Fueling station at the edge of Kerbin SoI.

[painking]

Is this a good idea? The majority of an ejection burn for interplanetary transfer is just breaking out of Kerbin's SoI, so I could just get an orbit rendesvous with it from low orbit, refuel, and then head off into the solar system. I think it'd be good for Jool since it takes a lot of dV to move around it, and it sounds like a simpler alternative than building larger rockets.

Edited July 18, 2013 by painking

[rottielover]

Interesting idea. Not sure what it would take to pull that off, but I'm interested and will try it out.

I had been thinking about a fuel station just for Jool, but to pull it off would need to be mining Kethane I think.

[stupid_chris]

Is this a good idea? The majority of an ejection burn for interplanetary transfer is just breaking out of Kerbin's SoI, so I could just get an orbit rendesvous with it from low orbit, refuel, and then head off into the solar system. I think it'd be good for Jool since it takes a lot of dV to move around it, and it sounds like a simpler alternative than building larger rockets.

It has it's pros and it's cons honestly.

We'll start with the cons, it will be much more logical in the flow of idea this way. The Oberth effect stipulates than the faster your rocket is traveling, the more efficient it will be. This means, the lower your orbit, the less delta V you'll need to get out. This is weird and counter intuitive, but trust me, that's how things work. I'm not really up to explaining exactly how the Oberth effect works right now, someone probably will though.

The pros, well, you are starting with a full tank already far out of the SOI, so you'll be carrying more fuel to your destination.

However, the total amount of fuel you will use will be much much greater if you fill up at the edge of the SOI midway. All in all, it's usually better to just shoot straight off from low orbit.

[CCKinnison]

Seems possible, but resupply would be a pain. High Mun orbit or High Minmus orbit would probably be a more effective use of time in the long run, assuming you're using Kethane. Stock, your idea might work, but you're gonna end up with a lot of empty tankers somewhere.

It has it's pros and it's cons honestly.

We'll start with the cons, it will be much more logical in the flow of idea this way. The Oberth effect stipulates than the faster your rocket is traveling, the more efficient it will be. This means, the lower your orbit, the less delta V you'll need to get out. This is weird and counter intuitive, but trust me, that's how things work. I'm not really up to explaining exactly how the Oberth effect works right now, someone probably will though.

The pros, well, you are starting with a full tank already far out of the SOI, so you'll be carrying more fuel to your destination.

However, the total amount of fuel you will use will be much much greater if you fill up at the edge of the SOI midway. All in all, it's usually better to just shoot straight off from low orbit.

Okay, here's the ultimate in crazy for this...

2 (or more) stations, inclined about 5-10 degrees in orbits, oppositely, so they won't conflict around Kerbin. Very elliptical orbits - ~80 KM to edge of Kerbin SOI.

Match orbit, refuel, separate, then burn though Periapsis to get escape velocity towards inner or outer system as needed/desired.

Edited July 18, 2013 by CCKinnison

[Infinitas]

I have a refueling station in Minmus orbit, and a Kethane refinery on the surface. Of course, it'll only last so long as the Kethane does.

[painking]

The only reason I propose this is so that I can get smaller craft into deep space. I could build a big monster rocket with lots of fuel and go wherever I want, but I like my little-r rocket that looks nice and compact. Would I have to worry about a planet moving out of phase as I wait for the right phase angle since my orbit would be so large?

[stupid_chris]

The only reason I propose this is so that I can get smaller craft into deep space. I could build a big monster rocket with lots of fuel and go wherever I want, but I like my little-r rocket that looks nice and compact. Would I have to worry about a planet moving out of phase as I wait for the right phase angle since my orbit would be so large?

That would be the biggest problem, I forgot to mention.

Honestly you would be surprised. The rocket you would have to build to get to interplanetary space without a refueling at the edge of the SOI would barely be bigger than the one to go straight out, all of this because of the Oberth effect.

[Mr Shifty]

I put together a chart a while ago that shows most efficient launch altitudes for interplanetary Hohmann transfers. Most of the time, you want to be as close to your origin planet as possible to take advantage of the Oberth effect. Sometimes, particularly for transfers to a close planet, it's better to be at a higher altitude to make it easier to escape the gravity well. In only one case, Jool to Dres transfer, is it best to be as far as possible from the origin planet.

Edited July 18, 2013 by Mr Shifty

[Mr Shifty]

EDIT: Duplicate post - forum hiccough.

[painking]

Interesting stuff to know. Ok, thanks for the advice.