In brief, a scientist lady and her bloke along with her 18 (ho ho) year old daughter rattle around in an over-sized spaceship playing galactic "chicken" with stars which are about to explode, supposedly collecting scientific data. Escaped loony psycho turns up, gets himself invited on board and takes over ship. Scientist lady (who used to be a cop) turns into Rambo and duffs up loony psycho, rescuing daughter and bloke at the same time.
I found it difficult to believe that the "18" year old girl was actually 18 (I think that the actress who played her was in fact 23 at the time) - even when the psycho loony turned up he commented on how she looked older than 18. I also had difficulty with the whole business of them hanging around stars until the last moment before beating a hasty retreat - would any parent want to take their teen-aged daughter on such a dangerous mission?
The psycho loony seemed to be indestructible, resisting numerous attempts to rub him out. Sadly, he didn't exactly exude an air of menace (such as you would have got from, say, Oliver Reed or Anthony Hopkins); instead he came across as an annoying little tick who just happened to have a gun, and certainly did nothing to deserve his indestructible status.
In all, I quite enjoyed the film but wouldn't go mad on it - it has succeeded in avoiding my "for the car boot sale" pile for a couple of years now, so it can't be that bad.