those restrictions.
> Given that it may very well be better to assume that anything untested doesn't work at all and to live within those restrictions.
There are an infinite number of untested cases though. Figuring out the important ones is the hard part, otherwise they likely would have been identified and fixed in development.
You get "Sorry, we could not calculate driving directions from "Wairiki, Fiji" to "Welagi, Fiji"
https://www.google.com/maps/dir/Wairiki,+Fiji/Welagi,+Fiji/@...
It's wild that on google maps, even dropping a pin on the Tavuki road and trying to drag it across the line, it just stops, hitting this invisible wall.
Something about this experience makes me want to go there....
Edit: and the nearby Rabi Island has a discontinuity at the meridian in map view. Zooming in on it in satellite view sent the map into a crazy refreshing state with flickering grid lines.
As I noted elsewhere in this thread, large swathes of US software couldn't handle mapping computations that straddled the date line and it's breathtaking that this is still an issue today.
I company I coded for surveyed the entire Fiji region in 1997, drafting aircraft at 80m ground clearance in long lines across both sides of the 180 longitude line.
Every single bit of commercial US GIS software available at the time was garbage and failed to correctly compute line lengths that straddled the 180 longitude line, areas of rectangles that did the same, correctly polygon mask etc.
Fortuneately we had in house software (that had the same flaws, considering it originated from Sunnydale, California) and source code so this became Yet Another Patch I had to write in on the fly in the midst of everything else to move forward.
I wrote issue tickets on this to ArcView | ESRI (of the day), the open GIS groups of the day, and raised it with anybody on relevant IRC boards | early reddit who was talking about their aircraft control software, etc.
I haven't thought about that for 14 odd years now .. but I really thought the base libraries in Google Maps would correctly handle geodesic geometry by now.
Scripps authored some pretty decent open source CLI unix mapping software that you could pipe together to do all manner of things data presentation wise that dates back to the 1980s at least.
That could handle line lengths across the 180 longitude line .. they thought globally and ran sensors from California to Hawaii to the South China Sea (and elsewhere in the world).
Even the original Sydney-based digital mapping start-up Where 2 Technologies that spawned Google Maps (not the 3D Google Earth) could handle those calculations (as I recall, they even pulled some libraries from people I worked with) - I'd have to check but I believe Where 2 shared some DNA with ERMapper (Perth, W.Australia based global resource mapping company).
At some point post aquisition they must have rewritten | simplified assumptions and never availed themselves of US open software paid for by their own tax dollars.
In the above I was recollecting a code header from ~ 26 years ago, I'm Australian and got a single letter wrong in a district name of country I don't live in.
You okay with that or are you just here to nitpick?
And how many potential users does this affect? Enough for Google to spend 10 seconds worrying about it?
Guam would beg to differ. :)
Kidding, people!
No time zone no bite
The distance along the zero latitude equator from -179.99 W to +179.99 E should be relatively easy to compute and yet a large proportion of software in the mapping domain screws that up - even software that controls drones and| used by commercial pilots in the US, etc.
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.
I was working in Samoa when they changed the date to align with NZ time, so am quite familiar with the region.
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 )
No Euler angles no bite
But with only 4 operational shuttles, ~20 days maximum ndurance and only 5-10 flights per year, it was simply enough to just avoid scheduling any mission in the latter half of December.
(Though, I notice STS-103 departed for an 8 day mission on December 19th 1999. That was cutting it close)
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 that on Google ;)
[1] https://airandspace.si.edu/webimages/collections/full/NAS-14...
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 blind (without knowing any details about the telescope/camera) though that takes a couple of minutes.
From what I’ve read (mostly the excellent book “Inventing Accuracy” the main challenge is very precisely aligning the telescope with the “stable member” in the gyroscope.
The Trident I used a Vidicon tube (what they used to use for TV cameras before CCDs were invented) [2] The Trident approach was to shoot a single star once in the flight.
The Trident II uses a CCD. The first version of the guidance system for that missile (The Draper Mark 6) used a 90x90 CCD [3]. That has been replaced with the Mark 6 Mod 1, which they say has increased resolution but they don't give a figure [4]
[1] NAS-14V2 ANS System Manual, Page 10A-49 https://airandspace.si.edu/webimages/collections/full/NAS-14...
[2] Inventing Accuracy, Page 290
[3] The Trident II (Mk-6) Guidance System, Page 1460 https://sci-hub.se/https://doi.org/10.2514/6.1991-2761
[4] Modifying the MARK 6 Guidance System Part 1 https://www.electronicdesign.com/home/article/21201730/modif...
If you know roughly where you're looking, the lookup is really quite quick.
The way I think about it is... when I was a kid I hated waiting at lights and imagined you could build a computer vision/ML system (this was in the '80s) that coudl recognize traffic and change the light to green when it was safe, rather than timing out. I mentioned this to some traffic engineer and he pointed out the simpler solution was to put magnetic detectors under the road and then just look for blips which are cars driving over.
My local town has a roundabout with a cut-through lane for buses. The cut-through has a traffic light to help the bus emerge. Every so often, a (presumably non-local) car driver accidentally enters the bus lane, and then has to wait for the next bus to trigger the traffic light.
https://nova.astrometry.net/ will do the blind solve.
If you want to learn more the keyword to google is "plate solving"
Interesting to see similar stuff here :)
If you see the night sky every night (without distracting screens), the shapes became kind of familiar.
So now you can see why Polaris will not always be aligned with the north spin axis of the Earth - because that axis is slowly changing the direction in which it points (precession)! Right now, the Earth's rotation axis happens to be pointing almost exactly at Polaris. But in the year 3000 B.C., the North Star was a star called Thuban (also known as Alpha Draconis), and in about 13,000 years from now the precession of the rotation axis will mean that the bright star Vega will be the North Star.But of course if you really know the dark sky well, there are a lot more points of references, you will remember what constellations will be where at what time of the night at what season. Or where the moon is, etc.
Ring Laser Gyroscopes are another nifty nav tool in this space: https://en.wikipedia.org/wiki/Ring_laser_gyroscope#/media/Fi...
https://en.m.wikipedia.org/wiki/Advanced_Inertial_Reference_...
More details on the link here: https://www.nasa.gov/feature/gemini-xii-crew-masters-the-cha...
What’s actually on aircraft tends to be classified.
Fighters don't have the legs to fly far enough that celestial navigation becomes worth the added complexity.
For other air mobility platforms like the C-130 or C-17 in my experience they do not include these features, as GPS, INS, and regular old "ask ATC for a vector" are usually good enough.
There are ongoing experiments with magnetic and other forms of navigation, some of which are classified, but I'm a civilian now so I don't know any specifics.
You are probably right that this went away sometime in the 1970s.
Damn, now I'm feeling old. I miss the stars.
I'm saying something different, which is that unlike the SR-71, the C-130 didn't and doesn't have an instrument that scans the sky and automatically determines where it is based on the constellations it can see.
Yet we see Ukraine doing precision strikes not only with long-range missiles, but also with all kinds of drones.
In this case, I went to Duxford a day before this was posted on HN. I visited the #962 SR-71 in person. At the day this was posted, I also discussed about the SR-71 with a neighbour and how it was stationed at RAF Mildenhall here in the UK.
With that said, SR-71 is such an awesome machine, it contains so many breakthroughs and innovations. It was so advanced that even the tooling, methods, paint and even fuel had to be invented specifically for this aircraft.
> were highly accurate, able to lock onto up to 11 stars (even in daytime) and resolve the craft's position to less than 300 feet (91 m)
- ICBM
https://en.m.wikipedia.org/wiki/LGM-118_Peacekeeper#/media/F...
I was talking to a grad student who was having an issue getting descent flat frames (images of a uniform field, used to account for dust and optical train effects). I asked why she didn't just take a picture of the sky in the daytime like most amateurs do, and she said she always ends up with stars in the image doing it that way. They tried finding the least populated part of the sky, but still always picked up stars.
This link explains them in more detail:
https://www.highpointscientific.com/astronomy-hub/post/astro...
Instead, you want one of these!
https://support.phaseone.com/knowledgebase/article/KA-01239/...
I guess you'll need something like an integrating sphere? https://en.wikipedia.org/wiki/Integrating_sphere
Photography reviews often measure vignetting by putting a piece of tissue paper on the lens lol.
Some people do use tissue paper, or a t-shirt over the lens, and that works for making pretty pictures. But she said none of them come close to 1% accuracy.
But now you have me wondering how the big telescopes do it. Things like the JWST or HST, or even large ground based scopes don't really have any of those options.
Status quo before ICBMs being strategic bombers, many of which could be neutralized en route.
Ironically enough, the much cheaper but less impressive U-2 is still in use today.
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 early aviation that is routinely forgotten by history is the fact that navigation was extremely difficult in a world before GPS. For example in WWII, pilots getting lost was a huge problem, especially for the Navy pilots. Imagine taking off of an aircraft carrier and flying hundreds of miles away from it, completing a mission and then trying to retrace your steps and find the 100 yard long dot in the wide open ocean again while flying at 10,000+ feet altitude. Pilots navigated with simple directions of, "heading 310 for 50 knots, heading 120 for 80 knots" and they would follow a handwritten piece of scrap paper and then try to come back. There were no landmarks to follow. To make things even more complicated, we didn't exactly know distances very well. In a world like the ocean with no landmarks, you rely purely on compass and distances and time for directions. But if there is a tailwind vs a headwind then you could travel 80 knots in 30 mins instead of 45 minutes. This could put you wildly off course when you go to turn. It was incredibly scary to get into a cockpit and sail off into the ocean with no landmarks and hope to find a target and return back to the carrier (which itself is also moving). This is also why bombers and even long-range fighters actually had dedicated "Navigators" on board who's sole job was navigation during flight.
As an example, The Battle of Midway was almost a complete failure for the USA because the main bomber squadron actually got lost trying to find the ships that they were meant to bomb. Iirc they had meandered around the destination area for almost an hour and were bingo on fuel. The squad commander had actually given the order to turn around and as the planes were turning around, one of the pilots spotted the Japanese carriers in the distance. The battle of midway up to this point was a complete failure and had overexposed the Navy. The first dive bomb attack had lost all but 3 dive bombers (one of which only survived because he got separated and lost). The Japanese were getting ready to counter strike on the remaining US Navy which were congregated (against the will of most admirals and generals) just a hundred miles away. The fighter wing had shown up before the second primary bomber wing (which had gotten lost) and had alerted the Japanese to the surprise attack, in addition to devestating losses (about 2/3) for the fighters. If these lost bombers had returned back without completing their successful bombing raid, it is safe to say that history would be re-written. Japan would have destroyed the US Navy and eventually consumed the USA. This would have distracted the US from aiding Europe and Europe would have likely been lost to Germany. All because of how difficult it was to navigate before GPS.
I just find early aviation so fascinating with how they accomplished so much with so little. We often look back and forget so many simple things about aviation like navigation because we take it for granted today. Hell, my watch can pinpoint my location anywhere on earth to within a few feet. Yet location in the 40s and 50s was usually determined by drawing circles on a map that cover 50 mile diameters and saying "we think we are somewhere in here".
A prime example is the original story. In a world before GPS, where we need precise long-range navigation, what are you going to do? You have to work with what you have. We didnt have satellites yet (well at least not ones like we needed), you are too high for anything visual on the ground, too fast to reliably navigate manually, so what's left? The stars. I'm sure someone in that brainstorming meeting said it was impossible, but there were no other choices, so they figured it out. And it's incredible!
And Italy. After fighting in North Africa, which tied up German resources and scrubs like, oh, one Field Marshal Erwin Rommel.
Without American equipment, the USSR would not have had the supplies to push the Germans west. Without a Russian front, the UK and the USA might not have been able to dislodge Germany from Europe, and the UK may have fallen [4]. Without Britain in allied hands, it would have been vastly more difficult for the USA to stage D-Day, and they certainly would not have been able to provide the fuel for their logistical needs via the Pluto pipeline [5].
1. https://en.wikipedia.org/wiki/Lend-Lease
2. https://en.wikipedia.org/wiki/Europe_first
3. https://en.wikipedia.org/wiki/Malta_Conference_(1945)
Still a very important battle and a gripping story.
The Japanese war plan was strategically inept from the outset - hit the US really hard, then sue for peace from a position of strength. But even if they got the carriers at Pearl Harbor, it was only a matter of time before US industrial output buried them and they failed to account for an enemy committed to total war. The turning point happened at Midway but the specific time and place don't really matter - it was inevitable. For Japan to win the war they would have had to walk an improbable golden path from victory to decisive victory while suffering no irreplaceable losses.
By the way, Germany displayed similar strategic ineptitude. Even if Germany won the Battle of Britain, they would not have been able to supply any invasion force they managed to land on Britain. They had no surface fleet, and they were staring down the largest navy in the world! All the Royal Navy needs to do is contest the Channel for a critical week or two and you've just lost your entire invasion force. As it happens they lost the BoB. Unable to finish the war against a globe-spanning empire, they proceeded to send their entire army into the USSR...
...and while US lend-lease certainly helped, the Soviet counteroffensive at the end of 1941 already inflicted such damage on the Wehrmacht that they started suffering shortages of men and equipment. The unsuccessful German offensive in 1942, Case Blue, was more limited in scope than Barbarossa because of these shortages - attacking in the southern USSR rather than the entire front as in 1941. Case Blue started the same month as the Battle of Midway - the outcome of the two could hardly be linked. With or without lend-lease, by end of '42 they are knee-deep in Russia with no prospect of further advance, while Britain blockades them on the other side.
Pilots in WWII had things like the predecessor to TACAN to navigate with -- my grandfather was a pilot in the Army Air Corps and described navigation with radio beacons regularly.
Aircraft Carriers don't move far in the short time CV based aircraft are up -- they just need to navigate back to where they took off from. That's not as hard as it sounds, even with 1940s technology. You just need to navigate to within radio range, which is a couple hundred miles if you're in the air.
At the same time, they did get lost at times.
RN strike aircraft also had their own radar which made it easier to find things.
> No mid-flight "re-calculating route" if stuff goes wrong.
From what I understand of the manual[0], the system doesn't get completely lost if the crew decides to abort and fly away or something. The preprogramming is mainly so the sensors and camera automatically engage at the predefined points in the planned flight.
[0] https://airandspace.si.edu/webimages/collections/full/NAS-14...
The crazy thing about this system too is that, like everything on the SR-71, it was done on a shoestring budget (relatively) and crazy fast. So a navigation system like this was done as a necessary workaround to traditional navigation of the time.
> 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.
Or if you'd prefer, the WW2 interpretation of air warfare probably leans towards treating the entire populace as hostile.
"[The plane] flew coast to coast [in the U.S] in 67 minutes"
Being able to go from NY to California in an hour seems pretty great
994, that is.
https://theaviationgeekclub.com/wp-content/uploads/2023/09/S...
Why, was he studying to build his own planes from scratch too?
https://en.wikipedia.org/wiki/Convair_B-58_Hustler?oldformat...
SR-71 Blackbird Speed Check Story
https://news.ycombinator.com/item?id=36041845
https://www.thesr71blackbird.com/Aircraft/Stories/sr-71-blac...