Mun or Minmus (For orbital fuel refinery)

[Squidiness]

Ok, so I'm looking into building an "Orbital Fuel Refinery" station around either the Mun or Minmus, and my station will have 3 sections: Crew Quarters (pretty self-explanatory), Fuel Canisters (and a lot of them), and a lander, but not any old lander; the lander undocks from the station in Low (Mun or Minmus) Orbit, lands (duh), mines for ore, lifts off, docks to the station, and finally the ore is refined into fuel to be stored in the fuel canisters, and repeat. With all that being said, which moon (Mun or Minmus) should this station orbit? Thanks in advance!

[ottothesilent]

I happen to prefer the Mun, but for pure practicality, Minmus has the advantage of lower gravity and orbital velocity, meaning that you can lift more ore with less fuel. So, consider Minmus.

[Squidiness]

Thanks a million!

Btw, if Minmus is the practical choice, why the Mun?

[Jarin]

1 hour ago, ottothesilent said:

I happen to prefer the Mun

Any particular reason? I'm just curious, since I tend to avoid the Mun like the plague.

[sardia]

8 minutes ago, Jarin said:

Any particular reason? I'm just curious, since I tend to avoid the Mun like the plague.

It's closer to your transfer stage. Instead of 2 day trip, it's 6 hours to get your fuel to your duna lander or etc etc.

[Jarin]

18 minutes ago, sardia said:

It's closer to your transfer stage. Instead of 2 day trip, it's 6 hours to get your fuel to your duna lander or etc etc.

Fair enough. I just hate how much dV landing and takeoff requires, but yeah, the transfers between Minmus and LKO do take a while, especially if you're being at all efficient; at which point the trip becomes 6-7 days.

[ottothesilent]

58 minutes ago, Jarin said:

Any particular reason? I'm just curious, since I tend to avoid the Mun like the plague.

I just don't have any particular affection for Minmus. I like the Mun's looks, terrain, and gravity. Minmus may take less DV to land and return, but I absolutely hate the terrain. Just my opinion, of course, and you're certainly entitled to your own.

[Squidiness]

Btw should the ISRU be on the lander or can it be on the station? I have no idea how ISRU's work

[Squidiness]

2 hours ago, sardia said:

It's closer to your transfer stage. Instead of 2 day trip, it's 6 hours to get your fuel to your duna lander or etc etc.

Can't you just time warp? Unless I have some contracts to do, I have no problem carrying out an 85 year mission with the help of time warp

[Aegolius13]

What are you doing with your fuel?  If you're sending it back to Kerbin, it's probably a slight advantage to Minmus due to lower gravity.  If you're using it as a waypoint for interplanetary vessels, I'd go with the Mun.  Since it orbits a lot faster, you'll likely be closer to the ideal transfer window at the time the Mun is at the right place in its orbit.  

On the other hand, maybe the best answer is: one of each!  Especially if you plan to do have activity on both moons. 

[Sharpy]

1 hour ago, Squidiness said:

Btw should the ISRU be on the lander or can it be on the station? I have no idea how ISRU's work

The ISRU converts ore to fuel so if there are no (big) fuel tanks to fill, there is no specific benefit to take it with you on each round-trip. Either take *everything* to the surface - drills, a token amount of ore tanks, ISRU and huge fuel tanks, or take drills and ore tanks (and an engineer!) down. Your setup will be bigger as you'll need large ore tanks hauling the ore, and you won't be able to use the same fuel tanks for flight and refueling others. You might consider two landers too, one drilling, one providing ore to the station. (unless you leave enough big ore tanks on the station).

Generally, rule#1, the drilling craft must have an engineer on board, as experienced as you can afford. Otherwise the drilling speed will be absolutely pathetic. Rule#2: if you process freshly drilled ore directly to fuel, you need just one smallest ore tank for all your needs - ISRU will most likely be depleting it faster than drills can fill it. So, hauling fuel saves more mass than hauling ore.

And don't forget radiators. Thermal efficiency is a difference between 100% output and 3% output...

[Blaarkies]

Don't shuttle ore up from the Mun, to do that you need to land with enough fuel reserves to lift all that ore...that fuel needs to come from somewhere(that ore won't convert back to more fuel than is used by the lander)

ISRU works like @Sharpy explained. It takes electricity and Ore, converts that in to fuel and heat. The small ISRU weighs less, but it is very slow(it uses 10 times as much ore for a single unit of fuel production). Get your highest level Engineer on that ISRU craft(inside a command pod of course). level-0 engineer gives 5x ore mining rate, and a level-5 engineer gives 25x mining rate. Any mid-level engineer will bottleneck your ISRU with only 2 big drills, use that to your advantage.

So all in all, refining should happen on the surface(mining base with fuel depot that you just "klaw" onto with a fuel shuttle?)

I much prefer the least amount of effort per fuel unit...build a lander with 2x 3.75m fuel tanks, some MK3 LF tank, lots of nukes, ISRU stuff and then land the entire ship on the surface. Give it a week or so to fill up, take off and put it back in orbit. Now you also have a fuel depot in orbit for other craft. When you finally emptied the 160tons of fuel into other craft, just go land again, rinse and repeat.

[sardia]

3 hours ago, Squidiness said:

Can't you just time warp? Unless I have some contracts to do, I have no problem carrying out an 85 year mission with the help of time warp

It uses up more life support.

Edit: Well, maybe not. With judicious use of probes, there won't be any excessive life support use. I think the mun does provide better practice landing sites than minmus does. Minmus is too easy, but the Mun is a good testbed for airless body landings.

Edited December 30, 2016 by sardia

[Sharpy]

4 hours ago, sardia said:

Minmus is too easy, but the Mun is a good testbed for airless body landings.

If your goal is fuel delivery though, it makes sense not to burn most of it on return to orbit though.

[N4CDLAW]

I used to use Minmus for my refueling needs, with the refinery and fuel storage in orbit and the miner and ore storage on a lander. It worked and was the most resource efficient option. However, in more recent games I've switched to the Mun for a few reasons:

1) Much easier to hit transfer windows from Mun orbit when doing interplanetary missions after refueling. This was my main reason to switch.

2) Less in-game time for when said transfer window sorta snuck up on me.

3) Mun generally has better ore concentrations, so less in-game time mining.

4) Started using a fuel depot in low Kerbin orbit when getting into reusable space planes, The mining lander I'd designed had a hard time achieving a 100k orbit over Kerbin when I chose to deliver ore from Minmus to the fuel depot there, it just didn't have the delta-V. Worked fine from the Mun, though.

5) Routine landings on the Mun prepared my "flying insticts" for interplanetary visits better than Minmus. I'd gotten to accustom to Minmus' "barely there" gravity and low delta-V landings and was getting into trouble during other landings when I stopped paying attention. 

Either way works, but in the end, Minmus was better because it saved resources; but those resources were free anyway, so... I prefer the Mun. 

[Squidiness]

17 hours ago, sardia said:

It uses up more life support.

Edit: Well, maybe not. With judicious use of probes, there won't be any excessive life support use. I think the mun does provide better practice landing sites than minmus does. Minmus is too easy, but the Mun is a good testbed for airless body landings.

Life support isn't in KSP...

[DrunkenKerbalnaut]

If I understand correctly, a few of you are mining on the surface, then transporting the ore to an orbital refinery. My refineries are on the surface, and my lander only hauls fuel to orbit. Is there a reason I should consider refining in orbit? At first glance, it seems cheaper to do it my way. What's the justification?

[Superfluous J]

1 hour ago, DrunkenKerbalnaut said:

If I understand correctly, a few of you are mining on the surface, then transporting the ore to an orbital refinery. My refineries are on the surface, and my lander only hauls fuel to orbit. Is there a reason I should consider refining in orbit? At first glance, it seems cheaper to do it my way. What's the justification?

If you use Extraplanetary Launchpads or any other mod that converts ore into something else, it's nice to have ore in space so you can decide what to do with it later. Or at the very least, not have to transport multiple things.

After doing this for several weeks on several worlds, I'm not sure that convenience is worth it. It really sucks when you arrive at Moho running on fumes and don't have a way to make fuel on the surface

[DrunkenKerbalnaut]

27 minutes ago, 5thHorseman said:

"... Extraplanetary Launchpads..."

Hadn't thought of that. Thanks. I've never used the mod, but I understand where your coming from. 

Another reason that just came to me: elliptical and/or polar orbits can yield longer periods of sun exposure, providing a refinery with more solar power. I don't really see this being a deciding factor, though. I don't imagine many people sit and wait while their refinery crunches 50 tons of ore. 

[sardia]

16 hours ago, DrunkenKerbalnaut said:

Hadn't thought of that. Thanks. I've never used the mod, but I understand where your coming from. 

Another reason that just came to me: elliptical and/or polar orbits can yield longer periods of sun exposure, providing a refinery with more solar power. I don't really see this being a deciding factor, though. I don't imagine many people sit and wait while their refinery crunches 50 tons of ore. 

You'd be surprised what people value. Some people have no problem time warping to get everything done. I've done it too. You need to think of your own personal play time as a resource too. 

 

Say you have a refinery on lathe, and your target is in orbit around jool.  Do you land your fuel tug, dock wait for it to refine, launch, dock with your fuel transport, and then dock to your target ship? Or do you just land with your Omni refinery transport, mine, and then take off straight for your target ship? 

You either save fuel, or you save time, or you save time warping. *

 

* I've purposely spent more fuel to get a bigger orbit just to be able to time warp faster so I physically spent less time waiting. I've also done the reverse, where I spent barely any fuel, but a lot of time with limited time warping. 

[Wcmille]

Refining Ore in orbit offers a playability advantage. You switch the ISRU on, and then everything auto-refuels. You don't have to care about the type of fuel or where the tank is, it just gets refueled.

Here's my Mun-rated hauler. It lands nearly empty, with empty rocket fuel tanks, and the liquid fuel about half-full. The poodles aren't used for descent. To launch, Poodles and Nervs get it up into the air. The Poodles cut out at about 8000m, and the NERVs get it to the station. I believe the RCS are balanced for docking (full ore, empty rockets, half-full liquid).

[DrunkenKerbalnaut]

1 hour ago, Wcmille said:

 You don't have to care about the type of fuel or where the tank is, it just gets refueled.

Say no more. That sounds pretty damned convenient haha. 

[jackellice]

I never thought of putting the OPD in orbit around the mun. I thought it would have been best to place it in LKO. Because it's a whole lot easier moving to and fro Mun's orbit and LKO for the refueler than it is for a launch vehicle to bring a craft up that needs 1 km/s more to reach the Mun and circularize.

Plus, the Oberth effect around Kerbin is a whole lot stronger.

Edited December 31, 2016 by jackellice

[Superfluous J]

28 minutes ago, jackellice said:

I never thought of putting the OPD in orbit around the mun. I thought it would have been best to place it in LKO. Because it's a whole lot easier moving to and fro Mun's orbit and LKO for the refueler than it is for a launch vehicle to bring a craft up that needs 1 km/s more to reach the Mun and circularize.

Plus, the Oberth effect around Kerbin is a whole lot stronger.

You can leave Mun backwards 180 degrees from where you'd eject from LKO, put your periapsis where you'd eject to your destination planet, and then burn at that periapsis to eject. Costs about 310 from Mun and 160 from Minmus and is like burning 860 or 930 from LKO back up there.

[DrunkenKerbalnaut]

1 hour ago, 5thHorseman said:

You can leave Mun backwards 180 degrees from where you'd eject from LKO, put your periapsis where you'd eject to your destination planet, and then burn at that periapsis to eject. Costs about 310 from Mun and 160 from Minmus and is like burning 860 or 930 from LKO back up there.

I abuse this religiously in my early game.