A Question Of Maneuverability

Discussion regarding the Outsider webcomic, science, technology and science fiction.

Moderator: Outsider Moderators

User avatar
Cthulhu
Posts: 1046
Joined: Sat Dec 01, 2012 6:15 pm
Location: R'lyeh

Re: A Question Of Maneuverability

Post by Cthulhu »

spacewhale wrote:
Tue Feb 01, 2022 5:01 pm
Assuming you burn all the torpedoes to get speed, but if you're burning a subset, I'd see it as no different than using stages in a multistage rocket.
Then you reduce the offensive potential of the torpedoes that you do burn.
spacewhale wrote:
Tue Feb 01, 2022 5:01 pm
Depends on the size of the torpedoes and torpedo boat. You could presumably have outsized, heavy hitting munitions on a small vessel.
A fighter or gunboat should be fast enough already.
spacewhale wrote:
Tue Feb 01, 2022 5:01 pm
I don't see why you couldn't turn them on and off, they are after all, just fusion drives. No rule stating you couldn't have them coast closer to an enemy, change attitude, and re-ignite later.
They are not fusion-driven, but use some sort of exotic matter reaction that needs ignition as well as containment.
spacewhale wrote:
Tue Feb 01, 2022 5:01 pm
Pretty sure a single shot against a flying bundle of fusion fuel would be fatal either way, the goal behind using missiles as boosters would be to close the distance faster to fight in close range while still being able to deliver missiles on target. Once the missiles are free, no reason to worry about the racks extending outwards or not, they have no further payload, and could be jettisoned if necessary.
Then it would be better to have the torpedoes burn harder on their own, since their small size and mass would allow them to accelerate far better than any carrier vessel.

User avatar
SVlad
Posts: 307
Joined: Thu Aug 27, 2015 5:43 pm
Location: Saint-Petersburg, Russia

Re: A Question Of Maneuverability

Post by SVlad »

I really doubt that using torpedoes as busters made and significant change in ship speed. They have twice the acceleration of the ship, but thousands times lighter. So their effect would be the thousandth part of ships acceleration.
Outsider in Russian
Image

Tamri
Posts: 340
Joined: Tue Dec 15, 2015 8:55 pm

Re: A Question Of Maneuverability

Post by Tamri »

At the same time, since the main acceleration factor here is "virtual mass", deltaV is actually calculated not quite according to the formula, since the ratio of mass consumption to thrust-weight ratio should be non-linear.

Demarquis
Posts: 452
Joined: Mon Aug 16, 2021 9:03 pm

Re: A Question Of Maneuverability

Post by Demarquis »

"Then it would be better to have the torpedoes burn harder on their own, since their small size and mass would allow them to accelerate far better than any carrier vessel."

If the torpedoes and the firing ship are using the same type of drive, then size and mass should have no effect on acceleration because the torpedoes have smaller drives as well.

User avatar
Cthulhu
Posts: 1046
Joined: Sat Dec 01, 2012 6:15 pm
Location: R'lyeh

Re: A Question Of Maneuverability

Post by Cthulhu »

Demarquis wrote:
Sun Feb 06, 2022 5:53 pm
If the torpedoes and the firing ship are using the same type of drive, then size and mass should have no effect on acceleration because the torpedoes have smaller drives as well.
Trust-weight ratio, my friend. A torpedo is little more than a fuel cell, reactor and drive, while a ship, even a fighter, will have more components. After all, the torpedoes can accelerate up to 60g, but weight merely 20 to 80 tons. Then, compare that with a vessel that weights thousands of tons, while still being able to accelerate with 30g. How much trust can a torpedo engine even add?

Demarquis
Posts: 452
Joined: Mon Aug 16, 2021 9:03 pm

Re: A Question Of Maneuverability

Post by Demarquis »

That's two different issues. A torpedo is nothing more than a miniature space ship (if said space ship is fully automated and has no crew). It will have everything that the larger craft would have, including sensors, maneuvering thrusters, heat management system, hull, fuel stores, etc. If the torpedo and the launching craft are using the same drive type then there is no a priori reason why the smaller vessel would be able to accelerate faster than the larger one (this is one reason why space fighters are soft science fiction). Adding a crew to the larger vessel will make a difference, admittedly, the issue being how much. In most realistic spacecraft designs, the vast majority of mass is given over to fuel and propellant, so the life support apparatus for even a large crew would not be significant. In this story that appears not to be the case, so perhaps there is a greater difference.

How much thrust firing the torpedoes (missiles) could add to the launching craft's own thrust depends, of course, on how much thrust the main drive vs. the missile drives generates. This is a design consideration that is entirely up to the engineers--it's simply a matter of assigning delta v to different parts of the launching platform/missile system. There are benefits and tradeoffs either way: a system which assigns nearly all the thrust to the main ship drive (ie, it deploys "smart bombs" with little thrust of their own) vs. a system which divides the delta v the other way (ie, a space station with a missile battery), or something that is more evenly distributed (some kind of patrol craft with a missile rack larger than itself). Any of these could be of any size, there being no physics reason to restrict the options (depending on how the technology is depicted within a given story there might be operational reasons, of course).

All this goes out the window if the missiles and the spaceship use different drive types, like a Nuclear Thermal drive firing chemical rocket missiles.

User avatar
Cthulhu
Posts: 1046
Joined: Sat Dec 01, 2012 6:15 pm
Location: R'lyeh

Re: A Question Of Maneuverability

Post by Cthulhu »

1. A torpedo uses the same drive system, reactor and fuel type that the other ships have.
2. However, the missile doesn't need inertial dampeners, weapons, jump drives, heavy armor, screens, crew quarters, supply storage, etc. Therefore, it can have an utterly oversized engine compared to its tiny mass.

Let's do some rocket science:
A Loroi destroyer-sized vessel is around 75 kt dry-weight, let's assume that a fully loaded one is 100 kt and can accelerate up to 30g.
A Loroi medium torpedo weights 35 t and accelerates up to 45 g, whereas a long-range torpedo is 70t and 60g.

This means:
The destroyer has an engine output of ~29.42 giga-newtons, the medium torpedo just ~0.0154 giga-newtons, and the heavy one ~0.0412 giga-newtons. I won't even bother adding that to the destroyer's acceleration capability, that's not going to change much.

Demarquis
Posts: 452
Joined: Mon Aug 16, 2021 9:03 pm

Re: A Question Of Maneuverability

Post by Demarquis »

Yes, all that's true in-universe, because the author proclaimed it (I assume, I haven't read the supplementary material), but not necessarily true in general. It may not need an intertial dampener because it isn't manned, which could make a difference (as I myself pointed out) but that depends on how much an ID weighs as a percentage of total ship weight. "Jump Drive" comes under "using different drives"--if you have the capacity to make torpedoes FTL but choose not to utilize that, well, that's a design decision. Armor is proportional, the torpedo's armor can be quite thin and still be the same percentage of total mass. The weapon is the payload (or the extra propellant/fuel if you're going with a kinetic strike). Why wouldn't you want it to have it's own screen?

But even if we take your list at face value, and the crew plus associated accessories and supplies adds another 33% to total mass of the ship, then using the torps to help power the ship will detract from the performance of the torp's alone by that amount. It then becomes a tactical decision whether or not the gain of the additional boost they provide the ship (whatever that is, it depends on how big they are) is worth the additional cost. The captain would presumably decide based on the specific circumstances.

In this story (according to your figures) the torps aren't very large and therefore you would need a bunch of them to add much (there is no a priori reason to limit them to such a small size, but perhaps there are operational considerations I am not aware of). Your math, I note, doesn't account for the total number of torpedoes involved. By your figures, roughly 700 heavy torpedoes produce about the same amount of force as a Loroi destroyer's main drive. I don't know how many torpedoes a destroyer normally carries, but a 100 or so doesn't seem too extreme. Let's round down and say they could add a tenth more thrust by using them.

Probably not worth it, but who knows?

User avatar
Cthulhu
Posts: 1046
Joined: Sat Dec 01, 2012 6:15 pm
Location: R'lyeh

Re: A Question Of Maneuverability

Post by Cthulhu »

Demarquis wrote:
Wed Feb 09, 2022 11:04 pm
(I assume, I haven't read the supplementary material)
Then what are we even arguing about? This discussion won't work without knowledge of the weapon database, at the very least. Let me be as clear as possible, this strategy will not work, it is a grossly inefficient method to waste precious ammo, and the Loroi do not have the capability to supply such huge numbers of torpedoes. The Warhammer-class destroyer in question, for example, has a standard supply of just 18 torpedoes, but it is often far less than that.

Anyway, imagine trying to use a modern fighter plane's missiles to give it a boost mid-flight? Or even strapping some JATOs to a car? :shock:

Demarquis
Posts: 452
Joined: Mon Aug 16, 2021 9:03 pm

Re: A Question Of Maneuverability

Post by Demarquis »

This thread was begun by Bamax, who said, in part:

"I am of the opinion that IRL spaceships often get by with less for the simple reason that they do not need full maneuverability."

and "What do you think? Both for scifi and real ife?"

Therefore, I have not been assuming that the discussion was limited to "Outsider" canon. If that was confusing, I apologize.

It's clearly one way within this story, because the author says it is. Fair enough. But outside that context, other factors are worth taking into consideration. I note that even you are using examples from real life. Fighter planes utilize missiles that are much smaller in cross section than the launching platform because that confers a distinct advantage when traveling through atmospheric resistance. Strapping a rocket to a car, while amusing, isn't practical because a land vehicle must maintain contact with a surface to generate traction. Neither consideration applies to space craft.

User avatar
spacewhale
Posts: 123
Joined: Fri Jul 24, 2020 7:08 am

Re: A Question Of Maneuverability

Post by spacewhale »

I don't think the idea of consumable units of propulsion is particularly impractical. We do it with multistage rockets, you've got drop-tanks on all sorts of aircraft. Considering craft can literally tow gunboats in hyperspace, what makes you think you couldn't have absolutely absurdly large missiles on something that was basically the smallest possible hyperdrive equipped vessel?

User avatar
Cthulhu
Posts: 1046
Joined: Sat Dec 01, 2012 6:15 pm
Location: R'lyeh

Re: A Question Of Maneuverability

Post by Cthulhu »

Demarquis wrote:
Thu Feb 10, 2022 11:51 pm
This thread was begun by Bamax, who said, in part:

"I am of the opinion that IRL spaceships often get by with less for the simple reason that they do not need full maneuverability."

and "What do you think? Both for scifi and real ife?"

Therefore, I have not been assuming that the discussion was limited to "Outsider" canon. If that was confusing, I apologize.

It's clearly one way within this story, because the author says it is. Fair enough. But outside that context, other factors are worth taking into consideration. I note that even you are using examples from real life. Fighter planes utilize missiles that are much smaller in cross section than the launching platform because that confers a distinct advantage when traveling through atmospheric resistance. Strapping a rocket to a car, while amusing, isn't practical because a land vehicle must maintain contact with a surface to generate traction. Neither consideration applies to space craft.
To be honest, this thread was probably started out of boredom with no clear goal in mind. Well, except to help pass the time until the comic updates. Therefore, it can be said that anything goes, as long as it's amusing.

In general, if something is done in a certain way in a fictional universe, then it should be assumed that there's a good reason for it. However, if you want to discuss that in depth, then you would also need more in-depth knowledge. :ugeek:

While my remarks about JATOs were mostly humorous, the idea about using torpedoes as additional means of propulsion is equally silly.
1. Negligibly small thrust compared to a ship alone, and not enough torpedoes to make it worthwhile.
2. Short fuel endurance, especially since the fuel is also the payload.
3. Very complex racks that have to ensure that the torpedoes will be shielded from enemy fire, do not burn something with their exhaust and can be launched without damaging anything. Normally, the torpedoes use either catapult launchers or small maneuvering thrusters to reach a safe distance and then ignite their main drives.
spacewhale wrote:
Fri Feb 11, 2022 6:10 am
I don't think the idea of consumable units of propulsion is particularly impractical. We do it with multistage rockets, you've got drop-tanks on all sorts of aircraft. Considering craft can literally tow gunboats in hyperspace, what makes you think you couldn't have absolutely absurdly large missiles on something that was basically the smallest possible hyperdrive equipped vessel?
So what would that even accomplish? Again, we have to call upon the Insider database, this time, about hyperspace drives. The smallest jump-capable vessels are in the range of 150 m, since the jump field generators are very energy-hungry. But if you strap something to that ship, then you'd need to extend the jump, as well as the inertia-dampening fields to encompass that extra mass and volume as well. This, in turn, would increase the size of the ship itself, until you end up with a "normal" missile destroyer or cruiser. Even the gunboat tenders carry only about a quarter of their mass in docked gunboats, at best.

Additionally, the fuel cells are quite complex pieces of equipment, it's not as easy and cheap as some strap-on drop-tanks.

gaerzi
Posts: 253
Joined: Thu Jan 30, 2020 5:14 pm

Re: A Question Of Maneuverability

Post by gaerzi »

If you design a spaceship that would really benefit from using torpedoes as extra engines... why not put extra engines to begin with?

And from the Loroi point of view, it's not like they really could afford to waste half their torpedoes on extra maneuvering capabilities. All that means would be that they'd no longer have that extra maneuverability once they really need it -- i.e. after they've expended most of their supplies.
spacewhale wrote:
Fri Feb 11, 2022 6:10 am
I don't think the idea of consumable units of propulsion is particularly impractical. We do it with multistage rockets, you've got drop-tanks on all sorts of aircraft.
Multistage rockets are to escape the gravity well of our planet. We wouldn't use them if we could do without. They're a tremendous waste of money.
https://www.nasa.gov/mission_pages/stat ... yanny.html

Drop tanks are not actually dropped except in case of emergency. It just would be too expensive if they were dropped every time they're emptied. But a fighter has a limited amount of pylons on which to install drop tank, and every pylon used by a drop tank is a pylon that can't be used for a missile, bomb, or mission pod. You're not really adding consumable unit of propulsion (the drop tank doesn't propel at all, to the contrary it's a big source of drag), you're just moving the cursor between "payload" and "fuel" more towards the "fuel" side.

Demarquis
Posts: 452
Joined: Mon Aug 16, 2021 9:03 pm

Re: A Question Of Maneuverability

Post by Demarquis »

"To be honest, this thread was probably started out of boredom with no clear goal in mind. Well, except to help pass the time until the comic updates. Therefore, it can be said that anything goes, as long as it's amusing."

I shall attempt to be as amusing as possible, then. What I won't be doing is limiting my discussion to the technical specs provided by the author (all due respect to the author, but there *are* other works out there, not to mention a real world).

"If you design a spaceship that would really benefit from using torpedoes as extra engines... why not put extra engines to begin with?"

That is, of course, the million dollar question. But let me rephrase--the issues is why not dump the same propellant through the main drive? In general, this would be better, except now the ship has no missiles. The only point of "de-weaponizing" the missiles and using them for additional thrust would be to give the captain an additional option, depending upon circumstances. Whether such circumstances would arise often enough to justify the additional complication depends on how the tech plays out in a given setting.

"And from the Loroi point of view, it's not like they really could afford to waste half their torpedoes on extra maneuvering capabilities. All that means would be that they'd no longer have that extra maneuverability once they really need it -- i.e. after they've expended most of their supplies."

Well, that's true regardless of where you store your delta-v. Any maneuvering *now* is purchased at the expense of being able to maneuver in the future. In the Loroi universe, apparently, fuel is cheap, so cheap that conserving propellant mass may be an insignificant design consideration. But that needn't be true in other settings.

In the real world, there is no technical reason why ship-born missiles need to be smaller than the ship that carries them. I can easily envision a type of artillery battery, which consists of very large missiles attached to a very small command module, and an engine. Such a ship might not have much defensive capacity, such that running away with the battery intact might be the better option, compared to getting it destroyed. Using the missiles as one-shot emergency thrusters could make sense then (you could also fire the missiles and run, and that might be more effective, or not, depending on how the situation was set up).

There is really no engineering related reason to restrict missile design to the set-up we are used to here on Earth. We're used to seeing large ships firing salvos of relatively small missiles, but that's due to atmospheric conditions that do not apply in space.
Last edited by Demarquis on Tue Feb 15, 2022 6:22 pm, edited 1 time in total.

Bamax
Posts: 1044
Joined: Sat May 22, 2021 11:23 am

Re: A Question Of Maneuverability

Post by Bamax »

Demarquis 'speaks' correctly as far as IRL goes.

IRL bigger missiles are better, even ship-size missiles. Why? Because fuel/propellant is finite and space is virtually infinite, the more you have the farther you can maneuver.

The more you can maneuver the less likely you are to get hit.

And regarding real world space lasers, unless the focusing lens itself is gigantic, it's effective range won't be all that great.

Which means that a giant laser is nigh unlikely to stop the equivalent of a freight train (a giant missile) from crashing into it and destroying it.

Burning small holes in a giant missile coming at you may or may not be enough to stop it, since hull rotation and armor are viable anti-laser tactics, neither can lasers fire indefinitely either.... they need large radiator fins and time to 'cool' (radiate) waste heat away.

gaerzi
Posts: 253
Joined: Thu Jan 30, 2020 5:14 pm

Re: A Question Of Maneuverability

Post by gaerzi »

Demarquis wrote:
Sun Feb 13, 2022 12:54 am
In the real world, there is no technical reason why ship-born missiles need to be smaller than the ship that carries them. I can easily envision a type of artillery batter, which consists of very large missiles attached to a very small command module, and an engine. Such a ship might not have much defensive capacity, such that running away with the battery intact might be the better option, compared to getting it destroyed. Using the missiles as one-shot emergency thrusters could make sense then (you could also fire the missiles and run, and that might be more effective, or not, depending on how the situation was set up).

There is really no engineering related reason to restrict missile design to the set-up we are used to here on Earth. We're used to seeing large ships firing salvos of relatively small missiles, but that's due to atmospheric conditions that do not apply in space.
The missile needs basically only three things:
- a seeker head with sensors and flight computer so that it can doggedly pursue its target
- a propulsion and flight control system so that it can actually doggedly pursue its target
- a payload so that it can blow up the target once it has caught up to it
In Outsider, that payload is basically whatever fuel remains in the missile. Also the missile is a consumable. So to save cost, each component is only as good as it really needs to be.

The spaceship also needs sensors, flight computers, engines, and fuel, but it also needs more stuff. Like the jump drive and crew quarters and life support systems. Also the space ship is not consumable. You don't want to lose it forever in deep space just because the engine fizzed out. Whereas if you lose a missile, well, it's too bad it didn't go and blow up an enemy ship but you were planning on losing it anyway. So your spaceship will have redundancy everywhere, and the best systems you can get. So that makes it that the minimum size of a spaceship is probably larger than the minimum size of a missile.

There's really one factor that can make or break the "bigger missiles than ships" and it's the size of the fuel tanks. The missiles need enough fuel to cover engagement range (including maneuvering) and keep enough surplus fuel to serve as an effective payload (unless they're carrying a dedicated explosive payload). The spaceship needs enough fuel to cover cruising range while carrying the missiles. Most likely, cruising range will be superior to engagement range, otherwise you may as well use static defenses.

Demarquis
Posts: 452
Joined: Mon Aug 16, 2021 9:03 pm

Re: A Question Of Maneuverability

Post by Demarquis »

@Bamax:

"And regarding real world space lasers, unless the focusing lens itself is gigantic, it's effective range won't be all that great.

Which means that a giant laser is nigh unlikely to stop the equivalent of a freight train (a giant missile) from crashing into it and destroying it."

Er, that depends. First, why can't the focusing lens be "gigantic", whatever that is taken to mean? Second, many smaller lasers can combine their beams on the same target, increasing the energy they transfer and also their range. Third, it's possible to mission kill the missile without necessarily vaporizing it: destroying the sensor package, the warhead, or the maneuvering thrusters alone would be enough.

@Gaerzi: "The spaceship also needs sensors, flight computers, engines, and fuel, but it also needs more stuff. Like the jump drive and crew quarters and life support systems. Also the space ship is not consumable. You don't want to lose it forever in deep space just because the engine fizzed out. Whereas if you lose a missile, well, it's too bad it didn't go and blow up an enemy ship but you were planning on losing it anyway. So your spaceship will have redundancy everywhere, and the best systems you can get. So that makes it that the minimum size of a spaceship is probably larger than the minimum size of a missile.

There's really one factor that can make or break the "bigger missiles than ships" and it's the size of the fuel tanks. The missiles need enough fuel to cover engagement range (including maneuvering) and keep enough surplus fuel to serve as an effective payload (unless they're carrying a dedicated explosive payload). The spaceship needs enough fuel to cover cruising range while carrying the missiles. Most likely, cruising range will be superior to engagement range, otherwise you may as well use static defenses."

I largely agree with your first paragraph, disagree with the second. Of the things you list as necessary for a ship but not a missile, the most important is the human crew and all the associated equipment and supplies. This leads us to the question: "Why do combat ship in the Outsider universe require an organic crew?" Evidently, and by authorial fiat, organic critters add some sort of advantage that AI cannot match. Fair enough. In that case, it makes sense for ship designs to cater to the needs of the crew, while missiles can dispense with all that. In other settings, this might not be so true. In real life, it almost certainly won't be true.

I think you make an error in the second paragraph, however, by conflating range with delta-v (ie, "change in velocity", or acceleration). The missiles need enough fuel (propellant) to match their target's evasive maneuvers and still have enough mass and/or relative velocity left over to do significant damage (the more of a velocity advantage the missile has over the target, the less mass it needs to do the same mount of damage). Meanwhile, "cruising" requires no more delta-v than is needed to accelerate to the desired velocity, and from there the ship can coast without using any fuel at all, unless it needs to correct its' course for some reason. Whether the ship needs more delta-v to complete its' patrol or the missiles need more to catch the target (which will frequently be an enemy ship cruising on its' patrol) will depend on specific circumstances. I can even see a trade-off where the launching ship's delta-v could be maximized at the expense of the missiles, or the reverse, depending on the mission. This is where using missiles as a back-up source of thrust might come in useful.

I would suppose that in general, to the extent that the target's point defenses are strong (whatever form that takes in a given setting), the less of an advantage delta-v will be for the ship, and the more advantage it will be to give it over to the missiles. This is because the missiles will need that delta-v in order to evade the point defenses and catch the targets (this may take the form of a large number of small missiles which nevertheless add up to a significant amount of the total delta-v). On the other hand, to the extent that the enemy's point defenses are weak, the more advantage will be derived from putting that delta-v into the launching ship's main drive, because getting within range and acquiring an advantageous launching position will be the main challenges (this may take the form of a small number of relatively larger missiles which add up to a reduced fraction of total delta-v).

As you can see, the number of missiles, and the size of the missiles, is a trade-off that complicates the issue. The real underlying question is where the delta-v budget is to be spent: is it to be made available mostly to the missile drives, or to the ship's drive?

"Small ship/large missile" is a design that will likely be most advantageous when in a positional disadvantage against an enemy ship larger and more capable than one's own (because giving the missile as much delta-v as possible is the only chance of hitting it). If humans were to go up against the Loroi, they would be well advised to deploy very large missiles in the hope that the wreckage will manage to intersect the enemy despite their advantage in point defenses (actually, I would advise them to develop an FTL missile, and start lobbing across the lightyears).

"Large ship/small missile" sounds to me more likely when in a positional advantage with better ships than the enemy has. Maneuver circles around them, and pick them off with cheap missiles. This is the Loroi against the humans (they need to get into human inhabited space as soon as possible to force the enemy to engage with their inferior vessels).

But really, the underlying question is still where should the delta-v go within the "ship-missile system"? Do you invest primarily in the ship, or in the missiles (bear in mind that the ship must carry the missiles until they are fired)? And what are the consequences of making a mistake? Again, this is where having some options (such as converting the missiles into back-up thrusters) might be helpful.

Bamax
Posts: 1044
Joined: Sat May 22, 2021 11:23 am

Re: A Question Of Maneuverability

Post by Bamax »

Demarquis wrote:
Tue Feb 15, 2022 6:28 pm
@Bamax:

"And regarding real world space lasers, unless the focusing lens itself is gigantic, it's effective range won't be all that great.

Which means that a giant laser is nigh unlikely to stop the equivalent of a freight train (a giant missile) from crashing into it and destroying it."

Er, that depends. First, why can't the focusing lens be "gigantic", whatever that is taken to mean? Second, many smaller lasers can combine their beams on the same target, increasing the energy they transfer and also their range. Third, it's possible to mission kill the missile without necessarily vaporizing it: destroying the sensor package, the warhead, or the maneuvering thrusters alone would be enough.

@Gaerzi: "The spaceship also needs sensors, flight computers, engines, and fuel, but it also needs more stuff. Like the jump drive and crew quarters and life support systems. Also the space ship is not consumable. You don't want to lose it forever in deep space just because the engine fizzed out. Whereas if you lose a missile, well, it's too bad it didn't go and blow up an enemy ship but you were planning on losing it anyway. So your spaceship will have redundancy everywhere, and the best systems you can get. So that makes it that the minimum size of a spaceship is probably larger than the minimum size of a missile.

There's really one factor that can make or break the "bigger missiles than ships" and it's the size of the fuel tanks. The missiles need enough fuel to cover engagement range (including maneuvering) and keep enough surplus fuel to serve as an effective payload (unless they're carrying a dedicated explosive payload). The spaceship needs enough fuel to cover cruising range while carrying the missiles. Most likely, cruising range will be superior to engagement range, otherwise you may as well use static defenses."

I largely agree with your first paragraph, disagree with the second. Of the things you list as necessary for a ship but not a missile, the most important is the human crew and all the associated equipment and supplies. This leads us to the question: "Why do combat ship in the Outsider universe require an organic crew?" Evidently, and by authorial fiat, organic critters add some sort of advantage that AI cannot match. Fair enough. In that case, it makes sense for ship designs to cater to the needs of the crew, while missiles can dispense with all that. In other settings, this might not be so true. In real life, it almost certainly won't be true.

I think you make an error in the second paragraph, however, by conflating range with delta-v (ie, "change in velocity", or acceleration). The missiles need enough fuel (propellant) to match their target's evasive maneuvers and still have enough mass and/or relative velocity left over to do significant damage (the more of a velocity advantage the missile has over the target, the less mass it needs to do the same mount of damage). Meanwhile, "cruising" requires no more delta-v than is needed to accelerate to the desired velocity, and from there the ship can coast without using any fuel at all, unless it needs to correct its' course for some reason. Whether the ship needs more delta-v to complete its' patrol or the missiles need more to catch the target (which will frequently be an enemy ship cruising on its' patrol) will depend on specific circumstances. I can even see a trade-off where the launching ship's delta-v could be maximized at the expense of the missiles, or the reverse, depending on the mission. This is where using missiles as a back-up source of thrust might come in useful.

I would suppose that in general, to the extent that the target's point defenses are strong (whatever form that takes in a given setting), the less of an advantage delta-v will be for the ship, and the more advantage it will be to give it over to the missiles. This is because the missiles will need that delta-v in order to evade the point defenses and catch the targets (this may take the form of a large number of small missiles which nevertheless add up to a significant amount of the total delta-v). On the other hand, to the extent that the enemy's point defenses are weak, the more advantage will be derived from putting that delta-v into the launching ship's main drive, because getting within range and acquiring an advantageous launching position will be the main challenges (this may take the form of a small number of relatively larger missiles which add up to a reduced fraction of total delta-v).

As you can see, the number of missiles, and the size of the missiles, is a trade-off that complicates the issue. The real underlying question is where the delta-v budget is to be spent: is it to be made available mostly to the missile drives, or to the ship's drive?

"Small ship/large missile" is a design that will likely be most advantageous when in a positional disadvantage against an enemy ship larger and more capable than one's own (because giving the missile as much delta-v as possible is the only chance of hitting it). If humans were to go up against the Loroi, they would be well advised to deploy very large missiles in the hope that the wreckage will manage to intersect the enemy despite their advantage in point defenses (actually, I would advise them to develop an FTL missile, and start lobbing across the lightyears).

"Large ship/small missile" sounds to me more likely when in a positional advantage with better ships than the enemy has. Maneuver circles around them, and pick them off with cheap missiles. This is the Loroi against the humans (they need to get into human inhabited space as soon as possible to force the enemy to engage with their inferior vessels).

But really, the underlying question is still where should the delta-v go within the "ship-missile system"? Do you invest primarily in the ship, or in the missiles (bear in mind that the ship must carry the missiles until they are fired)? And what are the consequences of making a mistake? Again, this is where having some options (such as converting the missiles into back-up thrusters) might be helpful.

Alright.

Ever shined a laser at a wall in the distance? Did you notice that the laser dot grows bigger with distance?

That is exactly the problem with small barrel lasers, the laser beam spreads out faster reducing damage the smaller the lens is.

The larger the lens not only can you focus farther, the more heat it can take withut breaking... which is another problem with lasers.

They are hardly an efficient weapon, they make an awful lot of waste heat for whatever damage they do manage to do.

My point was that if a missile is the size of a ship, a small laser is unlikely to stop it.

By the time the giant missile reaches effective laser range it will still take a LOT to kill it.

Why? Forget every space battle you ever saw on scifi TV shows.

Space combat at long range is NOT three dimensional.... it is more or less 2-D at long range.

At such long ranges the only part of the ship the laser will hit is the part facing it, not the bottom or top and certainly not the back.

A giant missile can carry spare sensors, and rotating forces a laser to spread it's energy overthe whole, negating the concentration of laser energy on a single point.

Demarquis
Posts: 452
Joined: Mon Aug 16, 2021 9:03 pm

Re: A Question Of Maneuverability

Post by Demarquis »

Yes, I know, it's called "beam divergence" and it is indeed a function, among other things, of the objective lens diameter. For any given beam with some divergence limited effective range, that range can be extended by overlapping the circular "spots" as they appear on the target. And lasers are, at least in comparison with kinetic rounds, rather energy inefficient. But terms such as "small" and "a lot" are inherently subjective, the exact size of objective lens and beam power needed to sufficiently damage a missile of a given size at some range will depend on the tech in use.

There are, of course, various countermeasures that one could design into a missile to try and protect it from a laser, but those come at a cost in both complexity, mass and, well, cost. Put enough heat into a missile and it may not matter what countermeasure it uses.

Dahak
Posts: 44
Joined: Thu May 21, 2015 12:09 am

Re: A Question Of Maneuverability

Post by Dahak »

Bamax wrote:
Sun Feb 13, 2022 3:20 am
IRL bigger missiles are better, even ship-size missiles. Why? Because fuel/propellant is finite and space is virtually infinite, the more you have the farther you can maneuver.
This leads to the Gamilon Proton Missile and Tug:

Image

Post Reply