I was watching ROTS the other day, and after observing the Jedi starfighters spiral past a Republic cruiser in the opening scene, it occurred to me that, in the vacuum of space, the ship with the larger engines would be faster, as opposed to the ship with the least mass. Specifically, fighters deployed from a Star Destroyer moving at speed ought to be unable to catch ub with it, because it would have a very high speed.

Fighters would be able to reach maximum acceleration faster, due to having less inertia, but once a fighter and a cruiser reached maximum acceleration, the fighter would be unable to catch up, unless I missed something.

Did I?

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Conversion Table:

2000 Mockingbirds = 2 Kilomockingbirds
Basic Unit of Laryngitis = 1 Hoarsepower
453.6 Graham Crackers = 1 Pound Cake
1 Kilogram of Falling Figs - 1 Fig Newton
Time Between Slipping on a Banana Peel and Smacking the Pavement = 1 Bananosecond
Half of a Large Intestine = 1 Semicolon

The fighters would have no speed relative the starship and therefore, unless it's accelerating, would have no problem catching up with it.


It depends on their thrust to mass ratio, which probably favour the fighters. And what do you mean by "maximum acceleration"? If the engines are putting out as much thrust as possible, both types of ships would have a pretty much constant acceleration (except for a few seconds at most as the engines start up; also discounting any mass lost as exhaust).

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Yes. You are making the same mistake that Time magazine made. For every action there is an equal and opposite reaction, but Time magazine wrote something in the early 20's about a rocket needing to "push" against something. Force does not need to "push" against anything. It's counter-intuitive, so the uninitiated make this mistake.

Since force depends on mass times acceleration, it's entirely possible that a small fighter craft could have greater applied force and therefore greater speed, because force is equal to mass times acceleration. Acceleration is also linked to speed, in that acceleration is the rate of change of speed, or a = v/t. Therefore you saying that a fighter could reach "maximum acceleration faster but have less speed" is nonsensical. There is no maximum acceleration, because there is no appreciable friction in vacuum and therefore you can accelerate forever as long as you have fuel. It's how Ion engines work IIRC.

There's a certain "click" you get when you study the math, and if you haven't studied the math I would just avoid making statements like this entirely. And don't study math to learn how to debate science fiction either, that's stupid and results in ripshod understanding: if you truly want to learn more about how the universe works, which is a noble goal and has nothing to do with science fiction, an excellent high school physics through distance education can do it. PM me for more information.

Otherwise, forget it, because you're talking out of ass like that Time writer, sorry.

ghetto edit: oops, made some mistakes: acceleration is dv/dt which is a little different ahahaha what a joke. Oh well, you get my meaning I hope. Anyway, I'll shut up now.

Right. Missed that.



Maximum acceleration ought to have been maximum speed, but brianeyci points out that there is no maximum speed in vacuum, rendering my entire point invalid.

Brianeyci, thank you for the explanation. Same to you, Dooey Jo.

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Conversion Table:

2000 Mockingbirds = 2 Kilomockingbirds
Basic Unit of Laryngitis = 1 Hoarsepower
453.6 Graham Crackers = 1 Pound Cake
1 Kilogram of Falling Figs - 1 Fig Newton
Time Between Slipping on a Banana Peel and Smacking the Pavement = 1 Bananosecond
Half of a Large Intestine = 1 Semicolon

Brian, I'm trying to make sense of your post.

For starters, net force is equal to mass times acceleration, so it's going to be near impossible for a fighter to put out as much thrust as a capital ship at full burn. That's meaningless, however, because the fighter has only a miniscule fraction of the mass that a capital ship has, so it doesn't need to generate anywhere near as much thrust as a capital ship to get the same acceleration. So, how fast a fighter is relative to a capship is determined by their respective thrust-to-mass ratios, not net applied force.

There also will be a maximum acceleration determined by the limits of your technology (i.e. power generation, inertial dampeners, drives, etc). Practically speaking, there isn't a maximum velocity, but you can't just continuously ramp up thrust because even assuming perfect inertial dampers and indestructitanium hulls, at some point the drive system is going to draw more power than what your ship can provide.

Yeah, I realized what you said Huang just a few seconds after I posted hahaha I sounded like some presumptuous ass. Mass to thrust ratio is the obvious factor, not net applied force.

I'll let those with better education than me talk now haha.

As others have already pointed out, the determining factor is the "thrust-to-mass ratio". You divide the thrust by the mass to calculate a spacecraft's acceleration.

The key point is that with terrestrial aircraft the thrust-to-mass ratio goes up as the aircraft size goes down. So fighters have higher acceleration than passenger jets. SF authors then jumped to the erroneous conclusion that the same thing would hold true with spacecraft.

In reality, it is possible to design a Star Destroyer sized spacecraft with a higher thrust-to-mass ratio than a fighter spacecraft. It all depend upon the technological assumptions one makes for one's future universe.

http://www.projectrho.com/rocket/rocket3x.html#fighters

That was the crux of my post, i.e. that s ship with larger engines would go faster. I made the same mistake as the SF authors, only in reverse.

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Conversion Table:

2000 Mockingbirds = 2 Kilomockingbirds
Basic Unit of Laryngitis = 1 Hoarsepower
453.6 Graham Crackers = 1 Pound Cake
1 Kilogram of Falling Figs - 1 Fig Newton
Time Between Slipping on a Banana Peel and Smacking the Pavement = 1 Bananosecond
Half of a Large Intestine = 1 Semicolon

Ghetto edit: The quotes are messed up. Sorry, Nyrath is who should be quoted.

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Conversion Table:

2000 Mockingbirds = 2 Kilomockingbirds
Basic Unit of Laryngitis = 1 Hoarsepower
453.6 Graham Crackers = 1 Pound Cake
1 Kilogram of Falling Figs - 1 Fig Newton
Time Between Slipping on a Banana Peel and Smacking the Pavement = 1 Bananosecond
Half of a Large Intestine = 1 Semicolon

I actually fell out of my chair laughing.

As Nyrath says, it depends on assumptions. Most universes assume that small craft are faster, and that's not necesserily unreasonable. As a rule they can certainly turn faster - for much the same reasons as the hundred foot woman is silly, see the size matters page - and thus achieve higher manouverability than larger starships. Linear speed, however, is a different matter. Star Wars itself isn't so terrible in this regard; watch the chase scenes in Empire Strikes Back. The Falcon can't outrun Star Destroyers, but it can turn a hell of a lot quicker than they can.

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Fighters will likely have a greater engine to mass ratio, given that they don't need toilets, nearly as much protection, more than short-lived weapons (like a bomb, which is much lighter than a giant cannon), life support and fuel only for maybe a few hours and so on.

Assuming your puny fighter scale engine is of similar efficiency to your big capital one, it'll probably accelerate faster because it's got more thrust for the kilo.

Of course, this ignores why you can't just make them go EVEN FASTER by replacing a 150 pound pilot and support gear with a 20 pound computer, but that's another story...

It’s quite possible for fighters to have better close in agility then big ships; but they still don’t make sense as space weapons, and allowing sci tech only makes things worse really. Too little endurance, too lightly armed, too easy to destroy and they lose all of the advantages which make aircraft so powerful in terrestrial naval combat. No advantage in being solely able to use the third dimension, no horizon to hide behind, no advantage in strategic mobility ect.. Meanwhile energy shields mean that fighter weapons should by all rights just go splat and accomplish nothing when not used in huge numbers, while in the absence of shields you can at least slowly inflict damage with anything you can hit with.

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The opposite argument can also be made. All you need to support a crew for a capital ship is a control pod, and the rest can be ginormous engines, weapons and such. In comparison, the support for one human can take up a sizeable portion of the volume of a fighter. Look at how much of a Saturn Five rocket is inhabitable, compared to say, an F22.

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Wrong analogy. A Saturn V is mostly fuel, which is why the only habitable portion of it is the capsule. A capship, on the other hand, actually needs to devote space to the accomodation of a large crew of engineers, repair techs, and other types of support personnel. It is also presumed that if such a vessel were feasible at all, a drive system based on entirely different principles than chemical reaction engines and employing a fuel with a far higher energy density per unit of mass than LOX would be in use.

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You're assuming it's not some sort of suicide vessal. That it goes on long-haul missions, rather than simply returning to a dock somewhere for maintainance, and that it requires significant amounts of support personnel. Starships from, say, Stargate, often appear to have little trouble surviving without support personnel for centuries or longer.And space opera vessels can have any size crew they like. Which goes back to the original point of it largely being a matter of author fiat how the dynamics work.

Some ships require one hundred and fifty people and a horde of maintainance bots, (Lucrehulks) so crew ameinities can be essentially discounted, and some require thousands and thousands (Imperator class destroyers, for instance).

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Fighters have an advantage over larger ships in that they can use less of their mass for structural strength. Also, their reactors can run hotter than a capital ship, as a ship 1/8 the size only has 1/4 the surface area on the interior of its reactor. Assuming identical materials technologies, the smaller vessel can get a reactor running twice as hot.

So fighters will use a smaller mass fraction for structural support, and can get more power per unit of mass from their engine.


Capital ships have several advantages though. First, is that they have all interior lines of communication. If you have an advanced battlecomputer that gives your shots a 5% better chance of hitting, a capital ship only needs one, while fighters need one per (unless you have really good datalink technology). Capital ships also have better recovery after damage. A fighter formation will lose members due to damage, hile a capital ship will only lose shields/armor when taking damage. So a capital ship vs fighters fight that involves hit & run, the capital ship will be regenerating/repairing shields/armor, while the fighters steadily lose members.

So capital ships have an advantage in terms of interior communications, excess damage capacity, and equipment efficiency.

I'd see ships in separate categories:

Strike - essentially short-ranged vessels with roughly 12 hours of life-support capability. Hardly any food or bathroom capacity. Either launched from a planet or carried by a carrier vessel. Examples include Fighters, Monitors, Missile Pods.

Self-contained - vessel is capable of supporting itself in terms of life-support and crew capability. Examples include water navy gunships, submarines, Enterprise-D

Support - vessel with extensive facilities for providing resources, resupply, and recreation for other vessels. Examples include current naval carriers, troopships, Star Destroyer, hopsital ships

(the above only separates them according to life support capacity, aka not enough, enough, and more than enough)

So it is possible for long-term 'fighters' to support a Strike warship, where the fighters carry the supplies needed by the larger ship, using their higher engine efficiency and smaller structural mass fraction to pack in lots of supplies and deliver them quickly, while the larger vessel uses its internal comunications and computers to coordinate strikes against enemy strongpoints. The small size of the supply vessels means that the enemy has to stop lots of them to interdict the larger vessel.

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Actually fighters are EXPENDABLE. Think of it this way you are in charge of sweeping an asteroid field of pirate ships yet you have noi idea where said ships are hidden.

So do you send in the big expensive cruiser to sweep it or send in a group of fighters?

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If any civilisation is going to make the investment of building such a platform in the first place, they're not going to make it as anything other than a ship designed for long-haul missions with the attendant maintenance and support requirements.

As for the Stargate example, that points only to how little the writers of that series have thought the problem through.




While space-opera vessels "can have any size crew they like" due to "writers' fiat", that does not automatically negate the exercise of rational analysis into how a given vessel would be constructed to follow a particular function and mission profile.

Aside from that, at the end of the day the rebuttal of your attempted Saturn V analogy still stands: that rocket is not at all comparable to any hypothetical starship given its limitations —chief of which is that it had to be about 90% fuel simply to get to translunar flight because of the performance restrictions of chemical fuel.

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And in the end, isnt that what it's all about?

The only way that fighters or drones would be usefull, would be as spammers? Just, to bother the PD systems or something. Maybe they could have some kind of device that fools the guns to shoot at them instead of shooting at the other warships in the area?

I dont know, it always seems stupid to use a small ship when a bigger one that can dish out more damage and take more is available.

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Space fighters make sense under one condition.

Existence of bombers or fighter-bombers capable of destroying capital ships.

Even without the speed advantage that terrestrial aircraft possess, a carrier with a force of bombers has an advantage over a capital ship with the same firepower as the bombers does retain two advantages of real aircraft carriers:

1. The carrier stays behind with the rest of the fleet, and risks only its bombers, which are cheaper to replace if lost than a capital ship would be.

2. The bomber force can be split and attack two targets simultaneously--or remain behind to defend the fleet.

Assuming existence of such craft, that can be based on either capital ships or planetary bases, one would need fighters to defend against them--because by the time they get within range of your capital ships' defensive systems, it may be too late. And if you used such craft, you would need fighters to protect them from enemy fighters, as well.

nBSG works this way. Cylon Raiders can, with enough numbers, destroy the Battlestars. The ship's own defenses aren't enough, so, to intercept them earlier, they use the Vipers.

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Depends on the stategic manouverability. If you've got some kind of fold-space drive, or something that can cross the galaxy in an hour, a mission to defend a colony or punish rebels need only take half a day. Take an engine, some weapons, and maybe some defences, and bolt on a bare minimum sized control pod for the crew to sit in, and you've got a starship.However, when dealing with completely made up things, such as FTL, we can construct a mission profile however we like. Jump-and-nuke for example, doesn't require a massive long term crew or major maintainance capacities.You find there to be something wrong with a sci-fi starship that's basically all engine - why? That seems eminently reasonable to me. Why can't space opera starships be all engine?

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A way fighters can work is not as fighters at all, but rather somewhat analogous to torpedo boats. Basically you use your strike-craft as a reusable first stage for cap-killer missiles. The reason why you would want to have a reusable first stage is the lack of computers smart enough to know when and were to best release their ordnance but cheap enough to be disposable. If you want a manned first stage, you either up the price of the computer such that using people is better, or lower computer performance such that using people is better.

The question is, why should I bother with fighters/bombers/torpedo boats if I can just use missiles instead?

Didn't see the Post by Adrian Laguna. That would indeed be a situation where short range torpedo boats might make sense, simply by providing the enemy with to many targets to attack them all, and/or give the mothership a way to attack the enemy without being forced to make itself a target by coming to close or risking detection by firing weapons.

On the other hand, I seriously doubt any civilization capable of space warfare on that level won't be able to remote control those missiles or give them reasonably cheap and effective AI. And that will always be cheaper, both in terms of rescources and lifes, than manning small craft which are supposed to be expendable.