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Popeyesays
04-16-2007, 09:35 AM
I have a hard science weapon question for you guys:

Given a 12 gram vanadium steel projectile impacting a target at a velocity of 18,600,000 meters per second (10% of the speed of light) what is the energy transfer in joules?

I'm postulating a magnetic mass driver as a space weapon and need to get a handle on the destructive capacity of the weapon.

Regards,
Scott

KanShu
04-16-2007, 12:14 PM
The kinetic energy of the projectile is 2.08x1012 joules (from E = 1/2 mv2), so if the projectile imparts all its energy to the target that value is your energy transfer (assuming the target is much larger than the projectile and stationary).

For cases other than this, the calculations get very hairy very quickly.

Hope this helps.

Edit:

Just noticed this: 18,600,000 m/s is roughly 6% the speed of light. For 10%, the kinetic energy jumps up to 5.4x1012 joules.

TSByrne
04-26-2007, 02:31 AM
So in layman's terms how bad does that jack up the Enterprise?

benbradley
04-26-2007, 03:36 AM
I have a hard science weapon question for you guys:

Given a 12 gram vanadium steel projectile impacting a target at a velocity of 18,600,000 meters per second (10% of the speed of light) what is the energy transfer in joules?

I'm postulating a magnetic mass driver as a space weapon and need to get a handle on the destructive capacity of the weapon.

Regards,
Scott
Firstly, that doesn't look quite like 10 percent of lightspeed (Yes, I actually remember figures such as 186,282 miles per second as lightspeed), so I googled:
18,600,000 meters per second in miles per second
and got:
18600000 (meters per second) = 11557.5042 miles per second

The copy/paste thing is strange here, I didn't ask for that font size, but anyway, that's only about 6.2 percent of lightspeed, still a respectable speed and a helluva lot of energy in 12 grams of metal.

This brings up other questions as well as the energy in the projectile. How thick is the object it strikes, and what is it made of? For any man-made device or ship currently or ever in outer space, your projectile will make a hole through it and barely slow down. The hole might splatter out on the other side, I'm not sure. If the struck object is thick and dense enough to stop the projectile (something made of steel several feet or tens of feet thick, maybe even thicker), then much of that energy will be released as heat and light. The bit of steel will melt, vaporize, and might even get hot enough for fusion, all in a small fraction of the blink of an eye. Take KanShu's calculation and compare with the output of a megaton or TNT or various size nuclear bombs.

Looking online, a kiloton of TNT is about 4*10^12 joules (http://en.wikipedia.org/wiki/Megaton) (http://en.wikipedia.org/wiki/Megaton%29), about the size of a quite small nuclear explosion (a "small" nuclear bomb test is expected to be about 10 kilotons of TNT, but North Korea's recent test was believed to be less than one kiloton: http://en.wikipedia.org/wiki/2006_North_Korean_nuclear_test) (http://en.wikipedia.org/wiki/2006_North_Korean_nuclear_test%29).

I was going to suggest the Usenet newsgroup rec.arts.sf.science for this question, but with KanShu's help, I think I've done well with answering it.:)


So in layman's terms how bad does that jack up the Enterprise?
Depends on where it hits. It would likely leave just a small hole through it (compared to the larger one the dish part got in one of the movies), but if it hits a thick, dense object or the antimatter containment vessel (whatever that's called, I just know it's not a Jeffries tube), there could be big problems.

dclary
04-26-2007, 10:00 PM
If it hits a pressurized vessel, would the exit hole be enormous as it sucks the atmospheric gases out with the slug?

Pthom
04-27-2007, 12:05 AM
If it hits a pressurized vessel, would the exit hole be enormous as it sucks the atmospheric gases out with the slug?
Explosive decompression? Not according to investigations by the guys of Mythbusters. Yeah, the air leaks out, and fast, but it doesn't take huge chunks of the vessel with it. Granted, they did it in an airliner, which they pressurized to 1 1/2 atmospheres or something (a 1/2 atmosphere differential), but the myth was that if a terrorist shot a bullet through one of the windows, the plane would blow apart (on the order of the wreck of flight 815 in LOST). Didn't happen. They did ultimately get a bigger hole--but they had to resort to high explosives to do it.

dclary
04-27-2007, 11:59 AM
Stupid mythbusters!

:p

Lhun
04-28-2007, 02:56 PM
Explosive decompression? Not according to investigations by the guys of Mythbusters. Yeah, the air leaks out, and fast, but it doesn't take huge chunks of the vessel with it. Granted, they did it in an airliner, which they pressurized to 1 1/2 atmospheres or something (a 1/2 atmosphere differential), but the myth was that if a terrorist shot a bullet through one of the windows, the plane would blow apart (on the order of the wreck of flight 815 in LOST). Didn't happen. They did ultimately get a bigger hole--but they had to resort to high explosives to do it.

Well, if you think about it, the pressure difference is only one bar. Too much for unprotected lung capillaries for sure, but not really in the realm of explosives.
Another thing that's very often wrong is being shock-frozen in space.
Not gonna happen. Sure, it's cold out there, but you're also surrounded by a near perfect vacuum. You freeze down to 0K but very, very slowly. At the speed the body radiates infrared radiation to precise. You freeze a LOT faster in a normal blizzard that's only a couple of degrees below zero because of the air that can conduct the heat.
A human could survive quite a while in space if he protects the vulnerable membranes, i.e. the goldfishbowl-helmet alone is pretty decent. If you don't go out into direct sunlight and get fried, you could do a spacewalk with nothing but a helmet and normal clothes.

benbradley
04-28-2007, 05:16 PM
Explosive decompression? Not according to investigations by the guys of Mythbusters. Yeah, the air leaks out, and fast, but it doesn't take huge chunks of the vessel with it. Granted, they did it in an airliner, which they pressurized to 1 1/2 atmospheres or something (a 1/2 atmosphere differential), but the myth was that if a terrorist shot a bullet through one of the windows, the plane would blow apart (on the order of the wreck of flight 815 in LOST). Didn't happen. They did ultimately get a bigger hole--but they had to resort to high explosives to do it.
This is, I presume, with ordinary bullets going at "ordinary bullet" speeds. A bullet going 6 or 10 percent of lightspeed is going maybe 100,000 times as fast. I presume (for the moment at least) it will generate the same size holes at a much faster speed, but the "splatter" of whatever the bullet hits and pushes out of the way to make the hole will be another thing. I wouldn't want to be anywhere around it.

Popeyesays
05-02-2007, 03:53 AM
Look at a kinetic tank penetrator. It turns the kinetic energy into heat very quickly. The penetrator and a quantity of the hull armor become a plasma which jets through the ship that is hit.

Anybody know the ergs to foot pounds formula?

Explosive decompression isn't the issue here. We're talking about warships after all which will be armored, compartmented and have their crew in space armor during combat.

The question is how much of the hull is going to be turned into high-temp plasma in the process, One has to compare that to the displacement tonnage and material tonnage of the ship hit to know how much is going to survive.

Regards,
Scott

Pthom
05-02-2007, 09:50 AM
I'm curious:

What accelerates this 12-gram (185 grains) steel bullet to 0.1C (67,061,663 mph)? A 55 grain high-velocity rifle bullet (http://www.winchester.com/products/catalog/cfrdetail.aspx?symbol=SBST243SS&cart=MjQzIFdTU00=)accelerated by an explosive charge barely exceeds 4000 fps (2,768.2 mph). You need to get this little thing of yours going 25,000 times as fast.

It's unimaginable how massive the explosion would need to be to propell it to such a velocity from a gun, let alone how massive the gun itself (canon?) would have to be to contain such an explosion. The only way I can think of to bring any mass to 0.1C (and keep it as recognizable in flight as it is at rest) would be with some sort of continuous acceleration. The fuel requirement for a conventional rocket to do that is mind boggling. Sure, it's been postulated that solar sails or ion drives might accelerate a mass to such velocities, but the distances and time required are so immense to preclude use as a weapon.

Is this bullet somehow brought to this velocity by accident?

Popeyesays
05-02-2007, 09:57 AM
I'm curious:

What accelerates this 12-gram (185 grains) steel bullet to 0.1C (67,061,663 mph)? A 55 grain high-velocity rifle bullet (http://www.winchester.com/products/catalog/cfrdetail.aspx?symbol=SBST243SS&cart=MjQzIFdTU00=)accelerated by an explosive charge barely exceeds 4000 fps (2,768.2 mph). You need to get this little thing of yours going 25,000 times as fast.

It's unimaginable how massive the explosion would need to be to propell it to such a velocity from a gun, let alone how massive the gun itself (canon?) would have to be to contain such an explosion. The only way I can think of to bring any mass to 0.1C (and keep it as recognizable in flight as it is at rest) would be with some sort of continuous acceleration. The fuel requirement for a conventional rocket to do that is mind boggling. Sure, it's been postulated that solar sails or ion drives might accelerate a mass to such velocities, but the distances and time required are so immense to preclude use as a weapon.

Is this bullet somehow brought to this velocity by accident?

No chemical or atomic propellant is present. It's a magnetic rail gun operating in a vacuum. The electromagnets are powered by fusion generators.

Also no friction because the dart is suspended in the gun by magnetic levitation.

Regards,

Scott

Pthom
05-02-2007, 10:49 AM
Okay. I guess. No friction = pure Newtonian physics problem.

But I'm still curious: How long is your rail gun? How big your magnets, your fusion reactors and the generators they drive?

The rifle bullet is accelerated to 3k mph in less than a meter. Can a linear motor accelerate a (somewhat fat) rifle bullet to 25k times as fast in anywhere near as reasonable a distance?

Seems to me that if you can somehow do this, I dunno: are we approaching the limits of molecular bonds? Would the leading mass of the projectile be overtaken by the rearward mass, effectively turning the thing inside out? Is steel (even vanadium steel) that strong?

Someone here is a wiz with the math of these kinds of problems. Luhn? You following this?

benbradley
05-02-2007, 12:58 PM
A rail gun as I understand it works by generating a a high current that passes through one rail, through the projectile, and through the other rail, so the projectile has to be touching both rails as it slides along them, and conduct a quite high current as well. The magnetic field generated by the "half turn" (as in a coil having several turns of wire, but this is only 1/2 turn) at the projectile pushes it forward. This contact causes a bit of inefficiency, and is likely to be problematic as the bullet approaches the speeds mentioned in the OP (imagine a sliding contact between two metals, one going 1 percent the speed of light).

Accelerating to that speed within a meter or so would indeed be a huge amount of acceleration. I'd have to calculate things, but I would make the railgun one or many kilometers long so it gives "reasonable" acceleration where strength of materials calculations wouldn't indicate things tearing apart.

Oh, by the way, this (if you're using reasonable real-world physics as we know it) is not a hand-held device like a conventional rifle. The mechanical aspects of aiming it could be a problem.

There's also the coilgun, where the projectile goes through the center of one or more electrical coils. Each coil is given electrical current for just long enough to accelerate the projectile through it, turning off as it passes through the center. Thus a moving magnetic field pulls the projectile along. This design IS frictionless, as long as the projectile doesn't slide against the inside of a coil. The magnetic field may keep it centered.

If I understand correctly, both of these types of designs CAN accelerate things to speeds faster than a rifle (though making one that would shoot at even 1 percent of lightspeed would be a huge investment), and much activity in ths area was done in the '80's under the Strategic Defense Initiative (President Reagan's "Star Wars" plan).

Popeyesays
05-02-2007, 07:08 PM
Coil gun, that's better. The magnetic field passes the dart from one coil to the next, each coil adding to the acceleration along the way. I am projecting a spinal mount on a starship, the gun itself being about a kilometer in length, protruding from both ends of the 800 meter long ovoid space craft.

If both ends of the gun tube are open, there should be little recoil.

The 'drive' for the ship does not provide any acceleration or motion in any physical sense. It is based upon the electron transfer phenomenon where a free electron within the orbital shells of the atom is present where ever you look for it, without traversing the distance between it's origin and the destination of the electron within the orbital shells. In effect the drive is a network of iridium and lanthanum wires in the hull, the power system of the ship activates the field and it causes the whole ship to become an electron for a pico second at a time, flipping the ship in the direction of travel a few hundred meters each pico second. The ship in the sense of inertia and momentum is at rest throughout the process, thus there is no velocity and no time dilation.

The weapons in the system are basically understandable today--missiles using the same drive operate to put a fission pumped x-ray laser warhead close enough to the target and the x-ray laser beam travels at the speed of light and is a micro seconds long pulse of energy. Ship's also mount laser weapons, particle beam accelerators in both turret mounts and in spinal mounts with very long accelerator tubes.

The dart in question I picture more as a very thin projectile more like a sewing needle than a bullet.

The first book will be out as an e-book this month (Sword of the Dajjal), it's indexed in the library section here on Absolute Write, I am working on the sequel and the coil gun in question is new technology, so it should have some technological problems and dependability issues. One chief thing about hitting these ships with weapons is that the ship literally does not physically exist in the process of a jump. It would be potentially possible to have the ship snap into being while the vanadium dart was already in existence inside the vessel, it would then become part of the vessel during the jump and continue it's momentum when the ship materializes along its direction of travel.

It woulod be functionally possible to have a dead on hit that misses because the ship just flickered out of existence. The whole story is set in the 27th century, with the "Flicker Drive" being invented at the end of this century.

Regards,
Scott

Pthom
05-02-2007, 11:22 PM
Cool stuff, Scott. Of course most of it is SF, eh? But you're asking questions in the Science Fact forum, so...

A couple of things you might want to consider:

If both ends of the gun tube are open, there should be little recoil.
If you have mass A at rest in contact with another mass B, even if that contact is a magnetic field, then accelerate mass A relative to mass B, there is indeed a reaction. But because your 'dart' is several orders of magnitude smaller than the ship, the reaction should be negligible. But from 0 to 0.1C in a kilometer? Baby, it ain't a bazooka: when the dart moves forward, something's gonna move back.

The 'drive' for the ship does not provide any acceleration or motion in any physical sense. It is based upon the electron transfer phenomenon where a free electron within the orbital shells of the atom is present where ever you look for it, without traversing the distance between it's origin and the destination of the electron within the orbital shells.

This is quantum phenomena, yes?
...the ship literally does not physically exist in the process of a jump.
Explain how the biological occupants of the vessel survive this electron spatial transfer and emerge on the other side of each pico-second jump with all their faculties in the same order as before. It's one thing to shift the molecules of aluminum, titanium and acrylic this way--they only need to be mostly the same once the transfer is over. But I dearly want to be exactly the same after. :)

Popeyesays
05-03-2007, 12:02 AM
Cool stuff, Scott. Of course most of it is SF, eh? But you're asking questions in the Science Fact forum, so...


This is quantum phenomena, yes?
...the ship literally does not physically exist in the process of a jump.Explain how the biological occupants of the vessel survive this electron spatial transfer and emerge on the other side of each pico-second jump with all their faculties in the same order as before. It's one thing to shift the molecules of aluminum, titanium and acrylic this way--they only need to be mostly the same once the transfer is over. But I dearly want to be exactly the same after. :)

Yes, it is. I'm going on the assumption that the whole ship becomes effectively a single particle in the process of the drive, and the contents of the ship are protected by the simple fact of containment within the particle.

Now sufficient damage to the hull of the ship and the drive net, will play hell with the integrity of the effect, I am sure.

I came to this board because I wanted to be sure I wasn't developing a planet-buster weapon, I want to keep things so that war can be limited.

For a bombardment weapon I am postulating a kinetic energy weapon called "Thor's Hammer", affectionately known as the "crowbar'. Radioactively it's quite clean (allowing for a small burst of x-rays with the transfer of kinetic energy) and some EMP effect. Firearms are either caseless or using binary propellants, and magnetic or gauss small arms. There is some limited use of shoulder mount lasers for sniper weapons, but generally energy weapons are mounted on vehicles or tripod supported with attached energy cells.

I'm trying to keep the whole technology as a foreseeable extrapolation of real-life technology.

Regards,
Scott

Lhun
06-29-2007, 11:11 PM
I'm unfortunately kinda out of internet access at the moment so i can't quite follow even interesting threads (like this one ;)

Magnetic acceleration of projectiles to nearly any speeds is one the hand just a problem of energy. Given enough energy we could concievably create Gauss (or coil~) guns today, it's just that lugging around the battery packs for those is impossible.
There is however a problem for limited gun size, since magnetic fields that get too strong tend to rip apart the coils generating them. Though i think it's perfectly within artistic license to just ignore that problem or explain it away with ultra-sturdy superconducting materials.
Another thing to consider here is that if you have enough energy available to power such a kinetic weapon, you also have enough energy to create some really powerful lasers, electron beams and other such weapons.
What's stopping us today from creating laser weapons is again, mostly just the weight of batteries. We've not yet found a better way to store weapons energy than as chemical energy.

One problem with limiting space weaponry at a level below planetbusters is that we, today, could easily make a whole planet uninhabitable. All you need to to is find a suitably big asteroid, install a few rocket drives and give it a push in the right direction. Any spaceborn war should logically see such weapons in action, especially since suitably big in this context is extremely tiny when compared to normal asteroid sizes.
The potential energy of anything thats not inside the gravity well will make for a splendid weapon when you toss it back in.
Theres no real way i know of to tweak the scenario physics to make such simple attacks unlogical, so the best way is probably to make the technology in the setting solve it. Find some way why planetary defenses can easily defend against simply throwing big masses down the gravity well.

benbradley
06-30-2007, 06:59 AM
I saw this when it was first posted, but for some reason I didn't respond.

Coil gun, that's better. The magnetic field passes the dart from one coil to the next, each coil adding to the acceleration along the way. I am projecting a spinal mount on a starship, the gun itself being about a kilometer in length, protruding from both ends of the 800 meter long ovoid space craft.

If both ends of the gun tube are open, there should be little recoil.
NO! This is true of a "rocket launcher" or Bazooka, because the exhaust gases (their action of going back causes the reaction of the rocket going forward) go out the back instead of being trapped inside a gun barrel. One of Newton's laws is "for every action there is an equal and opposite reaction.) In a coil gun, the force is on the coils, and so gets transferred to the tube.

The 'drive' for the ship does not provide any acceleration or motion in any physical sense. It is based upon the electron transfer phenomenon where a free electron within the orbital shells of the atom is present where ever you look for it, without traversing the distance between it's origin and the destination of the electron within the orbital shells. In effect the drive is a network of iridium and lanthanum wires in the hull, the power system of the ship activates the field and it causes the whole ship to become an electron for a pico second at a time, flipping the ship in the direction of travel a few hundred meters each pico second. The ship in the sense of inertia and momentum is at rest throughout the process, thus there is no velocity and no time dilation.
That's some really interesting HandWavium there!

The weapons in the system are basically understandable today--missiles using the same drive operate to put a fission pumped x-ray laser warhead close enough to the target and the x-ray laser beam travels at the speed of light and is a micro seconds long pulse of energy. Ship's also mount laser weapons, particle beam accelerators in both turret mounts and in spinal mounts with very long accelerator tubes.

The dart in question I picture more as a very thin projectile more like a sewing needle than a bullet.

The first book will be out as an e-book this month (Sword of the Dajjal), it's indexed in the library section here on Absolute Write, I am working on the sequel and the coil gun in question is new technology, so it should have some technological problems and dependability issues. One chief thing about hitting these ships with weapons is that the ship literally does not physically exist in the process of a jump. It would be potentially possible to have the ship snap into being while the vanadium dart was already in existence inside the vessel, it would then become part of the vessel during the jump and continue it's momentum when the ship materializes along its direction of travel.

It woulod be functionally possible to have a dead on hit that misses because the ship just flickered out of existence. The whole story is set in the 27th century, with the "Flicker Drive" being invented at the end of this century.

Regards,
Scott
If there are detectors for the 0.1c 'dart', it could reliably be avoided by 'flickering out', but I'm wondering if a "shotgun blast" of such darts might be more effective.

There's also the question of where the darts that miss their targets eventually go. I might get the willies from this - one might make a hit or near-miss on a world of super-alien beings, thus alerting them to Human (and whatever else we're fighting) presence in the Galaxy, much like the Heechee in the Gateway series. Or is that for the third book in the series?

dclary
07-02-2007, 05:14 AM
You know, as impossible as it may be... wouldn't it just be an awesome scene in a movie to see a chain-driven slug-thrower of capital-ship size. You know, a Star Destroyer firing Hummer-sized slugs with this immense stream of brass shells ejecting from ports to either side.

That would rock.

Artist's My rendition below:


http://randomsynapses.com/images/sd.jpg