In the movie, we barely have any information on the Alien's physiology and biology. Especially the adult alien, as it obviously is really hard to study.
In the extended lore, there are two explanations for those protrusions. One is that the alien breathes through them - kinda boring explanation. The other is: the alien secretes spider silk like substance through those, which allow it to stick to surfaces like a spider, and this might be the same substance it uses to cocoon its victims.
I myself subscribe to the latter explanation, but I am fine with having no explanation at all - because the title is "alien" so it is perfectly OK if we don't know all the details about how the monster works - it is still effective.
As fot the design: the "pipes" on its back are an upgrade, makes the design even more alien and biomechanical. It is something strange, something not immediately obvious what it is for. We see the "hands" and "feet" of the alien and we are like "yeah, it is walking, grabbing things, etc." - we have something to go on to make sense of those appendices. With the pipes, we don't have anything to go on, and that makes this effective. And it makes it effective, because the alien's design as a whole makes sense. We just don't know how ALL the parts work - and that's part of the intrigue, the mystery, the beauty of it.
One is the most common way of using this phrase - rational sense.
But the other is intuitive sense. When you cannot dissect the thing you are taking about, and don't understand it rationally, but it "feels right" in the sense that you have a high level understanding of it.
The alien's design is the latter. And I think you interpreted my comment from a rational standpoint, rather than an intuitive one. And I have the proof as well, as you earlier said in your OP: "And what about the big smokestacks on his back?"
This question is very telling. It clearly shows that you encountered something weird, something alien, and you have a need for understadning, more precisely rational understanding. So you are trying to make rationals sense of it, you are trying to compare the protrusions to something that is familiar and known to you (smokestacks).
Even from that standpoint however, I fail to see how one would consider the statement that the alien's design makes sense as "comedic". As a design of an organism - be it artificial or natural - it makes sense. When it comes to artistic intention, the protrusions are not just randomly thrown there, Giger had something in mind when he added those. We don't know what exact function does it serve? Well, that's unfortunate if you want to 100% understand everything about the alien, but the point of the movie is that the alien is alien. The artistic intention of the whole movie and the design itself is that we don't know, we cannot know everything about how it works. And that adds to the atmosphere, the creepiness, the cosmic horror.
There is nothing wrong with the need to understand everything rationally - it is after all, human nature. But this is one of the main messages of Alien: we (humanity) can often find ourselves in situations where we don't have all the information, where we don't have the chance to get the full picture. And we must cope with that somehow...
You remind me of the supporters of the Palestinians ... you will go to any lengths to rationalize your totally wrong opinion. I hate people like that. You're not even human, you're just a robot who doesn't even understand or question your programming.
The inner jaw is a great piece of biomechanical design. It is "on rails" because that is the mechanical part of the design.
You can dislike it, don't get me wrong, but there is a clear artistic intention behind how it looks and why it looks like that. In the movie, we cannot decide if the alien is a product of natural or artificial activity. And that duplicity is part of the design. It is dubbed "biomechanical", and it is a unique artstyle, that convinced Scott, O'Bannon and co. to hire Giger to craft the alien.
The mechanical mouth and the whole skull was built by Carlo Rambaldi, who is a pro in animatronics, and together with Giger, Scott and all others involved, they were all satisfied with the end result, the way the mouth moves, etc. So there is no doubt that the "on rails" nature of the movement is intended. Moreover, it is clearly offset by the vast amounts of saliva we see, which is clearly a very organic thing to include, further emphasizing the dual nature of the alien.
Its a great monster Giger designed no doubt . the best ever imo.
But I've never heard this "bio mechanical" side put forth before and I dont think thats what they were going for
I guess these latest Prometheus movies showing it was manufactured might lend some creedence to that bit I dont think they ever intended any kind of mechanical element in the beginning
Very quickly I looked up some articles, and found this:
Giger painted a biomechanical landscape of strange shapes formed out of twisted metal and bone. “I wanted the landscape of the planet to be biomechanic,” said Giger, “a mixture of our technology and some kind of magma, so as to create the feeling that maybe something has happened before on that planet, maybe a technical civilisation has been destroyed.”
So the artificial, technological origins of the alien were intended right from the start. During production, the idea of the alien being a weapon used by the Space Jockeys is floated numerous times.
Also, this statement from Ridley Scott is very telling:
The purpose of the derelict craft is left a mystery in the film. “I was amazed that no one asked me about this mysterious element of the film,” Scott said to French magazine L’Ecran Fantastique in 2012, “but if you would have asked me in 1978, I would have gladly explained that, in my mind, all this alien ship could be was a battleship.”
So yes, the idea of the alien being artificial, manufactured, a bioweapon in itself - was present throughout the making of the film.
Also, with this in mind, Cameron's idea for Burke to acquire aliens for "the bioweapon division" gets a weird meta layer. Burke is thinking about how the alien's acid, or other bodyparts could be used to create weapons. But the alien itself is already a bioweapon... Bizarre :-)
I think the alien's biology was supposed to seem impossible, like it defied the rules of biology in some ways. That made it very unpredictable. There was no knowing what it was capable of.
I think they were successful in creating one of the most terrifying monsters in movie history.