Would Kirk plowing ahead into the barrier count as a nonsensical course of action? I always forgive it because the episode is so good and it needs to happen, but looking at the barrier makes one wonder why he doesn't fly over or under it. Non canon explanations aside.
One) possibly that is a special effects failure and in "real" life no way "over" or "under" the barrier was visible..
Two) possibly an interaction between the barrier and the approaching spacecraft makes the barrier form and intensifiy as a relatively flat line in front of hte Spacecraft, and no matter where thte spacecraft went the barrier would and srengthen right in fornt of teh spaceship.
Three) Possibly the barrier was equally strong in all directions leading out of the galaxy, but some quirk about its nature made it appear as a thin band in frotn of and approaching space ship. The thin band could be some sort of refelction from the physical barrier which shpfted invisible radiation into the visible spectrum, but only right in front of where the ship was heading.
So here are three theories explaining why it wouldn't have done any good to try to go "over" or "under" the barrier.
And here is a fourth theory: Kirk should have tried to go "over" or "under" the barrier, and Ssosmcin is correct that it was a mistake made by Kirk..
Take your pick, or think of other theories.
You can't take visual effects literally. I mean, TOS had starscapes with moving stars even when the ship was at impulse, and the stars moved far faster than parallax would allow even at high warp. Then there's the way the ship visibly follows a curving path when orbiting a planet, which is nonsense. I mean, on a planet's surface, the curvature is so wide that the ground appears flat to the eye. An orbit hundreds of kilometers up would be a much larger ellipse and thus would look far flatter, so the ship should appear to fly perfectly straight.
And later Trek perpetuates the problem of depicting things in space as 2-dimensional when they should be 3-dimensional. The example that annoys me most is the "ripple" effect of the Praxis explosion in ST 6, because so many other productions adopted it later on.
But if you want an explanation for the "ribbon" appearance, maybe it's an illusion due to the way the barrier polarizes light or something. By analogy, think about looking at a reflective surface that's curved into a cylinder. Only the middle part reflects light into your eyes, while the other parts reflect it elsewhere, so you only see a glint on the middle part.
So Christopher also thought of my suggestion number one.
About orbiting starships. I have often noted that they seem to be turning at a rate which would made a full circle only a few kilometers or miles in diameter.
Thus my theory is that Starships often travel in an aeronautical orbit instead of an astronomical orbit. In an aeronautical orbit, an aircraft moves in a closed figure near an airfield waiting for clearance to land, and of course it is powered all the time it is making that type of orbit. So I suspect that starships are often in powered flight above a planet's surface, and try to stay above a spefic spot on the planet's surface while being far too close to the planet to be in a geosynchronous orbit. Thus they have to constantly use power to hover above th the spot they want, and will start to fall as soon as they loose engine power.
And apparently there is some technical reason why the starship can't stay in the exact position it wants but has to constantly circle around in a closed pattern with a diamter of a few kilometers or miles.
And somewhere, possibly on this BBS, and probably this year, I read a statement claiming there was some sort of proof that starships don't in fact travel in tiny circles above planets. But I didn't see that video and don't know what their argument was.
