Very efficient and cheap rocket

[milankragujevic]

Hello!

I don't think this should be in challenges, but it is a sort of a challenge.

I need a "contractor" to build me a rocket that can lift 15 tons into 69.9 km orbit around Kerbin.

The rocket must be smallest possible and cheapest.

Rules:

- Must lift Francesco's standard payload (or equivalent weighing no less than 15 tons) to 70km circular orbit http://forum.kerbalspaceprogram.com/showthread.php/29006-Very-efficient-and-cheap-rocket?p=358098&viewfull=1#post358098

- All stock parts, Mechjeb or other info mods allowed

- Must be a VAB rocket, not a SPH spaceplane

Metrics:

- Efficiency: Defined as payload mass fraction: 15t / total mass on pad. Higher is better, number will be between 0 and about 0.5 (way under 1).

- Size: defined as number of parts, number between ~50 - 500

- Overpowered: defined as units of liquid fuel + oxidizer left in the lifter after achieving stable orbit. expect values between ~20 - 1000.

Scoring:

You need to come up with some way of normalizing and adding together the above for a final score. For example, if you set "target" values of 100 parts used and 100 units of fuel left over, such that hitting those values exactly has 0 effect on score:

score = 1000*(efficiency) - (size - 100parts) - (overpower - 100units)

(by NeilC)

High Scores (from 1 to 100, first 5 places)

1. Temstar

2. Francesco

3.

4. Daze 57

5.

Edited May 16, 2013 by milankragujevic

[Ninety-Three]

By "Small and cheap", do you mean part count, physical volume, or the literal (and extremely arbitrary) cost numbers for parts?

[milankragujevic]

Well, not cost for parts as it's a place holder, but I need it to look like the most affordable rocket and not to be overpowered.

I believe that you can eyeball the cost of a rocket when you see it. Falcon 1 certainly costs alot less than Falcon 9.

Soyuz and Proton, also.

[joppiesaus]

You should read the guidelines, because there aren't any rules except "No cheaty parts like aerospikes"

EDIT: no problems anymore!

Edited May 16, 2013 by joppiesaus

[Francesco]

this should be a request thread in the spacecraft exchange: how is one supposed to win this?

one thing could be payload fraction: for a 15t payload, an efficient lifter should weight around 80-85t.

[milankragujevic]

Smallest rocket wins the first place, if a better appears it will be changed, first rocket second place until better appear.

0 - Worst rocket ever, doesn't even work

100 - Smallest and the cheapest rocket

50 - Good lifter, not the smallest or the cheapest, or both, but does the job of lifting 15 tons into 69.9km orbit.

[sjwt]

[font=Courier New

D'OH!

Edited May 14, 2013 by sjwt

[Francesco]

uhmmm... is the payload tank going to be full by the time you reach orbit, sjwt?

[Daze]

uhmmm... is the payload tank going to be full by the time you reach orbit, sjwt?

In teory, if there's a pod between two fuel tanks fuel won't pass

[sjwt]

In teory, if there's a pod between two fuel tanks fuel won't pass

D'oh..

Hes right, in theory it shouldn't of, in practice it did.. Back to beginners classes for me!

[Francesco]

I knew it

anyway, I could sort of cheat by putting a command pod and an ASAS module on the payload itself rather than on the lifter part of the rocket, thus making it easier to pilot...

maybe we should have a specific rule about that.

[Boex]

Sorry, how are aerospikes "cheaty parts"? Are you living in >0.17?

Sure it was massively OP before 0.18, but now, due to it's significantly reduced thrust, it's perfectly balanced in my opinion. It wasn't nerfed too hard, and I find myself using it equally or less often than the original engines, and simply adds to your engineering choices.

[Francesco]

here's a payload that weights exactly 15 tons, and has a purpose also:

basically a small fuel depot with probe, electrical system and RCS. we could use that as the standard payload for the challenge.

[Daze]

By the way i made mine... It cost 42850 per launch, but it's the most realistic i could achieve. Hope you enjoy

http://www./?a4a3hi8adcocata

[3_bit]

You should really add a better point system.

[Francesco]

here's my entry: 91.652 tons on the launchpad, payload fraction 16.366%.

I used the payload from my previous post.

the core stage has 2x LV-T30 and 1x LV-T45. the lifter itself, therefore, weights just a little more than 76 tons.

it gets to orbit with only ~40 m/s left:

[milankragujevic]

@Francesco, Yes it's a good payload. I'm going to copy your design. But yes, I need it for sending a two-part lunar lander into orbit, and also a 3man capsule with hypergolic monopropellant fuel.

@3_bit, No I don't. At least I don't think so.

@Daze, 76 score and second place, since I eyeballed it. I'll try it tomorrow and see the result and update the score if necessary. Explanation in first post.

------------

Update: @Francesco This is a much better rocket, and that's what I had in mind. So it's going to be first place, and Daze third. Lowering the score to 50, as his rocket looks horribly inefficient compared to yours.

[Daze]

Yes but if you talk me about efficiency i obviously can make a better rocket lol, you tell us to want a rocket similar to real rocket like the Falcon or Progress, so i made one "in-line".

[milankragujevic]

Yes but if you talk me about efficiency i obviously can make a better rocket lol, you tell us to want a rocket similar to real rocket like the Falcon or Progress, so i made one "in-line".

"The rocket must be smallest possible and cheapest."

I think that's clear enough.

[NeilC]

"The rocket must be smallest possible and cheapest."

I think that's clear enough.

It really, truly isn't though.

What if I make a smaller rocket than the #1 slot, but it's more expensive? Or larger but cheaper? Who wins? How are you defining "large" (mass? part count?)? You're also asking for "efficiency" - by what metric? fuel launched / fuel on pad? payload mass / launch mass?

You even say (emphasis mine):

need it to look like the most affordable rocket and not to be overpowered.

So now we're all trying to guess what you think an affordable rocket looks like?

This is the "challenge" section of the forum, not the "build me something" section. You need some hard numbers and metrics, here. I would enjoy competing in this challenge if the goals, rules, and points were more clearly defined.

Also, you need to try your own challenge before posting it. Doing this challenge yourself will really help you define those metrics.

Edited May 14, 2013 by NeilC

[milankragujevic]

Okay, NeilC.

I need a rocket that has the smallest number of parts and is small, and efficient, not overpowered.

As I said in the first post, I don't believe this is a challenge but it's not a build request but a competition.

Imagine it like this: I want a contractor who can build me a cheap rocket to go to space.

If you're not satisfied with the challenge, I can't help you.

I said I don't know how to build it as I usually build overpowered rockets if they need to lift more than about 5 tonnes, and I need this for a lunar lander.

I'm sorry if this is unfair or something, but I don't know how or what. I just need(ed) a affordable rocket for my cost-effective space program.

[NeilC]

OK, how about this as a suggestion for rules, metrics and scoring:

Rules:

- Must lift Francesco's standard payload (or equivalent weighing no less than 15 tons) to 70km circular orbit

- All stock parts, Mechjeb or other info mods allowed

- Must be a VAB rocket, not a SPH spaceplane (or would you like to allow spaceplanes?)

Metrics:

- Efficiency: Defined as payload mass fraction: 15t / total mass on pad. Higher is better, number will be between 0 and about 0.5 (way under 1).

- Size: defined as number of parts, number between ~50 - 500

- Overpowered: defined as units of liquid fuel + oxidizer left in the lifter after achieving stable orbit. expect values between ~20 - 1000.

Scoring:

You need to come up with some way of normalizing and adding together the above for a final score. For example, if you set "target" values of 100 parts used and 100 units of fuel left over, such that hitting those values exactly has 0 effect on score:

score = 1000*(efficiency) - (size - 100parts) - (overpower - 100units)

This is just a suggestion and probably needs further balancing but it will let you evaluate things using numbers, and pick a winner without issue. That's one reason you should try your challenge on your own first: to get an idea of what a typical score might look like.

[m1xte]

I need a rocket that has the smallest number of parts and is small, and efficient, not overpowered.

I said I don't know how to build it as I usually build overpowered rockets I don't know how or what

I know what you mean.

I thought ok now i build nice, small and efficient rocket and 6h later i have this.

[Temstar]

My craft:

90.455 tons in the launch pad, 15 tons to LKO, payload fraction 16.583%, booster rocket weight 75.455 tons

Built all stock except KER, flown all by hand + ASAS

Rocket on the launch pad

First asparagus booster pair jettison

Second asparagus booster pair jettison

Climbing to orbit against the morning sun

Last asparagus booster pair jettison

70.086km x 70.069km orbit achieved, 33m/s of delta-V left

Payload release

Booster after payload release

If you are interested in slightly more practical (eg self-deorbit capability) rockets that are still highly efficient check out these:

Zenith Rocket Family

Edited May 16, 2013 by Temstar

[sturmstiger]

Here's a rocket to lift 15-ton class payloads to orbit. It's a bit heavy due to the use of a low ISP engine, but like all my designs, is very simple - only 10 parts.

The payload used is a typical 3-Kerbal Crew Vehicle, with 25 parts and weighs 15.65 tons. As with all my crewed rocket launches, a Launch Escape System is included.

Payload put on top the rocket.

The rocket can be launched with MechJeb (not included or required) autopilot, using the following ascent profile.

The only staging event, fuel tank separation, is done safely without Separatrons.

Ejection of Nosecone Integrated Launch Escape System after fuel tank separation. This is just for this payload and not related to the rocket.

In 70km circular orbit, with barely any fuel left.

Crew Vehicle with its full tank of fuel.

Payload mass fraction in this launch would be 15 / 129.8 = ~11.5%, not very high, though in real world a simple rocket would cost less than a much more complex one with a somewhat higher mass fraction - because the cost of rocket fuel is insignificant (1~2%) in space programs. Of course this particular design is not very realistic either - no real launch vehicle today drops empty tanks or uses just a single engine

If you are interested in more "realistic" yet simple designs, check out my Modular Medium / Heavy Lift ELV Family . It uses the same idea as the Angara family, Delta IV / Delta IV Heavy and Falcon 9 / Falcon Heavy, e.g. building several configurations using the same common stages. I use mostly KW Rocketry parts these days as they look awesome, but you can also find pure stock versions (heavy lift variants) on that page. The KW Rocketry version of 15+ ton to LKO configuration, the R102-15, weighs 100 tons, has only 11 parts and uses a "realistic" serial, 2-stage design.