A First Look at America's Supergun
wsj.com
wsj.com
This is incorrect. Most cartridges are design so that the projectile accelerates for the entire length of the barrel.
A typical US navy marine propulsion reactor puts out 250 MW. This railgun would require about 10% the energy output of such a reactor. A large aircraft carrier might have several cores.
From the 9/11 attack scenario below, impact speed matters (kinetic energy scales with the square of velocity), but chemical reactions pack a great deal of energy. The fuel of the airliners crashed into the World Trade Center towers released some 370x more energy than the impacts themselves, though as thermal energy delivered over roughly an hour, rather than the instantaneous impact.
As an alternative to missiles, the railguns would likely allow for increased firing -- a typical vessel carries fewer than 100 missiles, but could probably carry far more shells (and be capable of firing them).
I'm wondering at what point increased speed means you're simply punching holes through things without actually inflicting damage -- it's the transfer of energy from shell to structure that matters. If you're targeting a deeply buried concrete bunker, this is appropriate. Residential or commercial buildings, cars, etc., will to a large extent simply get very well ventilated (though you might not want to be in the immediate enting area when this happens). Matching shell structure to target likely matters.
Also, I believe they are (were?) looking at the Zumwalt destroyer for this weapon, which actually only has 78 MW of power output.
It's traveling 4K mph or about 1800m/s, let's assume since its 24in long and largely tungsten it has a mass of around 60kg. 1/2 * mass * velocity ^2 means it needs 97.2 megajoules of power. That's about 4 seconds for a 25MW reactor, so I guess you're right something smaller could fire it less rapidly, though the one every 6 seconds they cite as desired would require that much power.
Other tanks, infantry, passers by will be glad for it.
Considering the history of the world, and considering that wars are happening in other countries all the time, I'd personally say that thinking war isn't possible is incredibly naive and unrealistic.
Surely anyone looking at history learns it's not a matter of if, but a matter of when. Perhaps (hopefully!) it won't be in our lifetimes, but it's reasonable to want to stay even with or ahead of the capabilities of other powerful militaries, including ones we are currently allied or at peace with.
Can you genuinely state with certainty that humanity is over fighting major wars -- that we've evolved past that?
The answer is simply no, we haven't gotten past that point and likely never will. So in that context we should be developing weapons to fight and win wars against the most likely of threats.
The most likely threats happen to be China and Russia.
That's why I don't believe in "a world without nuclear weapons" - a world without nuclear weapons is a world in which the next world war is imminent.
That said, something is going to happen in the south China sea. But no rational actor would ever start a nuclear war. That leaves cold-war style local dominance battles. Not nice, but not a major war either.
In terms of China, that means the west coast.
Lower wages, and little to no environmental protection. ... and a government that will one day nationalize everything, surprising a bunch of would-be Masters of the Universe on Wall Street. Oh, the irony when these clowns talk about "confiscatory" taxes, then get into bed with the Chinese.
Any consideration that rather than mercantilism discouraging war, there is just a small chance that the threat of mutual assured destruction might be a disincentive for (rational) players to avoid total conflict?
I'm actually more moderate than the above may sound (e.g. - I think we spend a bit too much on the military), but I am SOOOOOOO tired of "free traitors" spouting their ... stuff ... which only benefits the very wealthy (at least until the host dies from their parasitism).
Vegetius's adage "If you desire peace, be prepared for war." applies just as much today as it did in the time of the Roman Empire. I only hope that the Western powers are prepared enough.
> Or is just about using military might as a political & diplomatic tool?
Military might is always a political tool. One of the most famous, enduring descriptions of war, by arguably its leading theorist, 19th century Prussian General Carl von Clausewitz, is 'the continuation of politics by other means'.
Sometimes you threaten with your military power, sometimes you fight, but either way it's always for political reasons. Nations pursue war to obtain political goals and wars end with political settlements. Sometimes those settlements are vastly unbalanced, such as total surrender, but they're still political - 'we agree that you will govern us' - otherwise you keep fighting. When nations forget that then they waste blood and treasure - look at the U.S. invasion of Iraq, which lacked a political aim and thus found itself in a quagmire after the military goal, the overthrow of Hussein, was achieved. That lack of political resolution left a political vacuum which persists to this day, and which ISIL, Iran, the Kurds, and others have tried to take advantage of; the wars there will end when there is a stable political equilibrium.
> Do they believe there is a realistic chance of war with these countries?
RUSSIA is mostly bluster but they do have some capability; they are a threat to small, poor neighbors; and of course they have nuclear weapons. They can cause pain but would be absolutely insane to fight a real war with NATO (though that hasn't stopped some people). Their current strategy is to approach the line but not cross it; e.g., occupy neighboring parts of Ukraine and Georgia but stay away from NATO borders.
The foundation of military power is economic power; money buys more and better weapons (and friends too). Russia can't possibly afford to compete with NATO; they can't really afford their current operations, which are on the cheap (the Ukrainian province of Crimea was conquered with a small number special operations soldiers, for example). Annual economic output (GDP) of NATO, Russia, and selected countries says it all:
* NATO: $37 trillion
* U.S.: $17 trillion
* Germany: $3.9 trillion
* UK: $2.9 trillion
* Canada: $1.8 trillion
* Russia: $1.1 trillion (with a shrinking population and also a shrinking economy based on mineral wealth, not technology or industry)
CHINA is a much more serious issue. Remember the economic foundation of military power. China's economic output likely will surpass the U.S.'s in the next decade. With four times the U.S.'s population, it's not crazy to imagine China's economy being twice the size of the U.S.'s in future decades. Then what happens?
Much history has been studied and written about what happens when a rising power overtakes the existing dominant power. The result usually is war. Like an old incumbent tech company, the old dominant power can't see their obvious situation and tries to hold on to their historical position; the rising power refuses to remain subordinate.
The last time it happened, in the late 19th and early 20th centuries, the U.S. was the rising power and the European powers were the incumbents. To the Europeans the U.S. was about as benign as they could hope for: A relatively peaceful democracy, sharing the same values and culture, filled with European immigrants, and a great trade partner who enriched them all. Broadly speaking, they accommodated the rise of the U.S.; by the end of WWII, with Europe devastated by two massive wars, the transition was complete. According to one account I read, during one international security crisis in the 50s (Suez?) the UK government actually called the US and said, effectively, 'we can't handle this any more, it's your job now'. The U.S. has been primarily responsible for global order ever since.
China seems much less benign, a dictatorship that is openly threatening everyone from its neighbors to the U.S. to European nations. Many nations view the U.S. as a relatively very benign hegemon, actively seeking alliances and U.S. forces based in their countries. Another common pattern when a new power arises is that the others ally against them as a balance. Right now that seems to be happening around China, with Japan, Vietnam, the Philippines, Australia, India, S. Korea and others busily forming stronger bonds with the U.S. and among themselves in response to China's bellicosity.
But it's a very long game, one that will last a generation or more, so nobody knows.
That's not going to happen. China is replicating the Japan scenario. This is not only peak fear over China, but it's also peak China when it comes to their partially fake economic boom (fueled by the greatest debt binge in world history).
The US now has an $18 trillion economy. China is nearing $11 trillion.
It makes no sense to do this, but I'll do it for convenience - let's assume China never has a recession or depression (given their economic mismanagement since the easy growth faded, that's laughable, but anyway).
China grows at 4% for 30 years. The US grows at 2% for 30 years. The US ends up at ~$32 trillion. China ends up at ~$35 trillion. That's China's best case scenario, and it takes them three decades just to catch the US. The far more likely scenario is China has 20 years of stagnation as they struggle to claw their way out of extraordinary sums of debt, defaults, bankruptcies, vast unemployment and broad economic mismanagement under a failed central planner system - not to mention China has half a billion subsistence farmers that will never see their standard of living climb meaningfully in real terms because China has no jobs for them (and the robotic / AI revolution will guarantee they never have jobs), those people will not be very happy over the next 30 years.
Realize that hoping for that is hoping for hundreds of millions of people to be mired in poverty for generations more.
What I hope is that China achieves political reform and becomes a democracy, and all those people have freedom, self-determination, and prosperity. Despite China's protestations, many countries of many different cultures have done it with great success: Japan, S. Korea, Taiwan, and Hong Kong are examples right on and even within China's borders. All the most prosperous, secure countries in the world, almost without exception, are democracies.
Democracies almost never go to war with other democracies; it's not much of a threat. Also, liberty and self-determination are Western values; what you describe is the antithesis.
That depends on how you measure it, and especially on how you convert Chinese currency, renminbi (RMB), into dollars so you can compare the two economies on the same quantifiable scale. There are two widely used methods with much different results for the size of China's economy:
* $11 trillion: That number is yielded The "nominal" method, which is based on how many RMB you can buy with a dollar on international currency exchanges, such as if you did it at your bank (and they gave you a fair rate without exorbitant fees).
* $19 trillion (already larger than the U.S. economy): That number is yielded by the purchasing power parity method (PPP), PPP calculates the RMB-to-dollar conversion based on how much it would cost to purchase the same set of goods locally in each country. (For example, if a gallon of milk cost 10 RMB in China and $1 in the U.S., the PPP conversion rate for milk would be 10/1. Needless to say, economy-wide PPP is far more complex.) Goods generally cost much less in China, a much poorer nation, so money goes further.
Which method applies better to funding a military? I suppose it depends on to what degree transactions are local, such as paying troops and making military assets locally, and to what degree components and goods are purchased from other countries. Certainly China has large domestic military industry.
Also, both numbers depend on how much you trust Chinese government economic statistics, which are widely suspected of being overstated.
> That's not going to happen. China is replicating the Japan scenario.
I've heard some say that, but nobody can predict these things with anything like the certainty in the comment above (which I'll take as hyperbole). China certainly has economic problems, and a government whose legitimacy was based on economic growth for 30 years. Now they are shifting back to ideology (communism and nationalism) and raw oppression.
Even the Wall Street Journal has science/engineering illiterate idiots writing for it? If engineered properly, a conventional naval gun will also continue to accelerate its projectile all the way down the barrel. Why does this idiot think there are various guns that have long barrels? It's to give expanding gasses a longer time to accelerate the projectile.
Not knowing what you don't know can literally cost untold treasure and many millions of lives. There are tons of examples of this in history. I'm pretty sure we're not doing so great a job teaching that either.
And yes, it even goes to examples of basic Computer Science knowledge on HN!
Also, personally I don't have any other idea how to fix journalism than calling them out every time, and calling them out hard.
Removing words with high emotional charge but low signal (such as "idiot") will increase the quality and effectiveness of the comment. Others will view the comment more favorably, and any additional discussion is likely to be more productive this way.
P.S. Either way, the house rules here are to "be nice". You can argue (and many do in this thread) whether this is a good policy, but it is the policy.
This serves as yet another visible instance (out of countless) that shows they have no fucking clue what they're writing about and they don't even care.
So the barrel lasts just over an hour and a half?
Today's 5" guns have to have their barrel replaced every ~7000 rounds anyway (source: http://www.navweaps.com/Weapons/WNUS_5-62_mk45.htm ).
I suspect the Navy have some records on firing rates achieved in actual battle situations.
The relationship between theoretical firing rate and actual firing rate is often distant. You might find it more useful to read this as a weapon capable of firing not more often than once every six seconds, and having an effective barrel life of 1,000 rounds.
Those 1,000 firings could well be spread over months or years.
Edit: Apologies, basic mistake, mixed up power with energy. Thanks for correcting.
That's not how power works. Power is energy/second, so if one each firing requires 25Mw, firing every round requires 25Mw.
Edit: Although after doing some calculations, firing 1000 shells would require 22 billion joules of energy, which is about the same as the energy released during nuclear fission of three grams of uranium.
Of course, only a small portion of uranium in a reactor core is converted to something else. After that, they replace the fuel as its output drops a bit.
Disclaimer: I don't know enough to check the "grandparent" post's math. I'm assuming the calc is right in that it's the fission energy, and not total destruction of matter E=mc^2 / matter-antimatter style.
Learning about how expensive high-tech weapons are never ceases to blow my mind. 50k for a single bullet -- equivalent to 1 yearly median US salary. 10m for a missile -- the price of a luxury mansion or the value of a decently successful startup.
You are correct, most bullets fired in an infantry engagement do not in fact hit their targets. Assuming a target can even be seen. Bullets are cheap and useful for all manner of things, such as keeping the enemy's head down long enough for you to get into position to use a few bullets and kill him. ;)
But then again I feel like to do deals with the govt it requires jumping through hoops.
That's a reasonable rule of thumb, but it's kind of funny to apply it to the weaponry of large scale modern militaries, since those almost certainly couldn't exist without the very governments that makes their costs inflated.
On the other hand, it won't be something you can line a ship or a plane with, so yeah... Always shoot first.
A rail gun is as satanically simple in theory as it is satanically hard to engineer.
A coil gun won't have this problem, but unfortunately the magnetic fields are harder to get than the electric ones.
We know the impact a hijacked jumbo jet can have on buildings...now imagine being able to sustain that level of destruction at a rate of 10 times/minute with hardly any power or material consumption.
Sorry, but it sounds like not all readers on this website know the difference between kinetic energy and momentum. Here's a K-12 level website: http://www.batesville.k12.in.us/physics/phynet/mechanics/ene...
It has a very illustrative question: Would you rather be hit by a 1000 kg vehicle going 1 meters per second, or by a 1 kg meatball going 1000 meters per second?
Huh? Energy and momentum are two _different_ quantities related to the movement of an object. I was talking about using the energy _instead_ of the momentum as an indicator of damage.
On the other hand, as another poster already said, you should compute energy. That goes with velocity squared, so it will be way higher these projectile, compared with a jumbo jet.
Edit: as another poster said, you also should have said miles/hour. That gives you http://www.wolframalpha.com/input/?i=25+pounds%2F2+*+((4500+...), apparently about what a Samsung S3 uses in a year (what am I doing wrong? http://www.wolframalpha.com/input/?i=25+pounds%2F2+*+((4500+... gives me 6.374 kWh. Seems a tiny amount)
Additionally, small really fast projectiles can more easily pack a lot of kinetic energy relative to a larger, more slowly moving projectile because kinetic energy is proportional to velocity squared. It is not so easy to pack a lot of momentum in a small really fast projectile because momentum is just directly proportional to velocity.
It's the jet fuel that melts steel beams.
Kinetic energy = 0.5 * m * v^2
The energy density of kerosene (jet fuel) is about 33 MJ/l
We can compare the impacts of American Airlines Flight 11, a Boeing 767-233ER weighing about 180 tonnes, with about 38,000 l of fuel aboard, with the energy capacity of that fuel, comparing both to barrels of oil equivalent, using GNU Units:
You have: 0.5 * (180 tonnes) * (748 kph)^2 You want: barreloil * 0.63494668 / 1.5749354
And for the fuel (I'm assuming 1kg/l for kerosene, this is slightly high, but the fuel quantity isn't precisely known. Rough accuracy is sufficient.)
You have: 0.907 * 38 tonoil You want: barreloil * 235.81404 / 0.0042406296
The energy of the plane's fuel is roughly 370x that of its kinetic impact.
Which isn't to say that it's not useful, but it probably isn't useful for the same applications. Something like this wouldn't be my top choice for large-scale destruction such as knocking down buildings. I sure as hell wouldn't want to be in a bunker or tank that has one of these things bouncing around inside, though.