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Old 10-19-2019, 08:18 AM   #1
ericthered
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Default Spaceship Weapons and Gravity Layout

I'm laying out a super-science battleship for a damage control scenario, which gets more into the nitty-gritty of the ship than many other activities, and I could use some advice on how to lay the ship out.

The ship will be using artificial gravity. This is generated by grav-disks that apply either an attractive or a repulsive force to each side in a symmetric cylinder centered on the disk. Stacking a disk on each level requires changing the direction of gravity each time you pass a plate, which seems undesirable (likely at least 6 decks, if not more).

I'm thinking the ship should be long and thin so that it can present a minimal profile to opponents. I'm tentatively sticking the engines (super-science boosted reaction engines) on the other side of the minimal profile. I'm unsure if I should orient the gravity down towards the engines, so the ship is built like a rocket or sky scraper, or if I should pick a long side of the ship to be "down", and orient the thing like a naval ship.

The rocket orientation makes thrust and artificial gravity stress in the same direction, but gives a single point of failure for artificial gravity. It makes it easier to put gravity over the whole ship, but I'm not sure if that is a good thing or not. Conversely, the naval orientation looses gravity in chunks, rather than all at once, but doesn't line up with the thrust and is likely to result in corners of microgravity. Microgravity in the ship is considered a bad thing: most the crew is only passably trained for it, and when the gravity gets turned off all sorts of things come loose on a lived in ship. Does anyone have idea on how to arrange backup gravity systems? The assumption is if the gravity is out its because the grav-disk generating it has been hit, so a nearby backup isn't an option.

I'm trying to figure out the layout of the guns. My two initial ideas are putting the main turrets all on one long side of the ship, sloped towards the front. This is to allow the ship to concentrate fire in one direction. The other option is to slope all of the sides towards the front and place the main turrets all the way around the ship. Point defense guns will need to be fairly evenly distributed around the ship, though putting extra in the same direction as the main turrets is likely a good idea. I'm also unsure if there is is a benefit to orienting turrets in a specific direction with regards to gravity.

The ship has shields, so armor layout isn't as important as it might be, though structural integrity and relative compactness is still nice. And the ship will still be getting hit.

What am I missing? How would you lay out the ship? Thanks for the advice!
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Old 10-19-2019, 08:54 AM   #2
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Default Re: Spaceship Weapons and Gravity Layout

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Originally Posted by ericthered View Post
The ship will be using artificial gravity. This is generated by grav-disks that apply either an attractive or a repulsive force to each side in a symmetric cylinder centered on the disk. Stacking a disk on each level requires changing the direction of gravity each time you pass a plate, which seems undesirable (likely at least 6 decks, if not more).
Not sure I understand this. Are you saying that each disk generates either a repulsive or an attractive force, but not both (say, attractive on one side and repulsive on the other)? Is the gravity vector oriented perpendicular to the plate (flat side up/down) or parallel to it (with the plate as sort of an end-cap on the cylinder)?

Quote:
I'm thinking the ship should be long and thin so that it can present a minimal profile to opponents. I'm tentatively sticking the engines (super-science boosted reaction engines) on the other side of the minimal profile. I'm unsure if I should orient the gravity down towards the engines, so the ship is built like a rocket or sky scraper, or if I should pick a long side of the ship to be "down", and orient the thing like a naval ship.
Stacking like a skyscraper is the way to go. The only advantage of what you call naval orientation (besides being simpler to draw and cheaper for Earthly special effects budgets) is that it's easy to move the length of the ship -- but that turns into a disadvantage when the gravity is off.

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I'm trying to figure out the layout of the guns. ... The other option is to slope all of the sides towards the front and place the main turrets all the way around the ship.
This. Your ship is a long, thin cone, with the main battery ranked to concentrate fire forward (over each other's shoulders, as it were).

If your reaction engine system allows (e.g., doesn't spew radioactive death), it is helpful to place the main engines closer to amidships and make the hull a double cone. This reduces stress on the hull by reducing the "height" from the drive plane, and makes the ship easier to turn. You would need secondary batteries for the rear arc, but now you have some surface area to mount them. You could also have room for (e.g.) launching and recovering small craft without entering the main battery's firing arc.
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Old 10-19-2019, 09:21 AM   #3
ericthered
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Default Re: Spaceship Weapons and Gravity Layout

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Originally Posted by thrash View Post
Not sure I understand this. Are you saying that each disk generates either a repulsive or an attractive force, but not both (say, attractive on one side and repulsive on the other)? Is the gravity vector oriented perpendicular to the plate (flat side up/down) or parallel to it (with the plate as sort of an end-cap on the cylinder)?
Yes, the disk is either attractive or repulsive towards the disk in the center. The gravity vector is perpendicular to the disk, so you could stand on each side of an attractive disk with your feet being pulled towards the "Floor" created by the disk.

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Stacking like a skyscraper is the way to go. The only advantage of what you call naval orientation (besides being simpler to draw and cheaper for Earthly special effects budgets) is that it's easy to move the length of the ship -- but that turns into a disadvantage when the gravity is off.
Could you expand on this? You haven't said what you feel the advantages of skyscraper orientation are.

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If your reaction engine system allows (e.g., doesn't spew radioactive death), it is helpful to place the main engines closer to amidships and make the hull a double cone.
The reaction engines are fairly energetic, but mounting them off to the sides and towards the center of the ship should be possible. That does help with the turning, though I'm still thinking about using wheels to control attitude without spending dps.

It might also be interesting to mount the main gravity plate of a skyscraper layout in the middle of this ship, having the effective height. You have to switch gravity orientation once, but that might not be a big deal. A bigger deal might be that you can't easily thread things like pipes, power conduits, and passageways through the disk, Though I could embrace using lots of smaller disks rather than one big one.
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Old 10-19-2019, 10:35 AM   #4
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Default Re: Spaceship Weapons and Gravity Layout

What kind of force do those disks provide? And what about your engines?
And skyscraper is your only option really, unless you want ppl slamming against the walls every time your ship accelerated.
And ofc if your disks provide a fixed 1G, you still have problems
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Old 10-19-2019, 10:44 AM   #5
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Default Re: Spaceship Weapons and Gravity Layout

For gravity backups, having attractor-repulsor pairs at opposite sides of the ship could work. With the naval orientation, for example, you could have an array of attractor disks in the ventral portion of the ship, with a corresponding array of repulsor disks in the dorsal portion. For the crew, the attractive and repulsive forces would be in the same direction (“down”) and would probably be indistinguishable from each other. Up to you if you want both to generally be “on” (and thus loss of one cuts gravity in half, potentially adjustable back up to full) or if you want to have one always on and the other to turn on only when needed (so loss of one either has no effect or causes a brief few moments of zero G before the backup turns on). You should be able to manage a similar scheme with the rocket orientation as well.

Also, unless loss of gravity is unlikely without leading shortly to the destruction of the ship, the crew should be well-trained for zero G, and SOP should be to secure any loose tools/etc as soon as one is done using them (built-in electromagnets to let you stick it to any nearby metal surface when not in use would be useful). The skills are too important in space to neglect, and training isn’t exactly difficult when you’re already in space (just shut off the gravity to train).
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Old 10-19-2019, 10:44 AM   #6
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Default Re: Spaceship Weapons and Gravity Layout

Skyscraper orientation aligns the gravity direction with the thrust direction. So, if you give the gravity generators sensors (or connect them to the engine controls; either way gives you more stuff to break and thus have to fix to get the gravity under control), you can automatically reduce the gravity as the thrust increases, or even flip the orientation of the gravity vector (if the tech allows) to counter thrust over 1G. If it's naval-ship orientation, with the "rockets" oriented out the "stern", then any significant thrust is going to be a sideways shove on the crew. That's especially bad if that thrust level changes a lot (say, to randomize the ship's vector), or if thrust is high (so the crew couldn't stand up while the ship was thrusting).

Note that on Earth, "naval ship orientation" is really the same as "skyscraper orientation". Both are aligned so that the decks / floors are perpendicular to the predominant direction of gravity ("down"). If you have high thrust that's often used, then the predominant direction is the direction of thrust. So it only makes sense to align the ship to take that into account, even if you have artificial gravity as a supplement. If the ship uses thrust only briefly and spends most of its time coasting, like a modern-day space probe, or has very low thrust, then you might ignore that direction as irrelevant during the mission.

Naval ships are narrow compared to their length for hydrodynamic reasons -- less drag on the hull makes for a faster ship, though they have to keep some width for stability. Skyscraper are tall compared to their width because land in downtown cities is scarce and expensive and bought by area, not volume. (Also ego...) Neither of those factors are relevant in space. You might want a long, pointy ship just for the sake of tradition, but that's not really dictated by the environment. The fact that you have to travel more against gravity in a skyscraper (hence elevators), while you can walk horizontally over more of a ship, is a practical advantage for the ship layout, but it's not a dominant factor. (Besides, elevators are just another fun thing to break, right?)

A sphere gives you the most volume for the area of the hull, and minimizes the travel distance between points inside the ship. (Not that travel is normally random; the architects will no doubt take into account where people have to get to in their jobs when choosing a layout.) Spheres also minimize the moment of inertia, so they can likely more easily change direction than a long, thin object. You don't have to have spherical ships, but other shapes will have a reason for their existence.
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Old 10-19-2019, 11:54 AM   #7
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Default Re: Spaceship Weapons and Gravity Layout

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Originally Posted by thrash View Post
N

This. Your ship is a long, thin cone, with the main battery ranked to concentrate fire forward (over each other's shoulders, as it were).
This. Call it "christmas tree plan" if that helps. Each "ornament" on the "christmas tree" can be a turret. All turrets will fire straight ahead and even converge on a single point directly ahead. The bottom row of turrets can fire backwards and half of any turrets can fire to one side. How energetic your drive exhaust is determines how necessary PD mount on the rear facing are.

Maneuvering in space battles is grossly overrated. Speed needs to be very high relative to weapon's range for it to be much use at all.

Your artifical gravity system is confusing to say the least. However, unless it completely negates acceleration forces "naval" orientation just isn't an option.
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Old 10-19-2019, 08:01 PM   #8
ericthered
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Default Re: Spaceship Weapons and Gravity Layout

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Originally Posted by Aldric View Post
What kind of force do those disks provide? And what about your engines?
And skyscraper is your only option really, unless you want ppl slamming against the walls every time your ship accelerated.
And if your disks provide a fixed 1G, you still have problems
Those are some really good questions. I haven't figured out what kind of acceleration I'm expecting out of the ship, and I probably need to. The disks can put out at least 1 G of force, and should be able to do more. I can see individual disks being incapable of going past 1 G, but it would be odd if the technology petered out at exactly 1 earth gravity. Varying their strength with time should be doable. I don't want to give the artificial gravity some real limitations, but varying its strength (and possibly even switching between being an attracting and a repelling disk) seems to make for fun nuances without handwaving away problems.

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Originally Posted by Varyon View Post
For gravity backups, having attractor-repulsor pairs at opposite sides of the ship could work. With the naval orientation, for example, you could have an array of attractor disks in the ventral portion of the ship, with a corresponding array of repulsor disks in the dorsal portion. For the crew, the attractive and repulsive forces would be in the same direction (“down”) and would probably be indistinguishable from each other. Up to you if you want both to generally be “on” (and thus loss of one cuts gravity in half, potentially adjustable back up to full) or if you want to have one always on and the other to turn on only when needed (so loss of one either has no effect or causes a brief few moments of zero G before the backup turns on). You should be able to manage a similar scheme with the rocket orientation as well.
Thanks, that's a good idea. And you're right, you don't have to run one as the main and the other as "backup": you just have two generators that can be stepped up or down.

Quote:
Also, unless loss of gravity is unlikely without leading shortly to the destruction of the ship, the crew should be well-trained for zero G, and SOP should be to secure any loose tools/etc as soon as one is done using them (built-in electromagnets to let you stick it to any nearby metal surface when not in use would be useful). The skills are too important in space to neglect, and training isn’t exactly difficult when you’re already in space (just shut off the gravity to train).
"Gravity Drills" are certainly easy to run. It can be used both as training and as a precaution to keep people from leaving things unsecured. (sometime between 01800 and 1900 we're turning off gravity and accelerating for 3 seconds). I'm thinking of running the scenario in wartime conditions, with reasonably green hands, but you're right: its simple to run rudimentary drills, and there is no reason not to.

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Originally Posted by Fred Brackin View Post
Maneuvering in space battles is grossly overrated. Speed needs to be very high relative to weapon's range for it to be much use at all.
That's the thing that makes me wonder if thrust aligning with gravity is that big of a deal. It seems that absolute speed doesn't matter, but altering course and changing facing does. I don't know how much skyscraper is going to help when you need most of your acceleration to be in a direction you were not previously headed.

Come to think of it, ideally you want to point a small surface towards your target and then have your main thrust come orthogonal to that. I'm not sure how that effects the structural stress on the craft. It also gets weird if you want to close with your target.

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This. Call it "christmas tree plan" if that helps. Each "ornament" on the "christmas tree" can be a turret. All turrets will fire straight ahead and even converge on a single point directly ahead. The bottom row of turrets can fire backwards and half of any turrets can fire to one side.
The armor needed in this situation is a little worrisome to me: you're exposing most of your surface area to your target. On the other hand, you naturally get the benefits of sloping your armor, and armor really isn't main line of defense for this craft. It requires precision to focus all of your fire at one ship, but that should be doable.

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Originally Posted by Anaraxes View Post
If you give the gravity generators sensors (or connect them to the engine controls; either way gives you more stuff to break and thus have to fix to get the gravity under control), you can automatically reduce the gravity as the thrust increases, or even flip the orientation of the gravity vector (if the tech allows) to counter thrust over 1G.
That's a really cool idea. I think it even works in naval configuration if you use a separate disk to cancel thrust than to provide artificial gravity, though if that gets out of wack people will complain.

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Note that on Earth, "naval ship orientation" is really the same as "skyscraper orientation". Both are aligned so that the decks / floors are perpendicular to the predominant direction of gravity ("down"). If you have high thrust that's often used, then the predominant direction is the direction of thrust. So it only makes sense to align the ship to take that into account, even if you have artificial gravity as a supplement.
eh, "orientation" here refers to which direction gravity pulls in respect to a long cylinder. The decks are always aligned down, but are the decks aligned with the length of the cylinder or do they break it up?

Lining up gravity and thrust is probably the best thing to do, I'm just trying to look at other knock-on effects.

Quote:
If the ship uses thrust only briefly and spends most of its time coasting, like a modern-day space probe, or has very low thrust, then you might ignore that direction as irrelevant during the mission.
That may be the case. When I envision this thing in my head its not a high performance craft: its a beefy ship that slugs it out with the enemy.

Quote:
Neither of those factors are relevant in space. You might want a long, pointy ship just for the sake of tradition, but that's not really dictated by the environment. The fact that you have to travel more against gravity in a skyscraper (hence elevators), while you can walk horizontally over more of a ship, is a practical advantage for the ship layout, but it's not a dominant factor. (Besides, elevators are just another fun thing to break, right?)

A sphere gives you the most volume for the area of the hull, and minimizes the travel distance between points inside the ship. (Not that travel is normally random; the architects will no doubt take into account where people have to get to in their jobs when choosing a layout.) Spheres also minimize the moment of inertia, so they can likely more easily change direction than a long, thin object. You don't have to have spherical ships, but other shapes will have a reason for their existence.
I think I want a long, pointy craft to minimize target area. orient yourself toward the enemy as a christmas tree or ship and you have half the profile or less than a sphere. On the other hand, if I make the shields a sphere, it may not matter what the physical shape of the ship is.

Quote:
You might want a long, pointy ship just for the sake of tradition, but that's not really dictated by the environment.
Tradition certainly has its place, especially in space opera. Often ships have a cool design as well, but even though I'm beginning to notice they're often laid out like an airplane/boat/space shuttle rather than like a rocket.
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Old 10-19-2019, 08:38 PM   #9
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Default Re: Spaceship Weapons and Gravity Layout

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Originally Posted by ericthered View Post


That's the thing that makes me wonder if thrust aligning with gravity is that big of a deal. It seems that absolute speed doesn't matter, but altering course and changing facing does. I
It's the other way around in my experience. Absolute speed determines whether you can force engagement but once you're in range changing direction is largely pointless. You should have entered range with all your weapons bearing and your opponets would ahve to be scattered over a _very_ large area of space for much effort to be required to change point of aim.

If you are going to maneuver this is exactly where naval orientation does not work. A crew can not operate with 1 G towards their feet and even 0.1 Gs behind or to the side of them. You could perhaps strap everyone in and turn off the artifical gravity but you'd still have problems for anyone not strapped in like damage control parties.

Naval orinetation requires virtually all of any accelration forces to be completely neutralized which is how things work in Star Wars and Star Trek. If you're not doing that you'll only see "naval" orientation in immobile space stations.
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Old 10-20-2019, 02:05 AM   #10
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Default Re: Spaceship Weapons and Gravity Layout

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Originally Posted by ericthered View Post
I'm thinking the ship should be long and thin so that it can present a minimal profile to opponents. I'm tentatively sticking the engines (super-science boosted reaction engines) on the other side of the minimal profile. I'm unsure if I should orient the gravity down towards the engines, so the ship is built like a rocket or sky scraper, or if I should pick a long side of the ship to be "down", and orient the thing like a naval ship.
In this case, 'skyscraper' looks like the way to go. If you design 'wet navy' style, and then your 'gravity disks' fail, suddenly the back wall is 'down' and the whole ship's internal orientation is skewed. Plus, if you've got 'gravity' coming from disks and acceleration at 90 degrees apart, your ship's internal structure will need some weird designs to accommodate the conflict and differing stresses.

One exception: does your ship ever enter atmospheres, land, or otherwise operate very near planetary surfaces? If so, the 'wet navy' arrangement can make landing and near-surface operations more convenient.
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