Optimal Kerbin space station location?

[Joolian42]

I was setting up a refueling station around Kerbin to serve as part of an interplanetary infrastructure, and I was trying to decide which altitude to put it at -- would it be best to put it at LKO, just above the atmosphere (80 km), at a very high Kerbin orbit (Kerbin-synchronous orbit), or in orbit around Minmus. Each one seems to have its own pros and cons:

LKO Pros:

-- easiest to reach from the ground (requires least dV)

-- will provide the departing spacecraft with the biggest benefit from the Oberth effect

LKO Cons:

-- wouldn't provide the highest "starting" altitude (starting at a lower altitude would mean I could have to burn more to get out of orbit, relative to a high orbit)

KSO Pros:

-- starts me in a higher orbit than LKO, potentially reducing dV required to escape from orbit

KSO Cons:

-- the higher orbit means I get less advantage from the Oberth effect, increasing the dV required to get out of orbit

Minmus Pros:

-- extremely high orbit potentially reduces dV required to escape from orbit by a large margin

Minmus Cons:

-- provides the least benefit from the Oberth effect out of all three options

So, in terms of reducing the total dV required to break out of Kerbin's SOI, which one of those locations would be best for a refueling station?

[Captain Sierra]

Personally, I prefer 100-120km orbit for space stations. I find there you get the easiest time rendezvousing because you have plenty of distance below for Hohmann transfer orbits. It also keeps you low enough to get a decent oberth effect lower orbit start which I have found outweighs the dV required to set you up in a higher starting orbit (assuming you do direct from KSC to desired altitude and don't utilize a parking orbit first).

[astropapi1]

At least you get the idea of the oberth effect. The ideal position for a "mid-way" station (refuel and go on), would be around 80 km. Yes, you'd have to burn for longer to break orbit, but you're going way faster and will spend much less dV when going to another planet.

[Guest]

Generally I like to put my station somewhere around Kerbin. 400km is about right since the only thing I'll be refueling at the station will be Mun taxis or refueling craft. There's no point trying to dock some ungainly interplanetary modular craft to an ungainly modular space station; best to bring the refueling craft to it. Leaving the station at 400km also keeps LKO uncluttered.

As always, YMMV.

[annallia]

My station orbits at 320km. True it does require more fuel to get to it initially it is however not too horribly bad + my refueling rig was already designed to reach the Mun (rig for refueling the station not refueling station) so it has no trouble getting into that high of an orbit.

That is for Kerbin. Other planets I don't have a station around yet but I do use refueling satellites which are basically mini-stations that I keep in the lowest possible orbit, specially the ones around Eve.

[Tw1]

I tend to use 400-800, for easier rendezvous, for Kerbin, but I've only build multi function stations so far.

There was someone who had calculated the ideal heights for transfers to other planets, the idea being that you could put a tanker into those orbits, and interplanetary flights would refuel there before departing.

[dlmarti]

I either put it about 250km, so I can do warps, or I put it out at Minimus to help with refueling interplanetary missions.

[Joolian42]

As far as interplanetary missions go, wouldn't lower orbits be better, to take advantage of the Oberth effect? Some kind of station around Minmus (or the Mun) would be great for Kethane mining to refuel the fuel tanker, but it would seem like the best location for the fuel tanker itself would be LKO -- at least, that's what it seems like to me. Of course, I'm not an expert on KSP (I'm rather new to it), so I could certainly be wrong.

[Affan]

I would recommend putting the station at 95-100 km up as it gives space for you to position other space station modules to have slightly higher or slightly lower orbits to get closer to the station. You still get a decent starting altitude but still gets good Oberth effect.

I wouldn't recommend putting it in orbit round minmus, it would take too long to get every module up and it would be more difficult due to the off center orbit of minmus

[Kimberly]

As far as interplanetary missions go, wouldn't lower orbits be better, to take advantage of the Oberth effect? Some kind of station around Minmus (or the Mun) would be great for Kethane mining to refuel the fuel tanker, but it would seem like the best location for the fuel tanker itself would be LKO -- at least, that's what it seems like to me. Of course, I'm not an expert on KSP (I'm rather new to it), so I could certainly be wrong.

There are certain ideal orbits for transferring to each planet. There is a net loss of delta-V by boosting up to those orbits, but if you have a refueling station there, your craft can make do with a significantly lower fuel capacity. If you're not willing to have a fuel depot for each planet you want to burn to, it's best to just keep your depot at LKO. A Minmus refueling station isn't efficient.

[hjmott]

why not put one at around 150 km, and another orbiting minmus, or in that general area?

[LoneRider]

My station is at about 200km, but the main reason for this is fuel efficiency with special engines. For interplanetary flights i usually use the thermonuclear engines, because they are by far more efficient out of atmosphere than any other engine (about 2 - 2.5x as fuel efficient). Therefore i am using a very unusual way when starting: my rockets go up straight at about 15-20km, then going at about 60 degrees east. Then the first stage is empty when at about 50km, but with enough speed to reach 70km easily (usually the rocket will go up to about 100-130km) and all parts from the first stage go back to kerbin surface. From 70km height i start the nuclear engines, which take a LONG time to reach a good orbit, depending on weight. When reaching a mostly circular orbit altitude is at about 160-180km. Therefore 200km is a good height. The usual starting way (turning to east at 5-15km and trying to reach a low orbit as soon as possible) leaves me with a far longer time in the atmosphere, where the nuclear engines are inefficient and sometimes dont have anough thrust to get the rocket out of atmosphere.

One reason not to go too close to kerbin: max warp speed. Since i usually dont use mechjeb, i often have to wait at the station until the optimal time to start interplanetary travels. Therefore maybe a "waiting station" at about 600-800km would also be useful - first refuel close to kerbin, then go to about 800km to wait. On the other hand it would be enough to have a good timing and plan so you dont have to wait too long while in space

[elkar]

160km as a LKO. anything less or more is wrong by me

[frik]

There are certain ideal orbits for transferring to each planet. There is a net loss of delta-V by boosting up to those orbits, but if you have a refueling station there, your craft can make do with a significantly lower fuel capacity. If you're not willing to have a fuel depot for each planet you want to burn to, it's best to just keep your depot at LKO. A Minmus refueling station isn't efficient.

I saw once table showing Oberth effect, and interplanetary transfers, that would show where each such station should be, but I cand fit this diagram now - has anyone got it?

[RW-1]

Kerbal Station One is currently at 300-320km.

Nice enough, though I can change it's altitude should I wish it.

[FREEFALL1984]

If you're willing to be a little lax with your interplanetary launch windows (ie within 3 hours) then a KSO might be useful, especially if the KSO landed you almost directly on an optimal launch path, you would never have to wait rendezvous with the station or spend time "chasing" the station around kerbin in fact if you where using MJ you could have the accent autopilot almost plop you on a rendezvous every time you launch a ship, (depending on T/w among other factors) Then when the transfer window comes around you could just expend a couple of hundred m/s of dv to drop your periapsis to within 80km and do your transfer burn at peri, the periapsis reduction burn would increase your orbital velocity anyway so as long as your prepared to get all of your ships and fuel up to KSO which requires roughly 1km/s of DV then it sounds like a safe bet.

[cantab]

I wouldn't even consider KSO. It takes quite a bit of extra fuel to reach from the launch, and you lose Oberth effect benefits.

LKO is the obvious choice, but as others have said I might go a bit higher than your typical parking orbits. That keeps your station out of the way of other stuff, especially important if you have persistent debris turned on (though your station is only in danger when it's in physics range of what you're flying). It'll also permit a faster timewarp.

A Minmus or Mun station is a quite different proposition. I wouldn't see it as an alternative to an LKO one, but a complement, though I'm not entirely sure what it'd be used for.

[astroboy820]

Why not build two stations? Build both in LKO, add a few Rockomax and shoot one out to Minimus

[Claw]

Guys, this is an old thread that was necro'd for a question. So probably no need to restart the "where to park" debate.

I saw once table showing Oberth effect, and interplanetary transfers, that would show where each such station should be, but I cand fit this diagram now - has anyone got it?

Perhaps you're asking for this?

It's from this thread:

http://forum.kerbalspaceprogram.com/threads/75542-Should-I-build-a-refueling-station-at-the-edge-of-Kerbins-SOI/page2

[Eric S]

A Minmus refueling station isn't efficient.

It's potentially efficient (depending on how you measure efficiency), but can have problems. The idea is that if you're using a Minmus refueling station, you do not burn for planetary transfer directly from Minmus orbit, but rather depart Minmus in a Minmus-retrograde direction so that you have a periapsis in the LKO region, and then burn ship-prograde at your periapsis. Net result is planetary transfers for about 500-600 m/s less post-refueling delta-v than you'd spend boosting directly from LKO. The timing can be a pain since Minmus has a 12 day orbit, but most transfer windows are at least that wide at a cost of less than 20% of the fuel this can save.

That said, I mostly use that technique for self-refueling motherships, though to be honest, it's because I like doing shakedown runs close enough to Kerbin that if there's a design flaw I can fix/rescue easier than I can if the ship breaks down in the Solar SoI. It's fun to do it that way a few times, but for craft that aren't self-refueling, it's generally not worth saving the 500-600 m/s delta-v.

[O-Doc]

I have an LKO base at 250km and KSO base for interplanetary transfers. It's 230m/s dV to get your periapsis down to ~70km for a burn out of Kerbin SOI. In the end the KSO doesn't save a massive amount as a high Minmus base does but, it has more flexibility and a better window for Mun slingshots burning up or down.

I recommend you put up small bases all around the Kerbin system and find out what works best for you.

[thereaverofdarkness]

I put mine at 300km. That way it's both far enough out to warp at 1000x, and far enough that a ship at LKO (<100km) can catch up with it in just a few orbits, but close enough that it takes very little fuel to transfer to it from LKO. The minimum distance for this is 240km.

[FREEFALL1984]

I wouldn't even consider KSO. It takes quite a bit of extra fuel to reach from the launch, and you lose Oberth effect benefits.

While I agree it might not be as efficient as an LKO the only extra fuel you would need would be the fuel required to circularize the KSO and rendezvous (which would be super easy) and the fuel required to drop the orbit back to 75km ready for the interplanetary burn. it would make rendezvous a really easy task since the space station would almost always be in the exact correct location. So it would kind of be trading time efficiency for fuel efficiency.

[frik]

Perhaps you're asking for this?

It's from this thread:

http://forum.kerbalspaceprogram.com/threads/75542-Should-I-build-a-refueling-station-at-the-edge-of-Kerbins-SOI/page2

Exactly! Thanks a lot, I knew that it was in refueling station location thread, but couldn't find proper one...

[bflave13]

How do you refuel once on the station?