Do starships use projectile weapons?

[Lord Sabre Ace]

A projectile moving at hyperspace velocity would have an enormous amount of energy.

We know that KE=.5m*v^2 and that hyperdrive can move ships at 100 million c. We'll say the projectile weighs 5 kg.

KE=.5(5kg*(100,000,000(299792458m/s))^2)
KE=.5(5kg*(3.00e16m/s)^2)
KE=.5(5kg*8.99e32m^2/s^2)
KE=.5(4.49e33kgm^2/s^2)
KE=2.25e33 Joules

(I assume this is correct, but if it's not please correct me.)

When a 5kg projectile can hit a target with that much energy, why don't we see or read about the Empire using them?

[Captain tycho]

Well, I doubt it would be very efficient fitting every shell with a hyperdrive and nav computer so that it would exit hyperspace right before slamming into the target. But even at near c, it would do a huge amount of damage.

[Sea Skimmer]

(I assume this is correct, but if it's not please correct me.)

You need infinite energy to reach C, and you cannot calculate kinetic energy for values over C. Your math is flawed and meaningless because of this. If you attach any value to the impact energy of a faster then light object, you've value is just arbitrary and made up with no basis in science

When a 5kg projectile can hit a target with that much energy, why don't we see or read about the Empire using them?

One would assume that turbolasers are universally the most all around effective and destructive weapons packages available, given how totally they dominate vehicle and starship armament.
Accelerating an object to a high fraction of C (since FTL is a no go) would require absurdly high acceleration unless you had an absurdly long weapon barrel, I'd expect that's just not possible for them to do with a solid mass.

[Connor MacLeod]

One would assume that turbolasers are universally the most all around effective and destructive weapons packages available, given how totally they dominate vehicle and starship armament.

Except there are ion cannons. And there are apparently cases when starship mounted projectile weapons are used (ROTS is ample evidence by the movie alone.)

Accelerating an object to a high fraction of C (since FTL is a no go) would require absurdly high acceleration unless you had an absurdly long weapon barrel, I'd expect that's just not possible for them to do with a solid mass.

If that were true, then it would be downright impossible for a starship to acceclerate itself, since the relatavistic thrust stream is near-c (and made up mostly of relatavistic mass anyhow.) Yet we know ISDs and other starships do not have "absurdly long" thrusters or nozzles. The same goes for ion cannons (which almost invariably have to be near-c particle streams with a large amount of relatavistic mass in order to be able to penetrate shields. IE they have to be brute-force weapons like turbolasers.

Turbolasers ARE much more efficient (you don't really need "propellant" like you do with ion cannons or projectile cannons.), but ion cannons (or even projectile weapons) can have benefits that turbolasers can and do lack.

[Srynerson]

A projectile moving at hyperspace velocity would have an enormous amount of energy.

We know that KE=.5m*v^2 and that hyperdrive can move ships at 100 million c. We'll say the projectile weighs 5 kg.

KE=.5(5kg*(100,000,000(299792458m/s))^2)
KE=.5(5kg*(3.00e16m/s)^2)
KE=.5(5kg*8.99e32m^2/s^2)
KE=.5(4.49e33kgm^2/s^2)
KE=2.25e33 Joules

(I assume this is correct, but if it's not please correct me.)

When a 5kg projectile can hit a target with that much energy, why don't we see or read about the Empire using them?

Maybe I've always misunderstood, but it was my impression that hyperdrives do not accelerate ships. The fact that a hyperdrive allows a vessel to move from Point A to Point B in one one-hundred-millionth of the time a beam of light would take to cross that same distance does not mean that the ship is traveling at one-hunded million times the speed of light.

[dragon]

Its not because if was moving at that speed than interstellar space dust would destory the ship. Plus that equation is only usefull for non relativistic speeds.

[Darth Wong]

Its not because if was moving at that speed than interstellar space dust would destory the ship. Plus that equation is only usefull for non relativistic speeds.

Not necessarily. We really have no idea how normal matter would interact with tachyonic objects, assuming solid tachyonic objects are even possible. It may be that you need an enormous amount of mass and energy to affect tachyonic objects as they move through space, hence you're OK unless you fly right through a star.

[Beowulf]

Simple answer: That equation is wrong. It only works for non-relativistic objects, which generally means < .01c or so.

[Ford Prefect]

Ker = ((1/sqrt(1 - (V2/C2))) - 1) * M * C2

Where:
Ker = relativistic kinetic energy (Joules)
M = mass of projectile (kg)
V = velocity of projectile relative to target (m/s)
C = speed of light in m/s = 3e8

THat's the equation to use for substantial percentages of c, I believe. If my understanding is correct, it is for relativistic projectiles, and relativistic effects start to occur at around 14% the speed of light. Of course, I'm not extremely sound on the subject.

[Lord Revan]

We know that at least some CIS ship (especially the Invinsible Hand) have projectile weapons, those big guns that eject shells in ROTS.

[Illuminatus Primus]

Superluminal objects' kinetic energy cannot be derived using Newtonian equations. You must use relativistic equations. And energy decreases as you accelerate beyond c.

A superluminal object requires infinite energy to deaccelerate to c.

[Wyrm]

The relativistic kinetic energy equation would be

KE = m c^2 / \sqrt{1 - (v/c)^2}

Tachyons are posited to have imaginary mass, and because v < c, the term under the square-root is also negative, so the denominator is imaginary. Therefore, the fraction gives you a real-number answer. At v = 1e8 c, this grinds out to 8.987e8 J = 898.7 MJ. In comparison, it takes 7.8 MJ to melt a kg of iron, so you can melt a 115 kg block of iron, a cube about 36.6 centimeters on a side.

In contrast the accepted lower limit to maximum TL bolt energy is 280 TJ (30 TJ heating, 250 TJ melting).

Actually, slowing the projectile down gives you more kinetic energy. For instance, at only 1+2.02e-35 times c, the KE of that 5 kg shot is 1e33 J, which is Death Star-class planet-busting power!

EDIT: Corrected size of the iron cube. Forgot use density. >x<

[Glimmervoid]

We know that at least some CIS ship (especially the Invinsible Hand) have projectile weapons, those big guns that eject shells in ROTS.

And Yuuzhan Vong would occasionally have there ships throw moons at planets.