[0.22-0.23.0] Payload Fraction Challenge

[mhoram]

OP, please explain "No excessive usage of torque in the payload", I do not understand this.

What is "Torque", and where do they actually helping in the fraction value?

Torque is a measure how fast a ship can accelerate a rotation around its center of mass by using electricity.

Torque is an ability of SAS modules and of Pods.

The other way of rotating a rocket around its COM is using the gimbaling of engines.

Engines are balanced in a way that non-gimbaling engines are more efficient than gimbaling engines.

So using lots of torque-parts in the payload while not using any gimbaling-engines allows the ship to rotate even if there is no means of rotation in the propellant.

So this restriction is meant to prevent excessive use of more efficient non-gimbaling engines without providing means for rotation in the propellant.

How many torque value is consider excessive?

This is a difficult question.

I can tell you what I consider to be definitely not-excessive:

- 1 manned pod in the payload

- 1 unmanned pod in the payload

- 1 SAS-module per 50 ton payload

Otherwise ... it depends on the ships design.

Edited October 30, 2013 by mhoram
precisised physics explanation

[Sirine]

@mhoram Thanks for the detail answer.

1 sas-module = 20 torque value.

Manned pod are in difference value from 5~15.

Remote control devices are from 0.3~1.5

I believe 15 torque (3 crew pod) value per under 10 tons payload categories are acceptable.

35 torque per 100 tons payload categories, and 55 torque per >100 tons payload categories.

Please consider?

[tavert]

Here's the first thing I threw together, design's not totally optimized but took plenty of tweaking to get the ascent trajectory right. 18.65 ton payload, 95.62 tons on the pad, 9 stages, 19.50%.

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[mhoram]

18.65 ton payload, 95.62 tons on the pad, 9 stages, 19.50%.

So the magic 19%-barrier has been broken. Congrats!

Anyone aiming for 20?

[numerobis]

I'm at 19.4% and I just can't seem to do any better, for the <10t category (and I'm short a bit of fuel). Maybe I should go for a bigger payload -- but my rocket is already insane.

Oh, should I count the launch clamps in the mass?

Edited November 1, 2013 by numerobis

[Moar Boosters]

Lets get the heavy leaderboard off to a start (or maybe super heavy )

Start weight - 4159.64t.

Payload weight - 503.09t

Payload ratio - 12.09%

Here is my rocket. 3 stages to orbit. Just standard staging. No asparagus or anything.

[mhoram]

Oh, should I count the launch clamps in the mass?

Launch clamps provide additional benefits by overcoming the launch-pad stickiness and an altitude advantage. So the mass should count into the payload fraction.

Will update the OP accordingly.

Lets get the heavy leaderboard off to a start

Thanks for your submission - it is a big monster.

Unfortunately I can not verify that the fueltanks in the payload are full, so please PM me/publish your craft file or update your entry with an orbit-picture where the resources-tab is open.

Edited November 1, 2013 by mhoram

[Moar Boosters]

Launch clamps provide additional benefits by overcoming the launch-pad stickiness and an altitude advantage. So the mass should count into the payload fraction.

Will update the OP accordingly.

Thanks for your submission - it is a big monster.

Unfortunately I can not verify that the fueltanks in the payload are full, so please PM me/publish your craft file or update your entry with an orbit-picture where the resources-tab is open.

The 3 booster stages get it to a 75km/~40km orbit, but the payload has to fire it's engine for a few seconds to complete the orbit. It was designed this way so it doesn't leave junk in orbit, as junk in orbit is a bad thing. Surely you can't penalize for that . If you see in the staging section, it shows there fuel tank is basically full. I would take more screenshots, but the rocket has already been used for a mission to Tylo.

[blizzy78]

It was designed this way so it doesn't leave junk in orbit, as junk in orbit is a bad thing. Surely you can't penalize for that .

One could also argue that the last stage should always have some fuel left to deorbit itself.

[mhoram]

The 3 booster stages get it to a 75km/~40km orbit, but the payload has to fire it's engine for a few seconds to complete the orbit. It was designed this way so it doesn't leave junk in orbit, as junk in orbit is a bad thing. Surely you can't penalize for that . If you see in the staging section, it shows there fuel tank is basically full. I would take more screenshots, but the rocket has already been used for a mission to Tylo.

Since the results should be comparable, I can not allow a 75x40 orbit.

I will reduce from the payload the mass that was used to get into the orbit because I have the impression that you do not intend to restart the liftoff - if I am wrong, please post pictures of your new try.

Getting from a 40x75 to a 75x75 orbit requires about 30.6 Delta-V. I assume that the engine is a Mainsail. For a 510 ton ship this means about 450 L fuel.

So an empty Rockomax X200-8 and an empty FL-T200 and a Mainsail amount to a 7.125 ton penalty for the payload and result in a 11.92% payload fraction.

[blizzy78]

Standard asparagus design using 8 boosters. Final stage had only 5 m/s left before decoupling.

Note that although some engines do clip into each other, I did not enable part clipping as per the rules.

Payload mass: 117.35 t

Liftoff mass: 728.93 t

Payload fraction: 117.35 t / 728.93 t ~= 16.10%

Number of stages: 6 (including final stage decoupler)

Craft file

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Edited November 1, 2013 by blizzy78
corrected stats for launch clamp rules

[mhoram]

So the mass should count into the payload fraction.

Since this formulation can be misunderstood, I precisised it in the challenge description.

Standard asparagus design using 8 boosters.

Nice ship. Thanks for sharing the craft file.

The launch clamps count as part of the ship and not of the payload.

[blizzy78]

The launch clamps count as part of the ship and not of the payload.

I've edited my post accordingly.

[John.E]

Baby Booster - Mini Percent V4.0:)

19.74T All Up Weight

2.44T Payload

12.36% Payload/AUW ratio

Craft File

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All seems rather meagre when compared with the other entries Small seems like it runs at a disadvantage due to engine, coupler overheads representing such a large proportion of any ship. I can only get better, and to top it all it was fun trying

[blizzy78]

12.36% Payload/AUW ratio

This can be improved by quite some amount. In your craft I see you are making a few mistakes:

- Too much fuel. This results in drastically lowering the TWR (and payload fraction), which will keep you in the atmosphere for too long.

- To get that much fuel up, you added more thrust by adding engines than would otherwise be necessary.

- Asparagus staging by using groups of 3 instead of 2. Using groups of 2 is better because you can ditch empty tanks sooner, but it's still balanced. (Using your staging, MechJeb reports a total vacuum dV of about 5100 m/s, whereas setting it up by using groups of 2, it reports 5300 m/s. Nice improvement for a simple rearrangement.)

- Use of stack size matching decoupler where the smallest works perfectly, too.

I've tried to improve your craft and came up with this: Craft file

It now has the same payload mass (2.44 t), but the whole craft weighs only 14.91 t, resulting in a payload fraction of ~16.36%. Also, the TWR is improved from 1.24 to 1.57.

Edited November 2, 2013 by blizzy78

[mhoram]

Baby Booster - Mini Percent V4.0:)

I can only get better, and to top it all it was fun trying

That's the spirit! Thanks for sharing.

I've tried to improve your craft and came up with this

It now has the same payload mass (2.44 t), but the whole craft weighs only 14.91 t, resulting in a payload fraction of ~16.36%. Also, the TWR is improved from 1.24 to 1.57.

I think it's cool that you improved his design.

Edited November 2, 2013 by mhoram

[mhoram]

I came up with another entry for the Light category.

Payload: 4.70 ton

Ship mass: 24.55

Payload fraction: 19.14%

Stages: 7

The first time, I managed to pass the 19% barrier

Javascript is disabled. View full album

Had to manually adjust the MechJeb Gravity turn.

[John.E]

This can be improved by quite some amount. In your craft I see you are making a few mistakes:

- Too much fuel. This results in drastically lowering the TWR (and payload fraction), which will keep you in the atmosphere for too long.

- To get that much fuel up, you added more thrust by adding engines than would otherwise be necessary.

- Asparagus staging by using groups of 3 instead of 2. Using groups of 2 is better because you can ditch empty tanks sooner, but it's still balanced. (Using your staging, MechJeb reports a total vacuum dV of about 5100 m/s, whereas setting it up by using groups of 2, it reports 5300 m/s. Nice improvement for a simple rearrangement.)

- Use of stack size matching decoupler where the smallest works perfectly, too.

I've tried to improve your craft and came up with this: Craft file

It now has the same payload mass (2.44 t), but the whole craft weighs only 14.91 t, resulting in a payload fraction of ~16.36%. Also, the TWR is improved from 1.24 to 1.57.

Wow, what an improvement. Thanks for the guidance

It didn't even occur to me about the coupler for the payload ( doh ) and I also noticed the small ( but none the less significant ) savings on the inter-stage couplers you made. As for the asparagus arrangement, I knew about 2 way as opposed to 3 way, I even missed feeding the main stack! a complete brain fart sort of day I must have been having, I am glad you pointed that out to me ( hopefully it will now stay embedded in my brain now ).

It's great to get feedback, hopefully I can remember the lessons passed along here and built LIGHT and manage to reduce the amount 'Sledgehammer to crack a small nut' approach I so often use

That's the spirit! Thanks for sharing.

Thanks for the challenge. I have discovered another way to loose a little more of my life to KSP now

[mhoram]

I think it is time to add a twist to the challenge.

I added an extra award, the "MechJeb Compliance Award"

This award is rewarded to rockets that reach orbit without human interaction between the launch and a periapsis of 74km.

Getting a good payload fraction by optimizing the gravity-turn is a valid strategy and I find it astonishing how much improvement this brings, but I also want to reward people who can build a lifter for MechJeb-ascent paths.

My demonstration entry is 18.02% mhoram (2.70 ton, 6 stages).

To qualify for this award state that MechJeb was used and submit a screenshot of MechJeb's ascent path editor.

Edited November 6, 2013 by mhoram

[blizzy78]

To qualify for this award state that MechJeb was used and submit a screenshot of MechJeb's ascent path editor.

I've posted a screenshot of the editor in my 100 t entry, and yes, I did use MechJeb for the ascent

[Nao]

I think it is time to add a twist to the challenge.

I added an extra award, the "MechJeb Compliance Award"

This award is rewarded to rockets that reach orbit without human interaction between the launch and a periapsis of 74km.

Getting a good payload fraction by optimizing the gravity-turn is a valid strategy and I find it astonishing how much improvement this brings, but I also want to reward people who can build a lifter for MechJeb-ascent paths.

That's quite good idea! It does nerf nuclear engines quite a bit thou, since mech jeb can't use them to their full potential. (burning at an ~30deg angle to set flight path just after last normal engine separation). But i'll try it later

[Nao]

So, i took another bite at the "no asparagus idea", also lowering my previous stage count to only 3 stages.

Payload: 7,4 t (this time it's fully 0.2 drag)

Launch weight 39,45t

Payload fraction: 18,76%

Screenshots were merged to save on the imgur image limit.

It was flown on MJ but it isn't mechjeb compliant since it needs flight path angle changes when staging and near the end of the burn. There is still room for improvement, and i think "no asparagus" has the potential to get above 19%.

[Kourston]

Hey Rocketeers,

my best result with an 80km stable Orbit is a Rocket with 300 tonn staging weight..

it reaches kerbin orbit at 80km with a total of 60 tonn .. all tanks are total full in the last stage.. it has docking clamps for the lander.. the fuel it is carrying are in total 1 and 1/4 orange tanks.

it has 4 atomic engines at the last stage with 3/4 of an orange tank to burn.. the lander has an 2/4 orange tank with 4 * 120kn attach engines 320 isp.. no prob for killing orbit velo..

low orbits will make the lander easy kill orbit, land and get back to the efficient atomic engine tank.. this rocket is able to bring 3 kerbals from kerbin to gilly, ike, dres and everything that is lower

then 0.2 g and back, as soon its higher then 0.2 g only landing is possible.. for the way back i never did it.

tried to land on duna and back but failed in an sun orbit.. always using planets, muns or even rocks as a catapult. but for all the rest this ship is very versitile.

i also have the smaller version that only brings 1 man everywhere.

but its 307 tonn staging.. 65 tonn orbit with full fuel.. so its 21.1 % payload fraction.

cheers and happy optimising

[Kourston]

21.1% payload fraction ! without any mod ! 80km orbit.. 60 ton payload, 45 ton of it fuel... interplanetary ship for 3 kerbals with docking clamb lander.. made dres, ike and gilly with return to kerbin.

http://s14.directupload.net/file/d/3438/mq62k9ig_jpg.htm

http://s7.directupload.net/file/d/3438/aowxxpe9_jpg.htm

http://s7.directupload.net/file/d/3438/log7xuu6_jpg.htm

http://s1.directupload.net/file/d/3438/hfwug8ew_jpg.htm

cheers..

[Kourston]

http://s1.directupload.net/file/d/3438/hfwug8ew_jpg.htm Edited November 11, 2013 by Kourston