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General Information > Problems with Realistic Lasers v. Slugs and Missiles

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message 1: by Rikhard (new)

Rikhard Von Katzen (rikhardvkatzen) | 18 comments Lasers are problematic as weapons. Wobble at range means they waste a lot of their energy on a large surface area. They're also very ordered energy, and order means entropy, and entropy means waste heat: to create all that ordered energy for a laser beam you need to waste 99% of it. That means that before you turned that into a laser you had 100x more energy to use. Now some of this is inevitable: you'll probably have to turn the energy into electricity to make it useful in any kind of space gun. But between electricity and lasers there is a huge gap of wasted power.

Also, where does all that heat go? It has to go somewhere. If you up the power of your laser you get exponentially more wasted heat dumped right into your laser mechanism, power plant and - consequentially - your ship. There's another problem: lots of heat creates thermal lensing, and thermal lensing makes lasers even more ineffective and limits their range. Thus while lasers 'theoretically' have great range, they actually have shitty range.

In order to make a good laser you need a big power plant. Well, you can use that same power plant to shoot slugs out of a gauss gun or rail cannon with a lot less overall waste heat and a lot more on-target impact. A slug going really, really fast will deal out incredible amounts of damage as its mass is converted to plasma on impact. Guns are simply more efficient than lasers and, while slower traveling, simply don't have to hit as often. Guns also benefit from relative velocity: the faster you're going the harder your rail cannon hits. Going faster at an enemy slightly increases the frequency of your laser (blue shifting) but nobody is going to be able to tell the difference except a camera.

Moderate powered lasers have some practical utility in blowing up missiles, since they travel quickly and only need to do a little bit of damage to blow the missile off course/destroy it (missiles are basically bombs attached to bombs and are not very tough, tending to explode when you flick a pea at them). But as offensive armaments they leave a lot to be desired: they're too wasteful, too weak and the effective range sucks.

A realistic space ship is not going to be pulling 100Gs, either, so the difference in travel time between a laser and a slug might not make that much difference. At the range and speed a laser would make a difference it would suck anyway: it couldn't focus long enough on the same point to actually deliver serious damage. It would just heat up the surface of the target, and a bit of heat is precisely what transorbital spaceships are best at taking.

High energy lasers (soft X-ray) are generated by particle accelerators. That means that if you want to shoot a high energy laser you first have to have a complete particle beam gun that then uses free electron emission to shoot a laser. This is more conversion, more steps, more energy - more space, more entropy, more mass. This begins to make the 'unlimited ammo' angle less of an issue. If you need enormous heat sinks, a 2 mile long particle accelerator and unbotanium to build a functional weapon laser you could also use the same technology to build a rail-gun firing nuclear warheads for less money, less space, generate less heat and do more damage.

As popular as the Pew-ton beam is in science fiction the reality of space combat (if it ever happens, which is dubious) may be that boring old guns and nukes may still dominate until the end of time.


message 2: by Esha (new)

Esha Nas | 5 comments This is why BSG and a few other shows swap out their DEWs for KEWs.

An interesting compromise is the particle accelerator itself, but really, if we're having wars in space, we possibly have enough ISP to go around that we can have disposable munitions. Machine guns and strapped-on-missiles for earlier combat (1900-1970) with rail guns, gauss guns, magnetic accelerated weaponry et al taking over with more and more power and increasing speeds later.

This does turn the weapon itself into a fireworks show if hit, but there are always trade offs.


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