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How do agility, turn radius and speed work together?

Asked by [ Editor ]

How do I figure out what my maximum speed is orbiting an object at a given distance with a given agility?

Example: is it reasonable to assume that an interceptor can orbit a ship at 1500M doing 1700 m/s?

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5 answers

7

alec grahm [ Editor ]

From what research I've read in this thread, it appears that the formula for an orbit is:

r = A * m * v^2 / (sqrt (Vmax^2 - v^2) * 10^6)
  • r = Orbital Radius
  • A = Agility
  • m = ship mass (in kg)
  • VMax = maximum velocity for the ship
  • v = orbit velocity for the ship

Realize that you're solving for radius here rather than velocity. Note that you will not be traveling at maximum velocity around the object (that would divide by zero and cause the universe to explode).

The orbit velocity for the ship has some trig that I'm not entirely comfortable with.

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1

upsideyourhead [ Editor ]

Closed form solutions to your question can be computed from these notes on the mathematics of ship motion in EVE-Online Chapter 1. I was unaware of the thread on EVE-O forums that discusses similar results, motion thread, until today. Fortunately, my link describes how you can also solve for the radius of the orbit as well as the velocity. Perhaps more can be written about this in the future when I get time...

upsideyourhead

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0

jmblanckenberg [ Editor ]

To get the speed u can fly at a radius x the formula is

( Vm^2 – v^2 ) / v^4 = A^2 * m^2 / ( ( 10^12 ) * r^2 )

where the coefficients are the same as above

then u’ll get ( Vm^2 – v^2 ) / v^4 = num which u simply turn into a quadratic equation

num * v^4 + v^2 – Vm^2 = 0

let a = num, b = 1, c = -Vm^2

Use quadratic equation to get

Sqrt( (-b + or – Sqrt( b^2 – 4ac ) ) / 2a)

I think its always gonna be the + not the – but try both if one doesn’t work :) bit of a long way to get it, but put it into a excel spread sheet and u can find the speed at a radius x quite easily

Kondelis :)

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0

greatgold

Just to take this out of the theoretical and give you an in-game example: if you have a Crow with a max speed (in a straight line) of ~4800m/s, and set the crow to orbit at max speed at 17km, you will generally end up in an orbit just on the outer edge of 20km at an actual speed of roughly ~4200m/s. If you set the Crow to orbit at 500m at full speed, you will end up in an orbit of around 5000m at around 1000m/s (but my memory is hazy on this one, so please correct me if wrong). Again, this is very generalized, but should give you and idea of some parameters to start experimenting with. Now it can chance quite a bit based on fitting (nanofibers, inertials, rigs) and navigation skills.

Conversely, in a Taranis set to orbit at 500m using an AB with a max speed of 1400m/s, the orbit will end up at ~3500m at around 800m/s.

NN comments
darinas
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So how are those values calculated, do you think? If I set a radius and a speed, the ship will never match those values unless I pick a large orbit and/or small speed. Better still, how would I calculate that the orbit will be elliptical instead of circular?

gah'matar
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Orbit will settle to circular around unmoving object. If you set the speed (manually) for your ship to ~1 m/s, your orbit should be spot on… Or if you 0 the mass (fly a pod for the closest approximation).

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0

canhasgank [ Moderator ]

The sort answer is undock and test it out. Fit out your ship and orbit an object.

There's no easy way to calculate this.

NN comments
yuripup
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I am sure there is well heeled formula that EVE is using to generate this. It might be hiding, but I am sure its out there.

alec grahm
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@YuriPup – there is. However, solving 3d vector problems and differentials isn’t trivial for undergrad level college math. It is further complicated by the question of “is the subject at rest or in motion?” One will get different answers for the tightest orbit (when orbiting a ship in motion you sometimes have to play ‘catch up’ to it). Two threads on orbit math I’ve found – http://tinyurl.com/27yskmx and http://tinyurl.com/2cxejdk — Still trying to get my head around some of them.

yuripup
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I am happy to see the simplifications for a static target in 2 dimensions. Its probably close enough, most of the time.

canhasgank
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I said there’s no EASY way to figure this out. Of course there’s a formula for it. There is one for everything in EVE :)

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