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Old 10-20-2019, 03:08 AM   #11
Anthony
 
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Default Re: Spaceship Weapons and Gravity Layout

It is worth considering whether the entire interior of the ship will even have the same alignment. You could, for example, replace stairwells with passageways that have gravity flipped 90 degrees.
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Old 10-20-2019, 03:56 AM   #12
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Default Re: Spaceship Weapons and Gravity Layout

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Originally Posted by ericthered View Post
The rocket orientation makes thrust and artificial gravity stress in the same direction, but gives a single point of failure for artificial gravity. ... 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.
Take the rocket/skyscraper orientation. Gravity is normally generated by an attractive disc at the lowest deck, but there are backup attractive discs on higher decks. Your final reserve gravity is a repulsive disk at the highest deck, with only weapons above it. It is normally switched off.

It means gravity is subject to inversion from battle damage on the lower decks, so you mostly put big heavy things, like engines, on those decks, and design them to work with either direction of gravity. The weapons in the nose are also subject to inversion, so you need to design them the same way.

People and all the clutter they generate are on the middle higher decks, so that the gravity won't go out there unless the ship is catastrophically damaged.
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Old 10-20-2019, 05:47 AM   #13
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Default Re: Spaceship Weapons and Gravity Layout

Is there a utility in having main personnel and control spaces in gimbals? You could put the gravity plates inside the gimballed room, and they would freely rotate to be normal to whatever thrust vector or external gravity well you have.

It would give the ship a collection-of-spheres-and-domes aesthetic.

The other thing to consider is having spherical shells of gravity plate for each crew space, so that they could cancel out acceleration vectors that skew from the normal.
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Old 10-20-2019, 10:20 AM   #14
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Default Re: Spaceship Weapons and Gravity Layout

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Originally Posted by Anaraxes View Post
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.
So far as I can tell, spheres require considerably more structure for the same amount of acceleration stress than other configurations. The minimum structural mass is found in a thin-walled cylinder, which maximizes the area moment of inertia. Stacked cylinders of decreasing size form a cone.

Minimizing surface area is useful primarily for economizing on physical armor. If shields are a thing or ships aren't heavily armored (which is the case with most reaction-drive settings, even superscience ones), more surface area actually helps with placing weapons, sensors, radiators, etc.
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Old 10-20-2019, 01:18 PM   #15
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Default Re: Spaceship Weapons and Gravity Layout

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So far as I can tell, spheres require considerably more structure for the same amount of acceleration stress than other configurations.
They are, however, appreciably superior for resisting pressure; which matters more depends on the details of your drives.
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Old 10-20-2019, 04:13 PM   #16
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Is there a utility in having main personnel and control spaces in gimbals?
There might well be, on a ship designed to alternate between 'acceleration gravity' and 'spin gravity', it would save a lot of time and work rearranging everything when the ship turned the drive on and off.

But it just looks like added complexity with the g-disks, when you could instead just line everything up with the axis of thrust.
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Old 10-20-2019, 09:45 PM   #17
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Default Re: Spaceship Weapons and Gravity Layout

Thanks for the suggestions folks. You are really helping me to work through my ideas and giving good ideas for clever architecture with this setup.

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Originally Posted by Fred Brackin View Post
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.
I was thinking about evasive action. Accelerating your ship towards your foe doesn't through off their range very much, while moving to the side does. That doesn't let you chase them very effectively though. Though if you're chasing them, you presumably have a fire power advantage and can afford to increase the size of the target presented.

On the other hand, I'm not sure if turning/twisting the entire ship for evasive maneuvers is actually an effective dodge. It certainly is for projectile fire. With beams you need to be dodging the tracking, not the shot, so that could be very dps intensive.

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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.
I think that's overstated: that effectively makes it so they're standing on a 5 degree slope, and sailors have been dealing with pitching decks for a long time.

That said, I do think I'm convinced I need to either line up the ship's gravity with the primary thrust or use a rather slow drive. I'm not convinced that the ship needs to be a long thin cylinder with the engines at one end.

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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.
No, its a space-only craft

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It is worth considering whether the entire interior of the ship will even have the same alignment. You could, for example, replace stairwells with passageways that have gravity flipped 90 degrees.
The symmetric effect of the disks make doing that sort of thing rather tricky. I thought about the specific stairwell situation, and it is possible, but only if the stairwells are on the outside of the ship or if you split the passage into two halves, each with opposite gravity. The key to the trick is to cancel the main gravity with second, much smaller disk quite close to the main one, but with an opposite gravity. That gives a cylinder of neutral gravity, and you can either leave it or set up a second set of plates in the new direction.

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Originally Posted by johndallman View Post
Take the rocket/skyscraper orientation. Gravity is normally generated by an attractive disc at the lowest deck, but there are backup attractive discs on higher decks. Your final reserve gravity is a repulsive disk at the highest deck, with only weapons above it. It is normally switched off.

It means gravity is subject to inversion from battle damage on the lower decks, so you mostly put big heavy things, like engines, on those decks, and design them to work with either direction of gravity. The weapons in the nose are also subject to inversion, so you need to design them the same way.

People and all the clutter they generate are on the middle higher decks, so that the gravity won't go out there unless the ship is catastrophically damaged.
That's a neat trick. Thanks for the suggestion.

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Originally Posted by Daigoro View Post
Is there a utility in having main personnel and control spaces in gimbals? You could put the gravity plates inside the gimballed room, and they would freely rotate to be normal to whatever thrust vector or external gravity well you have.

It would give the ship a collection-of-spheres-and-domes aesthetic.

The other thing to consider is having spherical shells of gravity plate for each crew space, so that they could cancel out acceleration vectors that skew from the normal.
I think both ideas are possible. I'm not so sure that they fit the scenario though. Both systems seem rather delicate, and do unpredictable things to the gravity just outside of the "safe zones". They would be nice if you keep the humans in there all the time and your ship is mostly machinery that doesn't need to be accessed by humans, but both I and the admiralty very much planning to send PC's all over this ship among its guts, and I'd like for gravity to be present there.

The ideas might have some merit in high performance fighters.
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Old 10-21-2019, 04:05 AM   #18
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Default Re: Spaceship Weapons and Gravity Layout

Just to explore the idea a little:

With the gravity plates, gravity can be set arbitrarily, so there's no reason for it to be the same direction across the whole ship.

You might have the command bridge with naval setting, so they can walk around and look out the front of the bridge (said gimballing optional). The problem with rocket-orientation is that you have to lie on your back to see where you're going- unless everything is done by instruments only.

The drive section at the rear might be rocket-down, so that equipment is attached to the thrust-down direction of the ship. A shell of gravity plates could be used to help lifting heavy equipment around.

Long axial corridors would be gravity radially down toward the ship's axis, as it would be a long dangerous fall with gravity axially down the corridor. Set strength to 0.2 G so that crew can quickly moon-hop along to their destinations.

I'm not sure how you'd handle transition sections between orthogonal G-zones, though they might be 0G for easy body rotation to orient to the G-vector for where you're headed.

And so on.

Note that crew should be secured during combat and maneuvres, just as you don't let your airline passengers walk around during turbulence.

The question is how big are the grav plates? How heavy? How much energy do they use? i.e. What are the economics of installing and running them? Can they be put anywhere and everywhere, or does their design limit how they can be used?

And how switchable and responsive are they? If they're effectively instantaneous, then they can be basically inertial dampeners.
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Old 10-21-2019, 11:13 AM   #19
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Default Re: Spaceship Weapons and Gravity Layout

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Originally Posted by ericthered View Post
T
I think that's overstated: that effectively makes it so they're standing on a 5 degree slope, and sailors have been dealing with pitching decks for a long time.
Try pouring hot coffee or going to the bathroom with that "5 degree slope" theory and you might not like the result. :)

More seriously, you don't do either while undergoing combat maneuvering but the lower you set your acceleration the longer the periods you have to use it for effective travel. If you had only minutes of multi-G burns for Hohman transfer orbit insertion you just strap everyone in for the duration.

When the duration is hours or even days you really don't want to have your artificial gravity and acceleration going in different directions. Probably the main reason you have artifical gravity is that zero-G plumbing doesn't work very well. You'll want to design for long durations of every day life ass your default condition. You can get hrough minutes of acceleration and space battles with strapping in and keeping a stiff upper lip but hours and days of ordinary living should be as ordinary as you can manage.

As for Dodging you don't do that with the main drive for big ships anyway. You can't turn the hsip fast enough to bring main propulsion intot eh line you want. You have to use relatively large attitude thrusters that are scattered all over your hull.
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Old 10-21-2019, 04:25 PM   #20
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Default Re: Spaceship Weapons and Gravity Layout

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You might have the command bridge with naval setting, so they can walk around and look out the front of the bridge (said gimballing optional). The problem with rocket-orientation is that you have to lie on your back to see where you're going- unless everything is done by instruments only.
Everything probably is done by instruments only, as in the combat command centre of a modern warship.

Huge transparent windows to look out of all around present too great a vulnerability, because they are very difficult to armour and to protect with meteroid shielding. Putting the command room on the surface makes it hard for radiation shielding; you want people in the guts of the ship, surrounded by machines and tankage. The human eyeball is not sensitive enougb and doesn't have enough resolving power to be a useful sensor of small, dark things at great distances. And finally, the direction of the thrust vector is the direction the ship accelerates towards, not necessary the direction it moves towards. Thrustwards is forwards when you're accelerating, but the opposite when you a decelerating, besides which for a lot of maneuvres you'll accelerate at some angle up to a right angle to your direction of movement in the frame of reference of nearby illuminated objects. When you are doing a fast flypast you can orient any part of your surface that you choose also your vector of relative movement. When you arrive at a "place" you end your manoeuvres with a decelerate with respect to the destination, i.e. main engine forwards. To see where you were going with naked eyes you would lie face down, not on your back.

There is no gravity, so there is no "upwards". There is no atmosphere or ocean, so there is no "forwards". What direction you are going is a matter of "in what frame of reference?": in the ship's frame it isn't moving. Everything, including your destination and port of origin, is moving in all sorts of directions at speeds of several kilometres per second, while you are by definition stationary. The only direction that is significant is your thrust axis.
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