Whilst designed for use with the Star Frontiers RPG originally published by TSR, the Sathar Destroyer would make an excellent alien vessel whatever ruleset you are using.
The first part describes the general style of the vessel, which is built by and for a race called the Sathar. If you need to know who they are, consult Frontier Explorer Magazine #6, which is available for free download here, although if you use this as a derelict alien ship to be explored, it is not so important to know about its original owners. The whole appearance is 'alien' and hints are given as to how to convey this to the party. The whole layout, too, reflects an alien philosophy and approach to life rather neatly.
This section is followed by an overall plan and detailed deck plans for each level. These are reference plans for referee use, there are also full plans - at a size suitable for miniatures or counters if you use them - provided as part of the download. Here, though, there are descriptions and notes on what is to be found where.
There's a short section on ancillary vessels - work pods, shuttles - and robots that are carried (which may or may not be present if a derelict destroyer is to be discovered; and then comes a section on shipboard life - assuming that the Sathar are there to enjoy it. A couple of pictures show you want they look like.
Overall, this is an interesting ship with a genuinely alien feel to it. Particular features are the low ceilings (1.5m), rounded corners on everything, the use of 'pool beds' for sleeping, relaxation and acceleration couches, and the fact that you cannot reach all parts of the ship - being a caste-based society, they see no need for interaction over and above basic communications between different areas. A spot of proofreading would have helped, but you can generally work out what was intended.