SSTN - single stage To Neptune

[SunJumper]

Your goal is to go from Kerbin orbit, to 410 million km (in the Sun's SOI), circularise, then at some point return to Kerbin. From leaving Kerbin's SOI to return, this must be one stage.

Tip: You don't need much fuel after your final intercept, just get your final periapsis at about 30km, and the atmosphere will do the rest. Your launch stage can be as big as you want, and you can get your solar apoapsis at the required height whilst in your launch stage...

[Maxed-Rockets]

Your goal is to go from Kerbin orbit, to 410 million km (in the Sun's SOI), circularise, then at some point return to Kerbin. From leaving Kerbin's SOI to return, this must be one stage.

Tip: You don't need much fuel after your final intercept, just get your final periapsis at about 30km, and the atmosphere will do the rest. Your launch stage can be as big as you want, and you can get your solar apoapsis at the required height whilst in your launch stage...

Do you mean mean 410 billion meters? 410 million is really low, and Neptune is really high.

[TheDarkStar]

Do you mean mean 410 billion meters? 410 million is really low, and Neptune is really high.

He might mean 41 billion meters, since things in KSP have about 1/10 the size.

[Maxed-Rockets]

Whatever he meant I think this can get there:

http://imgur.com/a/8s5le#0

Adding a little bit of fuel I got to Laythe with 100l of fuel in the nuke engines.

[SunJumper]

I did mean 410 billion metres, as I said 410 million kilometres. And I took the smaller size into account with this...

[Rifleman192]

The scale is actually closer to 7/10 Sol/Kerbal ratio.

[Rifleman192]

My bad, I did the math and found that its a 8.8/100 equivalent Kerbol/Sol. The densities in KSP are a little bit higher with the same gravity as it's real-life counterpart. That would explain how the Kerbals evolved so short and stubby. lol Kerbol itself, being a "red dwarf" of sorts is significantly smaller than what it should be compared to Sol. That means the Neptune equivalent in KSP would orbit at around 395 ot 400 billion meters accounting for eccentricity.