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Missile DPS and the Doppler effect

Author
James Amril-Kesh
Viziam
Amarr Empire
#1 - 2012-10-23 21:17:56 UTC
The Doppler effect as many of you know is a physics phenomenon where the perceived frequency of a traveling wave can be different depending on the relative velocity of the wave source and observer. It's what causes approaching police sirens to have a higher pitch which switches to a lower pitch when they pass you, and what causes astronomical objects to appear blue when approaching at high speeds or red when receding at high speeds.

I was in help chat one day answering questions when it occurred to me that missile damage is in fact a kind of wave, where pulses of damage (the missiles) travel through a certain distance at a finite velocity to reach a target. These pulses are emitted at a fixed frequency, but the distance between the attacking ship and the target is not fixed. If missile DPS exhibits a Doppler effect, missile DPS should be higher when the radial velocity between the two ships is negative (distance is decreasing), and lower when the radial velocity is positive (distance is increasing).

Let's take a 100MN HM Tengu, for example. I'll just use simplistic numbers here, instead of more exact values you'd find in EFT, to simplify calculation. We assume that missiles instantly reach their maximum speed just after being launched.

This particular ship is capable of flying at 2000 m/s, and does 500 DPS nominally (4 second rate of fire, 2000 alpha). The missiles travel at 8000 m/s, and we'll assume for simplicity's sake that they have infinite flight time. We'll also assume the target ship sits perfectly still. With the Tengu also sitting still, the target receives 500 DPS as you would expect (before resists and signature radius).

Things however appear to be different when motion is taken into account. Now we'll assume the Tengu is flying away from the target with a radial velocity of 2000 m/s. The formula for the observed frequency of a wave when the relative velocity of the observer and the emitter is not constant is f (observed) = (1 - v relative / v wave)*f (emitted). v relative is in this case the radial velocity. For the ships flying apart at 2000 m/s, the impact rate of the missiles is (1 - 2000/8000) * 1/4 = 3/16, or roughly 1 impact every 5.3333 seconds. With 2000 damage per hit, this causes an effective 375 DPS compared to the nominal 500. Seems pretty significant.

Now let's observe the case where the ships are flying closer with a radial velocity of 2000 m/s. The formula is f_0 = (1 + 2000/8000) * 1/4 = (1 + 1/4) * 1/4 = 5/16, or one impact every 3.2 seconds. 2000 damage / 3.2 seconds gives an effective DPS of 625. You've gained 125 DPS simply because you were flying straight at your target.


So my question to you is, do you believe missile DPS in EVE exhibits a Doppler effect, and have you ever noticed it?

Enjoying the rain today? ;)

James 315
Experimental Fun Times Corp RELOADED
CODE.
#2 - 2012-10-23 21:23:24 UTC
James Amril-Kesh wrote:
So my question to you is, do you believe missile DPS in EVE exhibits a Doppler effect, and have you ever noticed it?

I don't know, it's been years since I used any missiles. Smile
Roll Sizzle Beef
Space Mutiny
#3 - 2012-10-23 21:24:23 UTC
James Amril-Kesh wrote:
So my question to you is, do you believe missile DPS in EVE exhibits a Doppler effect, and have you ever noticed it?


As I'm pretty sure they only use base ship velocity when calculating explosion velocity. I don't believe it as I have not noticed it.
Surfin's PlunderBunny
Sebiestor Tribe
Minmatar Republic
#4 - 2012-10-23 21:24:35 UTC
James 315 wrote:
James Amril-Kesh wrote:
So my question to you is, do you believe missile DPS in EVE exhibits a Doppler effect, and have you ever noticed it?

I don't know, it's been years since I used any missiles. Smile


And miners usually hold still

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Jack Miton
School of Applied Knowledge
Caldari State
#5 - 2012-10-23 21:28:30 UTC  |  Edited by: Jack Miton
Congrats on attending maths classes in highschool.
Realistically the distances traveled between missile volleys is going to be insignificant for this affect but yes, you are correct.

There is no Bob.

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James Amril-Kesh
Viziam
Amarr Empire
#6 - 2012-10-23 21:28:34 UTC
Roll Sizzle Beef wrote:
James Amril-Kesh wrote:
So my question to you is, do you believe missile DPS in EVE exhibits a Doppler effect, and have you ever noticed it?


As I'm pretty sure they only use base ship velocity when calculating explosion velocity. I don't believe it as I have not noticed it.

It's not explicitly in the equations, no, but you have to understand that missile DPS isn't damage per volley divided by rate of fire, it's damage per volley divided by rate of impact, and as demonstrated above the rate of impact changes per the Doppler effect

Enjoying the rain today? ;)

Demolishar
United Aggression
#7 - 2012-10-23 21:30:44 UTC
So... make a cruise raven that can fly the speed of it's own cruise missiles. Start burning toward the enemy from 250km away while shooting missiles. Alpha anything?
Mallak Azaria
Caldari Provisions
Caldari State
#8 - 2012-10-23 21:41:23 UTC
That made my brain hurt. However, I have noticed this before. Perhaps CCP could confirm/deny?

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Bagrat Skalski
Koinuun Kotei
#9 - 2012-10-23 21:42:39 UTC
Never noticed it, probably it's too much work for hamsters. P
Demolishar
United Aggression
#10 - 2012-10-23 21:44:37 UTC
Mallak Azaria wrote:
That made my brain hurt. However, I have noticed this before. Perhaps CCP could confirm/deny?


Of course it exists.
Selinate
#11 - 2012-10-23 21:44:52 UTC
If missiles travel the same speed throughout flight, then if a ship is traveling towards another ship, the missiles should increase in the frequency of impact. I don't use missiles, but I have no reason to assume this isn't true based on knowing that missiles have a finite flight time (as opposed to instant like guns), and ship velocity changes the point of origin of the missile being launched...
Arduemont
Rotten Legion
#12 - 2012-10-23 21:56:52 UTC  |  Edited by: Arduemont
James Amril-Kesh wrote:
So my question to you is, do you believe missile DPS in EVE exhibits a Doppler effect, and have you ever noticed it?


I got bored of the maths, so I didn't read the last couple of paragraphs, but in short yes. Missiles work this way. Because you always start roughly at the centre of the explosion (because the explosion happens when the missile hits your hull), you are always travelling away from the explosion (so long as you are infact moving of course). The Doppler effect is why missiles do less damage to faster moving targets, and its the reason we have an "explosion velocity" stat for missiles.

Because for game purposes the explosion is always counted as being at the rough centre of your ship, travel in ANY direction creates your hypothetical redshift, and therefore less damage. All damage is calculated based on the explosion (even kinetic, oddly enough).

"In the age of information, ignorance is a choice." www.stateofwar.co.nf

James Amril-Kesh
Viziam
Amarr Empire
#13 - 2012-10-23 22:00:27 UTC
Arduemont wrote:
James Amril-Kesh wrote:
So my question to you is, do you believe missile DPS in EVE exhibits a Doppler effect, and have you ever noticed it?


I got bored of the maths, so I didn't read the last couple of paragraphs, but in short yes. Missiles work this way. Because you always start roughly at the centre of the explosion (because the explosion happens when the missile hits your hull), you are always travelling away from the explosion (so long as you are infact moving of course). The Doppler effect is why missiles do less damage to faster moving targets, and its the reason we have an "explosion velocity" stat for missiles.

Because for game purposes the explosion is always counted as being at the rough centre of your ship travel in ANY direction creates your hypothetical redshift, and therefore less damage. All damage is calculated based on the explosion (even kinetic, oddly enough).

That actually has nothing to do with what I said.

Enjoying the rain today? ;)

Arduemont
Rotten Legion
#14 - 2012-10-23 22:04:35 UTC  |  Edited by: Arduemont
James Amril-Kesh wrote:

That actually has nothing to do with what I said.


If your talking about the actual impact the missiles makes on the ship, then damage is not calculated that way. No. The impact of the missile is negligible, because the explosion is doing the damage. (Like most real missiles)

Talking about the explosion (rather than the impact of the physical shell of the missile) in terms of Doppler, would make significantly more sense. Which is why I replied as I did. Especially as that's actually how it works in game.

Edit: Missiles really don't move fast enough for their physical shell's impact to be doing the damage. Kinetic force is speed squared, times weight, divided by surface area. Compared to projectiles, missiles have a very large surface area, and a very very low speed. It's all about the explosion.

"In the age of information, ignorance is a choice." www.stateofwar.co.nf

James Amril-Kesh
Viziam
Amarr Empire
#15 - 2012-10-23 22:08:50 UTC
The damage per volley doesn't change, I'm talking about the damage per second, which changes depending on both the damage per volley and the volleys per second that hit the target. For turrets the velocity is effectively instantaneous, so the impacts per second will be the same as the rate of fire of the weapon, however that's not true for missiles because when you're flying a missile ship towards its target each successive missile doesn't have to fly as far as the previous one and so reach their target more quickly, resulting in missiles hitting the target at a rate higher than the missiles are fired, which results in a higher rate of damage done to the target.

Enjoying the rain today? ;)

War Kitten
Panda McLegion
#16 - 2012-10-23 22:10:32 UTC
Taking into account the start of the engagement delay on your first wave of Damage, and the fact that if you're approaching at 2000 m/s you'll soon be at 0 range, this doppler effect of higher DPS starts out way behind and barely catches up and evens out.

In the end, you still have to have launched X number of volleys to kill your target whether you approached, sat still or moved away. You'll just waste extra volleys if you're not at close range at the end.

I don't judge people by their race, religion, color, size, age, gender, or ethnicity. I judge them by their grammar, spelling, syntax, punctuation, clarity of expression, and logical consistency.

HollyShocker 2inthestink
HOW to PEG SAFETY
#17 - 2012-10-23 22:10:33 UTC
Jack Miton wrote:
Congrats on attending maths classes in highschool.
Realistically the distances traveled between missile volleys is going you be insignificant for this affect but yes, you are correct.


LOL congrats on skipping grammer.
Arduemont
Rotten Legion
#18 - 2012-10-23 22:11:55 UTC  |  Edited by: Arduemont
James Amril-Kesh wrote:
The damage per volley doesn't change, I'm talking about the damage per second, which changes depending on both the damage per volley and the volleys per second that hit the target. For turrets the velocity is effectively instantaneous, so the impacts per second will be the same as the rate of fire of the weapon, however that's not true for missiles because when you're flying a missile ship towards its target each successive missile doesn't have to fly as far as the previous one and so reach their target more quickly, resulting in missiles hitting the target at a rate higher than the missiles are fired, which results in a higher rate of damage done to the target.


Oh, okay. I get you now. Yes, this does happen. Ever hear of cavalry Ravens? They used to MWD nano fit Ravens when torp ranges were massive, so they could start at like 90kms and travel the same speed as the torps towards their target. So when they got to the target all their volleys would hit at once.

They nerfed that for obvious reasons.

"In the age of information, ignorance is a choice." www.stateofwar.co.nf

Istvaan Shogaatsu
Guiding Hand Social Club
#19 - 2012-10-23 22:15:44 UTC
This used to be my strategy with ICC torpedo cruisers in Darkspace.
Jack Miton
School of Applied Knowledge
Caldari State
#20 - 2012-10-24 02:08:53 UTC
HollyShocker 2inthestink wrote:
Jack Miton wrote:
Congrats on attending maths classes in highschool.
Realistically the distances traveled between missile volleys is going you be insignificant for this affect but yes, you are correct.


LOL congrats on skipping grammer.


huh...i fail....

There is no Bob.

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