Aristotle's conception of the goodness of a thing (which is not convincingly conveyed by the author) is essentially normatively neutral; a good knife qua knife for Aristotle is one that cuts well as a good nuclear weapon is one which is destructive. Using a nuclear weapon might not be good but just as a gun might be well-designed without being well-used I don't think it is too normatively concerning to be able to identify something as being a good example of its kind (a well-designed nuclear weapon), though I could be wrong!

The author was referring to good as in quality, not the good/evil dichotomy.

The US is apparently retaining components of some large H-bomb designs for "potential planetary defense purposes" - wouldn't that be a "good" function?

https://en.wikipedia.org/wiki/B53_nuclear_bomb#Role

If blasting other nations is your thing, then sure, why not?

Yeah, and that's why I'm doubting this definition is very useful.

Aristoteles should also have gotten a chicken plucked on the market square ...

>> First of all, what makes a thing a good thing? A good thing fulfils its unique function.

> Like a nuclear weapon?

If the device in question sets off uncontrolled nuclear chain reaction, then yes, it is good for its purpose as a nuclear weapon.

You are asking/implying: is the nuclear weapon's purpose good (in the first place)?

Something can be good for its purpose (e.g., electric chair [0]), but the good/badness of that purpose is a separate question.

[0] https://en.wikipedia.org/wiki/Electric_chair

A nuke can be good considered in itself (effective at leveling a city), and bad considered in relation the person who presses the button and thereby commits mass murder.

It is the latter that makes nuking a city a bad deed.

The ultimate goal of a nuclear a weapon (as of any weapon) is to keep peace.

As it is said in the art of war, the good general is the one who wins without having to draw his sword.

So a good nuclear weapon is one that you will never need to use.

"The ultimate goal of a nuclear a weapon (as of any weapon) is to keep peace."

This certainly does not seem obvious to me. It seems eminently arguable that the ultimate goal of a weapon is to make someone else do what you want or eliminate them or punish them if they do not. Or the ultimate goal of a weapon is to kill something to eat it. Or other stuff. When the first ape-map picked up the first jaw bone with the intent of bashing in another person's head, I doubt he was thinking "I'm looking forward to keeping this peace with this."