What is the highest possible orbital period in game?

[Pawelk198604]

I wonder does is possible to send kerbal for orbit return to Kerbin in 500 years   

https://www.youtube.com/watch?v=BINijYepahA

[Snark]

Absolutely possible to get well over 500 years.  Orbital period goes up with the 1.5 power of the semimajor axis, so it blows up in a hurry as you start getting far from Kerbin.  For example, a circular orbit of period 500 Kerbin years would have about 63 times the orbital radius of Kerbin, i.e. about 850G meters.  That's not all that much; heck, there are mods with solar systems that have planets farther out than that.  For example, IIRC, I believe Galileo's Planet Pack has a dwarf start that orbits the sun out at a distance of 1200G meters or so.

So yeah, it's possible to have periods much, much longer than that.

As for "what's the actual limit":  that's a tricky one.  There's no actual "edge" to the kerbal universe-- the sun's gravity (and SoI) go on forever.  There's no hard boundary.  However, if you add enough zeroes onto the distance from the sun, eventually the program starts getting flaky / buggy because of floating-point errors.

[Pawelk198604]

17 minutes ago, Snark said:

floating-point errors.

floating-point errors.? I heard that name somewhere   

Edited September 15, 2017 by Pawelk198604

[Snark]

12 minutes ago, Pawelk198604 said:

floating-point errors.? I heard that name somewhere   

Avoiding the technobabble, what it boils down to is that when the numbers get big enough, the software basically runs out of decimal places to stay sufficiently precise, and then Weird Stuff happens.

But that's only when the numbers get *really* big. I haven't tried it myself, but I bet you could have a KSP orbit that's many, many thousands of years.

[Geschosskopf]

Well, it depends on how you define "orbital period"......

I've seen many trans-Eelooian KBOs with periods greater than 2000 years.  This is rather commonplace if you use Custom Asteroids and take the time to set up realistic bodies to track (or use my own or one of the many other OPM-friendly config files to do this for you).

I've used warp drives to get into interstellar space and paused to look around, at which point I was orbiting the center of the galaxy at periods measured in hundreds of thousands of years.

And the Kraken has taken many of my ships into intergalactic space, tens of thousands of parsecs from Kerbin, where they perhaps orbit the Great Attractor for all I know.  Anyhow, when any instrument has been able to make any sense out of such an out-of-range condition, my orbital period has been 6,666,6666 GIGAyeas, which is longer than the real universe has existed to date, so I assume I'm way out there surfing the wave of the Big Bang  

Edited September 16, 2017 by Geschosskopf

[invision]

[The Aziz]

14 hours ago, invision said:

<pic>

What'd you say..

Yes, Kraken'd.
But I wonder, since Kerbol SOI is infinite, how long it would take to lose THAT velocity and fall back.

[FungusForge]

According to google that's 44,369,444 times the speed of light. That's moving more than a lightyear every second.

7 hours ago, The Aziz said:

how long it would take to lose THAT velocity and fall back.

The heat death of the universe might come first.

[KerikBalm]

13 hours ago, The Aziz said:

But I wonder, since Kerbol SOI is infinite, how long it would take to lose THAT velocity and fall back.

You're making a logic error here. Escape velocity is still escape velocty. It won't lose that velocity and fall back.

Hyperbolic trajectories are... well.... hyperbolic trajectories... The real universe doesn't have gravity just stop affecting things at a certain distance. SOIs are a human construct to simplify calculations. The voyager probes will never not be affected by the sun's gravity, but they will never lose their velocity and fall back.

[Chakat Firepaw]

On 2017-09-16 at 2:57 PM, The Aziz said:

Yes, Kraken'd.

But I wonder, since Kerbol SOI is infinite, how long it would take to lose THAT velocity and fall back.

It will leave the SOI before it starts falling back.  Remember that the gravitational potential energy at infinity is still finite, if you are going up with more kinetic energy than that you will never stop unless you interact with a third body.

[magnemoe]

11 hours ago, Chakat Firepaw said:

It will leave the SOI before it starts falling back.  Remember that the gravitational potential energy at infinity is still finite, if you are going up with more kinetic energy than that you will never stop unless you interact with a third body.

Its two effects here, first the gravity slows the probe down on the other hand the gravity get weaker as farther you get from the sun. 
The braking depend on gravity, at escape velocity you end up with an rest speed its math for it but i don't remember it. 

SOI in KSP let you escape an body with a bit below real escape velocity 

[kerbiloid]

A test with MechJeb and Alt-F12 magic shows:

Probe: simple hex + rtg + MechJeb AR202.

There is a critical distance where MechJeb suddenly starts displaying negative values of date parts, and the skybox suddenly gets bright.
(They do this at once, so I guess not just MechJeb calculations get wrong, but general numerical problems appear).

Orbit semiaxis = 1.2864 Em = 1.2864 * 10¹⁸ m = 136 l.y.
Orbital period = 920 bln y.
Orbital speed = 0.95 m/s

Of course, it's impossible to see this orbit in a map or a tracking station modes.

Returning to KSC from below this distance makes KSC to appear in the ocean (the ground reappears in several seconds).
Returning to KSC from above this distance makes the new probe appear in space instead of Kerbin.

(By unknown reason, the picture doesn't get embedded here)
https://imgur.com/6KCHPyk

Upd.
Just checked. Reaching distances ~10³⁶ m cause NaNs and game crash.

Edited September 19, 2017 by kerbiloid

[Chakat Firepaw]

On 2017-09-18 at 7:52 AM, magnemoe said:

Its two effects here, first the gravity slows the probe down on the other hand the gravity get weaker as farther you get from the sun. 
The braking depend on gravity, at escape velocity you end up with an rest speed its math for it but i don't remember it. 

SOI in KSP let you escape an body with a bit below real escape velocity 

You missed the point I was making:  The craft would leave the SOI first, even though the SOI in question extends to infinity.

[VincentThacker]

With HyperEdit, you can put your craft into an insane circular Kerbol orbit that is several million exameters with an orbital velocity of 0.1 m/s. Pretty sure that would take quadrillions of years to complete. Of course, in real life, this is not very possible as the SoI of Kerbol is infinite in KSP. Thus, technically, you can be at infinite distance with an infinite orbital period

Edited September 23, 2017 by 100055

[Darael]

7 hours ago, 100055 said:

With HyperEdit, you can put your craft into an insane circular Kerbol orbit that is several million exameters with an orbital velocity of 0.1 m/s. Pretty sure that would take quadrillions of years to complete. Of course, in real life, this is not very possible as the SoI of Kerbol is infinite in KSP. Thus, technically, you can be at infinite distance with an infinite orbital period

No, you can't, because there exist maximum values dictated by the nature of the game engine.  The SoI is infinite but the maximum distance at which a craft can be located is not.

[VincentThacker]

7 hours ago, Darael said:

No, you can't, because there exist maximum values dictated by the nature of the game engine.  The SoI is infinite but the maximum distance at which a craft can be located is not.

It is possible with HyperEdit. You can place a craft so far from the Sun that its orbital period is effectively infinite.

[FungusForge]

27 minutes ago, 100055 said:

It is possible with HyperEdit. You can place a craft so far from the Sun that its orbital period is effectively infinite.

You seem to be misunderstanding. Yes, Hyperedit (and the Alt+F12 Set Orbit tool for that matter) have no hard limit for how far a craft can be placed, but the game itself does. As Snark said:

On 9/15/2017 at 4:46 PM, Snark said:

As for "what's the actual limit":  that's a tricky one.  There's no actual "edge" to the kerbal universe-- the sun's gravity (and SoI) go on forever.  There's no hard boundary.  However, if you add enough zeroes onto the distance from the sun, eventually the program starts getting flaky / buggy because of floating-point errors.

Since there is a finite limit to what the game can handle, there is a finite limit to what the orbital period can be. Unless Hyperedit entirely prevents such errors, then it too has a limit. A limit of what the game can handle.

[Darael]

11 hours ago, 100055 said:

It is possible with HyperEdit. You can place a craft so far from the Sun that its orbital period is effectively infinite.

This isn't about a limit on what you can practically reach (which HyperEdit would bypass), it's about the fact that there is an edge to the Kerbal universe, somewhere around a number of distance-units from the centre equal to the maximum number representable with an IEEE float.  That's before we even start considering the case where the orbital radius is large enough that the limits of floating-point precision make the physics break down, as @FungusForge notes - krakensbane helps to reduce those effects (by putting the craft at or near the centre of the universe), but they still kick in long before you reach the actual edge (because everything else is then way out towards the "new" edge, so even though those things are on rails, your acceleration due to gravity gets all messed up).

 

Just to clarify, my original "no, you can't" wasn't in response to "With HyperEdit, you can put your craft into an insane circular Kerbol orbit that is several million exameters with an orbital velocity of 0.1 m/s", because that part is true.  No, it was a response to the last sentence: "[...]technically, you can be at infinite distance with an infinite orbital period"

Edited September 24, 2017 by Darael

[septemberWaves]

On 9/15/2017 at 10:03 PM, Pawelk198604 said:

floating-point errors.? I heard that name somewhere   

Basically, there's a power of 2 (I can't remember which power of 2 but I think it might be 2⁶³) which is around 9 quintillion, and a computer cannot count beyond it while maintaining precision to the nearest integer due to the way numbers are stored and manipulated in a computer. You start getting gaps of 2, and then gaps of 4, and then gaps of 8, and so on until the computer can't even calculate precision to the nearest billion integers (and beyond that too). The gaps beyond the maximum integer lead to calculation errors which come from inability to be precise, termed "floating point errors".

If you want precision to more decimal places than the nearest integer, the cutoff point is reduced. Precision to the nearest half-integer only goes up to 2^62, precision to the nearest quarter-integer only goes up to 2^61, and so on. Essentially, the closer the number is to zero, the more precision you can get. This means that for larger numbers the computer loses accuracy, and if it's trying to calculate huge orbital periods it won't be able to calculate them to nearly as many decimal places as it would for an orbit that's, for example, 1/1024 times as far from the Sun.

[cubinator]

For an explanation of floats (not in KSP but it's the same principle):

https://www.youtube.com/watch?v=9hdFG2GcNuA

 

[Dunbaratu]

What is the definition of an "orbital period" for a hyperbolic trajectory?  Is it "imaginary number" or is it "infinity"?  If it's "infinity", then that's your answer.  The highest possible orbital period is infinity.

And speaking of floating-point problems. The IEEE standard for floats and doubles does in fact have a definition of how to store a value of "infinity", so it's possible to *actually* have that value in the game, depending on how they implemented it.

 

Edited September 25, 2017 by Steven Mading

[Darael]

7 hours ago, Steven Mading said:

What is the definition of an "orbital period" for a hyperbolic trajectory?  Is it "imaginary number" or is it "infinity"?  If it's "infinity", then that's your answer.  The highest possible orbital period is infinity.

And speaking of floating-point problems. The IEEE standard for floats and doubles does in fact have a definition of how to store a value of "infinity", so it's possible to *actually* have that value in the game, depending on how they implemented it.

 

While you're right in principle, the game stores orbits by way of their semimajor axis; orbital period is a calculated value.  To the best of my knowledge, no calculation that doesn't start containing an infinity and doesn't involve dividing by zero is going to produce one, at least in the sorts of languages involved.  I don't think calculations that result in values greater than the maximum return +Infty, though I confess I haven't checked.

You should be able to set an infinite orbital radius, though, assuming the save-file reader can cope with it.

On the hyperbolic question: yes, it's infinite, nominally, but KSP uses some means to ascribe a nominal orbital period for use with the MNA value stored in the save file - although I have no idea what that is.