Best place to put a space station?

[Gibster]

I'm getting ready to build a big utility station in my career mode and I was wondering where you guys think the best place to park a station in the Kerbin system is. Low Kerbin Orbit, High Kerbin Orbit, Mun, or Minmus? I want a place that will serve as a nice rendezvous and refueling area as I get ready to start launching reusable nuclear ships (that'll hopefully serve on multiple missions). 

[Guest]

All are good except maybe HKO.

LKO pros -- easy to get to, LKO is a good, straightforward place to launch interplanetary missions, best place to park stuff waiting for a recovery mission

Mun pros -- relatively easy to get to, also good straightforward place to launch interplanetary missions, relatively easy to set up fuel production on the surface

Minmus pros -- easiest to set up fuel production on the surface, but some interplanetary missions will require rather advanced orbital mechanics as you'll probably want to slingshot off Kerbin, and getting there is something of a PITA

I can't think of any advantages of HKO; it's more expensive to get to from Kerbin but doesn't do anything the other spots don't. Personally I'd go with either Mun or Minmus; LKO is so easy to get to that you don't really need a station there; just go directly there and do whatever you want to do.

[Aegolius13]

LKO, Minmus and the Mun are all pretty good options, depending on your playstyle.  The one I would not go with is high Kerbin orbit... you lose the Oberth effect without any discernible benefit.  

If you're mining fuel from one of the moons, or in the process of doing an extended science campaign there, that probably weighs in favor of putting the station at the same location.   

My personal favorite for staging interplanetary missions is the Mun (using fuel mined there).  The short orbital period and lack of inclination makes it easy to line up the launch windows.  And by refueling up the gravity well from Kerbin, you can extend your range.  Yeah, mining on Minmus is a little easier, but the difference is not that big.

All that said, eventually you'll probably want to have stations around each body, so you can do whatever works best for that particular mission. 

1 minute ago, Brikoleur said:

All are good except maybe HKO.

Ninja'd...

[Kryxal]

If you decide on the LKO station, try to make sure it's not TOO low ... starting at 250 km is actually better for any reasonable destination, and makes the ejection burn cleaner since you cover less of an arc and have more space before you get TOO low.

[GrouchyDevotee]

Low Kerban Orbit, 150km is nice and useful as a fuel depot and recovery station... Mun Station is useful for storing fuel if you are refining. I haven't tried a station at Minmus.

But, why not build a Base and a Space-station at all of them?

[Dafni]

Back in the old days of KSP, and in cases where performance of the game was an issue, it was suggested to have the LKO stations above 250km. Apparently 250km was the distance for the surface to render in a higher detail or something like that, sacrificing a chunk of performance.

Anybody know if this is still the case these days?

[blakemw]

I like 600km because it's not too hard to get to from Kerbin's surface, and it's also a good deal easier to get to from Minmus than a very low orbit and a higher orbit makes rendezvous more convenient and allows maximum time warp. Also check out the concept of a "gate orbit", for any given destination (Duna, Jool etc) the cheapest orbit to eject from will not be the lowest one but actually a higher orbit: up to a point being further out of a gravity well is more beneficial than more oberth effect, this has to be taken with a grain of salt because the dV cost of getting to the gate orbit will be greater than the dV savings from using it. So it's only useful if you can refuel - but refueling is a good use for a space station! And if you're bringing the fuel from Minmus rather than Kerbin then it's pretty much a win-win to use a higher altitude, and even if you're bringing it from Kerbin you'll probably be doing so in bulk so it's not a big deal burning a bit of extra fuel - it'll give your small missions more dV to work with once their little tanks are full.

Edited February 26, 2018 by blakemw

[Gargamel]

10 hours ago, Brikoleur said:

I can't think of any advantages of HKO; it's more expensive to get to from Kerbin but doesn't do anything the other spots don't. Personally I'd go with either Mun or Minmus; LKO is so easy to get to that you don't really need a station there; just go directly there and do whatever you want to do.

I managed to land a Class E Asteroid in HKO, (about 3 Mm), which is a significant chunk of the DV required to dig your way out of the gravity well.  I setup ISRU and a docking port on there.  All ships leaving Kerbin for a mission are built in LKO, or launched to LKO, transfer upto the refueling station, and then park slightly higher (like 30 more Dv total) until their transfer window arrives.

But without a source of fuel in HKO, it's really not a great place for a station.  Costs too much to ferry fuel there from Kerbin, and you might as well go higher if you plan on doing that.  And if you go higher, you might as well ISRU up from one of the moons, as bringing fuel/ore down to a HKO station is just working backwards, so put your station in orbit around one of the moons. 

The advantage of a LKO station is if you are trying to data farm the science labs.  Bringing repeated science experiments back to a LKO station and converting it to data will yield more science points than recovering them. 

[ajburges]

12 hours ago, Dafni said:

Back in the old days of KSP, and in cases where performance of the game was an issue, it was suggested to have the LKO stations above 250km. Apparently 250km was the distance for the surface to render in a higher detail or something like that, sacrificing a chunk of performance.

Anybody know if this is still the case these days?

That is still the case to my knowledge. The actual altitude is a little lower. The second reason to choose 250 km is to achieve 1000x time warp (unlocked at 240 km).

[Dafni]

10 hours ago, ajburges said:

That is still the case to my knowledge. The actual altitude is a little lower. The second reason to choose 250 km is to achieve 1000x time warp (unlocked at 240 km).

Okay then, thank you. And yeah, the additional time warp speed is nice to have too, for those fuel efficient slow approach rendez-vous situations etc.

[Curveball Anders]

15 hours ago, ajburges said:

That is still the case to my knowledge. The actual altitude is a little lower. The second reason to choose 250 km is to achieve 1000x time warp (unlocked at 240 km).

It's my favourite station orbit too.

No render lag, 1000x warp available, easy hohmann from a 75-80 launch orbit and an easy retro burn for re-entry.

[Tyko]

On 2/25/2018 at 9:58 PM, Brikoleur said:

I can't think of any advantages of HKO; it's more expensive to get to from Kerbin but doesn't do anything the other spots don't. Personally I'd go with either Mun or Minmus; LKO is so easy to get to that you don't really need a station there; just go directly there and do whatever you want to do.

The one big advantage to HKO - actually more like cis-lunar really - is lower dv costs to reach station when returning to Kerbin local system. The deeper into Kerbin's gravity well, the faster you're going and the more DV you'll need to enter orbit.

Your initial launches will cost more DV to get to the station, but if you're running motherships, ferries or other craft that operate in orbit it might be worth the fuel savings. In my most advanced game I had an LKO transfer station and my main refueling / mission station at 7500km. I was using nuclear ferries to move between the two stations. 

Edited February 27, 2018 by Tyko

[ajburges]

On 2/27/2018 at 7:35 AM, Tyko said:

The one big advantage to HKO - actually more like cis-lunar really - is lower dv costs to reach station when returning to Kerbin local system. The deeper into Kerbin's gravity well, the faster you're going and the more DV you'll need to enter orbit.

Your initial launches will cost more DV to get to the station, but if you're running motherships, ferries or other craft that operate in orbit it might be worth the fuel savings. In my most advanced game I had an LKO transfer station and my main refueling / mission station at 7500km. I was using nuclear ferries to move between the two stations. 

No, not really. Cis-Munar orbits only offer optimal ejection/capture dV for Eve and Duna. Do the math and you find that optimal ejection for anything else is lower due to the Oberth effect. You also need to spend the dV to get your fuel reserves there.

If you want optimal Eve/Duna ejections with refueling, best to have a Munar station IMO.

[Spricigo]

A idea no one mentioned is to not have a station, instead have fuel tankers(and other utility vessels) that can meet each ship in need in the most convenient orbit.

[Warzouz]

I would say that LKO space stations quiet useless. Refueling rockets from Minmus is very waste of time job. It's fun to do it once or twice, but boring then...

Launching then refueling is time consuming and increase the price tag. You need to add RCS devices and tanks and fuel to get rendez-vous.

LKO space stations may be interesting if you want to reuse you interplanetary stages for other missions. But again, it's time consuming. I'm doing that right know, and figured it's even easier to relaunch the full stuff.

On the opposit, using a Mun station to refuel to go to the mun us VERY useful : you don't need to get back to Kerbin ! It's even more useful dealing with Duna, Jool or any other planet.

here is an example (bit old)

 

[XLjedi]

I put engines on my stations and now refer to them as Orbital Command Vessels. 

Here's my mid-career Sci-Raker corvette that I recently launched.  It destroyed most of the science tree within a year just piddling around Kerbin, Mun, and Minmus...

Notice the claws on the front that it uses to scavenge fuel from the stages of other various smaller satellites that I have to put in orbit.  My preference would've been a stock solution for orbital assembly rather than a launch like this. But the end result is a sci-data research station in orbit that is capable of self-relocation, 2000 dV to start, and can pillage unused fuel from other sources.

Edited March 1, 2018 by XLjedi

[Curveball Anders]

On 2018-03-01 at 1:09 PM, Spricigo said:

A idea no one mentioned is to not have a station, instead have fuel tankers(and other utility vessels) that can meet each ship in need in the most convenient orbit.

I usually have a robotic tug/tanker docked to my 250km station.

Fully capable of topping up or rescuing any returned vessel that has managed to entry some form of Kerbin orbit.

The same little tug can is also used to de-orbit empty tanks and other debris.

 

[Daniel Prates]

On 26/02/2018 at 6:47 PM, ajburges said:

That is still the case to my knowledge. The actual altitude is a little lower. The second reason to choose 250 km is to achieve 1000x time warp (unlocked at 240 km).

Thats what I do. Mainly for the timewarping advantages. If it is going to be a busy station,  placing it in 100kms or so is a pain.

[Hotel26]

A stimulating discussion (as it's caused some revision of my fleet as well as ideas).

My conclusion is that I will stay with LKO but I am likely to use multiple stations now instead of just one.

My objectives for a Kerbin space station are a) fuel dump, b) assembly point, c) temporary habitat for transferring crew/pax.  The biggest disadvantage for me of LKO is the long rendez-vous times incurred when the target orbit is close to the minimum atmospheric escape.  This is a disadvantage primarily only when I a) don't bother to coordinate my launch time and b) am not multiplexing mission steps via the Very Salubrious Kerbal Alarm Clock [Best Mod Ever].

For reference, Kerbin Orbit Period:

100km     32m
120km     34m
160km     36m
260km     44m

So my resolutions are to establish multiple stations (3), but at 125km instead of at 100km [faster warp]; coordinate my launches more diligently at KSC; and I've introduced a much bigger fuel pod for use with my Hawk lander/tug.  This gives the option of sending the Hawk on refuel jobs for an easier rendez-vous and including the option to completely top-up missions assembled that have been moved to 250km (say) for more efficient departure.

I once tried a Mun-originated departure.  I soon realized that the orbital speed of the Mun and then that of the craft orbiting it, summed up are going to be far less (in the Kerbol) reference-frame than your standard Kerbin orbit speed.  That necessitates an initial slingshot maneuver via LKO to get going, which is another complication for interplanetary transit planning.  Doable for sure, but not by me, a hopeless plodder.  In addition, I worked hard to acquire the capability to boost a tremendous load of fuel into LKO from Kerbin and -- if I were a betting man -- I might wager I could always load fuel faster with less effort than can be done from the surface of the Mun.

Minmus: fageddabahtit...  [general consensus]

One more interesting concept from this discussion is the asteroid thingy.  I think I'm going to take a shot at it but only because it's bizarre.  My Kerbals will get a chuckle out of it.

Edited March 11, 2018 by Hotel26

[XtraChrisP]

@Hotel26

Sir I'm glad you articulated your use of LKO stations so artfully.  I use them for exactly those reasons, and I also recognize the need to synchronize launches with the orbital position of the station (on account of how many I've screwed up in the past )

I'm curious about this bulk fuel capability you speak of, and if you haven't tried it, getting a Class E asteroid into a useful orbit can be quite satisfying.  Good luck!

[Hotel26]

4 hours ago, XtraChrisP said:

I'm curious about this bulk fuel capability you speak of

Thanks for your interest, @XtraChrisP.  Two shots, one of the Hawk lander/tug and the second of the new fuel pod I mentioned.

Until recently, vehicles had to rendez-vous with a space station to refuel in preparation for interplanetary departures.  In addition, having many vehicles attached to a space station eventually becomes an invitation for a Kraken gate-crashing party.  So I'm thinking that the Hawk/fuel pod combination might be a nimble method for taking fuel to a nearby ship.

One more component in my fuel chain may be found here: Minotaur.

I will definitely give the asteroid capture a go.  Do you recommend trying a smaller class of asteroid first, or go directly to Class E?

[ave369]

Minmus, Minmus, Minmus!

 

Pros:

* Shallow gravity well means that orbital maneuvers are cheap and easy. Easy rendezvous, easy docking, extremely low dV cost.

* Shallow gravity well means easy trips to the surface and back. This means easy science grinding by delivering samples from each Minmus biome to the station, this means easy fuel production.

 

Cons:

* Slightly harder to get to than LKO.

* Slightly less efficient interplanetary travel. You can easily exit Minmus orbit to interplanetary space, but you lose the benefit of the Oberth effect. However, this drawback is only significant for those who make micro-optimized mosquito craft that travel to Eeloo on Ants.

[Hotel26]

Here's an interesting idea -- and, yes, I bet many have already discovered this.

I just rendez-voused a big, hulking ship with a space station.  I didn't want to dock it, but just keep it close.  They are currently 245m apart and the target-relative speed is 0.4 m/s, orbiting the Mun at an altitude of 50km.  How fast are they drifting apart?

Well, before you answer that, the orbital period of these two has been adjusted by me to be just 1 (one) millisecond apart.  (As close as I could get it with RCS.)  51m 21.588s and .587.

So the question really is: "how far apart can they drift?"  And the answer is "not much".  The closer you get them when you synchronize, the less it's likely to be and very likely always within quick "vessel switch" range during the whole orbit.

I really like this: "invisible tethering"!  A few hundred meters is a very easy trip for a fuel tender to make from an OFD (Orbital Fuel Dump) to a client vessel.

OK, so here's another good question: "why would you want to do that?".  (Here's my answer: "sick to death of the Kraken".)

[Somebody's gonna chime in to ask incredulously: "you didn't know that?"    Very good.  Take a number...]

Update: it's also really easy to re-adjust.  Align pro/retro-grade and bring up the Rendez-vous Planner (if you use MechJeb) and use RCS to simply dial-in a shorter or longer orbital period that brings your closest encounter back down really low.  Set a KAC alarm for one loop later.  Synchronize orbital periods again.

---

After I read this thread, I decided to put five space stations into orbit around Kerbin.  One of the CommNet tutorials describes the usage of the Law of Cosines.  You can use it to adjust the orbital period of one ship to acquire a rather exact line-of-sight distance to another, e.g. the distance equivalent to 72 degrees ahead in the orbit.  You can get within a few meters.  But it is then tuning the orbital period down to milliseconds that really holds tight formation.

Edited March 25, 2018 by Hotel26

[Tyko]

If the target relative speed is 0.4m/s, then that's how fast their distance is changing, but it doesn't tell you if they're getting closer at that speed or further apart.

Physics range is just over 2 kilometers - within physics range you can use the brackets [ ] to switch back and forth

[FinalFan]

3 hours ago, Daveroski said:

I meant what I said.

The conversation was about what altitude to build stations and why.

Other people, who are smart enough to be able to read more than the last few lines of a conversation, understood.

And actually even if you want to put it the other way then going from an 80K orbit of Kerbin to the Mun works out more economical than going from a 160k orbit of Kerbin to the Mun because you have to expend fuel to attain the orbit in the first place. Unless you cheat. I suppose you might have an argument. So if you think about it, I assume you can think, you are still WRONG. Maybe it's because I try to speak in such a way that people who don't know the terminology can still understand. Maybe it's because you and people like you feel the need to demonstrate that they have picked up a few crumbs of learning. Well just for you I can tell you that your input so far is a rather good example of floccinaucinihilipilification.

Dave, suppose you had a refueling station at 80km and a refueling station at 150km.  Which of these would leave you with more fuel remaining in your ship when you got to the Mun? 

The answer may be obvious to you and me, and thus you attack me for being overly pedantic about it, but just look at papuchalk's post.  You say no one could possibly misunderstand your post as literally meaning that 80km-->Mun is less dV than 150km-->Mun.  I rest my case.  You are contributing to the miseducation of other players.  Also, as someone who is interested in new words, I looked up that one, and based on my findings you used it wrong.  What a shock. 

1 hour ago, papuchalk said:

I agree with Daveroski.

Going to Mun from 80 km of Kerbin is more economical than going to Mun from 150 km. If you dont believe, try it in game, or use delta V calculator here

https://13375.de/KSPDeltaVMap/

The fact is, on close orbit 80km you have very high speed, so you need just "small" burn to gain a little more speed. While on 150km orbit you have much lower speed. That means, you have to make longer burn to gain speed again.

I think you are probably thinking it wrongly, because you dont consider 150 km to be a CIRCULAR orbit, but you are thinking about elliptical, with one side of orbit being still on 80 km , and the other side to be 150 km. That is different, because obviously you have that high speed when your ship is on 80km at Kerbin. However if you are speaking about really CIRCULAR orbit, you need extra delta v to get elliptical orbit 80/150  to be 150/150. And that is not eonomical at all.

Suppose you were DEORBITING from the Mun.  Would you be going faster at your Kerbin periapsis if you put it at 150km, or would it be faster if you put it at 80km?  Would it take more dV to circularize the 150km periapsis, or the 80km periapsis?  This is exactly the reverse situation of going to the Mun from those places.  Both questions have the same answer, and I know this is true because if it wasn't then Dave would have beaten me over the head with it by now.  Instead he falls back on his argument about the total dV to get from the ground to 150km and circularize and then go to the Mun is more than to circularize at 80km and then go to the Mun.