Spaceship Design: What makes sense, and what's nonsense?

[ericthered]

Bilateral symmetry makes sense for a certain kind of warship: one in which you are typically accelerating orthogonality to the direction of the enemy... or in other words, where dodging is more important than closing the distance. You have a powerful engine that moves you "up", but you fire "forward". To change the direction you dodge the ship rolls left or right. To minimize the profile and make your spinning more efficient you end up with a long thin rod with the main engine mounted at the midpoint of the rod... at least as far as weight goes.



The job of the ship and the surrounding technology will determine a lot about the ship. Some things to watch for:

• Does it enter the atmosphere? If so, you want it streamlined, and long and thin also helps.
• Does it move at high relative speeds through space? it might need shielding, and the most efficient way to shield is to make a long skinny ship with heavy shielding at the front.
• Does it experience high acceleration, and does it experience it from more than one direction? Many "realistic" designs have large solar or magnetic sails towing a body at a slow speed, and are loosely put together, while a ship that is made to take serious thrust in one direction tends to be shaped like a rocket.
• What's providing power, and how do you shield it? some spacial and material separation between the humans and the reactor is often a good idea.

some idea of what your spaceship paradigm is would help here as well.

[RyanW]

Originally Posted by WingedKagouti

It's worth noting that most Star Wars spaceships are (in-universe) intended to operate in many types of atmosphere as well as in (hyper)space. Of course, the actual designs are influenced far more by "will it look cool on screen" and "will the toy sell" than any actual workable real world engineering considerations.

And (especially early on) "can we build it using readily available model kits?" The main ships use off-the-shelf model kits for most of their detail parts. There are background ships that are not much more than an airplane model with the wings cut off and bits slapped on to make the outline less recognizable.

[Pomphis]

Originally Posted by FF_Ninja

My plan is to design an entire hierarchy of new ships for futuristic Earth, starting from the earliest space-fairing vessels, gradually incorporating FTL into the design (haven't settled on what FTL actually looks like in this setting), and building on that form factor over time.

As others have said, almost everything depends on the technology.

Do you have artificial gravity? Do you use spin gravity?

Do you have reactionless drives?

Are the FTL drives huge or small? Do they need huge amounts of fuel, as in Traveller?

Do you have force fields? If yes, can they have any shape or only some?

With enough superscience I prefer globe and egg shaped ships - simple, structurally sound, good surface/volume ratio.

[Varyon]

An interesting consideration when it comes to gravity is for spacecraft that are meant to operate planetside as well as in space. Planetside, a layout like a modern airplane (long and short) makes sense, whereas in space, a layout like a tall tower (tall and skinny) makes sense, provided constant - or at least frequent - thrust. The Savage Chicken from the webcomic Freefall has an interesting compromise - many of the amenities rotate or are otherwise setup to work under either situation. For example, the tables have booth-style seating, and the seats are setup so that the seat and back are functionally interchangeable, while the table can rotate for either orientation. That example can be see here.

Another consideration - the bridge being located at the front of the ship, with a big transparent "window" to see out of. That's fine for a "spaceship" that's going to spend most of its time flying around planetside (such as for The Savage Chicken), but realistically the bridge being further in, and relying on the ship's sensors, makes a lot more sense (using Spaceships, a Control Room in one of the Core sections is going to be much more well-protected than one elsewhere, although I think ejecting your Control Room in an emergency isn't available if you do that). Things in space are, quite frankly, too far away for the human eye to be of any use - and given the velocities necessary to get anywhere, by they time you can see something, it's too late for you to do anything about it. Best to avoid a big honking weakspot (transparent materials are unlikely to be as resilient as opaque ones) that doesn't even accomplish anything for you. Luxury spacecraft and the like, however, may well have direct viewports, for those wanting to see space with their own eyes rather than through a camera.

[Fred Brackin]

Originally Posted by Varyon

A Things in space are, quite frankly, too far away for the human eye to be of any use - .

The ship's instruments should do it better but you have to factor in brightness against distance. Stars are far away but still visible.

I once saw the calculation that one of Transhuman Space's fusion pulse drives with about 30 GW of output leaving Mars orbit could be seen with the naked eye from Earth orbit.

You'd still want the computer to tell you exactly how far away it was and how fast it was going but in some universes early detection with the human eye isn't that unreasonable.

[Frost]

Originally Posted by Fred Brackin

The ship's instruments should do it better but you have to factor in brightness against distance. Stars are far away but still visible.

I once saw the calculation that one of Transhuman Space's fusion pulse drives with about 30 GW of output leaving Mars orbit could be seen with the naked eye from Earth orbit.

You'd still want the computer to tell you exactly how far away it was and how fast it was going but in some universes early detection with the human eye isn't that unreasonable.

Even if early detection and navigation by direct observation are not practical I would still expect most long range ships to have a viewing port of some description (although probably only one) mostly for morale reasons.

While most of the time there is nothing to see I think there is a psychological case for actually being able to see outside without any sort of mediation.

At a guess these ports would be located as far as possible from the most vital parts of the habitat and heavily shuttered rather than the classic picture window on the flight deck.

[Frost]

Originally Posted by Varyon

An interesting consideration when it comes to gravity is for spacecraft that are meant to operate planetside as well as in space. Planetside, a layout like a modern airplane (long and short) makes sense, whereas in space, a layout like a tall tower (tall and skinny) makes sense, provided constant - or at least frequent - thrust. The Savage Chicken from the webcomic Freefall has an interesting compromise - many of the amenities rotate or are otherwise setup to work under either situation. For example, the tables have booth-style seating, and the seats are setup so that the seat and back are functionally interchangeable, while the table can rotate for either orientation. That example can be see here.

You make a good point aircraft style belly landing would actually be more convenient for managing cargo amongst other things.

But I think it would make more sense to put the main engine in the 'belly' so that gravity and main engine thrust were on the same axis rather than placing the main engine in the 'tail' and having build everything to handle loads in two directions and to reconfigure the ship every time you land or take off.

[Varyon]

Originally Posted by Frost

You make a good point aircraft style belly landing would actually be more convenient for managing cargo amongst other things.

But I think it would make more sense to put the main engine in the 'belly' so that gravity and main engine thrust were on the same axis rather than placing the main engine in the 'tail' and having build everything to handle loads in two directions and to reconfigure the ship every time you land or take off.

An interface craft (that is, one that is designed both for planetary and space travel) that deals exclusively with airless worlds could pull that off, but typically you'd want something more aerodynamic for travel through atmosphere. If you can vector your thrust, switching it to be in the belly while in space would let you generally maintain the same "down" direction, but I suspect the mass cost associated with doing that isn't worth the convenience. Really, I think just designing the living/working areas so that they can work with either orientation would be less problematic (and humans adapt to things well enough that doing the switch would be, at worst, a momentary problem for someone unused to travel in an interface craft) - but I could be mistaken.

[Phil Masters]

Originally Posted by FF_Ninja

To give you a point of reference: I don't see any functional or physical inconsistencies or design flaws with the typical Star Trek and Star Wars faire.

If you're going to be using media references and are trying for some kind of approximate plausibility, The Expanse is a much, much better bet than Trek or SW. That merely has insanely powerful and efficient reaction drives and no radiators, which is a miracle of plausibility by media SF standards.

Originally Posted by FF_Ninja

My plan is to design an entire hierarchy of new ships for futuristic Earth, starting from the earliest space-fairing vessels, gradually incorporating FTL into the design (haven't settled on what FTL actually looks like in this setting), and building on that form factor over time.

FTL is usually a magic black box that gets you between locations. A much more important question is usually whether you're going to have magic reactionless thrusters and artificial gravity. Ladle enough miracle-tech on and quietly forget that space has a third dimension and you can have spaceships impersonating WWII battleships and fighters, and your spaceships will look nothing like anything built with current tech.

[Ulzgoroth]

Originally Posted by Michael Thayne

The video game Children of a Dead Earth claims to be rigorously realistic in almost all respects and the ships look pretty cool IMHO. Incidentally, the warships in that game tend to have pointy noses even though they're not intended to fly in atmosphere. Rather, the game is trying to model the benefits of using sloped armor.

It's been a few years since I dipped into it but I don't think the benefits of sloping as such were very significant. But using a tapering nose to allow more frontal weapon mountings so you could attack head-on rather than needing to swing broadside and expose a much larger aspect was quite useful. Also it gave you thicker effective front armor without having to mess with the controls (and possible penalties) for adding armor layers that only covered a portion of the ship.

Of course, that's influenced by the game leaning to sustained gun engagements by preference, but you certainly could build a missile carrier that used efficient atomic rockets to drop missiles onto high-speed intercepts where they'd proceed to punch through anything in their path. I did that at one point, pretty sure it made a mockery of all the big battleships. (It might have been vulnerable to flares though, since the game made missile guidance highly vulnerable to decoys.)