Jump to content

STTO (Single Tank To Orbit) Challenge


Recommended Posts

Single Tank To Orbit Challenge:

The Goal:

For purposes that should not be disclosed, Jebediah needs fuel. A lot of it. He pointed to the biggest bloody fuel tank on the market and said "That one. I need it in orbit." But he's on a budget and wants the task completed by the lowest bidder. Get one fully filled S4-512 fuel tank into low kerbin orbit for the lowest amount of funds possible.

The S4-512 has 28160 units of oxidizer and 23040 units of liquid fuel, and weighs 288 tons. If you do not have Making History DLC or simply wish to build in a different configuration you can use other tanks. (3 Kerbodyne S3-14400's, 1 Kerbodyne S3-3600, 1 Kerbodyne ADTP-2-3 and 1 Rockomax X200-16 will bring you to within about 0.3% the amount of fuel and mass.) The cost in funds of these tanks is actually less than a single S4-512. For that reason the cost of the payload whatever it is will be subtracted from the scoring. You can use any configuration of tanks you want actually as long as the required amount of LF/OX arrives in orbit. But in the spirit of the challenge a few large tanks would be ideal.

Category 1:  This is for the cheapest spacecraft to put on the launchpad, or non-reusable launchers. The total vessel cost minus the cost of the payload.

vyznev: 391,432 (first entry)

Category 2: This is for the lowest cost after vessel recovery.  For SSTOs or recoverable boosters. The total cost of the vessel minus the cost of the payload and any recovered parts.

[Leaderboard to go here]

Rules: 

-No ISRU. No mining the launchpad or sending the tanks up empty and filling them at minmus.

-Single launch.

-No modded parts. Stock and DLC only.

-No clang drives.

-No cheat window.

-The cost of the fuel payload is only for the tanks and fuel themselves and is subtracted from the final cost of the rocket or spaceplane. Any attached probe cores, fuel tanks that are used by the ascent stage or other such items that are delivered into orbit or not part of the payload are not subtracted from the cost.

Documentation:

I'll do this mostly on the honor system. One screenshot of the fully assembled craft in the VAB. Any major staging events or milestones in the ascent profile. And a screenshot with the payload in orbit with the resources tab visible. Make sure you know the cost of the fuel payload so you can subtract it from the cost of the launcher. Videos are fine too.

Edited by Kuansenhama
leaderboard
Link to comment
Share on other sites

Well, if you need a lot of thrust for cheap, the answer is surely to use SRBs, right? You just need to use enough of them.

TRHJFP0.png

IKOrcY6.png

More images in imgur album: https://imgur.com/a/u93vgAf

IIRC, a full S4-512 tank costs 51,200 kerbucks, so my score should be 442,632 – 51,200 = 391,432. I probably could've squeezed a little bit more off that by trimming off unnecessary parts (like do I really need that engine plate?), but meh, whatever.

Craft file: https://kerbalx.com/vyznev/Fuel-Lifter

BTW, one issue I noticed while building this craft was that the Clydesdale SRBs kept breaking off from the core on the launchpad. Apparently I'm not the only one who's noticed this issue. FWIW, my solution to the problem was: 1) struts, 2) autostruts, and 3) more struts.

Edited by vyznev
Link to comment
Share on other sites

6 hours ago, vyznev said:

BTW, one issue I noticed while building this craft was that the Clydesdale SRBs kept breaking off from the core on the launchpad. Apparently I'm not the only one who's noticed this issue. FWIW, my solution to the problem was: 1) struts, 2) autostruts, and 3) more struts.

Nope I've had that problem too. A great first sub for this challenge BTW thanks. Saw your imgur album a simple but elegant solution.

Link to comment
Share on other sites

  • 2 weeks later...

I'm gonna put this placeholder submission here, I've since done better than this but I am not quite finished optimizing it yet.

I know that SRB + Twin Boar is a good cost per ton combination. Not sure what the best ratio of solid to liquid fuel is however.

HAUfBR6.png

The cost of the S4-512 is 51200 funds so the cost of the launcher is 292310 funds.

Note the lack of nose cones. Large rockets don't need them as much because of the higher thrust.

OpsmTDg.png

Launch, immediately pitch over

swBs4tv.png

Core throttles down otherwise it'll go too fast in the lower atmosphere

16MYFrD.png

SRB burnout, apoapsis is above 70 km

axU157m.png

SRB separation

3mJ9Rft.png

Circularization

fw242BE.png

In orbit. Note that I actually have more than a full Twin-Boar's worth of fuel left here.

Link to comment
Share on other sites

I had a cheaper one but I gave up on it after a couple of tries when I got periapsis just over 69 650 in the best attept. Just added two solid boosters more and got it up over 80 000m. Cost landed on 333 497. Done with the stock parts you suggested.


 

Link to comment
Share on other sites

Ok, this is probably as optimized as I can get my previous expendable launcher.

OMKcPG5.png

287520 funds with fuel tank, 236320 funds without fuel tank. This is just about the lowest that I thought this design could go.

Six Clydesdales, seven Twin-Boars, the outer six are dropped once suborbital and the central one circularizes.

Spoiler

5kP6Fer.png

On pad

v87meXJ.png

Launch, throttle down to keep acceleration around 20 m/s^2 and immediately pitch over. This craft, while it doesn't look it, is actually quite aerodynamic.

9xjrxAP.png

Twin-Boars are almost entirely off at this point

XOevTnW.png

And now they're completely off

WxIPhBt.png

I take a very shallow gravity turn - the craft is aerodynamic enough that gravity losses are more important than drag losses.

6NRudsD.png

Boosters run out, relight the Twin-Boars

AqKmJjD.png

Suborbital, outer boosters are empty, detach them

NMHX2LJ.png

Created the maneuver, and here I'm actually very surprised. I expected less than 20 m/s remaining on orbit and this has just over 40. However this is the first run that I did a very shallow ascent, so that's probably the reason.

GWQPMG4.png

Burning

PBdm5EB.png

In orbit!

taWqZ6z.png

Warped to the day side, showing propellant and full fuel tank.

Counting the bit of unused propellant as payload, this craft brings 293 tons of payload into orbit for 236320 funds, for 806 funds per ton. 

This is probably beatable by switching engine types, which I will attempt.

 

Edited by camacju
Link to comment
Share on other sites

Xq2rn8k.png

227160 funds with tank, 175960 funds without tank, 611 funds per ton of payload.

First stage is 7 Clydesdale

Second stage is 1 Rhino (4x Poodle is probably even cheaper)

Spoiler

2N69vhJ.png

On pad

HhaDZpM.png

Very aggressive gravity turn

2O4Yy4C.png

Solid motors still going

5tCFpHw.png

Burnout, turn on the Rhino engine

uNX5FXp.png

Coast to apoapsis

ybn8As2.png

Circularizing

XTRnU9X.pngXTRnU9X.png

In testing I managed to bring a few more tons of payload to orbit with a better ascent profile, but this is still pretty good

Edited by camacju
Link to comment
Share on other sites

This thread is quite old. Please consider starting a new thread rather than reviving this one.

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...