Cantwell was one of the first people George Lucas brought on board to work on what was then called "The Star Wars." He was introduced to Lucas by Hal Barwood, who was working on American Graffiti. Cantwell invited Lucas over to his house and showed him his Steampunk-like "Superiority Machines," which led Lucas to believe he was right for the project. Lucas had also admired Cantwell's work on 2001: A Space Odyssey.
Lucas gave him a copy of "Adventures of the Starkiller, Episode I: The Star Wars," and Cantwell set to work on the project. Lucas tasked Cantwell with designing several vehicles and ships including the X-Wing, Y-Wing, TIE/LN Fighter, Stardestroyer, Imperial Cruiser, Death Star, Landspeeder, Sandcrawler, Millennium Falcon, and T-16 Skyhopper. Cantwell started by sketching several drawings, based on brief conversations with George. He then took those designs and penciled concept art, which would be shown to studio executives along side Ralph McQuarrie's art. Cantwell created these colored-pencil works to lift George's spirit and enthusiasm for the project after being rejected by several studios.
He also created several prototype models, based on his sketches, using a process called "kitbashing." This involved taking pieces from several model kits to add detail to a new model. When creating his models and art, Cantwell knew that he had to design ships so that the audience could tell the difference between the ships of the good guys and bad guys. He also came up with the names of X-Wing and Y-Wing.
When designing the X-Wing, Cantwell took inspiration from two sources: a throwing dart and a dragster. He invented the S-foils to look like a cowboy drawing his guns. The X-Wing, like other Rebel spacecraft, originally had wheels on its landing gear. This was because George Lucas had envisioned hiring the Spanish Air Force, redressing their F-104 fighter jets as Rebel fighters, and filming them taxiing and taking off a runway. This idea was scrapped because it was deemed too expensive, and Cantwell replaced the wheels with landing pads.
In his concept art, the engine thrusters had a diamond shape, but were changed to circular when the model was made. Also in his concept art, the fighter seated two people instead of one.
For the Y-Wing, there where two designs made. One design became the current Y-Wing, and the other was a more triangular design that became the Skyhopper. For the final design of the Y-wing, everything was pretty much the same as Cantwell's original model. The only real changes were with the cockpit, which was redesigned by fellow model maker Joe Johnston.
The Skyhopper was initially going to be the vehicle that Luke Skywalker and C-3PO used to find R2-D2, but was scrapped for budget reasons. The ship did make an appearance as both a background prop and a toy model that Luke plays with. It also made an appearance in the Special Edition of Return of the Jedi. Its design formed the basis for the Imperial Shuttles.
Cantwell designed the TIEs so that the audience could instantly recognize the design, and easily tell the difference between the good guys and the bad guys. Lucas gave him a direction that the ship would have solar cells and that would power their ion engines. When the design was finalized, Cantwell realized he forgot to put a way for the pilot to enter the craft. He then made the suggestion that they be hung from the ceiling, and entered that way.
Before working on the Death Star, Cantwell asked Lucas if the station was going to be near planets. When Lucas confirmed that it was, Cantwell decided to make the entire station silver. This way it could be easily seen at any angle in space. Cantwell hand-etched and inscribed all the details of the station so that it showed when light was cast on it.
When building the Death Star prototype, the material that was used to make the model, polystyrene, had a tendency to shrink around the edge of the casting, causing a slight dip. To work around this, Cantwell came up with the idea that the station should have a trench at the equator, between the the north and south hemispheres.
To convince Lucas, Cantwell suggested that the exhaust port be placed inside this trench, and have the Rebels fly along inside it. Lucas liked this idea and gave him the go-ahead. Doing this saved Cantwell a lot of work.
Stardestroyer & Imperial Cruiser
In the early drafts of Star Wars, Stardestroyers (spelled as one word) and Imperial Cruisers were two different spacecraft. A Stardestroyer was a triangular, two-man fighter. Imperial Cruisers were large, aircraft carrier-like ships. Stardestroyers were launched from the Cruisers. Cantwell produced concept art for both ships.
In later drafts, the two ships were merged into one. When the model was made, Cantwell made a hybrid of his two previous designs, creating the now iconic look of the Imperial Star Destroyer.
Before it was called the Millennium Falcon, the ship was referenced by the production crew as a "Pirate Ship." In the story it was a captured pirate ship that the heroes steal from the Imperials and escape to Yavin. In space, they get into a brief scuffle with Imperial fighters, and fend off several of them in the ship's turrets, before leaving in the escape pods. Cantwell kept this in mind when creating the concept model.
Until the actual production, Cantwell's design was going to be the Millennium Falcon. Joe Johnston even built a model for filming. However, George Lucas decided not to use the design after seeing a similar ship in the series Space: 1999. Lucas then opted for the now familiar "Eaten Hamburger" design.
References to Cantwell's design, regarding several jettisoned escape pods, did make it into the final script, however. Cantwell's design for the Falcon's cockpit was also retained for the new design. Johnston's model was later repurposed as the Tantive IV.
Landspeeder & Sandcrawler
Cantwell's design for the Landspeeder was primarily made to dissuade Lucas from plagiarizing a design from a Buck Rogers comic strip. It was made to get Lucas looking for other designs, and was not taken seriously by Cantwell as an actual vehicle submission.
The Sandcrawler was another design that Cantwell was not enthusiastic about. It was designed so that it looked like a monster that devoured the two droids while in the desert.
After Star Wars
When Lucas was rejected by Universal Studios, he talked to Cantwell about developing his own special-effects studio. He offered him a head position at Industrial Light & Magic. Cantwell declined, stating he did not want to be tied down, doing the exact same thing over and over again. He also cited Lucas's decision to sign on with 20th Century Fox, a competitor of Universal, a studio Cantwell had loyalties to.
- Star Wars: Episode IV A New Hope (additional spacecraft design)
- The Star Wars Sketchbook
- "Star FX: Model Universe" – Star Wars Galaxy Magazine 6
- Star Wars: The Complete Vader
- Star Wars: Build Your Own X-Wing 1 (Creating a Starship Fleet: Ralph McQuarrie – The Man Who Drew Star Wars)
- Star Wars Bust Collection 1 (Behind the Cameras: How the Death Star Was Created)