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At some point in the far future, humankind has sufficiently advanced to construct spacecraft for warfare, ie. space navies. The smallest of these crafts are comparable in size to contemporary fighter and attack aircraft, and are used as such. The largest of them, meanwhile, dwarf contemporary supertankers, and take on the roles of massive battleships, supply transports, or command centers.

The superpowers construct carriers to house, transport and launch their fighter spacecraft (or space fighters), much like contemporary aircraft carriers. Since space fighters require no lift to launch, they could be stored in individually designated pods, chambers or hangars, and a carrier could launch - and recover - its entire compliment of fighters simultaneously.

However, no matter the builders or the sizes of these carriers, all of them use one long, flat, exposed flight deck, combined with multiple elevators, to launch and recover their fighters, almost exactly like contemporary seafaring aircraft carriers.

What would be the reason to build spacecraft carriers this way, ie. in the image of contemporary aircraft carriers, instead of building corn-like carriers where each "kernel" houses a fighter, and could all be launched or recovered simultaneously?

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    $\begingroup$ Reminder to close-voters: The problem cannot be fixed if the OP is not made aware of it. That being said, I don't see a problem here; vehicle design decisions are a part of worldbuilding. $\endgroup$ – Frostfyre Sep 22 '17 at 19:01
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    $\begingroup$ Asking "reason" seems to be a trigger word for closing for opinion-based or too broad, however I see this is not a problem for this question: the answer can be judged by reasonableness and plausibility. $\endgroup$ – Vylix Sep 22 '17 at 19:19
  • $\begingroup$ When in doubt, ask TV Tropes: Rule Of Cool! $\endgroup$ – RonJohn Sep 23 '17 at 0:23
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    $\begingroup$ There is no actual reason that a spacecraft carrier should look look an aircraft carrier, and the sorts of justifications and handwaving to make this happen really detract from the "storytelling" aspect, you have to explain why non optimal solutions would be sought. A "spacecraft carrier" would resemble the corncob model, or perhaps a VL missile cell open at both ends to ships can enter and exit. Space is not an ocean and solutions have to be designed for the specific environment. $\endgroup$ – Thucydides Sep 23 '17 at 1:01
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    $\begingroup$ Trouble is, space fighters make no sense anyway. On a planet all velocities are relative to ground or air, and maintaining a high velocity relative to either takes a lot of energy. In space its changing your velocity that is expensive. Once you have matched velocity near enough to land or fight, matching it precisely for touchdown is trivial. Aircraft have a minimum flying speed, so need to touchdown first and decelerate second. Spacecraft don't need to do that. $\endgroup$ – Paul Johnson Sep 23 '17 at 13:31

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One possibility would be to have the "deck" work as a rail/coil gun, accelerating the launched ships.

The longer the rail gun, the higher the survivable relative top speed. A corncob sized accelerator trying to push the fighter to the same speed would end up being occupied by a think film of meat paste.

That would give the smaller ships a higher initial speed and give them a higher initial survival chance. This assumes slow/armored carrier and light fragile fighter that uses size and speed for defense.

The smaller craft would also have less storage for fuel/energy. The speed boost would allow the carrier to bear the cost of the initial acceleration.

Or, maybe they just happened to convert an old Japanese carrier instead of a battleship....

Edit:

Another reason: the carrier presents a smaller profile to the enemy if it presents its narrow end. A corn cob design is either going to have the fighters launch with no acceleration boost or will need to face broadside to the enemy.

Also: Might as well put wings on the tiger... ...put a spinal mount laser on it and you have a weapon pointing toward the target of the fighters.

You can also use that launch system to throw out missiles and a very high initial relative velocity (pull the safeties off and zoom!).

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  • $\begingroup$ I am quite liking this answer, namely the 1) railgun catapult idea and 2) maintaining the smaller frontal profile while still launching fighters towards the enemy. $\endgroup$ – user42997 Sep 22 '17 at 19:29
  • $\begingroup$ @user42997, if you ruin the profile by having the rail guns be a structure that stands up from the deck surface, you can use them to "catch" the fighters and decrease their fuel usage or speed vulnerability. Maybe only pop up the above deck rails for catching. That keeps them safely tucked away unless you are catching returning craft. $\endgroup$ – ShadoCat Sep 22 '17 at 19:56
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    $\begingroup$ That means a "carrier" has three essential modules: long rail-gun rifle; two flat-sheet metal radiators either side; and a container section, for crew and life support, and for ships that will be fired out of the railgun. Looking like a modern-day aircraft carrier will give all these things. $\endgroup$ – Dewi Morgan Sep 22 '17 at 20:38
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    $\begingroup$ I don't see how this set up would lead to "one long, flat, exposed flight deck." Why not have a long cylindrical carrier with flight decks all of the way around the circumference? Unless there is no strategic advantage to launching/landing multiple fighters at once. $\endgroup$ – Lex Sep 22 '17 at 20:38
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    $\begingroup$ @DewiMorgan, I don't think that cooling will be too big of a problem. you are dealing with the acceleration limits of a human. With that limit, the only way of accelerating them more is to lengthen the launcher. Though, I haven't thought about machine gunning the fighters out (more like breach load, double barrel). I was thinking of 4+ rails with load times for each set of fighters. Though the thought of seeing a "fighter clip" hanging out of the bottom of the carrier gives me the giggles. Then there's belt fed carriers.... I wanna see that anime. $\endgroup$ – ShadoCat Sep 22 '17 at 23:14
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To protect the hangars, and other portions of the ship, from the small craft themselves.

Flight decks are largely giant slabs of armor with equipment on top. One of the things this does is protects the ship from errant landings.

With a modern carrier, the small craft can come in damaged or with engine problems or other things. There are numerous examples of aircraft landing poorly and smacking into the carrier's flight deck, but aside from the flames and other associated issues, the ship itself is largely undamaged. Clean up the debris and you can start functioning again.

With a spacecraft, this could be even more important. You want landing areas to be different than the work areas for the vehicles in any case, but when you have potentially damaged craft and pilots trying to land, you really don't want to have them trying to fly through a door or other relatively small opening. A great big flight deck can let them land or dock a lot easier because it's a much larger target. There can be equipment on the flight deck to launch and recover craft easier, but it also serves to make the craft significantly easier to recover - Which means they can take more damage and still be saved. It helps your pilots survive, and it helps the ship survive. A craft hitting a hangar door can take the entire hangar out of commission - Annoying if it's a shuttle bay, but if the shuttle bay hangar on a battleship is taken out, it's just an annoyance. If one of the launch hangars on a carrier is taken out, it can potentially cripple the entire ship's fighting capabilities until it is repaired.

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    $\begingroup$ "If one of the launch hangars on a carrier is taken out, it can potentially cripple the entire ship's fighting capabilities until it is repaired." Not to mention endangering the lives of any pilots who are still in flight and might need to land in that hangar when they return. $\endgroup$ – Dave Sherohman Sep 23 '17 at 8:29
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    $\begingroup$ @DaveSherohman indeed, in the navy, closing the landing deck may mean scrapping the aircraft, unless you think you can launch enough tankers to keep them flying long enough to reopen the deck, if you are wrong, you lose the tankers too. $\endgroup$ – Harper - Reinstate Monica Sep 23 '17 at 21:44
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    $\begingroup$ Having a hangar bay taken out might not be just an annoyance, the bay doors are likely heavily armored and the inside likely less so. Enemy ace pilots might just get a lucky hit in through the exhaust-vent. Ehm. Jammed hangar bay door, I mean. $\endgroup$ – Erik Sep 24 '17 at 15:17
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Solutions have to reflect the environment they are to operate in, so I am going to say there is no reason to make a ship which resembles an aircraft carrier in space. Consider the USS Macon and Akron. These were explicitly aircraft carriers, yet have no resemblance to oceanic aircraft carriers, since they operate in a different environment.

enter image description here

USS Macon ZRS-5. No flat decks here

I won't go into the argument that space fighters are a non sequitur since they operate in the same medium as the other spacecraft, but lets look at some other issues:

  • Spacecraft can come at you from any direction. Since space is both vast and 3 dimensional, the idea that you will majestically steam head on towards the enemy isn't going happen. They will follow orbital paths or direct trajectories, hide outside the plane of the ecliptic or maybe hiding inside an asteroid. A carrier needs to be able to react by rapidly launching sorties of fighters in any direction. A "corncob" or something resembling a sea urchin could point coilguns in many different directions and sortie multiple fighters at once.

enter image description here

Sea Urchin as inspiration for a carrier

  • To cover large volumes of space, you need to sortie multiple craft at once. This means firing volleys of missiles or launching waves of fighters in quick succession. Of course, lots of fighters being launched in quick succession mean you have to recover them quickly as well. A carrier might resemble something like a multiple rocket launcher open at both ends so fighters can be launched and recovered in large numbers. There is no particular reason they all have to be facing "front", you could conceivably have 1/2 the fighters facing forward and the other facing aft in the launch tubes, providing more flexibility when planning and launching sorties.

enter image description here

A WWII German design. If you imagine the launch tubes mounted on a turntable like this on the ship, you have a fairly flexible design

So frankly, the amount of handwaving you'll need to do to make a spacecraft carrier look like a modern oceanic "flattop" is going to detract from your story, and probably induce strange anomalies in your plot as the spacecraft crews need to work around the awkward design which isn't suitable for space combat.

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  • $\begingroup$ I was wondering if they really built that airship and apparently they did, with it's 5 biplane "parasite aircraft". $\endgroup$ – Xen2050 Sep 23 '17 at 9:55
  • $\begingroup$ Interesting story about it's loss, being damaged the year before in turbulence, not fully repaired & again damaged in a storm. Especially interesting is that even when "enough helium was vented to cancel the lift, reaching an altitude of 4,850 ft (1,480 m). It took 20 minutes to descend and, settling gently into the sea, the Macon sank off Monterey Bay." "Only two crew members were lost... jumped ship while still too high above the ocean surface to survive the fall and... drowned while swimming back into the wreckage to try to retrieve personal belongings." Sounds pretty safe for a crash $\endgroup$ – Xen2050 Sep 23 '17 at 9:56
  • $\begingroup$ The objection of the 3d space don't really make sense IMHO, also the actual aircraft carriers have this problem, if only 2D. I suppose that once you launch your fighters they can turn where they want. After all, also the modern aircraft carriers today try to launch the plane going against the wind (more common in the WWII than today I suppose) instead of going against the enemy, to help the fighters to take off. $\endgroup$ – Gianluca Sep 28 '17 at 7:20
  • $\begingroup$ Aircraft carriers are built to interface with two different fluid environments, which explains their shape and layout. The airship carrier referenced only operated in one fluid environment, so was totally different. Spacecraft operate in a much different environment, there is no fluid media to work against to turn, so changing direction is difficult and fuel intensive for spacecraft. Launching directly towards a target is needed to save fuel or reaction mass in space. $\endgroup$ – Thucydides Sep 28 '17 at 16:26
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Here is another reason to keep the traditional carrier like design. Have your carrier be able to operate both in and out of the atmosphere.

Why would you want to do this? One reason would be the ability to project power effectively while planetside. Planets are going to be the primary place where the most resources are. The best way to take and control an area is to get boots, literally, on the ground.

Have your capital ship be able to get down to the ocean of the target planet so that smaller boats can get boots on the ground. Have attack aircraft launch from the carrier in order to provide support for ground forces that were delivered by various means. For those craft to return, while in atmosphere, the long flat deck is more practical. If those small craft can also serve as space fighters, that's a major bonus. When the small craft are in atmosphere, they will need to be aerodynamic in order to function efficiently. You might think that if the fighter support craft are launched directly from orbit, keep in mind that it will take time and a ton of energy to get them back into orbit. Much easier to do it from within the atmosphere.

A very large capital ship like this could almost be thought of as a self sufficient military colony, able to go from planet to planet and tame the surrounding area. It can operate both in the vastness of space and in atmosphere.

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  • $\begingroup$ +1 "Landing" might be a good idea, but the energy required to get a whole carrier back into orbit might pale in comparison to a fighter (or a fighter an hour for a month). It also might be underestimating the effectiveness of accurate orbital bombardment. If you control space, you could literally throw rocks (accurately) and devastate any opponents on the ground. Nobody likes personnel losses, even combat droids are expensive, but rocks aren't. $\endgroup$ – Xen2050 Sep 23 '17 at 9:31
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    $\begingroup$ @Xen2050 Even very precise orbital bombardment is going to be devastating. the whole point of boots, or bots, on the ground is control without wide scale destruction of the resource you are fighting over. If you blow up all the houses, where will your imported workers live? $\endgroup$ – Paul TIKI Sep 23 '17 at 11:13
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    $\begingroup$ "Boots on the ground" are necessary to effectively control an area which doesn't want to be controlled. And planet destroyers are...problematical... "My master - we have destroyed the last of the rebelling planets". "Good, good - now to return to our home planet, to plot further evil". "Errrrmmmm...about that..." "Yesssss?" "It seems...*all* the planets were rebelling, and so..." "Do you mean...?" "Yep - no planets left". "Dammit! I knew we'd overlooked something!!" $\endgroup$ – Bob Jarvis - Reinstate Monica Sep 23 '17 at 13:34
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For taking off, while it is possible to just boost directly away from the carrier, you might want a little extra speed without burning fuel. So have a magnetic linear accelerator along the length of the deck that boosts the fighter up to attack speed without a lot of wasted fuel.

Likewise, while you might not really need a long deck for launching, you do need a way to slow fighters down when they are returning to the carrier. An easy way to do this would be bring the fighter in parallel to this long deck, power up large magnets, and use the magnetic field to pull the fighter toward the carrier where conventional wheels and brakes could slow it down.
Or use the magnetic accelerator in reverse to slow the fighter down if you don't want to use conventional brakes.

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There is no real reason to have an long exposed flight deck. On earth the fighter need a catapult since it need the lift from the air and the craft have not so many space to reach its lift-off velocity.

In space you have not this problem, you can simply release the planes and let them go. (and here you have a couple of solutions like Battlestar Galactica or the anime Yamato 2199)
Not to mention the difficulties to work on such setup: what happen if an deck operator will drift away in space ? How you plan to pressurize the hangars under the flight deck ? How the lifts works ? Just to mention some of them.

So the only thing that I can think about is that the landing require some sort of rendez-vous to land (like a mechanical arm that catch the plane) so a big somewhat exposed deck mean more fighter land per minutes but this have its problems too: the deck is out in the space and you probably want to put them in the hangars, like on the actual aircraft carriers.

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  • $\begingroup$ Y'know, I always liked the Battlestar Galactica solution, because I figured that the "outriggers" were separated as they were from the ship in order to protect the ship proper from explosions (accidental or battle damage). $\endgroup$ – akaioi Sep 28 '17 at 3:23
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Space is big, and you want to save fuel whenever possible. Not just to stay up (that's actually the part that requires least fuel), but to go to a higher or lower orbit.

The spacecraft carrier could act as a sort of a railgun, launching these fighters from the deck using electromagnetism, giving them the velocity needed to reach the required orbit. Not only that, but when these fighters return, rather than using their own fuel, the same process can be reversed to slow down the fighters to a stop.

By my amateur space enthusiast calculations, this could save up to 30% of fuel!

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  • $\begingroup$ This answer would be far better if it included those calculations. However, something tells me that you are forgetting Newton's third law of motion; if one thing is slowed down, then the other must be accellerated, even if the absolute delta-v is different for the two because their mass is different. Ergo, both would end up in different orbits compared to where they started out. $\endgroup$ – a CVn Sep 22 '17 at 19:06
  • $\begingroup$ Alright, it was more of an estimation than an actual calculation, and I only have hundreds of hours of playing Kerbal Space Program as a qualification, but still! $\endgroup$ – M Arif Rahman Winandar Sep 22 '17 at 19:22
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    $\begingroup$ If it takes 1 unit of fuel to achieve 30 spaceknots (skt), then if your carrier launches the fighter at 30skt (1 unit fuel on carrier), the fighter slows to a stop (1 unit fuel on fighter), and returns at 30skt (1 unit fuel on fighter) and then the carrier decelerates it to stop (1unit fuel on carrier), then your carrier has halved the fuel requirements of the fighter. $\endgroup$ – sdfgeoff Sep 23 '17 at 7:35
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For lasers and relativistic projectiles, point defense systems may be impractical. So you are left with two options for defense, armor and evasiveness. For a fighter, thick armor is likely impractical so you want them to be moving with significant velocity before they leave the armored safety of the larger ship. There are two options for this, launch tubes and a flight deck that is facing away from the battle shielding the fighters with the belly of the ship. If you give the fighters engines that cannot safely be started inside the ship, such as fusion torches, and cannot be started after a mass driver launch, due to warm up or a need to be kick started by the carrier, then launch tubes won't work. And you are left with the solution of a long flight deck along a single side of the carrier.

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    $\begingroup$ You can use a rail gun system similar to our current carrier cable launch systems to have both a rail gun and a flat deck. Also, why just have 1 flat deck. The carrier has more than 1 side. $\endgroup$ – ShadoCat Sep 22 '17 at 19:03
  • $\begingroup$ @ShadoCat : You're suggesting a polygonal carrier, akin to a gigantic Toblerone®©™? Interesting... $\endgroup$ – user42997 Sep 22 '17 at 19:06
  • $\begingroup$ @ShadoCat Because space is an ocean, that's why. WARNING: TV Tropes link. $\endgroup$ – a CVn Sep 22 '17 at 19:08
  • $\begingroup$ Yes you can, I was trying to justify why you wouldn't launch craft from an internal launch tube with a rail gun and then start the dangerous engine outside. In part to satisfy the OPs requirement, with the justification that you want the flight deck shielded by the bulk of the ship. $\endgroup$ – Lex Sep 22 '17 at 19:08
  • $\begingroup$ @user42997, yes or what ever shape you wish. $\endgroup$ – ShadoCat Sep 22 '17 at 19:10
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Say you have artifical gravity. The technobabble means that "down" must be the same direction on the entire ship, but the direction can be chosen independent of the axis of thrust.

Next, consider that you do not want to carry fighters, you want to generate fighter sorties.

  • After a mission, a fighter comes in for a landing. The fighter may be damaged but repairable, with limited fine control for maneuvering. The landing space needs ot be relatively large. It helps if there are force fields to keep the air in while fighters can pass through.
  • After landing, the flighter might need a little servicing and maintenance on the sortie generation line, or it gets diverted for more time-consuming repairs in a proper workshop.
  • Before the next mission, the fighter goes to refueling and rearming. Handling armed missiles should be done away from the armored core areas of the ship.
  • The crew gets back in, and multiple fighters in a flight are spotted in a convenient holding area for near-simultaneous launch.

Fighters get moved from position to position. Considering the gravity, it is convenient to have small wheels on the fighters and to move them on a level surface, instead of lifts to move them upwards or whatever. As a side benefit, this would be compatible with planetary surface bases. Are the starfighters atmosphere-capable?

Imagine a long tube for fighter operations. Fighters enter it on one end, get processed, and leave on the other end. Almost like one of the nacelles of the Battlestar Galactica, except that launch catapults are not necessary if the fighter engines are good enough.

The tube might be straight, on perhaps an S shape to reduce length. An U shape would launch new sorties into the incoming fighters.

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Launch rails to protect the carrier

Other answers have suggested launch rails to save on fighter fuel, but I think the boost that would give may not be that relevant if your fighters have enough delta-v (number describing the capability of a spacecraft to change velocity, usually in m/s) to actually do interesting things.

Either way, I can think of one other reason why you might need a long launch rail system: The fighter engines are powerful enough to damage the carrier. Long story short, if you want both high thrust (i.e. enough that you can do maneuvers other than ponderously spiral out of orbit) and high specific impulse (i.e. you have enough delta-v that you don't run out of fuel in minutes), you need very high engine power. This means that at close range your engines are likely to be dangerous - doubly so if the power source is nuclear, which it likely has to be.

If your engines are powerful enough to harm the carrier, you have two choices: Use low power thrusters to get away from the carrier, or use some sort of launch rail. Using thruster fuel for this adds mass on each fighter, whereas the launch rail adds mass on the carrier. I'll ignore that space fighters might not make any sense, but this would apply also to drones and missiles with sufficiently powerful engines - in general, any high performance carried craft. It doesn't imply a flat deck though, but at least it implies distinct hangar space and launch facilities on the ship.

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A corn-style carrier would have a few downsides due to the many hangars:

  1. Hangar doors that open cannot be as thickly armored as a solid wall could be. So now the outside of your carrier is full of weak spots, and your most valuable possession (the fighters) is right behind the thin doors.

  2. Airlocks present a lot of complexity and are also difficult to armor. But repairing the fighters is easiest done in normal air pressure. So it makes sense to have a few craft elevators with built-in ship-sized airlocks.

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They don't all have long carrier flight decks, though there are ones like Battlestar Galactica that have fast-deployment rail tubes to shoot the fighters out at high speed, presumably to get them far away from the carrier and into action asap without using the fighter's fuel reserve.

Other sci-fi places have a more realistic approach, such as Babylon 5, seen here launching StarFuries in this youtube clip.

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The question makes it sound like your future humans just started building space navies not too long ago. If true, then there could be a simple explanation.

Coming up with radically new designs (corncobs and sea urchins) would involve building prototype ships and rewriting crew member training and operation procedures from scratch. Not only does this take potentially huge amounts of time and money, the end result may be extremely inefficient since the crew would be trained purely theoretically to operate on a brand-new, unproven platform.

Instead, the construction of space carriers in the image of naval carriers means that a large portion of tried-and-true carrier training dating all the way back to the mid 20th century can be carried over to the space carriers. Both officers and enlisted crew members would be trained with proven centuries-old techniques.

Obviously the crew would require additional training in how to operate the carriers in a true three-dimensional space (as opposed to operating on the ocean surface, which is far more two-dimensional), but the time and cost of such training can be reasonably presumed to be lower than the construction and testing of new designs.

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Why would you want to store the fighters?

The entry points for a modern space-based carrier ship aren't storage modules. That's ancient thinking. Space combat is dangerous and fighters are unlikely to come back entirely in one piece; there's likely damage to the armor plating at the least. Probably the engine is also quite damaged from the amount of energy pumping through it, and the laser based weapons also tend to burn out at around the exact same time that their battery runs dry (the engineers were clever like that).

The "hangar bays" atop the flight deck aren't actually used to store any fighters, they are entry points into the factory line. You extract the pilot and then pull the fighter through the dis-assembly line when it comes home; take it completely apart, fix (or eject) all the broken parts and just store the fighter's components in the carrier's storage.

Need to launch a new jet? Just pull all the required parts from storage and run it through the assembly line (in the other direction) and it's good to launch out the main flight deck.

Sure, you lose a little bit of time in launch speed. Not much, mind you. We found that the main bottleneck in launch speed was getting all the pilots to their launch positions.

But you win a lot in both craft durability (just getting rid of the refuel-caps has increased survivability by 5%) and in operational sustainability. The old ideas for a corn-cob based design were nice in theory, but it turns out that having 10 kernels with banged up fighters isn't as practical as disassembling them and building 6 new ones from the parts that still work.

And as a bonus, we get to use the entire length of the ship for armor plating, magnetic launch systems, defensive counter measures and other such useful things now.

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You would never have a large flat deck like ocean based carriers.

The purpose of the flight deck is to give enough space for a plane to take off and land.

In space, there is no gravity so you never need to take off. The moment you launch, you start floating before you fire up the engines.

Landing is a case of slowing right down for the ship to pick you up exactly like the shuttle docking with the International Space Station.

If you want to use a rail to accelerate the launch, there would be a hole like a gun barrel but strictly isn't necessary.

In all likelihood, the corncob design is the most sensible design. The ship is cylinder and spun to give a gravity like effect for the crew. With the fighters mounted on the outside, the moment the clamps release, centrifugal force would fling the fighters away from the ship.

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