Mammoth CoT?

[GarrisonChisholm]

Good morning. I had a lifter that was causing too much 2nd stage Dv to be spent getting to orbit, so I copied the base 'Mammoth' stage and added 6 of them symmetrically, thinking I would then barely need any 2nd stage use to make orbit. However, now the rail-solid lift-off is gone, and the ship oscillates about its vertical access until stage burn-out, losing much of its thrust as it pronates back and forth through 50 degrees of vector on its way up. I have checked, and everything is symmetrical.

Noting that the Mammoth has 4 engines, does the game count that as 4 balanced centers of thrust, or does it compute only a single center of thrust for the stage? If the former is the case, then that must likely be the solution to this stability issue, as copying the staging and adding them as boosters cannot not create a balanced alignment of all the 4 engine stages.

Edited July 30, 2015 by GarrisonChisholm

[Feradose]

Calculates the thrust for four nozzles, and yes, its balanced.

[Red Iron Crown]

If you mounted the Mammoth stages radially I would give long odds that it is vessel flex that is causing your woes. Try adding some struts from the boosters to the core and see if it improves.

A pic of the rocket in question would be very helpful.

[A_name]

Maybe try disabling engine gimbal on the boosters.

[GarrisonChisholm]

If you mounted the Mammoth stages radially I would give long odds that it is vessel flex that is causing your woes. Try adding some struts from the boosters to the core and see if it improves.

A pic of the rocket in question would be very helpful.

Noted! I will try to provide one tomorrow.

[Randazzo]

Maybe try disabling engine gimbal on the boosters.

This.

You should probably still use struts with such massively heavy boosters though. And there will probably be fireworks when you try to drop the boosters.

[pincushionman]

I'm guessing your TWR went from "adequate" (1.2 to 1.7ish) to "excessively high" (>3.0) by adding the rhinoboosters to your first stage. Depends how big your upper stages are.

Excessive TWR = too fast too low in atmosphere = transsonic with too much drag = rocket flips!

Also, copying your first stage in 6X symmetry = moves CoM aft = rocket flips! Exacerbating above problem.

Pics would help immensely.

[GarrisonChisholm]

This.

You should probably still use struts with such massively heavy boosters though. And there will probably be fireworks when you try to drop the boosters.

Thank You Randazzo & A_name!

Locking gimbals corrected the issue. I did grab a screen shot, but have some wonky weirdness in my wifi and couldn't get it off my lap-top last night, but I ended up doing a complete tear-down afterwards and re-building the first stage piece by piece. It turns out that when I copied the stage and applied it x6 radially some of my fuel lines crossed and I had an uneven burn. The ship now lifts its cargo into space on the first stage alone, and if I can figure out how to fly it without losing it too-far over, maybe even into orbit.