Stock Payload Fraction Challenge: 1.0.5 Edition

[mightyhuhn]

here a proper video from "the struggle"

and the craft http://kerbalx.com/freehuhn/the-struggle

[antbin]

mightyhuhn, nice SSTO and nice piloting (lol at gear down mach 5). Two questions: Why the round intakes, and why the pre-cooler?

[mightyhuhn]

Why the round intakes

they don't explode that's the major reason and that's why there are 2. ram like to explode.

i know the rounds only have 1900 and the ram 2100 but still the rams over heat faster in my tests.

and why the pre-cooler?

i needed more fuel and i'm using air breathing for a long time.

[cybersol]

I present Jeb's Ore Truck. It weighed 433.35 t on the pad and separated a 113.35 t payload, for a payload score of 26.16%. It's a fairly conventional 3-stage asparagus LFO rocket with decreasing fuel fraction per stage. The photo album is here:

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Cheers,

CyberSoul

EDIT: Just saw the rule about reaction wheels and batteries. When I move those to the lifter I drop to 113.10/433.35 = 26.10%.

Edited April 30, 2015 by cybersol

[Red Iron Crown]

I've updated the leaderboard with metaphor's and cybersol's entries. Metaphor, did you have a name for your rocket?

zekes, that's an impressive rocket but I'm afraid there is too much clipping used to be acceptable as an entry for this particular challenge.

[KerikBalm]

Well, Yesterday I tried and failed to get to orbit using a modified design....

This was the original payload with a legit 22% fraction, but got to orbit with over 90 tons of fuel left... which if that got shifted to the payload, would put my fraction over 40%

The fairing is pretty wide, so I thought I'd use Ore tanks for a more compact mass, and a narrower payload -> less drag -> higher fraction.

Anticipating a higher fraction, I made the ore tank payload 206 tons instead of 202 as was the excess mass in the previous design.

I also substituted the one large battery for multiple massless batteries, removed some reaction wheels, used AV-8R tailfins instead of the large shuttle style tail fins... removed the monoprop, removed the front shielded docking port and replaced with a lighter nose cone... etc... I was expecting to smash the record and maybe get to 45%...

It was going good initially:

These sort of things happen on every attempt:

No big deal... since it can be an expendable launcher.

But whats that with the overheat thing on the payload fairing?

Uhhh... what just happened... where is my ore in the resources display?

Bye bye payload!

After multiple attempts, my payload fairing keeps overheating and exploding, causing the payload to fall off (as its designed to not affect the CG, the rest of the plane can get to orbit). I can't get the same speed and climb rate on jets as I could with the old payload - even though the paylaod is narrower!!!

If I climb higher to avoid overheat, then I lose too much thrust, and don't reach the same speed, and am no longer climbing.

If I don't, the fairing overheats, and I lose the payload.

I did manage to get a perapsis above ground, but repeated attempts failed to achieve orbit. I also have some problems with the right liquid fuel-oxidizer ratio.

I determined that my old payload is a much better heat sink... with multiple parts, there is a heat gradient... the part closest to the fairing is much hotter than the part where the end of an orange tank would be... and it only dumps heat into the next part.

In contrast, the old design has an orange tank that is dumping its heat into 3 adjacent parts (2 orange tank equivalents). It heats up much slower than the ore can immediately adjacent to the docking port+fairing base.

So... while the payload seems to be inert.... its heat conduction properties are actually very important (in some cases, after payload separation, then the Mk3 cockpit would overheat and explode, so the payload may also be involved in stabilizing the heat of the cockpit - although that may simply be due to the sudden acceeration that results from dumping 206 tons of payload - note I had the probe core in the utility bay behind the cockpit, so I could still fly the plane for a while longer).

I'm sure if I go back to the original payload + fairing, and slap on even more fuel tanks as I previously described.

***But that raises the question... is the payload still considered inert if its heat sink qualities are very important? ***

I also note that its not as useful as I thought, as any sensitive equipment on the payload like batteries and solar panels will likely be fried by the heat, despite the protective fairing.

I'm also considering ways to get it narrower, and making the payload stick back more... and taking the 90 tons of fuel out of the rear tanks in the spaceplane rather than the mid tanks, it will be an even better heat sink... and I should be able to demonstrate a >40% payload fraction...

If I just make the ore tank payload longer, I can make it so the fairing doesn't splay outward at all... that might fix the heating problem.

I'll have to see if I can still make it balance

I'm sure one could get even better results by decoupling the jets after flameout, decoupling the wings after 32k or so.... but then you need to use more space-tape (struts), part count goes up... maybe heat conduction problems go up... etc.

I didn't set out to explicitely get a high payload fraction... but I'm absolutely sure that over 40% is possible....

It seems you just need the right payload

Edited May 1, 2015 by KerikBalm

[mightyhuhn]

your math doesn't make any sense too me can you share the craft?

i mean the dry plane should be at about 120-220 tons. so how to get a fraction of 40 % with a small payload of 202/206 ton?

[Radam]

Well, Yesterday I tried and failed to get to orbit using a modified design....

I suggest you put the fairing base between 2 mk3 tanks.

[Red Iron Crown]

***But that raises the question... is the payload still considered inert if its heat sink qualities are very important? ***

That's a good question, and one that didn't matter in previous versions. Given that we don't really have a way to control heat flow well enough to ensure it doesn't get in the payload, I don't see a way for a reasonable rule to prevent it so I'll say that using the payload as a heat sink is fair game.

Fascinating post, KerikBalm, it is exactly this kind of discussion of refining the ascent and spacecraft that I was looking for when I started this thread. Keep it up!

[Radam]

While trying to make a rapier powered SSTO, I realised all I could do at max thrust is hover:

For some reason this exact craft prevents me from reverting back to launch, VAB or even just space center.

Edited May 1, 2015 by Radam

[Maelstrom Vortex]

- - - Updated - - -

I finally pulled it off. MASSIVE SSTO that carries an equally massive payload. Warning, be very gentle. Would someone care to run the numbers for me?

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Craft FileD

Depending on random physics loads, you might have to reload it a few times due to weight.

Flight profile instructions:

Careful off runway, do not tilt up til you are in air off the runway. Tilt up slowly to 30 degree up ascent to around 8000 feet and begin to level towards horizon with orbit indicator 5-10 degrees off horizon. Accelerate til over 1000 m/s continuing to ascend until the rocket motors kick in on their own, tilt nose up to 45 degree ascent til apoapsis is around 40,000 meters. Level back out. Accelerate until orbit encircles planet and periapsis turns to apoapsis on the other side. You MAY lose your flaps due to heat. This is okay, you will still be fully in control of the craft due to the tail surface controls and it will still be very controllable on re-entry.

On re-entry.. open drogue shutes if you want to use them to slow descent. I recommend if you do this you do set up an action group to cut them as I honestly have not needed them yet on re-entry. If you wish to do a glide descent, first burn of speed to a shallow re-entry path and keep your nose pitched up 10 degrees as you enter the atmosphere to bleed speed. Eventually it will return to flying like a normal aircraft. Clearance and absorption granted by the landing gear should make for relatively easy landings.

Edited May 1, 2015 by Maelstrom Vortex

[mightyhuhn]

i just broke the record by a little bit... :

http://abload.de/img/challengev31iyut8.png

http://abload.de/img/challengev32gluxd.png

http://abload.de/img/challengev33ybuaf.png

http://abload.de/img/challengev3418uir.png

http://abload.de/img/challengev35spucm.png

i messed most of the screns up but it is.

100/9.53*4.6=48.26862539349423

i'm going to make a video.

f5 saved it:

http://abload.de/img/challengev3new126u84.png

http://abload.de/img/challengev3new2npuoy.png

Edited May 1, 2015 by mightyhuhn

[Red Iron Crown]

Maelstrom Vortex, I'd be happy to calculate your payload fraction, I would just need you to provide a screenshot of map view with the vessel info window open when sitting on the runway or pad, as well as another similar one with the payload separated and focused in orbit.

[Maelstrom Vortex]

Maelstrom Vortex, I'd be happy to calculate your payload fraction, I would just need you to provide a screenshot of map view with the vessel info window open when sitting on the runway or pad, as well as another similar one with the payload separated and focused in orbit.

Added to imgur follio as images 6,7,8,9,10. Sadly the payload is just a little drone which is detatchable. The primary payload is two copies of every scientific instrument, a global mineral scanner, a metal drill, an ore container, an ore refinery, a pair of fuel cells, a fairing covering a linear docking port and an asteroid grabber. It also has a tourist section.. this thing.. has a massive, non-separable pay load, lol. I'll take all the extra junk off and try to do a dead lift of nothing but fuel later tonight or this weekend in the cargo bay.. buhahaha.

Image 4 and image 1 on the imgur list.

I think my boeing sized SSTO has proven space plane sstos are not dead by any stretch of the imagination, lol.

Edited May 1, 2015 by Maelstrom Vortex

[mightyhuhn]

@Maelstrom Vortex

it's

ion= 2.37

the rest is not on a decoupler or docking point. so in term of the rules it would be

100/185.59*2.37= 1.277008459507517%

just remove everything in the cargo and repleace it with something sticking to a decoupler or docking node, deactived every fuel in it and fly in in orbit.

BTW. your ISRU is not centered correctly.

[Red Iron Crown]

Maelstrom Vortex, I would suggest you rework what's in the cargo bay to maximize you payload fraction, I think your plane could do much better if it dropped more payload in orbit. I'll hold off on adding you to the list until you decide what you're doing.

mightyhuhn, that's an impressive fraction! I'll add it to the leaderboard.

[mightyhuhn]

just to make sure i didn't break any rules.

the nose cone is a heat shield with 0 ablator so just a structure part with over 3000 heat resistence.

[Red Iron Crown]

That's legit. Payloads are often at the nose of rockets, finding a way to avoid overheating is fair game (it would have been fine to have ablator there, even).

[mightyhuhn]

but that's the trick. ablator has mass.

i could spare a declocker by using the payload with the heat shield but that simply feels wrong.

[Red Iron Crown]

Sure, and if the ablator burns off before reaching orbit that would reduce payload mass. Not really seeing a problem with it.

[mightyhuhn]

for it's breaking this rule.

- Payload must be inert and contribute nothing but incidental body lift and command authority to the lifter (crewed pod or probe core is ok). All reaction wheels, batteries and fuel tanks in the payload must be disabled via tweakables.

[Red Iron Crown]

If the ablator is burned off, it doesn't contribute to payload mass. I'm not going to be a stickler about using something on the nose of the payload to prevent it from exploding, that's not what that rule is designed to prevent.

[KerikBalm]

Congratulations... you've beat my theoritical score.

Those runs take a lot of time because my computer can't handle it so well. A 6 minute flight according to the game time really takes me like 20 minutes.

Quick saving in flight often leads to disasters... trying to optimize the flight profile over and over uses a lot of time... then I change the design... etc.

I didn't even build mine for this challenge, but rather just to try and make an SSTO that can get a large payload to orbit (large in mass or volume).

Incidentally, I didn't want part count to go too high, which is probably how it ended up being so competitive (reduce part count, reduce mass)

I accomplished that, so I'm happy. This challenge did make me realize the limits to my SSTO... The really heavy payloads at the limit of its capabilities need to be good heat conductors or long and thin.

I still think I may be able to get it to orbit with the right ascent profile... judging by that one screenshot where it is at 21km and 1,275 m/s before the fairing overheated (nothing else had at that point).

Still.. when I load that thing up to its limit... the payload fairing starts to cook... even more parts in the utility bay cookoff... etc.

I also realized its TWR with the KR-2Ls is not good enough with a full payload... its good enough if I can get a decent climb rate and above 1,300 km on jets alone, but when I'm forced to do a steeper climb on jets to avoid overheating, followed by a shallower acceleration up to speed, the KR-2Ls don't have as much oomph to get it climbing again as I would like... I think I lose a lot due to resistance and gravity drag. If I hook up fuel lines to all the rapiers to allow them to suck oxidizer (can they still suck liquid fuel like a jet, when in rocket mode?)

Then with 28 rapiers going (I forget if the stats changed)... I'll more than double my TWR, which may overcome the lower Isp if I just use them to get up past ~32-35km.

I think for my own purposes, I'll "certify" the design for 150 tons of payload...

Sure, and if the ablator burns off before reaching orbit that would reduce payload mass. Not really seeing a problem with it.

Well... then the heat shield is like a fuel tank.... ablator instead of fuel.

Or maybe its like the decoupler rule.

Sure, for now, heat shields are massless... but if it was on the payload loaded with ablator, it was serving a much more direct function than a heat sink.

As such, I'd think he'd have to include a way to decouple it from the payload. One more decoupler would drop the mass fraction a bit.

But with no ablator in it... its just a heat sink... which is a similar situation to my design....

It seems that as designs start to push into the 40-50% range, heating concerns start to cause some "gray areas"

Edited May 1, 2015 by KerikBalm

[mightyhuhn]

currently i decouple it.

[Radam]

Fairings are now properly heavy.