O'Bannon brought in artists Ron Cobb and Chris Foss (with whom he had worked on Dark Star and Dune, respectively) to work on designs for the human aspects of the film such as the spaceship and space suits. Cobb created hundreds of preliminary sketches of the interiors and exteriors of the ship, which went through many design concepts and possible names such as Leviathan and Snark as the script continued to develop. The final name of the ship was derived from the title of Joseph Conrad's 1904 novel Nostromo, while the escape shuttle, called Narcissus in the script, was named after Conrad's 1897 novella The Nigger of the 'Narcissus'. The production team particularly praised Cobb's ability to depict the interior settings of the ship in a realistic and believable manner. Under Ridley Scott's direction the design of the Nostromo shifted towards an 800-foot (240 m)-long tug towing a refining platform 2 miles (3.2 km) long and 1.5 miles (2.4 km) wide. Cobb also created some conceptual drawings of the Alien, but these were not used. Moebius was attached to the project for a few days as well, and his costume renderings served as the basis for the final space suits created by costume designer John Mollo.
The sets of the Nostromo 's three decks were each created almost entirely in one piece, with each deck occupying a separate stage and the various rooms connected via corridors. To move around the sets the actors had to navigate through the hallways of the ship, adding to the film's sense of claustrophobia and realism. The sets used large transistors and low-resolution computer screens to give the ship a "used", industrial look and make it appear as though it was constructed of "retrofitted old technology". Ron Cobb created industrial-style symbols and color-coded signs for various areas and aspects of the ship. The company that owns the Nostromo is not named in the film, and is referred to by the characters as "the company". However, the name and logo of "Weylan-Yutani" appears on several set pieces and props such as computer monitors and beer cans. Cobb created the name to imply a business alliance between Britain and Japan, deriving "Weylan" from the British Leyland Motor Corporation and "Yutani" from the name of his Japanese neighbor. The 1986 sequel Aliens named the company as "Weyland-Yutani", and it has remained a central aspect of the film franchise.
Art Director Roger Christian used scrap metal and parts to create set pieces and props to save money, a technique he employed while working on Star Wars. Some of the Nostromo's corridors were created from portions of scrapped bomber aircraft, and a mirror was used to create the illusion of longer corridors in the below-deck area. Special effects supervisors Brian Johnson and Nick Allder made many of the set pieces and props function, including moving chairs, computer monitors, motion trackers, and flamethrowers.
H. R. Giger designed and worked on all of the alien aspects of the film, which he designed to appear organic and biomechanical in contrast to the industrial look of the Nostromo and its human elements. For the interior of the derelict spacecraft and egg chamber he used dried bones together with plaster to sculpt much of the scenery and elements. Veronica Cartwright described Giger's sets as "so erotic...it's big vaginas and penises...the whole thing is like you're going inside of some sort of womb or whatever...it's sort of visceral". The set with the deceased alien creature, which the production team nicknamed the "space jockey", proved problematic as 20th Century Fox did not want to spend the money for such an expensive set that would only be used for one scene. Ridley Scott described the set as the cockpit or driving deck of the mysterious ship, and the production team was able to convince the studio that the scene was important to impress the audience and make them aware that this was not a B movie. To save money only one wall of the set was created, and the "space jockey" sat atop a disc that could be rotated to facilitate shots from different angles in relation to the actors. Giger airbrushed the entire set and the "space jockey" by hand.
The origin of the jockey creature was not explored in the film, but Scott later theorized that it might have been the ship's pilot, and that the ship might have been a weapons carrier capable of dropping Alien eggs onto a planet so that the Aliens could use the local lifeforms as hosts. In early versions of the script the eggs were to be located in a separate pyramid structure which would be found later by the Nostromo crew and would contain statues and hieroglyphs depicting the Alien reproductive cycle, offering a contrast of the human, Alien, and space jockey cultures. Cobb, Foss, and Giger each created concept artwork for these sequences, but they were eventually discarded due to budgetary concerns and the need to trim the length of the film. Instead the egg chamber was set inside the derelict ship and was filmed on the same set as the space jockey scene; the entire disc piece supporting the jockey and its chair were removed and the set was redressed to create the egg chamber. Light effects in the egg chamber were created by lasers borrowed from English rock band The Who. The band was testing the lasers for use in their stage show in the sound stage next door.
Spaceships and planets
I resent films that are so shallow they rely entirely on their visual effects, and of course science fiction films are notorious for this. I've always felt that there's another way to do it: a lot of effort should be expended toward rendering the environment of the spaceship, or space travel, whatever the fantastic setting of your story should be–as convincingly as possible, but always in the background. That way the story and the characters emerge and they become more real.—Ron Cobb on his designs for Alien
The spaceships and planets for the film were shot using models and miniatures. These included models of the Nostromo, its attached mineral refinery, the escape shuttle Narcissus, the alien planetoid, and the exterior and interior of the derelict spacecraft. Visual Effects Supervisor Brian Johnson, supervising modelmaker Martin Bower, and their team worked at Bray Studios, roughly 25 miles (40 km) from Shepperton Studios where principal filming was taking place. The designs of the Nostromo and its attachments were based on combinations of Ridley Scott's storyboards and Ron Cobb's conceptual drawings. The basic outlines of the models were made of wood and plastic, and most of the fine details were added from model kits of warships, tanks, and World War II bombers. Three models of the Nostromo were made: a 12-inch (30 cm) version for medium and long shots, a 4-foot (1.2 m) version for rear shots, and a 12-foot (3.7 m), 7-short-ton (6.4 t) rig for the undocking and planetoid surface sequences. Scott insisted on numerous changes to the models even as filming was taking place, leading to conflicts with the modeling and filming teams. The Nostromo was originally yellow, and the team filmed shots of the models for six weeks before Johnson left to work on The Empire Strikes Back. Scott then ordered it changed to gray, and the team had to begin shooting again from scratch. He ordered more and more pieces added to the model until the final large version with the refinery required a metal framework so that it could be lifted by a forklift. He also took a hammer and chisel to sections of the refinery, knocking off many of its spires which Bower had spent weeks creating. Scott also had disagreements with miniature effects cinematographer Dennis Ayling over how to light the models.
A separate model, approximately 40 feet (12 m) long, was created for the Nostromo's underside from which the Narcissus would detach and from which Kane's body would be launched during the funeral scene. Bower carved Kane's burial shroud out of wood and it was launched through the hatch using a small catapult and filmed at high speed, then slowed down in editing. Only one shot was filmed using blue screen compositing: that of the shuttle racing past the Nostromo. The other shots were simply filmed against black backdrops, with stars added via double exposure. Though motion control photography technology was available at the time, the film's budget would not allow for it. The team therefore used a camera with wide-angle lenses mounted on a drive mechanism to make slow passes over and around the models filming at 2½ frames per second, giving them the appearance of motion. Scott added smoke and wind effects to enhance the illusion. For the scene in which the Nostromo detaches from the refinery, a 30-foot (9.1 m) docking arm was created using pieces from model railway kits. The Nostromo was pushed away from the refinery by the forklift, which was covered in black velvet, causing the arm to extend out from the refinery. This created the illusion that the arm was pushing the ship forward. Shots from outside the ship in which the characters are seen through windows moving around inside were filmed using larger models which contained projection screens showing pre-recorded footage.
A separate model was created for the exterior of the derelict alien spacecraft. Matte paintings were used to fill in areas of the ship's interior as well as exterior shots of the planetoid's surface. The surface as seen from space during the landing sequence was created by painting a globe white, then mixing chemicals and dyes onto transparencies and projecting them onto it. The planetoid was not named in the film, but some drafts of the script gave it the name Acheron after the river which in Greek mythology is described as the "stream of woe", a branch of the river Styx, and which forms the border of Hell in Dante's Inferno. The 1986 sequel Aliens named the planetoid as "LV-426", and both names have been used for it in subsequent expanded universe media such as comic books and video games.
The scene of Kane inspecting the egg was shot during post-production. A fiberglass egg was used so that actor John Hurt could shine his light on it and see movement inside, which was provided by Ridley Scott fluttering his hands inside the egg while wearing rubber gloves. The top of the egg opened via hydraulics, and the innards were made of a cow's stomach and tripe. Initial test shots of the eggs were filmed using hen's eggs, and this footage was used in early teaser trailers. For this reason a hen's egg was used as the primary image for the film's advertising poster, and became a lasting image for the series as a whole rather than the Alien egg that actually appears in the film.
The "facehugger" and its proboscis, which was made of a sheep's intestine, were shot out of the egg using high-pressure air hoses. The shot was acted out and filmed in reverse, then reversed and slowed down in editing to prolong the effect and show more detail. The facehugger itself was the first creature that Giger designed for the film, going through several versions in different sizes before deciding on a small creature with humanlike fingers and a long tail. Dan O'Bannon drew his own version based on Giger's design, with help from Ron Cobb, which became the final version. Cobb came up with the idea that the creature could have a powerful acid for blood, a characteristic that would carry over to the adult Alien and would make it impossible for the crew to kill it by conventional means such as guns or explosives, since the acid would burn through the ship's hull. For the scene in which the dead facehugger is examined, Scott used pieces of fish and shellfish to create its viscera.
The design of the "chestburster" was inspired by Francis Bacon's 1944 painting Three Studies for Figures at the Base of a Crucifixion. Giger's original design resembled a plucked chicken, which was redesigned and refined into the final version seen onscreen. Screenwriter Dan O'Bannon credits his experiences with Crohn's disease for inspiring the chest-busting scene.
For the filming of the chestburster scene the cast members knew that the creature would be bursting out of Hurt, and had seen the chestburster puppet, but they had not been told that fake blood would also be bursting out in every direction from high-pressure pumps and squibs. The scene was shot in one take using an artificial torso filled with blood and viscera, with Hurt's head and arms coming up from underneath the table. The chestburster was shoved up through the torso by a puppeteer who held it on a stick. When the creature burst through the chest a stream of blood shot directly at Veronica Cartwright, shocking her enough that she fell over and went into hysterics. According to Tom Skerritt: "What you saw on camera was the real response. She had no idea what the hell happened. All of a sudden this thing just came up." The creature then runs off-camera, an effect accomplished by cutting a slit in the table for the puppeteer's stick to go through and passing an air hose through the puppet's tail to make it whip about.
The real-life surprise of the actors gave the scene an intense sense of realism and made it one of the film's most memorable moments. During preview screenings the crew noticed that some viewers would move towards the back of the theater so as not to be too close to the screen during the sequence. In subsequent years the chestburster scene has often been voted as one of the most memorable moments in film. In 2007, the British film magazine Empire named it as the greatest 18-rated moment in film as part of its "18th birthday" issue, ranking it above the decapitation scene in The Omen (1976) and the transformation sequence in An American Werewolf in London (1981).
For the scene in which Ash is revealed to be an android and has his head knocked off, a puppet was created of the character's torso and upper body which was operated from underneath by a small puppeteer. During a preview screening of the film this scene caused a female usher to faint. In the following scene Ash's head is placed on a table and re-activated; for portions of this scene an animatronic head was made using a face cast of actor Ian Holm. However, the latex of the head shrank while curing and the result was not entirely convincing. For the bulk of the scene Holm knelt under the table with his head coming up through a hole and milk, caviar, pasta, and glass marbles were used to show the android's inner workings and fluids.
Giger made several conceptual paintings of the adult Alien before crafting the final version. He sculpted the creature's body using plasticine, incorporating pieces such as vertebrae from snakes and cooling tubes from a Rolls-Royce. The creature's head was manufactured separately by Carlo Rambaldi, who had worked on the aliens in Close Encounters of the Third Kind. Rambaldi followed Giger's designs closely, making some modifications in order to incorporate the moving parts which would animate the jaw and inner mouth. A system of hinges and cables was used to operate the creature's rigid tongue, which protruded from the main mouth and had a second mouth at the tip of it with its own set of movable teeth. The final head had about nine hundred moving parts and points of articulation. Part of a human skull was used as the "face", and was hidden under the smooth, translucent cover of the head. Rambaldi's original Alien jaw is now on display in the Smithsonian Institution, while in April 2007 the original Alien suit was sold at auction. Copious amounts of K-Y Jelly were used to simulate saliva and to give the Alien an overall slimy appearance. The creature's vocalizations were provided by Percy Edwards, a voice artist famous for providing bird sounds for British television throughout the 1960s and 1970s as well as the whale sounds for Orca: Killer Whale (1977).
For most of the film's scenes the Alien was portrayed by Bolaji Badejo. A latex costume was specifically made to fit Badejo's 6-foot-10-inch (208 cm) slender frame, made by taking a full-body plaster cast of him. Scott later commented that "It's a man in a suit, but then it would be, wouldn't it? It takes on elements of the host – in this case, a man." Badejo attended t'ai chi and mime classes in order to create convincing movements for the Alien. For some scenes, such as when the Alien lowers itself from the ceiling to kill Brett, the creature was portrayed by stuntmen Eddie Powell and Roy Scammell; in that scene a costumed Powell was suspended on wires and then lowered in an unfurling motion.
"I've never liked horror films before, because in the end it's always been a man in a rubber suit. Well, there's one way to deal with that. The most important thing in a film of this type is not what you see, but the effect of what you think you saw."—Ridley Scott
Scott chose not to show the Alien in full through most of the film, showing only pieces of it while keeping most of its body in shadow in order to heighten the sense of terror and suspense. The audience could thus project their own fears into imagining what the rest of the creature might look like: "Every movement is going to be very slow, very graceful, and the Alien will alter shape so you never really know exactly what he looks like." The Alien has been referred to as "one of the most iconic movie monsters in film history" in the decades since the film's release, being noted for its biomechanical appearance and sexual overtones. Roger Ebert has remarked that "Alien uses a tricky device to keep the alien fresh throughout the movie: It evolves the nature and appearance of the creature, so we never know quite what it looks like or what it can do...The first time we get a good look at the alien, as it bursts from the chest of poor Kane (John Hurt). It is unmistakably phallic in shape, and the critic Tim Dirks mentions its 'open, dripping vaginal mouth.'"