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I was watching Star Trek, and I thought that the shape of the Enterprise is quite weird. So what would a spaceship as big as the Enterprise look like? What would be the most efficient shape for a colossal spaceship that won't enter atmosphere?

We assume in this case the problem with gravity is somehow solved through alternative methods, so it won't necessarily need to have a tube shape to possess internal gravity like that of earth.

Notes:

1-the ship will be built in space and thus won't even once need to deal with leaving or entering a planet's atmosphere on normal conditions.

2-has to accommodate about 1000 passengers.

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    $\begingroup$ Are you asking about design constraints for space ships? Can you provide some additional information about what this space ship's mission is? $\endgroup$ – Green Jul 13 '15 at 13:58
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    $\begingroup$ I am afraid that any shape is justifiable by unknown laws of physics, including Enterprise's. In addition to the shapes suggested by the first two answers, also the cube is popular as for example easy to organise. Aesthetics may also decide about shape, if technical problems are unimportant. $\endgroup$ – BartekChom Jul 13 '15 at 14:13
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    $\begingroup$ I vote to re-open this question. I Don't think it is more opinion-based than a lot of questions on here. (Plus, i like the question :-) ) @ fishkopf: maybe you should provide some criteria to indicate how you will judge wether an answer is good or not. $\endgroup$ – Burki Jul 14 '15 at 7:23
  • $\begingroup$ I like the question too, my main concern is how constrained by science he wants it to be. Are we talking science plausible, science based, or hard science. The more strict we get on this spectrum (moving towards hard science) the less opinion based I think it will be. $\endgroup$ – Jim2B Jul 14 '15 at 12:54
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    $\begingroup$ this really depends on what you want the ship to do, the designs for a warship, mining ship, and landing craft are going to be radically different. $\endgroup$ – John Apr 11 at 14:59
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Baring constraints imposed by the spaceship parts the shape would be either a sphere or irregular.

The sphere is optimal in the sense that it has the least surface area compared to volume. It also doesn't have any "corners" which is an advantage when it comes to maintaining a pressure difference. So a ship designed from scratch and built in space would probably be a sphere. This somewhat with limitations imposed by the spaceship components, for example if your engine is radiating strongly you want some distance between it and the rest of the ship - which can as an example lead to a ship that is basically two spheres with long struts between them.

If your spaceship is constructed in orbit it's also possible that it's essentially built by adding parts to it as and when those parts become available. In this case the spaceship would add parts at the points that is convenient at the time those parts where added - leading to a somewhat haphazard shape overall. For example the international space station. There is a problem with this approach in that your thrust has to be aligned with the center of gravity, which would be difficult. Essentially I do not expect anyone to suggest strapping engines to the ISS to create a spaceship, but it's not entirely implausible - especially if you have artificial gravity.

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    $\begingroup$ The ISS has engines. $\endgroup$ – Joshua Jul 13 '15 at 16:10
  • $\begingroup$ @Joshua Yes, but it's not a spaceship. It's engines are there for stationkeeping, not to move it to a different orbit. $\endgroup$ – Taemyr Jul 13 '15 at 21:26
  • $\begingroup$ "a ship that is basically two spheres with long struts between them"... IOW, Discovery One. $\endgroup$ – Matthew Apr 11 at 18:41
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Necessity will shape space ships. We of course will start with big cylinders that rotate for gravity, I think that the center of the cans will be where the power-plant/propulsion system will be.

I think this might continue even if we figure out gravity fields to hold people to the deck. Partially out of inertia, we will have experience building ships that way and partly out a good design. the front of the ship can be designed to be a 'funnel' to help collect 'fuel' to feed into the engines, like a jet engine. This would have a two fold benefit. it would collect fuel and help protect the rest of the ship by 'guiding' harmful and dangerously fast matter away from the living quarters, forcefields would be used as the funnel.

If you mount the engines outside the body then you will have much smaller funnels guiding material and still need to protect the whole ship from collisions, maybe having to deflect the matter much farther to protect the whole ship.

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  • $\begingroup$ Incidentally, this is the "correct" answer in most better science fiction. Figure out how your propulsion system works, and that dictates the shape of the ship. This is how it worked for Star Trek, Honorverse, and probably many others. $\endgroup$ – Matthew Apr 11 at 18:44
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It Depends

The shape of a vehicle depends on a couple of things, the size and shape of the powerplant/engine, the purpose of the vehicle and the aesthetic requirements/tastes of the customer/manufacturer.

Powerplant

The shape of the Enterprise is driven by the practical shapes of it's powerplant. The two engine nacelles are needed to gather enough interstellar hydrogen as fuel. Still in the Star Trek universe, the Klingons and the Romulans have different powerplants so their ship designs differ significantly from the Federation's. In every spaceship I can think of, the powerplant/propulsion system takes up a significant portion of the ship.

Purpose of Vehicle

A cargo ship will have a drastically different shape than a pleasure cruiser. A cargo ship wants to maximize internal volume for cargo. A small pleasure cruiser will care more about economy and speed. Look at the variety of shapes of cars/trucks on Earth's roads. They have radically different shapes depending on their needs.

Aesthetic Requirments

The Romulans designed their ships around the shapes of birds. Maybe the customer really wants all chrome ships?

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The single most important factor in a spaceship's shape is the technology available.

So you could just make something pretty and then make your world's technology such that that's a good design, like star trek did.

One prediction that will hold true for almost all sets of technology is radial symmetry. Like a star fish or a tree, a skyscraper, or a sphere. We're used to things that move having bilateral symmetry (like people, cats, cars, planes, the Enterprise) because there are two relevant directions, where you are going and gravity. For your ships there is no external gravity.

Depending on how your artificial gravity works "down" will probably be the direction towards the rockets so that you can save power on artificial gravity while under propulsion, or down could be the direction you are going so that you can accelerate more than 1 g and make the passengers only experience 1 g. If saving energy and direction don't matter then down could be arbitrary.

Also aerodynamics don't matter so hard corners and fragile antenna hang out randomly would be acceptable, as would a long line of modular looking pieces like you see in 2001 space odyssey. The only physical limitations on shape are that vital systems and crew need to be safe from attack and debris, and everything needs to be able to withstand the acceleration of your engines.

One thing people don't think of that will be true for some technology sets is radiators. Your ship will make a lot of heat and there is no air to carry it away, so depending on your technology many ships may have long retractable glowing wings to radiate the heat away.

There's a lot of good points in other replies too but this is everything I know that hasn't already been said.

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As other have pointed out, it depends a lot on function.

For a warship: A Spherical Hex Lattice

enter image description here

Space combat in any realistic since is all about hitting your enemy before they can hit you. This means you want to minimize your hit profile to the absolute minimum so that all else being the same, you can reliably evade hits at longer ranges than you opponent and kite them until they are taken out.

Lattice ships allow you to evade a shot by letting it pass through your ship rather than having to move all the way out of the way such that small course corrections are all you need to dodge a shot. The spherical part is because it means you can take many hits without your ship losing any meaningful pieces and the reason for the hex shapes are because it breaks up straight lines meaning enemy ships can't reduce thier firing solutions to a single dimension of guesswork.

This answer to a similar question goes over this in more detail. https://worldbuilding.stackexchange.com/a/152967/57832

For a warship where system requirements dont allow a lattice: a Flat Ship

enter image description here

Flat ships have all of the same advantages as the spherical hex lattice, but to much lesser degree. Flat designs like flying saucers can by strafing up and down use smaller course corrections to dodge. They also allow for decent distribution of systems without having any attack vector that makes you easy to cut in half or overpenetrate right through all of your major systems at once.

It is actually funny that the Enterprise is referenced as such a bad shape since many federation ships would fall into this class of flat ships. The Enterprise NX-01, the Steam Runner class, the Akira class, and the Defiant class are all pretty decent designs for warships, especially in context of federation technical limitations for how Gene Roddenberry described federation warp drives to work.

For a Fast Ship: A Cigar

enter image description here

If your ships experience inertia while accelerating or friction from the albeit thin atmosphere in space, then it will be most important to optimize your hull against stress in the vector of your acceleration which is best done with a long narrow ship. These also minimize profile much like the previous 2 ships, but a single broadside hit is more likely to cut you in two or a single nose shot could overpenetrate you from bow to stern wrecking your whole ship; so, they are not quite as good of a military design.

For a Freighter: An Accessible Modular Cigar

enter image description here

Cigar for the same reasons as a fast ship, but optimising the time spent in port is also a huge aspect of logistics. Modern freight companies solve this problem with the use of cargo container ships. The factory loads the container, the container is placed on the ship in an easy to access manor, then the containers are unloaded ready to be put on trucks to go to thier destination. Saving a single second loading or unloading a ton of cargo can save days worth of port time on a larger freighter cutting into profit margins by a large %. The key here is that your cargo containers need to be highly accessible from the outside of your ship to minimize the time and effort of loading and unloading it.

For a Cheap Ship: A Solid Sphere

enter image description here

A solid sphere minimizes the amount of materials spent on making a structurally sound hull; so, you are just left paying for the thinner internal walls and necessary systems. This is the single worst design profile for a warship because it makes you easy to hit from all sides while offering many opportunities to hit vital systems with just about any projectile damage profile. That said, things like colony ships, mining ships, single use craft, etc might frequently use this design.

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As @BartekChom said you can have any shape. To elaborate, in space you can assume there's no friction so a cube would be as "aerodynamic" as a ship shaped like a rocket.

If your ship is a generation ship (will be travelling through space long enough that people will spend their entire lives on it) then you may want a ship which is a large sphere with different levels for the functions needed.

As well you need to consider how the ship will deal with threats, whether they be environmental or from other ships. Will it have a force field? Can the fields shape be manipulated?

The final consideration is fuel/propulsion. Does it use unobtanium to move, or will it need to collect the fuel as it goes. The engine is also important, does it require shielding, does it have a specific shape it needs like a solar sail?

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Given your setup, most importantly the part about not entering an atmosphere at any time, and that it is built in space, i think a construction that looks like the ISS with the enterprises engine gondolas attached, is a very likely result.

The basic setup of the ISS, with everything built in (more or less independent) modules arranged around each other provides ease of build, since you can dock individual modules tio the cluster pretty much wherever it is convenient, and in case of a hull breach you only loose a single module (until it is repaired or replaced).

The enterprise-style engine gondolas seem likely to me because i assume that they might either be radioactive, or very hot, or have strong EM fields, and might have a risk of fires, explosions or similar, so that you might like the possibility of getting rid of them easily when necessary.

So, overall, you will get a fairly ugly cluster pushed by an arbitrary number of very, very large engines.

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Cube or rectangular

The shape will depend on a lot of factors, so I will make some assumptions.

  1. I am assuming you have artificial gravity, so no need for long rotating cylinders or donut shapes.
  2. I am assuming that the shape has no influence in space due to speed or ftl travel.
  3. Since it is built in space I assume some standard manufacturing. This is quite important since one-offs space ships can be completely different.

The most efficient way of constructing large objects is quite often modular. You can have a lot of factories creating modular modules which will be coupled together to create a spaceship. Modules will probably be rectangular in certain sizes for easy assembly. Basically you would stack them like cargo containers. They would also be rectangular since flat surfaces that you can screw together are much easier to make than rounded surfaces. That goes for the outside, but also for all machinery on the inside. In the real world, things are usually rounded only for function or aesthetics. In the case of aesthetics most machines on the inside are quite square.

If for some reason you would need a sphere shape, for less outer area compared to volume you would probably only make the outer shape spherical, much like rounded office buildings.

As a last remark, for slower than light colonial ships I believe hollowing out asteroids (or clomping them together depending on the wanted size) and covering them in a thick sheet of ice as protection for interstellar radiation would be most efficient.

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