a) Ron's important story contribution
Dan O'Bannon discussed his problems about the alien with Ron Cobb
He said to Ron "What really bothers me about the whole idea of this thing running around the ship is why they didn't just kill it. Why didn't they spear the goddamn thing? Or shoot it with some kind of gun that wouldn't go right through it and penetrate the hull? Or why couldn't they get a bunch of long pointed shafts and drive it into the airlock?"
Ron replied "Well, why not give it extremely corrosive so that would like burn through metal."
This was another odd but great idea for Dan, he replied "Great, then they couldn't kill it because then its blood would eat a hole in the bulkhead and the ship would lose all it's oxygen. Well that doesn't make much sense; but it would certainly make it very, very difficult for them to deal with it on board the ship."
So Dan put it in and was very proud of Ron for having that idea and this was something that also interested the Brandywine Productions producer Walter Hill when he would come to read the script.
b) Acid for blood scene as a confused echo of Star Trek"The Survivor"
There was also the episode of Star Trek The Animated Series to consider where an alien who scould rearrange its molecules who had got aboard the Starship Enterprise had disguised itself as an examination table and Captain Kirk threatened to pour a highly corrosive acid onto it if it didn't reveal itself, and I decided that they had seen this cartoon and the scene served as a catalyst as they imagined what this acid might do in a space ship if it was poured in a similar context, but while it remained in a medical bay at an examination table, with an alien, it became the alien's blood that was a "molecular acid" as they failed to extract it from Kane's face. (See: Star Trek The Animated Series, Episode 6: "The Survivor")
c) Ridley's reponse
Ridley Scott's thoughts about this was that it was a perfect defence, and he thought that Dan O'Bannon liked Ron's idea for the acid blood because it was like the ants that squirt acid to combat enemy ants. Back in the time of the making of alien, one had to consult books and watch documentaries which is rather different to the 21st century where one has access to all of this knowledge at the touch of a button through photos and videos on the internet.
- A key element in the face-hugger sequence was the realization for the crew that they are dealing with a creature infinitely more dangerous than even the ferocity of its initial onslaught had suggested.. When efforts to pry the tenacious beast from Kane's face prove unfruitful. Ash and Dallas mount a more direct assault by attempting to amputate one of its fingers. At the first incision, however, a yellowish fluid oozes from the wound. In the penetrating two decks of the ship and threatening the hull before its virulence dissipates (Cinefex 1, p56)
- Dan O'Bannon: You know, Ron Cobb gave continual input to the film right from the very start. He gave us one of the major plot elements, the monster has an incredibly corrosive bloodstream, one of the reasons the monster can’t be cut up or fired at is that its blood would eat right through the ship. That was Ron’s idea and I want everyone to know it. (Film Fantasy magazine https://futurism.media/interview-with-alien-co-creator-dan-o-bannon)
- Dan O'Bannon: What really bothered me about the whole idea of this thing running around the ship was why they didn't just kill it. Why didn't they spear the goddamn thing? Or shoot it with some kind of gun that wouldn't go right through it and penetrate the hull? Or why couldn't they get a bunch of long pointed shafts and drive it into the airlock? I mentioned that to Ron Cobb and he said "Why not give it extremely corrosive blood that would eat through the hull?" And I said "Well that doesn't make much sense; but it would certainly make it very, very difficult for them to deal with it on board the ship" so I put it in." (Cinefex 1, p56)
- Dan O'Bannon: You know, Ron Cobb gave continual input to the film right from the very start. He gave us one of the major plot elements, the monster has an incredibly corrosive blood stream, one of the reason the monster can't be cut up or fired at is that its blood would eat right through the ship. That was Ron's idea and I want everyone to know it. (Fantastic Films Number 10, p12)
- Dan O'Bannon (1:13:05) :I was stuck on one point which was, once they got the thing on the spaceship, I wanted to avoid the cliché of bullets bouncing off of the thing, the indestructible monster, I mean that's the ancient cliché right, you can't stop it, bullets wont stop it, not at all, i wanted the thing to be in every respect, in every respect a natural animal, which means, yes, if you shoot it, it will die, so the question was, in the second half of the movie, why don't they just kill the thing, why didn't they just squash it, right, stick a knife in it, whatever and I wasn't sure how to achieve that and I asked Ron Cobb if he had any thoughts. Ron Cobb I remember who was always helpful said, "well, suppose the thing bled acid that would like burn through metal." I said "great", I said "then they couldn't kill it because then it would er, it's blood would eat a hole in the bulkhead and the ship would lose all it's oxygen", I said "great". (Alien Quadrilogy and Blu-Ray commentary)
- Ecran Fantastique: D’où vient l’idée du sang à base d’acide qui ronge tout sur son passage?
Ridley Scott: Je crois que c’est le designer Ron Cobb qui l’a suggérée, comme moyen de défense idéal : blesser un alien devient ainsi aussi dangereux que l’affronter. Le scénariste d’Alien, Dan O’Bannon, a hélas disparu en 2009, mais il me semble que Dan avait aimé cette idée de Ron parce qu’elle lui rappelait ces fourmis qui projettent, des jets d’acide pour combattre des fourmis ennemies. Vous seavez. il suffit de se documenter un peu pour trouver des choses étonnantes dans la Nature. à l’epoque d’Alien, il fallait consulter des livres, visioner des documentaires, et cela prenait du temps, mais aujoud’hui, il suffit d’explorer le web pour tomber sur des vidéos ou des photographies tellement incroyables que vous ne pouvez que vous exclamer “Mais qui a conçu cela ?!“ avant des vous rappeler que c’est l’œvre de la Nature, ou de Dieu le pére, si vous êtes croyant!Translation
EF: Whence the idea of blood acid which corrodes everything in its path?
Ridley Scott:I believe that it is the designer Ron Cobb who has suggested it, as a perfect defence: hurting an alien becomes as dangerous as confonting it.... The screenwriter of Alien, Dan O'Bannon, has unfortunately disappeared in 2009, but it seems to me that Dan had liked Ron's idea because it reminded him of these ants that spay jets of acid to combat enemy ants. You know. it is sufficient to document a bit to find amazing things in Nature. At the time of Alien, he had to consult books, watch documentaries, and it took time, but today just to explore the web for falling on videos or so amazing photographs that you can as exclaim you "but who designed this?" before reminding you that it is the work of Nature, or God the father, if you are a believer! (L'Ecran Fantastique Hors-Serie 20)
- Walter Hill: They had also worked out an interesting problem, which is: how do you destroy a creature you can't kill without destroying your own life-support systems. ('Kill By Mouth: Neon (UK). December 97,)