KKM and Plasma Weapons

[TheEngineer]

Hi !

Just a short one regarding maneuverablitiy.
In vacuum its not a complicate to simply turn the KKM around its mass center and thus the main thrust direction, which in fact will lead to highly agile missiles.
Mathematically a missile with a significant higher g-rating and agility will always hit the target (well, assuming quite perfect sensor info).
The energy requirements of such a missile could indeed be fullfilled by a fusion rocket propulsion (there is a pretty reference for that in Hard Times). So we would not have to break some basic physical laws.

Anyway, against mobile targets I still do not see striking advantages for this type of weapon. So I would consider KKMs just to be another alternative, especially for static targets, to add some spice.
The ability to produce active anti KKM drones should be able to keep the balance.

Besides, think of a space battle zone with dozens of disabled KKMs moving around...

Regards,

Mert

 

[Scott Martin]

I apologize, I seem to have been spending far too much time pointing out that these will hit (and kill) anything that doesn't defend or maneuver: the same could be said for any large weapons system. My real goal is trying to figure out how to integrate this type of weapon into the existing rules framework (I'm aiming for TNE, since there is less "rebalancing" needed) but by explaining the underlying physics of this type of weapon anyone can adapt it for use in their system of choice. I'm thinking that we should start another thread if we wnat to talk about plasma weapons though

It has been pointed out that the easiest counter to a KKM is a (smaller, cheaper) anti-KKM KKM: I expect that this type of design (and implementation) will be easy enough to do once the "main" KKM structure is worked out (make it much smaller, payload of "sand" instead of "gravel" or "rocks")

A "de-tuned" PAW would probably also be effective against KKM's: 1 MJ/square meter covers a LOT of square meters for those larger weapons systems, so I could see them "sweeping" volumes of space clear of KKM's, ditto for some of the laser weapons. I'd also see some ability to use your drive plume as a

Ptah has a point with the average starship size though: You just won't see a lot of massive combat starships, since they die just as fast as small scouts if they are hit. That said, if you cover them with point defence it will be really hard to saturate their defences to *get* that hit. I'm not convinced that you will see a lot of "fighter" sized ships, because you just can't put very capable systems on a fighter: you may see a bunch of fighter-sized drones though...

By using T4 (and HEPLAR drives only) your "hard" limit on maximum velocity (for a 95% fuel ship) is well under relativistic velocities, not to be confused with *really* fast. I'm bringing this up so that we know we're not talking about the "C-fractional rock" (solution of choice for immoble targets) but instead the interactions implicit in a tactical starship combat weapon.

I will also apologize for not explicitly stating that you should not use KKM's with reactionless drives: KKM's are "balanced" in a universe where they must trade off endurance for high thrust. If you are usng reaction drives you can expect KKM's to be more maneuverable, but with much less total delta-V (their total change in velocity will be lower than your avearge starships totalchange in velocity, but it will be over a much shorter timeframe) Again, Ptah's concept of a low thrust high terminal velocity (1G all the way baby!) missile would be my suggestion for taking out static targets: here you are trading maneuverability for endurance.

And there is no issue with violating energy conservation laws maintaining constant accelleration at higher velocities: you have already sped the reaction mass up (with the fuel you have already used) so it's like you're using "more energetic" fuel at higher velocities.

I'll try to put up some "concept" KKM's in the next week or so: I'll do the work using FF&S (the original) but include the masses etc so that folks can tweak them into T4/FF&S-2 if they want to. Pass #1 will be single solid warheads only (since I'm still working on the bursting charges and dispersion mechanics for submunitions: suggestions maniacally er I mean cheerfully recieved)

I'll also put together some 1G "Super Slugs" for use against static targets: Only you can answer the question "do they go *PTAH* when the obliterate their target?"


Scott Martin

 

[Ptah]

In vacuum its not a complicate to simply turn the KKM around its mass center and thus the main thrust direction, which in fact will lead to highly agile missiles.

Yes, I forgot about that. Is there a limit to this? That is, does this manuever put any stress on the missile, particualiry the ends? To maintain my newly acquired position that KKM=bad mojo How fast can this flip manuever be performed and how far will the missile travel before it is done? We're probably talking fractions of a second here, but also at the velocities we have in mind it could still end up being pretty far.

Mathematically a missile with a significant higher g-rating and agility will always hit the target (well, assuming quite perfect sensor info).

Yes, we all are assuming perfect sensor info and perfect steering.

I guess that's the next phase, what kind of sensors can you get on one of these KKMs.

The energy requirements of such a missile could indeed be fullfilled by a fusion rocket propulsion (there is a pretty reference for that in Hard Times). So we would not have to break some basic physical laws.

Interesting. I've don't have any TNE stuff so I'd be interested in seeing the designs that come out.

So let me see if I can sumamrize it here.
(1) With equal G and agility you are not going to be able to dodge the KKM assuming the KKM has perfect sensors and steering (i.e., it can put itself where it needs to go within the relevant error margin).

and

(2) A reaction drive, e.g., a fusion drive can maintain sufficient manueverability and achieve sufficient velocities for a 1-hit kill on any size starship. Or are we still waiting on designs to see if all the stuff (drives + fuel + sensors) can be put in a missile size package and achieve these results?

 

[Scott Martin]

I have existing HEPLAR driven missiles at tech 13 that have a thrust of 16 G's and 8 g-hours of thrust, carry a 90,000 KM PEMS array, a 1,000 AU laser (for infinite range control by an operator to get it "close" and a 500 Kton laser head.

This uses the existing FF&S system, and fits in the same space that a "standard" missile fits in, so the "feasability" is not an issue. Slamming this into your ship at an average closing velocity of 12 hexes/turn (the average relative velocity I *could* get as a KKm in most playtests I have used) gives lots of energy yield.

So this is *well* past the proof of concept for "can you build this in FF&S"

The main problem is that the Nuke warhead is the most expensive component...

Scott Martin

 

[Fritz_Brown]

Originally posted by Scott Martin:
Think of the threat volume of my missile as a cone with the point away from your ship, and the avoidance area that your ship can maneuver into is a ball (sphere). If the sphere is completely within the cone, you can't avoid the missile, and I can prove mathematically that this is *always* the case unless you have more thrust than I do, as long as my start vector is pointing at the target. (since I fired the missile *at* you in the first place, for the vast majority of cases my start vector either intersects your ship, or isn't divergent enough to really matter)

The cone concept is a good analogy. But, you're wrong about beating a missile. A fighter can't outsprint a surface-to-air missile, but it most certainly can outmaneuver it, even if the missile can out-G the fighter. All the fighter has to do is break at the proper angle to the missile's flight path at the proper moment. The missile can't react quickly enough to close - it has to go outside the turn.

Even a KC-135R can't outsprint an air-to-air missile, but it most certainly can beat one. All I have to do is be in the right part of the envelope and know the missile has been fired, then it's actually a matter of having significantly more gas than the missile. I can even beat an air-to-air inside that envelope if I go to idle, enter a diving 180 turn, and push the engines back up halfway through the turn.

It sounds like movie theatrics, but it is actual tactics employed by IRL air forces.

Edit: I see my post is late. The above holds, though. And, I think you're going to have approximately the same differences in maneuverability due to size, etc. End edit

 

[Badbru]

Originally posted by Scott Martin:
I have existing HEPLAR driven missiles at tech 13 that have a thrust of 16 G's and 8 g-hours of thrust, carry a 90,000 KM PEMS array, a 1,000 AU laser (for infinite range control by an operator to get it "close" and a 500 Kton laser head.

This uses the existing FF&S system, and fits in the same space that a "standard" missile fits in, so the "feasability" is not an issue. Slamming this into your ship at an average closing velocity of 12 hexes/turn (the average relative velocity I *could* get as a KKm in most playtests I have used) gives lots of energy yield.

So this is *well* past the proof of concept for "can you build this in FF&S"

The main problem is that the Nuke warhead is the most expensive component...

Scott Martin

Infinate range? Check the rules again Scott I think you'll find you still need to apply a -1 Diff Mod per 10 hexes based on the time it takes to send the information backwards and forwards. The best range you could therefore get would be 600,000km using a TL15 MFD. You might argue the "firing task" is still based on range between the missiles onbord sensor and the target but the "controlling task" would still be based on launching/controlling vessels range to missile and/or target. Better to make it a fully autonomous system.
I need to re-read the heading and facing and turning rules of movement but the faster you go the more effort you need to expend in turning and if you are turning there are limmits on facing changes too. This has serious implications for your kkm if it is travelling significantly faster than your starship/spacecraft target. Most starships are less than 100meters in length and considerably less than this in height and width. Even merely lifting the nose 90degrees to the angle of travel makes a 45 meter long by 8meter high target reduce its profile by 37meters. When a miss of 1centimeter or more may aswell be a miss of 1000AU that 37meters obtained without even changing course or speed is a huge amount to account for for something travelling at 720,000klm per hour!
A non evading target the task to hit should be easy, a successfully evading target the task to hit should be improbable (impossible) an outstanding success result on evading should make kkm hits actually not possible.
It's a game, it needs balence. KKMs that inflict 500+ points of damage, whilst realistic, destroy game balence.

 

[Scott Martin]

Hi Badbru

most of the issues that you have raised are based on rules mechanics, not the Real World(tm) which is one of the reasons that integration is such an issue. To integrate these effectively I suspect that I will need to put together a hybrid of vector and hex-based movement, so on the "final" turn of movement (remember that missiles move last, to simulate the fact that they are "tracking" their target) calculate if the missile can reach the target based on current velocity vector and vector-based delta-V. If so, the relative velocity is (some large-ish number) and apply hideous damage unless counter-battery fire destroys the missile.

I'm still trying to iron out the counter-battery fire (since KKMs should be significantly easier kills than standoff laser heads, but making this assumption gives the laser heads a "free" shot)

For your comment on the control penalties, the -1 per 10 hexes comm difficulty is based on the *stock* laser communicator provided with a nuclear warhead. The laser comm is really just satisfying a rules requirement, since aparrently in the 43rd century people have forgotten how to build BOL (bearing Only Launch) guidance systems. Using FF&S to built the missile allows you to put a better reciever unint on the missile (and for this reason you need to put a (real) laser or maser comm with 1,000 AU range on the missile) I just wish that FF&S had power and mass requirements for *just* the reciever, but this way you also get a remote sensor platform (it can relay what it "sees" back to you)

Since (at worst) this is a SIM (semi-independant Missile) the actual attack telemetry will be provided by the on-board sensor suite, which is almost certainly more limited than that available on the launching vessel, so you don't take the -1 per 3 hexes diff mod increase (range at attack is *always* 0 hexes).

I notice that the rampart carries TL-15 FIM missiles (since it can't control missiles itself) but Brilliant Lances "forgot" to actually provide rules for them If you want to use FIM's assume that the asset target is equal to tech level (Tech 9 missiles are "green", Tech 15 missiles are "Elite" and Yech 21 missiles are "unholy")

Fritz makes some good points about "generating misses" within existing missiles performance envelopes: I suspect that this would (or should) be possible for a small high-thrust target (probably less than 100 Td) if the KKM does not carry submunitions, and basically improbable for any other situation. It is likely to be extremely bad for the pilot of said craft, since this is likely to be outside of the design parameters of the craft (including G-Compensation) but I like the idea of the "Hail Mary" switch to tell your onboard computer to kick you to double rated max accelleration on a random heading just before impact (total delta V of 30 meters for a 12G burn which would clear a *small* ship from the direct hit zone if the targeting computer took 1/2 second to analyze and react to the course change. Much less (by square law) for faster computer response)
This is where countermeasures would actually be useful, since 500 "Blinder" packages would cover you for that 1/2 second. For any vessel larger than tens of meters, this just isn't likely to work for three reasons:
1) because the moment of inertia of such a vessel will prevent it from quickly rotating on its axis
2) because of the need for the entire vessel to be clear of the impact zone
3) Big things are easier to pick out of jamming, especially if for no other reason than an "out of performance" drive plume is a *really* obvious target.


Scott Martin

 

[Ptah]

Scott,
I was able to find some FFS rules on the internet. They actually said they were for FFS2 with errata that correct the fuel requirements, whatever that means.

Using the HePLAR drive info I get the exhaust velocity for a 6G sprint for 1 hour to be about 1%c. Within reason, if not whithin current technological capabilities. The rules I found didn't have drives above 6G and I had to extrapolate down from a 100T vessel and assumed a 0.25T missile. This didn't seem to leave as much room as in your design example, but I bet there are different rules for missile design.

One question that I had was how can you fit a sensor on these things since the rules I found had a minimum length of hull for the sensor, nothing less than 5 meters. This all got me thinking, well if the missile doesn't have it's own sensors of sufficient range it can always be directed from a ship, albiet with a communication lag.

Then I thought of the drive. The missile is using a high energy plasma with an exit velocity of 1%c. This thing is putting out x-rays and light (EM) all across the spectrum (x-rays to radio waves) in addition to high energy particles and the plasma environment behind it. Electromagnetic communications, across the whole spectrum (not just radio-waves) are going to be a problem, not just because of the inteference plasmas cause with radio waves, but because of the light emitted by the drive itself. This will play havoc with laser communication as the light from the drive is likely to swamp the photon density of the comm laser signal. In addition, the x-rays from the drive are going to play havoc with the photon detector (i.e., receiver for the laser comm) generating spurious signals. In essence, guidance by laser comm, or other EM method from a certain arc behind the missile is likely to be impossible.

An alternative is guidance by craft in front of or to the side of the missile.

On a starship size scale, it's probably much easier to shield the sensors from the drives, e.g., you don't put your sensors only 2-3 meters from your drives. Shielding the front of a missile from x-rays might be more difficult as a certain minimum thickness of material is needed.

Another defensive idea, if guidance is an achilles heel of a missile, one way to defeat the guidance is to turn a laser on the missile. It doesn't need to be powerfull enough to physically damage it, just add noise/swamp the photon detector of the laser receiver on the missile.

Thinking of these things, I think KKM missiles would be more susceptible to missile defenses because lasers, etc. only need to interfere with or damage the guidance system. Absent accurate guidance, the KKM will probably find it very hard to hit a moving target.

 

[Ptah]

For any vessel larger than tens of meters, this just isn't likely to work for three reasons:
1) because the moment of inertia of such a vessel will prevent it from quickly rotating on its axis

A fighter with its lower moment of inertia might be able to pivot about its center-of-mass with simple thrusters. However, wouldn't a starship flip just as fast if one used HePLAR etc. type drives to flip it? I'd bet you have more than enough thrust to flip a battleship end for end. I haven't run any numbers, but I suspect the amount of thrust even small versions of these starship drives put out is orders of magnitude more than the moment of inertia.

The need to flip a starship is of course assuming they only have one or two primary drive directions. If a method is developed to vent drive plasma in multiple directiions, or you just mount more drives, there is no need to flip. Another aid in flipping is to mount small HePLAR etc. drives a distance from the center of mass (nacelles anyone ). Depending on how deadly KKM become, ship design may deviate from the closed approach and favor dispersed hulls such that the "center of the target" is an empty space.

 

[Scott Martin]

Hi Ptah

I was dropping by to mention that a fusion rocket is limited to a max accell of 9G by TNE rules, so it's approptiate to your "death slug" but not to my "sprint" missiles. Fusion rockets are a bit more fuel efficient than HEPLAR too

6 G's for 30 minutes is a velocity of 1800*6*10 meters per second (108 kilometers per second, 0.036% C) The maximum velocity from a 90% fuel ship in TNE is a little over 100 G-hours, or 3500 km/second which is just over 1%C (and now you can't slow down)

The drive signature is one of the reasons that I laugh at the idea of EMM (electromagnetic masking) being effective in TNE. Imagine the following conversation happenng on the bridge of a warship
________________

Captain:
"Damnit, we need to find that hostile before they launch on our planet! Can't you figure out where it is?"

Sensor Tech:
"No sir, we can't get a solid read on the target vessel, it's just disappeared! are you at all interested in that exhaust plume in the same area?" (points out the front window at a blindingly visible smear)

Captain:
"Of Course not! We need to find that ship, this is a life-or-death issue!"
__________________

The communication issue isn't as dire as it may seem: yes, the drive exhaust is going to hash radio reception, and will have a much higher photon density than that from a laser comm, but:
1) The laser is coherent, and the plasma interference is not
2) The plasma plume will be very tightly confined (your missile may need to "wiggle" periodically to get reception if its launching ship is *directly* astern, but 5 degrees of yaw for 2 seconds every 10 minutes won't affect it's course that much

A missile "kill" in TNE needs to do a single point of damage to a missile, so yes, they're fragile.

a passive sensor systemcan be mounted on an "overly small" platform like a missile IF it's a folding array (yup, it's legal, and you will see it on one of the stock SIM's in TNE)

I think that KKM's should be easier than laser-head missiles to defend against just because they *must* close to contact range to hit: a laser head must be engaged at ~15,000 km range, a KKM could probably be safely engaged at sub-5,000 km ranges (depending on the size and maneuverability of your ship)

KKM's are really scary because they are 1-hit 1-kill munitions, but anyone prepared for them should be able to sweep them out of the sky in droves: the trick is firing (droves +1) at the target With respect to Badbru, "game balance" tends to be important to simulate the real world, not the other way around: Guns unbalanced the dynamics of warfare, but only one country that I know of dealt with that unbalance by pretending that the problem didn't exist. (I believe that a fellow called "Perry" pointed out why ignoring the issue was a Bad Idea in 18th century)

That said, I suspect that in a combat between two equally sized ships, one beam armed and the other solely KKM armed, the beam armed ship will win. This is based solely upon my belief that the KKM armed ship won't be able to put enough missiles into space to swamp the point defence of the beam armed ship (the KKM armed ship is likely to be a lot cheaper though...) If the missile ship "seeds" its fire with laser heads then life gets "interesting" for the beam armed ship, since it would be forced to either accept hits from the lasre heads (and get all of the KKM's) or expand its engagement range (and run the risk of having its point defence overwhelmed)

Using "stock" TNE rules, the KKM armed ship will almost certainly get a hit in, but "stock" TNE rules assume missile engagement at 15,000 km.

On a "strategic" level KKM's *suck* because you're never going to get any salvage, loot, prisoners or useful equipment to reverse engineer from something hit by one of these.

Scott Martin

 

[Scott Martin]

Ptah:

Duh! Sorry *exhaust velocity* should be in the ballpark of 1-2%C (remember that LHyd is significantly lighter that the rest of the ship) but if you crunch the numbers to accellerate that fuel to 1.5%C (because that's how fast it *must* be going based on the impulse generated) you discover that the energy needed is significantly more than that provided by the powerplant, which I believe Mert (TheEngineer) had previously pointed out when he said that drives were "broken"

(end tangent)
Scott Martin

 

[Ptah]

The communication issue isn't as dire as it may seem: yes, the drive exhaust is going to hash radio reception, and will have a much higher photon density than that from a laser comm, but:
1) The laser is coherent, and the plasma interference is not

The coherent nature of the laser beam means you can certainly do better tricks with modulation, phase locking, polarization, etc. From personal experience these only go so far, baring a change in the physics of the detectors (laser comm receivers), a photon detector cannot descriminate between a photon from an incoherent light source from that from a coherent light source. Current detectors respond to the photon energy, the photon impinging on the detector material, energizing an electron in the material to create a signal. Detectors that respond to a photon are also going to generate a signal when hit by an x-ray. Enough x-rays and they will dominate your signal.

Duh! Sorry *exhaust velocity* should be in the ballpark of 1-2%C (remember that LHyd is significantly lighter that the rest of the ship) but if you crunch the numbers to accellerate that fuel to 1.5%C (because that's how fast it *must* be going based on the impulse generated) you discover that the energy needed is significantly more than that provided by the powerplant, which I believe Mert (TheEngineer) had previously pointed out when he said that drives were "broken"

So the power plant is the postulated particle acceleration mechanism? Not knowing exactly what HePLAR stood for I assumed the idea was the particles streamed off from a fusion reaction of some kind and the powper plant was used to provide energy for magnetic containment.
Is there a fix for this "broken" aspect of the drives?

 

[Ptah]

Captain:
"Damnit, we need to find that hostile before they launch on our planet! Can't you figure out where it is?"

Sensor Tech:
"No sir, we can't get a solid read on the target vessel, it's just disappeared! are you at all interested in that exhaust plume in the same area?" (points out the front window at a blindingly visible smear)

Captain:
"Of Course not! We need to find that ship, this is a life-or-death issue!"

 

[Badbru]

Originally posted by Scott Martin:
Hi Badbru

most of the issues that you have raised are based on rules mechanics, not the Real World(tm) which is one of the reasons that integration is such an issue. To integrate these effectively I suspect that I will need to put together a hybrid of vector and hex-based movement, so on the "final" turn of movement (remember that missiles move last, to simulate the fact that they are "tracking" their target) calculate if the missile can reach the target based on current velocity vector and vector-based delta-V. If so, the relative velocity is (some large-ish number) and apply hideous damage unless counter-battery fire destroys the missile.

My bad. I was under the impression you wanted to integrate kkms into the existing rules not rewrite the rules to more appropriately reflect your assesment of Real World (tm). One is not the other.


For your comment on the control penalties, the -1 per 10 hexes comm difficulty is based on the *stock* laser communicator provided with a nuclear warhead. The laser comm is really just satisfying a rules requirement, since aparrently in the 43rd century people have forgotten how to build BOL (bearing Only Launch) guidance systems. Using FF&S to built the missile allows you to put a better reciever unint on the missile (and for this reason you need to put a (real) laser or maser comm with 1,000 AU range on the missile) I just wish that FF&S had power and mass requirements for *just* the reciever, but this way you also get a remote sensor platform (it can relay what it "sees" back to you)

I'm not sure what you're trying to tell me here?
Surely it is not that an 1000AU laser comm as opposed to a 300,000km laser comm changes the speed a which that laser light will travel 300,000km or more?
Yes, if they both have 1000AU units they'll remain in "SHORT" range of each other, but check the RCV rules in FFS, I think is where it is, with regards to 10 hex dif mods.

Since (at worst) this is a SIM (semi-independant Missile) the actual attack telemetry will be provided by the on-board sensor suite, which is almost certainly more limited than that available on the launching vessel, so you don't take the -1 per 3 hexes diff mod increase (range at attack is *always* 0 hexes).

Yeah I granted you that arguement won. Those Dif mods wern't the ones I was talking about.

Fritz makes some good points about "generating misses" within existing missiles performance envelopes: I suspect that this would (or should) be possible for a small high-thrust target (probably less than 100 Td) if the KKM does not carry submunitions, and basically improbable for any other situation. It is likely to be extremely bad for the pilot of said craft, since this is likely to be outside of the design parameters of the craft (including G-Compensation) but I like the idea of the "Hail Mary" switch to tell your onboard computer to kick you to double rated max accelleration on a random heading just before impact (total delta V of 30 meters for a 12G burn which would clear a *small* ship from the direct hit zone if the targeting computer took 1/2 second to analyze and react to the course change. Much less (by square law) for faster computer response)
This is where countermeasures would actually be useful, since 500 "Blinder" packages would cover you for that 1/2 second. For any vessel larger than tens of meters, this just isn't likely to work for three reasons:
1) because the moment of inertia of such a vessel will prevent it from quickly rotating on its axis
2) because of the need for the entire vessel to be clear of the impact zone
3) Big things are easier to pick out of jamming, especially if for no other reason than an "out of performance" drive plume is a *really* obvious target.


Scott Martin

1)In Space? Thrust up from the bow attitude thrusters and thrust down from the stern attitude thrusters. How else does a ship turn?
2)The entire vessel doesn't have to get out of the way, just the targeted portion

The biggest difference of opinion we seem to have is the perceived agility of the missile. What I'm getting from you is that the missile only needs to be faster than its target to guarantee a hit, as it can easily change its course and heading to match any evasion the target performs. I don't see this as so easy to accomplish as it will have to burn g's to counter its own heading and velocity too and the faster you're going the harder that is. Explain to me the "inertia" of travelling at 720,000klm per hour.

 

[Scott Martin]

Hi Badbru

My plan is to rewrite as few rules as possible, especially since TNE / Brilliant Lances is a fairly clean system. I'll have to check into the current rules on remote vehicle ops: I was pretty sure that it was exactly the same 1 diff mod/3 hexes as everything else, and I haven't used them since it loked like an expensive way to build disposable targets (er I meant platforms)

Inertia is the same at 2 m/s and 2,000,000 m/s (well ok Relativity has a tteney influence in the latter, but not enough to notice...) Momentum is not (Moment of inertia was mentioned earlier to point out that while a missile can "spin" to pretty much any bearing it wants in a fraction of a second, a large starship that tries that will probably tear itself apart: yes, it can put in the energy to spin, but the centripital accelleration of a larger object will make a mess of the structure...

If I have a large vector towards my target (call it BIGHURT vector) that passes through the centerline of said target, and this target wants the missile to miss, it's most efficient evasion is anywhere in the plane at 90 degrees to that vector.

If the missile has more thrust than the target, then the missile will *always* be able to pull the (resultant) vector back on line with the target, and the magnitude of vector BIGHURT will not be reduced (I can probably put together a mathematical proof for this, but I'll give a concrete example instead)

Start vector (after tthe KKM has been boosting for a while) 10 kilometers per second towards the unfortunate target vessel

Target Vessel thrusts at 6 G for 10 minutes at an angle perpindicular to this vector

Missile thrusts at 6 G for 10 minutes at an identical vector

Resultant *relative* vector is still 10 km/sec through the target, resultant actual vector is 3600 m/s for the target, and (sqrt(3600^2 + 10,000^2)) at an angle that I could derive, but can't be bothered to.

This is the case in which Missile thrust = target thrust. If missile thrust is greater than target thrust then the missile will continue building velocity and the lateral vector component will match that of the target.

Light speed delay is irrelavant in any case where the missile has more thrust than the target, because the missile can adjust the vector as it closes (and the delay will reduce as it does so)

Light speed delay is *critical* if missile thrust is exactly equal to target thrust, since the target will pick a bearing and accellerate on it as soon as it notices it is under attack, and the missile can only pursue once it "notices" the course change. The missile will miss by (light speed delay + computation delay (tiny) x thrust x (time from target when the ship started thrusting)) AKA "who cares, it missed"

Light speed delay is again irrelevant if missile thrust is less than target thrust (the target will wait until impact - some arbitrary delay) and then use reaction mass to avoid impact.

Ptah: you'll have to give me a better idea how much detail you want on overcoming interference: I have a bunch of years optimizing mass spec and photospectrometer sensors. Were I to pick nits I'd personally bet that thermal issues would be WAY more of an issue than X-rays kicking your CCD, PMT's or Multi-layer solid state detectors. Medical equipment gets around this by having a metal grate over the detector array to ensure that "scattered" x-rays don't impinge on their detectors. That said, if your HEPLAR drive isn't X-ray shielded then you will already have cooked your control systems, and the energy levels of your drive output mean that you can't have significant scattaring of your exhaust plume. Unless you are trying to punch a signal directly into the drive of your missile (or within a couple of degrees therin) you should be OK with just putting the detector forward of the drive shielding. If you want to use handwavuim I'd point out that at Tech 13 (minimum for small HEPLAR missiles due to min reactor size limits) you get free electron lasers capable of focusing X-rays: the same technology will deal nicely with your interference problem. A lower tech solution would be a prism (or 3 or 5) of the appropriate geometry to divert just the wavelength of modulation to the detector.

I personally find it amusing that a communication laser with a 1,000 AU range only needs a 1 square meter antennae (any tech level) but weapons laser below tech level 13 is attenuated to uselessness by 1 LS with the same size antennae

I believe that the HEPLAR mechanism is very similar to that of a fusion rocket, but with a better acronym...

Anyway, I may be incommunacado for a few days (Family Xmas in middle of nowhere) but if so I'll try to put together the promised (threatened) first pass designs.

Scott Martin

 

[Ptah]

Scott

Ptah: you'll have to give me a better idea how much detail you want on overcoming interference: I have a bunch of years optimizing mass spec and photospectrometer sensors. Were I to pick nits I'd personally bet that thermal issues would be WAY more of an issue than X-rays kicking your CCD, PMT's or Multi-layer solid state detectors. Medical equipment gets around this by having a metal grate over the detector array to ensure that "scattered" x-rays don't impinge on their detectors. That said, if your HEPLAR drive isn't X-ray shielded then you will already have cooked your control systems, and the energy levels of your drive output mean that you can't have significant scattaring of your exhaust plume. Unless you are trying to punch a signal directly into the drive of your missile (or within a couple of degrees therin) you should be OK with just putting the detector forward of the drive shielding. If you want to use handwavuim I'd point out that at Tech 13 (minimum for small HEPLAR missiles due to min reactor size limits) you get free electron lasers capable of focusing X-rays: the same technology will deal nicely with your interference problem. A lower tech solution would be a prism (or 3 or 5) of the appropriate geometry to divert just the wavelength of modulation to the detector.

Hi Scott, seems we have the same background in detectors. Heat, man don't get me started on thermal problems with photomultipliers (or the wide variability/relaibility in manufacturer listed dark counts).

Luckily, I never had to face intereference on the level of a fusion drive.

The view that HEPLAR drives have a fairly confined tail readily solves a fair portion of the interference problem for me. Also TL13 means alot, there is probably a large degree of unobtainium out there that could solve interference problems. I still like the idea of using lower power lasers to "jam" an enemy kkm control system.

Looking back on my posts, just wanted to say that I'm not trying to be a nudge. I like where your going with this and also enjoying working with reaction drives a bit. Speaking of which...

...you discover that the energy needed is significantly more than that provided by the powerplant, which I believe Mert (TheEngineer) had previously pointed out when he said that drives were "broken."

I'd heard this before about TNE thrusters but not having the books never sure what posters meant. Finally, compared the total energy output from the PP to the KE of my quick test missile above, off by about a factor of 10 if it came from the PP alone. Without a doubt some energy deficit even if these rules are found are not the official ones.

Happy Holidays Scott, see you when you get back.

 

[Fritz_Brown]

One thought: reverse this concept, and make the KKMs stationary, using the velocity of the ships to impart the KE. A "dark body" ship sows a "minefield" near a battle, while the rest of the fleet manuevers the enemy into that field at high velocity (and accelerating to escape their pursuers).

Variation: passive sensors activate high-g, short duration, drives to plow a little extra KE into the target before contact.

 

[Scott Martin]

If you look here:
http://www.travellerrpg.com/cgi-bin/Trav/CotI/Discuss/ultimatebb.cgi?ubb=get_topic;f=4;t=000890;p=1#000000
you will find some sample HEPLAR missiles with laser heads, suitable for use in a TNE campaign.

Notice the unholy G-Ratings and endurance, and the fact that (with the exception of FIM's with exxtensive sensor packages) the costs of these weapons are mostly due to the warheads. Since I'm still a fan of the "expensive Gun, Cheap bullets" model of ordinance, this insane expense for warheads offends my sensibilities.

In any case, all of these missiles can easily impact at a hefty (30 hexes/turn+ AKA 500 km/second) velocity, most can readily make 1,000 kps and their unloaded mass (mass with no fuel) is in the Ton range. Delivered energy of the body of the missile (undetonated warhead, powerplant and drive) is *far* in excess of the contact explosion rating of any warhead available in the FF&S design sequences (Multi-Megaton range)

So now we have a "simple" comparison using canon-legal designs.

You should also now understand why I would just avoid using reactionless drives: for a ballpark estimate of a T4 thruster plate missile the missile size stays the same (thruster plates require 4x the minimum thrust) but thrust doubles (since thruster plates are double the "reaction efficiency" of HEPLAR) and endurance becomes unlimited.

Hey Fritz

Space is *big*
Even in the Harrington novels the "mines" were nukes, and thus had standoff range.

Your "variation" would work nicely though, and may be possible to do using chemical thrusters (which would be cheap and harder to detect / intercept on a short sprint)

I think that I'd seed them near a planet (or gas giant) since if my opponent needs to land troops (or refuel) he *must* go there, and this would stop any "hit and run" tactics dropping troops on the way by before reducing my naval forces.

Scott Martin.

 

[Fritz_Brown]

Well, Scott, space is a big place, but the vector for your opponent isn't. Imagine a couple of pirate ships converging on a single target (say, a customs cutter) and manuevering it into the rock field.

Or another variation: Get a ship to chase you. Manuever so that the pursuit will cut the angle to gain on you, right through the rock field.

The key to either version is to get the opponent to build a blazing velocity, so that a few thousand rocks scattered in his path is not gonna be pretty.

I really don't know if the transfer of KE is going to work, though, if the rocks are stationary and the really large mass of the ship is what's moving.

 

[Fritz_Brown]

And, BTW, I've got an idea for KKMs posted somewhere else around here (though that's not what I called them). It involves most of the initial velocity coming from a slow, silent acceleration by the launching ship, then a fast, hi-G burn with chemical rockets to achieve a wicked velocity. The idea is to take out bases and ships in parking orbits or large formations before the main force jumps in.

I've also posted my Meson gun mines somewhere around here - been a while, though. When combined with some other hi-TL defensive measures, yikes.