Is there a "sweet spot" for payload weight when setting up a fuel station in LKO?

[Vllama87]

So I recently borrowed a friend's internet to update my KSP from 1.0 to the current version and get all the mods I plan to use, and I'm noticing that some techniques I used before to get things into LKO are not working anymore.

So my question is this: I have a large (180 ton) interplanetary science vessel parked in a high orbit around Kerbin and, after returning from a low space flyby of Eeloo, it has just enough DeltaV to deorbit itself, and not much else. It runs on nuclear engines and I need 16,000 units of liquid fuel to top it off, but I am having a DEVIL of a time getting that much fuel into orbit.

I guess I was so excited to finally get it into orbit and do some 'splorin that I didn't think about how I would refuel...

Any tips?

EDIT: I suppose I should clarify what exactly the problem is. I'm trying to do this in as few launches as possible to avoid running out of funds. I guess I could do a bunch of rescue missions and whatnot but I just want to fly around in my capital ship lol

Edited December 23, 2017 by Vllama87
clarification

[Rocket In My Pocket]

That's a lot of liquid fuel my friend!

I know you are prolly trying to avoid splitting this up into multiple launches but it may be the easiest way. (2 trips at 8k LF even is a lot more reasonable.) Of course, you could always just brute force it and build a monster rocket.

What kind of tech level are you at? If you could space plane it up there over multiple trips, it wouldn't really cost you anything besides the actual fuel. Or you could set up a mining OP on Minmus or Mun possibly? Regardless of how you look at it, I think this is going to be a time heavy investment, unless you just build a ridiculously huge rocket, which will be a funds heavy investment.

Edited December 23, 2017 by Rocket In My Pocket

[Rocket In My Pocket]

So, to give you an idea...and also because I couldn't stop thinking about how big said monster rocket would have to be to carry that much liquid fuel as payload! Lol.

I whipped up a real quick "monster rocket" that does indeed go to orbit. (Just barely, I'm talking running on fumes at 70k/70k, it also has no provisions to dock with, rendezvous with, or refuel anything on it's own. Wouldn't be too hard to add those functions though, or transfer it via a smaller orbital tug maybe?)

Carries 16k units of extra liquid fuel to orbit, for 200k funds. Could certainly be made cheaper though. Twin boars are pretty expensive for instance. So anyways, it is possible to do in one launch, just gonna be expensive. Maybe consider grinding out some funds first on other contracts?

Edited December 23, 2017 by Rocket In My Pocket

[GoSlash27]

160 tonnes of fuel is quite a lot.

The good news is your payload fraction and cost per tonne to orbit decreases as the rockets get bigger. The Twin- Boar is a very economical core booster when coupled with Kickbacks. That'll get you about 35 tonnes per launch. Spaceplane tankers are an even cheaper alternative, but they require even more R&D time and run the risk of costing far more if you screw up.

 Best,
-Slashy

[Vllama87]

Thanks for the responses! I believe I'm at tech level 5? (500 cost to research) with a few 300's left to grab as well. I have High Altitude flight and Heavy Rocketry, is that enough to build a large SSTO tanker?

I actually just finished the maiden voyage of my first functional SSTO, but it's fairly small (think SR-71 ish) and carries just enough fuel to get back to KSC (or at least crash in the desert less than 50km from ksc :P) after establishing an orbit.

I guess my followup question is: what are the basic guidelines for a large cargo-bearing SSTO? I've done a bit of research on some super-heavy SSTO carriers but they all either require things beyond my tech level (shock cones, rapiers, etc.) or cost somewhere in the 500-1000k funds range x_x

EDIT: A photo of my tech tree.

Edited December 23, 2017 by Vllama87

[Starman4308]

150k-200k funds seems a reasonable estimate for the cost of brute-forcing 16k liquid fuel to orbit. I got a little bit more than that to orbit with a 220k funds rocket (1x Rhino upper, 2x Mammoth lower), though there was plenty of dV left in the upper. I eschewed any sort of aerodynamic surfaces; at this scale, gimbal provides enough control authority if you don't veer far off prograde.

Incidentally, this has been the first craft I've gotten to orbit in stock KSP in months: https://kerbalx.com/Starman4308/SupertankerII

[Rocket In My Pocket]

3 hours ago, Starman4308 said:

150k-200k funds seems a reasonable estimate for the cost of brute-forcing 16k liquid fuel to orbit. I got a little bit more than that to orbit with a 220k funds rocket (1x Rhino upper, 2x Mammoth lower), though there was plenty of dV left in the upper. I eschewed any sort of aerodynamic surfaces; at this scale, gimbal provides enough control authority if you don't veer far off prograde.

Incidentally, this has been the first craft I've gotten to orbit in stock KSP in months: https://kerbalx.com/Starman4308/SupertankerII

Nice, looks like a slimmer version of mine!

Yeah, could prolly do without them, but I'm a stickler for COL being under COM. (Also, I wasn't looking to do a lot of testing on it, as it was sort of a whim. Slapping loads of fins on the bottom is a good way to be sure it'll fly straight on the first try.)

Also, also, nothing grinds my gears like flipping rockets. 

Edited December 24, 2017 by Rocket In My Pocket

[Human Person]

I'd go with a reusable SSTO rocket. Just a big booster with landing legs at the bottom and chutes n' airbrakes at the top. Make sure it has about 4000 m/s of deltav so you can make a reentry burn to prevent engines from blowing up and have some left over fuel to soften touchdown. The Mod Trajectories can help landing near KSC.

[Vllama87]

Awesome guys! Thanks! Once I learned of asparagus staging I kinda stopped using SRBs, apparently that was a mistake! I ended up taking it up in 2 easy installments of 9000 fuel (2k to spare for my SSTO!) with a Twin-Boar +big orange tank, 4 SpaceY heavy lifter SRBs, and an upper-stage scaled-up Swivel.

They were only 79k each, but I got a 40/16k refund on each of them thanks to the reusable idea!

You guys rock!

Edited December 24, 2017 by Vllama87

[GoSlash27]

Vllama97,

 Glad you got it all worked out. Keep in mind though, SRBs are not mutually exclusive with the concept of asparagus staging. You can put tanks and fuel lines on top of SRBs and get the benefits of asparagus staging. We had a contest last year to develop the most economical lifters, and all of the top entries used the "quasi-asparagus" SRB scheme.

For general rule of thumb for large SSTO spaceplanes:

1 airbreathing engine (Panther, whiplash, RAPIER) per 15 tonnes of plane. This can be stretched out to 25t with careful aerodynamics.
Each jet engine will require approx. 400 units of fuel and 1 intercooler. A ram intake is sufficient to feed as many as 4 jets.
Wing area is highly flexible. I like to use one shuttle sized wing per engine.

Expect roughly 25-30% payload fraction.
If not using RAPIERS, count your rockets as payload and adjust accordingly.
Launch t/w should be nlt .35, preferably over .5. Upper stage t/w should be nlt .5, preferably over .7.

Best,
-Slashy

 

[Aegolius13]

You could also consider investing in a big mining ship, especially if you plan to do missions like this repeatedly.  One of the bigger models I've used costs around 250,000 funds to launch, and could get that much fuel back from Minmus in one trip.

Of course, mining is a lot more time consuming than just sending fuel up from LKO.  So you'd have to decide whether you like mining or find it grindy.  Also whether you care that much about saving some funds through the additional time spent.  

[Cheif Operations Director]

You could do a engine refuel in flight system let me explain.

Use asparagus staging and just add a fuel line from your last booster to your core.  

[Vllama87]

Well I've got everything set up, but I've run into a new problem... how do I transfer resources from a tank that isn't visible from the ship exterior? (I uhhh, tend to set my monoprop tanks to 8x radial and clip them in between LFO tanks instead of putting them on the outside of the ship.)

[Cheif Operations Director]

28 minutes ago, Vllama87 said:

Well I've got everything set up, but I've run into a new problem... how do I transfer resources from a tank that isn't visible from the ship exterior? (I uhhh, tend to set my monoprop tanks to 8x radial and clip them in between LFO tanks instead of putting them on the outside of the ship.)

Fuel lines?

[Vllama87]

4 minutes ago, Cheif Operations Director said:

Fuel lines?

The ship is built and already in orbit, the only fuel transfer nodes on it are docking ports. I have KIS and KAS but I didn't put a connector on the ship. Is there another way to get a fuel line onto the ship?

Worst case scenario I'll just edit monoprop into one ship and out of another, I suppose, though I'd like to do it the fun way if possible

Edited December 24, 2017 by Vllama87

[Cheif Operations Director]

No BUT the orange bar in to top right of the orange bar their SHOULD be a Grey Square Press it and find the tank you want to transfer the fuel to and hit the grey square their. Now tap out on the tank losing fuel and tap in on the tank gaining fuel. This will only worked if their docked.

Did it work?

[Vllama87]

Now what? XD

I can't seem to find the "In/Out" buttons

Edited December 24, 2017 by Vllama87

[Cheif Operations Director]

1 minute ago, Vllama87 said:

Now what? XD

Um.... Their SHOULD BE a In and Out button underneath but it obviously isn't their.

I don't know because I play on console. And am Unfamiliar with mods.

see the 7/8 button down it's white with red inside try that it looks like a tank and might be something but other than that I'm at a loss

Ahh!

See how some of the buttons the a darker grey. Make the ones on the other side a darker grey. Maby that can pull up the page 

[Vllama87]

Haha, you know what? I don't know what that button does either! Not fuel unfortunately

Oh well, thanks for your help!

[Cheif Operations Director]

Just now, Vllama87 said:

Haha, you know what? I don't know what that button does either! Not fuel unfortunately

Oh well, thanks for your help!

Wait

Make the pins on the receiving craft darker maby that will help

Did that help

Select the pins

Hello?

[Starman4308]

Have only two fuel tanks selected at once, and in/out buttons should appear. If you want something more sophisticated, there is TAC Fuel Balancer.

[Wanderfound]

10 hours ago, Vllama87 said:

I guess my followup question is: what are the basic guidelines for a large cargo-bearing SSTO?

Large SSTOs are much easier with RAPIERs. It's possible to do them at lower tech, but Whiplash based designs are better suited to medium sized craft.

Given that, the basics:

Streamline, use wing incidence, no more engines or intakes than necessary. Put all of the clutter inside the cargo bay. Angle the wings so that the nose stays on prograde while flying, to minimise fuselage drag.

If you can get into the air before the end of the runway and crack through transonic without trouble, you have enough engine. Any more is a waste of payload mass.

https://kerbalx.com/Wanderfound/Kerbotruck-Compact-Lander

 

That design will easily handle 40 ton payloads. Add another pair of engines and it'll take 60.

Edited December 24, 2017 by Wanderfound

[Rocket In My Pocket]

9 hours ago, Starman4308 said:

Have only two fuel tanks selected at once, and in/out buttons should appear. If you want something more sophisticated, there is TAC Fuel Balancer.

You can have more than two fuel tanks selected at once, they just all have to be of the same type.

Looks like from the SS that his issue was he had monoprop tanks open as well.

[Zhetaan]

@Vllama87:

Clicking the box in the resource tab will show you all the parts that have the selected resource (as you have discovered) but it does not open the transfer dialogue.  For that, you need to Alt+Right-Click the tanks.  To do that, you have to be able to select the tanks, which is an argument against clipping.  However, you can get around that if you position the camera inside the part that you've clipped your monopropellant tanks into (this may require some tricky camera work and zooming; don't be afraid to use the 'Aim Camera Here' button on different parts if you have trouble), because then that part you're in will disappear and you will be able to see your clipped monoproellant tanks.

If you're playing career, you also need some upgraded facilities to be able to do resource transfer, but if your buildings are all level 2 then you should be okay.

[Rocket In My Pocket]

21 minutes ago, Zhetaan said:

@Vllama87:

Clicking the box in the resource tab will show you all the parts that have the selected resource (as you have discovered) but it does not open the transfer dialogue.  For that, you need to Alt+Right-Click the tanks.

Not exactly true, You can just right click the tanks and pin them open. That's all Alt does really, is tell the game you want to open multiple action windows.

Still, you have to be able to actually right-click the part though, the "show all" button isn't going to help you here.

So yeah...don't clip things you'll want to interact with later.