Cheapest Big Tank Fuel Lift to 100km Orbit (50k Credits)

[GoodGameHunter]

For the sake of having some fun, and in the great interest of Kerbal science, here's a challenge to anyone willing to undertake such venture:

a) You must upload 6480 liquid fuel + equivalent oxidizer, to a stable 100km orbit around Kerbin. It does not matter in what tank or configuration, just get the fuel up there.

The total cost of a flight must be less than 80.000 kerbucks, including fuel. I managed to get under 50k but I know that's hard to achieve so 80k should be an easier goal for everyone. To clarify, "flight cost" means how much kerbucks are lost for a single orbital delivery (including the delivered fuel itself), so if you're recovering your rocket, you're only paying for the fuel and boosters or whatever else you're using up. In my case, the Hercules craft costs 500k but the vast majority of it is recoverable and the flight and fuel itself only costs roughly below 50k.

c) You are only allowed to use stock parts and no other mods except MechJeb and FlightEngineer (or other mods that do not provide any technical advantage but will help make your development and rocket flight easier). Obviously also no mods that modify part costs

d) It does not matter what means you use to achieve the previous goals. Recoverable rocket, disposable rocket, space plane, whatever you want to do, the goal is all about costs, load the required fuel, and keep the costs as low as possible.

Oh and it must be done in a single flight!

Good luck!

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Here's my entry to the challenge: http://goo.gl/y1x2HY

And a video with a not-so-great commentary

Edited November 18, 2014 by GoodGameHunter

[Laie]

T-80 (it has it's name because it's just a Kerbodyne tank on top of my generic 80t lifter):

(click for gallery)

208 parts, ~15Min to orbit.

369k funds to launch, 357k funds recovered, for ~1.4 Kerbodyne tanks worth of fuel delivered. I previously figured that this amounts to 118 funds per ton, or ~8500 funds for one large Kerbodyne Tank worth of fuel.

With a different ascent path, it can get to orbit in 7 minutes at the expense of (a little) more fuel. I haven't bothered with calculations, but a large tank should still cost less than 9000 funds.

The only mod parts are Mechjeb, kOS and possibly KER. Stock physics.

Vessel is controlled through kOS because I can't be bothered to babysit my milk runs.

Edited November 18, 2014 by Laie

[GoodGameHunter]

Cool, I see you used the new intake, I haven't tried it yet, my craft was build before the last update. Have you tried the long lateral intakes? They seam to have better airflow on paper.

[Laie]

Cool, I see you used the new intake, I haven't tried it yet, my craft was build before the last update. Have you tried the long lateral intakes? They seam to have better airflow on paper.

For me, part count is the limiting factor in this kind of vessel. Performance-wise, the Shock Cones seem to be the equivalent of about two Ram Intakes. You need two parts to mount either (the intake itself, and some fuselage bit to attach it to), possibly less than two parts per intake if you can use multicouplers. Getting the same amount of air from any of the radial intakes will definitely require more than two parts.

[Wanderfound]

Cost after recovery on a large (> orange tank) spaceplane tanker is about √6,000. No way am I flying in stock, but if you do a FAR/DRE category I'll put something up.