Writing project questions

[Fraktal]

I have a few questions regarding an ongoing writing project of mine.

First. What would be a realistic crew count for a spaceship with no independent FTL capabilities? Specifically, in the current timeframe of the universe in question, humanity's FTL capabilities are limited to fixed gates with a travel speed of 99.187856c (roughly 0.8857 parsec per day), requiring weeks of travel time between inhabited systems. The gates utilize hyperspatial wormholes to chuck ships at each other; the targeting is not exact, but the gates are capable of pulling in wormholes passing in their general vicinity and opening a safe exit aperture. The range for doing so is sufficient that one gate per system is enough (and as of right now, the targeting is not accurate enough to pick between multiple gates in the same system anyway, that's part of a later upgrade).

However, the gates have a very low tolerance for gravity: if the gate is located too close to a gravity well like a planet, the gravity-induced curvature of space as described by general relativity pulls the exit aperture away from the gate (the gate pulls in the wormhole with an artificial version of the same effect, but at such close proximity, a planet yanks much harder than a gate) to the point where the wormhole either misses the gate and never opens an exit aperture, opens the aperture somewhere in interstellar space, or opens the exit aperture inside the planet with predictable results for the ship.

Because of this, gates are usually deployed far above or below the system ecliptic, though there is one loophole for this: L1 Lagrange points in two-body systems where the mass difference between the bodies in question is below a certain limit and there isn't a third, much more massive body nearby are stable enough for a gate to operate there. The Earth/Moon L1 is one such location (within tolerance and Jupiter is too far away to interfere) but if there isn't such a convenient spot available, ships have no choice but to spend weeks traveling on laser-ignition fusion rockets between the local worlds and the local gate on top of the weeks they already spent in FTL.

So then. With that kind of travel time, what should be the expected crew size for military vessels if we account for how much storage space would be available for provisions on the following size classes, also accounting for space taken up by ordinance (none are using energy weapons):

• Frigate-class: 96 m, AA and picket - 24 x AA autocannons, 1 x 90mm spinal coilgun
• Destroyer-class: 325 m, medium-to-long-range ship-to-ship and orbital fire support - 4 x gun turrets, 300 x cruise missiles in a broadside version of VLS, 1 x 155mm spinal coilgun
• Carrier-class: 743 m, force projection and taskgroup-level C&C - 32 x AA autocannons, hangar space for 30 fighters, 15 bombers and 20 transports (same chassis as a bomber)
• Battlecruiser-class: 968 m, taskgroup defense (that is, packing an assload of armor to park in front of smaller friendlies and literally take some for the team while said team is returning it with interest), strategic nuclear fire support - 4 x heavy turrets, 18 x medium turrets, 2 x 155mm spinal coilguns, classified number of nuclear-tipped cruise missiles

AI is a thing, but only on bigger ships and not good enough to fully automate ships. FTL communication is impossible because EM interference makes all ships blind and deaf beyond visual range while in the wormhole, so even courier ships are manned (and dreaded as a posting due to the sheer boredom).

For force organization, presume that one destroyer and four frigates counts as a task group, one battlecruiser, one carrier and two task groups count as a carrier group. 100+ km ranges are considered standoff because of projectile speeds; shootouts usually don't close to visual range unless a carrier is involved. Due to gates being the sole method of FTL (as of now) humans have, interstellar offensives tend to be very messy and costly because the incoming fleet is naturally chokepointed at the local gate, requiring them to come through very tightly packed to bring enough force to bear quickly enough to avoid being picked off one by one as they arrive.

And before you go "that's fucking pathetic", that's kinda the point: humanity is very new to this whole space warfare thing. The first time the fleet has to fight for real against a force with superior ships and far superior numbers, they suffer a catastrophic asskicking: the humans bring three quarters of their entire navy, slightly over a thousand ships not counting strike craft; the opposition brings a million-plus fleet, each individually superior to every human ship class, roll over the humans with barely any effort and strike a blow humanity doesn't recover from for millennia.


Second. Accounting for the above travel times, if the government suddenly started mass-relocation of people to offworld colonies to scatter humanity so that no single calamity can render them extinct, realistically how many they could relocate within about 15 years tops if they went from zero space infrastructure to interstellar with at least half a dozen settled systems within 23 years? As an added assistance, the government in question has no rivals aside from permanent insurgencies in the Middle East and Central Africa, isn't democratic enough to not resort to military intervention to crush attempted secessions and isn't naive enough to not have near-omnipotent political officers keeping the military in line. Would somewhere in the low eight-digit range too much to ask?

Note that if it weren't for this relocation program, humanity would've went extinct in the aforementioned asskicking, right then and there. Even so, they promptly degenerate into civil war and start killing each other despite their diminished numbers until they're too exhausted to fight and decide to call it off for now until some power consolidation can be had.

Also note that not a single settled planet has a breathable atmosphere or liquid surface water and only about 2 or 3 are even Goldilocks planets. The one planet that's closest to Earth in terms of habitability (similar climate and atmospheric pressure, 1.1g gravity, N-He-CO2 atmosphere, 52 hour rotation) is the most heavily populated and industrialized colony, recently started outlining plans for a space elevator and is under terraforming (icy asteroids from the local asteroid belt have been redirected at the planet to seed it with water and the lakes that have formed have been seeded with algae) but is not expected to be fully habitable for centuries, if not more. Another planet with water, oxygen and even intelligent native life is discovered later, but is uninhabitable to humans due to lethally high oxygen partial pressure and crushing gravity that requires a powered exoskeleton to even walk around in and is dangerously close to the maximum sustained gee tolerance of a human anyway.

[Elheru Aran]

Regarding crew sizes: I'm reminded of a line I saw in a Cracked article about life aboard a submarine. 'The equipment fits where it fits. You move'. That said, if you can do the math to calculate ship sizes, you can do the math to figure out how much crew you need. Try looking at modern wet-navy ships of the approximate size.

Also: If the other side has that much of a numeric disparity to your humans... how the hell did they not just wipe out your humans.

[U.P. Cinnabar]

Also bear in mind the trend in wet navies is to reduce crew sizes and automate where ever they can. Also, if you want a force projection capability(marines), that has to be factored in as well.

[Fraktal]

If the other side has that much of a numeric disparity to your humans... how the hell did they not just wipe out your humans.

That's what their invasion fleet was meant to do. It's just that the last time they had contact with humanity, humanity was still limited to Earth and had to resort to cutting off the bad guys' access to Earth to get away from them because if the bad guys could've brought in reinforcements, they would've steamrolled Earth in minutes (humanity was in very bad shape at the time). Now they came back because Earth's gate was sabotaged to let them in. Last time, their ROE was "kill all resistance, go Borg on the rest" but since humanity failed to get the message that resistance is futile and actually kicked them off Earth the first time around, that ROE has been updated to "full genocide, no surrender accepted". As I've stated elsewhere, these particular bad guys don't fuck around when it comes to competition.

Only, they haven't counted on two things. One, the relocation program. They don't know where humanity's colonies are and have limited FTL capabilities themselves (specifically, they can go from point A in one universe to point B in another nearly instantly, but not within the same universe; the humans partially got their own FTL off of theirs via modifying it, so the aliens could reverse-engineer and adapt it right back if they had a sample, but they can't because the humans rig the gates with nuclear scuttle charges as SOP to prevent capture), so they can't go look at random.

The other thing they hadn't counted on is that the human protagonists recently found and reactivated an ancient alien ship they found buried underground since its previous owners were rendered extinct by the same bad guys humanity is up against. And since the builders fought a full-scale galactic war of annihilation with the bad guys, the ship (a 78 km long, independently FTL-capable behemoth of a mobile shipyard/fortress) singlehandedly kicks back most of the invasion fleet. It's just that it arrived too late to actually stop the fleet from accomplishing its objective, is mostly inoperative due to being critically short on maintenance (it can self-repair if it has access to the materials and in fact has left Earth to seek out the wreck of one of its sister ships to cannibalize it) and is just one ship. It can't be everywhere at once, cannot self-multiply and is irreplaceable. Powerful, but not omnipotent by any means.

That, and the loss of that million-plus fleet wasn't even that big of a loss for the big guys because they can replace that kind of losses within weeks and have several orders of magnitude more. Even without a technological advantage, they can simply out-attrition everyone who tries to fight them. To them, humanity are not even bacteria in comparison. This is why the conflict against them is not even the main focus of the story because 1) humanity has other problems and battles to fight, 2) authorial fiat can only take repeated antagonist victories so far before the audience gets bored along the lines of "what's the point of this story, even?" and 3) the ONE other faction who could actually whoop THEIR asses are straight-up Clarkian folks who created the whole damn universe to begin with and literally anything they would do would be a massively unsatisfying deus ex machina.

This story is pretty much the antithesis of HFY: humanity sweat blood just trying to survive and pull some epic-tier shit in the process, but they're still so low in the universal food chain that they might as well not even exist. And when they get enough of a breather to actually explore the galaxy... they find that they're actually the local equivalent of a sci-fi elder race as far as galactic civilization goes!

So when battle-hardened humanity who have spent the past half a century fighting two extinction-level threats and found precious few allies in that time make first contact with a Grey-type race with a late-19th century tech level and the Greys are all awed and asking the visitors to enlighten them with their advanced society and morals... the humans are awkwardly shuffling in place and prodding each other to speak first because they have no idea how to handle a situation where they are the Vulcans/Bentusi/Asgard/Minbari/Protoss/insert-name-here other races are looking to for answers, as if they didn't have enough problems already with YET ANOTHER extinction-level threat (third now) approaching.


...sorry for the rant. I tend to go on rants when I can actually answer a question in detail.

[Sea Skimmer]

I have a few questions regarding an ongoing writing project of mine.

First. What would be a realistic crew count for a spaceship with no independent FTL capabilities? Specifically, in the current timeframe of the universe in question, humanity's FTL capabilities are limited to fixed gates with a travel speed of 99.187856c (roughly 0.8857 parsec per day), requiring weeks of travel time between inhabited systems. The gates utilize hyperspatial wormholes to chuck ships at each other; the targeting is not exact, but the gates are capable of pulling in wormholes passing in their general vicinity and opening a safe exit aperture. The range for doing so is sufficient that one gate per system is enough (and as of right now, the targeting is not accurate enough to pick between multiple gates in the same system anyway, that's part of a later upgrade).

A modern CVN has about 1 man per 200 tons of ship and ~15 men additionally per aircraft to service rapidly. Destroyers have more like 1 man per 25 tons of ship. If you want a rule of thumb, treating a space warship like it masses the same as it's volume displacement in water would get you a ballpark for a ship with limited armor.

The travel time between systems doesn't tell us much because how much ordnance you need to be effective depends on what and your doing and how often you can resupply from ammunition ships you brought along. Naval expeditions in real life lasted up to several years in the early modern period, but people brought along storeships to do it. A sailing man of war raiding the coast of Chile in 1590 probably only had 60 cannonballs per cannon on-board. That wasn't critical if you had a storeship per warship.

Because of this, gates are usually deployed far above or below the system ecliptic, though there is one loophole for this: L1 Lagrange points in two-body systems where the mass difference between the bodies in question is below a certain limit and there isn't a third, much more massive body nearby are stable enough for a gate to operate there. The Earth/Moon L1 is one such location (within tolerance and Jupiter is too far away to interfere) but if there isn't such a convenient spot available, ships have no choice but to spend weeks traveling on laser-ignition fusion rockets between the local worlds and the local gate on top of the weeks they already spent in FTL.

What that means if you won't have any kind of tactical surprise factor. The enemy literally has time to recall reservist personal from leave and launch them into orbit. On the other hand it's not enough time to seriously produce new weapons, unlike slower then light wars where that could be a major factor in system to system warfare. That favors the offense since preplanning is less likely to be wrong.

If we assume 4/6 weeks outbound in the home system, and 4/6 weeks inbound in the target systems were still well below the point that replacement crew should become a requirement. You could still spend months on the combat deployment. More or less in line with modern expectations.

So then. With that kind of travel time, what should be the expected crew size for military vessels if we account for how much storage space would be available for provisions on the following size classes, also accounting for space taken up by ordinance (none are using energy weapons):

See suggestion above and then consider the longer you expect to fight and more ammo you expect to fire from a given weapon the fewer people you need per ton of ship. Because plain storage doesn't require more people, but it does increase the mass of the ship. Aircraft carriers are ships designed for high endurance combat. Destroyers are designed around salvoing a large number of missiles quickly.

AI is a thing, but only on bigger ships and not good enough to fully automate ships. FTL communication is impossible because EM interference makes all ships blind and deaf beyond visual range while in the wormhole, so even courier ships are manned (and dreaded as a posting due to the sheer boredom).

That doesn't really follow that courier ships can't be unmanned. It's a drone carrying a message. The human instinct might be to deny the reliability of a robot, but in all reality a future tech robotic drone should be relatively easy to program to ensure total security of the messages. It can erase and self destruct them multiple times over using wholly independent sensors if need be. Carrying a human crew means humans can compromise the situation and they'll need significant accommodation to constantly sustain such boring duty.

Tactical command can suffice on STL communications if need be. An earth to the moon battle wouldn't be seriously hindered if you're limiting this to more or less realistic technology aside from the FTL, but stupid high interplanetary government levels of spending.

For force organization, presume that one destroyer and four frigates counts as a task group, one battlecruiser, one carrier and two task groups count as a carrier group. 100+ km ranges are considered standoff because of projectile speeds; shootouts usually don't close to visual range unless a carrier is involved.

Visual range? This is space. Visual range is potentially billions of light years. 100km isn't jack squat for optical target tracking, light travels at about 300,000km/s. Earth to the Moon is about 385,000km.

To put that in context world war battleships were having to compute target positions 30-120 seconds into the future depending on the actual firing range.

This isn't very important for crew sizes though. That's governed by how much equipment in the ship needs human attention. One would reckon that any major system like an engine, a power switching controller, a weapon, an aircraft, is going to need at least several people if it needs any people at all. A large number of missiles might be wooden rounds, while the loader and launcher mechanism per tube each requires multiple people to maintain but none to operate.

ue to gates being the sole method of FTL (as of now) humans have, interstellar offensives tend to be very messy and costly because the incoming fleet is naturally chokepointed at the local gate, requiring them to come through very tightly packed to bring enough force to bear quickly enough to avoid being picked off one by one as they arrive.

That seems like a scenario calling for a large number of nuclear warheads to be fired ahead of an invasion. Followed up by some kind of super protected blockship that's made of minimal 100ft thick concrete that can actually absorb near direct hits from nuclear weapons. Such attacks might have little in common with the mobile part of the space to space navy.

Second. Accounting for the above travel times, if the government suddenly started mass-relocation of people to off world colonies to scatter humanity so that no single calamity can render them extinct, realistically how many they could relocate within about 15 years tops if they went from zero space infrastructure to interstellar with at least half a dozen settled systems within 23 years?

Also note that not a single settled planet has a breathable atmosphere or liquid surface water and only about 2 or 3 are even Goldilocks planets. The one planet that's closest to Earth in terms of habitability (similar climate and atmospheric pressure, 1.1g gravity, N-He-CO2 atmosphere, 52 hour rotation) is the most heavily populated and industrialized colony, recently started outlining plans for a space elevator and is under terraforming (icy asteroids from the local asteroid belt have been redirected at the planet to seed it with water and the lakes that have formed have been seeded with algae) but is not expected to be fully habitable for centuries, if not more. Another planet with water, oxygen and even intelligent native life is discovered later, but is uninhabitable to humans due to lethally high oxygen partial pressure and crushing gravity that requires a powered exoskeleton to even walk around in and is dangerously close to the maximum sustained gee tolerance of a human anyway.

If you are trying to go from zero space to colonizing non habitable worlds in 23 years the main limitation is going to be how quickly you can launch large amounts of heavy equipment into orbit and thence onward to the gate. Moving the people alone won't be the limit. It will be getting bulldozers onto the far planet so you can start building tunnel habitats and solar farms on an industrial scale. Since this is less then hard sci fi that depends on how you have that aspect of technology work. You should expect a pretty non linear result on this, once you can get enough infastructure going on a colony to make concrete and plastic locally the amount of habitat you can build would skyrocket. Keep digging tunnels and lining them, and non habitable greenhouses on the surface.

[Sky Captain]

If independent FTL is not possible how the jump gates got to other systems in the first place ? If in system sublight travel still takes quite long then it seems sublight engine technology is not up to the task of relativistic flight to deliver jump gates to nearby star systems in reasonable time.

[Sea Skimmer]

I got the impression the gates work one way, so you could launch a ship to another system, but it couldn't return without bringing along a gate to assemble on the far side. So opening up a new system to exploration is a big risk and high cost as you won't know what's on the far side until you make that resource commitment. Or else chuck a scouting drone on a one way mission and wait decades or centuries for a slower then light communication back.

[Formless]

Actually, I remember one trick mentioned on Atomic Rockets that can solve the issue of getting wormholes and other Warp Gate style FTL devices/objects to other systems: In theory, every time you send something through a wormhole the momentum of the wormhole changes. So if you shoot thrust through the wormhole, the end of the wormhole that thrust comes out of will move. This allows you to shoot wormholes to other parts of the galaxy by simply pointing a laser or ion engine through it. One end of the wormhole stays put (although I'm not sure if this is because only one end of the anomaly actually changes momentum or simply because you can hold it down), while the other goes wherever you want it, and you don't need an external spaceship to carry it to its destination. The wormhole is the spaceship. To slow it down, simply move the engine so its pointing in the opposite direction, and it will come out the other way on the other end of the wormhole as well.

And because non-wormhole based warpgate technologies are essentially handwave, you can handwave them to have this same property.

[Fraktal]

^ Interesting idea.

If independent FTL is not possible how the jump gates got to other systems in the first place ? If in system sublight travel still takes quite long then it seems sublight engine technology is not up to the task of relativistic flight to deliver jump gates to nearby star systems in reasonable time.

I got the impression the gates work one way, so you could launch a ship to another system, but it couldn't return without bringing along a gate to assemble on the far side. So opening up a new system to exploration is a big risk and high cost as you won't know what's on the far side until you make that resource commitment. Or else chuck a scouting drone on a one way mission and wait decades or centuries for a slower then light communication back.

Humanity has access to a different form of FTL, basically point-to-point teleportation, that's nearly instant, but beyond a few hundred thousand kilometers, the process produces so much exotic radiation that attempting to send living tissue across interstellar distances will instantly kill the traveler on arrival, to say nothing of the colossal energy requirements and the accuracy issues (one character explicitly mentions that writing a note down onto a piece of paper and teleporting it to another star system for FTL communication would drop it out anywhere within a several-hundred-to-several-thousand AU radius and since space is big and empty, making actually finding something that small an exercise in finding a needle in a haystack). So the first step in colonizing a new system is using the same exoplanet discovery methods we have access to in real life to scout for a potential destination. The gates are constructed in a facility orbiting the Sun within Mercury's orbit, most of the mass of which is composed of capacitors and solar cells to accumulate the energy to deploy the gates to their destination. Each gate deployment requires around a full year's worth of solar power, even at this proximity. Due to the waste radiation issue, the gates are deployed unmanned and upon arrival, spend the next couple of months moving to their new position before opening a wormhole back to Earth and sending through a message pod broadcasting a "mission complete" comm burst to let the humans know that the gate is in position and ready to receive a permanent crew.

It doesn't always work out. There's one system with a planet that looked good on the simulations but when they actually deployed a gate and went there, the planet turned out to be a high-gravity world so close to the local star that it was tidally locked (and the star's output was higher than projected, making the day side a radiation hazard), so the colony was set up on the moon of a neighboring gas giant and the government recouped losses by setting up a penal colony space station at the very end of the planet's umbra that uses giant solar sails extending into the penumbra to stationkeep above the planet's night side while the inmates work the foundries fed from the mines on the planet's surface.

For the aforementioned alien-built mothership, it can FTL on its own just fine and can even fling other ships into FTL on a one-way jump, which makes it a gamechanger as far as the rest of humanity is concerned because it means it can show up literally anywhere, at any time, with zero warning. It's just that its FTL drive is the size of a small city and suffers from an accuracy issue: without a fixed exit point, the further and faster it tries to go in one jump, the navigational calculations become exponentially more complex until even its AI can only guess where it's going to come back out. Basically, if you try to jump beyond a few tens of lightyears in one go, you can come out anywhere within a few lightyears of the target and will have to make several corrective shortjumps to arrive to where you were trying to go. The human faction controlling the ship does eventually reverse-engineer the drive into two smaller versions (a short-range, limited-functionality version for a 2.5 km dreadnought and a long-range, fully functional version bolted onto an O'Neill cylinder to act as a generation ship), but they're still glitchy and the faction doesn't share their tech with anyone.

For comparison, while everyone else have ships with laser-ignition fusion rockets, artificial-gravity-confinement nuclear fusion reactors and a mix of kinetic cannons, missiles and the occasional particle beam cannon, the faction with the alien ship have ultra-efficient ion drives with ramscoops, hyperspace ZPE taps and the same array of weapons plus giant fuckoff antimatter-pumped lasers (which was reverse-engineered off the alien ship's spinal cannon). They do use the knowledge they gained from doing so to give the rest of humanity an improved gate design with a much higher gravity tolerance (now high planetary orbit is enough) and accuracy (multiple gates per system are now possible, allowing rapid interplanetary travel), but they keep the best stuff for themselves, for which they catch quite a bit of flak from the others.

The exact rate of FTL development is still a bit fuzzy. First contact with the Borg-wannabe aliens whose tech goes into the gates is in 1997, gate-based FTL is invented sometime in the late 2020s, the big alien ship is found in 2042, reverse-engineered versions of its FTL drive are completed in 2068, and a cruiser dating to the 3000s dug out of an asteroid circa 10000 has independent FTL despite its comparatively small size (barely 500 m for the main hull, ~800 m total). Development is quick at first because humanity already has the theoretical physics background to understand how it works, but slows down afterwards as construction material limitations/imperfections come into play (case in point, the aforementioned ZPE tap: they run on a significantly lower output than what the math says they're capable of because 40% theoretical maximum output is the absolute maximum the regulator can handle before it can't throttle the power flow back down anymore and the whole thing goes off like a nuke) and the humans start running out of stuff to copy and adapt.

[Fraktal]

A new question came to me just now. For a warship without artificial gravity that doesn't have to worry about delta-V, realistically how strong forward acceleration I can assume before it starts inhibiting crew mobility too much?

I'm asking because I just found out that even with 1g acceleration, it could cross the Earth-Sun distance within slightly less than three days and Sun-Uranus in slightly over three weeks if we assume it starts decelerating halfway with the same 1g and we don't factor in gravity or relative speeds between the target planets. That's a lot more than what I was planning on (I was planning on Earth-Mars in weeks instead of months), but that's the smaller matter. The bigger matter is that if the ship is micrograv and doesn't have inertial dampening, 1g would make it rather difficult for damage control crews to get to the front while the ship is running away from a battle it can't win.

So... what's the best solution? Nerf the acceleration to the point where the crew can use wall ladders, throw in inertial dampening (I'd prefer not to and the source verse has no explicit example, but I can extrapolate it from existing tech) or just stack the decks front-to-aft instead of top-to-keel?

[Formless]

Uh, 1 G is exactly the same gravity as on Earth, so I'm not sure what the problem is for damage control crews if you are accelerating that fast. Keep in mind that without artificial gravity (or arguably even with artificial gravity) the ship would most logically be designed like a skyscraper (The Expanse is one of the few shows that follows this logic), with the engines blow the crew's feet. That way "down" is opposite the direction of travel whenever the engines are accelerating the ship. At 1 G, damage control crews should find ladders and staircases to be a perfectly adequate solution for getting to whichever deck they need to be to fix stuff. Any less acceleration and its even less of an issue because falling down won't hurt as much.

However, as far as travel times go the ship's maximum theoretical acceleration won't necessarily be the only consideration. Fuel capacity and efficiency issues will make simple Brachistochrone transfer missions (i.e. "burn the rocket all the way 'till we're halfway there, flip, burn off all our acceleration, do this in a straight line") infeasible and uneconomic for many civilizations. In many cases you are going to make as few burns as you need, and the engines might actually be off for a lot of the trip, or accelerating much less than they theoretically could.

[Fraktal]

Uh, 1 G is exactly the same gravity as on Earth

I know. That's why I said that value.

so I'm not sure what the problem is for damage control crews if you are accelerating that fast.

Hauling DC equipment up several hundred meters on ladders in a timely manner. And that's if there are ladders in the first place. There are genetically engineered superhumans in the setting, but very few (six) at this point.

Keep in mind that without artificial gravity (or arguably even with artificial gravity) the ship would most logically be designed like a skyscraper (The Expanse is one of the few shows that follows this logic), with the engines blow the crew's feet. That way "down" is opposite the direction of travel whenever the engines are accelerating the ship. At 1 G, damage control crews should find ladders and staircases to be a perfectly adequate solution for getting to whichever deck they need to be to fix stuff. Any less acceleration and its even less of an issue because falling down won't hurt as much.

Problem is, the same ship is designed for atmospheric operation too. So if the decks are stacked front-to-end, landing on a planet means gravity is 90° offset from the floor. Designing living quarters to take that into account with square-shaped doors and rotating furniture is one thing, but rotating the entire CIC (a hollow sphere with panoramic screen walls and the crew stations being held up by platforms) would be quite mechanically complex.

However, as far as travel times go the ship's maximum theoretical acceleration won't necessarily be the only consideration. Fuel capacity and efficiency issues will make simple Brachistochrone transfer missions (i.e. "burn the rocket all the way 'till we're halfway there, flip, burn off all our acceleration, do this in a straight line") infeasible and uneconomic for many civilizations. In many cases you are going to make as few burns as you need, and the engines might actually be off for a lot of the trip, or accelerating much less than they theoretically could.

Which is why I explicitly stated that delta-V is not an issue. The ship runs on very high-efficiency ion drives mated to a particle accelerator and a ramscoop that can use anything from planetary atmosphere to solar wind as reaction mass, so the limiting factor isn't fuel, but power (and heat). It's already a power hog to begin with (the ship had to squeeze in multiple reactors) but the thinner the ambient medium, the less energy-efficient it becomes because less reaction mass means higher specific impulse to maintain thrust, which means pushing the accelerators harder to increase exhaust velocity. There's a point where you just can't push them any harder without equipment failure and no way to fly. Interstellar deep space is already pushing it and extragalactic space is just straight-up no-go because there simply isn't enough ambient gas to get any meaningful amount of thrust out of it.

However, since higher ambient density means higher efficiency, the ship can reverse-aerobrake by dipping into an upper atmosphere to get an extra kick that more than offsets the speed it lost from air resistance, with minimal energy expenditure. So orbital maneuvers are still a thing.

For how much power it uses, the ship can use the Aeon drive during combat (which results in frankly ludicrous agility for even something half its size; in fact, the ship's superstructure is segmented like a spinal column to flex under high-gee maneuvers because a rigid frame would snap in half during flank speed combat maneuvers) but the output has to be dialed back to keep the weapons and armor plating operational and if main power goes due to battle damage, the drive is the first to go despite the ship's power systems having quintuple redundancy (main, primary backup, secondary backup, tertiary backup and emergency power; the Aeon drive can only run off the main while armor plating and beam weaponry can run off the primary backup, kinetic weaponry and sensors can run off the secondary and conventional propulsion can run off the tertiary).

[Formless]

so I'm not sure what the problem is for damage control crews if you are accelerating that fast.

Hauling DC equipment up several hundred meters on ladders in a timely manner. And that's if there are ladders in the first place. There are genetically engineered superhumans in the setting, but very few (six) at this point.

First, I'm no military expert, but I'm pretty sure damage control can be done a lot more efficiently than that. Having damage control crews come from one or two centralized areas and hauling all of their equipment around the ship is a bad idea. Instead, there should be multiple damage control stations with an appropriate number of crewmen spread across all decks and they should have appropriate gear for fixing whatever is on that particular deck. That minimizes the need to haul equipment long distances and improves response times for the crews. Second, some systems that are particularly important might actually have the tools to fix them in the vicinity of the system or machine, since that tool might only have one use it doesn't need to be stored at a damage control station. Much like how kitchens generally have fire extinguishers (or should have them). Thirdly, human damage control officers may not even be desirable, at least for some tasks. Or at least, those officers may not need to show up in person to do repairs when they could use telepresence technology instead. Nasa already has robonauts to help with maintenance on the outside of the ISS, and if your ship has a nuclear reactor or fission/fusion engines (which it would need to pull 1G consistently) then it will likewise have to have robotic damage control systems for fixing anything in those areas of the ship that is exposed to radiation. On some realistic designs the livable part of the ship is actually one of the smallest parts, unlike boats and airplanes we currently have.

Problem is, the same ship is designed for atmospheric operation too. So if the decks are stacked front-to-end, landing on a planet means gravity is 90° offset from the floor. Designing living quarters to take that into account with square-shaped doors and rotating furniture is one thing, but rotating the entire CIC (a hollow sphere with panoramic screen walls and the crew stations being held up by platforms) would be quite mechanically complex.

Oh, no no no no no no no. No. Any spacecraft small enough to enter an atmosphere will not be big enough to mount a fusion or fission engine needed for fast interplanetary flight, and that's just the first of a number of engineering nightmares that happen when you try and make a spaceship also function as an aircraft. Don't bother crossing the streams on this one: its like trying to make an airplane double as a submarine. The environments they are meant to operate in are simply too different to make it work in Hard SF.

The best alternative IMO is to simply give the ship parasite craft that are specifically meant for landing on a planet or deploying in the atmosphere. The ship itself should ideally always stay in orbit, much like ships in Star Trek do (Voyager notwithstanding). IF the ship needs to come into the atmosphere, its best to just land it because it will again be too big and probably heavy to make atmospheric missions as effectively as a properly built airplane or helicopter. Aerodynamics will always favor the purpose built vehicle, and modern aircraft are literally built like aluminium shells to minimize weight. That design does not work so well in space, where penetrating radiation is an issue for the crew. For those spacecraft that do land, it is possibly to land them on their engines like a rocket pointing up. That way you never have to worry about the floor changing direction, unless you have some sort of centrifugal method of generating false gravity.

No matter what you do, the ship's crew will experience "down" as being relative to the direction of acceleration, if there is one. This is a basic principle of Einstein's relativity, and the only way to get ships with floor layouts that look like the Millenium Falcon or the USS Enterprise where the floor is 90 degrees to the direction of travel is to break the rules and introduce magical gravity technology and Inertial Dampeners. If you go that rout the whole point is rendered moot. Besides, designing the ship's interior so that "down" can rotate 90 degrees depending on context is already a thing that's been done. Atomic Rockets has an entire page about centrifugal gravity setups that do have to deal with this kind of thing.

Which is why I explicitly stated that delta-V is not an issue. The ship runs on very high-efficiency ion drives mated to a particle accelerator and a ramscoop that can use anything from planetary atmosphere to solar wind as reaction mass, so the limiting factor isn't fuel, but power (and heat). It's already a power hog to begin with (the ship had to squeeze in multiple reactors) but the thinner the ambient medium, the less energy-efficient it becomes because less reaction mass means higher specific impulse to maintain thrust, which means pushing the accelerators harder to increase exhaust velocity. There's a point where you just can't push them any harder without equipment failure and no way to fly. Interstellar deep space is already pushing it and extragalactic space is just straight-up no-go because there simply isn't enough ambient gas to get any meaningful amount of thrust out of it.

However, since higher ambient density means higher efficiency, the ship can reverse-aerobrake by dipping into an upper atmosphere to get an extra kick that more than offsets the speed it lost from air resistance, with minimal energy expenditure. So orbital maneuvers are still a thing.

FYI that extra kick will most likely turn you into a disintegrating fireball like the one that blew up over Chelyabinsk. Aerobraking sounds like a suicidal idea at the speeds spacecraft travel at. A better idea is to remember that solar wind has inertia and that whenever you scoop it up you slow the ship down-- or more accurately, your scoop doubles as a kind of solar sail, which can be used for braking when close enough to a star. In spirit it is similar to slowing down in an atmosphere, but again I repeat that you should not try to fit a square peg into a round hole by having an interplanetary spacecraft perform atmospheric maneuvers like an aircraft. It will make for a ship that is neither a good aircraft nor an optimal spacecraft.

For how much power it uses, the ship can use the Aeon drive during combat (which results in frankly ludicrous agility for even something half its size; in fact, the ship's superstructure is segmented like a spinal column to flex under high-gee maneuvers because a rigid frame would snap in half during flank speed combat maneuvers) but the output has to be dialed back to keep the weapons and armor plating operational and if main power goes due to battle damage, the drive is the first to go despite the ship's power systems having quintuple redundancy (main, primary backup, secondary backup, tertiary backup and emergency power; the Aeon drive can only run off the main while armor plating and beam weaponry can run off the primary backup, kinetic weaponry and sensors can run off the secondary and conventional propulsion can run off the tertiary).

Why would the output of the engines ever interact with the effectiveness of the armor of all things? The weapons I can see, but armor is normally a passive architectural element. On modern attack helicopters, instead of armor they just make every structural element thicker than on a civilian vehicle. Sea Skimmer has often suggested simply using the ship's water tanks or fuel tanks or any other bulk containers that are necessarily part of the ship as a form of armor, especially against radiation. Yes, I know you used the words "armor plating" but its not like there is drag in space that could tear armor plates off when you try to go fast. The only other explanation I can think of is if you are using "spinning" armor, wherein spaced armor is spun up around the hull thus minimizing the risk of bullets going through the same hole twice. But I don't favor those armor schemes anyway. Too complicated to be worth it.

[Fraktal]

Oh, no no no no no no no. No. Any spacecraft small enough to enter an atmosphere will not be big enough to mount a fusion or fission engine needed for fast interplanetary flight, and that's just the first of a number of engineering nightmares that happen when you try and make a spaceship also function as an aircraft. Don't bother crossing the streams on this one: its like trying to make an airplane double as a submarine. The environments they are meant to operate in are simply too different to make it work in Hard SF.

Clarification. In an above post, I mentioned a 968-meter battlecruiser class. That one predates this ship and it very explicitly cannot enter atmosphere because it doesn't have the thrust-to-weight ratio for even VTOL, much less actually getting back up into space. I already got that down. The similarly earlier 743-meter Nexus-class carrier can VTOL, soft-land on water with extreme care and very slowly SSTO, but that's it.

The Netzach-class, the one we're talking about now, can VTOL, provide close air support, slug it out with stuff of similar size and can SSTO in minutes. It's NOT going to dogfight or supercruise because it's not exactly aerodynamic (the best way I can describe it is a Y-shape) and would fall right out of the sky if it tried to roll but in the very upper atmosphere, it's agile enough that at point in the story, it would dodge incoming fire from low orbit during aerobraking (and I mean real aerobraking, not aero-accelerating: they need to get to a moon in a hurry but the planet is in the way and there's an enemy fleet in orbit they don't have the time to pick a fight with, so they skip through the atmosphere to decelerate so as to not overshoot the moon and zip past the fleet low enough to not get hit; any lower and they disintegrate from hitting air at that speed, any higher and the enemy fire's travel time will be too short to evade and getting holed during reentry even once means they're DEAD). Fortunately, their helmswoman is competent enough to pull it off and their captain just that audacious to try it despite knowing full well how insane the very idea of combat maneuvering in the middle of reentry is. And predictably, the entire rest of the bridge crew are screaming in abject terror the whole time.

Enemy fire ends up not being as heavy as they expected because the enemy is too busy going "...oh, you gotta be fucking with me, is this shit for real?! What kind of suicidal morons are those people?!" to actually try picking them off seriously. Which kinda serves as part of a repeating motif to prove a point that no matter what the numbers say, as long as the human element is in play psychological warfare can always flip the table. Because when a screaming lunatic at the controls of a thousand-plus tons of mecha-sized cyborg is coming at you at supersonic speeds to rip out your cockpit and bite it in half after having singlehandedly massacred your entire unit... you're kinda too busy shitting your g-suit to operate your equipment effectively, and not just because the other guy somehow isn't dead from the 70+ gees he just pulled right in front of you with that charge.

Why would the output of the engines ever interact with the effectiveness of the armor of all things? The weapons I can see, but armor is normally a passive architectural element. On modern attack helicopters, instead of armor they just make every structural element thicker than on a civilian vehicle. Sea Skimmer has often suggested simply using the ship's water tanks or fuel tanks or any other bulk containers that are necessarily part of the ship as a form of armor, especially against radiation. Yes, I know you used the words "armor plating" but its not like there is drag in space that could tear armor plates off when you try to go fast. The only other explanation I can think of is if you are using "spinning" armor, wherein spaced armor is spun up around the hull thus minimizing the risk of bullets going through the same hole twice. But I don't favor those armor schemes anyway. Too complicated to be worth it.

The ship can magnetize some of its outer hull plating as a countermeasure against negatively-charged particle beams. Against kinetic projectiles, lasers, plasma and neutral particle beams, it won't do squat. Against a beam composed of negatively-charged particles (which is every particle beam weapon used by humanity), the hull acts like the electromagnetic equivalent of shaped armor: it won't stop a head-on blow but if the shot comes in at a shallow enough angle, the electromagnetic repulsion will force it away from the hull. Thing is, these beams rely on kinetic energy rather than heat transfer to deliver damage (translation: pencil-thin beam with superior armor penetration but unless it hits something vital, it will just overpenetrate with minimal internal damage most of the time; extremely deadly in the hands of a sniper who knows where to shoot), so even at a near-perpendicular angle, forcing the beam back requires a very strong magnetic field that takes a lot of power. And of course, if someone were to try and shoot the magnetized plate with a positively-charged particle beam, it would attract the beam instead of repelling it and turn near-misses into definite hits.

It's a really crude and buggy mechanism, but it's the closest thing to shields at this timeframe and is the only defense against particle beam weapons other than not getting hit or staying out of range (human beam weapons use tauons, which decay in a split second and are therefore range-limited) because no matter how much CIWS you pack, be it bullets, lasers or interceptor missiles, you can't hardkill subatomic particles coming in at relativistic speeds (since the tauon's short half-life means you need really high muzzle velocity to actually get a useful range out of it).