Handheld energy weapons

[Rynn]

Okay, you have a point there. Having mature nanotechnology imbedded into a plasma rifle could help overcome some of the reliability problems. But how well can nanomachines handle high temperatures? Would they be able to patch up erosion spots in the barrel of a plasma rifle thats glowing white hot?

Not a lot of complex chemistry survives incredibly high temperatures so likely not, though I'm not terribly convinced that a plasma "rifle" is possible. Most things I've read on plasma weapons talk of them being short range vacuum weapons. In any case the point being that if you make the weapon incredibly sturdy and include active internal repair you can mitigate the complexity cost to boost the ROI.

But that raises a question for me, how many different ways are there to design the same tool, especially if its something simple in nature? Lets say that in OA, you have primtech enthusiasts who like to use automatic rifles and gasoline engines: Would they look anything like the analogues we use today? Would a rifle built in the future use fundamentally different mechanical principles to achieve the same thing?

Fundamentally I suspect not. Practically there will likely be all sorts of improvements. On the minor improvement front consider how much more ergonomic rifles are today compared to one hundred years ago and how much more sophisticated ad-ons like scopes are. As a more major example improvements in materials science could lead to all sorts of drastic improvements; tougher components with stainless surfaces could allow for more powerful chemical propellant, foamed diamondoid casing could make a much lighter rifle etcetera. Beyond that you can work in highly reliable smart features like gyroscopic stabilizers, Friend-Foe trigger release and bullets that can do anything from track their target to be rapidly printed from stock metal powder to create a variety of types (piercing, hollow-point) on the fly.

A good comparison over guns (which are a relatively recent invention) would be bows. Bows and arrows have existed for thousands of years and fundamentally they operate the same today as they have done since ancient times. But if you compare a modern olympic bow (made of lightweight composite materials with balance stabilisers and fibre glass arrows) to one from any other point in history there's a marked improvement.

Yes, but a fighter jet is an actual weapons system with many other sub-systems in its frame. Airborne fighters are going to be complex regardless of what you do (not so for a rifle). The cost/benefit analysis is different for them than for monolithic items like howitzers, mortars, and small arms.

Part of what I was getting at is that in OA a "soldier" is a weapons system with many other sub-systems in its frame. The increased complexity over a meat body with a chemical/mechanical bang-bang tube pays dividends in performance despite the greater failure modes.