was the atmospheric processor built on the ruins of engineers?

The atmospheric processor was designed by Ron Cobb for Aliens (1986)

Based on the concept art, and Ron Cobb's approach to such things, it's likely it was always intended to be Human technology

Although the idea is intriguing, it is not.

The reactor was covered in xenomorph slime.

I have always think that the lower parts of the processor with strange shapes were the work of xenomorphs, i.e. their socket.

That is a great observation, but I agree with Leto. If it were the case that it was Engineer technology, that brings up the question of why the people there never mentioned it (I am referring to the Director's Cut).

Same designer, so I guess he ripped off himself.

wtf?! Hadley's Hope has one of the best & most recognizable sci-fi designs.

Agree with LETO on this.....the Sulaco was well designed for its time and still looks good to this day in my opinion....as well as the large Atmospheric Processing planet....."it's a rock no indigenous life." So no engineers there...and if they are there the place was nuked.

I like many of the designs in Aliens....the weapons....the lab, the inside of the ship....the sleep chambers, the WY complex......that was a cool movie overall for its time.....would challenge anyone to do better. Say what you will about Cameron but he gets stuff done! The Alien Queen Priceless special effects....but hey if anyone wants to throw it all under the bus I really could care less....its not going to stop me from enjoying it one bit.....

Anyone seen or heard from BIG DAVE!.....BigDave where are you old Chap!!!!!!

It's an interesting idea, although I doubt it.

“it seems that they are not part of the ship but a structure underground.”

Scott has at different times said that the ship (1979) was like a bombing-plane with the eggs being like bio-bombs. You can try to find interviews where he mentions that. This probably means that the derelict was big and the place where they found them was like a storage of some sort.

It's possible to question if the scale makes sense but that was the point of that room as far as I know. At least with how it looks it makes it more mysterious. Kane went down there and said that it was a cave of some sort but he probably compared it to what he had seen before, he could be mistaken. Keeping that comment in mind I find it reasonable that some people might not think that it is a part of the ship but I don't think that it is.

The walls of the 'egg cave' are identical to those in the chamber above (a result of having re-used the set).  So either it's part of the Derelict or an Engineer complex like the pyramids on LV-223.  (And Ridley talks about the bomber thing on one of his commentaries from memory).

Either way, the similarity to an Alien hive is only very superficial.

Didn't they have to scrap the story of a pyramid and roll it into the derelict? I think if so then the derelict could be re-configurable and the bomber from the prequels was tooled up to be a transport making the pilot deck higher up and the lower deck for carrying stuff. It could just be a different model of the ship, an older design or something like that.

I like many of the designs in Aliens....the weapons....the lab, the inside of the ship....the sleep chambers, the WY complex......that was a cool movie overall for its time.....would challenge anyone to do better. Say what you will about Cameron but he gets stuff done! The Alien Queen Priceless special effects....but hey if anyone wants to throw it all under the bus I really could care less....its not going to stop me from enjoying it one bit.....