Viable Energy Beam

Question

I've researched into lasers, plasma weapons, sonic weapons, basically everything I can think of, and I can't find any kind of energy weapon viable as a hand-held or even vehicle mounted weapon. Lasers can be easily reflected, they have to be held on-target to inflict damage, they can be nullified by something as simple as a dust cloud or a mirror, and their power-output ratio is ridiculous for a mounted or hand-held weapon. Plasma have very similar problems, but mainly power. I don't want my soldiers each carrying a nuclear powerplant on their backs. Is there, even a theoretical energy that can be fired as a beam or projectile and preferably not have to be held on-target for more than a few seconds?

If there really is no alternative without unobtanium then I'd accept something that can fire a projectile at railgun or better speeds, if that means a power-efficient railgun then that's fine.

Edit: This is pretty far beyond our tech, while I'd like to keep the theoretical as human these weapons will be landing in alien hands.

Answer 1

Kinetic weapons can always deliver more energy to the target than an energy weapon for the same input energy, and the farther the distance the bigger the divergence. But if you want high power a railgun is going to give you better results than a laser for the same energy output. The energy transfer gets more efficient the larger the particle is, and you just follow that to its logical conclusion, a big nugget of particles delivered all at once, aka a bullet.

If you want super high energy in a portable means think less about batteries and more about single use reactions. Instead of having the capacitor and power supply in the gun, just swap out capacitors like ammunition, and have a single external power supply per team.

You could imagine each team carrying one nuclear battery to recharge/top-up between fights, the actual projectile is barely noticeable weight wise, since you're basically looking a a bullet without a casing. Most of the weapons mass is the insulation to keep the arc from killing the person firing it.

But even with that explosion propelled projectiles are just going to be better against infantry, railguns would be reserved for anti-vehicle. You just don't need all that much energy to kill a person. Now I expect see switching to caseless ammunition for infantry in the future, much less weight for the same killing power. Now you could see better bullets, smart bullets, micro-grenades, or HEIAP as standard ammunition.

But remember this is all dependent on how far in the future you are talking about. If you really want to dive deep into this the Atomic Rockets people have pages dedicated to theoretical weapon calculations, including sidearms.