Stock Payload Fraction Challenge: 1.0.5 Edition

[gchristopher]

Wow, you people are monsters. This challenge is the single biggest reason I keep reading these forums. Great work!

It's become fairly obvious that using cockpits in the payload, and using payload as structure, are really "unfair" advantages in multistage designs. I humbly suggest either

- separating the categories, with practical, reusable single-piece SSTOs in one and exotic unrestricted multistage designs in the other.

or

- adding additional restrictions to all spaceplane designs (i.e. must be able to achieve orbit with the payload missing).

I think as long as being multistage means you're inherently throwing away parts (since spent stage recovery is impossible without mods), I don't think it's a big problem that you're making clever use of the payload as structure. It would be a much more complicated and difficult to adjudicate challenge that considered how many tons or what cost was recoverable.

Considering the cockpit as "payload" is more of a thorny issue, because in my mind, "payload" implies some degree of arbitrary-ness, where you can specify a size, shape and mass of the payload, but not that the front 1/5th of the payload must be a particular cockpit, or else the launch doesn't work.

If the cockpit counts, why bother separating the engines from the front half of the "payload?" It's all mass in orbit.

I don't have any great suggestions, but thankfully this group doesn't seem too inclined to rules-lawyering. As a spectator, I'd be perfectly happy seeing a short note next to any entry that might have a counterintuitive idea of payload.

I'm still going to read all about more than the current winning entry, because the intermediate ones are often a lot more approachable and instructive than the ones where I couldn't fly the right profile even if I understood it. The new drag and mach dynamics are still mostly a mystery to me, and it's often easier to figure out what's going on with the less clever or optimized entries.

[tseitsei]

Added another great entry of yours to the leaderboard, tewpie.

You raise an interesting point. Since we have an update imminent, now might be a good time to open the floor to possible revisions to the rules and scoreboards. So far I am thinking:

- Only the best entry per participant on each board.

- Four boards: Multistage rocket, Single stage rocket, Multistage airbreathing, Single stage airbreathing

I'm not sure about the changes you suggest, tewpie, as recoverability/reusability is not really considered for this challenge. I am open to the idea though if others feel strongly about it.

Does anyone have any feedback to offer about further rule changes or the leaderboard revisions suggested above?

IMO there should be 4 categories:

Multistage rocket

Completely reusable rocket

Multistage airbreathing

Completely reusable airbreathing

Because I find the idea of ssto that cant be recovered quite stupid and unpractical... Complete reusability would practically mean ssto but it would also mean it needs to be recoverable. By completely reusable I mean that you can land it reasonably close to ksc and only thing that is needed for new launch is is refueling it.

[SpaceplaneAddict]

IMO there should be 4 categories:

Multistage rocket

Completely reusable rocket

Multistage airbreathing

Completely reusable airbreathing

Because I find the idea of ssto that cant be recovered quite stupid and unpractical... Complete reusability would practically mean ssto but it would also mean it needs to be recoverable. By completely reusable I mean that you can land it reasonably close to ksc and only thing that is needed for new launch is is refueling it.

This is my philosophy as an SSTO maker.

[Johould]

- Only the best entry per participant on each board.

- Four boards: Multistage rocket, Single stage rocket, Multistage airbreathing, Single stage airbreathing

I'm not sure about the changes you suggest, tewpie, as recoverability/reusability is not really considered for this challenge. I am open to the idea though if others feel strongly about it.

Does anyone have any feedback to offer about further rule changes or the leaderboard revisions suggested above?

Rather than going by participant, I'd rather keep all distinct designs. Whether or not they are in the rankings, it's also nice to have every accepted attempt linked from the first post. Maybe check out how the Goddard Problem Challenge has an "attic".

As for reusability of planes, I like seeing both kinds of designs, but it's also interesting to see which ones are at least semi-practical, so it would be nice to tag SSTO designs that can't reasonably be recovered (maybe as "SSTO*") if there are too many. But, I'm definitely against requiring enough fuel for landing as part of the scoring flight - minimizing that sounds like a very boring game of 69km aerobraking passes.

For defining "reusability", I think being able to *land* from orbit without a payload more closely tracks practicallity - an exposed payload design could still be useful for stocking fuel depots or with payload fairings, and I'd certainly expect them to fly less well without a payload, but as long as they don't disintigrate or incinerate on reentry it could still be used. Reusability with only refueling is too strict for planes - recovering and rebuilding is easy on Kerbin, and jets hardly work anywhere else.

I don't know about rockets, maybe SSTO and multi-stage are more interesting as separate challenges there. Strict "SSTO" might track practical goals better too - refuel from a depot and fly the whole thing elsewhere, or recover in one big piece.

[Right]

I'm happy with one entry per category per person.

One cheatery thing I've had success with is using aerodynamically shielded struts in the payload. The rules don't prohibit that, but probably should. I think you summed it up nicely in an earlier post...

The idea is that your test payload could be conceivably replaced with another and still have the ascent work.

I see the merit of taking this to the extreme and disqualifying payloads with cockpits, nose cones, or structure... but in reality 90%+ of payloads will have these things, so I think there is also merit to not going that far. (This also leaves room for some fun creativity)

Whatever you decide, I'll be happy with, since there are pros and cons to both.

[Red Iron Crown]

A quick update: I'm closing this to 1.0.4 entries as of now. I'm holding off on starting a 1.0.5 version for at least a few days just to make sure there's not another hotfix in the works.

Thanks for all the feedback on the rules. My thinking right now is to leave the actual rules as they are, if for no better reason than to be able to compare to previous versions.

I've revised my thoughts on the leaderboard divisions, here's the provisional plan:

Group 1: Unlimited staging and propulsion (basically multistage airbreathers, here's where the biggest fractions will be)

Group 2: Unlimited staging and rockets only (multistage rockets go here)

Group 3: Single stage, any propulsion (No discarded parts, recoverability not necessary. Both rocket and airbreathing SSTOs go here)

Group 4: Single stage, any propulsion, recoverable. (As Group 3 but the entire lifter must be recoverable one way or another)

Thoughts, opinions, objections?

[SpaceplaneAddict]

I like group 4.

[Val]

A quick update: I'm closing this to 1.0.4 entries as of now. I'm holding off on starting a 1.0.5 version for at least a few days just to make sure there's not another hotfix in the works.

I'm also holding back on making any entries, as MechJeb SmartASS isn't working for me atm, and I'm too lazy to fly manually.

Thanks for all the feedback on the rules. My thinking right now is to leave the actual rules as they are, if for no better reason than to be able to compare to previous versions.

I've revised my thoughts on the leaderboard divisions, here's the provisional plan:

Group 1: Unlimited staging and propulsion (basically multistage airbreathers, here's where the biggest fractions will be)

Group 2: Unlimited staging and rockets only (multistage rockets go here)

Group 3: Single stage, any propulsion (No discarded parts, recoverability not necessary. Both rocket and airbreathing SSTOs go here)

Group 4: Single stage, any propulsion, recoverable. (As Group 3 but the entire lifter must be recoverable one way or another)

Thoughts, opinions, objections?

I like these new groups, especially the addition of group 4.

It's a little sad that Rocket SSTOs won't have their own group(s), but on the other hand, they're not a great choice for high payload fractions, which is what this challenge is about.

Edited November 10, 2015 by Val

[tseitsei]

I'm interested in divisions 1 & 4.

1 because it's finding the absolute limit for payload fraction in current ksp.

And 4 because ssto without recoverability could just as well be considered multistage because it doesnt offer any advantage over multistage design.

Good changes. Will see what I can do in new version next week.

[numerobis]

Oooh, a new payload fraction challenge to sink my teeth in to!

I find category 3 to be a bit odd; how about morphing it to instead be SpaceX style: any propulsion, any staging, all parts recoverable (i.e. if you switch to a part you dump, you can recover that part -- it should be allowed to shed bits that physics culls).

[tewpie]

Non recoverable ssto planes really don't make much sense (how would they be different from recoverable ssto planes?) Cat 3 would be dominated by copies of entries from Cat 4 as it is.

How about making category 3 to be recoverable rockets like numberobis said or airbreathing rockets (no significant aero lift but jet engines allowed).

[Nefrums]

I suggest removing category 3, and only have 3 categories.

I'll soon post entries for 1.0.5 (as soon as I manage to stop playing some post apocalyptic game)

[Red Iron Crown]

You folks might be right about Group 3, maybe it would be better to have only fully recoverable rockets there instead?

[Sanic]

I suggest removing category 3, and only have 3 categories.

I'll soon post entries for 1.0.5 (as soon as I manage to stop playing some post apocalyptic game)

I hope KSP hasn't fallen out of you favor.

Puns4days.

[Right]

I think group 4 should be recoverable under its own power - thus recovery through sending up an additional vessel for retrieval would not be acceptable.

[Red Iron Crown]

I have updated the OP and am now accepting entries for 1.0.5. The categories have been added:

Unlimited - Use any type of propulsion to get to orbit, no recovery necessary.

Unlimited Recoverable - Use any type of propulsion to get to orbit, all non-payload parts must be safely recovered.

Rocket Only - Rocket engines only (no ions, jets, or Rapiers in open cycle mode), no recovery necessary.

Rocket Recoverable - Rocket engines only (no ions, jets, or Rapiers in open cycle mode), all non-payload parts must be safely recovered.

I think group 4 should be recoverable under its own power - thus recovery through sending up an additional vessel for retrieval would not be acceptable.

That's a good point, I'll specify that it's single launch and no resource transfer with other ships.

[tewpie]

I have updated the OP and am now accepting entries for 1.0.5. The categories have been added:

Unlimited - Use any type of propulsion to get to orbit, no recovery necessary.

Unlimited Recoverable - Use any type of propulsion to get to orbit, all non-payload parts must be safely recovered.

Rocket Only - Rocket engines only (no ions, jets, or Rapiers in open cycle mode), no recovery necessary.

Rocket Recoverable - Rocket engines only (no ions, jets, or Rapiers in open cycle mode), all non-payload parts must be safely recovered.

That's a good point, I'll specify that it's single launch and no resource transfer with other ships.

Does unlimited recoverable allow the use of parachutes? I suggest locking it down to powered/glide recovery only to preserve the spirit of having a category of practical spaceplanes...

[Red Iron Crown]

Chutes are fine, a plane pays a mass penalty for them. For that matter, a plane that is recovered with chutes *is* a practical spaceplane, no?

[tewpie]

Chutes are fine, a plane pays a mass penalty for them. For that matter, a plane that is recovered with chutes *is* a practical spaceplane, no?

Ok, but I foresee a bunch of multistage planes using various tricks to recover their jettisoned parts. IMO what distinguishes a practical plane is that the plane can be guided to the runway for 100% recovery.

[Red Iron Crown]

Ok, but I foresee a bunch of multistage planes using various tricks to recover their jettisoned parts. IMO what distinguishes a practical plane is that the plane can be guided to the runway for 100% recovery.

We're looking for full recoverability, not purely SSTO planes. If someone can figure a way to stage and recover that increases their fraction over a single stage design, then that should rightfully beat the single stage design, IMO.

If it's anything like the previous leaderboard, there might be a handful of designs that take advantage of this, most of them will be SSTOs anyway.

[Jouni]

I built a quick 1.0.5 entry. A pure rocket, as always, and deliberately not too optimized.

It's a reasonably big rocket with 18 Vectors and no other engines. The boosters were gimbal locked, while the gimbal range of core engines was limited to 20% of the maximum.

MechJeb says more, and I'm not sure why. Perhaps it counts the launch clamps, which were necessary, because the Vector has a tendency to explode if it touches the launchpad.

Each booster had a Sepratron with 1.6 units of fuel. They weren't strictly necessary, but it was too easy to hit the falling boosters without them.

I did a few short burns during while coasting to rotate the rocket and dropped the interstage fairing at around 55 km.

The service bay in the core stage contains reaction wheels, a probe core, and a battery. Six struts connect the payload to the fairing base, and another four struts connect the fairing base to the core stage.

Entry name: Space, Vector

Launch mass: 1055.93 tonnes

Payload mass: 276.53 tonnes

Payload fraction: 26.19%

[Red Iron Crown]

Added you as the first entry on the new board, Jouni. Nicely done, I am sure we'll be seeing a lot of Vectors in the rocket entries.

[Right]

Yeah...the Vector is an extremely good engine. Its TWR, ISP ASL & vac, gimbal, and crash tolerance all blow the LV-T30 and LV-T45 out of the water. The Mammoth is the only engine that can match its performance for atmospheric pushing. While the mammoth has slightly better TWR, the vector potentially has like 1/9th the drag while only at 1/4th performance.

[KerikBalm]

I don't have full documentation, or an appropriate test payload, but I can confirm that >30% payloads with SSTOs that will also survive re-entry are possible in 1.05:

[Val]

Well. I finally got around to making an entry.

Air-breathing SSTO spaceplane as usual.

A new evolution of my trusty C-1 Payday, rebalanced to have Wet and Dry CoM on top of each other. The challenge payload also does not move either CoM, so it should be easily recoverable.

GTOW = 320.69 t
Payload = 171.00 t
Payload Fraction = [B]53.32 %

[/B][URL="https://drive.google.com/file/d/0B34u1G2080ndRm5aNExHOWduRjg/view"]Craft file[/URL]

Doesn't quite get the fraction of the Mk.7 as it needed a bit more fuel to punch through the atmosphere at 23-29 km.

[imgur]KMMTg[/imgur]
[B]Edit: [/B]Now including recovery.

Full launch, unedited video (~11 mins)

[video=youtube;MO-6Dur_Alk]http://www.youtube.com/watch?v=MO-6Dur_Alk[/video]
(should be available 30 mins after posting this)

[video=youtube;iuNsDJzqbNE]http://www.youtube.com/watch?v=iuNsDJzqbNE[/video] Edited November 21, 2015 by Val
Added recovery video