(written from a Production point of view)
Donald "Don" Loos was a model builder who worked on Star Trek: Phase II television project. Under the supervision of Brick Price, Loos was the lead model maker on the build of the Enterprise Phase II studio model while in employ of Brick Price Movie Miniatures, a company sub-contracted by Magicam. This work, done at Loos' own workshop in Van Nuys, was based on the design sketches provided by Matt Jefferies for the project. Loos' Enterprise studio model was three quarters complete, and he "(...)had the engine pods finished, and was working on the struts(...)" as Jefferies recalled (Star Trek: The Magazine Volume 2, Issue 8, p. 84), adding that Loos and Price "did a beautiful job", but was pulled from the project in early December 1977 when a new, larger model was deemed necessary to meet movie requirements when Phase II became Star Trek: The Motion Picture. (Return to Tomorrow - The Filming of Star Trek: The Motion Picture, p. 27; Star Trek Phase II: The Lost Series, pp. 27, 72)
Model Shop Supervisor Jim Dow of Magicam, to which the build of the new Enterprise model reverted, considered Loos' work somewhat sub-par, "Don Loos is a very fine model maker, but his techniques were a bit antiquated and his model was made for television." (Starlog, issue 27, p. 27) This however, solicited a somewhat irked response from Loos' employer, Brick Price, who felt that his employee was being short-changed by Dow, "Loos is doing a lot of work with us now on various models for NASA and I have the greatest respect for his ability. He does not use "antiquated" techniques as Dow says unless it is for the best." (Starlog, issue 30, p. 8) However, Dow's off-the-cuff remark for Starlog magazine was not meant as nearly as derogative as Price made it out to be as he had already explained in an, at the time, unpublished interview where he delved in far more detail into the production reasons for having stated so,
"Bob Abel took a look at the rest of the models we'd been working on–the Klingons, V'ger and the space office complex– and at the Enterprise, which Don Loos had been working on. It was decided to shelve all of the models, because they were definitively built for television, and to bring the Enterprise into our shop. This was because Don Loos unfortunately wasn't equipped, as we were, to build a model for motion-control shooting, which requires many things designed into the model in the way of stability and inter-changeability and interfacing to the computer-controlled rig. He was still doing things in fiberglass and wood and other materials that we don't use because they're much too heavy. Our basic armatures have to be designed in a very solid way in aluminum, and our body skins are designed to cope with a variety of things, thermal changes and so on, so that they don't flex or expand. Also, Bob Abel wanted to work with models that were scaled for one inch equaling 10 feet, and Don's Enterprise was a little under that. And he wasn't constructing models the way they necessarily have to be constructed for the motion-control camera. Models today are a great deal more exotic than they used to be.
"For instance, the Enterprise, being a cantilevered object very spindly in nature, must not flex between camera passes. The propulsion pods are suspended on struts away from the main body, and the primary consideration is: from how many points do you armature the model for shooting? And once we'd decided on five for the Enterprise, how do you power the lighting systems from each of those five armaturing positions? How do you keep the model from flexing, or dropping the nose of the saucer, when you turn it on its side? Which lighting systems do you select, based on the kinds of exposures with which you're going to be able to afford to photograph the model? And how many times do you have to expose the model in repeat passes of motion-control photography in order to build up the single image of the model? And so on and so forth. There really are a great deal of things that mist be considered in the basic model design that are never even thought of by people who aren't familiar with motion-control shooting. Well, we were familiar with it, and Bob Abel was planning to build a motion-control camera, so we began the design/construction phase of the models for the Robert Abel version." (Return to Tomorrow - The Filming of Star Trek: The Motion Picture, pp. 62-63)
For almost two decades, Don Loos had, unwittingly, been the subject of one of the most persistent myths in Star Trek lore for being attributed the build of the Star Trek: The Original Series' original eleven-foot Enterprise studio model. The misconception originated from an off-hand remark Jim Dow had made in the interview for the above-referenced 1979 Starlog magazine issue, specifically mentioning Loos as the one "who made the original one for TV" (p. 27) Unthinkingly, Dow's remark, misinterpreted as being the Original Series one, was propagated by authors ever since for the next two decades in every subsequent reference work, such as Cinefantastique magazine (Vol 17 #2, 1987), Starlog magazine itself, The Special Effects of Trek (1993), and even officially licensed books like The Art of Star Trek (1995). Even as late as 2020, the mistake was reiterated once by the authors of their otherwise meticulous reference book Star Trek: The Motion Picture - The Art and Visual Effects (p. 28, but not repeated elsewhere in the book). However, what each and every single author of these works had failed to grasp was that Dow was not referring to the Original Series, but to the abandoned Phase II television project. Only in 1996 was the mistake rectified by author Daniel Fiebiger in an article for Cinefantastique (Vol 27 #11), identifying the real builders of the Original Series filming models.
While still in the employ of Price, Don Loos, has only one other recorded motion picture "model construction" credit to his name, for the movie Lifepod (1981). The reason for this was quite simple as Loos had been a technician at NASA in daily life, building models for wind tunnel tests, relating that he had received a lot of "strange looks" from his colleagues when they became aware of his side project. (The Special Effects of Trek, p. 14) As indicated by Price, Loos reciprocally brought in Price's company to work for NASA, when he returned to work for his regular employer.