Stock Payload Fraction Challenge: 1.0.5 Edition

[Nao]

Nice Nefrums . Although with two small tweaks to the craft, that configuration can go above 52% hehe...

[Nefrums]

Thanks. There is always room for more improvements. What where the tweaks you where thinking about?

Here is a slightly bigger ship:

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28.48%

[Nao]

Thanks. There is always room for more improvements. What where the tweaks you where thinking about?

Here is a slightly bigger ship:

http://imgur.com/a/LvCAv

28.48%

Ohhh so thats how this cookie crumbles! I'll show you the tweaks... right with some percentages to boot! soon

[Red Iron Crown]

Added you to the top of the other board, Nefrums, congrats on topping both! (For the moment, how long can it last?)

[Nefrums]

How is it going Nao?

In the meantime I have made this design with twin Rapiers and an Aerospike:

Stingray mk1:

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52,52%

[Red Iron Crown]

The top spot keeps creeping higher and higher (and I can see that design could eke out a bit more by tweaking fuel and using docking ports rather than decouplers). Well done, Nefrums, added to the board.

[Rune]

Wow, this keeps going up?

Rune. Guys, seriously, physics called, it wants its rules back.

[Nao]

How is it going Nao?

As you can see (the empty space instead of my posts) not so great , made 2 crafts with fun and useful configuration, both ended up having phantom forces, and then life knocked on the door ~~

But to answer your previous question, the two tweaks to the 51% craft would be to drop the radial intake (the RAPIERspike actually gives enough air to fly) and to angle the wings up by 5degrees - due to how drag for wings works a bit differently, you get roughly the same drag but a significant increase to lift for most part of the flight increasing efficiency of both early ascent with less drag on rest of the craft for the same lift and for the rocket flight as the additional lift allows for keeping vertical velocity high without excessive attitude tilt over prograde.

Nice craft thou! I was using similar configuration but with LV-909 instead of Aerospike. Spike has only a tiny bit more TWR, while 909 is lighter by 0.5t, and provides better ISP. And considering the last "rocket only" push is so short deltaV wise, only 909 was mass effective, in my calculations, when compared to just bringing more fuel for RAPIERs. (Funnily enough i have used the same main wings as you in the same configuration)

But in the end during tests payload was only ~52% so idk (with a 2.5m fairing thou)... Now i kind of want to wait for next version and fixes...:/ Anyways congrats again!

[Nich]

I am absolutely loving the Big S wing I even used it on a 10t craft and it did just as well as a tiny wing. I would have thought too much drag and weight for a single rapier but its L/D must be good enough to make up for the extra weight.

[Val]

Here's my entry. I hope it's valid, cause I put a lot of time into it

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GTOW: 307.74 t

Payload: 136.8 t (8x Full Ore Cannisters + 16x Struts?)

That should give a payload fraction of 44.45%

It's a single stage spaceplane. The C-1 Payday Mk.4 (Craft file). Flown using pitch input to MechJeb's Smart A.S.S.

Engine layout 12 RAPIERs and 6 Nervas.

Liquid Fuel Capacity 13510.

Oxidizer Capacity 4510.

122 Parts including cargo (24 Parts)

[Red Iron Crown]

Looks legit to me, Val, and a new high water mark for single stage designs! Great entry and very detailed report of the ascent, added to the leaderboard.

[Val]

Looks legit to me, Val, and a new high water mark for single stage designs! Great entry and very detailed report of the ascent, added to the leaderboard.

Woohoo, I'm on a leaderboard I've never been that before. Thanks

[Val]

Had to try again. This time with a multistage rocket entry.

But I ended up with the wrong kind of efficient, at least for this challenge.

But I'll go ahead an submit it anyway, since I thought it was interesting and I won't be last on the leader board (also I'm not thaaat far behind the serious ones).

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265.323 t Rocket.

51 t payload (3 full Large Holding Tanks)

19.22 % Payload Fraction.

Edit: Craft file

Edited August 9, 2015 by Val
Craft file

[Red Iron Crown]

That entry may not place highly by the scoring metric for this challenge, Val, but it's the first Kerbin ascent I've seen done with less than 3km/s of delta-V. I didn't think that was possible, and had you submitted pics instead of video I would have been very suspicious but it looks completely legit in the video. Well done, and I've added you to the board.

Edited August 9, 2015 by Red Iron Crown

[Val]

That entry may not place highly by the scoring metric for this challenge, Val, but it's the first Kerbin ascent I've seen done with less than 3km/s of delta-V. I didn't think that was possible, and had you submitted pics instead of video I would have been very suspicious but it looks completely legit in the vdeio. Well done, and I've added you to the board.

Too be honest, I was a little surprised myself, since that was not what I was going for.

I'd very much like if someone could test my craft and replicate it.

The launch profile I used is as simple as:

1. Full throttle, Stage, turn immediately to 25 degrees above horizon.
   
2. Stage 2 times when first stage runs out. (Seperation and engine ignition is staggered or the whole rocket may explode)
   
3. Keep at 25 degrees.
   
4. When AP >60 km turn prograde.
   
5. When AP >70 km Throttle down.
   
6. Stage when above 50 km to shed fairing.
   
7. Circularize at AP.
   

Edit: Sorry, if this is considered derailment. Should I have created my own thread for this?

Edited August 9, 2015 by Val

[Red Iron Crown]

It seems to have some excess dV, I was able to put it into a 74x136km orbit with the fuel provided (though it took several tries, that pitch maneuver at launch is critical and I'm not as smooth as MJ). I'm not sure if MJ and KER are making an error in calculating dV or if this ascent profile is particularly efficient but I suspect the latter.

Don't worry about derailment, it's this sort of interesting result that is the best thing about challenges (and we're discussing your entry anyway ).

[Jouni]

I'm not sure if MJ and KER are making an error in calculating dV or if this ascent profile is particularly efficient but I suspect the latter.

There is something strange with the MechJeb/KER displays. MechJeb sees a heavier rocket than KER, and I'm not sure which one is right.

I had similar issues with MechJeb earlier in the challenge. I thought I had broken the 29% barrier, but it turned out to be a MechJeb error, and the real payload fraction was below 28%.

[Red Iron Crown]

Indeed. MJ is showing 2999m/s of vacuum dV for Val's rocket on the pad, KER gives me 3067m/s of vacuum dV in the VAB.

Either way that's an extremely dV-efficient ascent. I think it is the reduced gravity losses from going mostly horizontal nearly immediately more than offsetting the additional drag losses from the wings and greater time in atmosphere.

[Val]

...

I think it is the reduced gravity losses from going mostly horizontal nearly immediately more than offsetting the additional drag losses from the wings and greater time in atmosphere.

Yes, the wings are supposed to reduce gravity losses, by allowing a near horizontal flight path, similarly to a very high TWR gravity turn on an airless body.

My idea was that this would allow me to reduce fuel mass, proportionally to the amount usually used to lift the rocket vertically for the first part of the ascent. Which is usually where most of the fuel mass is spent, boosters and all considered. If that had worked as I thought it would, it should have meant a massive improvement in payload fraction.

But instead it, mostly, just reduced the total dV expenditure. Which I guess makes sense, since it does reduce gravity losses.

[Val]

I improved the payload fraction of my Rocket Flyer.

The Mk.8 is now up to 324.15 t.

Payload is 68 t.

Craft file

Payload fraction 20.98 %

I'm catching up

dV usage also above 3000 m/s now, though not by much.

Imgur is being difficult, so only video atm.

Edit: Imgur is feeling better now.

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Edit 2: And I only just noticed I have unbalanced amounts of LF and O. I'll have to redo this one.

Edited August 11, 2015 by Val
Facepalm

[Red Iron Crown]

Added that entry as is for now, Val, if you update it please bump the thread so I see it and I'll update. Why do I have the feeling you'll keep refining until you are near the top of the board?

[Val]

Added that entry as is for now, Val, if you update it please bump the thread so I see it and I'll update. Why do I have the feeling you'll keep refining until you are near the top of the board?

Hehe. I am planning to do one more round of optimizations for one last entry in this category, but it'll be later in the week. Won't have time for KSP at least for a few days.

[wolfman29]

Alright. First time posting, just got the game a few weeks ago. But by my calculations, even though I don't make #1 on the list of rocket-based payloads to orbit, am lifting the largest payload to orbit by any of the people on the top list by far! My payload is bigger than most of the rockets on the list!

Anyway, here's pictures.

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Also, I had enough fuel to spare to deorbit it (I have about 5.3k units of liquid fuel left). While I don't think I could have lifted more (I barely made it up as it is), I think that if I optimized the rocket a bit more (reducing the size of my ejection engines would help a bit), I think I could get away with up to 25% efficiency.

By the way - I've never seen anyone use the ejection engines that I am before. The reason I am using real engines instead of only sepratrons (I am using sepratrons, but not only those) is because I need a big enough kick-back from the main stack due to the length. If I just used sepratrons, the thrust on those isn't enough to move then quickly enough, especially when I am accelerating or turning (see image 6).

Hope you guys like it!

[Red Iron Crown]

Welcome aboard, wolfman29! That is one giant rocket, does it have a name?

That's certainly on the larger side of separation motors, do they overheat if you don't put them in a fairing?

[wolfman29]

Thanks for the welcome. Really enjoying the game!

Well, currently it's name is Heaviest Lifter 5 (not very creative - wasn't sure if it was going to be the finished product or not). I guess it deserves a name though. How about... Juggernaut 5?

As for the separation motors - I put them in fairing if only to decrease drag. I never tested this specific rocket without the fairings (I've been using those for big rockets for a while now), but I seem to get better results with than without. And I think someone did a pretty comprehensive review of the aerodynamics in 1.0.4 and found that just about anything significantly beats a rocket whose top is naked, including a pointy fairing.

However! I actually made a small change to it and managed to bump up it's payload fraction by a few percentage points. That extra fuel I had just lying around? Well, I removed that and replaced it with an equal amount in the payload. Here are the pictures for that.

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For those who don't want to scroll through imgur and look at the high-res screencaps, the numbers are the following.

Launch mass: 2436.05 tons

Payload mass: 612.125 tons

Payload fraction: 25.13%

Definitely better than before, and even then I still had about 20 tons of fuel left over! I could bump it up a bit if I wanted to, but it's a long flight because of the high part-count, and I also have to pay a lot of attention, even if I do fly on autopilot (sorry guys, I'm not so great of a pilot myself!).