Just before NASA’s Mariner 4 spacecraft passed Mars in July 1965, a worried Kubrick attempted to take out an insurance policy with Lloyd’s of London—in case the discovery of extraterrestrial life ruined the plot he was then working on with science-fiction writer Arthur C. Clarke. “How the underwriters managed to compute the premium, I can’t imagine,” Clarke wrote wonderingly, “but the figure they quoted was slightly astronomical and the project was dropped. Stanley decided to take his chances with the universe.” In the end, Mariner’s pictures showed a harsh, cratered, moon-like surface, which immediately tamped down the hope that intelligent life—or indeed, any life—might exist on that planet.

Early in pre-production Kubrick proposed to Clarke that they co-write a novel first, then base their film script on it—rather than the other way around. In fact, the director had promised Clarke that their novel could be published before the film came out. But as Kubrick became increasingly subsumed in the film, he reneged on that pledge—in part because various plot points weren’t worked out until fairly late in the production, and in part because he simply didn’t want their story to be known before the film’s release. This caused considerable tension between 2001’s authors, because Clarke needed the money, and his payment was repeatedly delayed as sale of the novel was deferred.

During production, Kubrick at first refused to let spacewalking stuntman Bill Weston wear a second cable for safety, although he was 30 feet above a hard concrete studio floor. This almost resulted in a serious accident when individual strands of Weston’s sole cable broke under his weight. In another incident, Kubrick refused to let Weston punch holes in the back of his space helmet, which meant the stuntman was perpetually on the verge of blacking out from carbon-dioxide poisoning as he engaged in complicated maneuvers while hanging high above the camera. When he actually did pass out, Weston, who’d been a mercenary in South Africa, took a minute to recover and then set off to find the director and teach him a lesson—a story originating from Weston himself. But Kubrick had fled the scene, causing production to grind to a halt for several days.

Some of the film’s most iconic features were decided during production for purely practical reasons. The mysterious black monolith began as a translucent Plexiglas tetrahedron, which ultimately assumed a monolith shape because Plexiglas cools better that way. But after paying massively for the big clear Plexi slab, Kubrick decided it didn’t look right—so production designer Tony Masters suggested the featureless black one, which Kubrick approved. In another example, the idea that the HAL-9000 supercomputer would discover the astronauts’ plot against him by reading their lips originated as an offhand suggestion by the film’s associate producer, Victor Lyndon. And the decision for HAL to kill off most of the crew came from visual-effects supervisor Doug Trumbull, who suggested that this would resolve some loose plot points—an idea the director at first angrily rejected. Kubrick later came up with the aphorism, “Never let your ego get in the way of a good idea.”

Arthur C. Clarke, worried that Kubrick might reject further collaboration with him because he was gay, one day mustered the nerve to confront the issue head on. Choosing his moment, he abruptly announced during one of their meetings, “Stan, I want you to know that I’m a very well-adjusted homosexual.” “Yeah I know,” Kubrick responded without missing a beat, and continued discussing the topic at hand. This brought a relieved smile to Clarke’s face. When he described the scene later to his wife Christiane, Kubrick said that Clarke had sounded “like a school teacher. He was very pleased that I don’t care, and he doesn’t know how much I don’t care.”

The film’s complex, kinetic sets were unintentionally hazardous. The film’s turning centrifuge, which was 38 feet in diameter, 10 feet wide, and weighed 30 tons, caused particular problems. Film lights don’t like to go upside down, and when they turned within the centrifuge, they frequently exploded, showering hot glass down on the film crew, which had to wear hard hats at all times. On one occasion Massachusetts Institute of Technology artificial-intelligence pioneer Marvin Minsky visited the set, and Kubrick ordered that the centrifuge be turned so the computer scientist could see it in action. Minsky narrowly avoided being hit by a falling pipe wrench, which would certainly have killed him had it hit him.

Stanley Kubrick and lead actors Keir Dullea and Gary Lockwood were all afraid of flying, with each traveling to England by boat for filming. That meant that the most convincing film about space exploration ever made would be captained and crewed by groundlings. As his trust in Kubrick’s vision grew, however, Dullea, who played astronaut Dave Bowman, overcame his fear of heights and agreed to do some of his own stunts, including plunging 24 feet on a wire within the film’s Emergency Airlock set. Both Dullea and Lockwood also flew from New York to Los Angeles in 1968 for the film’s L.A. premiere, at Kubrick’s urging.

American mime Dan Richter, who both brought to life the lead man-ape “Moonwatcher” and choreographed the whole “Dawn of Man” prehistoric prelude, was a hard-core heroin addict throughout production—a fact he initially hid from Kubrick. Richter, who had beat out numerous professional actors for the role, had managed to achieve the status of a “legal” addict in England, where the film was shot, and injected a doctor-prescribed speedball combination of pharmaceutical-grade heroin and cocaine up to seven times each day. When that blend didn’t do the trick and he needed additional stimulation, he always kept some state-supplied methamphetamine (crystal meth) on hand. After being inaccurately accused of pushing drugs by a disgruntled former collaborator, Richter confessed to his legal addict status to an intrigued Kubrick—who immediately asked him to describe what it was like and how he did it.

Sent to South West Africa—today’s Namibia—to scout locations and supervise large-format photography of desert landscapes for the “Dawn of Man” sequence, Kubrick’s assistant Andrew Birkin sent Polaroid shots back to London of a fascinatingly primitive-looking giant spiny aloe tree, or kokerboom in Afrikaans. Seeing the shots, Kubrick grew excited, and asked Birkin to cut down and transport the highly protected trees far to the north of their natural environment. Commandeering a small convoy of trucks and workers, Birkin fulfilled Kubrick’s wishes, illegally cutting down dozens of kokerbooms as night fell, then transporting them at great cost across the desert so they could be positioned where Kubrick wanted them. In the end, they were too small in the resulting background stills used for the “Dawn of Man,” and Kubrick had the film studio-art department fabricate fake kokerboom trees for him back in England.

No shooting day was more fraught with anxiety than the leopard-attack scene for the “Dawn of Man” sequence, which was set in a dry riverbed and filmed in the studio in London in September 1967. The leopard had been wrestling with animal trainer Terry Duggan for many months, but it didn’t know Dan Richter, who’d agreed to be in the scene. When it first jumped off its high hill onto Duggan, who was wearing a man-ape suit, it soon noticed Richter, also in his suit, and went after him. Luckily Duggan tackled the leopard just in time. Throughout the day, the film crew was unprotected—but Kubrick directed from within a protective one-man cage. “Everybody was very nervous because they figured Stanley’s in a f—ing cage; he doesn’t have a problem,” Richter recalled years later.

Reactions to the premieres of 2001 in Washington, D.C. and New York City in the first week of April 1968 were so negative that Clarke left the New York premiere in tears at the intermission. Some 241 audience walkouts were recorded at the New York screening alone, and the city’s leading film critics almost unanimously issued scathingly negative reviews. It seemed clear to everyone that the film was a monumental disaster—but young people flocked to see the film from the first day, and its fortunes quickly reversed. 2001 ended up becoming the highest-grossing film of 1968—the only time Stanley Kubrick ever achieved such a standing.

Despite its commercial success and undoubted influence, 2001 did not crack the British Film Institute’s critic’s list of the top 10 greatest films of all time until 1992. By 2002 it ranked as the 6th most important film in history—a position it retained in the last such survey, in 2012. It took 44 years from premiere for the film to even make an appearance on BFI’s Director’s Top 10 Poll. When it did, however, it landed with a bang, vaulting to second place, behind Ozu Yasujiro’s Tokyo Story, the current #1, and Citizen Kane (#3), which had long reigned at the top.

**Michael Benson is an artist, writer and filmmaker. A fellow of the NY Institute of the Humanities and a past visiting scholar at the MIT Media Lab’s Center for Bits and Atoms, he is the author of Space Odyssey: Stanley Kubrick, Arthur C. Clarke, and the Making of a Masterpiece and such books as Cosmigraphics: Picturing Space Through Time.**