"How 'Powerful' is a 40 Watt phased plasma rifle?" Topic

" For an Author writing SF can be challenging for many reasons. Not least is the expectation that there must be some 'science' involved, especially for a 'hard SF' work. Often this results in lengthy and boring expositions where the technology, setting, or related paraphernalia is explained in detail. This isn't so bad; it is, after all, the reason many people read that particular kind of SF. A bigger issue is when the author adds in a random number, not always necessary, in order to imbed more firmly in his reader/audience's mind that this is 'science' fiction. But, often, the number is not as carefully selected as it should be. Most SF fans will not care, but for some of us fanatics it is a major annoyance.

The case in question is from Terminator, one of my favourite SF movies. The terminator is buying guns and asks the shopkeeper if he has a 'phased plasma rifle in the forty watt range'. So far so good. A single line that reinforces the fact that the terminator is a robotic killer from the future.

But I got thinking, is 40W really a good number? A big problem for hard SF authors wishing to include energy based weapons into their 'Verse is how much power to give them; making sidearms wight eh output of a thermonuclear warhead is an obvious no-no, for example. So I made the following table, 'translating' the output of several modern kinetic weapons into a 'Power' rating. It is not a perfect comparison, as directed energy weapons employ a different mechanism to do damage t the target than do KEW, but it provides a rough ballpark…"
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Amicalement
Armand

You'll shoot you eye out!

Game Designers' Workshop addressed the issue as early as 1983 in Striker, which allows players to design their own weapons, including plasma guns. You can determine blast radius and penetration using the design sequences.

Striker II and Fusion, Fire & Steel are later publications with similar functionality.

I've always assumed this line was BS: made-up jargon by a non-scientist writer. Maybe it was supposed to be 40 Mega Watts.

But googling this question, one discussion compares it to lasers. Surgical lasers are 5 watts. Most industrial cutting lasers are 1-2 watts. So a 40 watt laser might cause enough damage to be useful.

Those low wattage lasers aren't effective at combat ranges.

The answer is in the question.

A 40 Watt phased plasma rifle has a power of 40 Watts.

Now, while that may not sound like a lot to you, 0.5 Watts can light a fire with little problem.
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The real question what is the irradiance of a 40 Watt phased plasma rifle?
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Irradiance is power received by a surface per unit area. That is W/m^2

So it is a matter of focus. Typical CO2 lasers used to cut wood and such are 60 Watts, but home models are as low as 20 Watts. Now if your rifle can achieve a focus tighter than these lasers then, 40 Watts will cut through metal, or what have you.

Thanks!.

Amicalement
Armand

Just what you see, pal.

I'd want at least a 40 "kill-o-watt" laser, so it can do some real damage.

(smile)

Amicalement
Armand

Well, 40 watts per pulse is plenty if your rate of fire is 100s of pulses per second. You get a weapon that shreds flesh, but is useless against Terminators (in case the humans capture it.) It's essentially a fire hose of heat and pain which is great for close quarters combat in bunker.

Slight problem with the 100s per second, as Watts is Joules per second. J/s = W

That would result in just 0.4 Watts per pulse.

Better to think that 40 Watts is the average power, while the pulse power would be a function of the "duty cycle" and pulse width, which could be set be the user. Like a laser, let us say the pulse is short, very short! A femto-second

That would be 1.0X10^(-12) seconds with an instantaneous power of 4.0X10^13 Watts or 40,000 GigaWatts if you like.
But that is just one pulse per second. 40 Joules per pulse
A more practical 10 pulses per second yields 4000 GigaW per pulse. At 4 Joules per shot.

I can tell you from personal experience a 1 Joule pulse of a Femto-Second Laser can blow metal apart.

So, 40W is more the recharge rate then any other factor.