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

[Ulzgoroth]

Originally Posted by Phil Masters

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.

FTL is usually a conceptual magic black box to a large extent, but it's not uncommon for it to have distinctive architectural/aesthetic implications. Examples include:
-Star Trek warp nacelles
-The 'ship-in-a-hoop' designs you can see in a number of properties but for an easy visual Sword of the Stars human ships have this.

[FF_Ninja]

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.

So, Firefly's Serenity did handle this issue fairly well. It had a massive rear engine, but it also had two sizable engines (one on either side) that could be rotated downward to provide downward thrust for landing/take-off or rearward to provide additional forward thrust. Or, I guess, rotated forward to provide rearward thrust.

It mimicked VTOL craft that we have in real life, such as the V-22 Osprey that the marines use. Multi-vector thrust makes sense even when you hit higher TLs.

[Fred Brackin]

Originally Posted by FF_Ninja

So, Firefly's Serenity did handle this issue fairly well. It had a massive rear engine, but it also had two sizable engines (one on either side) that could be rotated downward to provide downward thrust for landing/take-off or rearward to provide additional forward thrust. Or, I guess, rotated forward to provide rearward thrust.

The swivel engines were the atmospheric propulsion system. they could be turned all the way to the front. You see this done (for one engine only) in the "Crazy Ivan" maneuver in (ISTR) the pilot. They shut off when you hit orbit.

Guesses at how they work mostly center around what's usually called a "grav-ram" that pulls air (and the occaissional human body) through the engine with intense artificial gravity. It obviously has no internal fans or blades.

The big engine at the back is for space propulsion only and its' mode of function is utterly mysterious. It does appear to involve that spinning _thing_ in Kaylee's engine room (but it uses no fuel). Rotary motion is important to many forms of spece travel.

Possibly a Rotary Reactionless in Spaceships terms.

[FenrisLoki]

If you have fun things like a reaction less drive, a sphere is probably the best design with the engine at the center of the sphere and mounted on gimbals. You could then thrust in any direction, just dependent on how fast your can rotate the drive unit.

[Anthony]

Originally Posted by FenrisLoki

If you have fun things like a reaction less drive, a sphere is probably the best design with the engine at the center of the sphere and mounted on gimbals.

Depends a lot on the details of the drive system and of what problems you expect to deal with. A sphere is good for shielding from omnidirectional hazards and threats, but it's a bad shape for packing and directional hazards (preferred shape depends on the details of the hazard). Also, there's a question of whether you actually need an outer hull at all, real-world spacecraft don't really have one unless they're expected to operate in atmosphere.

It's perfectly possible to design your tech so, say, flying saucers are a favored shape.

[Kaspar]

Here is a realistic ship design:

Take the star destroyer’s dagger shape. Remove the stupid tower. Flatten the hull somewhat to minimize the profile when viewed from front or sides. Add two ‘wings’ of heat radiators to the sides. An enemy approaching from sides or front would only see the edges of the radiators.
[Common fleet tactic would be to split your fleet in at least two groups, to attack the enemy from different angles, but the enemy undoubtedly will try the same…]

The radiators are made resistant to damage- hits would just blow through with minimum damage. The ‘capillary’ pipe network pumping the coolant would self-seal at the edges of a hole to stop leakage.

A row of turrets are placed on the central ridge of the hull (and another row on the underside ridge). This way, all of them can fire forward or to the sides. Attackers from the top (or bottom) would face one row of turrets, guns pivoted up. However only the last pair of turrets can point backwards.

One or more spinal mount guns point forward, spanning the length of the ship.

Random walking to dodge incoming shots is of course important, but it is not worth reducing your max speed by having thrusters point in different directions, so put them all at the rear. Random walking is performed by varying your thrust and using the RCS to swing the ship’s bow in different directions.

Armor is ablative- probably aero-gel in honeycombed pattern with empty spaces within to deal with spalling effects. Thermal super-conducting cables (possible according to know science) could be threaded throughout the hull to try to prevent local hit spots. The outer layer is highly reflective foil to minimize than amount of heat absorbed from long-range lasers and distant nuclear detonations.

[Laser beams spread out with range, but even if your beam has a spot diameter of 100m, does not mean you can’t still hurt the enemy by heating up their hull and jamming/damaging their sensors. And the wide beam makes it easier to hit the target. Of course, if your ship is the same size, you will accumulate waste heat faster than you impart it to the enemy, but if you are bigger or have multiple ships focusing on one opponent, it could work.]

No armor can withstand a point blank nuke, so it is the point defense’s job to stop incoming missiles.

What weapons would the ship carry? Options are:
Missiles: Toss them out a cargo hatch and let them fly. They could have a booster stage to get them close to enemy (possibly MIRVs delivering multiple warheads at once). At the edge of enemy‘s point defense zone the warheads separate and use their own thrusters to dodge through (while deploying chaff and decoys). Payload options are shaped charge nukes (get as close as possible, detonate when hit by point defense and try fry the enemy), nuke pumped energy beams (basically, a rod that will channel a good fraction of the blast energy in a specific direction as it gets disintegrated), or frag warheads that use a chemical explosive to shatter in an expanding cone of shrapnel.

You would want to use missiles in swarms to overwhelm the enemy point defense, but you could aslo launch a few ahead to test PD capability (but the enemy might also choose to obfuscate things by not using full capacity against mere probing attacks…).

Smart kinetics: If you can make electronics tough enough to survive being accelerated by a railgun (massive g-forces and exposure to powerful electromagnetic fields), you can also launch warheads from your spinal mounted barrel. Same payload options as before. Probably faster velocities than all-self-propelled missiles, but harder to stage in swarms.

Dumb kinetics: Just a chunk of metal fired from a railgun. Good for stationary targets. But can you hit something at the other side of the star system? Just because your math is perfect, does not mean the railgun has perfect accuracy, and over multiple astronomic units the projectile drift will accumulate.

Particle beams- ions are fired from a particle accelerator. As they leave the barrel, electrons are added to the beam to make it neutral and stop the particles from repelling each other.

Lasers: Unlike railguns and particle accelerator, laser emitters are wide not long, better suited for turrets. Best option for point defense.

[FF_Ninja]

Originally Posted by Kaspar

Here is a realistic ship design:
...

I like it. It's a good intermediary place to be for a design hierarchy: more sophisticated than the first forays into space, but plenty of room to adapt superscience-y bits into the design as technological advances are made.

I think it's really important to answer as many questions from a hard realism standpoint as possible before applying superscience to them later. Keeps you (and your designs) honest.

[Varyon]

Originally Posted by Fred Brackin

The big engine at the back is for space propulsion only and its' mode of function is utterly mysterious. It does appear to involve that spinning _thing_ in Kaylee's engine room (but it uses no fuel). Rotary motion is important to many forms of spece travel.

Possibly a Rotary Reactionless in Spaceships terms.

I think the Firefly Role Playing Game indicated the large drives for space travel were roughly akin to what GURPS Spaceships would label pseudovelocity boost drives - they couldn't be used to ram anything, they didn't really accelerate or decelerate (just worked at a given pseudospeed, more or less), and if they get turned off, you basically come to a dead stop (as was the case in "Out of Gas"). They could only move in a straight line; if you need to make an adjustment, you've got to shut it down, reorient, and then get going again. I believe they did use a bit of fuel, but only to initially get going.

They also served as the ship's power source, powering the artificial gravity, CO2 scrubbers, etc. They could serve in this capacity even when the ship was stationary, at least so long as they were in working order.

[cptbutton]

Originally Posted by Fred Brackin

The big engine at the back is for space propulsion only and its' mode of function is utterly mysterious. It does appear to involve that spinning _thing_ in Kaylee's engine room (but it uses no fuel). Rotary motion is important to many forms of spece travel.

Possibly a Rotary Reactionless in Spaceships terms.

Sounds like a Dean Drive derivative.

[Rupert]

Originally Posted by FenrisLoki

If you have fun things like a reaction less drive, a sphere is probably the best design with the engine at the center of the sphere and mounted on gimbals. You could then thrust in any direction, just dependent on how fast your can rotate the drive unit.

The early Skylarks in E.E. 'Doc' Smith's Skylark series of novels were spherical for this reason, complete with centre-mounted drive.