Escaping the Sun

[capi3101]

Alright...I hate to admit this, but I've started a challenge whose goal is to send a craft on a Kerbolar escape trajectory, and I have no earthly idea how to do this my own self.

Here's my sitrep at this point - I have a craft in a 125k Kerbin orbit (I overshot a bit), KER says I have 4,917 m/s of delta-V available and my current TWR is .453. It is Year 1, Day 5, 04:12:17 in my save game. I can go at any time.

So how does one achieve a Kerbol escape trajectory? (For clarification: I'm talking about escaping from "The Sun").

Edited March 3, 2014 by capi3101

[RocketPilot573]

Well, you can achieve "escape velocity," It wont take much once you get past Jool. However, the Sun's SOI is infinite due to the lack of an SOI to change to (there's nothing beyond the Sun). So you can never escape, regardless of how far you timewarp.

[Kasuha]

Here is one option. But it can be done directly form Kerbin orbit, too.

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[InterCity]

As far as i know, the broken K-Drive is a best way to reach escape velocity.

As mentioned before, there is nothing like kerbol escape. If you don't prod the kraken of course.

[Kasuha]

there is nothing like kerbol escape

There's nothing like Kerbol in the first place, the thing in the middle is called Sun.

And the fact that its SOI is infinite does not mean you cannot reach escape velocity. Because escape velocity means there is no apoapsis and the ship will keep flying away however long you wait.

[sal_vager]

Actually, the devs also sometimes call it that, the names stuck.

[Francesco]

I don't get this, on that thread you yourself posted a screenshot of a ship on escape trajectory... wut?

How can you not know what you already did?

[InterCity]

There's nothing like Kerbol in the first place, the thing in the middle is called Sun.

And the fact that its SOI is infinite does not mean you cannot reach escape velocity. Because escape velocity means there is no apoapsis and the ship will keep flying away however long you wait.

It seems you misunderstood me. Yeah, i know that the thing in the middle is called sun, although it's referred to as "Kerbol" often, and i see this as the most common way to call sun.

By "escape" i meant "leaving sun SOI". I think that it's clear, since i already mentioned that the K-Drive is probably the best way to achieve sun escape velocity. You just won't leave the SOI.

[maltesh]

Alright...I hate to admit this, but I've started a challenge whose goal is to send a craft on a Kerbolar escape trajectory, and I have no earthly idea how to do this my own self.

Here's my sitrep at this point - I have a craft in a 125k Kerbin orbit (I overshot a bit), KER says I have 4,917 m/s of delta-V available and my current TWR is .453. It is Year 1, Day 5, 04:12:17 in my save game. I can go at any time.

So how does one achieve a Kerbol escape trajectory? (For clarification: I'm talking about escaping from "The Sun").

Easiest way? Throw down a maneuver node on or a little bit before the point where your orbit crosses the midnight line, and pull it for awhile. Adjust it and slide it backwards to keep your direction of departure along Kerbin's direction of travel. As I recall, the delta-V required to put yourself on a trajectory that escapes the sun from LKO is somewhere between 2500 and 3000 m/s. I /want/ to say it's about 2800.

[Rhomphaia]

Trying to get to Moho usually does the trick for me:huh:

[Kasuha]

By "escape" i meant "leaving sun SOI". I think that it's clear

Okay, but I think the main reason I did not understand it the way you meant it is because "Probe A is on XXX escape" usually means it has acquired escape velocity for XXX and is on escape trajectory from XXX. These terms are not limited to KSP.

[capi3101]

Well, you can achieve "escape velocity," It wont take much once you get past Jool. However, the Sun's SOI is infinite due to the lack of an SOI to change to (there's nothing beyond the Sun). So you can never escape, regardless of how far you timewarp.

I was aware that you can't actually escape. But there does come a point where the game hits the numerical limits of the programming language, your SOI says SUN and your situation becomes ESCAPING. That's what I'm hoping to acheive here.

Here is one option. But it can be done directly form Kerbin orbit, too.

About where did you put your Kerbolar periapsis in that screenie, Kasuha?

I don't get this, on that thread you yourself posted a screenshot of a ship on escape trajectory... wut?

How can you not know what you already did?

Wasn't my screenie...

Easiest way? Throw down a maneuver node on or a little bit before the point where your orbit crosses the midnight line, and pull it for awhile. Adjust it and slide it backwards to keep your direction of departure along Kerbin's direction of travel. As I recall, the delta-V required to put yourself on a trajectory that escapes the sun from LKO is somewhere between 2500 and 3000 m/s. I /want/ to say it's about 2800.

Alright, I may give this a shot. I'd been doing my burn at sunrise; probably why I was having problems with it.

[Kasuha]

About where did you put your Kerbolar periapsis in that screenie, Kasuha?

I have no idea, I just put it where I thought it's low enough. It was inefficient maneuver anyway, I just found I can escape the system with over 100 fuel units left with the same rocket if I burn for escape straight from Kerbin orbit.

[Pds314]

Just wait until you are about 120 degrees from Kerbin's prograde and then burn aggressively toward your prograde. Shouldn't need very much Delta-V if you have a powerful engine thanks to the Oberth effect. (doable in 2800 m/s or less.)

[Pds314]

It would be interesting to live in a universe with no such thing as an escape velocity due to F=m1*m2*G/r instead of over r^2. I guess that technically means everything is a black hole, doesn't it.

In other words. 2D is wierd.

[capi3101]

Just wait until you are about 120 degrees from Kerbin's prograde and then burn aggressively toward your prograde. Shouldn't need very much Delta-V if you have a powerful engine thanks to the Oberth effect. (doable in 2800 m/s or less.)

Well....I've got one nuke and I'm pretty sure I'm too high to exploit Oberth effect to the maximum capability. I'm hesitant to lower my orbit at this point, though I might if I can do it cheaply.

[Claw]

I'm not certain what you're asking for Capi. If it's just placement of the node to escape Kerbin (for Solar "escape"), then it's just short of the Kerbin midnight point (not the midnight terminator). So almost the straight opposite side than the sun, but slightly "back" toward the midnight terminator. Basically you're pulling the prograde marker tangent to Kerbin's orbit.

Yeah, from a 75km circular orbit, it takes about 2800 m/s.

[capi3101]

I was simply asking for instructions on how you should go about making the burn, and y'all have answered that question succinctly. I can happily report success this evening:

I did go ahead and do one periapsis kick first; it was one of those deals where I'd have been burning straight down into Kerbin if I had tried to do it all in one thwack. Basically just set up the maneuver node at 120 degrees ejection angle like y'all told me to do; PreciseNode helped with that.

Thanks for y'all's help.