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

[FF_Ninja]

I'm going to be spending some time in Inkscape and GIMP over the next few days working on some custom top-down spaceship layouts for use in a campaign later. In preparation for this, I started looking today for reference models (starting with my old stomping grounds, CGSociety).

It then ocurred to me that I'm highly influenced by sensational, flashy, exotic designs - and I don't have a clue what's more functional and realistic versus what might be highly improbably or unlikely a design feature to be incorporated.

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.

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.

I would very much prefer to approach my designs with a practical understanding of what "would" and "wouldn't" make sense, rather than throwing elements together in an arbitrary fashion.

For those of you who consider yourselves more of an authority on "space-y" things, I would appreciate any insight into what would make sense in terms of spaceship design and form, and I appreciate any commentary on examples in media that stand out in one way or another.

Thank you all very kindly.

[FenrisLoki]

So realism is not really a strong point of Star Wars or Star Trek designs. Those are mostly aesthetic. Swoopy closed shapes are fine, but unless your FTL system has a fluid "drag" in its hypothetical physics, there's no real reason for it. People may decide to build that way, but it isn't a necessity.

Babylon 5 had some of the more realistic designs for space travel with the tech from Earth. Their small fighters had large engines away from the center of mass for rapid turns (not necessarily comfortable for the pilot though). The alien designs were again mostly aesthetic.

A truly realistic design will depend on whether the ship will land. Then wings or a lifting body will be a necessity for reentry and travel in an atmosphere. Otherwise the ship could be just an empty framework.

Transhuman Space has a lot of realistic, hard-science ship designs.

[Michael Thayne]

A key problem with a lot of fictional spacecraft designs is that they have bilateral symmetry, instead of being either radially symmetrical or having two planes of symmetry intersecting at the center of thrust. On Star Trek, the Stargazer is a rare example of a ship that more or less does the two planes of symmetry thing right. Bilateral symmetry only makes sense for spaceplanes, and wildly asymmetrical designs almost never make sense. (Technically, you can get away with a lot as long as your axis of thrust passes through your center of mass, but engineers will usually find that trying to satisfy that requirement with an asymmetrical design is more trouble than its worth.)

[FF_Ninja]

It just occurred to me how very likely a poor design the Millenium Falcon is by those standards.

[Anthony]

Originally Posted by Michael Thayne

(Technically, you can get away with a lot as long as your axis of thrust passes through your center of mass, but engineers will usually find that trying to satisfy that requirement with an asymmetrical design is more trouble than its worth.)

It's not that rare -- if you look at models of deep space probes, a lot of them have asymmetric spikes of one sort or another. For example, Cassini is mostly symmetrical but has a single long rod off to one side (not sure what it's for... possibly the RTG). However, you certainly don't do it without a reason.

Looking at models of real world space probes is a good place to start.

[thrash]

A lot depends on your tech assumptions. If you don't have force field reinforcement on your structure ("inertial damping fields") or other applied phlebotium, you should check that your design would make sense if you stood it on its engines (since that is effectively what happens when you accelerate). Don't forget that cargo (including munitions) and fuel/reaction mass will vary a lot over time, so those have to balance around the center line.

Likewise, no one ever gets required radiator area even vaguely correct, because it looks terrible and would be lethally fragile in a fight. (Discovery, from 2001, was as long and skinny as it was because it was supposed to have realistic radiator fins all along its length. It looked dumb, however, so they were deleted.)

Finally, remember: form follows function. Freighters prioritize cargo space; warships emphasize weapon systems. Neither one puts a premium on comfortable quarters for the crew. Any ship with a balance of all three is questionable, unless it really is a rich person's privately owned, purpose-built yacht-and-pirate-hunter. Choose the role for each class and optimize for it.

[thrash]

Originally Posted by Anthony

For example, Cassini is mostly symmetrical but has a single long rod off to one side (not sure what it's for... possibly the RTG).

Magnetometer arm, which was sensitive enough that it had to be away from the other electronic components. The RTGs were used to balance the arm, however, since it was light but long and they were dense but close in.

[Michael Thayne]

Originally Posted by FF_Ninja

It just occurred to me how very likely a poor design the Millenium Falcon is by those standards.

The Millennium Falcon could be worse! For example, it has one weapon turret on top and another on the bottom, which both avoids throwing off the balance, and prevents the ship from having a vulnerable underbelly which would be a much bigger liability in a 3D combat environment than it is at land/sea. The big problem with the Falcon is the pilot can't see anything going on to his left.

Originally Posted by Anthony

It's not that rare -- if you look at models of deep space probes, a lot of them have asymmetric spikes of one sort or another. For example, Cassini is mostly symmetrical but has a single long rod off to one side (not sure what it's for... possibly the RTG). However, you certainly don't do it without a reason.

Looking at models of real world space probes is a good place to start.

Originally Posted by thrash

Magnetometer arm, which was sensitive enough that it had to be away from the other electronic components. The RTGs were used to balance the arm, however, since it was light but long and they were dense but close in.

Yeah. I should have said "modulo the occasional small component that can easily be counterbalanced by another small component."

[thrash]

Originally Posted by FF_Ninja

It just occurred to me how very likely a poor design the Millenium Falcon is by those standards.

Best justification I've seen for Millenium Falcon is that the class was originally a kind of space tug. A rack of cargo containers was slotted in between the "mandibles." The engines were sized for a full load, and therefore oversized when unloaded. The cockpit and sensor dish were offset for visibility. There wasn't any real need for cargo holds.

I had a heck of a time coming up with a similar rationale for Serenity. Best I could do was a long range landing craft, with a mission similar to a Landing Craft, Utility.

[Michael Thayne]

Originally Posted by thrash

Likewise, no one ever gets required radiator area even vaguely correct, because it looks terrible and would be lethally fragile in a fight. (Discovery, from 2001, was as long and skinny as it was because it was supposed to have realistic radiator fins all along its length. It looked dumb, however, so they were deleted.)

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.