Cost effective LKO cargo vehicle?

[ShadowNightfall]

Hi all, first post here!

So, I'm in career mode, with the majority of the tech tree unlocked (rapiers etc, but no MK3 spaceplane parts yet...) 

I have a rather large assembly plan for a rather large multi purpose space station. 

SoI need a cost effective (hopefully reusable for realism) LKO capable vehicle with the largest cargo capacity possible. Any ideas? 

Options thus far and their problems: 

1. SSTO - probably with rapiers, but these are hard to design, and cargo capacity seems limited unless I go massive, and I mean massive 

2. Recoverable booster (spacex style) - design wise this should be easier, with optimal cargo capacity, however landing the damn thing is a fair task... I have a mechjeb available (landing guidance) which could work, but surely I would need a mod to fly multiple ships at the same time. I'm willing to try my hand at KOS if it would work? 

Which of my two options is the best way forward, and how best to implement this in ship and mission design and execution? Or is there an option I haven't though of? 

Edited April 6, 2018 by ShadowNightfall

[Foxster]

Umm, SSTO's are low cost (just the fuel) but they are rather payload limited, unless you go huge and that has it's challenges. 

A rocket is probably going to be your best bet. To save cost you could have a cheap disposable solid fuel first stage and a LF/O second stage that you either fly or parachute for recovery.  

What mass of payload are you thinking of?

Edited April 6, 2018 by Foxster

[ShadowNightfall]

6 minutes ago, Foxster said:

Umm, SSTO's are low cost (just the fuel) but they are rather payload limited, unless you go huge and that has it's challenges. 

A rocket is probably going to be your best bet. To save cost you could have a cheap disposable solid fuel first stage and a LF/O second stage that you either fly or parachute for recovery.  

What mass of payload are you thinking of?

So for an overestimate cargo wise, something similar to an orange tank volume and mass wise. For the station construction I won't be transporting anything that heavy but for future refueling missions capacity for an orange tank would be good. 

The solid fuel first stage sounds feasible, never thought of that before. Is there a solid rocket engine big enough to get to orbit? Or would I need a pretty large second stage? Second stage recovery would be harder as it would acheive orbit, so de orbiting and landing would be rather costly Delta v wise.

Just as another though similar to yours, could a space shuttle sort of idea be feasible, for vertical launch?

Thank you for the reply!!

[Foxster]

Well, a shuttle is basically a single-stage-rocket with a disposable solid fuel assist. 

If you don't mind going big then you can do it with a rocket SSTO with a high payload capability that, once built, will only cost you the fuel for each trip...

With an orange tank payload this has loads of dV left by orbit. Most of the landing done with chutes. 

Edited April 6, 2018 by Foxster

[GoSlash27]

ShadowNightFall,

Check out the cheap & cheerful challenge here:

 

Maccallo had an entry that's the perfect design for your needs.

 

It cost him $734 per tonne to orbit 38 tonnes with this design, and that's *without* recovering any of it.

Best,
-Slashy

[ShadowNightfall]

1 hour ago, Foxster said:

Well, a shuttle is basically a single-stage-rocket with a disposable solid fuel assist. 

If you don't mind going big then you can do it with a rocket SSTO with a high payload capability that, once built, will only cost you the fuel for each trip...

With an orange tank payload this has loads of dV left by orbit. Most of the landing done with chutes. 

This looks great! So do you land literally the entire thing? Surely this will be a little awkward for docking? 

[ShadowNightfall]

4 minutes ago, GoSlash27 said:

ShadowNightFall,

Check out the cheap & cheerful challenge here:

 

Maccallo had an entry that's the perfect design for your needs.

 

It cost him $734 per tonne to orbit 38 tonnes with this design, and that's *without* recovering any of it.

Best,
-Slashy

Thank you for the post! This looks great, and should save me a lot of time with landing etc... I will have to do some modifications for rendezvous and docking procedures but this could potentially work!

[bewing]

2 hours ago, ShadowNightfall said:

This looks great! So do you land literally the entire thing? Surely this will be a little awkward for docking? 

Certainly not the entire thing. There's at least one stage there that gets discarded with a fairly expensive Mammoth.

However, that ship's from version 1.4.2, and you are running 1.2.2 currently on your console. So it's not currently feasible for you.

 

[GoSlash27]

4 hours ago, ShadowNightfall said:

Thank you for the post! This looks great, and should save me a lot of time with landing etc... I will have to do some modifications for rendezvous and docking procedures but this could potentially work!

ShadowNightfall,

 No problem, that's actually why we had the competition; to demonstrate and refine techniques to make crazy- cheap lifters without recovery or exploits. Of course... if you wish to add recovery you can do so.
 Your requirement is actually a fairly light payload by our standards (you could do 32t pretty cheap with level 2 facilities). We were able to create even cheaper lifters in the 130- 150t payload range.

Tips:

-SRBs are the best deal going for DV in the first stage. Except for the Flea. That thing is garbage.
-The Twin- Boar is the best bargain in the game for LF&O engines, but is often overlooked.
-Quasi- asparagus staging (SRBs lifting LF&O drop tanks in an asparagus arrangement to feed a core) work beautifully on a larger scale.

Best,
-Slashy

 

Edited April 7, 2018 by GoSlash27

[Foxster]

7 hours ago, bewing said:

Certainly not the entire thing. There's at least one stage there that gets discarded with a fairly expensive Mammoth.

However, that ship's from version 1.4.2, and you are running 1.2.2 currently on your console. So it's not currently feasible for you.

 

Umm, nope, its an SSTO. 

Didn't spot he's on console. 

[ShadowNightfall]

So thus far I'm look at combining several of these designs into a rocket SSTO of some sort. 

Just as a side note, would a space shuttle be remotely feasible for this sort of thing? 

Also, on pc here!

[AeroGav]

You said in your original post that you didn't have mk3 cargo bays unlocked.  Fairings are bugged in 1.4.2 so can't be trusted.

Also, it sounds like you are experienced in building rockets but have little or no expertise with aircraft.

In KSP, it is far easier to access funds than endgame techs,  so taking all these things together you're probably best off just sticking with throwaway vehicles, just concentrate on making them cost effective.  There is no reason you can't recover the upper stage actually ,  but there is no easy way to pull off a SpaceX in stock KSP so use Kickback SRBs for the lower .    They give the most thrust per unit of cost.

Rocket SSTOs have awful payload fractions, even lower than spaceplane ones.  You'd need something monstrous to launch what you need.

Space shuttles are a nightmare to build in KSP.    Harder than SSTOs and they perform worse by just about every metric.  We only build them for the challenge and for "rule of cool".

I can't give much advice on rocketry beyond "use cheap SRB lower and recover the upper".   For airplane type systems, I wrote a long tutorial thread

The main reason people go wrong building space planes is that the game shows mass of parts in the craft editor,  but no drag info.  It offers no clues that leaving open attach nodes is bad, and that parts end attached must be joined by attachment nodes of matching diameters - if not use an adapter.

Aerodynamic (according to KSP) - 2 rapiers and 2 panthers get it to mach 4.7.      5 nervs do the rest. https://kerbalx.com/AeroGav/Andromeda

If you want to try spaceplanes but don't feel ready for SSTO,   instead of trying to build a space shuttle,  I'd recommend making a spaceplane with droppable booster engines.   Whiplash/Panther motors are quite cheap, if you hang them off the wingtips near the CG, jettisoning them will not upset the aircraft.

https://kerbalx.com/AeroGav/Learstar-A2

[Foxster]

Just a thought...

 

[Curveball Anders]

15 hours ago, GoSlash27 said:

-Quasi- asparagus staging (SRBs lifting LF&O drop tanks in an asparagus arrangement to feed a core) work beautifully on a larger scale.
 

Hmm, LFO-core with sideattached SRB with LFO tanks on top feeding the core. Designed so that the extra tanks go empty just before the boosters burn out?

I have to try this ...

[GoSlash27]

2 hours ago, Curveball Anders said:

Hmm, LFO-core with sideattached SRB with LFO tanks on top feeding the core. Designed so that the extra tanks go empty just before the boosters burn out?

You got it.

This one does 140 tonnes to LKO for under $100,000. Not as "gamed" as the contest entries, but almost all of them wound up using this technique.

Best,
-Slashy