Large Payload

[Yawdar]

So ive been playing KSP for a while, off an on since about 1 year ago. Im perfectly capable of getting to other planets with small probes and, landing on the Mun and Minmus, no issues. But now with contracts and whatnot (which i love having objectives) i have to build some sort of Mun Station. In the end, meeting all specifications, this thing weighs about 20 tons. (i made some changes to it w/o looking at weight, should be around 20T) I only use Kerbal Engineer and i have all the research up to the 500 mark. If anyone could help me out getting this thing to have the DeltaV to get to the Mun, i would love you forever.

Craft File: Kerbo-National Mun Station

PS: This thing doesnt have to return, though it has parachutes, so at a later time i could bring it back IF it has the DeltaV to get home.

Some people say running the forums for answers is cheating... I call it 3rd party consulting

[Alshain]

Your best bet is to build a tug, ideally with nuclear engines for high fuel efficiency. When your done, leave the tug in orbit in case you need it again.

Take a large fuel tank (2.5m) and attach 2-4 smaller tanks (1.25m) radially. Attach the LV-N to the bottom of those small tanks and put appropriate sized docking ports on both sides of the big tank so it can push and pull. Don't forget the fuel lines.

Ideally you want to pull but if your station blocks the engine flame, you won't get any thrust. You can also angle the engines outward a bit to help this problem.

I went looking for a picture of one of my tugs but oddly enough I couldn't find a single one. However that thing on the right in this pic is a Karbonite fuel collector. A tug would look very similar, except the middle would just be a fuel tank and you wouldn't need landing gear and such.

Edited January 29, 2015 by Alshain

[Wabbit]

Actually, a 20t lifter is pretty easy. To the Mun, slightly harder but very doable.

[capi3101]

Okay...so you're wanting to move 20 tonnes to the Mun. I'm assuming the 20 tonnes is going to include whatever delta-V you need to land it. So you just need a transfer stage capable of getting to the Mun and a booster capable of getting that into Kerbin orbit.

So...whip out the delta-V map......you need 1170 m/s of delta-V to go from a 70k LKO to a 10k LMO. If you want a one-way trip craft, you can put that together with a Rockomax Decoupler, a single nuclear engine and an X200-8 fuel tank; that will give you 1,238.5 m/s of delta-V, plenty enough for a one-way trip. If you want to be able to deorbit the thing afterwards, you could add an OKTO-2 probe core and 2 Z-100 battery packs; that would add only 0.05 tonnes and cost you 2.5 m/s of delta-V. Total mass will be 27.45 tonnes.

Now, getting 27.45 tonnes to LKO. A classic asparagus design will do the trick. Using Temstar's guidelines, you should expect a total rocket mass of 183 tonnes with a total of 2869-3049 kN of thrust at launch, with 631-670 kN in the core and 372-396 kN in the boosters, assuming a 4-stage to orbit asparagus design (i.e. 3 booster pairs and a core). I'd tackle that with a set of seven Skippers; leave the core Skipper set to maximum thrust and set the thrust limiters on the external booster stages to about 59-60% or so. Total engine mass of seven Skippers is 21 tonnes, you've got 27.45 tonnes of payload, say two tonnes of asparagus support equipment (a stack decoupler, an array of six radial decouplers, a sepratron per booster, maybe a probe core and some batts to deorbit the core)...from your 183 tonne rocket, you're left with 132.55 tonnes for fuel tanks; divvy those up evenly and it comes out to 18.9 tonnes of fuel per asparagus stack. An X200-32 tank weighs 18 tonnes, so just go with thems. You can add an FT-200 to the boosters if you really need the extra fuel.

I'll have to play around with the design when I get a chance (to see if it can land and make it back to Kerbin on its own). The info I gave you should be enough to get you started, though.

What level is your launch pad at? 183 tonnes is an estimate; you can get into orbit with a lighter rocket if your asparagus is good. I'd just hate to see you try to put the design together and not be able to launch it due to the Level 2 mass limitation...three tonnes short......

Edited January 29, 2015 by capi3101