Payload Efficiency Challenge

[Laie]

As to the question about kOS, I don't think I see a problem with it. Is there any conceivable situation in which it would give a higher theoretical efficiency?

kOS is the scriptable autopilot. It does nothing to increase performance, but being able to program your very own ascent can be a powerful tool.

Excellent results on the second entry! I think your multistage recovery techniques will be the key to the best efficiencies for rockets.

Maybe, maybe not. It forces an inefficient ascent profile and comes with inevitable recovery losses. For now, it looks as if it would come out even with other technologies.

I wonder, do you think using an even steeper ascent and landing the first stage at KSC would improve the score?

Probably yes, but I don't expect that it will really be worthwhile. Getting it right will require a lot of skill, though, either at the controls or when programming the autopilot.

Personally, I think that two-stage thing is a good approach when you want to launch a vessel that can do the last 1000-1500m/s of the ascent under it's own power. Just add a suffcient amount of LFBs (which are cheap, and can usually be recovered at 80% or better) and be done with it. It's more expensive than a dedicated SSTO for the same vessel, but not much more expensive, and development time for the lifter tends towards nil.

However, tanking the concept as far as I'm doing with these entries is a challenge thing. For "real-life" launches, I'd consider it to be more trouble than it's worth.

[SanderB]

Hi Laie,

Your rocket now comes with

.

At the end of the video I forget to include the decoupler in the payload, but with it included the costs come down to 520.04 kredits a ton. It could probably go down by another ~1.8 kredits if I make a higher velocity touchdown.

[Right]

The 500 funds/tonne barrier has been broken!

Payload Mass: 26.3

Launch Vehicle Cost: 94,880

Recovered: 81,768

Part count: 35

Payload Efficiency: 498.6 Funds/tonne

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Some notes to build on:

The S3 engine is extremely good. One of the lowest TWR and very reasonable ISP.

The large Kerbodyne tanks have a worse dry mass ratio (counter-intuitively) than other tanks, so avoid using them when possible.

1 Parachute for every ~12 tonnes of landing mass is generally all you need. Land on small gear bays to save on mass, or on engines with high crash tolerance.

The small RT-10 SRBs are the most cost effective at accelerating a craft to terminal velocity.

Edited January 31, 2015 by Right

[Mesklin]

Unnamed rocket SSTO, one big engine and best current tanks - Mk3 rocket fuel tanks:

Delivery cost: 440.5 funds per tonne, if I not did mistake in calculation (start cost - 109008, empty cost - 99828)

Payload mass: 20.84 t

Start mass: 140.030 t

Not smooth or too exact landing in Jeb's style, but nothing were destroyed, only broken links between parts, use tape for repair

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[kcs123]

Apologize if this is not valid entry. It is moded SSTO space plane.

Requires mods: FAR, B9 , B9 Procedural Wings, Adjustable landing gears

I have used MJ only for info and to create nodes once I'm in space. MJ autopilot don't like FAR too much. Only SAS pilot assistance used to keep pitching stable.

SpacePlane Mk2 B9PW V0.90 - craft file.Parts count: 98; Cost: 103,104.00

Tested with 32.25t payload to orbit. More then enough fuel left for higher orbit and reentry. Plane was designed in such way that you can glide to runway from orbit without engines.

If you assume that all fuel is consumed, fuel cost+monopropelant is 4,888.00 Payload is kibbal from station science mod (not required for craft file) dock port and some struts making 32.25 t.

Efficiency should be: 4,888.00 / 32.25 t. = 151.56 cost/t

In very rare occasions like in my test flight you will be able to put 32.25t, so I consider this as light cargo entry, but you can put it in any category if this entry is accepted.

I'm still recreating my planes from V0.25 for medium/heavy category. You will find soon my additional craft files in craft exchange forum.

SpacePlane Mk2 B9PW - trip to orbit with payload

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[Right]

It was becoming clear that there was already plenty of incentive to have a sustainable design (no orbital debris). Why put junk in LKO when you can bring it back for a full refund? Also, every entry earned it, making it unremarkable. In its place I've created tech level based awards. This should add a completely new layer of competition as well as pragmatism to designs. And if some spiffy text award isn't incentive enough, just think: your launch vehicle might become famous as the best way to get stuff into LKO in some portion of career mode.

Unnamed rocket SSTO, one big engine and best current tanks - Mk3 rocket fuel tanks:

Delivery cost: 440.5 funds per tonne

Wow, way push the bar! Excellent job. And your right about the tanks, I completely forgot to check them!

Apologize if this is not valid entry. It is moded SSTO space plane.

Its valid, though modded entries have a separate bracket. Beautiful plane, and excellent flight log!

[Laie]

Unnamed rocket SSTO, one big engine and best current tanks - Mk3 rocket fuel tanks:

Delivery cost: 440.5 funds per tonne, if I not did mistake in calculation (start cost - 109008, empty cost - 99828)

Yeah, you're using exactly 100t of fuel, 9180 funds. You're aware that this is another spinoff of Slashy's design, are you? I briefly considered this myself, but didn't expect that going from kerbodyne to Mk3 tanks would really make much of a difference. Fat chance, turns out you saved 30% fuel!

I tried to do one better by again adding boosters and/or additional engines, but that won't work this time. Looks like you found a sweet spot. It may be possible to tickle out a little more by adding or removing small amounts of fuel (Mk3 parts make that easy), then tune the payload to the maximum that the given amount of fuel will carry. But I don't expect that the effect will be larger than 10-20 funds/ton.

@Right: you may want to consider listing procedural wings under stock. In terms of weight/lift ratio, they're worse than stock wings; their sole benefit is that they save a lot of parts. One could still have the same rigidity in stock through MOAR STRUTS.

[SanderB]

Mesklin (or someone else) can I ask how you can input turn end altitde in Mechjeb Ascent Guidance? I can find no way to manipulate it. I have MJ 2.4.2.0.

Edited January 31, 2015 by SanderB

[Laie]

Mesklin (or someone else) can I ask how you can input turn end altitde in Mechjeb Ascent Guidance? I can find no way to manipulate it. I have MJ 2.4.2.0.

When you uncheck "automatic gravity turn", you can set your own start and end altitudes.

[GoSlash27]

Yeah, you're using exactly 100t of fuel, 9180 funds. You're aware that this is another spinoff of Slashy's design, are you? I briefly considered this myself, but didn't expect that going from kerbodyne to Mk3 tanks would really make much of a difference. Fat chance, turns out you saved 30% fuel!

I tried to do one better by again adding boosters and/or additional engines, but that won't work this time. Looks like you found a sweet spot. It may be possible to tickle out a little more by adding or removing small amounts of fuel (Mk3 parts make that easy), then tune the payload to the maximum that the given amount of fuel will carry. But I don't expect that the effect will be larger than 10-20 funds/ton.

Unfortunately, I won't be able to participate in this for a while. My neck and shoulder are fubar'd again.

I can, however, enjoy watching people raising the bar on this challenge, so AFAIC "mi rocket es su rocket".

FWIW, I have run a ridiculously tiny payload SSTO that was able to manage under $450 per tonne using the 48-7S. Might be worth playing around with...

Release the hounds!

-Slashy

[Pamynx]

Here is my entry, modded one, with my Atlas launcher.

I was in need to refuel my "asteroïd hunter", Artémis, and send some snacks up there. Thus the payload is a dockable fuel tank and a big supply tank.

Screenshots :

http://imgur.com/a/HC8wj/embed

A video of the taking off (Very agressive, using MechJeb) :

After the docking, for some reason, prograde was replaced by retrograde.

When landing, do not forget to put the remaining fuel in the tank in the front to gain in stability with the "arrow effect". When landing, put back the fuel in the 4 tanks to lower the center of mass.

Feet on top can be useful to avoid exploding all the ship if your landing place is not flat.

My mods :

Physics : FerramAerospaceResearch / DeadlyReentry

Parts : RemoteTech / TacLifeSupport / ProceduralFairings

Piloting with parts : KerbalEngineerRedux / MechJeb2

Piloting without parts : MechJebFARExt / PreciseNode / Trajectories

Total ship cost : 93971 kerbucks

Payload cost : 93971 - 79136 = 14835 kerbucks

Recovered : 65589 kerbucks

Total cost : 13547 kerbucks

Payload mass : 216,096 - 194,643 = 21,453 tons

Score : 13547 / 21,453 = 631 kerbucks per ton

Given the amount of fuel left on landing, I think I can go with a payload a little bit heavier.

Technologies of tiers 6 needed :

- Advanced MetaWorks (3,75m heatshield).

- Unmanned tech (OKTO2).

- Large electrics (Z-1k battery)

When needed, one can put on top of the 4 FTL800 tanks either mini ion satellites I use for transmissions in LKO or automated claws I use to build stations on asteroids.

Edited January 31, 2015 by Pamynx

[Right]

And finally, a jet entry:

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Launch vehicle cost: 13,998

Recovered: 13,825

Payload mass: 6.765 tonnes

Payload cost efficiency: 24.1 Funds/tonne

Definitely not mechjeb compliant. I'm noticing jet based designs are very finicky when trying to optimize your cost efficiency. Moderate to heavy dependance on small differences in the flight path, and tweaking of more than one fuel source can be a headache. Landing took many attempts without wings, so definitely need to include some of those next time. Also forgot batteries which was almost fatal...However I managed to set up a suborbital trajectory and throttle up before running out of power. When I re-entered the atmosphere, the jet's alternator kicked in and saved me haha

[Laie]

16 turbojets, 4 shock cones each + 4 basic jets + 2 nervas have just taken four orange tanks to orbit for 15.4 funds/ton.

Pics will have to wait, I'm long past bedtime (wonder how that happened?)

[Mesklin]

Mesklin (or someone else) can I ask how you can input turn end altitde in Mechjeb Ascent Guidance? I can find no way to manipulate it. I have MJ 2.4.2.0.

Use radio-button, marked by red circle

[ttnarg]

Cost of craft = 154040

Cost of payload = 12800

upperstage empty = 39581

first Stage empty = 81096

Payload mass = 36Tons

Cost per Ton = 571.2

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I feel a bit bad about claming 100% recovery for the lower stage as there is no where I could get that one at 100% (I got it at 98% i think) upperstage I could of got at 100% with a few more trys and if I remembered to put some solar pannels on. (had to land this one quick as I was running out of power so didnt even try to land it at KSC)

This was built more as a test to see what I could do with a 2 stage rocket with a single "S3 KS-25x4 Engine Cluster" lower stage.

[Right]

@ Pamynx: Is that really the most efficient gravity turn in FAR? I know its supposed to be much earlier, but 0.6km with a 5% turn shape? Wow.

@ Laie: I'm eager to see this! Thats impressive.

@ttnarg: Not bad! I'll grant you 100% recovery because you landed so close. However, as a rule that 1st stage should be calculated at actual recovery value, since the distance from KSP corresponds to how much you gravity turn and save fuel. On a side note: whats up with the side mounted probes? You could do without that extra mass lol

Edited February 2, 2015 by Right

[ttnarg]

@ttnarg: Not bad! I'll grant you 100% recovery because you landed so close. However, as a rule that 1st stage should be calculated at actual recovery value, since the distance from KSP corresponds to how much you gravity turn and save fuel. On a side note: whats up with the side mounted probes? You could do without that extra mass lol

There was no turn with the first stage. which is why it landed so close but with out more fuel for the landing I had no way to target a landing spot. But dont worry that was just a prototype and I've fixed my landing problems for my 100T craft I'm building.

The probe cores out on the slide because there is no proble core of the largest size and even if there are the larger probe cores have more mass anyway. By putting them on the side I can use the smaller ones unless I'm missing somthing.

[Pamynx]

@ Pamynx: Is that really the most efficient gravity turn in FAR? I know its supposed to be much earlier, but 0.6km with a 5% turn shape? Wow.

I spent a lot of time finding the right ascent profile because I was used to pilot the ship myself and control the turn because there are 2 problems :

- You can easily make a flip in the beginning of the ascent.

- By the end of the ascent, I have a very low but efficient push and need to fight the gravity in order to circularize if you did not start your gravity turn soon enough.

I am also surprised but it worked

[ttnarg]

Fueled Lifter with payload = 438,016

unfueled Lefter with payload = 394,826

fuel cost = 43,190

playload mass = 102.5

fuel cost per ton of playload = 421.4

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Edit:

I should of put a reaction wheel on the second stage. Targetting the landing was hard. Maybe I should of done the wheels thing on the second stage.

The flight is quite hard. You have to turn the first stage to about 1 deg east to cope with the turning of kerbin, if your not landing on the flat the first stage breaks up on landing. Once I stage I roll hard to 80 deg. The single KR-2L brealy has the thrust needed to get into orbit before I have to switch back to the first stage. At which point I deploy the gear hit the shoots and then seperate the cores which inculdes Sepratrons to push them apart. All in all not MechJeb Compliance.

Edited February 2, 2015 by ttnarg

[Laie]

(/ (- 416667 362970 51480) 144.0) 15.3958333 funds/ton

Flight was controlled through kOS; the ascent is a good bit steeper and slower than what most people suggest. I hope that there's enough pictures for curious minds to re-create the profile (if someone is really that curious). Most pics were taken just after something happened; you may also want to look at the console, flight data is updated every second. ttta is "target time to apoapsis" the vessel tries to maintain; pitch and throttle should be obvious. The program is following a scheme that seems to work reasonably well for all kinds of jet-powered craft; I have not tried to optimize it for this particular vessel, and besides, my programming skills leave much to be desired. So I guess that there's still room for improvement.

- - - Updated - - -

There was no turn with the first stage. which is why it landed so close but with out more fuel for the landing I had no way to target a landing spot. But dont worry that was just a prototype and I've fixed my landing problems for my 100T craft I'm building.

The probe cores out on the slide because there is no proble core of the largest size and even if there are the larger probe cores have more mass anyway. By putting them on the side I can use the smaller ones unless I'm missing somthing.

You're landing on the far side of KSC because you went straight up while Kerbin kept turning underneath you. Hitting the launchpad would require you to initiate a very slight turn and then stage at just the right time. Good luck with that. For purposes of this challenge, I think the two-stage approach isn't very promising. It's much easier to do (and more worthwhile) if you're going for a higher orbit, though; next time you have to send something to 100-120km, remember the two stages. Especially if the payload happens to be a vessel that can circularize under it's own power (TWR=0.5 is usually enough), which is explicitly forbidden for this challenge.

As to mounting the probe cores, I'd like to point you to the "structural fuselage" (a white drum that looks almost like a jet fuel tank). Weighs less than the girders and is bigger, providing room for probe cores, proper parachutes, or extra engines. Or if you really only want to mount a probe core, just use a weightless cubic strut and have the core clip slightly. I don't think anyone will blame you.

[ttnarg]

yes if we where aiming for a higher orbit then 2 stage would be easyer. But I still say 2 stage is the way to go for non jet crafts. Even if you need a large engine like the KR-2L to get get to orbit before switching back. I knew about Kerbin turning, in my 102.5 t lifter I tryed to cope with that but we talking about fractions of degees a few times I ended up in the sea when I turned too far.

Would be intressing to use this mod maybe even do gravity turns and then boost back with first stage (SpaceX style). I have not tryed it but it looks good.

http://forum.kerbalspaceprogram.com/threads/80292-0-90-0-Flight-Manager-for-Reusable-Stages-%28FMRS-v0-3-01%29

[Laie]

Edit: Post removed. I made a huge claim that won't hold up to scrutiny. Sorry.

Edited February 3, 2015 by Laie

[Right]

fuel cost per ton of playload = 421.4

Wow, this is a good leap forward! And on top of that, a >100 ton lifter! Most unusual flight path and awesome recovery plan. Congrats on taking the #1 spot...for now

(/ (- 416667 362970 51480) 144.0) 15.3958333 funds/ton

Quite an exotic design! Color me impressed. I would not attribute such accomplishments to the craft based on looks alone haha. So what do you think the key(s) is? Airhogging? Nuclear engines? And I have to ask, would the craft do worse if those 4 basic jets were turbos?

On a side note, how do you prevent asymmetrical flameout/throttle down. I stack my intakes properly, but I still get one side's jets throttling down while the other side is on full.

You both earned some rep with those!

[Laie]

fuel cost per ton of playload = 421.4

Ouch. I totally missed that bit. Giving advice about how two-stage is worn out just after you made a new best was... not sensible.

Quite an exotic design! Color me impressed. So what do you think the key(s) is?

Probably that the number of engines is a power of two, allowing me to switch off exactly half of them when the air becomes too thin, again and again. And the ascent profile where I don't really level off and build speed, but try to gain both speed and altitude at the same time. I could write a whole essay about the pros and cons of this... the long and short of it is that it seems to work well.

The many intakes also matter, of course. Two jets with two intakes will always provide more thrust than a single engine with four intakes, but not so much more as to justify the doubled fuel consumption. So I think the most effective jet lifter will need to have just enough engines, but as many intakes as possible. There's probably a point where the extra drag at low altitudes offsets the later gains, but with four shock cones I'm not there yet.

Then, this thing is very bare-bones, with as little dead weight as possible. You could maybe strip another two or three tons, but that's it. Having a cargo bay over the whole length of the payload would be 20t extra; and another 5t if you also want a proper tip and tail. That alone would increase the cost to ~19funds/ton (which is still dead cheap, if you think about it).

The basic jets are there to speed up the process of getting to 10-15km; actually, without them the vessel could barely take off and would take minutes to reach 2km. A winged design would fare better, but I'm not going to piece together sufficient wing for 200t from stock parts. Also, they don't have any intakes of their own -- they've been slapped on as an afterthought to increase initial TWR. For that purpose, they're better than turbos, and cheaper to run than SRBs or rocket power.

[kcs123]

@Right, thanks for kind words. I found a typo in OP. In Pamynx entry says about payload that is 21.61 while in OP is 216.1. I'm not envy, I was just curious to see 216t lifter and left disapointed.

I wanted to build 400t SSTO lifter, but I failed to do it. Maybe it could be done, but will require a lot more time to optimize craft, so I have to satisfy with only 367.4t

In lot of places I have found info that "SpacePlane with large wings is not good due to large drag and dead weight in space.", "Sucessfull SpacePlane need to have more than 1 TWR to be able to reach orbit."

I was too stubborn to listen that, so here is my "failure" as second entry for this chalange.

SpacePlane S3 B9 B9PW - with payload:

Parts count: 199; Cost 422,458.00; Weight: 722.530 t

SpacePlane S3 B9 B9PW - without payload wet cost/mass:

Parts count: 150; Cost 406,070.00; Weight: 355.130 t

SpacePlane S3 B9 B9PW - without payload dry cost(fuel and monopropelant removed):

Parts count: 150; Cost 384,967.00

Efficiency should be: 21,103.00 / 367.4 t = 57.43 cost/t

Link for craft file is in signature, with one exception - two craft files, with plane shown in galery (minus fuel from one cargo bay) and more optimized variant with some extra struts and info in craft file. Plane is more than capable to land at KSP as glider, only problem is it's weight, so you need to be extra carefull to not destroy runway.

If you can't land exactly on runway there is still enough clear land nearby for 100% recovery.

For penalty that I didn't provided re-entry pictures I have removed all fuel and monopropelant in SPH editor for above calculations.

SpacePlane S3 B9 B9PW - test flight to orbit with 367.4t of payload.

Require mods: FAR, B9, B9 procedural wings, Adjustable landing gears.

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