How useful do you find fueling stations?

[Valley]

I have a fueling station (unmanned) around both Kerbin and the Mun. I placed them there for the Kerbin-Mun run for my ships but find, to my amusement, that after developing refueling rockets to refill them that I don't need them. The same rockets can easily refuel ships in orbit around Kerbin and the Mun.

I assume, as I try to spread out farther, that they will become more useful but have noticed that most players, when dealing in interplanetary travel make massive ships which carry their own fuel or send a fleet of smaller specially designed ships (one of which is a tanker).

In other words, how often do you place a station in orbit around a planet for the sole purpose of storing fuel for future missions? Outside of manned stations, that look cool, how many of you have stations whose sole reason is to be a orbiting 'pumping station'?

Edited August 10, 2013 by Valley

[Johnno]

I have a few refuelling stations that are just there for fuel storage. I have one in Kerbin orbit for when I play around with SSTOs and one in Mün orbit for playing around with reusable Mün landers. Mainly though I build stations for the fun of it, the cool looks and in case of emergencies.

[annallia]

I use a combination of refueling stations and refueling satellites (akin to your rockets). The satellites are used for smaller craft and then deorbited. The station however is used for larger craft. Some of my larger builds (usually the orbital builds) tend to have... lets say massive fuel requirements. I would rather dock at my station which has roughly 8-12 of the big orange tanks worth of fuel stored at any given time and fill the ship in one go than I would dock say 4-5 refueling satellites to fill the ship.

That is dependent on preference though as eventually those refueling satellites will have to dock with the station to refill its massive tanks anyway.

[Tiron]

I have a fueling station (unmanned) around both Kerbin and the Mun. I placed them there for the Kerbin-Mun run for my ships but find, to my amusement, that after developing refueling rockets to refill them that I don't need them. The same rockets can easily refuel ships in orbit around Kerbin and the Mun.

I assume, as I try to spread out farther, that they will become more useful but have noticed that most players, when dealing in interplanetary travel make massive ships which carry their own fuel or send a fleet of smaller specially designed ships (one of which is a tanker).

In other words, how often do you place a station in orbit around a planet for the sole purpose of storing fuel for future missions? Outside of manned stations, that look cool, how many of you have stations whose sole reason is to be a orbiting 'pumping station'?

I never managed to get my refueling tankers to work, got Kethane instead so I could get the fuel from the Mun, but never actually followed through on it because my stations were too laggy. I had a vague sort of idea for a simpler (and smaller) design that hopefully wouldn't lag so much, but haven't actually done anything with it.

Actually, I haven't done much at all since then because I'd been playing with Spaceplanes and rovers instead. Except the rovers don't work very well because of the terrain bugs.

I suspect the general principle works better with Kethane (or its eventual stock replacement), because you can get fuel from low gravity worlds instead. Especially if you're hauling the raw kethane to a refinery station. Which in the past has traditionally been somewhat less efficient than refining it on the surface and hauling the fuel, though the recent changes have...modified that dynamic more than a little. The kethane-> fuel conversion factor is the difference in weight between the two, modified by the efficiency. If the efficiency is lower than 100%, the fuel weighs less than the kethane. If it's more than 100%, the kethane weighs less than the fuel. The maximum conversion efficiency used to be 99%. It's now 103% for Liquidfuel, so it's a bit more complicated.

Regardless, the key point is the tyranny of the rocket equation. To move more mass you need more fuel, which adds more mass, so you need more fuel, which adds more mass... Apparently the only reason it's not an infinite loop is that you burn the fuel as you go, continuously losing weight.

So to maximize efficiency you need to move the lighter craft to the heavier one. This is probably going to be the craft that needs to be refueled. And if you're doing that, your tanker is effectively a temporary refueling station.

This also means, for example, that the most efficient way to launch a tank into orbit is to use the fuel in the tank to launch it, then refill it in orbit (Ideally with fuel from a nearby body with low gravity, as that drastically reduces the cost in fuel to move the fuel you're filling the tank with).

Edited August 9, 2013 by Tiron

[HeadHunter67]

I built one, but I'm so bad at unassisted rendezvous that I have yet to actually use it.

[Geschosskopf]

The usefulness of refueling stations depends on what you need the fuel for. There's not much need of refueling for ships staying within the Kerbin system. Either they're small enough to get where they're going unassisted, or they're a docked collection of such things. And in any case, if you do need to refuel something in the Kerbin system, it's pretty simple just to send a small tanker up from Kerbin to bring fuel to the stranded ship.

Where fueling stations come in handy is at other planets. There, you can't just send the odd tanker on the spur of the moment due to having to wait for launch windows, but the expedition always seems to need more fuel than you planned on to start with, due to unforeseen issue, the desire to visit more of the planet than originally intended, and the need to come home eventually. So, it's always a good idea to include some source of extra fuel in the expeditionary flotilla. There are several ways to do this, ranging from a number of self-propelled fuel tanks that can go where needed within the system, to an immobile orbital fuel depot, to several varieties of Kethane-based things. I personally prefer a combination of all 3, meaning Kethane operation maintaining a small depot, which in turn supplies several self-propelled fuel tanks. That way, I'm not dependent on sending fuel out from Kerbin beyond what the expedition uses to reach the target and get set up. In any case, all you have to bring home are the Kerbals so all of the above is now in place for use by later expeditions.

As a side note, if you want to do the Kethane thing, the best place to obtain the stuff is on the smallest moon of the system, so you burn less fuel lifting it to where you need it. And I think the best place for a depot is orbiting the main planet because its primary purpose is to make sure you have enough fuel to get home, and that's where you'll be leaving from. Whether you refine the Kethane into fuel on the moon or at the depot is up to you, and it really depends on what you're making.

[Keome]

I find them useful when I need to top off the tanks. I can make lighter designs, or designs that can go a lot further by filling up the tanks at one of my stations.

Fuel is brought to the station by other rockets that have excess fuel (i.e. lifter stages with a bit of fuel left in them). Why drop stages with fuel in them when I can use that fuel to keep the stations filled and then use that fuel to refill other rockets?

[Ziff]

It depends on what you are doing. I decided to build a large Kethane mining facility on the Mun. I took a minimalist craft approach and tried to keep my crafts as small and efficient as possible, without creating excessive debris. In order to do that I would also need an orbital station around the Mun for transfers and fuel storage. I started with 1 refueling station around Kerbin. Then I built several small 'orbital transfer vehicles' that I used to ferry station modules from Kerbin orbit to Mun orbit. Then I did the same to create the base on the Mun. During this entire process I actually saved on boatloads of parts by simply reusing and refueling nearly all my vehicles.

[Edit] To fully answer your question, I plan to do the same thing with Duna. It's certainly effective if you have small vehicles that need to refuel as opposed to just a large craft that carries its on fuel. Is it necessary? Absolutely not, however, I also find it far more entertaining to build and dock with these types of orbital stations.

Edited August 9, 2013 by Ziff

[Diche Bach]

Haven't done any of this stuff yet, but I want to. Still fiddling with getting a RemoteTech basic starter network started up.

Could someone post: (a) a brief description of what an orbital fuel depot consists of; ( the procedure to get it setup; © the procedure to stock it up with fuel; (d) how it is then used to refuel stuff.

I of course have some ideas on that stuff, but it would be edifying to hear how some of you guys who know more about it do it.

ADDIT: and one more clarification: the parts that use Kethane fuel are not compatible with the parts that use stock "liquid fuel + oxidizer"?

[Crush]

Fuel depots near Kerbin rarely make sense IMO. When you have a fuel depot, you need to send tankers to refuel it. Just sending the tankers to the ship you want to refuel is exactly the same amount of work.

But it can make sense to park a fuel depot at another celestial body when you intend to use it multiple times during the same mission.

You can, for example, park a fuel depot in orbit around Jool, and then explore the moons with a much smaller and thus more fuel-efficient craft which you refuel at that depot whenever it runs dry.

[Anton P. Nym]

I find my LKO fuel depot convenient. Yes, it has to be supplied with tankers but I can launch the tankers whenever I like or whenever I want to keep in practice with rendezvous operations. Yes, I could fly tankers directly to missions underway (and do on occasion) but the fuel depot is always there and if I find I need fuel unexpectedly I can count on it (and an orbital tender I'm about to launch) to resupply. (The tender will even allow rescue & recovery operations.)

And atop all that, it's providing me valuable experience in running a depot for the time when I do want to send one to Jool.

-- Steve

[Icarium]

Before reading this, my current project was to build a refueling station in LKO, but now I think I'll skip that and go for a Mun station instead. Thanks!

[annallia]

Haven't done any of this stuff yet, but I want to. Still fiddling with getting a RemoteTech basic starter network started up.

Could someone post: (a) a brief description of what an orbital fuel depot consists of; ( the procedure to get it setup; © the procedure to stock it up with fuel; (d) how it is then used to refuel stuff.

I of course have some ideas on that stuff, but it would be edifying to hear how some of you guys who know more about it do it.

ADDIT: and one more clarification: the parts that use Kethane fuel are not compatible with the parts that use stock "liquid fuel + oxidizer"?

Depends on definition of depot, station, and satellite.

Some might define a station/depot as anything really that is manned, others might scale it on size, others still would consider it a station if it is intended to be reused rather than a one off.

For me a station is large, a fueling station/depot generally to me has several large tanks for storage or with a craft I am looking to make one off refuelers. (they dock, next time a ship comes in to be refueled they dump 85% or so of their fuel and then deorbit themselves).

Because of this the station/depot is really little more than whatever you want a station to be, just with the addition of fuel tanks to be filled by a tanker. Build your station, allow at least one docking port (I usually build an arm with multiple ports for tanks) dock the tanks to that port/arm and then send in your tanker to fill them as needed.

Satellites are a slightly different story, they are usually just a fuel tank with docking ports put into orbit for a one time use, then you crash them into whatever body they are orbiting.

I cant answer your kethane clarification because I am not entirely sure on that, I haven't really gotten past scanning planets yet (did attempt to mine some but crashed my lander).

[Rainbow-Dashie]

I'm still pretty new to this game, and thus have not yet mastered the "putting large self-sufficient super ships into space" skills yet (i made one but it blew up in orbit) So i use smaller, simpler ships which work much better then any of the large ones i can build. I have a pretty decent ship im using, "The Wonderbolt", a nice 30-somethin part, 3 stage rocket. It can get into orbit easily, reach the mun and back, get into orbit around the Sun, and is pretty dang close to reaching Duna (might be able to if someone more experienced flew it).

So to get that last little push to Duna, im building a refueling station, so i can top off The Wonderbolt's tank, and make it to Duna (probably a one way trip, but hey! first trip there!).

So for me, and my smaller, less impressive ships, having a refueling station in Kerbin's Orbit increases my rockets range a bit more, plus docking is just awesome.

[SpeedDaemon]

Orbital refueling can be useful for interplanetary missions, because you can use the fuel in the interplanetary stage during launch, which should drastically reduce the size/complexity of your launchers to get it off of Kerbin.

As others have pointed out, you can always just launch a few refueling ships to top it off instead of a station, but the dynamic changes a bit if you're mining fuel on the Mun or Minmus. Then, instead of heaving heavy fuel through heavy gravity and atmosphere, you only have to nudge it into Kerbin's gravity well and aerobrake into orbit, then send the much lighter empty vehicle back out. Also, your refueling vehicles are completely reusable in this case. Since everything is "free" right now, it's not a big deal, but might become so once we have to pay for parts!

[Geschosskopf]

Before reading this, my current project was to build a refueling station in LKO, but now I think I'll skip that and go for a Mun station instead. Thanks!

Um, I dunno about that. Fuel depots aren't really cost-effective within the Kerbin system because the tankers required to fill them up could just as easily meet the thirsty ships themselves anywhere from LKO to Minmus. So only build a fuel station in the Kerbin system (including Mun or Minmus) for style points; they really serve no practical purpose there. NOTE, however, that this is only true for the Kerbin/Mun/Minmus system. Other plantets are a different story.

But regardless of that, Mun isn't the best location within the Kerbin system. You want the fuel depot at the place where you have the highest fuel consumption, so ships can top up before doing expensive burns without using much fuel to get from the depot to the maneuver node. Therefore, if you really want a fuel depot in the Kerbin system, having it in LKO is the best place.

[Valley]

Since everything is "free" right now, it's not a big deal, but might become so once we have to pay for parts!

Good point. I don't make very good reusable shuttles or space planes (crash, death, Senate hearings) but I do plan for any ships that travel between Kerbin and the moons to be reused. Standardizing docking ports is a MUST for proper refueling!

(Also don't forget your station should also have a small tank of mono for those ships that use RCS)

[Burninate]

Cost is one big unimplemented part of the idea... but not the only one.

In real life, fuel depots are attractive because we only have ~20T payload launchers, maximum. The development of a new 100T launcher would be incredibly expensive relative to using 5x 20T craft; Rocket prices per pound tend to be extremely responsive to a low launch cadence. A Saturn V that is launched only sparingly, every four months or so, and requires a whole new class of larger tooling and launchpad and facilities devoted to the design, is much less economical than a larger number of smaller rockets, launched more often.

In KSP *beta sandbox mode*, launchpad part counts are a major limitation on increasing payload. The maximum practical payloads range from about 100T to 1000T, depending on your computer & settings, and anything larger will require in-space assembly of the few remaining parts that aren't jettisoned to escape the Kerbal gravity well. Things assembled in space which don't have to deal with 1G static load and 3G dynamic acceleration, because they're using underpowered engines on huge tanks, also don't have to worry so much about bracing parts. Complex missions can be assembled and launched with *large payloads* that have sufficient delta V to go on interplanetary return missions - missions that would not be possible in a single launch.

I find the Kethane mod cool, but somewhat regrettable in implementing simple in situ resource utilization, because it doesn't require you to have these grand large in-orbit construction efforts to complete a mission.

Edited August 9, 2013 by Burninate

[Captain Sierra]

I use a refueling station as a staging area for tugs that carry my tanker modules out across the system. It also serves as a refueling station for me to send SSTOs to the Mun.

[Geschosskopf]

I find the Kethane mod cool, but somewhat regrettable in implementing simple in situ resource utilization, because it doesn't require you to have these grand large in-orbit construction efforts to complete a mission.

Well, Kethane is optional . And don't forget that KSP has a toy-sized solar system so even the biggest KSP interplanetary ships, painstakingly assembled in orbit from scads of smaller subassemblies, have ridiculously low delta-V requirements compared to doing the same thing in real life. So I don't see Kethane being "regrettable", because even without it KSP interplanetary flight is still extremely easy, relatively speaking.

[Vanamonde]

I play around with the idea of refueling stations sometimes, but the problem is that the part count of the station + the part count of the ship rapidly becomes unmanageable. When I'm actually going places instead of putzing around in orbit, it just makes more sense to fly multiple fueling tankers to the ships.

[Burninate]

Well, Kethane is optional . And don't forget that KSP has a toy-sized solar system so even the biggest KSP interplanetary ships, painstakingly assembled in orbit from scads of smaller subassemblies, have ridiculously low delta-V requirements compared to doing the same thing in real life. So I don't see Kethane being "regrettable", because even without it KSP interplanetary flight is still extremely easy, relatively speaking.

I don't have a problem with it, it's just interesting to think what one might find the mod-heavy community building without it.

You're right, though - KSP has a tiny solar system; It could be expanded outwards to include targets that are more challenging dV-wise, without jeopardizing the experience of the existing system.

[RocketPilot573]

They're definitely useful for refueling ships that remain in orbit to be reused, except when Kethane breaks...

[Captain Sierra]

To answer the earlier compatibility question about kethane, the converters produce stock resources. They are as compatible with stock as you can get. If you are refering to the kethane engine, it runs on normal jet fuel but can burn in non-oxygenated atmospheres.

I use kethane to create an orbital fueling network. My one in the Kerbin system is really pointless (I can always bring fuel right from KSC) but I refuse to bring up tankers so I challenge myself. Call it practice, because I will be using it to create a fully self sufficient system out of Jool.

[Geschosskopf]

If you are refering to the kethane engine, it runs on normal jet fuel but can burn in non-oxygenated atmospheres..

I have to disagree with this. In my experience playing with it, per the Kethane docs, and from looking at the CFG files, this engine only runs on raw Kethane for fuel and "KintakeAir" for oxidizer (the only source of which is the integral intake on the engine). Normal LF (aka "jet fuel") won't do anything for it.

Also note that the KE-J65 is a very special-purpose engine. It only works reasonably well in a combination entailing low speed and high throttle, meaning a very heavy airplane. Forget using it for an SSTO. And because it can't SSTO, and because it lacks a rear attachment node, you always need at least 2 engines. So if you have a light airplane, you have to REALLY throttle back because each engine is so powerful, but that means it tends to cut out even more frequently.