During their service in WWII, the 16-inch guns on the Iowa-class battleships had a life of about 300 rounds. They didn't reach their current 3500-round lifetime until we figured out polyeurethane bags in the 70s. So 1000 rounds is solid. https://en.wikipedia.org/wiki/Armament_of_the_Iowa-class_bat...
Have you ever seen, in person, the scale of a 16 inch 50 Caliber gun? They're not field swappable. The barrel is about 67 feet long and weighs 120ish tons.
Think of it instead as: The ship can fire 10x as many rounds before needing to resupply as it can with today's technology. The resupply also happens to involve replacing the barrel.
In terms of firepower and reusability, you should compare these to missiles rather than guns. (Each round could sink a ship.) The barrel is an expendable component.
What's the scenario in which a vessel would be faced with 1,000 targets (per barrel) in an engagement?
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.
It's kind of like with automatic weapons - some of them are capable of firing so fast that they'd eat through your magazine in a second or less. That has little to do with how they're actually used though.
Might a bigger challenge be the power source? If each firing requires 25MW, then 1000 shells would require 25GW, which is equivalent to the output of several large nuclear power stations.
Edit: Apologies, basic mistake, mixed up power with energy. Thanks for correcting.
> If each firing requires 25Mw, then 1000 shells would require 25Gw
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.
Thanks. That helps with my original question - how portable will this be? If it just needs a very small nuclear reactor with a tiny amount of fuel, then they should be able to have a power source "that generates 25 megawatts" and can "fire 10 times a minute through a barrel capable of lasting 1,000 rounds" on a ship. But what about a truck? Having a weapon with a 125 mile range isn't necessarily all that great if it is too big and heavy to get within 125 miles of most of the things you want to shoot at.
I look forward to the day that the great weapons race is for more weapons like this that aren't radioactive, biological, or otherwise impact the environment beyond the war itself.
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.
The destructive power of this gun comes from the energy of its momentum (mass x velocity) -- all the energy expended to accelerate it needs to go somewhere when it reaches its target. Same principle as a handgun. The difference is in how the projectile is accelerated.
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?
Thread-placement wise, I thought it was the best place to post the message to maximize salience and relevance. Do not be offended if there is no need for you to be offended.
I'm not confusing anything, but I wasn't trying to be scientifially rigorous, either. By "energy of the momentum" I was referring, admittedly imprecisely, to the fact that the kinetic energy is a function of the momentum. Or, to be precise, E_k=p^2/2m. At least as I understand it.
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.
That impact wasn't as large as your remark make it appear to be. The twin towers didn't collapse on impact, they collapsed from the energy released by burning the fuel in the planes and the burnable stuff present in the planes and the towers themselves (in what proportions, I don't dare take a stab at)
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.
Your calculation is wrong. You are using 4500 miles/second instead of 4500 mile/hour as the velocity.
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.
The impact of a jumbo jet on a building is relatively modest. Not good to those on the directly affected floors, but even high-speed direct impacts are sustainable.
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.
It's not just how much momentum is in the projectile, it's also how much energy is transferred to the target. A jumbo jet at cruising speed is likely to transfer almost all its energy into a large portion of virtually anything it hits. A small projectile traveling at 4500mph is likely to either transfer a lot of energy into a small area, or punch a hole straight through and keep on going until it hits something else.
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.
Cool, but also something that makes war even more scary. You'd use to have all sorts of things to protect you; there isn't anything that can protect you from this once aimed at you (except a pre-emptive EMP; providing they have no shielding for it). Feels weird knowing there is nothing that can protect you from it.
In conventional guns, a bullet loses velocity from the moment the gunpowder ignites and sends it flying. The railgun projectile instead gains speed as it travels the length of a 32-foot barrel
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.
This is how I genuinely feel about the level of scientific illiteracy our society has fallen to. We literally have people at an executive level who are functionally illiterate in science, making decisions on the basis of their ignorance. (The editors of the WSJ could be seen as examples of this.) "Solar Freakin Roadways" got almost $2 million from the public. Are we functioning with a viable educational system for a complex technological democratic society? Heck no. Even the people in charge are riddled with ignorance on basic levels.
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!
I think that calling people names here was making the comment much closer to what 'stcredzero actually thinks. I.e. it boosted accuracy and clarity of the comment.
Also, personally I don't have any other idea how to fix journalism than calling them out every time, and calling them out hard.
You literally used "accuracy" and "clarity" as synonyms for intensity of emotion. Under that logic, everything becomes a screaming match, and the comments devolve into a competition to see who's feelings are the most virulent.
I meant something else. When you write a comment, you transcribe your thoughts and feelings into text. That text may or may not be close to what you actually think - e.g. to the words you use in your internal monologue. In this case I think the word choice serves to portray the actual thoughts and emotions of the author more clearly/accurately.
High quality comments are written to convey an idea or present an argument (low quality comments are often written to make the writer feel good about themselves without conveying any meaningful idea).
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.
I don't disagree with the sentiment, although I think you go a little too far - not everyone can be an expert in everything, and journalists have a genuinely hard problem of trying to a) learn something well enough and quickly enough to get it to print within a few hours, and b) manage to reduce it to a form that the average reader will understand. These are genuinely hard problems.
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.
I'd otherwise agree, but this is journalism. Even here people seem in need to be reminded that the quality level of news media, even those reputable ones, fell down to ridiculously low levels.
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.
> In conventional guns, a bullet loses velocity from the moment the gunpowder ignites and sends it flying. The railgun projectile instead gains speed as it travels the length of a 32-foot barrel..
This is incorrect. Most cartridges are design so that the projectile accelerates for the entire length of the barrel.
Based on the fact that they state the railgun is different in that it gains speed over during the time in the barrel, it seems like the author just doesn't gun physics.
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.
Never, more speed is good because they can program the projectiles to break apart before impact with soft targets. The limiting factor is air resistance, greater initial speeds result in more energy wasted.
Also, I believe they are (were?) looking at the Zumwalt destroyer for this weapon, which actually only has 78 MW of power output.
Does power really matter? 25MW instantaneous power vs continuous/average power are different things. With modern clever power electronics you could get pretty high instantaneous power from a lower powered source. The exact energy vs time curve and desired fire rate has to be utilized to make any effective prediction I think.
The article does mention advances in supercapaciter design as one of the enabling technologies, but I suspect just charging the things requires a ton of power. Let's do some back of the envelope physics with what we know (and reasonable ball park guesses when we don't)!
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.
In war rendering things unusable is as good as completely destroying them. Also, secondary explosions set off by the impact/spaulding can be a Very Bad Thing: https://youtu.be/750jAbdf-I8
Missile defense by the railgun is at least a decade away, but Pentagon officials believe the weapon’s projectiles can be used much sooner. They are filled with tungsten pellets harder than many kinds of steel, officials said, and will likely cost between $25,000 and $50,000, a bargain compared with a $10-million interceptor missile.
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.
Consider that an infantry rifle will cost at least $1,000. A rail gun round seems like a bargain if it costs 25-50 rifles-worth! The risk to the military personnel is also lesser than using small arms rifles.
I've heard that the hit ratio of modern small-arms battle is very low. The railgun would be a much more assured strike than sending even many humans to do the job. The railgun isn't just replacing rifles, bombs, and missiles, it is replacing humans! Think of how much a wounded soldier will cost a country over the course of their life, at least if the country gives a damn about vet benefits. Of course while likely quite precise (I'd guess 10 meter CEP), it is still a very powerful weapon that could cause a lot of collateral damage. Human soldiers still have applications.
Artillery isn't typically used to do infantry jobs. We call that a "war crime". Unless it's us doing it, then we call it "collateral damage".
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. ;)
I'm sure it could be a lot cheaper, usually government contracts are inflated. Seems like everyone increases the actual costs to extract more money from the government. Not to mention the govt changes requirements constantly (F-35).
But then again I feel like to do deals with the govt it requires jumping through hoops.
> I'm sure it could be a lot cheaper, usually government contracts are inflated.
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.
I think the GP is not saying the problem is with government - it's with the people who take government contracts and inflate the costs to take more money for themselves.
This projectile is actually significantly more sophisticated than a bullet. It is going to require a significant amount of guidance/control to have any level of accuracy at 100 km. That is the real cost driver, and it saves money compared to a missile because it gets all of its kinetic energy from the gun.
Indeed, thanks for the hint. I actually wanted to note, that electromagnetic guns is an old idea. (Even I came to it once, but of different design; and was surprised when discovered it to be already studied - in that article though they said this idea turned out to be impractical).
It's a bit fascinating and scary how casually they talk about the weapons of China and Russia, and what we need to counter them. Do they believe there is a realistic chance of war with these countries? Or is just about using military might as a political & diplomatic tool?
I think most people generally believe that, yes, war with other countries is possible.
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.
> Do they believe there is a realistic chance of war with these countries?
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.
The weapons of China and Russia aren't going to be confronted only in China or Russia. At any rate, it's always good to negotiate from a position of strength.
Let's look at this another way: Do you think that there will never be another major war? Like never, ever, ever again?
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.
No, we haven't evolved past major wars, but nuclear weapons have made them impossible to win. That is something new under the sun.
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.
You won't find any official government statements about this, but supposedly senior US military officers have been saying privately that they think an air and naval war with China is inevitable within the next few decades. They see China today as being roughly equivalent to Japan circa 1930 as a competing power. So they've been quietly reorienting the military to fight that conflict. I hope they're wrong. We need to find a way to coexist.
Not going to disagree with you. The only people who benefit from offshoring are the people making the money and the areas with the best ports to import from those areas.
Right. It's not like electronics manufacturing was moved to China in the 90s because of a shorter supply chain or superior expertise.
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.
Apparently many others hold that belief, as well, to the extent that it is downright offensive to them to suggest otherwise.
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).
A more likely consideration in China and Russia are one of the few arms suppliers out there. So, even if we don't fight them it's likely we are going to fight older versions of their gear.
Strategically, China is our only real rival and threat (Russia is a secondary power at best). It's in our interest, and our allies interest, that we be prepared to win a war with them, even if we prefer not to fight them.
The re-annexation of the Crimea and construction of military outposts on artificial islands in the South China Sea show that neither of the two powers have lost their ambitions.
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.
As an amateur with a hobby in foreign affairs, I can say the following based on reading many experts for years but with no expertise of of my own:
> 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's economic output likely will surpass the U.S.'s in the next decade.
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.
I mean, I hope you're right and that China will prove to be a paper tiger, as it were, but I'm not so confident that it will be so, and it therefore seems prudent to spend the money needed to have a military capable of containing them.
> I hope you're right and that China will prove to be a paper tiger
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.
True, but I'm not going to starve the rest of the world so that I feel safe. That seems like a definition of evil.
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.
> The US now has an $18 trillion economy. China is nearing $11 trillion.
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.
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[ 3.6 ms ] story [ 180 ms ] threadSo 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.
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.
On the other hand, it won't be something you can line a ship or a plane with, so yeah... Always shoot first.
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.
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.
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.
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'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.
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.