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Has anyone seen Orbiting the Sun contract?


FancyMouse

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I guess it can't appear without the first time leaving the Kerbin SoI being a Sun-escaping trajectory? From my understanding, it looks like "orbiting" is given after "fly-by", and if you fly-by Sun, most likely you'll be orbiting it, and leaving a progress mark for orbiting as well and then "orbiting" will not be offered any more.

If what I guess here is true, then I might consider doing it in my current career save. But first I probably want to hear from you folks and see whether my hypothesis is already busted by some counterexamples that I'm not aware of.

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That's what I'm curious about - is it really that "fly-by" is the only contract, or it's actually the case that, there is indeed an "Orbiting" contract, it's just that the way most people do it (as what you said) is automatically achieving an orbit and thus preventing the contract from appearing?

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Oh, now I see what you mean. Well in that case, I dont know really... might be worth a shot out of the solar system. :cool:

Is that even possible?

If, as suggested by the OP, you want to never, ever have been orbiting the sun, you would need to be leaving kerbin SOI with enough speed already to be right away on a Solar escape trajectory.

I'm not really aware of the required speed for an escape trajectory from as low as Kerbin in the Sun gravity well, so this might be a stupid question...

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I'm not really aware of the required speed for an escape trajectory from as low as Kerbin in the Sun gravity well, so this might be a stupid question...

Well, by the wiki Kerbin has no eccentricity and a 9284.5 m/s orbital velocity, so if you wanted to "escape" the sun, which I guess means having at least a parabolic or probably hyperbolic trajectory, so we can say you would need to escape Kerbin itself along prograde at (sqrt(2)-1)*9284.5 m/s ~= 3845.8 m/s.

And if you want to escape Kerbin's SOI with that velocity, since its SOI distance of 84,159,286 m, at the time you're at distance 700km for example (so 100km above Kerbin's surface) you'd need to be traveling at around 4979.6 m/s.

Given that it's a lot easier to do these fine "aims" from orbit where you have the luxury of setting up manuever nodes just right, rather than a straight shot from the surface (at least, easier for me), and at an LKO 100km circular orbit (with a 2246 m/s velocity), maybe budget for having another 3000 m/s DV from LKO, ideally more, to account for the fact that you'd doing this from orbit and so won't have an exactly straight shot on Kerbin prograde? (I would hope the loss of efficiency wouldn't be more than 10%. I'm not quite sure how to adjust the simple calculations to account for when you leave from orbit instead of from straight shot, you won't escape exactly prograde. Maybe someone smarter knows.)

Anyway that all seems doable. Though admittedly that's a cheap thing for me to say since I've not tried to do it. :)

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I thought you couldn't escape the Kerbol SOI as it has no bounds. There is a second option of escaping Kerbin on a sub-orbital Kerbol trajectory.

Missions to put an object on a Kerbol escape trajectory are satisfied by putting the required object into a parabolic or hyperbolic trajectory (as opposed to a nice periodic elliptical or circular orbit). I'm thinking especially of those crazy missions to eject a class E asteroid from Kerbol. :P They do not depend on a finite SOI. You do not escape the SOI of course, but that is not the definition of escape KSP uses.

Doing a suborbital is an interesting strategy. That would require that at the point you leave Kerbin you have an orbital velocity of 1803 m/s around Kerbol (so your eliptical orbit is below Kerbol's surface). This means I guess escaping at about 7481 m/s retrograde. Using the same strategy as I outlined above that means 8122 m/s at 100km, so if done from orbit it would require ~6000 m/s delta v?

Still doable, but harder?

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I wonder how much of that 5000 escape d/v or 6000 deoribt d/v you could save if you start in a low-Minmus orbit when Minmus is in the correct orbital position...

(I like launching my interplanetary missions from Minmus because that makes it easy to have practically full fuel+ore tanks without adding additional stages. Not sure if it actually helps me at all though... especially when Minmus is in the wrong orbital location relative to Kerbin)

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I wonder how much of that 5000 escape d/v or 6000 deoribt d/v you could save if you start in a low-Minmus orbit when Minmus is in the correct orbital position...

So how efficiently can you do a Minmus-escape-Kerbin-return burn, from Minmus orbit? (I forget myself. Is it 200 m/s? 300 m/s?) Anyway, you'd get for "free" back the usual 930 m/s, minus whatever that is. Maybe 600 m/s, 700 m/s?

And then you're really, really lucky and good, the Mun lines up just right so you can use its 542.5 m/s orbital velocity to extract another ~1100 m/s, for a total gain of ~1700 m/s. :D

Right. But of course there's the more appealing answer: moar boosters. ;)

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