What do your Orbital Fuel Dumps look like?

[Hotel26]

Happy New Year, everyone.

I am overhauling my fleet and I'm in the market for ideas about orbital fuel dumps (OFD).  Let's define an OFD as an orbital vehicle (Kerbin or elsewhere) that serves the sole two purposes of:

1.  refueling visiting vessels;
2. (possibly) keeping mission components docked together awaiting final (low orbit) assembly;
3. (not looking beautiful [in Space, nobody can see how Ugly you are])

I gave up on space stations as anything more than a fuel dump long ago.  I've recently upgraded to 1.2 and then 1.3 and find auto-strutting -- which is just a way to defeat the ugly side of the Unity physics engine (as best I can gather) -- does actually help.  But I still can't risk docking very much to the OFD (pictured).  And have to remain very observant with the Warp key lest tragedy befall.

What have people found is the best way to put a pile of fuel into orbit and keep it stocked??

Pictured below, (BEWARE THE UGLINESS), I assemble the following from bits left over from two super-tanker launches.  Each super-tanker lofts 165 kilotons of LF up to the OFD.  You can see this OFD has two weak links, at the hubs.  I find that just maneuvering a ship near it can cause it to get the shakes.  Even auto-strutted.  And I'm not terribly sure which kind of strutting (Root, Parent, Grandparent, Heaviest) ought to work best...

Please post screenshots of your Orange Fuel Dumps...!!

 

Edited January 2, 2018 by Hotel26

[Hotel26]

So the reason this is an issue for me right now is that I am starting a new world and finding that it's hard to duplicate the same performance (in stability) as the above.  It may be because the original was an upgrade from 1.2 and then I added all the auto-strutting.  Trying to assemble one from scratch in 1.3 is not panning out, even as I progressively add the auto-strutting as I add every pylon.  (a.k.a. a pair of "ugly orange tanks")  They almost immediately begin shaking.

Edited January 1, 2018 by Hotel26

[KerikBalm]

Too much autostrutting, or at least autostrutting the wrong things together causes the craft to shake apart, be judicious in its use. Also, lower part count helps, so why use 2 orange tanks when you can use 1 large kerbodyne tank?

Also, why do you need a fuel dump that big?

[Hotel26]

Woooaah, there's the answer.  (I am way out of date!!)  I need to rebuild my super-tanker around these Kerbodyne thingies...

To answer why the fuel dump is big: lots of fuel means less trips.  The tanker delivers 33,000 units (payload).  I could just use the tanker as the fuel dump but second reason for "why so big" is ten+ connection points.

I think I need a better balance of fuel supply to tanker size to docking points, keeping it all reasonable.

(I'll attach a photo shortly of my Minotaur super-tanker.)

Edited January 2, 2018 by Hotel26

[Whackjob]

I used to send mine up in one piece like this.

[Hotel26]

59 minutes ago, Whackjob said:

I used to send mine up in one piece like this.

Waaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaah, man.  That doesn't even fit onto my screen... 

OK, well, in my defense, at least I have spaghetti staging. 

EDIT: "FOUL!!"  I want to know what you've got off screen!! 

OK, here we go: https://kerbalx.com/Hotel26/Minotaur-Super-Tanker  This is stale technology now.  Let's rebuild it.

 

Edited January 1, 2018 by Hotel26

[MR L A]

5 hours ago, Hotel26 said:

To answer why the fuel dump is big: lots of fuel means less trips

I'm not sure it does mean less trips to be honest. Its the same amount of tips or more, just spaced out differently. It's often just much more efficient to launch refuelling craft directly to whatever needs refuelling - rather than launch them to a fuel depot which then needs to be rendezvoused with by whatever wants refuelling (at greater docking expense due to the mass of the depot OR the mass of the interplanetary craft). Just cut out the middle man. 

[Geonovast]

I prefer to put an ISRU station in Minmus orbit.

But if you're going to put a fuel dump in LKO, two things I would consider:

1. Use the 3m tanks.  Stronger connections and a lower part count.

2. Don't space it out like that.  Yeah it looks all science-fictiony, but it's also gonna be more wobbly.

[pandaman]

One concept I'm considering trying...

When sending survey probes to orbit wherever to scan for ore and anomalies etc give them the largest fuel tank and a docking port. That way they can double up as fuel stations.  Even if i don't fill the tank fully when launching the capacity is there to use them as filling stations.

[Rocket In My Pocket]

Here's a pretty modest fuel station from earlier in my current career. (Omg, I forgot how ugly the stock skybox is...)

I find a couple of small fuel depot's to be nice to have sometimes in a pinch, but I don't tend to ever build huge stations holding tons and tons of fuel. Still, I like seeing screenshots of huge fuel stations!

Edited January 2, 2018 by Rocket In My Pocket

[swjr-swis]

A fuel station I made back in 1.1.2.

The fuel storage core is 14x Kerbodyne S3-14400 tanks in a star configuration, topped by habitation modules (14x30=420 max kerbal capacity). Total fuel capacity, including the pods = 156k units of LF, 149k Ox.

The hab modules could all be decoupled in the event of an emergency, capable of independently performing deorbit, reentry and powered landing back on Kerbin. The staging shown in the editor was later changed, as decoupling all pods simultaneously was a guaranteed explosive event that damaged several pods beyond recovery. Keeping a single pod out of the mass abort event (and decoupling it by itself a second later) was enough to avert explosions. Somehow it seemed appropriate to let the captain's pod eject last, so I considered it an acceptable solution.

Spoiler

I also uploaded some screenshots of my attempts at getting this thing into orbit fully fueled and in one piece. Proper 4am Kerbal engineering which I termed the 'Cathedral Method'. Lesson learned: skipping sleep to finish building a complex craft can have... well, less than optimal results.

Part count of the final version -with a lab ring, ore tanks, tug, and the lifter- was around 1600 (860 without the lifter), with abysmal performance, so I never shared it. But the station itself was very stable in orbit, I never saw any undue oscillations or random explosions, and I had 4 of them in LKO at one point, although one was sacrificed in a test of the mass evac procedure and pod recovery.

 

My OFDs in later careers were a lot smaller and more sensibly shaped, but always based on the largest Kerbodyne S3 tanks - it helps keeping the part count down.

[Hotel26]

On 2018/01/01 at 10:47 PM, MR L A said:

I'm not sure it does mean less trips to be honest. Its the same amount of tips or more, just spaced out differently. It's often just much more efficient to launch refuelling craft directly to whatever needs refuelling - rather than launch them to a fuel depot which then needs to be rendezvoused with by whatever wants refuelling (at greater docking expense due to the mass of the depot OR the mass of the interplanetary craft). Just cut out the middle man. 

Well, you could be right if you launch to rendez-vous with the tanker already in orbit.  That just makes the tanker itself the orbital fuel dump.  Multiple ships could refuel from the one tanker.  Until it is (nearly) depleted.

But not right if you launch a tanker to each vessel that needs fuel.  How much fuel do you need anyway for a mission anyway?  Probably not as much as 165t.

The more fuel (as payload) you put into orbit on a launch, the less launches you will require to service your interplanetary fuel needs.

So, in the case of my VUD (Very Ugly Design), I happen to have 5x orange tank pairs on the tanker that can easily be made into the fuel dump.  This kind of fixes the "nearly depleted" tanker scenario, because a new tanker comes up "just in time" to offload as much of its fuel into the dump as it can.  For a while, it stays attached because it's too capacious to offload all its fuel.  But when it does, it backs out to retrograde with just enough fuel onboard to de-orbit.  Then the next tanker is scheduled to come up.

If the Kraken just plain forbid the concept, then I'd say you are completely right.  But I think I need to play with the bigger tanks, redesign my tanker around them and possibly just limit myself to a single hub with just 5 docks.

Edited January 2, 2018 by Hotel26

[Hotel26]

15 minutes ago, swjr-swis said:

I also uploaded some screenshots of my attempts at getting this thing into orbit fully fueled and in one piece.

Thank you for doing that!  (I am no longer an ATHEIST.  Hallelujah!!)

Uhm.  I wonder how fast that thing jumps into space without any fuel in the fuel star?????

Big lesson for me (thank you) in the fight against the Kraken is "do good welds".    I'm gonna run a fast experiment to boost an empty cross (4xKerbodyne) or star (6x) an see if I can get it into orbit on my standard Aquila launcher...

[Whisky Tango Foxtrot]

Here's my Dres Fuel Depot (with a lander attached to the end):

Its main purpose is to allow interplanetary ships to easily refuel. Since the vast majority of my interplanetary missions use nuclear engines it prioritizes liquid fuel over oxidizer, with most of its bulk being made up of a Mk3 Liquid Fuel Fuselage. It's supplied by a mining/ISRU base on the surface. I have a similar station oribiting Moho, but it was an earlier design with some flaws that I've ironed out in this version, and I have an identical station en route to Eeloo.

[sh1pman]

I don't use fuel depots. Don't see the need for them. My fuel tankers are already big enough and have docking ports. They're also fully recoverable and reusable, so it costs nothing for me to get the fuel where I want it.

Edited January 2, 2018 by sh1pman

[ussoldier2002]

I'm sorry but this made me laugh so hard lol. I love the "sole purpose off two" items then you listed three things. I'm not being a grammar pedant or nothing but I laughed out loud. Plus I'm pretty drunk ha ha ha!! I wish I could actually contribute to this conversation though lol.

[Hotel26]

OK, quick experiment.  Pictured has capacity for 47,500 units of LF as opposed to the 57,600 of my 20 "orange tank" construction.  [It looks a good deal better, too.  It'd certainly be easy to add some habitat for crew transfer...]

[I didn't exactly get the center aligned when I slapped this together.  ]

Edited January 2, 2018 by Hotel26

[Hotel26]

31 minutes ago, sh1pman said:

so it costs nothing for me to get the fuel where I want it.

Thanks for the photos!!

For interest, how much fuel does your tanker bring to space?

"costs nothing".  I wish to very respectfully point out the value of your own time and the other Mission Control Specialists who assist you on each and every launch from KSC, sir!

Of course, we "play" for fun but I would say that a fuel launch from KSC is probably your most frequent kind of launch and you may already have done thousands of them(?).  Everyone a very routine mission, by now...

[Wcmille]

Here's my orbital Mun station and mothership construction yard. A number of different ships are currently docked. The orange tanks are pushed through the Mk III Liquid Fuel tank to make multi-directional docking port senior ports. At the bottom of the station is the power grid, cooling, ore tanks, and ISRU. The ore tanks actually do most of the refueling, since you don't have to do anything for them to refuel.

I don't launch fuel from Kerbin anymore. To get fuel to my Kerbin station, I send the tanker in the lower right. It's the ship with 6 large holding tanks stacked in a column. That way, I don't have to manage whether I need mono, oxidizer, or liquid fuel. It just makes the right thing.

I don't actually have a lot of oxidizer stored. I try to use nukes often, which just need liquid fuel.

Edited January 2, 2018 by Wcmille
Incomplete answer.

[Hotel26]

@swjr-swis

Cristo Redentor:

[NSEP]

I use my spent stages, detach the engines from them and make a OFD out of them. Usually my spent stages have a little bit more fuel left.

[eddiew]

Not orange, but functions as a fuel dump...

Most of my returning flights don't go to ground anyway, so they hook up with the station and transfer any remaining fuel before heading for a parking orbit on the last fumes. Any tourist/crew SSTOs that go up hand over whatever they can spare before de-orbiting.

On the whole, if you have a policy of docking with your fuel depot before landing, then you'll never waste fuel by bringing it back to ground at the end of a mission  

Edit: for m'sanity, the rings are welded parts and only count as one tank each. That'd be a lot of clicking if each tiny tank was its own entity  

Edited January 2, 2018 by eddiew

[sh1pman]

8 hours ago, Hotel26 said:

Thanks for the photos!!

For interest, how much fuel does your tanker bring to space?

"costs nothing".  I wish to very respectfully point out the value of your own time and the other Mission Control Specialists who assist you on each and every launch from KSC, sir!

Of course, we "play" for fun but I would say that a fuel launch from KSC is probably your most frequent kind of launch and you may already have done thousands of them(?).  Everyone a very routine mission, by now...

60t of fuel/oxidizer to low orbit not counting the landing fuel. That's if I go for the first stage landing (and I always do). 

I launched a lot of them for refueling purposes, and I usually have a tanker in orbit of every explored planet or moon to refuel passing ships. Once empty, it lands and refills at a surface gas station  fuel refinery. Tanker has parachutes, but its engines are powerful enough to land without them. It's also aerodynamic and can glide to KSC.

[Hotel26]

1 minute ago, sh1pman said:

60t of fuel/oxidizer to low orbit

Well, sir, I think that is outstanding.  (Especially, as it is a beautiful-looking ship.)  At least, in my neighborhood, that makes it an OFD. 

So I have to ask you how much fuel do you load onto an interplanetary mission, maximum?  Do you send 60t to refuel a mission in LKO?  If you don't use it all, do you bring it back?  If you need less, do you go up with less (+ margin)?

Please forgive all the questions!!

[sh1pman]

18 minutes ago, Hotel26 said:

Well, sir, I think that is outstanding.  (Especially, as it is a beautiful-looking ship.)  At least, in my neighborhood, that makes it an OFD. 

So I have to ask you how much fuel do you load onto an interplanetary mission, maximum?  Do you send 60t to refuel a mission in LKO?  If you don't use it all, do you bring it back?  If you need less, do you go up with less (+ margin)?

Please forgive all the questions!!

This is the latest version of my tanker. The engines are from Nertea's Near Future Launch Vehicles (balanced with stock), and the legs are from Kerbal Reusability Expansion.

On an interplanetary mission I don't use tankers, I use ships that have one less fuel tank and a long Mk3 cargo bay with everything that I need. Once it is in orbit, I send a full tanker to refuel it. That tanker stays in orbit until it's drained, then it comes down.

Craft files: https://kerbalx.com/sh1pman/craft

Edited January 2, 2018 by sh1pman