It's the mostly forgotten 1987 movie Nightflyers, based on the 1979 novella of the same name.
It was produced on a modest budget, starring '80s B-movie queen Catherine Mary Stewart, Robin Hood's Michael Praed, and rocker turned actor Michael Des Barres. The effects and model work are actually not that bad for a low budget flick that went more or less directly to video, and to be honest, it actually starts out promisingly. The set design has a cheap but appealing aesthetic that will remind you of the Max Headroom TV series — think Ridley Scott on a budget. But as the movie progresses it starts to give in to dumb B-movie cliches and abandons most of Martin's plot. There is also a lot of '80s hair.
As far as I can tell, it was never released on video beyond a VHS cassette in the late '80s — there was no DVD, and the production company is long gone. I remember that Martin had some good words for the project when it was being made, though he wasn't involved with the movie, and he never mentions it in interviews. However, some intrepid soul has uploaded the entire thing to YouTube, and so for the time being the mystery of the volcryn is yours to discover, though I'd stick to the source material.