Heavy lifting into orbit to refuel gas station

[AengorKerbow]

I've been playing KSP for a few weeks now.

So i have a space station of sorts that is intended to be a gas station. It has three Kerbodyne S3-14400 tanks. I'm trying to figure out the best way to refuel these tanks, but it is turning out to be fairly difficult.

My latest effort involved using a KS-25x4 Engine Cluster, with three of the Kerbodyne 14400 tanks, two of the LFB KR-1x2s, and about 8 of the S1 SRB-KD25ks. On the LFBs I've reduced the thrust to about 40%, then put half the SRBs at 50% thrust so I could jettison them in stages as they run out of fuel. First the outer ring of SRBs, then the inner, then the two LFBs. I start out with the KS-25x4 cluster at full thrust, then cut back to 50% once I get above 50m/s, then increase to 85% after all the boosters are jettisoned. This strategy left me with about a quarter of a KD14400 tank (maybe a little more if I had a more efficient accent). That would take me about 8-12 trips to fill it up from empty.

I then added 4 KD S3-7200 tanks using asparagus staging so I could drop them off in pairs as they ran out of fuel. This got me up to 70% of a tank remaining. I guess that is ok. But I was wondering if there were any strategies that can improve this poor efficiency.

[Franklin]

Photo(s) of the rocket, please.

edit: But keep in mind [gas] stations are always an accumulation of many launches. It's not often (ever?) you send up three 14400s and then send up 1-2 following launches to cap them off. If rockets were that efficient you wouldn't need the gas station to begin with.

The issue also may be that you're trying to lift a lot of fuel. Your station went up empty, so Assuming you can increase the efficiency of your lifter by 50% (which is impressive) you're still looking at at least 6 following launches to fill up the station (my math is probably wrong). It's a lot of fuel.

Edited November 3, 2014 by Franklin

[mhoram]

It depends on what you mean by efficiency.

If you want to get the fuel into orbit with as low costs as possible, then SRBs are a good way to do that.

You can find in this thread reference points how good your lifter is:

http://forum.kerbalspaceprogram.com/threads/87211-0-24-s-Cost-Effective-Lifters-Challenge

If you aim to improve the payload fraction (Payload mass divided total rocket mass) 15% and more can be considered good. For top payload fractions (around 20%) have a look in this thread:

http://forum.kerbalspaceprogram.com/threads/55615-0-22-0-23-0-Payload-Fraction-Challenge

If you want to reduce the number of trips, then build bigger rockets.

• Super-massive payloads
  
• Show Off Your Largest Rockets!
  
• What's the highest mass you've ever put into Kerbin orbit with a single ship?
  

[Zylark]

Getting fuel to orbit from Kerbin is both expensive and not entirely efficient. What I do, is to not do any refueling launches at all. Once a Station or Depot is in orbit, it'll get more fuel by siphoning off what is left over from some other launch. Then I get some useful payload to orbit, and add to the fuel reserves even if it is just a few hundred units of LFO at a time.

The other strategy I use is to set up fuel production on Mun by means of Karbonite or Kethane mods. Transporting fuel from Mun to a Kerbin Station or Depot is a pretty simple affair - and more important cost nothing.

If you must transport fuel to orbit, then anything over a Jumbo64 tank will weigh so much that the entire operation becomes very inefficient and very costly. If you play sandbox, then that is fine - if in career there are better things to use those funds on.

[Pecan]

The only thing refuelling at your station should be vehicles that never land on Kerbin. Since that means they'll almost always operate in space they should be using LV-Ns. That in turn means they won't need huge amounts of fuel and could probably be launched full in the first place. My guess - you'll never use that much fuel even once you get it there.

As Zylark said, anything more than an orange tube just isn't worth it - except for the fun ^^.

[AengorKerbow]

I will upload a picture of my refuel rocket when I get home this evening. It isn't very pretty, as it grew less by planning and more by "well, that wasn't enough, lets add some more boosters."

I am playing in career mode. But I am using a recovery mod that allows me to recover of staging components, as long as I have enough parachutes to prevent damage. That reduces some of my costs.

I've heard of the Kethane mod, but I haven't used it. That is an interesting possibility.

[AengorKerbow]

The only thing refuelling at your station should be vehicles that never land on Kerbin. Since that means they'll almost always operate in space they should be using LV-Ns. That in turn means they won't need huge amounts of fuel and could probably be launched full in the first place. My guess - you'll never use that much fuel even once you get it there.

As Zylark said, anything more than an orange tube just isn't worth it - except for the fun ^^.

How I envisioned it's use, is for missions to Duna or Eve, where I will need to carry enough fuel for taking off from the surface, so I'll need a larger rocket, with more fuel, than I've used for my Mun and Minmus missions. Though I have no experience with any missions past Minmus, so I don't really know what to expect in that regard.

[capi3101]

I've been playing KSP for a few weeks now.

So i have a space station of sorts that is intended to be a gas station. It has three Kerbodyne S3-14400 tanks. I'm trying to figure out the best way to refuel these tanks, but it is turning out to be fairly difficult.

My latest effort involved using a KS-25x4 Engine Cluster, with three of the Kerbodyne 14400 tanks, two of the LFB KR-1x2s, and about 8 of the S1 SRB-KD25ks. On the LFBs I've reduced the thrust to about 40%, then put half the SRBs at 50% thrust so I could jettison them in stages as they run out of fuel. First the outer ring of SRBs, then the inner, then the two LFBs. I start out with the KS-25x4 cluster at full thrust, then cut back to 50% once I get above 50m/s, then increase to 85% after all the boosters are jettisoned. This strategy left me with about a quarter of a KD14400 tank (maybe a little more if I had a more efficient accent). That would take me about 8-12 trips to fill it up from empty.

I then added 4 KD S3-7200 tanks using asparagus staging so I could drop them off in pairs as they ran out of fuel. This got me up to 70% of a tank remaining. I guess that is ok. But I was wondering if there were any strategies that can improve this poor efficiency.

Well...you could always deliver the fuel by spaceplane. Back in 0.23 I farted around with the idea of building a massive transfer stage based on a cluster of 25 LV-Ns that would lift itself into orbit (using SRBs to help get it off the ground). It'd then need to be refueled before it could be used. Dumb idea, of course, but I'd decided then to go ahead and use spaceplanes to refuel it. The idea was that the spaceplane parts could be fully recovered (sans the fuel). Back then it was role-playing; in 0.25, that's actually a pretty damned start strategy if I say so my own self.

So I had a plane capable of doing the job - sorta: the Auk VII.

This is a good example of how NOT to build a spaceplane, incidentally. Lousy lift, lousy thrust, imbalanced all to hell - I could never deliver the full load and land safely at KSC. But you get the concept.

If you want to try this route, I suggest taking a look in two places - keptin's Basic Aircraft Design - Explained Simply, With Pictures for the basics and DocMoriarty's KSP Space Plane Construction and Operation for specifics (the only thing I'll add there is that the new Wing Connectors are functionally equivalent to Delta Wings, something to bear in mind.

I should try again with the Auk; now that I know more, I might be able to build a completely functional plane this time around...

EDIT: I'm pretty sure that's not the Auk VII in the picture...trying to remember which one that was. The VII was unmanned.

[Zylark]

I've heard of the Kethane mod, but I haven't used it. That is an interesting possibility.

Sure is. The following example is using Karbonite mod, but Kethane works much the same way. Karbonite however integrates very well with the Modular Kolonization System mod that I also use. Same author and all...

Anyhow. Assuming you got your Mun (or Minmus by all means) mining operation up and going - some assembly required - all you need is one really big fuel lander.

That'll do. Launched upside down and that big tank on the lander emptied of fuel to get the weight down to something managable.

Plot a course for Mun. Don't trust MechJeb doing this properly. With a bit of experience, you'll do this much better yourself, and always getting a good prograde orbit at your desired altitude.

Landing is something MechJeb does a whole lot better than me however. But here MJ missed the target by nearly 30-40 meters, so had to do some plumbing to hook up the lander and the base. All done, fuel transfer is a breeze. Next up is just deciding where you want that fuel.

The short of it being getting well over 6000 units of fuel more or less for free. Setting up the base do cost a bit, and that lander isn't free either. That is a one-time investment, and well worth it as you'll be able to fuel up for free for the rest of your career.

Oh, and there is also an easier way - no lander required:

With MKS you get the Kolony Logistics module. With it you can transport whatever to wherever within the same Sphere of Influence. It cost a chunk of fuel depending on from where to where you need transport what and how much. The upside is, it is entirely automatic and runs in the background. A typical transfer of fuel from the Mun to Mun orbit will cost amount of fuel to transport divided by roughly 4 and will take a day to complete.

All you need then is a ship with a large fuel tank to ferry the stuff from Mun orbit to your station in Kerbin orbit.

Edited November 4, 2014 by Zylark

[Wanderfound]

As has been mentioned upthread:

1) You don't need that much fuel in orbit unless you're planning on setting up an Eve tourism service. A few orange tanks that get refilled after every ~5 uses is plenty.

2) The cheapest way by far to deliver fuel to orbit is by spaceplane or other recoverable SSTO.

For example: http://forum.kerbalspaceprogram.com/threads/90337-Economic-Fuel-to-Oribit?p=1361984&viewfull=1#post1361984

Wet cost: √149322

Recovered: √143321.7

LF delivered: 3727.9

O delivered: 4186.4

Cost: √6000.3

Splitting the bill evenly between the LF and O portions:

Price per unit of LF: √0.8

Price per unit of O: √0.7

Edited November 4, 2014 by Wanderfound

[Wanderfound]

As has been mentioned upthread:

1) You don't need that much fuel in orbit unless you're planning on setting up an Eve tourism service. A few orange tanks that get refilled after every ~5 uses is plenty.

2) The cheapest way by far to deliver fuel to orbit is by spaceplane or other recoverable SSTO.

For example: http://forum.kerbalspaceprogram.com/threads/90337-Economic-Fuel-to-Oribit?p=1361984&viewfull=1#post1361984

Wet cost: √149322

Recovered: √143321.7

LF delivered: 3727.9

O delivered: 4186.4

Cost: √6000.3

Splitting the bill evenly between the LF and O portions:

Price per unit of LF: √0.8

Price per unit of O: √0.7

Edited November 4, 2014 by Wanderfound

[AengorKerbow]

Here is my refueller ship. I think I'd have issues if I used that aerodynamics mod I've heard about.

Edited November 4, 2014 by AengorKerbow

[bitslizer]

Not my designs, but I've been using these as inspirations for my own SSTO Cargo lifter.

http://forum.kerbalspaceprogram.com/threads/92447-Firefly-Launch-System-(FLS)-New-Crafts!-The-FLS-KLAW-series!

land them back at KSP for 100% fund recovery (less fuel cost)

trick to launching is to gain 2000m/s + between 25km and 30km before kicking in the booster to LKO, when the AP is to your desired LKO, feather the jets to minize atomsphereic drag all the way up to 70km

[Alshain]

This is my refueler, it's not entirely finished yet.

[Wanderfound]

This is my refueler, it's not entirely finished yet.

http://cloud-4.steampowered.com/ugc/36353839590188695/34FDBF88124688AEB421C3700302C8F471684D45/1024x576.resizedimage

That'd be fun to land IVA; not a lot of forward visibility when you're pitched up. I don't think a Concorde-esque droop snoot is gonna cut it...

[Pecan]

That'd be fun to land IVA; not a lot of forward visibility when you're pitched up. I don't think a Concorde-esque droop snoot is gonna cut it...

RPM includes HullCam (or something like it). Add NavUtils (and VV) for all the instrumentation loveliness you could want :-)

[Wanderfound]

RPM includes HullCam (or something like it). Add NavUtils (and VV) for all the instrumentation loveliness you could want :-)

And pray that your cameras don't burn off on the way down...

http://forum.kerbalspaceprogram.com/threads/97802-Fun-with-IVA-reentry-%28lotsa-images%29

[Pecan]

Lol, I never knew that was a thing.

[Alshain]

That'd be fun to land IVA; not a lot of forward visibility when you're pitched up. I don't think a Concorde-esque droop snoot is gonna cut it...

Have you done IVA in that cockpit? You can't see a thing no matter where it's located. I tried it with that plane and I still couldn't even see the nose at all.

[Wanderfound]

Have you done IVA in that cockpit? You can't see a thing no matter where it's located. I tried it with that plane and I still couldn't even see the nose at all.

See the link in #17...

That was done with the normal rather than inline cockpit, but the IVA is the same.

[doggie015]

Have you considered hauling up the big tank as part of the initial launch? A fair few versions ago (Back when orange tanks were a new thing) I designed a craft which uses the core stage of the launcher as the fuel tank on orbit. I'm not even sure if it works anymore but it's up at http://jmp.sh/IJt75o4 if you want to take it for a spin - the engine detaches (Last time I checked anyway!) and you can dock the bit at the top on launch to the main tank once in orbit if you so desire (It has its own RCS system to facilitate that). Then just send up some fuel with your craft of choice to top up the tank. If you remove the central engine detachment system you should be able to use the launcher to get 100 tons into LKO (Unless you are using Real Solar System - this thing will not work with that