Laser vs Missile

[Kuciwalker]

Originally posted by Patroklos
Oh noos!

I do think mass drivers provide the best weapons choice for first generation space combat. Better power in/power out ratio, and the technology is relatively simple.

What are you talking about? Neither assertion is true...

[Kuciwalker]

Originally posted by Whoha
I'll grant that, even though the requirements for a laser that has to survive being shot are somewhat different from a warhead that doesn't, but even if they start out equal the warhead still wins at long distance.

At ranges considered "long distance" for a military space laser, I don't think any weapon will be particularly effective.

The energy will be spread a "comparatively" short distance from the ultimate detonation point, which will be the hull of the ship.

And you think force spread over a large area is more effective than force spread over a small area why?

that material would be blown into space and away from the target/laser.

Why would the material be blown into space rather than transferring most of its energy into the rest of the ship (via the explosion)? The energy should be about equal in both directions.

[Kuciwalker]

Originally posted by snoopy369
Well, there is if you pack it full of shrapnel

A missile full of shrapnel would have to be based on conventional explosives, or something of similar energy density. Increase the energy density a lot (e.g. nuke) and the shrapnel is vaporized. Therefore you've got a weapon with far less damage potential than our hypothetical military space laser.

[Dr Strangelove]

I think a laser would simply cut through the hull. Laser beams are generally on the order of microns in diameter. That's not going to create much of an explosion, except for the explosive decompression of the compartments opened to space.
Lasers would be deflected if the surface of the ship were mirrored.
Even in space a nuclear detonation is going to create a miniature sphere of heat a couple hundred yards in diameter. That would take a serious chunk out of even a Star Wars Imperial Star Destroyer.

[Whoha]

Originally posted by Kuciwalker

Originally posted by Whoha
I'll grant that, even though the requirements for a laser that has to survive being shot are somewhat different from a warhead that doesn't, but even if they start out equal the warhead still wins at long distance.

At ranges considered "long distance" for a military space laser, I don't think any weapon will be particularly effective.

Missiles can continue ballistically without consuming fuel, so they can travel much longer distances.

The energy will be spread a "comparatively" short distance from the ultimate detonation point, which will be the hull of the ship.

And you think force spread over a large area is more effective than force spread over a small area why?

Overkill. Most of the energy from the laser will pass through the ship, while the warhead will vaporize the entire ship.

that material would be blown into space and away from the target/laser.

Why would the material be blown into space rather than transferring most of its energy into the rest of the ship (via the explosion)? The energy should be about equal in both directions.

Atmosphere behind the plating that just got vaporized will push it out.

[Kuciwalker]

Missiles can continue ballistically without consuming fuel, so they can travel much longer distances.

Do you know how long it would take a missile going at non-relativistic speeds to hit a target that's "far away" (several light-seconds) for a laser?

Overkill. Most of the energy from the laser will pass through the ship, while the warhead will vaporize the entire ship.

Lasers don't cut through ships. When the laser hits it vaporizes the surface it hits, but it doesn't annihilate the surface. The matter is still there and it continues to absorb most of the rest of the laser. Given the duration of the laser (probably a very small fraction of a second), this amounts to almost all of the energy of the laser deposited at one point on the surface of the ship at one instant.

Atmosphere behind the plating that just got vaporized will push it out.

Wrong timescale. That effect takes orders of magnitude longer than the duration of the beam.

[Kuciwalker]

Originally posted by Dr Strangelove
I think a laser would simply cut through the hull. Laser beams are generally on the order of microns in diameter. That's not going to create much of an explosion, except for the explosive decompression of the compartments opened to space.

See above; a military laser is not going to cut through anything.

[snoopy369]

Originally posted by Kuciwalker

Originally posted by snoopy369
If you can't imagine defensive technology that would be useful against a laser, Kuci, then you should perhaps consider that your imagination is the issue...

I can imagine defensive technology that you think would be useful against a laser, but I can also debunk all of it. So put up or shut up

A defensive screen could be any particle or wave that interferes with the function of a laser, applied externally to a ship or other object or location that needs to be defended.

.................

Explain how a "wave" would "interfere with the function of a laser". No technobabble please - this may be sci-fi, but I'm not going to accept an argument based on "I can make up whatever magic I want, QED."

I include wave due to the fact that I am not an optical physicist and so don't know if a wave is possible or not. I mostly am imagining a particle screen that is made of highly reflective particles. Heck, even water particles would refract the laser ... put water in your hull so that when a laser hits the hull it comes out and refracts the laser.

You could imagine small metallic dust particles held in place magnetically, that would aid in the dispersion of the laser;

Yes, like that.

hypothesize an interference wave similar to a sound wave (as sound waves can interfere with each other either constructively or destructively) but with light

That doesn't work with light. Period. Light waves are purely additive; to "interfere" with the laser in such a way to eliminate its effects, you'd need another laser at the same place as the first.

I'm not sure you are necessarily correct here, regardless of our current understanding of the matter. A laser over distance (as we're discussing here, remember; we're talking kilometers away) will be already somewhat dispersed, so if it's possible it will certainly apply in these situations.

or even some sort of plating or armor that disperses, reflects, or absorbs the laser in a non-destructive way.

Good luck with that. There's no perfect mirror; even if you have a substance with 99% reflectivity, or 99.9% reflectivity, it'd be worthless against a military laser because the reflective surface would be instantly vaporized by the front of the beam and the rest of the energy would be delivered in full. I have no idea what you mean be "dispereses", and "absorbs in a non-destructive way" is impossible - you just said "make uber-massive armor that isn't annihilated by the energy deposited into it by the laser." Such armor would of course be even more effective against a less focused weapon like a missile.

What we can make in space, who knows? Certainly more perfect mirrors than we ever could make here. Or a substance that absorbs the heat and redirects it (a heat spreader), or even something that redirects the heat to a liquid medium that would turn the heat into power. Or use multilayered vacuum plating with some substance in the middle that fills the hole when a hole is made by virtue of the properties of vacuum (ie, like tire hole repair).

You can't avoid the simple fact that a laser can focus more energy in a smaller area than a missile. Any defensive measure would have to rely on the difference in the character of that energy - that lasers are light whereas missiles are (apart from nukes) kinetic. Unfortunately for you, the only thing that operates differently on those is a mirror, and no mirror could defend against a military laser.

You are ignoring an awful lot of possibilities - and you yourself are assuming significant technological developments. Fortunately there are plenty of people out there who think outside the box, to make these incredible technological advances... sure, most of the above are probably impossible - but if one is not, that's a big thing in and of itself.

Missiles (or self guided ships) are pretty incredible also, and have a lot of potential. If we're at a point where space travel is commonplace, and in most of the discussed situations we have some method of surpassing light speed, why can't the missile do the same (or more - lesser acceleration constraints). Your laser may be going at 186,000 mi/s but my missile is going 400,000 mi/s and accelerating at 100,000 mi/s^2... or even if there is no surpassing the speed of light, then missiles certainly can still accelerate dramatically faster than a ship, and if you have a few thousand of them coming at you at once, how exactly will you stop them?

Part of my point is that even if you can't think of it, I would assume some advancement will occur (though perhaps a bit after lasers are powerful, as is normal with defensive technology lagging a bit behind). Who could have imagined self-guided missiles, 150 years ago? Given that real space combat is (unfortunately) probably at least that far off - and technology moving a LOT faster now - I certainly have no belief that I have any idea of the advancements that will occur in the meanwhile

"We don't know what we will invent" does not mean that we can assume that we could invent anything.

I don't see why not ... I certainly think that assuming things will be invented is more reasonable than assuming they won't be.

[snoopy369]

Originally posted by Kuciwalker

Missiles can continue ballistically without consuming fuel, so they can travel much longer distances.

Do you know how long it would take a missile going at non-relativistic speeds to hit a target that's "far away" (several light-seconds) for a laser?

Do you have any data on how much power it would take to make a military laser that could do significant damage at a distance of a light-second? I don't know exactly how quickly they disperse, but at a distance of a light second I would imagine the laser would be incredibly wide (I read that a laser from here to the moon would have a dispersion radius of a several mile:

http://sunearth.gsfc.nasa.gov/eclipse/SEhelp/ApolloLaser.html

) ... certainly a military laser would be more powerful than the research lasers they're using, but what order of magnitude more powerful would it need to be - and what power source would you need for that?

[Kuciwalker]

I include wave due to the fact that I am not an optical physicist and so don't know if a wave is possible or not. I mostly am imagining a particle screen that is made of highly reflective particles. Heck, even water particles would refract the laser ... put water in your hull so that when a laser hits the hull it comes out and refracts the laser.

Sigh.

You cannot rely on the optical properties of a material to effect a military laser. All materials will absorb some amount of the beam, and the laser will be strong enough that even that small part of the beam will be sufficient to destroy whatever optical properties the material has. If you try to use a mirror, the surface will be vaporized and will no longer reflect after the front of the beam hits it. If you use water, the water will be vaporized and become opaque, absorbing the rest of the beam and then exploding because you've just depositied a ton of energy in it. Same for any other system you conceive.

I'm not sure you are necessarily correct here, regardless of our current understanding of the matter. A laser over distance (as we're discussing here, remember; we're talking kilometers away) will be already somewhat dispersed, so if it's possible it will certainly apply in these situations.

To cancel out a wave you have to superimpose the exact inverse of that wave. You can only do that by producing another wave at the same place.

What we can make in space, who knows? Certainly more perfect mirrors than we ever could make here.

You will not make something with 100% reflectivity. It doesn't exist. Not to mention that our mirrors don't reflect much lower than the visible spectrum, so you just need an X-ray laser...

Or a substance that absorbs the heat and redirects it (a heat spreader), or even something that redirects the heat to a liquid medium that would turn the heat into power.

Timescale, timescale, timescale. Whatever the material is, it cannot redirect all of the energy of the laser in a couple milliseconds. The energy that is deposited will change the properties of the material sufficiently (e.g. by making it explode) to counter whatever defensive benefits it might have had.

The best defense against a laser of the power we're considering is thick armor, which is equally effective against missiles.

You are ignoring an awful lot of possibilities - and you yourself are assuming significant technological developments. Fortunately there are plenty of people out there who think outside the box, to make these incredible technological advances... sure, most of the above are probably impossible - but if one is not, that's a big thing in and of itself.

I'm making realistic extrapolations from known science while refusing to consider entirely new technologies without some explained mechanism. If you permit introduction of technologies without an explained mechanism you can prove anything - "zomfg energy shields are ubergood against lasers therefore only missiles are useful, clearly."

If we're at a point where space travel is commonplace, and in most of the discussed situations we have some method of surpassing light speed

Woah there, I've never admitted FTL as a factor here. You might as well introduce "energy shields". You can come to any answer you want if you can assume any technology you want.

then missiles certainly can still accelerate dramatically faster than a ship, and if you have a few thousand of them coming at you at once, how exactly will you stop them?

The energy source powering such a missile would power an even more powerful laser. (Again, I'm going to ignore any FTL suggestion that's not very well defined in advance.)

I don't see why not ... I certainly think that assuming things will be invented is more reasonable than assuming they won't be.

But not just anything will be invented.

[Kuciwalker]

I'm not sure how this is relevant to the question in the OP, to which I provided the most concise response: lasers have a limited range before the beam is too weak to do damage. Missiles can hit something much farther away, just at decreased effectiveness (given time to target, etc.). That's the real important difference, and explains fully the phenomenon question in the OP.

[snoopy369]

There's no way the earth could be round, either...

We're talking sci fi, Kuci. Nothing on either side is remotely feasible using current technology. Have a little fun

[snoopy369]

Originally posted by Kuciwalker
I'm not sure how this is relevant to the question in the OP, to which I provided the most concise response: lasers have a limited range before the beam is too weak to do damage. Missiles can hit something much farther away, just at decreased effectiveness (given time to target, etc.). That's the real important difference, and explains fully the phenomenon question in the OP.

I'm not sure why you went off on a tangent either We agreed at the start here...

[Seeker]

I'm glad that someone mentioned the weakness of nukes in space.

Unless a nuke is actually stuck right on the side of a space vessel, all you're going to get is the gamma radiation and a tiny little whiff of superheated gas from the actually bomb casing and bomb material.

Basically you might as well just use a big conventional explosive with lots of shrapnel then a nuke in space. It would do more damage.

Without an atmosphere, no big destructive shockwave, no massive transfer of heat.

[Whoha]

Originally posted by Kuciwalker

Missiles can continue ballistically without consuming fuel, so they can travel much longer distances.

Do you know how long it would take a missile going at non-relativistic speeds to hit a target that's "far away" (several light-seconds) for a laser?

A fairly long time, But so what, its not like the ships will be moving faster than the missiles will.

Overkill. Most of the energy from the laser will pass through the ship, while the warhead will vaporize the entire ship.

Lasers don't cut through ships. When the laser hits it vaporizes the surface it hits, but it doesn't annihilate the surface. The matter is still there and it continues to absorb most of the rest of the laser. Given the duration of the laser (probably a very small fraction of a second), this amounts to almost all of the energy of the laser deposited at one point on the surface of the ship at one instant.

Let me first say that this is shaping up to be one hell of a beam weapon. It can deliver atleast a megaton in a 20th of a second. That is damned impressive from every angle.

But there is still no way that the matter will absorb all that energy, and most of it is going out the other side of the ship.

Atmosphere behind the plating that just got vaporized will push it out.

Wrong timescale. That effect takes orders of magnitude longer than the duration of the beam.

There are 15 pounds of pressure per square inch exerting a constant outward push on the hull, the instant the hull can't hold it back it is pushing outward. It is anyone's guess how far away the vaporized matter will get before transfering what energy it has absorbed to the ship, but it isn't going to deliver all of its energy there.