In sci-fi’s a lot of the time, the ship is aerodynamic, even if it never needs to enter the atmosphere. I guess because it looks better to the viewer.
But in reality, what would be the best/most efficient shape for a spaceship that never needs to enter an atmosphere? Does it matter at all?
I suppose a thin ship would be better because it would hit less particles and whatever else is out there in space. For that matter, maybe an aerodynamic looking ship would be better, as whatever hits the spaceship can slide off easier.
But if that weren’t an issue, ships might as well be squares?
Regardless of what is most practical, do you think that humans would design actual spaceships to look aerodynamic just to make them look more physically appealing?
Quite possibly; rather like how for example symmetrical airplane designs are chosen over asymmetrical even if the asymmetrical one is superior. People aren’t motivated by pure efficiency.
One possibility that appears likely to me is building shells around the ships of extremely light, thin material to give it a more aerodynamic or just “cool” look with a minimum mass penalty.
What other considerations drive the ship geometry? If it has to stand on the surface of a body with gravity, then it has shape concerns like buildings do (note that this requirement could still exist if the ship never enters a significant atmosphere, for example on the Moon). If it harbors life and requires pressurization, then it prefers the same shapes that tanks for compressed air do. If there is a need to generate artificial gravity, then it probably needs a shape like a tethered dumbbell, or possibly a ring. If it needs to simultaneously maintain things that dislike each other, such as crew quarters and radioactive power, then it needs to be long.
Likely spaceships would be a lot more spindly than is generally depicted in sci-fi with a lot more surface area per unit volume. Functional spaceships have a lot of reactors that run hot and habitation modules that have to be kept cool, with both embedded in one of the most heat-insulating mediums in the universe, so a lot of surface area to shed excess heat from is important.
The mothership from Avatar is actually fairly well designed in this regard: Big engine dragging along tiny habitation module with long cable to keep all of the dangers of the engine far away from the people.
The Atomic Rockets site has a section on the pros and cons of sphere and cylinder shaped ships in their Advanced Spacecraft Design page: Linky
To see the index for the site put you cursor where it says *Show topic list * on the top right of the page. There are more pages dealing with space craft design and the various technologies and other space related stuff like aliens.
A spaceship or any ship for that matter is shaped based upon its mission. Look at the current space station. Not very aerodynamic but then again it never needs to be. The shuttle on the other hand is out of necessity. Aesthetics has little to do with it. As technology gets better, shape and design progresses to meet the needs of the mission. I suspect that if any one was to ask NASA or any other space agency of any country if esthetics is considered in design, they would say no.
Cylindrical and spherical are good for handling pressure, and cylindrical wins out over spherical in terms of easy manufacturability. As ships get larger, just using larger cylinders may not be optimal, since you’d either need higher surface tension, or internal struts, to hold in the pressure. But you could use multiple cylinders, like the space station does. For a ship, they’d probably all be parallel, in the direction of motion. That seems a sturdy structure, and depressurization in one module could be easily contained.
In our everyday engineering we value looks. I see no reason why this wouldn’t eventually apply to space craft. If we were building space ships today, provided it didn’t take away from utility I’d expect space ships to incorporate aerodynamic shapes. By the time we get to that level of choice however our society views of art may have changed. We might very well decide on cube shaped ships because that’s popular at the time
We build bridges and skyscrapers with esthetic value all the time. Pure utility is seldom the only deciding factor in even our most basic creations.
(That’s one page in the collection C-ship: Relativistic ray traced images, which helps you explore relativity by the simple expedient of showing you pictures and video of a ship that can accelerate to very nearly the speed of light in a vacuum, or c.)
Unless we know what technologies and materials are available, as well as the spaceships’ purpose, we have absolutely no way of knowing. We’re like Leif Ericsson trying to imagine an AEGIS cruiser.
The big issue is weight and the cabin pressure at say 14 psi, or a ton per square ft will require a lot of heavy metal to resist collapsing the flat portion of your cylinder.
Theoretically, their are no bending stress in the sphere which makes it vastly superior.
On the other hand I like the cylinder with spherical ends. I can’t see any bending stresses in there either, and probably more efficient for interior layout .
The larger a ship becomes, the more surface area will need to be dedicated to radiator surfaces.
A ship (or space station) will need to shed heat in proportion to the amount of energy being generated onboard. In a vacuum, the only ways to shed heat are with radiator panels, or by evaporation or sublimation of fluid. The latter is only used for short-term cooling as it consumes fluid, so any long-term ship or installation will need radiators.
Heat generated will scale roughly with ship volume, with exact details depending on design of course. Radiator surface on the other hand scales with surface area. As you increase the size of a ship surface are increases more slowly than volume, so the design will need to change to permit more radiator surface. It’s the old square-cubed law again.
We can see this to a degree with existing capsules and stations. The earliest capsules - Mercury and Vostock - barely needed cooling systems. Soyuz and Apollo have radiators built into the outer surface of the command module. The Space Shuttle has radiators on the inner surfaces of the cargo bay doors, which is why it always needs to have the cargo bay open while in space. And the International Space Station has multiple fairly large radiator panels unfolded accordion-style, some of which are on pivots to keep them edge-on to the sun.
Assuming the spacecraft or it’s materials have to be launched from a planet like earth which requires using a lot of fuel, a spherical ship will have the greatest volume for the weight of it’s materials, so that ship will cost less to get into space, weight wise. However, considering how many other cost factors would be involved, that one wouldn’t be all that important.
I would say that even a ship that never lands but that must endure significant acceleration must have structures designed to withstand that acceleration, which is similar to withstanding gravity. This means it needs at least some sort of orientation (“this side forward” instead of “this side up”). A spidery lattice like the International Space Station probably couldn’t endure high acceleration in any direction.
Weight (mass) distribution is a key factor. A balanced ship is easier to steer and move. You’ll need to figure out where the center of mass is going to be and design around that. It may not be geometrically symmetrical but it better have good mass distribution.
The design for the discovery one in 2001 was apparently well researched and based on real designs. Nuclear reactor at one end, living sphere at the other end of a long gantry. In the book version the gantry between was filled with radiator fins, in the film they got rid of that as they thought people wold think it was wings for atmospheric entry instead.