How about Moho to Eeloo?

[More Boosters]

It just occurred to me to check inclination for Eeloo and Moho, and they are 6.15/7 degrees respectively. Those two values are very close to each other so unless they are on opposite directions, it seems like a Moho vehicle that fills up nicely with ISRU can do a more efficient transfer to Eeloo than it would from Kerbin. I didn't actually get any numbers for this and I don't know if being that close to the sun would make the Oberth effect you get not worth it (as from Kerbin you start with Kerbin's higher energy orbit), so can someone tell me if a Kerbin -> Moho -> Eeloo round trip may actually make sense? Or is a straight transfer to Eeloo more efficient? Keep in mind that I know Moho is hell to get to and there's no way Moho to anything will save Delta-V much less when landing is involved, but consider ISRU and just a fully fueled spacecraft at Moho surface. Edited November 20, 2015 by More Boosters

[A_name]

The way I understand Oberth Effect is that you can get more energy out of the same burn the more kinetic energy you’re already carrying, i.e. the faster you’re going. So from that perspective, a craft landed on Moho has more kinetic energy than one landed on Kerbin because of Moho’s higher orbital velocity, so the transfer to Eeloo should be more efficient, but not necessarily cheaper because you have to raise your orbit higher than you would if departing from Kerbin. Without any solid basis to say this, it seems to me the transfer burn would end up being more expensive overall.

In my experience, the best way to get to Eeloo is with a Jool gravity assist. When I say “best way” I’m considering a balance between efficiency and simplicity. But you can be even more efficient, for example, by using a combination of gravity assists from Eve, Kerbin and Jool.

[Streetwind]

Well, what do you want to achieve with a Kerbin -> Moho -> Eeloo trip? Lower dV from Kerbin?

Then I have the duty to inform you that a Kerbin -> Moho trip takes more dV than a Kerbin -> Eeloo trip in the first place, even without a Jool gravity assist. Moho is the highest dV destination in the stock game. ;)

[Snark]

You have to bear in mind that "efficiency" becomes a bit more abstract when ISRU is involved.

For example, at one point I had a large ship at Moho that I wanted to send back to Kerbin. Instead of going straight back from Moho to Kerbin, I went to Eve first and then from Eve to Kerbin.

That wasn't the most "efficient" way-- it's definitely cheaper in terms of total dV to go straight from Moho to Kerbin than from Moho to Eve to Kerbin.

However, a direct Moho-to-Kerbin trip takes a [I][U]lot[/U][/I] of dV, and my ship was marginal in that regard. And also, a direct Moho-to-Kerbin transfer will cause an arrival at Kerbin with very high velocity, and there was some concern about whether my ship could handle aerobraking at that speed; arriving at Kerbin from Eve results in a considerably lower velocity upon Kerbin arrival.

Therefore, I sent my ship from Moho to Eve (requiring much less dV than sending it to Kerbin); stopped at Gilly to mine fuel and fill up my tanks; then went home to Kerbin. Very poor "efficiency" in terms of total dV used, and crappy use of Oberth effect, but the fact that I could stop in the middle to fill up my tanks more than made up the difference.

Be aware that Moho is very deep in the Sun's gravity well. It will take considerably more dV to go from Moho to Eeloo than from Kerbin to Eeloo. ([URL]http://ksp.olex.biz[/URL] is a handy tool for this). So the question is whether you have the dV budget for it.

An easier solution, from an engineering standpoint, would be to go home to Kerbin first, fuel up from a mining operation on Mun or Minmus, then go from there. I like Minmus as a refueling stop, because not only is it very cheap to land and take off from (really helps with mining economics), but also, if you're leaving Minmus to go to another planet in the Kerbol system, you can get a pretty good slingshot past Kerbin for some Oberth love. Just takes a little finesse to deal with the orbital inclination.

[More Boosters]

[quote name='Streetwind']Well, what do you want to achieve with a Kerbin -> Moho -> Eeloo trip? Lower dV from Kerbin?

Then I have the duty to inform you that a Kerbin -> Moho trip takes more dV than a Kerbin -> Eeloo trip in the first place, even without a Jool gravity assist. Moho is the highest dV destination in the stock game. ;)[/QUOTE]

No I thought I had clarified that in the OP but apparently it didn't work out. Yeah, I know Moho is the most expensive place to be.

Ignore the first Kerbin -> Moho bit. ISRU helps us pretend we're launching from Moho; sure there is no giant launch stack but we don't need one to begin with.

What's cheaper in terms of Delta V, your typical Kerbin -> Eeloo or Moho -> Eeloo?

Edit: And as Snark answered, the "free plane change" and Oberth effect you get from being so low don't even come close to making up for the penalty of being so deep in the gravity well. Edited November 20, 2015 by More Boosters

[Taki117]

Moho is no more expensive dV wise than anywhere else. The Key to getting to Moho is ignoring whatever transfer window you are using and eyeball it.

Check[URL="http://forum.kerbalspaceprogram.com/threads/61478-Oh-bugger-Injection-burn-at-Moho?p=835667&viewfull=1#post835667"] this thread[/URL] for probably the best tutorial on how to get to Moho I can find.

[paul23]

The main advantage of starting at a planet that is close to the sun is not more efficiency (notice that even though you have a higher speed your apoapsis is also quite low since Moho's orbit is near circular, so the oberth effect is still relative small compared to the total energy difference).
However you have very often launch windows, where Eloo & Moho align neatly to do a hohman (or whatever other) transfer.

For the similar reason I prefer my mining on mun/asteroids in lower orbits, at minmus I have to wait many days before minmus is aligned well enough to leave kerbin.

[PLAD]

I love running the numbers, and we can run the numbers for this one. I notice Eeloo's longitude of ascending node is at 50 degrees and Moho's at 70 degrees, so their orbits are not too far from coplanar. But...
Using Flyby Finder I see that, starting from a 20x20km orbit over Moho, and braking into a 20x20km orbit at Eeloo, the minimum start burn is about 4280m/s, and the minimum braking burn is about 1760m/s. Not with the same path though, the minimum total is about 6860m/s.
For a direct Kerbin to Eeloo flight, starting at 75x75km over Kerbin, the minimum start burn is about 2020m/s and the minimum braking burn is about 1010m/s, and the minimum total is about 3230m/s.
So going Kerbin-Eeloo is much cheaper than going Moho-Eeloo. I wondered about flybys, but the minimum to get to an Eve flyby from Moho is around 1070m/s, while the minimum from Kerbin to Eve is about 1030, so no sequence of flybys can be better from Moho than Kerbin, though it could be close.

[Kerbart]

[quote name='More Boosters'](...)
Edit: And as Snark answered, the "free plane change" and Oberth effect you get from being so low don't even come close to making up for the penalty of being so deep in the gravity well.[/QUOTE]

While nearly similar in inclination, the argument of the periapsis of Moho is 15°, and of Eeloo is 260°, nearly the opposite. Unless I'm wrong it means that effectively you're dealing with a 15° plane change as well, instead of the plane change being "free?"

[Jimbimbibble]

So, we've established its cheaper to go from kerbin to eeloo, but if you have a craft that can get to moho and you can refuel it there, then maybe you will have enough dV to get to eeloo and refuel again? Sounds like an interesting mission to me.

[cantab]

Arg of peri is where the closest point in the orbit to the Sun is. It doesn't affect the orbital plane at all.

[A35K]

Using [URL="http://alexmoon.github.io/ksp/#/Kerbin/100/Eeloo/30/false/ballistic/true/1/1"]this[/URL], the lowest possible delta-v from Kerbin to Eeloo is 3,524 m/s, taking 1 year and 108 days of travel (Earth time). From Moho to Eeloo, the lowest possible delta-v is 6,917 m/s, taking approximately the same time as from Kerbin. So there is no reason to go from Moho.

[Arugela]

I was thinking the same thing. But I was thinking you should go from eeloo to moho. I was thinking it may be a natural difficutly level thing. You start at kerbin. Go out to eeloo planet by planet. Then from Eeloo down to moho then Eve system. This would seem like it might follow a natural system of increase in DV or something for each destination and maybe follow some logical pattern.

I have yet to fully test this yet though. But my next mission is to go to Eeloo with a miner then do this very thing on the way back to kerbin. A round the world/Solar System trip going outwards first.

[More Boosters]

[quote name='Arugela']I was thinking the same thing. But I was thinking you should go from eeloo to moho. I was thinking it may be a natural difficutly level thing. You start at kerbin. Go out to eeloo planet by planet. Then from Eeloo down to moho then Eve system. This would seem like it might follow a natural system of increase in DV or something for each destination and maybe follow some logical pattern.

I have yet to fully test this yet though. But my next mission is to go to Eeloo with a miner then do this very thing on the way back to kerbin. A round the world/Solar System trip going outwards first.[/QUOTE]

Oh yeah, maybe you should look at the DV numbers regarding that.

[jarmund]

Pardon the useless post, but this has to be said: I want to make that trip now, regardless of any fuel-related benefits or lack thereof. Kerbin->Moho->Eeloo->Kerbin sounds like a beautiful trip.

[More Boosters]

[quote name='jarmund']Pardon the useless post, but this has to be said: I want to make that trip now, regardless of any fuel-related benefits or lack thereof. Kerbin->Moho->Eeloo->Kerbin sounds like a beautiful trip.[/QUOTE]

No problem at all, I'm glad I could inspire someone!