Ships must practice celestial navigation(usni.org)
usni.org
Ships must practice celestial navigation
https://www.usni.org/magazines/proceedings/2025/january/ships-must-practice-celestial-navigation
114 comments
The main principle of celestial navigation is pretty easy to visualize.
Pick a celestial body that's in your sky right now, like the Sun. At any given time, the Sun is directly over a single point on the globe (the GP, or Geographic Position). So if you measure the Sun as being directly over your head, you know where you are exactly on the globe, after consulting your clock and almanac.
But, if you measure the Sun at a non-overhead angle, then you and everyone else with that same measurement must be on a circle whose centre is the Sun's GP. (Visualize the circle as the edge of a flashlight beam being pointed directly downward at the GP.) The rest of celestial navigation is refinements to figure out where you are on that circle.
Pick a celestial body that's in your sky right now, like the Sun. At any given time, the Sun is directly over a single point on the globe (the GP, or Geographic Position). So if you measure the Sun as being directly over your head, you know where you are exactly on the globe, after consulting your clock and almanac.
But, if you measure the Sun at a non-overhead angle, then you and everyone else with that same measurement must be on a circle whose centre is the Sun's GP. (Visualize the circle as the edge of a flashlight beam being pointed directly downward at the GP.) The rest of celestial navigation is refinements to figure out where you are on that circle.
You can also do it at night using star charts (or as you call it, an "almanac"). That's how most of the digital celestial navigation solutions work, they use the positions of bright stars to determine a fix based on observatory data.
You can try it yourself here:
https://nova.astrometry.net/
You can try it yourself here:
https://nova.astrometry.net/
Might I differ on "easy", from second hand experience of watching my
father go through his advanced yachtsmanship RYA Astro Navigation
exams and cursing at trig functions? In practice its a lot of paper
and compasses.
The USA who just threatened to invade a few NATO allies? People working with USA for the next few years seems pretty foolhardy. Surely everyone else in NATO needs to be getting together and building it defense system that exclude USA.
For (e.g.) eLoran, each chain is independent of every other chain. So the network chain(s) run in the EU are not dependent on the chains in US/CA, are not dependent on the chains in Russia, or the Middle East:
* https://en.wikipedia.org/wiki/File:NGA-Atlantic_Loran.png
The chains run by Japan are not dependent on the chains run by South Korea, would not be dependent on chains run by AU or NZ:
* https://en.wikipedia.org/wiki/File:NGA-Pacific_Loran.png
* https://en.wikipedia.org/wiki/Loran-C#Limitations
India, China, and Pakistan could all run their own infrastructure:
* https://commons.wikimedia.org/wiki/File:Loranstationscrkl.jp...
The only agreement being the technical standards (frequencies) and timing offset for near-by chains.
(And I'm Canadian.)
* https://en.wikipedia.org/wiki/File:NGA-Atlantic_Loran.png
The chains run by Japan are not dependent on the chains run by South Korea, would not be dependent on chains run by AU or NZ:
* https://en.wikipedia.org/wiki/File:NGA-Pacific_Loran.png
* https://en.wikipedia.org/wiki/Loran-C#Limitations
India, China, and Pakistan could all run their own infrastructure:
* https://commons.wikimedia.org/wiki/File:Loranstationscrkl.jp...
The only agreement being the technical standards (frequencies) and timing offset for near-by chains.
(And I'm Canadian.)
It wasn't "the USA", it was our incoming president, who everyone knows speaks for no one but himself.
The president speaks for the united states. Brushing his comments off like that is absurd. You act like he got the job in a raffle, the majority of the voting population voted for him, explicitly asking him to speak for them.
The USA technical infrastructure can be shutdown entirely any time EU wants. Hint: ASML Machines and Remote Disable...
I'm pretty sure the threatened invasions are just distractions to change the conversation from the H1B debacle.
If for no other reason than Canada is a country a lot of Americans actually care about (many have relatives there), and without a formal declaration of war congress could step in at any time and declare the whole thing illegal, enabling the military to refuse orders relevant to the invasion.
But as an American who has been a little sick of Europe mooching off of our military overwatch (see various European nations running out of bombs during the Libya campaign), I'm all for an independent European military command with independent capacity. The Cold War is over, the Russian tank hordes that once threatened to roll across Western Europe haven't managed to roll halfway across Ukraine with even reluctant, intermittent, indirect western support. We don't need to be under some monolithic military command anymore, Europe does not (or at least should not) need US strategic overwatch to fend off Russia.
As for the "European militarization has historically led to world wars" argument, the UK, France, and Russia all have nukes. Germany could probably build a few in a long weekend if sufficiently motivated. We aren't going to see a WWI or WWII rematch unless the AI "revolution" actually turns out to be more than smoke and mirrors for dumb money and enables perfect missile defense or something.
So yeah, please get an ex-US NATO off the ground so we can focus on China.
If for no other reason than Canada is a country a lot of Americans actually care about (many have relatives there), and without a formal declaration of war congress could step in at any time and declare the whole thing illegal, enabling the military to refuse orders relevant to the invasion.
But as an American who has been a little sick of Europe mooching off of our military overwatch (see various European nations running out of bombs during the Libya campaign), I'm all for an independent European military command with independent capacity. The Cold War is over, the Russian tank hordes that once threatened to roll across Western Europe haven't managed to roll halfway across Ukraine with even reluctant, intermittent, indirect western support. We don't need to be under some monolithic military command anymore, Europe does not (or at least should not) need US strategic overwatch to fend off Russia.
As for the "European militarization has historically led to world wars" argument, the UK, France, and Russia all have nukes. Germany could probably build a few in a long weekend if sufficiently motivated. We aren't going to see a WWI or WWII rematch unless the AI "revolution" actually turns out to be more than smoke and mirrors for dumb money and enables perfect missile defense or something.
So yeah, please get an ex-US NATO off the ground so we can focus on China.
Even if it's just a distraction, countries usually distract from their internal problems by targeting un-allied countries as the source of their problems. For example, when China has some internal issue, they start complaining about Japan or Taiwan. When Iran has problems, they threaten the US.
When countries start threatening those who aren't their active enemies, it's a first step into normalization of the rhetoric and building up support for inhuman actions. Iraq wasn't even in anyone's mind until suddenly America needed to invade and "liberate" it just for some president's personal ego, and the overwhelming majority became convinced that Iraq was involved in 9/11 (it wasn't) and steamrolling the entire country was doing the world a public service (it wasn't)[1]. Nobody was even thinking about Greenland or Denmark in the US until someone with a big ego started talking about liberating it. Now the same political faction that had 89% support for the Iraq War is starting up the same thing.
[1] https://www.pewresearch.org/politics/2023/03/14/a-look-back-...
When countries start threatening those who aren't their active enemies, it's a first step into normalization of the rhetoric and building up support for inhuman actions. Iraq wasn't even in anyone's mind until suddenly America needed to invade and "liberate" it just for some president's personal ego, and the overwhelming majority became convinced that Iraq was involved in 9/11 (it wasn't) and steamrolling the entire country was doing the world a public service (it wasn't)[1]. Nobody was even thinking about Greenland or Denmark in the US until someone with a big ego started talking about liberating it. Now the same political faction that had 89% support for the Iraq War is starting up the same thing.
[1] https://www.pewresearch.org/politics/2023/03/14/a-look-back-...
I think it’s a bit unfair to say Iraq wasn’t in anyone’s mind. Clinton spent the 90s bombing Iraq after coalition forces invaded to stop the Kuwait invasion in 1991. And saddam hussein was regularly declaring America as moral enemy of Iraq. Saddam Hussein had nothing to do with 9/11 but I feel like he was regularly discussed throughout the 90s and so was easy to inject back into the conversation in 2003. This is really different than randomly saying that Canada is Americas hat or Greenland should be liberated.
All that being said, Americans grew up, long before Donald trump entered the political discourse, learning that they live in the greatest country on earth and that everyone wants to move there and become American. This is a core component of Donald trump’s political message of make America great again. So why wouldn’t the average American be accepting the idea that other places want to join in on the fun? Democrat or Republican most seem to buy in to American exceptionalism.
All that being said, Americans grew up, long before Donald trump entered the political discourse, learning that they live in the greatest country on earth and that everyone wants to move there and become American. This is a core component of Donald trump’s political message of make America great again. So why wouldn’t the average American be accepting the idea that other places want to join in on the fun? Democrat or Republican most seem to buy in to American exceptionalism.
Having personally lived through the 90's and 00's, I can confirm that:
* Sadam Houssein (and Kadhafi, and Khomeini) regularly moaned about the US
* everybody was indeed aware of them
* and everyone ignored them
* for most people outside the US, the second gulf war was perceived a transparent lie
One look at the ridiculous "coalition of the willing" that GWB managed to drum up makes that clear.
https://en.wikipedia.org/wiki/Coalition_of_the_willing_(Iraq...
* Sadam Houssein (and Kadhafi, and Khomeini) regularly moaned about the US
* everybody was indeed aware of them
* and everyone ignored them
* for most people outside the US, the second gulf war was perceived a transparent lie
One look at the ridiculous "coalition of the willing" that GWB managed to drum up makes that clear.
https://en.wikipedia.org/wiki/Coalition_of_the_willing_(Iraq...
>But as an American who has been a little sick of Europe mooching off of our military overwatch
Thousands of european soldiers have died because of US war on terror the last decades, not the other way around.
Thousands of european soldiers have died because of US war on terror the last decades, not the other way around.
> But as an American who has been a little sick of Europe mooching off of our military overwatch
As a European (now living in the US) I think this perspective might be an oversimplification. Access to EU soil has been incredibly important for US military strategy over the last 50 years. Having bases in Germany, Spain and Italy is instrumental in US campaigns in Middle East or Asia. Not to mention the amount of European lives lost in conflicts initiates or led by US interests.
As a European (now living in the US) I think this perspective might be an oversimplification. Access to EU soil has been incredibly important for US military strategy over the last 50 years. Having bases in Germany, Spain and Italy is instrumental in US campaigns in Middle East or Asia. Not to mention the amount of European lives lost in conflicts initiates or led by US interests.
Maintaining NATO also ensures American hegemony over Europe and potentially the most disruptive global competitor. It may be expensive, but we know that left to their own devices the Europeans are wont to start a war amongst themselves, over some trivial border dispute, and then involve the rest of the world in it. So it's cheaper in American lives and material this way.
That may be the predominant American belief, but I would point out that about over half of Europe — by population, making the zone larger than the USA — now has borders slightly more porous than the ones between American states.
https://en.wikipedia.org/wiki/California_Border_Protection_S...
https://en.wikipedia.org/wiki/Schengen_Area
https://en.wikipedia.org/wiki/California_Border_Protection_S...
https://en.wikipedia.org/wiki/Schengen_Area
My impression is the US has pretty consistently tried to dissuade the EU from developing any kind of capable military organisation and to instead do it as part of NATO.
Although I have to assume that with Trump as president for a second time a lot of people in europe are going to have to worry that the US can't be relied on in the way it could in the past so I think you might get your wish.
Where that leaves NATO afterwards, I don't know.
Although I have to assume that with Trump as president for a second time a lot of people in europe are going to have to worry that the US can't be relied on in the way it could in the past so I think you might get your wish.
Where that leaves NATO afterwards, I don't know.
> My impression is the US has pretty consistently tried to dissuade the EU from developing any kind of capable military organization
It’s been a policy of the US government to discourage strong independent European militaries since about 1945. Same policy towards Japan, too.
It’s been a policy of the US government to discourage strong independent European militaries since about 1945. Same policy towards Japan, too.
> So yeah, please get an ex-US NATO off the ground so we can focus on China.
If the US does not care about its European allies, it no longer has the economic power to "focus on China". From an European perspective, China is far away and not particularly threatening. If there are no specific reasons to support the US, it's better to not take sides and trade with both sides.
BRICS is already a serious challenge to the Western hegemony. If the US thinks that "the West" has no longer a reason to exist, it will be seriously outnumbered by those who don't share its ambitions.
If the US does not care about its European allies, it no longer has the economic power to "focus on China". From an European perspective, China is far away and not particularly threatening. If there are no specific reasons to support the US, it's better to not take sides and trade with both sides.
BRICS is already a serious challenge to the Western hegemony. If the US thinks that "the West" has no longer a reason to exist, it will be seriously outnumbered by those who don't share its ambitions.
> BRICS is already a serious challenge to the Western hegemony.
A semi-joke-y observation:
> Pretty straightforward really. You combine Brazil's history of monetary stability, with Russia's respect for property rights, India's domestic tranquility, China's financial transparency, and South Africa's investment opportunities - and hey presto, you've got a new global money.
* https://twitter.com/davidfrum/status/1665053372402081792
If the 'BRICS currency' is made up of only a small group, then it's not going to be useful, especially the restrictive countries that are in the name.
But if you expand it, sure it could become more useful, but then you've got competing interests and desires and a coördination problem on policy and such.
Further: I've yet to see an explanation of how this thing will actually work. Does each country given up their own currency, Euro-style? Is there a 'theoretical currency' that everyone pegs their own to? What are the consequences for de-pegging (if any)? Are bonds issued in BRICS or the country's own currency?
A semi-joke-y observation:
> Pretty straightforward really. You combine Brazil's history of monetary stability, with Russia's respect for property rights, India's domestic tranquility, China's financial transparency, and South Africa's investment opportunities - and hey presto, you've got a new global money.
* https://twitter.com/davidfrum/status/1665053372402081792
If the 'BRICS currency' is made up of only a small group, then it's not going to be useful, especially the restrictive countries that are in the name.
But if you expand it, sure it could become more useful, but then you've got competing interests and desires and a coördination problem on policy and such.
Further: I've yet to see an explanation of how this thing will actually work. Does each country given up their own currency, Euro-style? Is there a 'theoretical currency' that everyone pegs their own to? What are the consequences for de-pegging (if any)? Are bonds issued in BRICS or the country's own currency?
BRICS is a total joke. Some of the member countries have taken limited unilateral actions to challenge Western hegemony but BRICS as a group has never taken any meaningful coordinated action and never will. India won't go along with anything that benefits China. South Africa is a failed state. Brazil has no global ambitions. And the Russian Empire is bleeding to death in Ukraine; even if they eventually "win" their ability to challenge us has disintegrated.
BRICS is not supposed to be a coordinated power. It's a tool for creating the multipolar world order Putin has been dreaming of for decades. A world where the US is just one power among many and the dollar just one currency among many.
And the best way to achieve that is creating a wedge between the US and its allies.
And the best way to achieve that is creating a wedge between the US and its allies.
> It's a tool for creating the multipolar world order Putin has been dreaming of for decades
India and China just barely wrapped up hostilities, and maintain geopolitical contest with each other. India is increasing defence ties with America. Egypt and the UAE host American armed forces.
BRICS is a propaganda tool for leaders who want to blame their failures on a foreign boogeyman. About the best thing for American (and dollar) hegemony would be BRICS continuing to exist. (Versus e.g. China internationalising the renmimbi.)
India and China just barely wrapped up hostilities, and maintain geopolitical contest with each other. India is increasing defence ties with America. Egypt and the UAE host American armed forces.
BRICS is a propaganda tool for leaders who want to blame their failures on a foreign boogeyman. About the best thing for American (and dollar) hegemony would be BRICS continuing to exist. (Versus e.g. China internationalising the renmimbi.)
> And the Russian Empire is bleeding to death in Ukraine; even if they eventually "win" their ability to challenge us has disintegrated.
LOL. USSR had plan how to win war with NATO called «icebreaker» («ледокол»): influence elections or bribe politics in enemy countries to put puppets into powerful seats, then use puppets to start internal conflicts between members of NATO, then support a single side or both sides in the proxy war.
LOL. USSR had plan how to win war with NATO called «icebreaker» («ледокол»): influence elections or bribe politics in enemy countries to put puppets into powerful seats, then use puppets to start internal conflicts between members of NATO, then support a single side or both sides in the proxy war.
Sowing dissent is relatively easy, so I hope we defend against it.
However, on a military level, Russia is being held off by the Ukrainian people (and 37% of the Ukrainian economy) supported by foreign donations equivalent to the current military spending of any one of the United Kingdom (2.33% of the UK's GDP), Germany (2.12% of German GDP), or France (2.06% of French GDP).
If Poland was both threatened and totally isolated from allies, they could triple their military spend to equal the current Ukrainian forces plus all donations, and do so with only half the percentage of their GDP as compared to Ukraine.
Everyone would rather that this war goes away and they can return to spending money on things that are directly valuable, rather than the necessary but un-productive task of defending all the things we value.
But from a purely military perspective, ignoring how they may sow dissent, my only worry about Russia is that the nukes might not have had all their critical elements sold off in separate black market deals since the end of the cold war.
However, on a military level, Russia is being held off by the Ukrainian people (and 37% of the Ukrainian economy) supported by foreign donations equivalent to the current military spending of any one of the United Kingdom (2.33% of the UK's GDP), Germany (2.12% of German GDP), or France (2.06% of French GDP).
If Poland was both threatened and totally isolated from allies, they could triple their military spend to equal the current Ukrainian forces plus all donations, and do so with only half the percentage of their GDP as compared to Ukraine.
Everyone would rather that this war goes away and they can return to spending money on things that are directly valuable, rather than the necessary but un-productive task of defending all the things we value.
But from a purely military perspective, ignoring how they may sow dissent, my only worry about Russia is that the nukes might not have had all their critical elements sold off in separate black market deals since the end of the cold war.
How you will defend NATO against Merkel, Orban, Fico, Trump? How you defended NATO against Covid-19?
Russia currently is marching forward in Eastern Ukraine, while Ukrainian partners are recommend to use Ukrainian children instead of promised shells.
Poland is ready to 2022 style of war, but not ready to 2023, 2024, or 2025 style of war.
With each passing year, nukes are easier to manufacture. 1GHz switches are not a n advanced tech anymore. WiFi is working on 6GHz. Nuclear isotopes can be separated at home. Gas turbines are outdated. Nuclear reactions inside nuke can be modeled on gaming notebook. No need for testing. More and more nuclear reactors lowers barrier to tech and radioactive elements. Small 2 kWt reactor with size of washing machine can be built to breed highly radioactive elements.
At some point, everybody will be able to produce nukes or dirty bombs using off the shelf items. We are running out of time anyway. Hiroshima and Nagasaki are forgotten.
Russia currently is marching forward in Eastern Ukraine, while Ukrainian partners are recommend to use Ukrainian children instead of promised shells.
Poland is ready to 2022 style of war, but not ready to 2023, 2024, or 2025 style of war.
With each passing year, nukes are easier to manufacture. 1GHz switches are not a n advanced tech anymore. WiFi is working on 6GHz. Nuclear isotopes can be separated at home. Gas turbines are outdated. Nuclear reactions inside nuke can be modeled on gaming notebook. No need for testing. More and more nuclear reactors lowers barrier to tech and radioactive elements. Small 2 kWt reactor with size of washing machine can be built to breed highly radioactive elements.
At some point, everybody will be able to produce nukes or dirty bombs using off the shelf items. We are running out of time anyway. Hiroshima and Nagasaki are forgotten.
> How you will defend NATO against Merkel, Orban, Fico, Trump? How you defended NATO against Covid-19?
I'm saying it isn't necessary to do so, if the enemy is the Russian armed forces.
If the enemy is the Russian propaganda machine, that may be harder, but the armed forces are a joke and it's embarrassing that the rest of the world isn't supporting the Ukrainian military to the level required to make the Russian people themselves remove Putin for wasting Russia's own youth.
(Also: Merkel isn't in, nor is she running for, office).
> With each passing year, nukes are easier to manufacture.
They were never hard, by modern industrial standards. The Russian industrial base isn't up to "modern", they have a lot of corruption, and MAD lends itself to visible threats more than real threats, which means there's a decent chance of any given weapon being a Potemkin.
I've heard serious analysts suggest that Ukraine is merely a few months away from their own independent nuclear capability. But also this is a separate question to delivery systems — and the Russian equipment in general looks shoddy and cheap, as if corruption has hollowed it out.
(My guess is that most Russian nukes have lost fusion boost, most of the *nuclear-capable* missiles can't fly, and most of those which can fly can be shot down by very old anti-missile systems; but this all adds up to about a 90% chance they can't start something if they want to, which isn't odds I'd willingly gamble when the stakes are so high).
> 1GHz switches are not a n advanced tech anymore. WiFi is working on 6GHz.
> Gas turbines are outdated.
None of those are even vaguely relevant.
> Nuclear isotopes can be separated at home.
> More and more nuclear reactors lowers barrier to tech and radioactive elements. Small 2 kWt reactor with size of washing machine can be built to breed highly radioactive elements.
Only in the same technical sense that I can make a nuclear fusion reactor at home. (I really should put together that shopping list…)
The requisite isn't simply "doing it", but the scale and the speed of doing so.
> Nuclear reactions inside nuke can be modeled on gaming notebook. No need for testing.
"In theory, theory and practice are the same. In practice, they are not."
This is also important for confirming that, for example, the tritium boost was actually refreshed with hydrogen-3 rather than the much cheaper but chemically identical hydrogen-1, by someone who pocketed the difference and went on to take early retirement in a small island in the Caribbean.
> At some point, everybody will be able to produce nukes or dirty bombs using off the shelf items.
For dirty bombs, that was true years ago. I think we've actually mostly stopped using americium-241 in smoke detectors? We've definitely stopped using radium for glow-in-the-dark paint. I think thorium still gets sold as welding supplies, but no longer for gas mantles.
But a dirty bomb[0] is to a nuclear bomb[1] as a legal and eye-safe laser pointer[2] is to the NIF lasers… if you stacked up about half a million copies of the National Ignition Facility.
There's thermodynamic limits to nuclear isotope enrichment, and while (I assume) all the relevant info is classified, it's reasonable to guess that it would take burning in the order of a million USD worth of energy to make a minimum viable nuclear explosive.
(Ironic risk factor from PV: much cheaper electricity)
[0] continuous radiohazard that can be hundreds of milliwatts/gram, where a gram of material costs ~ $1500
[1] pulse measured in terajoules
[2] ~1mW
[3] NIF laser pulses are about ~2 megajoules light energy per pulse, so half a million copies would get you 1 terajoule, compared to Fat Man's 88 TJ; ~88 laser pointers gets you the same CW equivalent power of ~1000 USD of americium-241.
To be a health hazard, you'd have to eat or inhale a sample. Which has been made to happen, but it looks like poisoning, not like a bombing: https://en.wikipedia.org/wiki/Alexander_Litvinenko
This is why, despite all the fear of dirty bombs during the War On Terror, we didn't see any.
I'm saying it isn't necessary to do so, if the enemy is the Russian armed forces.
If the enemy is the Russian propaganda machine, that may be harder, but the armed forces are a joke and it's embarrassing that the rest of the world isn't supporting the Ukrainian military to the level required to make the Russian people themselves remove Putin for wasting Russia's own youth.
(Also: Merkel isn't in, nor is she running for, office).
> With each passing year, nukes are easier to manufacture.
They were never hard, by modern industrial standards. The Russian industrial base isn't up to "modern", they have a lot of corruption, and MAD lends itself to visible threats more than real threats, which means there's a decent chance of any given weapon being a Potemkin.
I've heard serious analysts suggest that Ukraine is merely a few months away from their own independent nuclear capability. But also this is a separate question to delivery systems — and the Russian equipment in general looks shoddy and cheap, as if corruption has hollowed it out.
(My guess is that most Russian nukes have lost fusion boost, most of the *nuclear-capable* missiles can't fly, and most of those which can fly can be shot down by very old anti-missile systems; but this all adds up to about a 90% chance they can't start something if they want to, which isn't odds I'd willingly gamble when the stakes are so high).
> 1GHz switches are not a n advanced tech anymore. WiFi is working on 6GHz.
> Gas turbines are outdated.
None of those are even vaguely relevant.
> Nuclear isotopes can be separated at home.
> More and more nuclear reactors lowers barrier to tech and radioactive elements. Small 2 kWt reactor with size of washing machine can be built to breed highly radioactive elements.
Only in the same technical sense that I can make a nuclear fusion reactor at home. (I really should put together that shopping list…)
The requisite isn't simply "doing it", but the scale and the speed of doing so.
> Nuclear reactions inside nuke can be modeled on gaming notebook. No need for testing.
"In theory, theory and practice are the same. In practice, they are not."
This is also important for confirming that, for example, the tritium boost was actually refreshed with hydrogen-3 rather than the much cheaper but chemically identical hydrogen-1, by someone who pocketed the difference and went on to take early retirement in a small island in the Caribbean.
> At some point, everybody will be able to produce nukes or dirty bombs using off the shelf items.
For dirty bombs, that was true years ago. I think we've actually mostly stopped using americium-241 in smoke detectors? We've definitely stopped using radium for glow-in-the-dark paint. I think thorium still gets sold as welding supplies, but no longer for gas mantles.
But a dirty bomb[0] is to a nuclear bomb[1] as a legal and eye-safe laser pointer[2] is to the NIF lasers… if you stacked up about half a million copies of the National Ignition Facility.
There's thermodynamic limits to nuclear isotope enrichment, and while (I assume) all the relevant info is classified, it's reasonable to guess that it would take burning in the order of a million USD worth of energy to make a minimum viable nuclear explosive.
(Ironic risk factor from PV: much cheaper electricity)
[0] continuous radiohazard that can be hundreds of milliwatts/gram, where a gram of material costs ~ $1500
[1] pulse measured in terajoules
[2] ~1mW
[3] NIF laser pulses are about ~2 megajoules light energy per pulse, so half a million copies would get you 1 terajoule, compared to Fat Man's 88 TJ; ~88 laser pointers gets you the same CW equivalent power of ~1000 USD of americium-241.
To be a health hazard, you'd have to eat or inhale a sample. Which has been made to happen, but it looks like poisoning, not like a bombing: https://en.wikipedia.org/wiki/Alexander_Litvinenko
This is why, despite all the fear of dirty bombs during the War On Terror, we didn't see any.
This European perspective is one of the reasons that many developing countries outside of Europe didn't condemn Russia's invasion of Ukraine. As India's External Affairs Minister had remarked, "Europe has to grow out of the mindset that Europe's problems are the world's problems, but the world's problems are not Europe's problems."
> and without a formal declaration of war congress could step in at any time and declare the whole thing illegal, enabling the military to refuse orders relevant to the invasion.
I’m pretty sure that war requires congressional approval BEFORE an invasion full stop. Congress in recent history has been fairly cavalier about letting the executive launch military action and looking the other way, but it’s not actually supposed to work this way.
> The Cold War is over, the Russian tank hordes that once threatened to roll across Western Europe haven't managed to roll halfway across Ukraine with even reluctant, intermittent, indirect western support
This is a gross mischaracterization of the situation that significantly underplays what actually happened I think. Without what Biden did right before the war saying “it’s going to happen” and mustering broad domestic and international support as well as using sanctions to freeze Russian assets and use them to pay Ukraine for reparations, Ukraine wouldn’t exist today.
We’re talking about $70B of military HW and $23B in terms of economic and humanitarian aid and another ~87B for the Ukrainian government to keep the lights on. That’s from the US alone. The international community has also contributed another $100B.
> We aren't going to see a WWI or WWII rematch unless the AI "revolution" actually turns out to be more than smoke and mirrors for dumb money and enables perfect missile defense or something.
It’s a slower burn. Putin isn’t going to try to take everything at once. It’s the Hitler annexation strategy over a longer time period. A little Georgia here, a little Crimea there, now it’s the entirety of Ukraine. Partly because his country is weaker but also because war is more expensive to prosecute than 100 years ago due to technology and the resistance is much better prepared for such an attempt.
Where do you think Eastern and Western European civilians will flee if any of those countries is drawn into conflict with Russia? Conflict forces desperate immigration which then creates anti-immigration counter responses in domestic populations here in the US.
China is important but what are we going to do there? Do you think we’re going to successfully defend an invasion of Taiwan when it happens? Cause that’s going to be their first military action. And if people are complaining about supporting Ukraine, how do you think they’ll fair regarding Chinese nationalists?
Finally, I’m pretty sure the troops and equipment we need there are also fairly different. If China is delivering huge numbers of land troops to Taiwan in the first place I’d say the battle is very lost. It’s going to be a sea/land siege so if the US gets directly involved it’ll be a meeting of the navies.
I’m pretty sure that war requires congressional approval BEFORE an invasion full stop. Congress in recent history has been fairly cavalier about letting the executive launch military action and looking the other way, but it’s not actually supposed to work this way.
> The Cold War is over, the Russian tank hordes that once threatened to roll across Western Europe haven't managed to roll halfway across Ukraine with even reluctant, intermittent, indirect western support
This is a gross mischaracterization of the situation that significantly underplays what actually happened I think. Without what Biden did right before the war saying “it’s going to happen” and mustering broad domestic and international support as well as using sanctions to freeze Russian assets and use them to pay Ukraine for reparations, Ukraine wouldn’t exist today.
We’re talking about $70B of military HW and $23B in terms of economic and humanitarian aid and another ~87B for the Ukrainian government to keep the lights on. That’s from the US alone. The international community has also contributed another $100B.
> We aren't going to see a WWI or WWII rematch unless the AI "revolution" actually turns out to be more than smoke and mirrors for dumb money and enables perfect missile defense or something.
It’s a slower burn. Putin isn’t going to try to take everything at once. It’s the Hitler annexation strategy over a longer time period. A little Georgia here, a little Crimea there, now it’s the entirety of Ukraine. Partly because his country is weaker but also because war is more expensive to prosecute than 100 years ago due to technology and the resistance is much better prepared for such an attempt.
Where do you think Eastern and Western European civilians will flee if any of those countries is drawn into conflict with Russia? Conflict forces desperate immigration which then creates anti-immigration counter responses in domestic populations here in the US.
China is important but what are we going to do there? Do you think we’re going to successfully defend an invasion of Taiwan when it happens? Cause that’s going to be their first military action. And if people are complaining about supporting Ukraine, how do you think they’ll fair regarding Chinese nationalists?
Finally, I’m pretty sure the troops and equipment we need there are also fairly different. If China is delivering huge numbers of land troops to Taiwan in the first place I’d say the battle is very lost. It’s going to be a sea/land siege so if the US gets directly involved it’ll be a meeting of the navies.
This is very simplistic way of interpreting what Trump said. I would advice to read a bit about the significance of the GIUK (Greenland, Island, UK) in view of warming climate and growing importance of Arctics - melting ice might provide a much better and faster route for trade.
The problem is who will control the entrance and exit to that route and GIKU is one of them. And here we are on the key problem: Denmark for years totally neglected building any security/military infrastructure on Greenland, which suddenly might become a crucial element of the World economy and trade.
Do you really want sadistic regimes like Russia or China to take control over key parts of the potential trade routes (80% of global trade goes through the sees and oceans)?
Whatever you think about Trump, he will be gone in 4 years, someone else can be elected if Trump/Vance fails to deliver. Do you think we can get rid of Putin and his dreams on conquests Europe that easily? Or Xi, who is speeding with extending military potential of China, including nuclear weapons, aircraft carriers? Try to guess why Xi is doing this.
The problem is who will control the entrance and exit to that route and GIKU is one of them. And here we are on the key problem: Denmark for years totally neglected building any security/military infrastructure on Greenland, which suddenly might become a crucial element of the World economy and trade.
Do you really want sadistic regimes like Russia or China to take control over key parts of the potential trade routes (80% of global trade goes through the sees and oceans)?
Whatever you think about Trump, he will be gone in 4 years, someone else can be elected if Trump/Vance fails to deliver. Do you think we can get rid of Putin and his dreams on conquests Europe that easily? Or Xi, who is speeding with extending military potential of China, including nuclear weapons, aircraft carriers? Try to guess why Xi is doing this.
Denmark is in NATO, US base is already in Greenland and I'm sure Danes would be open to add few more. There is no need to invade it. The moment it happens, Europe is lost to the US as an ally and NATO is gone.
You've not addressed threatening the territorial integrity of Denmark. If you're going to say we've misinterpreted him, please quote him. Verbatim, not cleaned up.
Without touching the argument if the end justifies the means, the master of the deal apparently has communicated very badly what his intentions are. Obviously, nobody in Europe understood him.
But let's just wait and see, actions speak louder than words, although given past actions that is not instilling great confidence in me.
But let's just wait and see, actions speak louder than words, although given past actions that is not instilling great confidence in me.
Not to pick on your point about Denmark, but the fact is that there has been no aggressors and thus none to defend it against. The US did try to have a sort of covert base on Greenland many years ago, and in the end it failed.
Yes, someone could invade. But they didn't.
And if they did, they probably wouldn't have been able to stay there for long enough to actually get anything out of it long term, without it turning into a war against NATO.
It is my understanding that it has been agreed a few years ago that additional monitoring should be put in place. I don't think anything else than general tech incompetence of the Danish defense forces has prevented that from happening yet.
But on the hand, as far as I understand the matter, there is still too much ice for it to become a major trade route.
Yes, someone could invade. But they didn't.
And if they did, they probably wouldn't have been able to stay there for long enough to actually get anything out of it long term, without it turning into a war against NATO.
It is my understanding that it has been agreed a few years ago that additional monitoring should be put in place. I don't think anything else than general tech incompetence of the Danish defense forces has prevented that from happening yet.
But on the hand, as far as I understand the matter, there is still too much ice for it to become a major trade route.
The question was “Greenland and Panama” and the answer was “I wouldn’t rule anything out”. It requires a pretty hard squint to convert that into a threat “to invade a few NATO allies”. This sort of intentional misunderstanding of an exaggeration does so much more harm than good.
A western defense system that excludes the USA is naive at best.
A western defense system that excludes the USA is naive at best.
It’s not a hard squint.
If these countries were our allies the answer would be “I have no idea why you would even be thinking that question”, not “we won’t rule anything out”.
If these countries were our allies the answer would be “I have no idea why you would even be thinking that question”, not “we won’t rule anything out”.
Not ruling anything out is not a threat. Panama is not a NATO country. One is not a few. ‘Military options’ is not synonymous with invasion. “Invading” is a funny term for an area currently occupied by several US major military bases. The list continues.
I hate to sound snarky, and I mean this genuinely, but forcing people to defend someone is not a way to generate allies. A decade of “what he actually said was” is enough to turn even the most strident progressives towards the middle at least.
I hate to sound snarky, and I mean this genuinely, but forcing people to defend someone is not a way to generate allies. A decade of “what he actually said was” is enough to turn even the most strident progressives towards the middle at least.
> Now if only the US (and others) would get their act together and build out a backup system to GNSS
They are moving towards quantum navigation (esp subs)
They are moving towards quantum navigation (esp subs)
> They are moving towards quantum navigation (esp subs)
How does that help the merchant marine that is part of the logistical supply chain? Are container ships going to get this quantum nav boxes too? The US pays airlines a retainer to be a reserve fleet [1]: will they get these boxes as well in case of emergency?
What happens to all the civilian infrastructure that need navigation and timing signals?
Considering only the "military" ramifications of GNSS disruption is myopic.
[1] https://en.wikipedia.org/wiki/Civil_Reserve_Air_Fleet
How does that help the merchant marine that is part of the logistical supply chain? Are container ships going to get this quantum nav boxes too? The US pays airlines a retainer to be a reserve fleet [1]: will they get these boxes as well in case of emergency?
What happens to all the civilian infrastructure that need navigation and timing signals?
Considering only the "military" ramifications of GNSS disruption is myopic.
[1] https://en.wikipedia.org/wiki/Civil_Reserve_Air_Fleet
> Now if only the US (and others) would get their act together and build out a backup system to GNSS. China, for example, has built out an eLoran system:
What prevents other countries from using these other systems?
What prevents other countries from using these other systems?
Encryption. For example, GPS's P(Y) code is encrypted and only for military use. https://en.wikipedia.org/wiki/Global_Positioning_System
But that’s what the three letter agencies are supposed to do. Surely there’s a good guy back door to that encryption /s
> What prevents other countries from using these other systems?
Nothing.
Nothing also prevents other countries from using China's BeiDou GNSS or their eLoran network.
Nothing.
Nothing also prevents other countries from using China's BeiDou GNSS or their eLoran network.
The US government can apparently turn off their GPS signals over certain parts of the world:
https://idstch.com/geopolitics/denial-gps-services-kargil-wa...
https://idstch.com/geopolitics/denial-gps-services-kargil-wa...
the Earth is the center of the universe, though, just like any other point in space
>As The American Practical Navigator (aka “Bowditch”) states, “No navigator should ever become completely dependent on electronic methods. The navigator who regularly navigates by blindly pushing buttons and reading the coordinates from ‘black boxes’ will not be prepared to use basic principles to improvise solutions in an emergency.”
I wonder if this mindset is also applied, for example, to the rest of the military. Does the Army regularly practice land navigation? I know they get at least one landnav class, but it is a perishable skill. If you don't practice, you'll soon forget about it.
I guess this could also be useful to civilians. Being able to do stuff without relying too much on electronics.
I wonder if this mindset is also applied, for example, to the rest of the military. Does the Army regularly practice land navigation? I know they get at least one landnav class, but it is a perishable skill. If you don't practice, you'll soon forget about it.
I guess this could also be useful to civilians. Being able to do stuff without relying too much on electronics.
Some Army units, particularly ground combat units, regularly practice land navigation with map and compass. I don't think they typically spend much time on celestial navigation beyond the basics of finding heading based on constellations. They're not usually carrying sextants.
There's no real need for celestial navigation on land, the same way there's no need for celestial navigation in most coastal waters: if you can see lines of bearing to known landmarks/navigation markers, you can obtain a fix.
Ships are far more isolated than land crews, and direction-finding is much harder at sea than on land. If you're part of an organization that cares where you are and wants you back, you are pretty easy to find your general location venture off on a land journey and get stuck. A single human might be hard to find under a rock or snow, but an army unit that wants to fund is easy to spot.
The problem with getting lost as an army unit on land is that you might inadvertently get in your enemy's sights before anyone on your side might have had the chance to find you, and at that moment it is game over for said unit. There have been documented a few of these such cases in the war in Ukraine.
There is a lot of GPS jamming happening these days, especially in the Baltic around Kaliningrad. Makes a lot of sense.
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It's really funny to watch a bunch of people contradict the US Navy when it comes to navigation at sea. No, a cell phone isn't going to work in the middle of the Pacific and no, the US Navy doesn't use Google maps. Go get on an actual boat sometime and sail out of sight of land, you lose cell signal way before you're even over the horizon.
A cellphone's GPS only relies on the network for a quickstart. With no network, it takes longer to get the initial fix, but then works perfectly fine.
> A cellphone's GPS only relies on the network for a quickstart.
The point is not to rely on GPS/GNSS:
* https://gpsjam.org
The point is not to rely on GPS/GNSS:
* https://gpsjam.org
Not always true. I have devices with GPS which not only relies on a network for getting ephemeris data for the satellites, but they can't function without it. In other words, they don't even try to get ephemeris data through the GPS signal. So, if there's no network, it doesn't work. One of my devices is even a tablet without a SIM card, it only has wifi.. so if I'm near a cafeteria with wifi I can get a fix, and keep it for a while, but without it it's totally stuck. Forever.
In any case, as others have said, in the ocean a cellphone is useless for navigation. At least use a standalone satellite navigator. And learn to use paper maps and a sextant, it's actually a lot of fun.
In any case, as others have said, in the ocean a cellphone is useless for navigation. At least use a standalone satellite navigator. And learn to use paper maps and a sextant, it's actually a lot of fun.
Ships do use GPS and so do phones and other devices. What exactly are you trying to say?
Have there been any computer vision systems that can approximate celestial navigation using common sensors like a camera, An electronic compass, and a tilt sensor? Something like a computer vision based auto sextant. This is an idea I have thought about for a while but I have zero background in this area.
Yes, starcams are standard equipment on satellites including Cubesats because they provide more precise attitude information than any other available sensor. There are numerous free-software packages for star tracking; a quick search finds https://github.com/spel-uchile/Star_Tracker. I don't know if there's, like, an Android app that will do the required sensor fusion to tell you where on Earth you are.
I looked into it briefly, and while it may be easy at sea with a horizon reference, it becomes surprisingly hard without it (which also complicates testing). The article touches on this with the mention of the bubble sextant required at night, presumably because you can't see the horizon. You'd have the same problem over land.
The stars only give you the angle at which you're looking at the sky. If you know the angle to the center of the earth (or can relate the sky measurement to that) and the exact time, you know where you are, within the inaccuracy of your measurements. Being 1/60th of a degree (1 angular minute) off places you 1 nautical mile off.
A bubble sextant solves this by including a literal 2D bubble level. "When properly used, the bubble sextant gives good results, by which we mean an accuracy to within 5 miles." (https://www.usni.org/magazines/proceedings/1939/june/averagi...).
The obvious solution that immediately springs to mind is a tilt sensor/accelerometer. However, once you get to a useful accuracy, those start getting expensive - several hundred dollars for a 0.01 degree system, which would give you an error of about 1 km.
You'd then need a sufficiently rigid mount for everything, proper calibration (remember, some angle on your mount being 0.05 degrees off completely destroys all usefulness of your system!), and then a camera and a plate solver (software that turns a photo into sky coordinates) should give you a useful fix. I think you could build a system that gets you within a few nautical miles for about $1000 (parts, not labor).
The stars only give you the angle at which you're looking at the sky. If you know the angle to the center of the earth (or can relate the sky measurement to that) and the exact time, you know where you are, within the inaccuracy of your measurements. Being 1/60th of a degree (1 angular minute) off places you 1 nautical mile off.
A bubble sextant solves this by including a literal 2D bubble level. "When properly used, the bubble sextant gives good results, by which we mean an accuracy to within 5 miles." (https://www.usni.org/magazines/proceedings/1939/june/averagi...).
The obvious solution that immediately springs to mind is a tilt sensor/accelerometer. However, once you get to a useful accuracy, those start getting expensive - several hundred dollars for a 0.01 degree system, which would give you an error of about 1 km.
You'd then need a sufficiently rigid mount for everything, proper calibration (remember, some angle on your mount being 0.05 degrees off completely destroys all usefulness of your system!), and then a camera and a plate solver (software that turns a photo into sky coordinates) should give you a useful fix. I think you could build a system that gets you within a few nautical miles for about $1000 (parts, not labor).
The closest unit I can think of right now was the SR-71's celestial navigation unit. I don't know how it worked internally, but it supposedly navigated the spy planes to targets across the globe before GPS existed.
A number of ICBMs used / uses a similar approach. In space, stars are always visible well, and terrestrial navigation aids may have been jammed or destroyed when ICBMs are put to use.
From one SR-71 memoir I remember the factoid that sometimes the electromechanical star tracker was sensitive enough to catch stars in the daylight while the plane was still on the ground. Makes one wonder what is possible now with modern digital photographic sensors and processing power. And miniaturisation of course, the 60s celestial navigation unit was the size of a fridge.
Many aircraft, mostly numbers had similar systems.
I'm not aware of any specifically, but one of the instruments that can be used as a data point to further reduce error when navigating in a zero-GPS/zero-radio-signal environment is an INS. The very highest precision ones are quite classified and used on submarines.
https://en.wikipedia.org/wiki/Inertial_navigation_system
https://en.wikipedia.org/wiki/Inertial_navigation_system
Not exactly what you're looking for, but spacecraft can use optical star trackers which compare what they see to a catalogue of known stars to determine orientation.
See, for instance:
https://www.rocketlabusa.com/space-systems/satellite-compone...
https://en.wikipedia.org/wiki/Star_tracker
See, for instance:
https://www.rocketlabusa.com/space-systems/satellite-compone...
https://en.wikipedia.org/wiki/Star_tracker
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Yes, there's one mentioned in the article, STELLA. Here's a paper describing it https://adsabs.harvard.edu/full/1999naos.symp..239K
That's an amazing paper:
TL;DR star tracking is a thoroughly solved problem, the hard problem is finding "where is down" without looking at the horizon (which may not be visible). The solution to that is coupling into the ship's inertial navigation system, which still may drift up to an arcminute per hour, but if you feed the star tracker data back into the INS for corrections, it gets better.
TL;DR star tracking is a thoroughly solved problem, the hard problem is finding "where is down" without looking at the horizon (which may not be visible). The solution to that is coupling into the ship's inertial navigation system, which still may drift up to an arcminute per hour, but if you feed the star tracker data back into the INS for corrections, it gets better.
It's wild that the state of art on this is still basically how they left it at the end of the apollo program.
Not sure how you reached that conclusion. The linked STELLA paper describes many post-Apollo improvements, both improvements implemented in STELLA, and star trackers like OWLS and AST 201. And it's not like progress stopped even there; the focus has been mostly on space exploration applications, but as the paper mentions the developments are somewhat applicable for terrestrial use too.
Like others said SR71 etc.
Problem is those fly high enough that the sky is pretty dark and you can actually see stars.
That's not an assumption we can make for the avg plane
Problem is those fly high enough that the sky is pretty dark and you can actually see stars.
That's not an assumption we can make for the avg plane
Somewhat related - https://oceangloberace.com/
A round-the-world yacht race where modern technology is not permitted. (Where 'Modern' = pretty much anything that wasn't in common use in 1970's/1980's).
A fair few of the boats that have taken part had previously run the Whitbread Race in 80's.
GPS isn't permitted outside of emergency situations, and neither are mobile phones/computers (which are sealed in a bag by race organizers for the duration of each leg).
Celestial navigation is required iirc.
Other banned items include: - Carbon Fiber - Digital Music (Only cassette tapes permitted!)
A round-the-world yacht race where modern technology is not permitted. (Where 'Modern' = pretty much anything that wasn't in common use in 1970's/1980's).
A fair few of the boats that have taken part had previously run the Whitbread Race in 80's.
GPS isn't permitted outside of emergency situations, and neither are mobile phones/computers (which are sealed in a bag by race organizers for the duration of each leg).
Celestial navigation is required iirc.
Other banned items include: - Carbon Fiber - Digital Music (Only cassette tapes permitted!)
Curious how navigation at night was not possible without expensive equipment, sounds like they were relying only on starts in the morning and evening? Are the measuring something like angle of those morning/evening stars or their set/rise times with respect to the sun?
It is not true- the authors sound very inexperienced with celestial navigation. There are many ways including the lunar distance method to get a position at night with regular equipment. The math is more complex than a simple noon solar sighting, but it can be done with just a regular cheap plastic sextant and a watch.
It’s also no big deal to go 12 hours with no position. If you know your speed and heading you can accurately estimate your position much longer than that.
Overall, they also made it sound almost impossibly difficult for a large team of professionals, when solo and otherwise short handed recreational sailors have been reliably sailing around the world with celestial navigation for more than a century- through all possible conditions.
It’s also no big deal to go 12 hours with no position. If you know your speed and heading you can accurately estimate your position much longer than that.
Overall, they also made it sound almost impossibly difficult for a large team of professionals, when solo and otherwise short handed recreational sailors have been reliably sailing around the world with celestial navigation for more than a century- through all possible conditions.
Note that they were staying roughly 2 miles within the actual track, while having the bulk of the work being done by a combo of officers and newbs that they had just trained. That's high accuracy standards for celestial nav, not even counting that this is most of other people's first time doing this in anger.
> Curious how navigation at night was not possible without expensive equipment, sounds like they were relying only on starts in the morning and evening?
As a sibling comment notes, it is possible. There are tables for lunar distance:
* https://thenauticalalmanac.com/Lunar_Distance_Tables.html
* https://en.wikipedia.org/wiki/Lunar_distance_(navigation)
* https://www.starpath.com/resources2/brunner-lunars.pdf
The planets Venus, Mars, Jupiter, and Saturn can be used, as well as several dozen planets (lookup tables in an almanac)
* https://en.wikipedia.org/wiki/Nautical_almanac
* https://thenauticalalmanac.com
Two US military videos explaining the theory (ground points/GP, circle of position, etc):
* USAF: https://www.youtube.com/watch?v=UV1V9-nnaAs
* Army: https://www.youtube.com/watch?v=G4DRBi66cOA
The USAF has a video because that's how planes used to do navigation outside of radio range—sextants on the ceiling of the cockpit:
* https://www.youtube.com/watch?v=C7gAiI79nOY
* https://www.youtube.com/watch?v=xc3rAlCDf54
As a sibling comment notes, it is possible. There are tables for lunar distance:
* https://thenauticalalmanac.com/Lunar_Distance_Tables.html
* https://en.wikipedia.org/wiki/Lunar_distance_(navigation)
* https://www.starpath.com/resources2/brunner-lunars.pdf
The planets Venus, Mars, Jupiter, and Saturn can be used, as well as several dozen planets (lookup tables in an almanac)
* https://en.wikipedia.org/wiki/Nautical_almanac
* https://thenauticalalmanac.com
Two US military videos explaining the theory (ground points/GP, circle of position, etc):
* USAF: https://www.youtube.com/watch?v=UV1V9-nnaAs
* Army: https://www.youtube.com/watch?v=G4DRBi66cOA
The USAF has a video because that's how planes used to do navigation outside of radio range—sextants on the ceiling of the cockpit:
* https://www.youtube.com/watch?v=C7gAiI79nOY
* https://www.youtube.com/watch?v=xc3rAlCDf54
And just how expensive is a bubble sextant?
I discovered that real Tamaya marine sextants are available on eBay for $100-150. They were 30x that new.
My understanding is that the sextants are coming from breaker yards in India where the sextants were left on ships and salvaged.
My understanding is that the sextants are coming from breaker yards in India where the sextants were left on ships and salvaged.
I have one I paid $150 for. But bubble sextants are usually only used on aircraft.
> CIC was to notify Lieutenant Commander Stanton if the Essex deviated more than 10 nautical miles (nm) from the planned track.
Pretty impressive! USS Essex would cover 10nm in about half an hour, so not much tolerance for going off-course.
Pretty impressive! USS Essex would cover 10nm in about half an hour, so not much tolerance for going off-course.
So does that mean USN ships are issued with a precision mechanical chronometer for longitude, like John Harrison's original marine chronometer that won the Royal Navy's Longitude Prize?
An electric timekeeping device which is not networked would presumably be good enough for this purpose wouldn’t it? The concern is ewar not so much the ship not having electricity.
In this application, I would also be concerned about resilience in the event of an EMP strike. Not sure a battery-powered quartz timepiece would survive such, even if it would survive a failure of the ship's electrical systems (not sure if that would matter, as I doubt the ship's propulsion could survive such).
If it doesn't require external communication, it's very easy to harden against EMP. Just put it in a Faraday cage.
you can just put a quartz watch in a faraday cage. That'll be more accurate than any mechanical timepiece. Mechanical clocks have a nasty habit of breaking.
Believe it or not, some people still use slide rules and books on trig tables for this very purpose. They use them too. No sense in having them if you aren't competent at using them.
> when celestial navigation is all but impossible without advanced, expensive equipment (i.e., a bubble sextant).
Compared to what the Navy usually steers by, how advanced and expensive are bubble sextants?
Compared to what the Navy usually steers by, how advanced and expensive are bubble sextants?
A new Tamaya sextant can run about $3,000 and Chinese-made Astra sextants are about a third of that. (Bubble sextants aren't used at sea.)
That's the only "expensive" equipment needed for celestial navigation or at least that was the case when I learned it over 40 years ago.
That's the only "expensive" equipment needed for celestial navigation or at least that was the case when I learned it over 40 years ago.
Probably they use a $500,000 computer that fills a room and could be replaced with a $50 Android smartphone with offline Google Maps.
Said Android smartphone relies on clear airwaves and billions worth of GPS satellites.
> analog navigation techniques became relevant again
I'm not sure exactly what methods were used in this navigation exercise, but if they write down numbers with finite precision at any point in the process, then the method has at least some digital component to it. Note that digital means the use of digits, not necessarily any involvement of computers or electronics.
For example, if they take a reading on a sextant, write down a number, and manually transfer it to a coordinate on paper, then that is a semi-digital process. If they take a number and then look up some kind of trigonometric table, that is definitely digital and not analog. But if the navigation process entirely consists of analog mechanical linkages and at no point any number is read out, then I would deem it 100% analog.
> using the radian rule, steering 1 degree off base course for 12 hours at a speed of 16 knots results in nearly 3.5 nm left or right of track (565 yards per hour)
This brings up a laughable feature of the US customary measurement "system", a hodge-podge of units with no coherent logic to it: 1 nautical mile ≈ 2025.371... yards, an awkward number that isn't even whole. This is because 1 nautical mile = 1852 metres exact and 1 yard = 0.9144 metre exact. Converting between these units would be a pain. (Whereas at least 1 mile = 1760 yards exact.)
Analogously, let's say you're piloting an airplane at an altitude of 15000 feet and have a horizontal distance of 7 nautical miles to your landing site. What would be the descent angle if you flew down in a straight line? The answer is not immediately obvious because you can't do trigonometry on different units. Whereas if I said you're 4572 m high and 12964 m horizontal distance away, then the angle is arctan(4572/12964) ≈ 19.4°. And even if distances are reported in kilometres, even a child knows that 1 km = 1000 m.
I'm not sure exactly what methods were used in this navigation exercise, but if they write down numbers with finite precision at any point in the process, then the method has at least some digital component to it. Note that digital means the use of digits, not necessarily any involvement of computers or electronics.
For example, if they take a reading on a sextant, write down a number, and manually transfer it to a coordinate on paper, then that is a semi-digital process. If they take a number and then look up some kind of trigonometric table, that is definitely digital and not analog. But if the navigation process entirely consists of analog mechanical linkages and at no point any number is read out, then I would deem it 100% analog.
> using the radian rule, steering 1 degree off base course for 12 hours at a speed of 16 knots results in nearly 3.5 nm left or right of track (565 yards per hour)
This brings up a laughable feature of the US customary measurement "system", a hodge-podge of units with no coherent logic to it: 1 nautical mile ≈ 2025.371... yards, an awkward number that isn't even whole. This is because 1 nautical mile = 1852 metres exact and 1 yard = 0.9144 metre exact. Converting between these units would be a pain. (Whereas at least 1 mile = 1760 yards exact.)
Analogously, let's say you're piloting an airplane at an altitude of 15000 feet and have a horizontal distance of 7 nautical miles to your landing site. What would be the descent angle if you flew down in a straight line? The answer is not immediately obvious because you can't do trigonometry on different units. Whereas if I said you're 4572 m high and 12964 m horizontal distance away, then the angle is arctan(4572/12964) ≈ 19.4°. And even if distances are reported in kilometres, even a child knows that 1 km = 1000 m.
What a wonderfully pedantic takedown of the conflation of digital and electronic.
Much written, nothing said
Can't tell if that's a compliment or a snark. Do you have anything else to add to the discussion?
Btw, digital logic can be made out of LEGO, fluidics, electromagnetic (not electronic!) relays, steel plates (old railway signaling logic).
Btw, digital logic can be made out of LEGO, fluidics, electromagnetic (not electronic!) relays, steel plates (old railway signaling logic).
It was genuine admiration for sticking to a prescriptive language thing long after that ship sailed.
BTW you can do digital logic on… actual digits/fingers. But when someone says “digital signal processor” that’s not usually what they mean. Sadly.
BTW you can do digital logic on… actual digits/fingers. But when someone says “digital signal processor” that’s not usually what they mean. Sadly.
Knots and nmi are not US customary units. 1nmi is 1 arcminute along the Earth's surface -- 1/60 of 1 degree. Knots are simply nmi/hr. Navigation is really just the application of spherical geometry. Not sure why they're referring to yards, I've never heard of those used in a navigational context.
If you want odd American units you should check out surveying. Units vary by geographical region.
If you want odd American units you should check out surveying. Units vary by geographical region.
> Knots and nmi are not US customary units.
Uh yeah they are. They are _customarily used_ in the US, so they count. They're literally used on all ships and planes. Any unit that is broadly used in the USA is USC. Further, they are indeed listed under the USC page: https://en.wikipedia.org/wiki/United_States_customary_units .
Uh yeah they are. They are _customarily used_ in the US, so they count. They're literally used on all ships and planes. Any unit that is broadly used in the USA is USC. Further, they are indeed listed under the USC page: https://en.wikipedia.org/wiki/United_States_customary_units .
Sorry, I meant that they aren't exclusively US units like US has its own unique pound, etc. Nmi are widely used because elevation of a celestial body can be directly translated to it's Geographical Point's distance from your location with some mental math. Handy.
Go ahead and tune to your favorite station on an analog FM radio without using any digits, please.
Do you mind sharing what that station is with the class, or where it is on the dial?
Do you mind sharing what that station is with the class, or where it is on the dial?
> tune to your favorite station on an analog FM radio ... dial
I mean, when an ad says "Listen to 123.4 FM!", they are literally conveying that information to you digitally; they are telling you the number to tune to.
A fully analog radio has markings to give you a rough guide of where the frequencies are, e.g. 99.0 MHz, 99.1 MHz, 99.2 MHz, etc. When you take the number in your mind and map it onto the markings, you are performing a digital-to-analog conversion (DAC). And because the dial is analog, you can make it fall between any marking you want; there are no steps that you're forced to take.
Meanwhile, a digital tuner would let you tune to 99.1 MHz and 99.3 MHz with nothing in between.
I mean, when an ad says "Listen to 123.4 FM!", they are literally conveying that information to you digitally; they are telling you the number to tune to.
A fully analog radio has markings to give you a rough guide of where the frequencies are, e.g. 99.0 MHz, 99.1 MHz, 99.2 MHz, etc. When you take the number in your mind and map it onto the markings, you are performing a digital-to-analog conversion (DAC). And because the dial is analog, you can make it fall between any marking you want; there are no steps that you're forced to take.
Meanwhile, a digital tuner would let you tune to 99.1 MHz and 99.3 MHz with nothing in between.
A smartphone has all the sensors: tilt, clock, camera. Even compass, though hardly needed. This should be enough to build an app to determine position at sea.
The article opens with:
> Any navigation equipment that used electricity was prohibited, including all GPS sources, the Essex’s electronic Voyage Management System (VMS), and the computer-based celestial navigation software STELLA.
That defines the scope of the exercise.
> Any navigation equipment that used electricity was prohibited, including all GPS sources, the Essex’s electronic Voyage Management System (VMS), and the computer-based celestial navigation software STELLA.
That defines the scope of the exercise.
Those likely aren't anywhere near accurate enough. And accuracy matters when being off by a few degrees can mean hundreds of miles.
Cellphone clocks are quartz crystals. Ordinary quartz crystals have an accuracy of ±10 ppm. That's ±0.001%. That's plenty accurate unless you've been at sea for a long time. 10 ppm of a month is 26 seconds, during which time the equator rotates 12 km (6 arc minutes, 1.9 milliradians). That's not "a few degrees".
Of course if you have a GPS signal you can keep time to within nanoseconds, but I suppose we're assuming GPS is jammed.
Cellphone cameras typically have pixel pitch on the order of 250 microradians, but star trackers routinely deliver attitude information accurate to less than a tenth of a pixel, so 25 microradians, which is 5 arc seconds, not "a few degrees". Calibrating a star tracker for a mass-market camera with its nonlinear distortions is a pain in the ass but can be done. 25 microradians is 160 meters.
SatState from F-Droid shows that my cellphone's accelerometer (tilt sensor) seems to vary by ±0.01m/s² in each of its ≈200ms samples, which is about a milliradian of error, 40× worse than the camera error, about two weeks of clock drift. This isn't "a few degrees" either. Accelerometers can integrate over arbitrarily long periods of time to reduce noise; to reduce noise by 40×, assuming a Gaussian distribution, you need about 1600 samples (320 seconds, 5 minutes and 20 seconds) to average out to the same level as the camera error.
(It's easiest if the phone is sitting still during the averaging time, but both the gyros and the star tracker attitude information permit you to usefully average the accelerometer signal over time even when the phone is changing attitude.)
You probably do need to calibrate the angle between the accelerometer and the camera, but it probably won't change significantly over time for a given phone.
The clock seems like it could be the weak point here, but even the clock is only drifting a few hundred meters a day, and that only produces an east-west error.
Of course if you have a GPS signal you can keep time to within nanoseconds, but I suppose we're assuming GPS is jammed.
Cellphone cameras typically have pixel pitch on the order of 250 microradians, but star trackers routinely deliver attitude information accurate to less than a tenth of a pixel, so 25 microradians, which is 5 arc seconds, not "a few degrees". Calibrating a star tracker for a mass-market camera with its nonlinear distortions is a pain in the ass but can be done. 25 microradians is 160 meters.
SatState from F-Droid shows that my cellphone's accelerometer (tilt sensor) seems to vary by ±0.01m/s² in each of its ≈200ms samples, which is about a milliradian of error, 40× worse than the camera error, about two weeks of clock drift. This isn't "a few degrees" either. Accelerometers can integrate over arbitrarily long periods of time to reduce noise; to reduce noise by 40×, assuming a Gaussian distribution, you need about 1600 samples (320 seconds, 5 minutes and 20 seconds) to average out to the same level as the camera error.
(It's easiest if the phone is sitting still during the averaging time, but both the gyros and the star tracker attitude information permit you to usefully average the accelerometer signal over time even when the phone is changing attitude.)
You probably do need to calibrate the angle between the accelerometer and the camera, but it probably won't change significantly over time for a given phone.
The clock seems like it could be the weak point here, but even the clock is only drifting a few hundred meters a day, and that only produces an east-west error.
But what happens when the smartphone is bricked by an EMP, or hacked by a nation-state virus? Haven't you ever seen Battlestar Galactica?
Can you actually brick a smartphone with an EMP? They don't have much capture area compared to the grid.
Also at that point I would question can you do anything useful with your ship anyway... Considering just how much electronics and automation modern ships run with.
* https://www.npr.org/2016/02/22/467210492/u-s-navy-brings-bac...
Now if only the US (and others) would get their act together and build out a backup system to GNSS. China, for example, has built out an eLoran system:
* https://rntfnd.org/2024/10/03/china-completes-national-elora...
An old USAF video explaining how the theory works (it assumes a geocentric worldview: the Earth is the centre of the universe (but it's not flat :)):
* https://www.youtube.com/watch?v=UV1V9-nnaAs