Help in making a really powerful first stage, aka Mah tank is too big!

[Guest Aaack]

Hi guys!

So I made a Mün landing but went kinda wrong and my poor kerbal in it's mercury capsule is stranded there.

I want to rescue him, for that the first stage will be put in Kerbin orbit a refuel station, then in Mün orbit another station and finally a shuttle service from / to stations and a reusable lander from/ to the mün.

Ah! right, also rescue the poor kerbal in the future...

Anywaysss

My idea is to simply put two orange tanks in Kerbin orbit. that happens to have all the docking ports available just for the lulz.

The tanks are isolated from the rockets that will put them in orbit, so basically ill have to deal with the weight of two full tanks at all time.

My first experiment was put one orange tank on top of the other, which made almost impossible to control it. Now i made a tandem configuration:

Underneath I added decouplers and more tanks with huge engines to lift that off.

Which works! but... it's not enough, that would be a great second stage, I need a first one and so far I didn't find any alternative.

So the first cry for help would be: Can you throw me an idea to lift this monstrosity at least to 50k mts?

Also the second and weird thing that happens is once i decouple both main engines the thing start to spin out of control, the separated tanks spins like crazy too, its weird. I made sure to make the thing as symmetrical as possible, so I'm not sure if it's the design or a bug?

the second cry for help would be: Have you dealt with weird rotational momentum lately?

Thanks in advance!

Edit: I just read about the difference between SAS and ASAS... Ill work on that to kill the weird rotation, probably adding an empty module... more weight

Edited June 29, 2013 by Aaack

[Tank Buddy]

First of all, 2 orange tanks is way overkill. One is hard enough. Second, that first stage has the equivalent Delta V of the boosters of my heavy lifter. You need to use asparagus staging and limit yourself to 2880 liters of fuel total. That's one orange tank. I would recommend one orange tank, then have a skipper for an orbital insertion, then have some mainsails and SRB's for the lift off stage. I can send you the craft file for one of my Munar rescues. It was actually to rescue poor Jeb, who then immediately got sent back down to the moon! My craft requires no refueling and has plenty of fuel. Just let me know and I will e-mail it to you or however you like. Bueno Suerte!

[7499275]

I am not the best launching odd shaped things or large things into orbit so... For the 2nd part... The "Weird rotational momentum"

Try taking away the control surfaces and using just engine gimbal to manuever your rocket. Or... if your a cheater turn on infinte RCS and use RCS and ASAS to cancel the rotation.

Another option would be adding more control surfaces in the right places. Where are the right places you may ask? Well I do not know that part either. Hope my limited information helped you some!

regards 74

[Guest Aaack]

Hey 74, thanks for the ideas, I don't want to cheat, so no infinite RCS, however... the problem of spinning actually aggravates when I turn the RCSs on!

So far if I turn the ASAS off and try to fly it manually (while it falls like a rock to Kerbin again surrounded by fire), I have better results than if I turn on ASAS+RCSs

I will try getting rid of the extra ASAS I set up, get rid of the control surfaces and see what happens... Thanks for the idea!

[Bioman222]

MOAR BOOSTARS

Though seriosly, add a few boosters to that first stage and you should be set!

[capi3101]

Okay...so your payload is roughly eighty tonnes from the look of it.

Temstar's got an excellent post that talks specifically about how to make asparagus staged rockets. In it, he tells you to assume that your payload fraction is going to be about 15% of the total mass of your rocket and to shoot for a first stage TWR of 1.6 to 1.7.

So you've got eighty tonnes...80*(100/15) = 533.33 tonnes.

533.33 * 9.81 * 1.6 = 8,371.2

533.33 * 9.81 * 1.7 = 8,894.4

So you want your thrust at liftoff to be somewhere between 8371.2 and 8894.4 kN.

Actually, with a little bit of redesign, there's not much reason why you couldn't use the Zenith IX or Nova booster to lift that. I suppose if you're wanting to put that in Munar orbit you'll need to do some work (the boosters are designed for 75k circular Kerbin orbits only). Still this might give you a good place to begin.

When the spin starts, warp time. When you go back to 1x, does it start spinning again?

Ninja'd at least six different ways...

[Horn Brain]

That thing needs about 12 more orange tanks with mainsails/skippers on them, all asparagus staged, if you even want to smell space. I can lift an orange tank and a little extra payload nearly fully fueled to orbit with 6 orange tanks of asparagus boosters and a core stage not too different from the ones you've got beneath each of your intended payloads, so that's probably a good ballpark figure of how much you're lacking.

You might try running a fuel line from the payload to the boosters, then dumping them (transfer forward all remaining fuel first) just before you reach orbit and adding a few of the tiny radial engines to the payload to perform the circularization. Then you can send up more reasonable tankers to refuel your station.

Launching two orange tanks into orbit is approaching the limits of what the game can handle on a regular machine.

[Johnno]

I'd advice you to start small. Figure out how to send one tank into orbit, then dock two together (around potentially a manned core with a hitchhiker storage or two). You're looking at sending about 80 tons up to orbit in one go, you'd need in the neighbourhood of 14 red tanks worth of fuel and buncha mainsails to get that done in one go.

As for your design two red tanks is the same as one red tank and 4 rockomax x200-16 tanks. It would be easier to build a single core rocket with the red tank on top and the 4 smaller white ones around it in symmetry.

[Guest Aaack]

Hi Tank, thanks for reply!

Well Yep, I know, it's horribly exaggerated--- Exactly the way I like it!

I made an asparagus setup using the same engine/tanks of the screenshot, it took me out to orbit but it was impossible to have the DV enough to set an orbit, it was more like an Up / Down - Ka-boom trip.

let me show you:

I even added SRBs to have an extra push up there, but it made it spiral completely out of control, perhaps now I know what's the difference between ASAS and SAS I could revise this design...

The reason why I want to put two oranges up there is to avoid do two trips and try to rendez vous such mass being a noob as I am.

[Guest Aaack]

Hi Bioman, thank you!

Actually I tried that at first, (see the reply to Tank), it was enough to put me at 80k mts.

However that was all i could do, without any fuel left to made an orbit (I needed something like 12 minutes at full burn to made the crappiest orbit ever)... I know this is crazily exaggerated, perhaps thats why it's so fun to try XD

[Guest Aaack]

Hi Capi!

Tank you very much for the number crunching !

Well I'll have to check the Zenith and the Nova, because I don't know them, but this is the Kerbin orbit fuel station, I don't pretend to send it to the Mün at all, Ill try the warp trick (I saw it in you tube) and post results!

[Guest Aaack]

Hey Horn!

Launching two orange tanks into orbit is approaching the limits of what the game can handle on a regular machine.

You mean lag? or just the limit of calculation? I launched something bigger as the first prototype of this thing and didn't had lag at all.

Granted, I basically wipe all the debris so my game is not tracking anything at all, but my rig is not new and it runs pretty well.

I want to keep the fuel on that payload intact, however Ill do a 12 aparagus setup and try to launch it just for laughs, it sounds so crazy and over the top I love it

[Guest Aaack]

Hi Johnno, thanks for the suggestion!

Actually that's my plan B, I got basically the same answer from most of you.

Ill try to do a behemoth of a rocket and if that doesnt work (which I'm pretty sure it wont) Ill just mod the first prototype to carry 1 tank and see what happens.

I think at least Ill have good and funny screenshots, thank you very much for the advice!

[Guest Aaack]

So that it's getting fun. I almost made it.

I had two oustanding issues, but first let me show you what i did.

It's basically two tanks, one top of the other, with an asparagus config with 12 mainsails and one central also with the same config that pushes the tanks....

The design itself is challenging because the outer ring basically holds the weight of the whole rocket so there's never enough strut connectors, in fact the first model just collapsed under it's own weight!

3... 2... 1...

yeah... humm...

actually after reinforcing everything I managed to lift off...

...to suffer a horrible structural failure that causes the last stage of the outer ring to crash into the inner ring and make everything blow away

Third and forth try was a disaster too...

So in order to make thing symmetrical I started to tend struts in 3 pieces from the booster to the central body, I couldn't strut from booster to booster because the separation makes it tioo unstable and wobbly, usually making it explode. So every strut goes to the central body in a radial configuration. It's a nightmare to build but ... I made it.

...And found that the spinning is worse than ever.

When just 2 boosters on the outer ring remains the spinning is so fast it stabilizes right up making impossible to make any maneuver...

so I got this:

Which allowed me to deploy everything as if it were in orbit!

and make spectacularly firey re-entries...

Last one I discovered that cutting engines and stabilizing things manually works, BUT takes like for ever and that doesn't gives time to use the little fuel i have left to make an orbit...

It's the mass of the whole thing, but in spite of being very symmetrical the issue with the rotation is terrible, even using the SRBs.

This was my last try:

For whom advised GO SMALLER YOU ANIMAL! well you're right guys.

But I'll keep trying for the lulz and because I don't have brain left today to sit at the editor again.

I'll post more results, if you have any advise, please I'm all ears.

I'll leave you with the toughest solar panels I ever saw surviving almost the whole re-entry.

[Guest Aaack]

Success!

Thank you guys for the ideas and numbers! It would take me for EVER to guess all that by myself (I'm not good at numbers, Jim, I'm a graphic designer!).

So... here's what I did:

A problem I had before is that in order to make the ubercluster of boosters I needed to add a structural strut at the bottom of the central rocket and attach there the decouplers that would hold the exterior ring of tanks/engines. Everything was nice until I started to decouple the interior ring... they would collide against the struts!

The bloody thing is so reinforced that that didn't destroy it but it usually add chaos to my already chaotic spinning, so...

I added decouplers to the struts.

The thing worked like a charm, now the interior tanks just shaved some control surfaces when decoupling... I know, you wouldn't call that a "charm" but if you consider it's a huge mass of wobbliness spinning out of control while trying to get into orbit... well I'm proud of it

So that solved issue #1. Also I had luck and it didn't wobble so hard it broke apart (which happened 2 or 3 times every 10).

And the trick to cut engines to align the thing manually and then let ASAS and the RCSs take charge of keeping it in place while I was burning worked also, I managed to get the station in the ugliest orbit ever, but up there!

After I made sure the tanks weren't about to disintegrate due the stress I planned a correction that would take about 7 seconds burning, to circularize the orbit.

I had just 4 left... and this is the result:

After a VERY slow separation of the last stage...

I managed to put in (an ugly) orbit my tanks!

Now I wonder, how come the last stage actually fell?

Shouldn't be following the station for ever? Why it drifted? The decoupler barely separates the thing, may be it's more powerful than I think?

In any case it's a non tripulated station that basically has an array of antennae, solar panels and light and a silly amount of fuel up there.

Thanks again for all the help!

Edit: Re upload the separation pic that for some reason went boom.

PS: If someone wants the file to play with the monstrosity I've made just ping me, I'm more than happy to share it.

Edited June 29, 2013 by Aaack

[Skorpychan]

Why did you put the RCS tanks spread out like that? I'd have dumped them all at the top, for lower CoM, and so fuel pipes didn't need to be added to bridge them.

Also, needs more lights, and a few RTGs.

[Guest Aaack]

well my first prototype had just ones on one end. but they were way too weak to move the whole thing , I added more just to make it possible to rotate in time, those tanks are full and untouched so the thing is kinda heavy XD

what's CoM? and RTGs?

It has 4 lights on one end, I think they are way too powerful and way too close to the fuselage to be any good but make it bright at redezvous. I'm experimenting with the smaller lights on landing gears to have some robotic directional lights, well see how it works

So that picture... after sweating and almost by miracle put the whole thing in orbit... I ended the flight thinking it was just a "return to the vhicle assembly" option... and lost it.

I just put my station back on orbit, this time with fuel enough to make it really well aligned at 204 Km, in a perfectly circular orbit very very equatorial, Im very proud of it but I want to put more refuel stations now, so if you tell me whats those acronysms i'll probably add them in the new model

Edit: Sorry I misread your message... I can't do speed reading in English XD

Anyway, I did it that way because I was copying Pasting the same tank "module", in order to have the best symmetry possible, I dont mind some fuel lines as long as I have a balanced thing... which I don't but that was my attempt.

Edited June 29, 2013 by Aaack

[Johnno]

Congratulations on getting that thing into orbit Aaack, well done.

CoM = center of mass.

RTG = Radioisotope Thermoelectric Generator (always on electric charge generator supposed to provide power for 'decades').

For lights I would suggest the boxy stock version lights, the landing gear lights are pretty bright too while the boxy lights (illuminator mk2) only really light up your ship with a gentle glow (they don't reach very far either). I use them as docking lights on all my ships.

Also, you don't need the fuel lines to connect tanks that are in the same 'stack'. As long as everything inbetween is fuel crossfeed capable you'll be fine. It's once you start mounting stuff radially (onto the sides of the center stack) that you'll need fuel lines.

Anyhoo, once again, well done.

[Guest Aaack]

Hey Johnno thank you!

Oh I thought that a solar panel array + batteries (im using 4 Z-400 batteries) were enough for the demands of the station (basically a small probe the communication antennae (not sure if needs power) and the lights), Do I need the RTG too?

Bah, no problem Ill add it, I'm redoing the station now, so I'll add a couple of RTGs too, I thought everything needed fuel lines, that's another reason why I set up the RCSs on their own tank too, I don't know, it sounded logical, more like sim city where you have to connect everything by hand haha.

I'll post new pictures as soon as I'm done with the lights and put this one on orbit (I plan to put several and just forget about fuel for a while, while I'm building the Mün base to rescue my Kerbal)

[Johnno]

RTGs aren't really necessary but they're nice to have just to ensure that you have power at all times. With the amount of batteries you have though you should be more than fine. Personally I usually just stick one battery and one RTG on each ship and it's fine, I use solar panels mainly for eyecandy. You can pretty much do the math yourself by looking at the power requirements for things and the power output / battery power amount, a single RTG can power a probecore and a buncha lights just fine nonstop.

[Guest Aaack]

well true... BIG solar panels that moves to face the sun will look always cooler than a beam shaped thingy.

I added two, I think now I have the capacity to recharge other vehicles batteries if necessary, alas I'm not sure if that's possible to do yet.

The lights are quite the challenge, since the docking ports are just below a booster and inmediately upwards there's the SRBs setting up lights it's nearly impossible im still trying to think how Ill pull such stunt...

[Guest Aaack]

Well the new lights are beautiful, no more harsh contrasts (alas the bump map on the orange tanks is beautiful), but a really soft and useful light for the docking ports:

Also I has RTGs now and the whole thing is so wobbly it's scary...

Ill try to put this second and improved flying tank on orbit now, wish me luck

[Skorpychan]

If you add struts, it won't wobble so much. They instantly break under staging conditions, so you can happily strut those SRBs to the tanks, and so forth.

[Guest Aaack]

Hey Skorpy!

Actually it does have struts. But i added decouplers on both sides... I think Ill add more without decouplers and hope they do break completely after the separation...after removing the unnecessary fuel lines it became so wobbly it explodes on lift off...so i really need to fasten the lower boosters somehow and make whatever i use to fasten them to disappear after the exterior ring is detached, leaving the space free for the falling tanks of the inner ring of boosters.

(and this is why I don't have nice things)

[koshelenkovv]

Aaack, you don't need two orange tanks in orbit.

Really, for which sake one can need two huge tanks in space?

But if you just want to have two orange tanks in orbit, deliver them separately and dock.