Stock Payload Fraction Challenge: 1.0.5 Edition

[Rune]

Nicely done, Rune! I've updated your entry in the leaderboard, your craft also has the distinction of the longest name of any entry.

You can shorten it up to RecordBreaker, it's the name of the particular bird that made the trip, in it's second tweaking. See, that is how I keep track of my stuff, the SSTO is obvious, Mk LIV means it's the 54th model that short of works (Kod I have been making SSTOs long... that doesn't count failed concepts), and Longsword is the model name. Then, if I make any special version, that gets added to the end, along with a mission number if necessary. But yeah, I often shorten it myself if it's going to be in the tracking station for any length of time... this bird's designation ingame would be, for example, SS-LX "RecordBreaker", for SSTO, Longsword-based, eXperimental model. Other examples would be CS-01 "Spatha" for the first Crew Shuttle of the Spatha model, or LE-03 "Copernicus", for the third Lander, Eagle model, that happens to be called "Copernicus" so I can distinguish it from it's siblings. But since this was actually done in a hurry...

Rune. In any case, a mouthful. Use the one that looks cooler.

[rocx]

Rune, I broke your record again. By more than 4%. During a test flight that I wasn't planning to take to orbit. With lots of fuel left on both stages. Take off mass 31,66 tons, payload mass 11,78 tons, 37,21% efficiency.

The secret to this improved efficiency is not building useless parts such as cargo bays, wheels or wings.

My first stage flamed out with almost half the fuel in the tanks left, and the core stage made it to orbit easily.

Here you see Jeb and his three loads of ore just before decoupling.

I am working on a design that will reach over 40% payload mass, and when it's working you will get some more pictures.

Edited June 24, 2015 by rocx

[Red Iron Crown]

rocx, you're going to have to document a bit more than that, please. At least show mass on the pad and of the decoupled payload, for your last entry I rebuilt the craft in the VAB to check your numbers but I'd like to not have to do that.

Looking forward to the 40% craft, I'm not sure if the limit is as high now that jet Isps have been nerfed.

[Rune]

Rune, I broke your record again. By more than 4%. During a test flight that I wasn't planning to take to orbit. With lots of fuel left on both stages. Take off mass 31,66 tons, payload mass 11,78 tons, 37,21% efficiency.

Ah, stages, so that is a two-stage design right? No wonder you beat me! You could go over 50% in 1.02 with that. In fact, I didn't expect my record to last very long anyway, since people here are pretty crazy (and there is at least one 1.02 design that did better than RecordBreaker). In any case, we can happily share first place on two different boards, and declare the non-rockety thing started once you clear the legalities with Red Iron Crown I don't get how boards work but whatever, I'm still first of the single stages.

Rune. Not likely that I try that one, I usually design for cost.

Edited June 24, 2015 by Rune

[rocx]

All right then, here it is. 37,06 tons on the pad, 15,28 tons of payload. 41,23%.

This has become quite a tall rocket. The difference in ISP between airbreathing and rocket mode is very visible here: the two side tanks provide 3589,1 m/s for five engines, the tall core tank provides just 854,2 m/s.

Takeoff is a bit slow with the 1,44 TWR and spooling up of the Rapiers. Pitching down towards 20 degrees.

At max Q, between 10 and 12 km, SAS has to be switched off because the tall rocket is wobbling like crazy. Also Valentina is almost fried in her cockpit.

At 28 km there are still 74 units of fuel left, but air has run out.

So it's time to thank the boosters for their service and condemn them to a splash of death.

One and a half minute of burn later apogee is at 70 km. Small correction burns are necessary to compensate drag losses at this altitude.

After a swift apogee kick the orbit is circularised, with 10% fuel and oxidiser left.

The payload: four 0,5t ore tanks with 3 tons of ore each, and a cockpit with monopropellant (1,28t), for a total of 15,28t.

Clearly there is some room left, but my next attempt will probably be a simpler model, with less graphics, because this took a long time on my old laptop. 45% should be possible with a similar rocket.

Rune: I concede to you the one-stage title. My Longsword design was reaching its limits, and may never have reached 33%. So I switched to a different idea.

Red Iron Crown: Is this documented enough?

[Norcalplanner]

I'm somewhat sad that I'm travelling and away from my computer at the moment. Not only am I not getting my hands on the new version of KSP, I can't do an entry for this challenge.

[Red Iron Crown]

Red Iron Crown: Is this documented enough?

Looks to be. Fantastic fraction, unconventional design, and a punny name; ticks all the boxes for a great entry! Added to the top of the board.

I'm somewhat sad that I'm travelling and away from my computer at the moment. Not only am I not getting my hands on the new version of KSP, I can't do an entry for this challenge.

It's been ongoing for almost two months, the challenge will be waiting when you return.

[Slugy]

Now that Mk3 parts are not so buggy I have a minimal Mk3 based SSTO cargo hauler.

Still not worked out the most efficient ascent, the one shown was ok, but probably not optimal.

123.13t out the hangar (a bit less by the time the brakes come off) and 50.65t delivered to LKO for 41.15%, with a little fuel left over.

In the pics below KER is badly confused - both on how many engines actually have fuel and how much dV there actually is (compare the circularization burn numbers, it was most confusing while I was testing it ...)

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I was surprised to find that there was never any danger of overheating the wings!

Edited June 24, 2015 by Slugy

[Red Iron Crown]

Another great entry, slugy! Added to the board.

I think KER is struggling when RAPIERs are drawing fuel from tanks not connected by crossfeed rules, at least in rocket mode.

[rocx]

I have made a rocket with about 46,5% efficiency, but I just came short 20m/s at circularisation. A few more tries and I can show you.

[RuBisCO]

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Upgraded my Xylol to 1.0.4. The Xylol 5B can lift 59 t to a 80 km with enough fuel to spare for a return to port. That is a 31.27% cargo mass fraction. Again the Xylol 5B was not designed for cargo mass fraction records, just to lift BIG cargo to orbit and land back (minimize cost to orbit for career mode) and look good while doing it. I might be able squeeze more out of it but I rather make a dedicated record breaking model for that.

Here is a zip with Xylol 5A (extra docking port and RCS) and Xylol 5B, with and without MJ case.

http://www./download/xn6a39krn9n265h/Xylol+5.zip

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http://www./download/4wirhyyzpoicwrg/Xylol+5RB.zip

Ok so here is a the Xylol 5 RB, Down to 121.2 tons empty, reduced wing area, cut down cargo bay to only what is needed and reduced tail (like NikkyD suggested). It now flies like a shopping cart with cardboard wings attached but it made it to >70 km orbit carrying 68.4 tons of cargo and even with enough fuel to spare for a return attempt, little chance it will make it back to port though with the way it flies.

So that is 36.08% cargo mass to orbit

Launch Regime is:

1. Start with cargo bays open, close them before starting engine (custom09)

2. Close pre-coolers (custom06) and start engines at full power

3. Lift off to 30° pitch and maintain attitude

4. At 12 km dive to 0° pitch

5. Open pre-coolers at 500 m/s surface speed

6. Rise to 5° pitch at 600 m/s

7. Rise to 10° pitch at 800 m/s

8. Rise to 15° pitch at 1000 m/s

9. Rise to 20° pitch at 1200 m/s

10. Switch one set of RAPIERS to rocket mode when surface speed stops increasing (custom04 or custom05)

11. After other RAPIER switches automatically (~29.7 km) close pre-coolers and shut off jet engines (custom01)

12. At 40 km dive to 10° pitch

13. Cruise at 10° pitch once apoapsis exceeds 70 km

14. Circularize at apogee

[Rune]

In fact, I didn't expect my record to last very long anyway, since people here are pretty crazy

Now that Mk3 parts are not so buggy I have a minimal Mk3 based SSTO cargo hauler.

Still not worked out the most efficient ascent, the one shown was ok, but probably not optimal.

123.13t out the hangar (a bit less by the time the brakes come off) and 50.65t delivered to LKO for 41.15%, with a little fuel left over.

Ok so here is a the Xylol 5 RB, Down to 121.2 tons empty, reduced wing area, cut down cargo bay to only what is needed and reduced tail (like NikkyD suggested). It now flies like a shopping cart with cardboard wings attached but it made it to >70 km orbit carrying 68.4 tons of cargo and even with enough fuel to spare for a return attempt, little chance it will make it back to port though with the way it flies.

So that is 36.08% cargo mass to orbit

Well that took long. Congrats guys! I honestly didn't think 40% single-stage was doable, so double kudos to our new champion. There can't be much more room for improvement now...

Rune. I have just poked a bear, haven't I?

[Red Iron Crown]

I see the new version hasn't slowed you down, RuBisCO, your fraction actually improved even with lower airbreathing Isps. Well done, added to the board.

[rocx]

Finally! The Assisted Launch Primarily Airbreathing Cargo Ascender (abbreviated A.L.P.A.C.A.) has made it to orbit! And the magic number is... 44,56%! Click the spoiler tag to see how it is done.

The A.L.P.A.C.A. is a descendant of the Alpacalypse 2, with slightly more fuel but 55% more payload. It's takeoff mass is 41,185, and the payload mass is 18,35. I took extra care to add an extra reaction wheel and battery on the core stage, since the Aerospike doesn't have gimballing, and we're not allowed to use the payload's torque or battery.

Rapiers seem the way to go for highest efficiency, flaming out at higher speed and altitude than Whiplashes. But the limiting factor is always their static TWR. For example the Rapiers on the A.L.P.A.C.A. give it a TWR of 1,04 when completely spooled up. So how does this take off?

By assisted launch! When the Rapiers reach 70% thrust, the Aerospike is switched on and drains fuel from the two FLT-100's in the booster stages.

This burn only lasts 18 seconds, but that is enough to bring the Rapiers to 140 m/s, after which their thrust only increases.

The sound barrier is broken in 47 seconds. Jeb tries to keep a 20 degree pitch.

The cockpit is getting a little warm at max Q, but nothing that Jebediah can't handle.

On this launch air runs out slightly before fuel, 47 fuel units left over in the side boosters.

After staging the core stage takes over, also recharging the battery (Rapiers don't have alternators). Jeb looks quite happy.

With its low TWR of 0,69 raising apogee takes a while, but staging velocity was high enough that the thrust doesn't have to be pointed away from prograde.

When the Aerospike is shut down, the A.L.P.A.C.A.'s orbit actually has a perigee!

A 59 m/s burn was enough to circularise the orbit. 6 fuel units are left.

Content with a mission accomplished, Jeb undocks the 18,35 tons of payload.

So can this be improved upon? Seeing as I had tiny amounts of fuel left in both stages, 45% should be possible, maybe 45,5% with a larger rocket profiting from scale efficiencies. But I don't see 1.0.2's 55% as possible in any way.

Here is what such a larger rocket would look like:

4 full ore tanks, large reaction wheel instead of small, X-200 32 and X-200 16 instead of C7 adapter and FLT-400, Skipper instead of Aerospike, and 8 boosters instead of 2. Delta-v and TWR numbers all look the same, and payload fraction is 45,28%. But I'm not going to launch it, because it has 84 parts and it would take hours to reach orbit.

Edited June 25, 2015 by rocx

[Slugy]

Well that took long. Congrats guys! I honestly didn't think 40% single-stage was doable, so double kudos to our new champion. There can't be much more room for improvement now...

Rune. I have just poked a bear, haven't I?

Cheers, one of the biggest problems was actually getting enough speed to take off (really needed all the runway, and a bit more), even the 5 rapiers are enough for the main atmospheric part of the ascent, although a bit underpowered once in rocket mode. Also tried one turbojet on the back, but that really lacked once the air ran out. I'm pretty sure that it could have a slightly better payload fraction with a little more cargo and a better ascent.

More wings seems to be a viable approach - how things change!

[Red Iron Crown]

Awesome entry, rocx! Brilliant to use the rocket for a few moments at liftoff to get the rocket moving fast enough for the RAPIERs to become more effective, I'm adding that to my bag of tricks.

I've also found the newly buffed aerospike effective, here's a multistage rocket entry (easy to be first when you're the only entry on that board):

Name: Ore Really

Type: Asparagus staged rocket

Delta-V Total: 3011m/s ASL, 3492m/s vacuum

Mass: 63,862kg total, 14,300kg payload in LKO

Payload Fraction: 22.39%

Craft file: Ore Really.craft

Imgur Album:

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[Rune]

Well if I can't be first in one board, I can steal someone's thunder in another, if only temporarily . I feel like this was more of a piloting/luck thing than anything else, though... I finished the gravity turn, and I know it was a gravity turn because the autopilot was on prograde since I ditched the second pair of boosters... on a 72x38 suborbital trajectory, at 54 kms. The boring part was to wait until I got out of atmo with the probe off to save power. You can't deny it has a sweet thrust curve, though (separatrons on launch is a great idea!). If I compute correctly, 19.94/89.94=22.17%. Just enough.

Cheers, one of the biggest problems was actually getting enough speed to take off (really needed all the runway, and a bit more), even the 5 rapiers are enough for the main atmospheric part of the ascent, although a bit underpowered once in rocket mode. Also tried one turbojet on the back, but that really lacked once the air ran out. I'm pretty sure that it could have a slightly better payload fraction with a little more cargo and a better ascent.

More wings seems to be a viable approach - how things change!

Yup, just like in real life, wings let you "cheat" physics, and low TWRs give awesome tankage fractions. A worthy example of physics!

Rune. Basically wings nullify a great % of the gravity losses.

[Red Iron Crown]

Sweet, another rocket entry! Added it to the leaderboard, Rune, though I feel I must point out it wasn't quite enough to bump me down. I may need to preemptively see if I can tweak a few more hundredths of a percent from my design in anticipation of you doing the same.

[Rune]

Sweet, another rocket entry! Added it to the leaderboard, Rune, though I feel I must point out it wasn't quite enough to bump me down. I may need to preemptively see if I can tweak a few more hundredths of a percent from my design in anticipation of you doing the same.

It wasn't? Seemed to remember you did 20... then don't worry, I did it once, and once is enough. Not really doing it for the score!

[Nao]

Weee above 50% in almost SSTO (gear is left on ground, rest is on one stage) ... 9.187/18.263*100 = 50.3% There is little bit more performance left in the design, probably up to 51% ... Although it's kind of boring with Rapiers being so good that staging anything except for used fuel tanks does not really bring improvements.

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[Red Iron Crown]

Impressive, Nao! I wasn't sure such things were still possible, added you to the top of the board. I have to call it multistage, though, even if it is barely so.

You have any pics from your ascent, or a description of it? I'm really curious about what profile you used as my planes can't get anywhere near that.

[Nao]

@Red Iron Crown. It was nothing special, kind of like with real planes: accelerate in level flight, ascent, parabolic flight to the edge of space, then accelerate in level again (~18km) and ascent again into space on rockets.

I happen to record that flight for whatever reason... didn't cut it but it's speed up 4x. https://youtu.be/WSpq6iMHLus (ps: o god, i was thinking takeoff engine sounds at 4x were funny... but after that the high speed screach is bad haha, better switch off sound completely).

[BigFatStupidHead]

Here's my rocket. Not a great payload fraction, but it IS a fully reusable SSTO.

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Payload is (36.6 / 305.48 * 100), roughly 12%

Edited June 25, 2015 by BigFatStupidHead
Learning to Imgur. I is smrt.

[rocx]

Aw man, I worked so hard on my assisted launch technique, and turns out it can be beaten with wings that easily... congratulations Nao, I will try to beat your record next!

[Slugy]

@Red Iron Crown. It was nothing special, kind of like with real planes: accelerate in level flight, ascent, parabolic flight to the edge of space, then accelerate in level again (~18km) and ascent again into space on rockets.

I happen to record that flight for whatever reason... didn't cut it but it's speed up 4x. https://youtu.be/WSpq6iMHLus (ps: o god, i was thinking takeoff engine sounds at 4x were funny... but after that the high speed screach is bad haha, better switch off sound completely).

Really nice, amazing speed in the atmosphere.

I was just building a similar sort of thing - but mine wasn't going to break 50% ...