Tip for lifting super-massive payloads - thrust plate (with video)

[allmhuran]

So, you've finally decided to lift something stupid.

We've all been there. One jumbo in orbit isn't enough. You want two. Then three. Then six.

At some point you simply can't fit enough thrust directly below your payload anymore, so you start building radial stages that aren't directly under the payload (introducing shear stresses).

Then you go even bigger, and even the radial stages need mainsails. And herein lies the problem. The column feeding your radially attached mainsail stack starts to get low on fuel, and therefore very light. Meanwhile there's still a mainsail below it putting out just as much thrust as it did when the column was full. The rest of your payload is still struggling into the sky, but the radial mainsail stack has crazy thrust to weight at this point. The shear forces become too great and your mainsail stack rips off its decoupler. At best, your base of thrust is now asymmetrical and you go spiralling back to Kerbin. At worst, the stack slams into the rest of your rocket and creates a huge chain of explosions.

Wait... maybe the second one was best...

In any case, there is a solution!

Structural I-beams and structural plates are very, very strong. They don't tear apart easily. You can use them to create a "thrust plate". A web of beams and panels that form a nigh-indestructible platform sitting between your payload and the stacks below it, with a big enough diameter to accomodate all of your giant asparagus stages.

Attach your stacks to the bottom of the plate instead of attaching them radially to neighbouring stacks. Now they will never tear off.

For example: this rocket lifts 750 tons (20 orange tanks) into LKO. You can see the web of girders and plates most clearly once it reaches orbit.

[pebble_garden]

Very impressive!

[CodatheSpaceFox]

Quite a feat of ingenuity, I have always been impressed with structural pieces ability to take a lot of stress, but I usually avoided them for their weight. This is very impressive though, and I do believe I'll have to give them a second chance to prove their ability. Thanks for the share, and well done with your launch and design. ^^

[Superfluous J]

Very cool, even though I eyetwitched when you left all that debris in orbit at the end

If I ever need that much fuel (or even if I don't) I will remember this video.

[TouhouTorpedo]

Interesting idea I hadn't considered. I don't asparagus out of principle, but the idea of structural beams to take the primary load instead is an interesting one that could be applied to a normal rocket if well thought out. I normally just do big tall rocket with beams outside, but that has limits. I'll give a structural core instead a shot next time.

[SRV Ron]

Looks like a job for some Novapunch monster boosters. So long as it works, stock design is fine too.

Those solid fuel boosters should be ejected as soon as they burned out to eliminate their dead weight.

[allmhuran]

Those solid fuel boosters should be ejected as soon as they burned out to eliminate their dead weight.

That would mean carrying the decouplers as well, with the extra weight and structural considerations. Since the whole stage is dropped shortly after the boosters run out, there's very little lost by just holding on to them for a couple more seconds, and you don't have to carry the decouplers up (which reduces weight and also means you don't have the extra parts in your part count)

[allmhuran]

Based on requests I've added a construction tutorial video :

[allmhuran]

Quite a feat of ingenuity, I have always been impressed with structural pieces ability to take a lot of stress, but I usually avoided them for their weight. This is very impressive though, and I do believe I'll have to give them a second chance to prove their ability. Thanks for the share, and well done with your launch and design. ^^

Yes, the weight is a problem for smaller rockets. But if you're lifting such huge payloads the percentage of extra weight added by the plate is easily offset by the larger base of thrust you can provide with the additional structural integrity.

[Jarin]

You mention Editor Tools... which seems to be very out of date. Are you using Editor Extensions?

[Tripzter]

Based on requests I've added a construction tutorial video

I shall give you props by liking the vid. Very nice explanation.

[allmhuran]

You mention Editor Tools... which seems to be very out of date. Are you using Editor Extensions?

That's the one!

[Iansoreta]

That's the one!

Is that possible without using editor extension mod? I have so far mods like Novapunch, KAS, and AGM, and I'm currently using KSP 0.23.

[Tahib]

Did some testing. Sorry for reviving, but the overheat tip is genious. maybe a bug?

I'm not entirely sure the thrust plate is the better way to go. My biggest Payload so far was 144 t only 2 struts per asparagus tank.

Test results

a) 1 Strut and TT-70 Radial Decoupler. Not very stable, but does not fall apart. Another Strut at bottom adds a lot more stability. Vessel mass: 381 t, 60 parts

1 Panel, Beam, Strut, Stack Decoupler. Not possible without additional Strut at the Bottom. Bit more stability, more parts too. Vessel mass: 383 t, 79 parts

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Edit: BTSM Mod adds some Weight i think

Edited June 2, 2014 by Tahib

[Norcalplanner]

Thanks so much for the thrust plate tip. I've been using 2x2 plates with longer beams and the ARM Kerbodyne rockets for some truly epic launches. Thanks to the thrust plate, I now have an 850 ton space station in orbit around the Mun. Of course, my part count is too high, so it lags like a sonofagun, but it's still pretty to look at.

[Iansoreta]

This thread is really getting old since someone introduced that concept of thrust plate, however, I never convince anyone to close this thread for the sake of newbies. I'm still using that concept even when using tank and engine of 3 meter size, however, I have aerodynamic plugin named neophyte(basically works like ferram), so it will not work well under realistic aerodynamics without aerodynamic parts. Thrust plates aren't streamlined as well so I avoid that without adding aerodynamic parts or making it streamline.