Kinetic Kill Bombs

[McPerth]

The Missiles special supplement introduced the rules for relative vector adding to the damage of a contact hit.

Well, Kilemall talked about Mayday, and the fact in Mayday missiles don't need to roll for hiting, they just explode if they reach their target without being blown away by point defense/ECMs, again makes me think they are proximity fuses...

Yes, but that is just silly...]|

I'd say just wrongly phrased, not really silly...

So if the ship is moving away from the missile, more hits.
If the ship is moving towards the missile, damage is reduced, contrary to any logic.
Example: The target ship is moving at 1000 mm/turn at 0°. The missile is approaching from behind at 1100 mm/turn at 0°. Real relative speed is 100 mm/turn. Calculated impact speed is 1000 + 1100 = 2100 mm/turn. Silly.


Better would be to do something like Impact speed = |V_missile| + |V_target| × cos φ, where φ is the angle between the vectors.

Or at least Impact speed = |V_missile - V_target|

Too complex for my taste, s it would probably need a calculator (and, by the way, how would ange be used in your formula)?).

Wouldn't be easier just to say the substraction of the two vectors (remembr that if they are opposite, subtracting them adds the speeds)?

As you're playing with vectors representing them with past and future positions, with a simple set square from any drawing kit you can easily calculate the linear vector to be added or subtracted, not needing a calculator...

(note: I hope I explained myself good enough, though I'm far from sure about it)

 

[kilemall]

Assuming Mayday comes directly from LBB2 Ship Combat System (or more exactly my reference will be from TTB, page 76), see that (underscoring is mine):



As I understand it, this hints that the missiles are proximity fuses detonated, not really coming to true contact with the target before exploding (as explosive anti-air projectiles ,that fill the area with shrapnel instead of expecting to explode in contact with the airplane). I'm not an expert with explosives or missiles (to say the least), but I guess if the missiles are not contact fused the relative speed is irrelevant, or at least its effect severely reduced.

That's how SS3 has it, the warheads are a set value depending on size, whether they are directed energy or nuclear, which is set for proximity detonation.

Contact requires DIRECT contact, in which case the combined vee of target and missile combine to valuate hits. It can be easily 10+ more hits.

 

[kilemall]

AnotherDilbert, poor wording. Like that has ever happened before in any Traveller rules. :CoW::rofl:

The intent and formula is simple- take missile speed G/3, add target speed G/3 if moving towards missile or subtract target G/3 if moving away from missile, round down and apply that sum as hits.

And before anyone comes in and says G is accel/decel value not a speed valuation, technically you're right, but it is a VERY handy way to express speed in terms of how much it would take to catch up or decel.

 

[AnotherDilbert]

Or at least Impact speed = |V_missile - V_target|

Wouldn't be easier just to say the substraction of the two vectors (remembr that if they are opposite, subtracting them adds the speeds)?

That's what I said?

That is still a rather rough estimate of impact speed, since speed perpendicular to the impact vector doesn't really add to the Bang.

 

[AnotherDilbert]

And before anyone comes in and says G is accel/decel value not a speed valuation, technically you're right, but it is a VERY handy way to express speed in terms of how much it would take to catch up or decel.

Yes, it is handy. But if you say Gturn† when you mean speed and G when you mean acceleration, it is much easier to keep everything straight, both for yourself and the reader.

† 1 Gturn = the speed you get when you accelerate at 1 G for 1 turn. See TNE.

 

[mike wightman]

Well, Kilemall talked about Mayday, and the fact in Mayday missiles don't need to roll for hiting, they just explode if they reach their target without being blown away by point defense/ECMs, again makes me think they are proximity fuses...

Missiles do have to roll to hit in Mayday.

The attack table is then consulted, and if a hit results, the damage table is consulted twice for proximity missiles and three times for contact detonation.

 

[AnotherDilbert]

AnotherDilbert, poor wording. Like that has ever happened before in any Traveller rules.

It's really more than poor wording.

Example: A ship moves with a speed of 1000 mm/turn (10 Gturns) at 0°. A missile approaches from the side with a vector of 300 mm/turn at 90°. Real impact speed is 300 mm/turn. Calculated impact speed is √( 300² + 1000² ) ≈ 1044 mm/turn. Again a silly result.

 

[mike wightman]

Yes, but that is just silly...


So if the ship is moving away from the missile, more hits.
If the ship is moving towards the missile, damage is reduced, contrary to any logic.
Example: The target ship is moving at 1000 mm/turn at 0°. The missile is approaching from behind at 1100 mm/turn at 0°. Real relative speed is 100 mm/turn. Calculated impact speed is 1000 + 1100 = 2100 mm/turn. Silly.


Better would be to do something like Impact speed = |V_missile| + |V_target| × cos φ, where φ is the angle between the vectors.

Or at least Impact speed = |V_missile - V_target|

You need to brush up on your understanding of vectors.
If the ship and the missile are heading in the same direction then the relative velocity vector is low, if they are heading in different directions the relative vector is high.

<----ship<-------missile = <--- relative so three extra hits
---->ship<-------missile = -----------> relative so 11 extra hits

 

[mike wightman]

It's really more than poor wording.

Example: A ship moves with a speed of 1000 mm/turn (10 Gturns) at 0°. A missile approaches from the side with a vector of 300 mm/turn at 90°. Real impact speed is 300 mm/turn. Calculated impact speed is √( 300² + 1000² ) ≈ 1044 mm/turn. Again a silly result.

Again, if you plot it graphically you get the right result.
I really wish we could talk face to face about this because a few seconds with a piece of paper and plotted vectors show what is meant to happen.

 

[AnotherDilbert]

You need to brush up on your understanding of vectors.

Quite possible.

If the ship and the missile are heading in the same direction then the relative velocity vector is low, if they are heading in different directions the relative vector is high.

<----ship<-------missile = <--- relative so three extra hits
---->ship<-------missile = -----------> relative so 11 extra hits

The text says add the vectors:
<-------missile + <----ship = <----------- silly
<-------missile + ---->ship = <--- silly

If we instead subtract the vectors we get a better result as you showed:
<-------missile - <----ship = <--- relative so three extra hits
<-------missile - ---->ship = -----------> relative so 11 extra hits

But if we use perpendicular vectors that does not work well either:

^             ^
|              \
|  -  --->  =   \
|                \

The perpendicular vector does not add to the impact speed, so should be ignored.

 

[mike wightman]

Perpendicular hit all you need to worry about is the size of the missile vector, although technically you are correct, you should solve for the length of the hypotenuse, and that becomes the additional damage.

And I agree that the wording is poor - you don't add the vectors you work out the relative vector, which is easy if you have it all mapped out on your game table.

 

[AnotherDilbert]

Again, if you plot it graphically you get the right result.
I really wish we could talk face to face about this because a few seconds with a piece of paper and plotted vectors show what is meant to happen.

Yes, face to face would be simpler.

But we can still write something:
V_missile = [x=3,y=0,z=0]
V_ship = [x=0,y=10,z=0]
The missile approached from the side at exactly 90° for simplicity.

V_missile - V_ship = [3,-10,0]
The length of the vector is √( 3² + (-10)² ) ≈ 10,44
But that is not correct, the impact vector is only 3 long.

Please show me where I went wrong.

 

[McPerth]

Missiles do have to roll to hit in Mayday.

You're right, my fault. That's what happens when one speaks on memory...

 

[AnotherDilbert]

Perpendicular hit all you need to worry about is the size of the missile vector, although technically you are correct, you should solve for the length of the hypotenuse, and that becomes the additional damage.

And I agree that the wording is poor - you don't add the vectors you work out the relative vector, which is easy if you have it all mapped out on your game table.

If we want to ignore the perpendicular part of the ships vector, we have to project the ships vector onto the missiles vector and then subtract, or with other words:
Impact speed = |V_missile| - |V_target| × cos φ, where φ is the angle between the vectors.


I wrote that wrong last time, a few pages ago: Impact speed = |V_missile| + |V_target| × cos φ, the magnitudes should be subtracted, not added. As the angle becomes larger than 90° the cosine becomes negative and the magnitudes are added, as it should be. I hope.

 

[mike wightman]

Your calculation is correct.
In the real world it is all about energy transfer, so if you walk into the side of a train when the train is doing 100mph you die, whereas if you walk into a wall you bounce off.

 

[AnotherDilbert]

Your calculation is correct.
In the real world it is all about energy transfer, so if you walk into the side of a train when the train is doing 100mph you die, whereas if you walk into a wall you bounce off.

I suspect it matters a great deal exactly who hits who, and with what.

If the side of the train is "perfectly smooth and frictionless" the energy transfer would be minimal, and you would bounce off just like the wall. A real train side would transfer some energy to you. If the train hit you straight on a lot more energy would be transferred to you.


In the case of a missile I would guess it depends a lot on if we penetrate the targets armour or not. If we bounce off the armour the perpendicular speed would not matter much, but if the missile penetrate into the target the perpendicular speed will matter a great deal. But since the missiles are like HE or HEAT, and not solid penetrators like DS, I guess the perpendicular speed will not matter all that much.

Except for the OP that uses solid penetrators, for him the perpendicular speed should probably be included.

 

[kilemall]

I suspect it matters a great deal exactly who hits who, and with what.

If the side of the train is "perfectly smooth and frictionless" the energy transfer would be minimal, and you would bounce off just like the wall. A real train side would transfer some energy to you. If the train hit you straight on a lot more energy would be transferred to you.


In the case of a missile I would guess it depends a lot on if we penetrate the targets armour or not. If we bounce off the armour the perpendicular speed would not matter much, but if the missile penetrate into the target the perpendicular speed will matter a great deal. But since the missiles are like HE or HEAT, and not solid penetrators like DS, I guess the perpendicular speed will not matter all that much.

Except for the OP that uses solid penetrators, for him the perpendicular speed should probably be included.

Armor, another one of my issues, and the HG table sliding value to me doesn't do the design tradeoff justice.