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By: [ Editor ] Asked from Sweden

How is turning your ship working mathematically?

This is not directly on the topic of orbiting, but on the topic of setting a new course towards a new object.

Turning often seems to involve slowing down. The ship seem to slow down more for a high degree turn. But sometimes the ship makes an almost full speed turn and makes a quite big radius curve before placing itself in the direction I picked.

Main question about turning towards a static object far away

What decides how much the ship will slow down and how big the radius of the turning curve is going to be? How much time would this take?

Bonus question about turning towards a static object that's close

I don't know if the closeness affects anything. But it might spiral you towards the object.

Bonus question about moving objects

And what would happen if the object was moving straight, turning or orbiting another object or you?

Notes

I guess the formula would involve the inertia modifier, the ship's final mass, how many degrees off the new direction is, if the object is close and your current speed.

If you done experiments please provide data.

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4 answers

  • 11

upsideyourhead [ Editor ]

Hello there!

I am the author of EVE Mathematics article linked by Darinas. My article (Chapter 1) has some data specific to the solution of turning and the necessary mathematics is now posted there. I will reprise the method of solution here, and I have posted it along with some relevant graphs in my chapter here. The pursuit curve approach is also relevant, but only to the more complex piloting behavior that happens when using 'Approach' or other built-in motion programs. I have done plenty of math for these circumstances in EVE, however, I have not made time to write them up directly. Perhaps the day will come when there is sufficient interest for a complete treatise on more of the implications of EVE's mechanics...

For now lets talk about the 'double-clicking' problem that Werner Lucifer has outlined for us. To start, lets narrow the situation to motion in a 2-D plane. Indeed, any two-vector command can be represented in a plane chosen to contain both vectors.

What we need is a solution to Equation 1-5 that takes into account an initial ship vector state, and then a change in that state which represents our new motion direction vector and magnitude. Lets say that you are moving at V_{MAX} in the x direction, and you double-click to accelerate in the y direction. For right angle movement like this, it is particularly simple, because the dimensions are completely independent and a method of solution does not require a particular solution for the x direction. Writing the vectors, our initial motion is, V_{init} = [V_{MAX} 0], and the new direction vector would be, V_{comm} = [0 V_{MAX}].

Using Equation 1-5 I simply write the solution in the independent dimensions by inspection. So, in the x direction:

v_x(t) = V_{MAX} * exp(-t/tau)

and in the y direction:

v_y(t) = V_{MAX} * (1 - exp(-t/tau))

Now, you wanted to know what was the total forward velocity of your ship. I can find this by computing the total velocity vector length, or,

v_total(t) = V_{MAX} * sqrt( 2*exp(-t/tau)^2 + 1 - 2*exp(-t/tau))

As an exersize for the reader, see if you can compute a closed form solution for the minimum velocity obtained during motion for piloting changes (Hint: this simplifies nicely for the right-angle case). This has implications for piloting when taking damage from missiles because damage from them depends on total velocity, not angular velocity.

You can compute the velocity profile for an arbitrary angle, theta, by repeating the above process for velocity vectors [V_{MAX} 0] => [V_{MAX}*cos(theta) V_{MAX}*sin(theta)]. Just be careful to compute both homogeneous and particular solutions for the x direction.

Your other questions are, in part, answered in my notes, although I could certainly write more about it.

I thoroughly enjoyed finding this question on the front-page of skilltrainingcompleted. I will be sure to return to this site more often. With any luck we can build a community of people interested in both practical and theoretical understanding of EVE mechanics. And now, back to my tasty lunch of fried chicken...

Good luck, and fly smart.

upsideyourhead

-- EDIT -- I added data to my chapter in Figure I-10. I took data for 45, 90, and 135 degree turns. Enjoy.

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  • 5

darinas [ Moderator ]

I've wondered about this myself. If there is one thing about Eve Online, it is full of geeks! I'm one of them, but my maths skills aren't up to the task of simply explaining the mechanics of turning using the values in the ship info screen. But, one guy has done exactly that: http://knol.google.com/k/upsideyourhead/chapter-i-ship-motion-in-eve-online/2mdavnicxps8v/4#

(Sorry, I can't actually repost the info here in good conscience, in case I get something completely wrong. My maths understanding level only goes to Bachelor of Science (Honours).)

If you need a different take on acceleration in Eve, try the Evlopedia wiki: http://wiki.eveonline.com/en/wiki/Acceleration. Acceleration and circular motion are deeply inter-related.

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werner lucifer
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Great link to that article but I couldn’t find anything specific on the turning bit. Maybe I missed it :/

werner lucifer
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Sorry I found something. I will see if I can find a function for it or if I can work one out myself. “When a command vector is entered into the eve interface, by double-clicking in space, aligning or approaching a stationary object, the ship accelerates in the direction of the command vector.”

werner lucifer
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Thank you so much! The link is Eve heaven! It’s everything I’ve been looking for!

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  • 4

alec grahm [ Editor ]

The direction the ship is pointing is a representation of the motion vector of the ship.

A given ship's acceleration is the ability to change this vector in a given time unit.

Unless the location, is behind you, the path from one vector to another is most likely not coming to a complete halt and then starting on a new vector. So instead, it will constantly be making adjustments to the vector. Slowing down or speeding up is just as 'costly' as turning and if the ship doesn't need to slow down or speed up to get to the proper vector, it won't.

If you where to give the instruction to the ship to fly to something that is immediately behind you, the ship's motion vector will be reduced, then it will do a spectacular flip in space, and then start up again.

If you give the instruction for the ship to fly at something not too far off the bow of the ship (not a planet, but another ship, battery, or something stationary), you will probably get a spiral in to it (depends on distance, and ship performance).

When the object that you are turning 'towards is in motion, you get the pursuit curve. If this is what intrests you, you might consider reading Chases and Escapes: The Mathematics of Pursuit and Evasion

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werner lucifer
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Great links on moving objects and good analysing of the problem at hand! I wonder if it works like the pursuit curves in EVE, it does seem rather likely. I will take a closer look at it.

darinas
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I suppose what we should really be trying to work out is how can you fly a pursuit curve using just double-clicks? ;) I saw a great explanation of flying an interceptor against another interceptor, but I can not find it anymore. Anyone know what I am on about and hwere it lives now?

darinas
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hmmm… > is not a valid link character, but SSC turned my link in my previous comment so that it tries for the > at the end. Click it, manually remove the > and it should work correctly.

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  • 0

joostskywalker

i just know how it works in real, with this knowledge you prob also can change your ship in such a way that you can turn faster then others. basics physics factor is to turn faster is more power or less mass. and how you click your mouse is another story wich is written above.

Fc = M * V ^2/ R Fc= is power ship for example M= mass ship V= speed ship R= radius

so to make it simple M*V*V/R= Fc

so lets explain this: your ship has a certain amount of power Fc and a mass M if you got a certain speed you can calculate the radius.

so if you want a ship to turn around with a certain radius you can determine its speed you need to get to that radius.

This is basic Physics and you can turn in 2D with this, from this you can lead to any more complicated formula. I am guessing, that factors in game based on this too.

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