Sun Flyby Contract

[Ncog Nito]

Hello All.  I have accepted a sun flyby contract and I'm having a small issue.  The game does not allow you to set the sun as a target, therefore, I am not sure how to aim for it.  This is my first attempt at leaving Kerbin space before accepting the explore Duna contract.  Any tips?

[Dman979]

I've got good news and bad news for you, @Ncog Nito.

 

The good news is that you don't have to aim for the sun. The bad news is that you might need a very big ship.

 

In Kerbal Space Program, there is no way to escape the Sun's influence, short of being in a different SOI. As such, to get into a lower solar orbit from Kerbin, you just need to burn prograde on the early-morning side of the planet (the side facing forward with respect to Kerbin's orbit) until you reach escape velocity and leave Kerbin.

 

The bad news is that depending on the altitude the contract wants you to fly at, you'll need a lot of Delta-V. It costs about 1k Delta-V to escape from LKO, but that just gets you a little lower than Kerbin. In order to get even lower, you'll need to pack more DV, and more stages, into the ship.

[Capt. Hunt]

The Sun's SOI is everything that isn't part of the other planets' or moons' SOIs, so all you have to do is burn until your trajectory is a Kerbin escape.  Strictly speaking, a Kerbolar flyby is probably easier then the interplanetary transfer orbit you'll need for your Duna mission, since it doesn't require a transfer window, and it's down the well instead of up it.  Depending on the terms of the contract, you may even be able to kill two birds with one stone, since an interplanetary transfer orbit is by definition a flyby of the sun.  Are there any altitude/perihelion requirements for the flyby?

Edited April 21, 2017 by Capt. Hunt

[MacLuky]

Yes you can even pick up tourists and use a mun and minmus gravity assist to get thrown out of the system. If you pack 1500 dv you should be okay.

[FancyMouse]

20 minutes ago, Dman979 said:

In order to get even lower

You don't need to. From exploration contract point of view, Sun fly by is the same as orbiting Sun. As others just pointed out, you could complete the contract by just momentaily escape Kerbin. And I've tried a few versions back that if I first escape Kerbin with a Sun escape velocity, "orbiting Sun" is still tracked completed. So no need to aim for Sun escape velocity - just Kerbin escape is sufficient.

[Ncog Nito]

Thanks guys, big help, and good to know.  One other question, if its convenient in this thread, what does SOI stand for? 

[Urses]

SOI = Sphere of Influnce.

Urses 

[Capt. Hunt]

Just a quick forum hint, if you hover your mouse over any word or acronym underlined with two sets of dotted lines, a tool tip will pop up with a definition.

 

In this case, because KSP does not use n-body physics, every large celestial object's gravity is applied only to objects within a sphere of influence around it.

[Ncog Nito]

Excellent.  Thanks for the tips.

[juanml82]

I'll add that the peeking out of Kerbin's SOI and returning to Kerbin is a good way to train kerbals:

Go to Minmus, land there. Maybe refuel, if you unlocked the tech and have a mining rig there.

Leave Minmus and, in doing so, make a burn long enough to also leave Kerbin's SOI

The moment you leave Kerbin's SOI, mark Kerbin as your target and burn towards the target (ie, Kerbin). Your burn will take you back into Kerbin's SOI.

Get into Kerbin's SOI. Instead of circularizing at Pe for capture, perform a Hoffman transfer to the Mun.

Capture at the Mun so you orbit the Mun

Return to Kerbin's surface

 

Any kerbal you had in your ship will end up with three stars

[Loren Pechtel]

22 hours ago, juanml82 said:

I'll add that the peeking out of Kerbin's SOI and returning to Kerbin is a good way to train kerbals:

Go to Minmus, land there. Maybe refuel, if you unlocked the tech and have a mining rig there.

Leave Minmus and, in doing so, make a burn long enough to also leave Kerbin's SOI

The moment you leave Kerbin's SOI, mark Kerbin as your target and burn towards the target (ie, Kerbin). Your burn will take you back into Kerbin's SOI.

Get into Kerbin's SOI. Instead of circularizing at Pe for capture, perform a Hoffman transfer to the Mun.

Capture at the Mun so you orbit the Mun

Return to Kerbin's surface

 

Any kerbal you had in your ship will end up with three stars

I thought you needed flags on the two moons + leaving the SOI to get 3 stars.

[juanml82]

31 minutes ago, Loren Pechtel said:

I thought you needed flags on the two moons + leaving the SOI to get 3 stars.

Nope, they reduced the requirements in one of the last updates. Land in one of the two moons, orbit the other and leave SOI is enough now. Since Minmus requires less dV to land and take off and the Mun is easier to aim for while returning to Kerbin, I'd rather go Minmus surface -> out of soi -> Mun orbit -> recover at Kerbin

[blakemw]

On 4/21/2017 at 8:56 AM, FancyMouse said:

And I've tried a few versions back that if I first escape Kerbin with a Sun escape velocity, "orbiting Sun" is still tracked completed.

Fun fact though, is that if you merely "flyby" the sun (that is, leave Kerbin's SOI on a trajectory which enters another SOI, either back to Kerbin after ~1 year or another planet) you get awarded the flyby but not the orbit. I used to believe that any escape from Kerbin's SOI would award the Sun Orbit, but nope, it has to display a proper, non-broken orbit.

[Kryxal]

For 3 stars, it looks like the "easiest" way is probably Mun flyby, Minmus landing and flag, pop out of Kerbin SoI and return.  If you don't feel like placing a flag on Minmus, you'll need a Mun orbit.