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[Insanegame27]

I had a thought today, and it probably sucks. What would the advantages and disadvantages be of a rotary shotgun. A minigun/rotary cannon arrangement which shoots shotgun shells and/or slugs?

[Amperzand]

The advantages of the two don't really mesh very well, I think. It'd certainly work mechanically, though.

Rotary guns today are generally for aircraft use, since something moving that fast needs to throw a lot of deadly stuff at a target in order to get a good hit likelyhood. That makes shotguns sound great, but they're generally quite close-ranged, and thoroughly useless against armor, whereas even the M134, which I believe is the lowest-powered military minigun, fires 7.62x51mm NATO, which is a true rifle cartridge, and quite effective against infantry at a considerable range.

[Incidentally, to avoid silliness, by "Close range" I mean 10-40 meters, which is reasonably doable for shotguns outside of vidjagaems with their magical evaporating pellets, who really should just give up and use Dragon's Breath for more logic, as opposed to the 100-300 meter accurate range of assault rifle, and the many hundreds of meters for serious rifle rounds.]

[wierd]

If I'm getting that correctly, it sounds like a recipe for incredible mind screw across the multiverse. If no-FTL universes can sometimes receive ships anyway, what's to stop a no-pol-FTL universe receiving a warship from a free-for-all universe, in flagrant violation of the compact, that was never sent? Then of course they can't send a diplomatic party quickly enough to do anything.

It would happen in only a very tiny percentage of possible universes, to the point of being statistically insignificant, but when it does happen, it would be a big deal, yes.

Likely, the ship arriving would realize very quickly that the nav computer was in error, and they arrived at an acausal universe, and it is not where they intended to be. Barring a very very very bizzare set of circumstances, even "evil universe" versions would want to get to the nearest 'sensible' universe, and not the 'crazy one' they just arrived in, especially if this is a political envoy.  They will want to jump again almost immediately, and after they get a correct navigational fix.  there is always the chance that they are just straight up sociopathic or are from a 'doomed' universe, and will want assylum in a "sane" universe where whatever calamity they are desperately fleeing from never happened, but those are again going to be very statistically unlikely. Good story material, but statistically unlikely, and a radical departure from the "normal."

Likely, the 'no politics' universe would deny such an assylum request, since it is a big pandora's box.

Basically, there are only two scenarios where a political allowed universe sends an unexpected ship into a no politics universe: 

An accident in navigation (likely to be corrected quickly when they realize they are in the wrong place)

They went there on purpose (and will likely be "directed" to leave. immediately.)

So, the potential for such a ship to suddenly arrive, even in a universe where FTL is never developed at all, is definately real. As a story teller, you would need a pretty compelling reason for such an "off probability curve" incursion though.

The converse is also true-- ships departing, but never arriving at destination.

[GiglameshDespair]

I had a thought today, and it probably sucks. What would the advantages and disadvantages be of a rotary shotgun. A minigun/rotary cannon arrangement which shoots shotgun shells and/or slugs?

There's no advantages to carrying a rotary shotgun as a small arm.

The advantage of lots of barrels allows a high firing rate and gives the barrels a bit of time to cool between shots. This helps prevent overheating. This isn't an issue with a weapon like a shotgun - it won't have enough cartridges in the magazine to overheat before it runs out of ammunition.
The fire rate, additionally, can be plenty high enough with a single barrel. If you look at real combat shotguns^{1 2 3}, they tend to have a lower fire rate than assault rifles - they hover around the 300rpm mark rather than the 700-950 rpm of the M4 carbine. A higher fire rate clearly isn't a priority.

The disadvantages are:
1 ) weight. Lots of barrels are really heavy. This isn't great for a close combat weapon. Combined with the weight of lots of shotgun shells, you'll find it'll be an exhausting weapon to carry around. A shotgun is a close range weapon - so it needs to be manoeuvrable. You could decrease weight by reducing barrel length, but that also decreases accuracy and power.
2 ) something has to power the rotation. While gas powered rotatary cannons do exist, generally they're electrically powered. If so, you've also got to lug around a battery as well. That ties into 1). If you want it to be gas powered, it's... debatable whether the
3 ) accuracy. The faster the fire rate, the harder it is to control the recoil.
4 ) maintenance. A rotarty cannon, by definition, has a lot of moving parts. If your gun is broke, it ain't a gun.

To sum: a huge amount of additional weight for no actual gain.

If you want it to be a crew served weapon, ala the XM214, you have to consider again the fact that shotguns are primarily short ranged weapons. A crew-served weapon is not ideal at short ranges. Even if you're shooting slugs, you won't match a machine gun. The weight issue still applies, as well, just to a lesser extent.
It'd be better just to stick to a machine gun. Tried and tested.

[wierd]

If you want a long range anti-personel round, what you want is an exploding canister filled with shot pellets.

The canister has good ballistics efficiency (Has the weight of all that lead shot inside it, and a good ballistics cross-section due to the shape of the canister), and thus can travel long distances without losing appreciable energy. When it approaches target, it explodes using either an inexpensive computerized detonator, or a simple time delay fuse-- rupturing the canister, and dispersing the shot pellets.

[Jimmy]

A.K.A: Artillery.

[Tack]

Speaking of rotary shotgun, can someone help me figure out cooling for a rotary canon designed to operate in vacuum?

As far as I can tell, on the macro scale we've got to either vent hot gasses/liquids which will be difficult to restock on, or sinking that heat into the internal heating of the plane- which is great for economy, but less great when during an extended firefight the cockpit keeps getting hotter and hotter.
On the micro- how the heck are you supposed to transfer heat efficiently enough from the rapidly-spinning barrels in order to prevent catastrophic failure during aforementioned extended firefight?

[Rolepgeek]

Barrel shroud that cools them all down simultaneously. Superconductors help.

[GiglameshDespair]

Speaking of rotary shotgun, can someone help me figure out cooling for a rotary canon designed to operate in vacuum?

As far as I can tell, on the macro scale we've got to either vent hot gasses/liquids which will be difficult to restock on, or sinking that heat into the internal heating of the plane- which is great for economy, but less great when during an extended firefight the cockpit keeps getting hotter and hotter.
On the micro- how the heck are you supposed to transfer heat efficiently enough from the rapidly-spinning barrels in order to prevent catastrophic failure during aforementioned extended firefight?

Liquid cooling, perhaps with liquid nitrogen or ammonia, as used on the ISS.

It's quite valid for your fight to be limited by the amount of heat you can disperse, just as you'd run out of ammunition.

[Dirst]

If you want a long range anti-personel round, what you want is an exploding canister filled with shot pellets.

The canister has good ballistics efficiency (Has the weight of all that lead shot inside it, and a good ballistics cross-section due to the shape of the canister), and thus can travel long distances without losing appreciable energy. When it approaches target, it explodes using either an inexpensive computerized detonator, or a simple time delay fuse-- rupturing the canister, and dispersing the shot pellets.

You mean the XM25?

[i2amroy]

By contrast, we would want to have a spherical chamber instead of a circular pool, and would want the standing wave to be produced eccentric to the ship's center of mass, so that the ship will have potential energy to move toward the created spacial depression. (the ship will try to "fall into" the standing wave, but as the chamber moves, the wave's focal point will move, so the ship never reaches it, instead continuing to slowly fall forward, picking up speed.)

I am sure somebody will point out how this is impossible, but I think it would work.

I think the big issue with this idea in space is that we need emitters at all points around the edge of the space that we wish to create our waves in in order for it to work. As such it could work great for things like moving ships through stationary highways in space and whatnot (gravity pulse travels along the highway every half hour or something similar) but it makes it fairly useless as an engine drive for pathfinding/trailblazing (or for entering any space you don't already control the edges of at near 100%). It would definitely be an awesome idea for a method of pseudo-wormgates for a civilization though.

[Tack]

Speaking of rotary shotgun, can someone help me figure out cooling for a rotary canon designed to operate in vacuum?

As far as I can tell, on the macro scale we've got to either vent hot gasses/liquids which will be difficult to restock on, or sinking that heat into the internal heating of the plane- which is great for economy, but less great when during an extended firefight the cockpit keeps getting hotter and hotter.
On the micro- how the heck are you supposed to transfer heat efficiently enough from the rapidly-spinning barrels in order to prevent catastrophic failure during aforementioned extended firefight?

Liquid cooling, perhaps with liquid nitrogen or ammonia, as used on the ISS.

It's quite valid for your fight to be limited by the amount of heat you can disperse, just as you'd run out of ammunition.

Barrel shroud that cools them all down simultaneously. Superconductors help.

But even then I run into difficulties trying to figure out how the liquid cooling, or even the heat, would move from spinny-barrel-bit to non-spinny-bit.

[Rolepgeek]

Liquid. That's how, Tack. Have liquid inside the barrel shroud. Or superconductive wire around the barrels and the centerline of the barrels rotary motion. A few wires connecting the two, and it leads back towards a heat sink where it can rotate in or something(possibly a partially liquid heatsink so that it can diffuse through faster/doesn't wear out the wires as quickly).

[GiglameshDespair]

The method exists.
Basically a static shroud around the rotating barrels that has the liquid inside to draw away the heat.

[Tack]

The method exists.
Basically a static shroud around the rotating barrels that has the liquid inside to draw away the heat.

Read through that whole thing and still barely understand
It looks like a simple fixed boom which sprays pressurised gas and coolant over the barrels as they spin. The coolant isn't a problem- just pack it with the ammo, I guess. Heck, it could actually make for a good countermeasure if the ship's magazine gets hit.
Not sure how efficient it would be but the "rolling heatsink" idea I had was probably more awful.
Plus it could compensate for the spin... Although I'm not sure about the kick of the gun.
I have no idea how guns kick in space.