Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

US Navy's Railgun Now Undergoing Tests in New Mexico

thedrive.com

Post reply on HN
Print view View original

71–80 of 277 posts

Re: US Navy's Railgun Now Undergoing Tests in New Mexico

#71

Post by JDulin »

JDulin wrote: post #70
pneill wrote: post #51

Does anyone know why there is a flash of light and a puff of smoke when the gun fires? Since it's electromagnetic, you'd think you wouldn't see anything.

A combination of three things: 1) The flash is air in contact with the super-hot rail ionizing instantaneously from the heat, and becoming plasma. 2) Friction (From the projectile against both the rail itself, and air) producing vast amounts of heat, which then a) causes water vapor in the air to flash to steam b) produces smoke from burning metal I am not sure how much of the smoke is from 2)b), because I'm assuming…

Ah! Some good answers in the rest of this thread noting that this gun vaporizes its sabot - That's probably the biggest source of smoke

Re: US Navy's Railgun Now Undergoing Tests in New Mexico

#72

Post by hollerith »

bin0 wrote: post #50
minikites wrote: post #42

Earlier quoted context omitted.

>Condemn the action, not the tool. So it's fine to stockpile chemical weapons as long as we don't use them because they're just a tool?

We've been stockpiling nukes for a half-century, and only ever used two. I would contend that the two which were used were a net benefit in terms of what it would have cost (in both American and Japanese lives) to invade the islands. Of course, the threat is only good if the nation doing the threatening is willing to use it, so the merits of stockpiling are still arguable. With that said, they were something of a too…

> the two [nukes] which were used were a net benefit in terms of what it would have cost (in both American and Japanese lives) to invade the islands.

There was no need to invade the islands. For the last year of the war, the Japanese had severe problems importing supplies. A significant fraction of their imports were coming in on tiny wooden ships: larger ships and steel ships would probably be sunk by US submarines or US aviation before making even a single delivery, and Japan had almost none left. The US could have simply waited and gotten the same result that they got with nukes. The reason it did not wait is worry that Stalin would invade northern Japan.

The first sentence of the wikipedia page on mining in Japan is, "Mining in Japan is minimal because Japan does not possess many on-shore mineral resources". Although the Japanese homeland does have coal reserves, the extraction costs are much higher than they are in the US and in Europe. It has and had very little petroleum reserves. The wikipedia page I mentioned says that "in 1941, Japanese petroleum production was . . . 0.1% of world petroleum production" and that the US produced about as much petroleum in a day as Japan did in a year.

Re: US Navy's Railgun Now Undergoing Tests in New Mexico

#74

Post by rmcrx »

module0000 wrote: post #61

Sadly, news these days involves a lot of "we've invented , to kill people that disagree with us". Often the word "disagree" is replaced with "undermine" or "threaten". It's all the same human-life-ending bullshit. I don't feel at home in this world any more. When I was 18, I enlisted in the armed services and "did my part" as people often say. What a fucking mistake, I'm humiliated and embarrassed every single day to…

[flagged]

Re: US Navy's Railgun Now Undergoing Tests in New Mexico

#75

Post by ohaideredevs »

vosper wrote: post #56
ohaideredevs wrote: post #54

Earlier quoted context omitted.

"2) Railguns are going to be the equivalent of WWII naval cannon -- They won't be nearly as important as something else." Railguns would completely surpass missiles for StS warfare, which can be intercepted by other missiles, whereas a railgun shot cannot at this time.

Except maybe not these hypersonic missiles, which were discussed here just the other day? https://news.ycombinator.com/item?id=20227021

Well aware. The radar signature is still significantly smaller for the projectile. Also, note how hard-kill tank defense systems work better on missiles/rockets than SABOT.

P.S. Zircon is probably vaporware.

Re: US Navy's Railgun Now Undergoing Tests in New Mexico

#76

Post by phreeza »

clarkmoody wrote: post #22
sdinsn wrote: post #14

Earlier quoted context omitted.

It's just a logo, I think the Railgun only can get to 100 miles or so (at the moment).

Someone a little better with aerodynamic drag computations could do a quick back-of-the-napkin to figure out the maximum range of something fired at sea-level going Mach 3,4,5,6,etc. The biggest issue I see is just vaporizing the projectile on launch, so there would be an upper bound on muzzle velocity based on projectile material properties.

As long as the projectile travels fast enough that there is ablation, you can use the Newton approximation [1] to get a rough idea. Using densities for uranium and air, and a projectile length of 1m, that gives a range of 15km. Of course when the bullet slows down, that is significantly extended.

[1] https://en.m.wikipedia.org/wiki/Impact_depth

Re: US Navy's Railgun Now Undergoing Tests in New Mexico

#77

Post by brink »

oblongx wrote: post #67
module0000 wrote: post #61

Sadly, news these days involves a lot of "we've invented , to kill people that disagree with us". Often the word "disagree" is replaced with "undermine" or "threaten". It's all the same human-life-ending bullshit. I don't feel at home in this world any more. When I was 18, I enlisted in the armed services and "did my part" as people often say. What a fucking mistake, I'm humiliated and embarrassed every single day to…

?? Sadly, news these days involves a lot of "we've invented , to kill people that disagree with us".....The modern-day me wishes I could go back to the 18-year-old me and

What's a pacifist with militaristic sentiments? A hypocrite? A doublethink?

Re: US Navy's Railgun Now Undergoing Tests in New Mexico

#78

Post by SEJeff »

minikites wrote: post #68
SEJeff wrote: post #65

Earlier quoted context omitted.

Do you not see that materials science from high performance cruise missiles might work its way through other uses of materials science such as structural engineering and bridges? Bridges can be used to hold tanks, does that mean all bridge engineers are bad?

There's no way other than weapons engineering to make those discoveries?

In the same vein, as an industry, pornography really improved computer storage density and video codecs whereas electronic trading really improved the tech to reduce networking latency. Virtually all engineering benefits from other engineering that came before it. There are plenty of other ways, but this is how it is. Most all of what NASA does or has ever done has directly benefited the Department of Defense. Does this mean we should shut down NASA because it helps the military make more efficient missiles or spy satellites? When does this silly argument end.

Re: US Navy's Railgun Now Undergoing Tests in New Mexico

#79

Post by losteric »

minikites wrote: post #41
SEJeff wrote: post #37

Earlier quoted context omitted.

Really hard engineering pushing the limits of physics and materials science is fun, killing people is not.

Do you genuinely see the same virtue in the engineering of a bridge and the engineering of a cruise missile?

Virtue? For me, it's much more basal than that.

Railguns, rockets, explosions, lasers... fast cars, fighter jets, massive supercomputers... all impressive engineering "magic" that spark some childish awe in a certain type of person.

As an adult, I know the why behind the technology. That "awe" grows into "awesome" or "awful"... but it always starts awe.

Re: US Navy's Railgun Now Undergoing Tests in New Mexico

#80

Post by Robotbeat »

travisporter wrote: post #9

Is there any active research on this technology for non-rocket launch systems?

The closest I'm aware of for active research is SpinLaunch: https://www.nextbigfuture.com/2018/02/spinlaunch-is-using-la...

...but isn't using rails. Rails are kind of a pain anyway as they have a habit of eroding.

Post reply on HN