Question on refueling efficiency using Kethane Mod

[SpaceChief]

Hello fellow Kerbals! I've recently begun to add mods to my game to spice it up and I've started using Kethane mod as well as some others. The question I have is this. I've sent some time making a station in orbit around Kerblin for use as a space dock/refueling station and I am wondering if it is more fuel efficient to build a base on Mun to refuel my station or if I should stick to shutting fuel up from the ground? The reason I'm wondering is the amount of effort I spend trying to get fuel off the ground and to the station seems a little much. I launch a huge ship and only get a small amount of fuel into orbit. I think my best so far was 5% or so of my capacity on the station. It seems a little rediculous to try and keep the station fueled from the ground. Any suggestions are greatly appreciated!

[Captain Sierra]

Due to the fact that liquid fuel and oxidizer is denser than kethane, and the Kethane mod obeys conservation of mass, you get less than a 1:1 unitary yield of rocket fuel for your kethane. By that logic, it's more efficient for the operation as a whole to refine at the point of extraction rather than drilling the kethane, transporting it, then refining it. Now, because kethane is slightly lighter than the equivalent volume of rocket fuel, it's more efficient for your tanker craft to ferry raw kethane as opposed to rocket fuel. To sum that up, it all depends on where you want the efficiency. Also, for getting fuel to orbit, I can get an orange rockomax to orbit with 8 FL-T800 fuel tanks and 8 LV 909 engines. It should take less (maybe 6 of those stacks instead of 8) on the Mun,

[Brofessional]

It's better to put your Kethane operation on Minmus instead of the Mun. Lot's of flat places to land, and the lower gravity means you can use an LV-N and get more fuel to orbit each trip. It's also right on the edge of Kerbin's SOI so if you refuel interplanetary ships there they enter solar orbit with nearly full tanks.

I usually land a drilling/refining base at the site, then have a separate vehicle just to carry the refined fuel up and land again. As cool as the idea of fuel stations are, it requires just as much work to refill the fuel station as it does to bring the fuel straight to the spacecraft, so you're better off just not building a fuel station in the first place.

[Captain Sierra]

It's better to put your Kethane operation on Minmus instead of the Mun. Lot's of flat places to land, and the lower gravity means you can use an LV-N and get more fuel to orbit each trip. It's also right on the edge of Kerbin's SOI so if you refuel interplanetary ships there they enter solar orbit with nearly full tanks.

I usually land a drilling/refining base at the site, then have a separate vehicle just to carry the refined fuel up and land again. As cool as the idea of fuel stations are, it requires just as much work to refill the fuel station as it does to bring the fuel straight to the spacecraft, so you're better off just not building a fuel station in the first place.

This is KSP, practicality is not something we pride ourselves on (at least I know I don't!). I built a giant space dock at 1500km purely to say that I docked a 700 part Jool mission to a 600 part space station, FTW!

[SkyRender]

The real question is, how much do you value your time over the return on your investment? As has been pointed out, Minmus makes a better target for getting fuel, but there's a long gap between shipments. The Mun is much more reasonable, but your returns (even if your system is well-designed) will never rise above 50% of what you extract. Kerbin is most time-efficient of all, being instantaneous, yet you end up spending a huge amount of resources to get almost none of the fuel you send up actually in orbit.

If your plans are not on a tight schedule, use Minmus as your base of operations. If you want things to go fairly quickly, the Mun is a better bet. If you just need that fuel right now thank you very much, you'll have to make a rush delivery from Kerbin. Choose wisely.

[Jouni]

I usually land a drilling/refining base at the site, then have a separate vehicle just to carry the refined fuel up and land again. As cool as the idea of fuel stations are, it requires just as much work to refill the fuel station as it does to bring the fuel straight to the spacecraft, so you're better off just not building a fuel station in the first place.

The main function of fuel stations with the Kethane Pack is to ensure that you have spare fuel available when you need it. Otherwise you may have to interrupt your current mission for a surface mission or ten.

Personally I find ground operations tedious, so my kethane infrastructure is centered around a refinery/refueling station orbiting Minmus. A simple lander goes down to Minmus, fills its kethane tanks, and returns to the station. The station has plenty of storage capacity for both raw kethane and refined fuels. Smaller ships can dock directly with the station to refuel, while fuel tankers are used to service ships that are too big to dock safely. Sometimes a tanker also goes down to LKO to carry fuel to the refueling station there, if utility tugs have not been able to salvage enough fuel from lifter stages.

[WafflesToo]

The real question is, how much do you value your time over... <snip>

If your plans are not on a tight schedule, use Minmus as your base of operations. If you want things to go fairly quickly, the Mun is a better bet. If you just need that fuel right now thank you very much, you'll have to make a rush delivery from Kerbin. Choose wisely.

Well said sir

My plans are to haul raw Kethane from Minmus to an orbital refinery around Kerbin. Mostly so I can refine it into whatever products I need most at that moment; LFO, monoprop, or xenon. Possibly even oxygen and water if TAC life support ever includes Kethane support but I digress.

I've seen good use of a Minmus refinery to boost oberth effect by falling from Minmus to LKO and performing the exit burn at perikerb. If your destination is energetically far enough away you do get more boost to your exit burn than it costs to drop from Minmus' orbit.

Little difficult to get the timing right but still a neat stunt.

[Sabreur]

As cool as the idea of fuel stations are, it requires just as much work to refill the fuel station as it does to bring the fuel straight to the spacecraft, so you're better off just not building a fuel station in the first place.

One way to make a fuel station more practical is to put your fuel station in low orbit around Kerbin while your actual mining/refinement operation takes place on Minimus. Run a few trips to Minimus and back to fill up your station with absurd amounts of fuel, then use the station as a waypoint for any big interplanetary missions that need to top off their tanks after reaching orbit. I don't know how resource efficient this would be, but once the fuel station is in place it would be a huge timesaver.

[WafflesToo]

One way to make a fuel station more practical is to put your fuel station in low orbit around Kerbin while your actual mining/refinement operation takes place on Minimus. Run a few trips to Minimus and back to fill up your station with absurd amounts of fuel, then use the station as a waypoint for any big interplanetary missions that need to top off their tanks after reaching orbit. I don't know how resource efficient this would be, but once the fuel station is in place it would be a huge timesaver.

Sorry, but Bro's actually right. Operating the refueling and hauling and refining processes is a time sink. But then again, so is all of Kerbal Space Program so as far as I'm concerned it's one more part of my model railroad to play with.

[SkyRender]

The thing about a good Kethane refining operation is, once you have it in place, the only real concerns are time and Kethane left on the moon you chose. And the latter is only an issue if you make a point of launching gigantic vessels off of Kethane-refined fuel at regular intervals. It's entirely possible (and I've done this many times) to launch a fully self-sufficient Kethane operation for the Mun or Minmus that includes scanner, miner, fuel ferry, and orbital fuel depot in the same asparagus-staged launch from Kerbin. If you're good with timing and know the tricks of the trade, a Minmus base will serve you very well indeed. If you just want to "fire and forget" from low Kerbin orbit and do regular launches, a Mun operation to ferry fuel out to LKO will probably better suit your interests. Either way, you've got the same amount of hardware shipped up to haul up Kethane and convert it to fuel.

[Superfluous J]

My personal Kethane operation on Minmus is a great starting point for interplanetary missions. It takes a LOT of work but it's really satisfying hitting a correct ejection to another planet from a Minmus orbit. Ideally, you'll start (at Minmus) between 6 days and 2 weeks ahead of time (So you want to start 9 days or more from Kerbin) so you can leave Minmus, come in for a low-altitude (80-100km) pass of Kerbin to tweak your orbit so you'll come back at exactly the right time in the window, then at Apoapsis you can burn to set your ejection angle.

Most any ship that can get to Minmus with empty tanks, can get from Minmus to any other destination once you've filled those tanks up. It's a tweak on that "Once you're in Low Earth Orbit you're halfway to anywhere" line that some famous guy said once

[Kosmic Debris]

Personally I find ground operations tedious, so my kethane infrastructure is centered around a refinery/refueling station orbiting Minmus. A simple lander goes down to Minmus, fills its kethane tanks, and returns to the station. The station has plenty of storage capacity for both raw kethane and refined fuels. Smaller ships can dock directly with the station to refuel, while fuel tankers are used to service ships that are too big to dock safely. Sometimes a tanker also goes down to LKO to carry fuel to the refueling station there, if utility tugs have not been able to salvage enough fuel from lifter stages.

This is pretty much my approach; after a lot of design thought I noted two conditions that aren't often discussed. First, the Kethane tanks are empty...so however they get to the surface they need to be landed with regular fuel/oxidizer. Second, a deposit (apparently) does run out, requiring a move of the drilling operation. I haven't done enough to see how long it takes, but that struck me as another reason to have a mobile drilling rig. So my lander is basically a 16K Kethane tank with 4 standard engines, 2 drills, a small Kethane generator for power, a small converter and a scanner. I scan, land, drill (using the generator for power) and refuel using the convertor. Then I have my main conversion plant in low Minmus orbit, and I have nuk-u-lar tugs that move the refined fuel back to my fuel station at 130K around Kerbin.

Given that I have a dead-reliable HLV that launches a full orange tank into LKO, I'm questioning the overall approach to some extent. I can basically launch-and-forget...or I can operate the Kethane operation which is frankly a ton of work. From a "realism" perspective the Kethane in-situ fuel generation operation makes sense, but the effort required to get fuel via that vs. just launching it (admittedly wastefully) from Kerbin makes it somewhat questionable long-term.

Edited February 13, 2014 by Kosmic Debris

[ArmchairGravy]

I agree with Kosmic Debris so much that I uninstalled Kethane and just launch tankers. That being said, Minmus operations net a lot more fuel than Mun operations as you're not burning all of your fuel in landing/orbiting.

[magnemoe]

I prefer to use an pretty large kethane miner 2-4 orange tanks of fuel who I take back to LKO, and use for refueling, then bring it back to Minmus for refueling then empty.

Brings some kethane, this is mostly as I can choose to convert to monoprop or fuel on demand, miner is large enough to refuel multiple ships.

Now you could build an refueling depot in orbit simply launching say 4-6 empty orange tanks and let them arrive empty to orbit, add crew facilities so you can launch experimental ships unmanned and add kerbals and fuel in orbit.

[Jank]

So far I just refuel with a lifter tug, but I could see the value in having a Kethane refinery in another SOI

[KBMODIGITY]

I wonder why this thread has not been shut down like rowsdower did to my last one for even the thought of mentioning of kethane and resources. All I did was add the fact that resources obviously add to the game not in a monetary value but in an exploratory value. You can see it here http://forum.kerbalspaceprogram.com/threads/68992-Why-resources-should-be-put-on-the-front-burner

[TimePeriod]

Assuming you are using the large converter you would get more fuel/oxidizer pr unit of kethane then the smaller one. It's marginal but in the longer run you would get more fuel.

[John Crichton]

I've asked myself the same question a lot lately because I'm preparing a Kethane grand tour ship.

Make sure you do your calculations before lifting off! Figure out where your Kethane bottleneck is...power, conversion or mining. No point adding too many miners if you don't have the power...or the ability to convert quickly enough.

For now I settled for this:

1) Base ship/drive with fuel tanks and docking ports for 2 large Kethane tanks. There's a heavy refinery on the base ship too. Trying to get it just above 12k DeltaV at the moment. All stock except for the Kethane mod and a fancy spinning habitat for 4 Kerbals.

2) 2 refueling landers for convenient (aka low-grav) worlds. Their main use is to refuel the base ship and I will plan my route so this happens on planets/moons where it's "cheap" to ferry up those Kethane tanks. 2 of them because it makes the entire process a lot quicker.

3) Main lander for "difficult" places like Tylo and Laythe. It's single stage and features 5.2k DeltaV. Its purpose is to visit places, not refuel the main ship. Can land on pretty much everything including Kerbin (and get to orbit again on a single stage) but not Eve. Features a single outside seat for Jeb...he gets space-sick in the spinning habitat. 4 extra outside seats allow the other Kerbals to use this as a lifeboat. At 5.2k DeltaV and using the Kethane refueling ability of the ship, they are likely to get home from almost everywhere.

4) The excellent Hondo. I wanted to design my own, but this is pretty much perfect. Can lift off on Kerbin, land on moon, get back...and then do the same thing again all without refueling. The SSTO can be used to land on planets and a small lander can be undocked.

According to my calculations it all comes down to the route you pick. If you pick an inefficient one, you'll need a larger base ship. To get to Tylo and then to another easier refueling moon (since Tylo is too inefficient to refuel the base ship!) will cost you around 10k DeltaV. I'm adding 2k to account for Jeb's piloting errors. Don't tell him!

My base ship features 5 senior docking ports. 1 in front to attach the Tylo lander, and 4 in the back to attach orange fuel tanks and the 2 Kethane tanks. 4 additional junior docking ports allow me to attach the SSTO and 3 Ion Kethane satellites. They don't need to be fast, just efficient. Got enough DeltaV left to attach 1-2 smaller rovers if I wanted to. They'd use the Kethane tank landers to get down to the surface of planets/moons.

Full disclosure: I *******ized someone else's Tylo lander by removing his 2nd stage and turning the ship into a single-stage Kethane lander. All powered with Aerospikes because thrust was the key issue, not DeltaV. Pretty happy with it because I now have a 2k DeltaV safety margin once back in Tylo orbit. So even on Tylo I should be able to refuel my base ship...although it will take forever. I just don't want to be stuck.

Edited February 13, 2014 by John Crichton

[Streetwind]

Given that I have a dead-reliable HLV that launches a full orange tank into LKO, I'm questioning the overall approach to some extent. I can basically launch-and-forget...or I can operate the Kethane operation which is frankly a ton of work. From a "realism" perspective the Kethane in-situ fuel generation operation makes sense, but the effort required to get fuel via that vs. just launching it (admittedly wastefully) from Kerbin makes it somewhat questionable long-term.

I agree with Kosmic Debris so much that I uninstalled Kethane and just launch tankers. That being said, Minmus operations net a lot more fuel than Mun operations as you're not burning all of your fuel in landing/orbiting.

This is true for now, but it might be worth a reconsideration when .24 rolls around. Career mode launches will require funding, and funding will likely be tight unless you actively invest effort (through optional missions) to earn yourself a bonus. At this point it is pure speculation still, but we might be seeing a future in which regularly launching heavy lifters just to refuel orbital depots might not be feasible from a cost/benefit standpoint... at least, not unless you invest effort into paying for it. Then suddenly, the prospect of a "launch once" fuel-processing operation based on kethane could start making a lot of sense.

[KerbMav]

I do not have hard numbers to say which approach would be most fuel efficient all in all. But I have some thoughts to add (repeat?).

Using an all in one miner-converter-transport-lander saves you from the need to land on the spot/close to your drilling site/equipment.

Converting on the ground takes one less orbital rendesvouz (with the converter orbiting the mined body).

Especially useful for mining sites not close the equator!

Converting at a station orbiting the mined body makes ground operations easier by reduing the mass you have to move to a mining site and/or need to relocate as a deposit is depleted.

Having a converter and Kethane at Kerbin enables you to produce the specific type of fuel you need right here and now.

It also makes ground operations easier and saves one orbital rendesvouz. (see above)

Converting directly into a ships tanks reduces the tanks/parts needed at the station itself.

Having a lander with just enough fuel to carry (in one go or multiple trips) either refined or raw Kethane up into orbit, then un-/re-docking its payload to a transfer vehicle unable of landing but fuel-efficient at orbital operations and flying between moon and planet may be an option, too.

Spreading out the tasks of drilling, converting and storage (e.g. ground, moon orbit, LKO) reduces the part count on site.

At any point it is also a question of the required TWR to launch from the mined body again.

I wonder why this thread has not been shut down like

Maybe because this is discussing a mod, not suggesting a change of pace in the development of KSP.

It should be moved to the modding section though.

[John Crichton]

The key reason I use Kethane is because I hate getting stuck and having to rescue crazy Kerbals like Jeb.

I also can't see any way how launching replacement fuel from Kerbin orbit (using disposable tanks) and then shipping them to Jool & Co is any more (cost) efficient than whatever Kethane operation you have running directly on site. All my Kethane refueling ships are fuel neutral, as in, they always have fuel left to share with the "mothership" while keeping the ability to land again (even the Tylo lander). I also don't have to spend time making the Kerbin > other planet transfer.

If you want to be 100% self-sufficient with Kethane, the table below summarises your DeltaV requirments. The table assumes you start off on Kerbin's surface and then move to Minmus as a first base. From Minmus, you can visit the Mun, Moho, Eeloo, Gilly, Duna, Ike and Dres. Use Duna to refuel for Ike of course (or vice versa, doesn't matter). The figures assume you turn around after each visit and start again from Minmus, which is basically a worst case scenario.

After that, head out from Minmus to low Jool orbit and then Pol as your new base. Pol is the "cheapest" refueling moon if you're heading out to Jol and getting there from Minmus will set you back 10.3k DeltaV (assuming a 10% safety margin). From Pol you can then visit Bop, Tylo, Vall and Laythe. No trip will cost more than Tylo to Pol, so that's the max DeltaV you need for the tour.

Would love a single-stage from Kerbin design, but I'm not sure how given I want to actually land everywhere but Eve and Jool (although I might send Jeb to Eve on a crazy outside seat lander). My lander can land and take-off from everywhere but Eve and Jool, but the 10.8k DeltaV needed from Pol to Tylo is a major pain as the lander only has around 5.2k DeltaV on its own.

Trying to get there without drop-tanks or a multi-stage setup. I am trying to push my lander to 7.2k DeltaV on his own. Would net me better refueling capabilities and the ability to tour everything but the Jool system and Laythe just with the lander. Still working on my interplanetary ring shipping the lander to Pol...and of course I'm not sure how to push my lander to 7.2k DeltaV yet. Was able to have a stable version at 5.8k DeltaV, so I'm still 1.4k short.

Would love to do it all with a single-stage giant lander of course, but building an 11k DeltaV lander with nothing but stock parts and the Kethane mod seems to be a real challenge. Not least because I'd need a crapload of tiny landing legs unless I get a mod with stronger landing legs...which I don't want to because I want to keep it as stock as possible other than the Kethane mod

PS: No aerobreaking has been taken into consideration and there's probably a more efficient route. I like to assume a "worst case scenario" though because it'll make the entire trip easier. Figures are all one-way trip figures because it's assumed you refuel completely at your destination.

As to what's more efficient, sending tanks from Kerbin or using Kethane, that's a no brainer in my opinion...Kethane wins. Shipping fuel for 10k'ish DeltaV from Kerbin's surface to a place like Pol can't possibly be more economical than having a simple Kethane refueling lander drop off 3k DeltaV fuel (that's assuming Tylo!!) per refueling trip. It's way more on lower gravity moons/planets, so even more efficient.

You also only have to deal with landing and getting back up...instead of transfer windows from Kerbin to other planets/moons.

PPS: Just to clarify, the Ike figure is the Duna to Ike DeltaV required, not the Minmus to Ike figure. Wouldn't make sense to fly to Duna, back to Minmus and then to Ike for obvious reasons

Edited February 13, 2014 by John Crichton

[Kosmic Debris]

I wonder why this thread has not been shut down like rowsdower did to my last one

Because this one is not discussing resources or game design...simply use of a mod.

[Kosmic Debris]

I could see the value in having a Kethane refinery in another SOI

Yep, completely agree - very different deal.

[WafflesToo]

I too am wondering what the effect of adding money to the game will have. I think SSTO vehicles and persistent, reusable vehicles may become more than just odd curiosities and possibly show real worth.

Doubly so with off Kerbin fuel sources.

[Spatzimaus]

The key reason I use Kethane is because I hate getting stuck and having to rescue crazy Kerbals like Jeb.

The key reason I use Kethane is that I want to be able to actually have FUN in places like Jool, instead of being limited to what you can do with the small amount of fuel a ship can carry there.

A Kethane refinery in Kerbin orbit is basically useless, because it's not hard to get massive amounts of fuel into low orbit from KSC. One around Mun or Minmus has a little utility, but not much since outbound flights are usually better off maximizing the Oberth Effect to leave from low Kerbin orbit. My main use for a Minmus base has been as a depot for INBOUND flights, where a ship coming back from Jool or Duna might not have quite enough fuel left to get back to Kerbin.

But fuel depots around Duna, Eve, and Jool have been essential to my enjoyment of this game. The thing is, as others have pointed out, you're better off refining Kethane into fuel/oxidizer on-site, not hauling the raw material up to orbit. So, I have three basic classes of craft that refine Kethane:

1> A self-contained 300-ton station/refinery/lander. It lands on low-gravity moons (Pol, Gilly, Minmus, or Ike), fills up the fuel tanks using a metric buttload of Kethane, converts as much as possible, takes off, flies to wherever it's needed, then acts like a station until it's low on fuel again. It's a little inefficient to haul drills and a refining module up and down a gravity well, but it saves quite a bit of fuel that you'd otherwise use for rendezvousing your refinery with a station.

2> Rovers with refineries. These drive around the surface until they reach a Kethane field, then drill and refine to fill up. If a vessel lands nearby, they can drive over to it, use KAS connectors to link up, and refuel it while on the surface. If the vessel landed on the Kethane field as well, then the rover can drill and refine while it transfers, so capacity isn't an issue. I've got a small 30-ton rover for general use, and a massive 400-ton rover that also acts as a manned base.

3> Self-fueling Grand Tour vessels. I made a 55-ton one-man vessel with onboard Kethane refinery, which Jeb used to make a Grand Tour, landing on every planet and moon other than Jool itself. Being able to refuel on the surface makes it much easier to take off from places like Tylo, or get to and from Moho without running out of fuel.

If and when we get an economic system that encourages SSTOs and reusable craft, something like Kethane will be essential for even Kerbin-orbit craft. But even there, you'll be limited by the amount of easily accessible Kethane since it's definitely not cost-effective to lift it from Kerbin itself, and sooner or later Mun and Minmus will run out.