Writing science fiction; description trouble...

I'm having a hard time writing the parts of this new novel that describe the settings and the characters. Which is very strange -- because I can, with my mind's eye, see all of those settings and characters in vivid detail. That should mean, logically, that all I have to do is write down what I see, right? But I'm having endless trouble doing that in a way that would be interesting to readers. I keep writing descriptive sentences [and paragraphs:] that sound like specifications from technical ...