Tuesday, 28 July 2015
Random Numbers: How 'Powerful' is a 40 Watt phased plasma rifle?
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.
Energy = (Mass * Velocity^2) / 2
mass in kg, velocity in m/s, energy in joules
Power = (Energy * RPM) / 60
It was pointed out in the comments that I had inadvertently used the wrong equation. I've fixed that, and the table is updated as well. If I've made any other errors feel free to point them out