How would I get a 40 ton payload into orbit?

[Vectura]

I already have rcs on it so I can dock with my station, and a Skipper engine to perform the rendezvous. What rocket should I use to get it into orbit though? I have not yet unlocked the really big rocket motors, but I have pretty much everything the size below (mainsail size). I have tried asparagus staging but it still runs out of fuel really fast, even if I try to limit by velocity so I don't waste fuel in the thick atmosphere.

Edited August 19, 2014 by Vectura

[cantab]

My approach is simple. Design a rocket that can lift as much as possible in a single stack, ie without any boosters. Save it as a subassembly from the uppermost fuel tank. Then stick as many of them together as you need for a payload. No fuel lines needed.

[Pecan]

If you can't make a rocket big enough to launch your payload cut your payload in half and dock them separately to your station ^^.

[Temeter]

Mechjeb and Kerbal Engineed can show you the available Delta-V and T/W-ratio. Otherwise use more rockets.

[Red Iron Crown]

Moar boosters is the traditional response to your question.

More usefully, around 200t of asparagused boosters should get 40t up there.

[Endersmens]

If you have mainsails, Try this asparagus design. starting at the bottom:

One stack in the center, of 2.5m tanks, one orange and one half size. Surround it with 6 orange tanks with mainsails on the bottom of all tanks. Strut it up and organize the fuel lines. (i also recommend seperatrons, less explosions ) above the central stack, put a skipper with a half 2.5m tank and some RCS. You might also need to add some radial engines to this stage. For your rendesvous stage that you say you already have, i would put the smallest 2.5 tanks and the skipper. LOADS OF STRUTS. Just a suggestion, if its too confusing than dis-regard this entirely. Hope this helps!

[Vectura]

-snip-

I have just tried something along those lines, and... it worked! Only I used the LFB KR-1x2 boosters instead which have an extra 500 more thrust than a mainsail. Thanks for the tip though (moar, moar, more asparagus!)

[capi3101]

40 tonnes isn't all that much to lift; Temstar's Zenith V is capable of lifting that payload easily. Alternatively, you can follow his guide to good asparagus to build one of your own. The Zeniths are a few versions old now but they're still good boosters. I'm still hoping Temstar will at some point put together something that surpasses the Supernova as far as maximum payload capacity...

You can even launch 40 tonnes into orbit with a single stage booster, though you'll have to be judicious about how you build it and DEFINITELY about how you fly it (pretty much just throttle back after you've made your gravity turn to the green zone of the gee meter, keeping the AP between 30-60 seconds until you're well up into the atmosphere and a minimal throttle burst for orbital insertion). Pre-0.24, I would've said eight mainsails and nine stacks of three jumbo-tanks each, with fuel lines running from the center stack to the eight outboard stacks. I have yet to fully analyze the 0.24 parts owing to the different wet/dry fuel tank mass ratio. No doubt far larger payloads could be put up with those engines.

[Frank_G]

A good way to start designing a launcher is to keep in mind, that the launchers mass will be about 5 - 10 times heavier than the payload. Unless you have the SLS parts think more in direction of 10 times. That will give you an efficient launcher. Mainsails are your friends for sure.

I try to keep my launchers visually as close to a rocket as possible, so consider a transfer stage on top of a main center stage and 2 or 4 side mounted boosters. That should do the trick. Personally i dont like asparagus setups mentioned by Red Iron Crown, but they are really efficient. So find your style, then built it.

[Endersmens]

I have just tried something along those lines, and... it worked! Only I used the LFB KR-1x2 boosters instead which have an extra 500 more thrust than a mainsail. Thanks for the tip though (moar, moar, more asparagus!)

Wait, are you saying you conveniently tried something similar to what i said, or that you followed my advice and it worked?

[Pecan]

...Pre-0.24, I would've said eight mainsails and nine stacks of three jumbo-tanks each, with fuel lines running from the center stack to the eight outboard stacks. I have yet to fully analyze the 0.24 parts owing to the different wet/dry fuel tank mass ratio. No doubt far larger payloads could be put up with those engines.

I was playing around while you were typing ... 4 mainsails.

All 2.5m parts. Core stack; RGU with large SAS and docking port on top (to connect the <=45t payload). Two orange tubes beneath. Radially attach 4 stacks of two orange tubes each (8 orange tubes plus the two in the middle). Add mainsails to bottom of the 4 radial stacks, Rocomax brand adapters and drogue parachutes on top of them. TWR ~1.47 and 4,790m/s deltaV. Will SSTO, de-orbit and land at <5m/s touchdown speed.

The point of this design is that engines are expensive - by using a SSTO you recover 98% of the entire vehicle cost (minus fuel) if you can land back at KSC.

ETA: Oops, I forgot to say - you need fuel lines from the two central orange tubes to the radial stacks, of course.

Edited August 18, 2014 by Pecan

[Vectura]

Wait, are you saying you conveniently tried something similar to what i said, or that you followed my advice and it worked?

I mean I followed your advice and it worked.

[SRV Ron]

Simple asparagus design with skippers but a pair of Mainsail on the last set places a full orange fuel can in orbit with fuel to spare.

The core stage is recoverable.

[TheScienceGuy120]

wanna know my method for building rockets?

step one:ask yourself what you are going for(for example, you are trying to get a 40 ton payload into orbit)

step two:make an un-necessarily large launch stage

step three:make an un-necessarily large booster stage

step four:place your payload on top, add rcs, go crazy with struts, add boosters, and you are done.

as simple as the steps listed above.

[Ringkeeper]

if you dont mind to use other peoples work: Munshine Lifter Family

Lifters with subassembly for 5 to 165 tons . I always use this.

[O-Doc]

I've got some low tech lifters called Pro-Chute. They're 20, 30, 40, 50 and 70 ton subassembly lifters.