The right action in the right order

I don't often write detailed fight scenes into my work, but at the end of Renaissance I'm having to do something that works in the same way.  I have an AI which is opposing my boarding party.  All the human crew on the ship are dead, and it is having to improvise to defend itself.

The ship my characters are on has been used to recycle space junk.  That's why my centenarian main character, Elke, is with the team.  As the team get further into the derelict ship they encounter a series of dead ends created by the AI.  The only way to reach the bridge is through the ship's Belt Room.

Elke's own ship is a recycler too, so I'd already worked out how a Belt Room is supposed to operate.  It's the heart of the ship's recycling operation, the place where all the pieces of whatever scrap they're breaking up is scanned and separated into its different materials.  

I've written a detailed description of Renaissance's crew at work in the Belt Room early in the book, so the reader already knows how the machinery should work.

So I get Elke to say that a Belt Room is a dangerous place, and point out how people can lose limbs in the fast-moving machinery.  Originally I expected someone to get mangled up on the moving belt, or sucked up into one of the chutes, but the scene I wrote played out very differently.

I had to keep in mind that the AI was controlling the machinery.  It has no body of its own, so it's using the machinery in the Belt Room to defend itself.  Someone has loosened trucking and components on the ceiling, and these drop down onto the disintegrating belt and bounce off again, threatening my characters.  They're subjected to a rain of sharp pieces coming from all over the room.

Then I had the chutes that line either side of the belt start up.  They can only take small chunks of material, so when large pieces jam in them the material explodes, sending another shower of sharp  pieces flying off.  I've ended up with my characters trapped in the middle of a shooting gallery.  Good job they're wearing military EVA armour.

I've had to rewrite the scene twice already, and it still needs another pass.  Complex scenes like this one rely on the right action happening in the right order, and it has to be choreographed in detail.  I haven't got the order here quite right yet, so it's back to work to do another rewrite.