The Cheap and Cheerful Rocket Payload Challenge 1.0.5

[GoSlash27]

Meithan,

 As you get into smaller scales, radial decouplers and fuel lines become prohibitively expensive. Serial staging seems to work out better ( see my Poodle entry).

 I can try going smaller, perhaps with a Terrier upper stage.

Best,

-Slashy

[Norcalplanner]

If we did create weight classes, I'm thinking that the payload cutoffs should be less than 10 tons, and then 10 to less than 50 tons. We could label them lightweight and middleweight divisions, and then everything 50 tons or higher would br considered hesvyweight. However, work is ramping up again, so I would need some help in scoring and keeping up the leaderboard. 

Meithan, would you be willing to shoulder the burden of implementing your idea? If so, we can pm to work out the details.

I'd also appreciate hearing from others on the proposed change before we commit to this.

[Nich]

I have been trying to get an SRB, Terrier combo but I cant break 750.  here is an example of one that might make orbit with a better flight path but it still cost 735 funds/ton

 

 

Numbers that seem important are starting TWR of 1.6-1.8 Second stage TWR of .5-.7 and a total vacuum dv of 3250.  I tend to need 3300 min but maccrollo routinely gets craft with 3225 dv into space.  Decouplers are very expensive in this competition.  A pair of cheap ones cost 1200 kredits which means you need to add 1.84t @650/t to justify their inclusion.  On my terrior craft my 2 decouplers cost 800 at @735 that is 1.09t or 16% of the payload

 

I have included a pic of slashys craft analyzed by KER.

[Meithan]

23 minutes ago, Norcalplanner said:

If we did create weight classes, I'm thinking that the payload cutoffs should be less than 10 tons, and then 10 to less than 50 tons. We could label them lightweight and middleweight divisions, and then everything 50 tons or higher would br considered hesvyweight. However, work is ramping up again, so I would need some help in scoring and keeping up the leaderboard. 

Meithan, would you be willing to shoulder the burden of implementing your idea? If so, we can pm to work out the details.

I'd also appreciate hearing from others on the proposed change before we commit to this.

Norcalplanner, work's looking a bit daunting on this side too, but I think I can manage scoring entries and helping you maintain the leaderboard.

I was thinking of 2 or 3 mass tiers myself (maybe an ultra-light 2 tonnes tier?). Let's discuss the details. I'm about to go out right now, so I'll only be able to PM you until tomorrow, if that's ok with you.

[GoSlash27]

38 minutes ago, Nich said:

I have included a pic of slashys craft analyzed by KER.

Nich,

 It's weird seeing one of my craft analyzed using KER

Yeah, the Terrier definitely isn't going to compete with the big boys, but $750 per tonne is a *very* solid entry for it. I don't think I could get one under $900.

I'm fine with weight classes (I suggested the same back on the first page). I'm not really picky about the number of classes, but I'd recommend splitting them up on a logarithmic scale rather than linear.

Best,
-Slashy

Edited February 6, 2016 by GoSlash27

[Nich]

Woot woot finally broke 700 with the mammath.  With 88 dv left and some overshoot who knows what is possible my goal is 675

Total cost 190543

Payload cost 46775

Payload 206.27

696.99 funds/ton

 

[Nefrums]

twin-boar + poodles works

627 funds/ton

 

 

 

[GoSlash27]

Looks like there's a new sheriff in town

[numerobis]

Here's a fun little table: cost per unit of fuel for the various tanks. There's a lot at 1 per unit, but it's interesting that the absolute cheapest is the Jumbo-64 and not the huge kerbodynes (though not by a whole lot).

  0.8984 : Rockomax Jumbo-64 Fuel Tank

  0.9028 : Kerbodyne S3-14400 Tank

  0.9028 : Kerbodyne S3-7200 Tank

  0.9028 : Kerbodyne S3-3600 Tank

  0.9375 : Rockomax X200-32 Fuel Tank

  0.9688 : Rockomax X200-16 Fuel Tank

  1.0000 : Mk3 to 2.5m Adapter

  1.0000 : Mk3 to 2.5m Adapter Slant

  1.0000 : 2.5m to Mk2 Adapter

  1.0000 : C7 Brand Adapter - 2.5m to 1.25m

  1.0000 : C7 Brand Adapter Slanted - 2.5m to 1.25m

  1.0000 : Mk3 to 3.75m Adapter

  1.0000 : FL-T800 Fuel Tank

  1.0000 : Rockomax X200-8 Fuel Tank

  1.0000 : Mk3 Rocket Fuel Fuselage Long

  1.0000 : Mk3 Rocket Fuel Fuselage Short

  1.0000 : Mk3 Rocket Fuel Fuselage

  1.1000 : Mk3 to Mk2 Adapter

  1.2500 : FL-T400 Fuel Tank

  1.3125 : Mk2 to 1.25m Adapter Long

  1.3750 : FL-T200 Fuel Tank

  1.3750 : Mk2 to 1.25m Adapter

  1.5000 : FL-T100 Fuel Tank

  1.7500 : Oscar-B Fuel Tank

  1.8125 : Mk2 Rocket Fuel Fuselage

  1.8750 : Mk2 Rocket Fuel Fuselage Short

  2.1500 : Mk2 Bicoupler

  2.9167 : ROUND-8 Toroidal Fuel Tank

Edited February 6, 2016 by numerobis
added a few more tank types

[Nich]

Wait I thought all the tanks (that are not adaptors or plane tanks) were the same per unit fuel.  When did this change?

[SanderB]

I think the smaller fuel tanks generally are less efficient per fuel unit and it never changed ever as far as I remember. I wonder how efficient a 1.25m cross section launcher can get (ie, a sustainer stage with LFO engines not exceeding 1.25m in diameter). I might be wrong but I believe 830$/t is the best achieved so far under the previous ruleset. I've been looking things over a little and it'll have to be more expensive because of how less efficient the engines and fuel tanks are in several ways.

[Nefrums]

The problem with size 1 is not the fuel tanks or the engines,  the difference in efficiency is negligible.

The problem is the decuplers, fuel lines etc.

I made a quick test with a size one rocket and managed to get 753 funds/ton.  This still has some room for optimization.

 

 

 

 

[maccollo]

3 hours ago, Nefrums said:

The problem with size 1 is not the fuel tanks or the engines,  the difference in efficiency is negligible.

The difference between using 8 FL-T800 tanks and 1 jumbo64 is 650 funds. That's pretty significant. Anyway, I never would have thought of using hard points as decouplers. Suddenly radial staging is cheaper than inline staging. Using the hardpoints I am able to get 645 funds per ton with a skipper and 4 kickbacks.
https://dl.dropboxusercontent.com/u/22015656/KSP%202016-02-06%2017-50-56-54.png

Edited February 6, 2016 by maccollo

[numerobis]

20 minutes ago, maccollo said:

The difference between using 8 FL-T800 tanks and 1 jumbo64 is 650 funds. That's pretty significant.

Indeed. Though I suspect @Nefrums point is that the noodly aspect of the 8 FL-T800 will force you to engage in strutting and decouplers, which will quickly be even more expensive.

8 hours ago, Nich said:

Wait I thought all the tanks (that are not adaptors or plane tanks) were the same per unit fuel.  When did this change?

Most of the tanks are 8 mass fuel per 1 mass tank, but the cost differs. For instance, the 2x FL-T400 and 1x FL-T800 have the same mass and fuel contents, but the latter is 100 funds cheaper.

[Nefrums]

Yes the size 1 fuel tanks are about 10% from the cheapest.

But the Size 1 engines are very good.   in terms of cost/thrust.

LV-T30 "Reliant" Liquid Fuel Engine	5,1
Rockomax "Poodle" Liquid Engine	5,2
LFB KR-1x2 "Twin-Boar" Liquid Fuel Engine	5,6
LV-T45 "Swivel" Liquid Fuel Engine	6,0
LV-909 "Terrier" Liquid Fuel Engine	6,5
Mk-55 "Thud" Liquid Fuel Engine	6,8
O-10 "Puff" MonoPropellant Fuel Engine	7,5
Rockomax "Skipper" Liquid Engine	8,2
Rockomax "Mainsail" Liquid Engine	8,7
S3 KS-25x4 "Mammoth" Liquid Fuel Engine	9,8
48-7S "Spark" Liquid Fuel Engine	11,1
Kerbodyne KR-2L+ "Rhino" Liquid Fuel Engine	12,5
S3 KS-25 "Vector" Liquid Fuel Engine	18,0
T-1 Toroidal "Aerospike" Liquid Fuel Engine	21,4
24-77 "Twitch" Liquid Fuel Engine	25,0
CR-7 R.A.P.I.E.R. Engine[Note 2]	33,3
LV-1 "Ant" Liquid Fuel Engine	55,0
LV-1R "Spider" Liquid Fuel Engine	60,0
LV-N "Nerv" Atomic Rocket Motor[Note 3]	166,7

 (For a fair comparison the cost of Twin-boar was decreased by the cost of a Jumbo tank as that comes included in that engine.)

[GoSlash27]

Nefrums,

 Ahh, but we aren't looking for cost for thrust. We're looking for cost for DV.

 Figuring (as an example) an upper stage with 0.7 t/w initial and 1600 m/sec DV, we have to figure in not only the engine's thrust and cost, but the entire stage as a whole.

 Furthermore, the cheapest upper stage doesn't necessarily mean the cheapest overall launch vehicle. A more expensive but lighter upper stage can make for a cheaper booster, reducing the cost of the entire assembly.

 Looking at it that way, size 1 doesn't stack up as well as it's bigger counterparts. Especially once you figure in the loss of parallel staging and more expensive tanks.

Best,

-Slashy

Edited February 6, 2016 by GoSlash27

[Nefrums]

not arguing with you there.

For an upper stage isp is very important, as well as having enough dV and thrust.   There are no engine competing with the poodle as the most cost efficient upper stage engine in itself.

Drag is another thing to consider,  8 poodles are cheaper and have better isp than a rhino, while having the same thrust, However drag from 8 size 2 stacks are many times grater than a single size 3 stack.

 

[Nich]

Thanks for the info.  Is it just me or are the lifting engines better?  Yes lower ISP means more fuel but more thrust means you can get more payload and fuel (for more potential dv) from one engine.  Not to mention a more efficient launch profile as there TWR will increase more than the more efficient engines.

I think I am going to try a twin boar build.

[GoSlash27]

I compiled a quick and dirty list for comparison.

I assumed 1,600 m/sec DV and 0.7 t/w, then adjusted the payload to have the fuel tanks 100% filled.

Tank costs were estimated assuming the smallest available size in the appropriate diameter, so prices are overestimated a bit.

Type   Payload Mass   Cost  $/t %payload
48-7S  1.03    2.25     500 485 45.8
LV-909 4.31    8.74   1,440 334 49.3
RE-L10 15.0    30.2   3,700 247 49.7
RE-I5  46.6    94.6  13,300 285 49.3
KR-1x2  138    288   36,850 267 47.9
KR-2L   136    266   44,500 327 51.1
KS-25x4 290    588   84,500 291 49.5

This is a good starting point for an upper stage, but overkill for a core stage. As the payload increases, decouplers and fuel lines become cost- effective.

Best,

-Slashy

 

[GoSlash27]

19 minutes ago, Nefrums said:

Drag is another thing to consider,  8 poodles are cheaper and have better isp than a rhino, while having the same thrust, However drag from 8 size 2 stacks are many times grater than a single size 3 stack.

Hmm... Seeing as how drag losses are pretty low in KSP, I wonder if something like that might be worth doing. 7 Poodles in an asparagus arrangement with Kickbacks...

[numerobis]

The poodle is pretty terrible on launch. I think the twin-boar is best for your launch liquid, switching to a flock of poodles later -- isn't that exactly what Nefrums' best spacecraft is?

I am having a heck of a time flying that thing, by the way. I finally got within 100m/s, but it seems a tricky bird to fly.

[Nefrums]

31 minutes ago, GoSlash27 said:

Tank costs were estimated assuming the smallest available size in the appropriate diameter, so prices are overestimated a bit.

Use the largest tanks instead, otherwise this will heavily favor the larges sizes.

The price per fuel difference between the smallest and largest tank is:

Size 1	+50%
Size 2	+11%
Size 3	0

[GoSlash27]

1 hour ago, Nefrums said:

Use the largest tanks instead, otherwise this will heavily favor the larges sizes.

The price per fuel difference between the smallest and largest tank is:

Size 1	+50%
Size 2	+11%
Size 3	0

Right... but my spreadsheet doesn't account for this

It just says "you need this many tanks" and calculates the price appropriately. To use the larger tanks, I would have to teach it how and when to substitute tanks. Either that, or actually build them to get the exact price.

Best,

-Slashy

 

[maccollo]

I had to have one more go with the Rhino booster. Just had to see how far the cost could be pushed down with the radial hardpoints. There was also about 20 m/s of deltaV left in the last attempt. The hardpoints create a bit more space between the boosters and core, so I was able to remove the septratrons. I also decided to stop the pretense and removed the nosecones. Overall this reduced the cost/ton by about 8, with the increase in payload dropping it by another 4 funds/ton.

Total cost: 173455
Payload cost: 44383
Launcher cost: 129072
Payload: 209.051 metric tons
Cost/ton: 617.419

Launch video: https://www.youtube.com/watch?v=onQzPtyTesM

Screen dumps:
https://dl.dropboxusercontent.com/u/22015656/cheapLaunch/payload8.png
https://dl.dropboxusercontent.com/u/22015656/cheapLaunch/launcher8.png

 

Edited February 7, 2016 by maccollo

[numerobis]

26 kickbacks. Ouch. How do you pack them in so densely?

The Rhino is not even 10% of your first-stage thrust. I wonder: would it be worth adding a pair of kickbacks and ditching the fuel and fuel lines on the first stage, making it SRB only?