rail gun vis

[cassandra and sara's daddy]

bet it leaves a mark

http://fredericksburg.com/topics/railgun-video-navy-dahlgren/index_html

[Gowen]

That was neat.

[freakazoid]

I'm currently stationed where they are testing that. You can hear, and sometimes feel, when they shoot it. Unfortunately our class didn't take the opportunity to see it. :(

[roo_ster]

He'd best carry a change of undershorts.  And a baggie to put the old ones in put the few bits of him they find after impact.

[cassandra and sara's daddy]

I'm currently stationed where they are testing that. You can hear, and sometimes feel, when they shoot it. Unfortunately our class didn't take the opportunity to see it. :(

they let you outa your cage and you wanna see the town let me know

[RocketMan]

Meh.  Where's the ACS troops?  And no Posleen.  It is Fredericksburg, afterall.

[cassandra and sara's daddy]

http://fredericksburg.com/News/FLS/2010/122010/12112010/593845


8 times the speed of sound

[geronimotwo]

downloaded from wikileaks?  

how many frames per second to smoothly catch mach 8 in slow-mo?

any idea how large is the projectile? material?  is the casing used bacause the projectile is non-magnetic or just to stabilize during acceleration?

saw the video first,  just read the article.  interesting how they measure velocity in joules.  lol.

[AmbulanceDriver]

from the article:

The Navy hopes to have a working 64-megajoule railgun aboard ships within 10 to 15 years.

Holy Crap!  Now I know it's not necessarily gonna scale up velocity wise, but let's assume for a moment that it does.  That means the projectile would be traveling at 16 times the speed of sound!  At sea level, that would be in excess of 12 thousand miles per hour.....  We're approaching orbital speeds here!

Now, let's say for sake of argument that a doubling in power only results in a 50% increase in MV...  That would still be over 9000 miles per hour.... 

Holy Crap.

Oh, and nobody let Rev read this article.  He'll be building one in his basement (if he hasn't already).

[Tallpine]

Holy Crap!  Now I know it's not necessarily gonna scale up velocity wise, but let's assume for a moment that it does.  That means the projectile would be traveling at 16 times the speed of sound!  At sea level, that would be in excess of 12 thousand miles per hour.....  We're approaching orbital speeds here!

Now, let's say for sake of argument that a doubling in power only results in a 50% increase in MV...  That would still be over 9000 miles per hour.... 

Holy Crap.

Oh, and nobody let Rev read this article.  He'll be building one in his basement (if he hasn't already).

Too fast and the projectile will just burn up going through the atmo.

[AmbulanceDriver]

Too fast and the projectile will just burn up going through the atmo.

Of course, the other option is to keep velocity the same and double the mass...

Wait...

dang it, where'd I leave my kinetic energy formulas.

hold on...

Ok.  So for a 32MJ shot, assuming Mach 8 from the article, you have a projectile of mass 8.6kg (roughly).

Now, let's put that as a 64MJ shot, and see what we can do..  

If you keep the projectile mass the same, you can increase velocity to nearly Mach 12...  11.5ish

Or, if you keep the velocity the same, your projectile now has a mass of 17.2kg...

In either case, that's a helluva lot of KE packed into a relatively small package........

As an example, that'd be like getting hit by 2-ton car at nearly 600 mph

[MillCreek]

I am reminded of the 'flying crowbars' theory of orbital weapons.  The kinetic energy does all the work.

[AmbulanceDriver]

I am reminded of the 'flying crowbars' theory of orbital weapons.  The kinetic energy does all the work.

Aka God Rods

[cassandra and sara's daddy]

Too fast and the projectile will just burn up going through the atmo.

they are already starting to burn up the aluminum projectiles. i think the sabot is ferrous and you can see it glowing and in pieces

[Matthew Carberry]

If they can increase the rate of fire, a LOS weapon of that speed with a suitable targeting system makes flying aircraft into its target envelope a dicey prospect.

[Devonai]

I've started to think about weapons systems like this for my own science fiction.  After reviewing the info on Atomic Rocket, this is what I came up with:

http://devonai.wordpress.com/2010/12/02/miscellanea-mphi-m24c-mass-driver-cannon/

I like the idea of using osmium as a slug.  Any thoughts on this?

[erictank]

Meh.  Where's the ACS troops?  And no Posleen.  It is Fredericksburg, afterall.

Think they're still working on the ACS.

And the horsies are late.  They were supposed to be here a few years ago now.  Probably a good thing, since the Elves haven't shown (back) up yet either with the Galactic goodies.  Like ACS  .

I've started to think about weapons systems like this for my own science fiction.  After reviewing the info on Atomic Rocket, this is what I came up with:

http://devonai.wordpress.com/2010/12/02/miscellanea-mphi-m24c-mass-driver-cannon/

I like the idea of using osmium as a slug.  Any thoughts on this?

If you can PAY for it, maybe... (osmium is gawdawful expensive round these parts, last I heard)

[AJ Dual]

I've started to think about weapons systems like this for my own science fiction.  After reviewing the info on Atomic Rocket, this is what I came up with:

http://devonai.wordpress.com/2010/12/02/miscellanea-mphi-m24c-mass-driver-cannon/

I like the idea of using osmium as a slug.  Any thoughts on this?

Osmium is expensive? Each of your 60kg slugs costs about $800,000 in 2010 USD.

Space sources might be a bit better than Earth, but there's an average decreasing distribution of each element on average as you go up in atomic weight. Things'll get better after planets have formed around Population III stars, after all our Population II stars go nova and distribute a higher percentage of those heavy elements.

However, that's a long time to wait.  

DU is lots cheaper if your SF universe/technology still makes extensive use of fission for power sources. Costs are defrayed because the dual use of mining for energy etc. and as projectiles, just as today.

And with no atmospheric drag issues, mass matters more than volume. A long skinny rod of plain old asteroidal iron that masses the same as an egg of Osmium will carry the same KE much more cheaply. And it's sectional density would be amazing.  (Think how an arrow can go through sandbags at 300-400fps, when a .50BMG at 2900fps can't.)

The hardness and density of the Osmium would be great if the enemy vessel uses ablative armor, thick low density foams, or aerogell shrouds to vaporize KEW's before they reach any vital ship components, (although carry this too far, the ship can't accelerate without leaving it's flimsy armor behind) Or if it uses some sort of exotic highly rigid or high density armor. (Although too massive, and the ship's performance will suffer...

Using high density metals for KEW's has it's upsides and drawbacks.

I'd say that a standardized sabot system with cheap iron rods as the main ammunition, and specialty Osmium or DU rounds when the situation warrants it might be the way to go.

[kgbsquirrel]

Hmm, have they found a solution to the rail erosion problem yet? As I recall, the primary problem with rail guns was you stripped away a lot of metal from the contact rails per shot. I've always been a bigger fan of the gauss/coil gun because the projectile is propelled by a magnetic field with no actual physical contact though its problem is magnetic saturation of the projectile limiting it's potential velocity. I'd be curious to see which problem gets solved first to the point of feasibility of fielding the weapon system.

[freakazoid]

any idea how large is the projectile?

You can see them load one in this video, http://www.youtube.com/watch?v=y54aLcC3G74 at around 1:45

[geronimotwo]

unless i am mistaken, that last vid was shot at 10,000 frames per second!  and it did not look as smooth as the first.  not even close.

[Devonai]

And with no atmospheric drag issues, mass matters more than volume. A long skinny rod of plain old asteroidal iron that masses the same as an egg of Osmium will carry the same KE much more cheaply. And it's sectional density would be amazing.  (Think how an arrow can go through sandbags at 300-400fps, when a .50BMG at 2900fps can't.)

I'd say that a standardized sabot system with cheap iron rods as the main ammunition, and specialty Osmium or DU rounds when the situation warrants it might be the way to go.

Good stuff, thank you.  I was going with the idea that some form of higher technology would allow Osmium to be refined in greater quantities at a lower cost, but using it for specialty rounds makes more sense.

[AJ Dual]

Good stuff, thank you.  I was going with the idea that some form of higher technology would allow Osmium to be refined in greater quantities at a lower cost, but using it for specialty rounds makes more sense.

Does the fic. universe have any functional VonNeuman type tech? Or at least highly automated mining? If so, then yes. You can just turn the machines loose and they'll do whatever you want for "free", save the overall entropy of the Universe at large and wherever it is they get their energy from.

Otherwise the the statistical distribution of rare metals and heavy metals works against you in an economic sense no matter what.

Another though is that high density metals are like ball ammo, they might just sail on through a target, carrying a lot of wasted energy with them. Less exotic materials that aren't as hard/dense will vaporize more completely, and create more secondary damage.

Another consideration is the ship's drive efficiency and technology in the fic. universe. If it's GOOD, it's possibly just easier to get your KEW's up to speed and let them go, then make a course change, than it is to launch them with some sort of "gun".

This falls back on the Niven's "Kzinti Lesson" namely: "Any drive technology that's sufficiently efficient, powerful, and advanced, is itself a weapon that is equally efficient powerful and advanced.

You might be looking at a situation where offensive KEW's are gotten up to speed by the ship and released since you are choosing the time and place of firing, but defensive KEW's are shot from "guns" because you may need to lay down CIWS fire anywhere, independent of your maneuvers. (Presumably if you could maneuver/thrust to fire back and intercept incoming KEW's, then you could just get out of the way/evade too.)

You could also touch on all sorts of strategy like "bright" KEW's vs. "dark" KEW's, where a spread of high albedo, radar reflective, or warm in the IR spectrum KEW's gets an enemy ship to move to evade, only to run into a second formation of "dark" projectiles that are chilled to reduce their IR signature, are not radar reflective, or have a low visible abedo.

Then I imagine there's all sorts of complicated mathematics based on how many KEW's you've got. The targeting precision, the distance you're firing at, the closing velocity, and the enemy's Delta-V to evade at velocity X when they've got Y% probability of detecting the incoming KEW's, which mandates firing a spread of size Z to cover the area they can't escape from in time.

[roo_ster]

We already get Mach 6.5+ outta such critters as LOSAT & CKEM using rocket motors.

That was only in the 10-20MJ range, depending on the missile mass.

Range was "way out there" limited by LOS in most cases.

If they can increase the rate of fire, a LOS weapon of that speed with a suitable targeting system makes flying aircraft into its target envelope a dicey prospect.

Meh, you don't need much of a rate of fire if your fire control is worth a damn.  ONE shot is all it takes.

[erictank]

We already get Mach 6.5+ outta such critters as LOSAT & CKEM using rocket motors.

That was only in the 10-20MJ range, depending on the missile mass.

Range was "way out there" limited by LOS in most cases.

Meh, you don't need much of a rate of fire if your fire control is worth a damn.  ONE shot is all it takes.

What if you're up against more than one target?