I just can't wrap my head around this. And it is present everywhere! Movies, Games, TV Series, you name it!
They are bloody energy weapons. Did anyone even bother considering how the recoil is generated in the first place ?
I mean, seriously, firing advanced laser weapons and the gun kicks back. Why? There is no force in play there. A laser gun is literally a beam, fired either consistently or in small bursts. A high powered ray of light. How can that generate recoil?
As for plasma weapons, they are firing streams of plasma(duh). Seriously, plasma is just superheated gas (ok it's not as simple as that, but I am trying to keep it simple) It doesn't involve conventional ballistics in launching it, how can the plasma stream produce recoil?
Am I really the only one who cannot make any sense out of this?
Lemme let you in on what momentum (recoil) is: p=mv. The velocity of the light will be 3x10^8, yet the mass will be so small that it won't matter.
Momentum is not recoil. Recoil is a force imparted to the launcher that is equal in magnitude to the force imparted to the projectile. What you are calculating, therefore, is the energy required to drive a 1kg launcher backward at 300000000m/s. In terms of firearms, that's a bit much.
When firing light, the recoil is a product of radiation pressure, so the equation we should be using is this:
P = Ef/c
where P is pressure and Ef is a measure of Watts per unit area
Let's say the launching surface is 1cm², and the emission pressure is something more reasonable like 20N/m².
Sure, 600kJ/s is a lot (about 1/3 of the intended output of the Laser Mégajoule stretched over 1 second), but it is at least within the realm of possibility for laser weapons. 90 petajoules is not.
I found an old blog article about recoil in laser guns. After stating that yes, laser guns would certainly have some recoil, he also tried to calculate just how much that would be. Conclusion: a laser gun firing a pulse of light with the same energy as a bullet has kinetic energy would lead to a comparable recoil according to his calculation. However, as addressed in this other blog article (in response to the first one), given that the recoil would last an extremely short time, we may not even be able to feel the recoil.
A mathematician or physicist will be in a better position than me to tell whether the calculations are sound, but I like their ideas anyway.
Yes, there should be some recoil.
I'm no expert in physics, but
Laser:
There is something called "solar sail" that works in real life and relies on being impulsed by light like if it was wind.
Light carries energy, if you concentrate the necessary amount of light, very concentrated impulses of energy would be like hurricanes to solar sails. It appears on the entry.
