Smart missiles and line of sight

[Chas]

Question: what happens when a target moves out of sight of launched missiles?

For example you've launched a bunch of missiles at a fighter, when then ducks behind an asteroid. The smart missiles follow the fighter? For how long, i.e. the missiles curves around the asteroid, nothing to see in the first turn and has to give up?

Similarly what happens when a fighter ducks behind a covering dreadnought? The missile and the fighter start playing ring a ring a rosie about the big ship? Might be a valid tactic to shake off missiles were the big ship's PD can hit a closely circling missile?

 

[AnotherDilbert]

A missile that has accelerated for a few rounds has a staggeringly massive velocity vector, it simply cannot turn around obstacles.

But that applies to you too. To stay behind an obstacle you have to stop completely close to it. You cannot stop on a dime, if you have accelerated for 20 min, it will take you 20 min (and thousands of km) to stop. Speeds in Traveller are mindboggling. If you accelerate at 9G for 6 s you have a velocity of ~2000 km/h, after 6 min ~100 000 km/h, and you have no brakes or steering.

Realistically, in combat, you can only hide behind cooperating ships you are flying in formation with. And if you do that you should be immune to missiles, beam weapons, and electromagnetic sensors alike. So hiding fighters behind battleships should be a thing...

 

[phavoc]

'smart' missiles should be smart enough to figure that out. Missiles would have a smaller turning radius than a small craft. And with no atmosphere to go against, they should always win the turn game.

A more relevant question becomes, how long would they do ring around the asteriod before giving up and making the mechanical decision that they 'missed' and then self-destructing. Fired at long range I'd say the odds are more likely. Fired in say a dogfight situation, I'd say not so much.

 

[AnotherDilbert]

'smart' missiles should be smart enough to figure that out.

Agreed. If they see you hide they know where you probably are. That doesn't necessarily mean they can turn quickly enough to hit you.

Missiles would have a smaller turning radius than a small craft. And with no atmosphere to go against, they should always win the turn game.

No, not at speed. A battleship, a destroyer, a small craft, or a missile that has accelerated for 30 min will take 30 min to turn 90 degrees (or stop). A missile might gain a few seconds because it can swivel around its axis quicker, but to turn the velocity vector they all have to accelerate.

A more relevant question becomes, how long would they do ring around the asteriod before giving up and making the mechanical decision that they 'missed' and then self-destructing. Fired at long range I'd say the odds are more likely. Fired in say a dogfight situation, I'd say not so much.

Fired at Long range the missile cannot turn around the asteroid at all. It has travelled 20 000 km at max acceleration and will take more than 20 000 km to turn its velocity 90 degrees.

A missile in dogfight where it has not built up any velocity is extremely manoeuvrable.

 

[phavoc]

'smart' missiles should be smart enough to figure that out.

Agreed. If they see you hide they know where you probably are. That doesn't necessarily mean they can turn quickly enough to hit you.

Missiles would have a smaller turning radius than a small craft. And with no atmosphere to go against, they should always win the turn game.

No, not at speed. A battleship, a destroyer, a small craft, or a missile that has accelerated for 30 min will take 30 min to turn 90 degrees (or stop). A missile might gain a few seconds because it can swivel around its axis quicker, but to turn the velocity vector they all have to accelerate.

A more relevant question becomes, how long would they do ring around the asteriod before giving up and making the mechanical decision that they 'missed' and then self-destructing. Fired at long range I'd say the odds are more likely. Fired in say a dogfight situation, I'd say not so much.

Fired at Long range the missile cannot turn around the asteroid at all. It has travelled 20 000 km at max acceleration and will take more than 20 000 km to turn its velocity 90 degrees.

A missile in dogfight where it has not built up any velocity is extremely manoeuvrable.

I agree with all your points above. But that concept of built-up movement (or as I like to call them G-turns) does not factor into the rules, at all, for starships. So, from the game universe perspective at least, if you've been accelerating for two days, you instantly reset your acceleration to zero when combat begins in round 1.

 

[PsiTraveller]

Here we are in more space opera vs science fiction. With M-Drive you are not accelerating at a speed, you are moving at a speed and the speed does not build up. The grav turns of thrust and the km/s/s is not calculated. As Phavoc pointed out your calculation resets your acceleration to 0 each round. And how realistic are we wanting to be with floating cities and fusion plants inside small ships?

You are driving a car and can turn, stop and reverse whenever you want. This is the advantage of M-Drive and the lack of fuel it needs to operate. When debating this with my hardcore Classic Traveller friend. "M-Drives do not accelerate your ship, they clutch at the fabric of space-time and claw the ship along at a steady pace. When you stop clawing, movement stops." This hand waves the impossibility of the physics away in a single sentence and allows the Reaction Drives to slide the ship along faster by pushing those handholds along the rails of space time while the Gravitic control the M-Drive represents prevents crews from getting crushed at 3-15 G's of acceleration. Does it make sense with our understanding of physics? Heck no! Do I care? Hell no! I just want to have fun with my friends and wave away the acceleration equations and g-loading of structural members with "gravitic technology' that allows control of the local g-environment.

The understanding of the gravity particle allows for weaponized gravity distortion but the local control of basic systems prevents the occupants from being crushed to paste, instead they float around in zero g thanks to their grav plates. (pg 76-77 of Core book)

So now the 90 degree turns and zipping along around asteroids is acceptable and possible. Any sufficiently advanced technology is indistinguishable from Magic says Mr. Clarke.

The emphasis is on the fiction side of the science fiction adventure. The harder the science the more calculations and spreadsheets you will need, which may be great for some players ( one of mine included), but not for all.

 

[AnotherDilbert]

Ah, interesting point of view. I have assumed that Newtonian physics works as usual, and that the extremely simplified Core combat system tries to simulate that, but be much simpler,

I think the Travel Calculations [Core, p152] assumes normal Newtonian physics.

All of these formulae use kilometres ..., and assume the ship is undertaking a journey from rest, that it accelerates continuously to midpoint of the trip, then decelerates to rest again.

I guess we have to hope someone semi-official can give us some advice...

 

[PsiTraveller]

I use the Horst Conrad impeller concept from Heinlein's Starman Jones.

I freely admit I use the travel times as a time delay for activity and say it takes x amount of time to get from A to B and ignore the physics. Maybe the ships CAN accelerate Newtonically when going between planets, and use the 0 accleration M-Drive capabilities when in combat because making 90 degree turns without the pilot turning to paste is a huge tactical advantage for combat.

But if we go down the Hard science route then we end up with 500 000 ton planetoid ships being accelerated to near light speeds used as kinetic planet killers and smashing into worlds like massive Ortillery weapons. Or scaling it down and using the Honor Harrington as an example again, C-fractional missiles coming in from the outer system targeting Orbital facilities. (Flag in Exile pg 363). David Weber uses the Warshowski Sail technology for acceleration to insane speeds with crew protection from the gravity bands. Good reading. And in a few instances the protection fails and the crew is crushed instantly.

 

[wbnc]

Ah, interesting point of view. I have assumed that Newtonian physics works as usual, and that the extremely simplified Core combat system tries to simulate that, but be much simpler,

I think the Travel Calculations [Core, p152] assumes normal Newtonian physics.

All of these formulae use kilometres ..., and assume the ship is undertaking a journey from rest, that it accelerates continuously to midpoint of the trip, then decelerates to rest again.

I guess we have to hope someone semi-official can give us some advice...

one problem with those flight time charts...they treat target and destination as static points. and your flight plan as a straight line.

They are assuming you aren't playing fancy trick with relative velocities, and using such techniques as Gravity braking/assist. And that you are travelling in a straight line between the two objects.

applying that to a missile chasing a fighter..if the fighter pilot flies so he approaches close to to an on object he doesn't have to orbit it to use it for cover..all he has to do is make a rather mild lateral shift to bring the object between himself and the missile. He only has a big problem if he tries to change hims velocity on his "Y" axis...which means he has to burn a lot of energy to change his previous path of travel

However he doesn't have to burn as much energy to change his X, Or Z axis. so if he has 12 gees execute a 12 gee burn along his x axis and produce a much larger change in position tan he can by using 12 gees along his y axis...he doesn't have to overcome any inertia along his x axis...well at least until he wants to reverse that vector change at which pin he has to bur 12 Gees just to stop his movement along he x axis.

of course he could burn 12 gees, slide along his x axis for a few second flip over burn 12 gees of force, and arrest his acceleration along his x axis.He'd e bouncing around in his cockpit like a rag doll under the radical acceleration shifts..and still be moving at original velocity along his y access but his lateral position has changed radically in a few seconds.

Since once locked on a missile isn't looking for ANY target it is looking for a Specific target a pilot could potentially confuse the missile with some fast maneuvers. basically as son as he has cover he can try a pilot, or electronics check to spoof the missile using maneuvers, or electronic warfare to fool the missile into thinking he isn't it's proper target.

however I would also have to say, that a smart missile which has lost it's intended target could always go into search mode to find a similar target to go after...which does allow for the possibility of it going after the fighter that just eluded it completely by chance....

 

[phavoc]

If only we used stutter-warp, or reactionless drives... none of this would be an issue! No grappling with constant accel/turnover/constant decel worries.

But we are stuck with one thought process for calculating travel times (hence actual movement) and a completely different one for space combat. A flaw that has dogged Traveller since the beginning.

As for a mssile not being able to keep up with a maneuvering fighter... yes, and no. It is easy enough to build a fighter with thruster nodules spread along it's axis so that it is just as maneuverable as any small craft. And, conceivably, it's thrust-to-mass ratio should be far superior to that of a spacecraft. A missile can pull insanely high g-forces and not care, whereas a manned craft is still limited by... man.

If it is that easy to avoid a missile, what you would find is missiles that are stand-off attack missiles so that the ship itself is hit by a bomb-pumped shot rather than an actual direct hit, or even a proximity detonation.

I would suspect, with the defenses like nuclear dampers being deployed by ships, that all torpedoes would be stand-off attack weapons. And actual torpedo-to-hull hit should be staggeringly damaging, since ALL of the energy is being directed onto the targets hull. Point defense lasers (and where are the counter-missiles... crap, we have those today!!!) should be chewing the hell out of missile swarms.

 

[AnotherDilbert]

We have M-Drives: (Magical) reactionless thrust. No problem.
The difference between vector movement, and simplified combat movement is only in MgT. CT Book2 used vector movement in combat (sadly).
We have always have inertial compensators in Traveller, as the limit to acceleration.
We have bomb-pumped torpedoes. No problem.
A 25G fighter should easily avoid a 15G missile as long as it is free to manoeuvre. There is always something you have to choose not to see...

 

[phavoc]

We have M-Drives: (Magical) reactionless thrust. No problem.

Well, it depends if you are looking at non-combat movement (Newtonian), or combat (reactionless).

A 25G fighter should easily avoid a 15G missile as long as it is free to manoeuvre. There is always something you have to choose not to see...

Noooo! Say it isn't so!

 

[AnotherDilbert]

We have M-Drives: (Magical) reactionless thrust. No problem.

Well, it depends if you are looking at non-combat movement (Newtonian), or combat (reactionless).

I must be missing something. M-Drives have always (almost) been reactionless thrust leading to Newtonian motion. I do not think there is any way to get constant velocity in space according to physics?

 

[PsiTraveller]

I must be missing something. M-Drives have always (almost) been reactionless thrust leading to Newtonian motion. I do not think there is any way to get constant velocity in space according to physics?

According to our understanding of physics right now. M-Drive may work on a branch of physics we have not discovered yet. The control of the gravity particle in conjunction with the flux capacitor and the turbo encabulator makes for easy constant velocity, zero acceleration movement.

And a 25 thrust fighter will get hit by a thrust 15 missile if in close enough range from launch according to the rules. If there is flight time involved then the fighter could outrun the missile, but if launched from Medium range the fighter gets hit according to the rules. It ends up being about the phases.

 

[phavoc]

We have M-Drives: (Magical) reactionless thrust. No problem.

Well, it depends if you are looking at non-combat movement (Newtonian), or combat (reactionless).

I must be missing something. M-Drives have always (almost) been reactionless thrust leading to Newtonian motion. I do not think there is any way to get constant velocity in space according to physics?

Nope. The rulesets rarely go into the details. Rather you get a little here and a little there. If you look at the charts for say Earth to Jupiter style travel, it says you have a turnover. Turnover implies full newtonian movement. Also the new rules agree with the CT premise that you retain your velocity and heading upon exiting jumpspace that you had going in. More newtonian movement.

 

[AnotherDilbert]

According to our understanding of physics right now. M-Drive may work on a branch of physics we have not discovered yet. The control of the gravity particle in conjunction with the flux capacitor and the turbo encabulator makes for easy constant velocity, zero acceleration movement.

Made from Unobtainium and Handwaveium no doubt.

I prefer SF at least slightly hard, your mileage may vary...

 

[AnotherDilbert]

applying that to a missile chasing a fighter..if the fighter pilot flies so he approaches close to to an on object he doesn't have to orbit it to use it for cover..all he has to do is make a rather mild lateral shift to bring the object between himself and the missile. He only has a big problem if he tries to change hims velocity on his "Y" axis...which means he has to burn a lot of energy to change his previous path of travel

But if you just kinks a bit around the asteroid the missile can probably do the same. It's probably smart enough to keep track of roughly where you are and reacquire after passing the asteroid.

however I would also have to say, that a smart missile which has lost it's intended target could always go into search mode to find a similar target to go after...which does allow for the possibility of it going after the fighter that just eluded it completely by chance....

Quite, or a preprogrammed secondary target. But the simple system has to stop somewhere.

 

[wbnc]

applying that to a missile chasing a fighter..if the fighter pilot flies so he approaches close to to an on object he doesn't have to orbit it to use it for cover..all he has to do is make a rather mild lateral shift to bring the object between himself and the missile. He only has a big problem if he tries to change hims velocity on his "Y" axis...which means he has to burn a lot of energy to change his previous path of travel

But if you just kinks a bit around the asteroid the missile can probably do the same. It's probably smart enough to keep track of roughly where you are and reacquire after passing the asteroid.

however I would also have to say, that a smart missile which has lost it's intended target could always go into search mode to find a similar target to go after...which does allow for the possibility of it going after the fighter that just eluded it completely by chance....

Quite, or a preprogrammed secondary target. But the simple system has to stop somewhere.

Oh yeah you have a point...which is why I said he should have a CHANCE to maneuver , or EW his way out of trouble not automatigically shake the missile.

the trick would be to change your profile/signature until it is out of the missiles programmed parameters....

the real problme is that a missile would be pretty quick to go..Oh...I lot that one...Oh there is another one I can chase. If you're lucky it will go after something else.

 

[MongooseMatt]

Some very interesting points raised here, and if we were all running Traveller space combat on PCs, a lot of this might be incorporated.

However, we aren't, and we need to create a game that is simple, quick, does not stretch the brain too much (because we want to concentrate on the story, not physics - if you want the latter, try the degree I am currently studying, by all that is Holy!). So, yes, jumping behind a convenient rock will shield you from a missile. However, space is Very Large and, on this scale, Very Empty. The chance of a rock being in the right place at the right time (heading in the right direction, at the right speed) is not something I think we need in the rules.

You could have players saying they are hanging back near a rock and if any missiles come their way, they will just nip behind it - but the enemy knows that, and is going to take steps to prevent it/make it difficult/do something else entirely.

 

[Chas]

I was thinking the more likely situation was a fighter getting behind a ship of the line Matt. Say a situation where fighters are launched early, and then getting through distant and very long range still hanging around the battleships out of line of sight, much like soldiers advancing behind tanks or flitting out to fire their own salvos and then ducking behind the big ship, or fleeing from engagement and taking cover as it were behind the big ship with a missile on their tail...