Rocketship - Maybe. Traditional- Maybe not. Traditional rocketships are long and skinny. The Eymorg craft is conical(spherical) with outboard engines, but squat.
@Henoch Memory Alpha has the side view of the very rocket-like original: https://memory-alpha.fandom.com/wiki/File:Eymorg_starship.jpg
The link doesn't work, but I looked it up on Memory Alpha. Good catch; I never saw the side profile of the original ship. Scale size? ~100 ft length or longer?
Link works for me but here you go: This shot is very short and appears before the initial view of the Enterprise and is often stepped on by commercials.
Hypothetical real space station designs are big cylinders just because the idea is to spin it to mage gravity. For the Trek ships, I’d buy that it’s some sort of engineering optimization. Or maybe there’s even aerodynamic concerns for safely flying through atmosphere. Or maybe they think a frisbee is a good shape to try to crash at a near flat angle.
Frisbees are only aerodynamically stable when spinning. With no spin, they are unstable. Saucer is another shape with a bulge in the underside center. Assuming no propulsion or shield power, the Enterprise saucer would enter the atmosphere like our current space capsules. The bottom of the ship would act as its heat shield while protecting the upper side from the reentry heat. The concave under-side feature might help to aerodynamically slow its decent with chemical-reaction rockets to stabilize the free-fall. At a certain altitude, old-fashion gigantic parachutes would be deployed for final landing. "Crew. Assume crash landing positions." (I'd put my mattress on the deck and lay flat on it.) The bottom decks may act as a crush zone, so, all crew would be evacuated to the upper decks.
IMHO all interstellar FTL ships and many ships that travel at even sublight speeds are likely to be tall, narrow cylinders because of their speeds in space. At earth's distance from the Sun, the escape velocity of the Solar System is 42.1 kilometers per second. If an interstellar craft is launched from orbit around the Sun at Earth's distance at a speed of 84.2 kilometers per second it's speed will gradually decrease until it is just a tiny little bit more than 42.1 kilometers per second. At that speed the craft will travel 1,328,574,960 kilometers in 31,557,600 seconds or one year. And it should take the craft about 4,426.2 years to travel even one light year. If a space craft travels much faster, say one percent of the speed of light, it will take it one hundred years to travel one light year. One percent of the speed of light would be 2,997.9245 kilometers per second. Ten percent of the speed of light, or 29,979.245 kilometers per second, would be necessary to travel one light year in only ten years. The kinetic energy of an impact depends on the mass of the object hit and the velocity. And speeds of one percent to ten percent of light speed are already thousands of times faster than any speeds in the solar system. Any slower than light space craft that travels at a significant percentage of the speed of light is going to suffer greatly from impacts with grains of dust or even molecules of gas in the interplanetary or interstellar environment. Even though interplanetary space is a thinner vacuum than science can create on Earth, and interstellar space is much thinner, there is still matter in space that can be collided with. Subatomic particles, gas molecules, specks of dust, and even tiny pebbles are in interstellar space and even more so in interplanetary space. If the path of a starship from star to stars is imagined as a narrow cylinder of space with the width of the starship, the starship will impact every single subtomic particle or object in that cylinder of space and create an absolute vacuum in that cylinder of space until matter from outside the cylinder of space drifts inside it. The greater the diameter of the starship the greater the diameter of the cylinder of space where it will hit every single bit of matter. Changing the diameter of the starship will change the diameter and total volume of the cylinder of space where it will hit every single bit of matter in its journey. Since it is desirable to reduce the total number of impacts during an interstellar journey, and thus the total impact those impacts have on the starship, it is desirable to reduce the cross section of the starship perpendicular to its direction of movement. Thus the design of a starship most likely to survive a sublight interstellar journey would be a very tall, narrow cylinder with many round decks perpendicular to the height and the direction of movement. The arrangement of decks in the habitable parts of the starship would resemble the arrangement of floors in a round skyscraper. Of course a starship that actually travels through space much faster than light is likely to have much more violent impacts with any matter it impacts. The warp drive supposedly doesn't work by moving the starship through space faster than light. instead the starship supposedly remains still in the center of a warp bubble of space/time that is moved relative to other space/time. But if the warp bubble dosn't have an absolutely sharp border between space that is 100 percent affect and space that is 100 percent not affect, if the effects of the warp bubble become weaker and weaker with distance, the starship is likely to pass among particles of matter that have varying degrees of warp effect on them. And it is possible that matter particles within the regions affect to various degrees will interact with each other with gravitational and magnetic forces. So there could be interactions between the starship and other particles totally within the warp field, particles partially affected by the warp field, and particles totally outside the warp field. And such interactions could cause a drag effect on the starship. In which case making the warp field as narrow as possible would reduce the drag effect, and that may require making the starship as narrow as possible.
I don't think there'd be a "drag effect" on something that's a topological distortion of spacetime itself. And I think Alcubierre-style warp equations suggest (going from memory here) that particles impinging on the warp bubble would just sort of get stuck along the forward edge like bugs on the windshield -- and then, when the ship comes out of warp, they'd be blasted forward at high relativistic velocities as deadly cosmic rays, so you don't want to cut warp while pointed toward anything you like. Since we are talking about a bubble here, you'd probably want a spheroidal ship, so the bubble would be as compact and energy-efficient as possible.
A starship could have many warp field generations each generating a spherical warp bubble, and the generators would be close enough that their fields would combine to form a field of uniform strength around the starship and presumably diminishing strength farther away. So the shape of the starship and the placement of the warp generators could define the shape of the warp bubble around the starship.. Since you mentioned the way that a Alcubierre style warp bubble would pick up a deadly amount of stuff and then blast it forward when the warp bubble deactivates, it might be a good idea for a civilian starship to have as narrow a warp bubble as possible in order to minimize that effect so they could come out a of warp harmlessly as close to the destination as possible. And depending on how close the warp bubble was to the ship, the ship might have to be a narrow cylinder in order for the warp bubble to be a cylinder. on the other hand, a warship might desire a disc shaped warp bubble with the broad face of the bubble facing forward in order to maximize the effect and pick up as much destructive force as possible to release when turning off the warp drive at the target position in space. And that might require that the warship be shaped like a disc or saucer and travel with the broad face forward.
I've long thought that, intentionally or not, the original Enterprise design was a clever blending of the two predominant shapes used for spaceships in popular culture up to that point - the flying saucer and the rocketship. But by blending the two together the way he did, Matt Jefferies created a truly original, distinctive shape for Star Trek's main ship that achieved pop culture immortality. It was a paradigm shift, for sure.
I'd hate to think that all other space travelers in Trek are idiots who can't figure out the most efficient design... OTOH, considering that there is no single predominant design out there, I'd like to think that there are no engineering constraints overall, and space folks go for aesthetics or esoteric philosophies when choosing a shape. Which in turn might mean the saucer in-universe is chosen for the very same reasons it got chosen out-universe - because it looks pretty and sleek and distinctive and harkens back to certain quirks of Earth's history. OTTH, we have seen and heard of saucer separation, and always in the context of protecting the crew, one way or another. Might well be Starfleet is the only saucer user due to Starfleet being the only one to care enough about the crew. Again both in- and out-universe: the saucer gets carried on because the designers are aware of the pseudohistory of it being a lifeboat and want to emphasize that evil space scum doesn't even believe in lifeboats while our heroic heroes decidedly do. Timo Saloniemi
They just tried to put a different spin on it..........spin.........saucer........no......i'l get me coat.
I have always assumed that earlier ships used spheres for the living areas and the engineering hull for the messy stuff. Daedelus class as an example. But as crew sizes grew, the centre decks of the sphere spread outward and in time formed a saucer. Take away the widest parts of the original Enterprise saucer hull and what are you left with? A sorta sphere. Or not!
Klingon ships seem to imply a small crew module that can presumably seperate from the engineering deck. And the Defiant class has no easy seperation conceivable. So I hazard to guess that Starfleet isn't the first to conceive of a sort of large-scale escape pod.
Well, the Defiant was designed around Starfleet's first-ever ejectable bridge - that's what the bow section was supposed to be, before the ship was drastically upscaled. Although as for first-ever, some fan/backstage takes have assumed that the bridges or upper decks of Kirk's and Janeway's ships were also independently ejectable... Timo Saloniemi
Is it known why the sphere design was rejected, or was it simply not the right shape for the era when saucers were seen as the peak of space traveling?
In-universe? In the TNG era, a sphere-hulled design was portrayed as a hospital ship. Perhaps there has always been a demand for sphere hulls, but in "peaceful" applications like that, and the sphere-hulled Daedalus or whatever (we have never seen that class name actually associated with the sphere-hulled tabletop model!) was a "peaceful" ship from the mid-22nd century while the saucer vessels from that era were "warlike" or "exploratory". One would then be tempted to think that saucers go faster. But that's explicitly not true in the TNG era, where both the hospital ship and the modernized E-D travel at warp 13 when in relative hurry. "Peaceful" might instead have something to do with shielding, the saucers being easier to protect somehow. Or then it's the obvious thing: a saucer has a smaller silhouette in the standard encounter between two starships, which is nose-to-nose. A sphere presents a maximal silhouette to the enemy from all directions; a clever captain can minimize the silhouette of a saucer by maneuvering right, and it takes even less effort to minimize the silhouette of one of 'em Vulcan spindles. So spheres are preferred when the assumption is that nobody is firing at you much (and the other attributes of a sphere, such as possible ease of shielding or ease of construction or whatever, thus dominate), and saucers when you need to dodge death rays and hide from targeting systems. Out-universe? I gather the sphere looked sorta passive and sluggish, there being no bow and no "forward impetus" to the shape, so Jeffries was told to do something sleeker. He kept the attractive simplicity of the circle shape by using a saucer, even at the risk of drawing something looking like a trite old UFO, and Roddenberry approved. Of course, bits and pieces of the story actually survive - folks like Shaw or Harvey etc. here would have the dirt. But the full story probably wouldn't have been told, unless it was very specifically asked when Jeffries was interviewed. Headcanon? I go with the novels that say the sphere-hulled little Daedalus was a mass-produceable wartime desperation measure, akin to the small escorts the RN built out of whaler blueprints in WWII. Which means I think the sphere was simply easier to build than the saucer, while in fact being an inferior shape in combat (for the silhouette reason and others), and quickly disappeared from military use after the Romulan War concluded and desperation evaporated. Timo Saloniemi