I'm not a writing teacher, and I'm not a copyright lawyer. However, it's an intriguing question, and so I'll take a swing at it, since you're asking about technology in science fiction novels - technovelgy! (Readers, prepare your comments.)

First, I'd distinguish between fan fiction (fanfic) and published, original works. At present, it appears that you can post a story online using anyone's characters, plots, technovelgy or settings, and no one cares. Yet. Lawyers are sharpening their pencils, so stay tuned. Note that you can't publish a word of it for money without permission.

I'd also like to distinguish between plagiarism (ethics) and copyright infringement (law). I'm assuming that you are interested in the ethical issue of when you can borrow and when you should not.

Science fiction authors certainly borrow from each other all the time; no story is completely original. However, let me see if I can't find some rules by using examples.

Consider the tractor beam. I'd distinguish two parts; the idea (a beam of energy that pulls on an object) and the name ("tractor beam").

The earliest use of the idea that I know about occurs in Crashing Suns, a wonderful 1928 novel by Edmund Hamilton. However, he called it an "attractive ray."

Three years later, 'Doc' Smith uses the same idea, but he calls it a "tractor beam in Space Hounds of IPC.

Four years after that, Jack Williamson calls it a "tubular field of force."

By the 1940's, the term "tractor beam" was in common usage; Murray Leinster, Theodore Sturgeon and others used the concept and the name.

Similarly, consider the space suit. The earliest reference (that I know about) to the idea that you might need something to protect your body in space appears in the 1898 novel Edison's Conquest of Mars, by Garrett P. Serviss. He refers to it as "air-tight dress" like a diver's suit.

The term "space suit" was used as early as 1931 in The Emperor of the Stars, by that great team Nat Schachner and AL Zagat.

Gordon A. Giles, in his 1937 short story Diamond Planetoid, wrote about a vacuum suit.

However, it was the term "space suit" that was picked up and used by Campbell, Williamson, Manning and many others.

There is one thing that I should point out: in that era, it's also true that lots of the stories were serialized in the same magazines, owners of the copyright in any case.

So where's that line between borrowing and plagiarizing?

If you used the term "tractor beam" or "space suit" today, they are a part of common usage. No one would question your ethics, and you'd probably need a good reason to make up your own word for either one. Readers would ask themselves "why didn't he just call it a tractor beam?"

So, I'd say that if a piece of technovelgy, like a tractor beam, is in common usage, you don't have to worry about plagiarism. You might be accused of using a boring sf idea, maybe, but not plagiarism.

Clearly, originality is highly prized in science fiction writing. If you must use an existing idea, you must do something original with it, or extend its use or functionality.

For example, the idea of something that flies through the air to watch what people are doing is an old idea. So, original writers think of original ways to do it. Consider this progression of ideas:

• Raytron Apparatus from Beyond the Stars by Ray Cummings(1928)
• from by (1928)
• Scarab Insect Robot from The Scarab by Raymond Z. Gallun (1936)
• Flying Eye from The Repairman by Harry Harrison (1959)
• Stick Tight from The Star King by Jack Vance (1964)
• Copseye from Cloak of Anarchy by Larry Niven (1972)
• Tracer Bird from Changeling by Roger Zelazny (1980)
• Aerostat Monitor from The Diamond Age by Neal Stephenson (1995)
• Bee Cam from City of Pearl by Karen Traviss (2004)

I'd also argue that there are sets of technovelgy. For example, if you told me about a novel with things like a carryall, crysknife, distrans, ego-likeness, fencing mirror, lasgun, and semuta, I'd say you were talking about Frank Herbert's Dune. I don't think you could write a novel with this set of terms without being justly accused of plagiarism (and possibly copyright infringement, since particular authors have been given permission to write in the Dune universe).

I think that there are concepts that everyone borrows. In many cases, the concept is common usage, but the particular expression (the name and the details) should not be copied.

For example, no one owns the idea of a "robot." However, if you use words like wabbler, electric sheep, golden shuttles, droid, robass or hired girl to describe your robot, you're plagiarizing someone else's work.