Launching asymmetrical rockets

[Lunar Sea]

Like, say, space station modules. Any tips? 

[Rodhern]

The only two points I can think of aren't tricks.

Point 1: Add sufficient control authority by sticking on fins, reaction wheels and such stuff, so that you can still control the craft. The extra fins and stuff can be attached to decouplers so that you may eject them when they have served their purpose.

Point 2: Accept that you have to invent a different ascent path than your 'usual' one. Find out (experimentally) what thrust settings, speeds, angles etc will make your ascent a success.

[Lunar Sea]

2 minutes ago, Rodhern said:

Point 1: Add sufficient control authority by sticking on fins, reaction wheels and such stuff, so that you can still control the craft. The extra fins and stuff can be attached to decouplers so that you may eject them when they have served their purpose.

Like what politicians do with their supporters? I'll try that out 

Srsly though yes I am having trouble launching this new thing. I at least got it weight balanced through the central axis, a minor feat in itself. But it has some abutments that are causing aerodynamic inversions. I'll throw up a pic in a few hours. 

[Superfluous J]

This assumes that you are capable of getting the payload into orbit, were it not for the fact that it's asymmetric:

1. Turn on the COM and COT markers. The buttons are in the lower left.
2. Attach your asymmetric payload to your rocket (assuming it's not attached already)
3. Turn on the translate button (or hit "2" which is its shortcut) and turn off angle snap (the hex button, make it a circle) by clicking or hitting "c".
4. Click the decoupler or fairing base or whatever is convenient and at the top of your rocket (but under the payload) to bring up the translation gizmo for that part.
5. Use the gizmo to slide the rocket around under the payload until the COM and COT markers line up.
6. (optional) Get frustrated with the stock display of these markers and install RCS Build Aid to further help you line things up.

Edited August 26, 2016 by 5thHorseman
Edited for clarity

[Rodhern]

9 minutes ago, 5thHorseman said:

• (optional) Get frustrated with the stock display of these markers and install RCS Build Aid to further help you line things up.

Speaking of lining things up. I think this mod is quite nice:

http://forum.kerbalspaceprogram.com/index.php?/topic/132775-11-113-hangar-grid-zero-deviation-v030-2016-apr-20/&page=1

 

[LN400]

Another way is to use a small engine, or two, like the Twitch on the "heavy" side of the rocket. Adjust the throttle cap on that to line up the CoT with CoM.

Edited August 26, 2016 by LN400

[Aegolius13]

Fairings are an option to help with uneven aerodynamic issues, though they won't help with weight balancing issues, of course.

But I usually pass on the fairings, since they can be heavy, expensive, and can cause issues of their own.

I agree RCS Build Aid is helpful for this too, thoughi t's a little confusing to read.  It will show you torque produced when you use your engine.  Then you can reposition the parts, your engine or both to get the torque number down.

[Superfluous J]

Note if your problems are asymmetric aerodynamics, one option is to break the "gravity turn" rule and launch straight up, at least for a bit. Maybe up to 10km or so. It's horribly inefficient but if it gets you to space, it gets you to space.

[Plusck]

I regularly send up butt-ugly, assymmetrical craft. Control authoity for thrust is generally not a problem and can be countered with RCS and reaction wheels. I usually end up having the module in the middle with a small orbital-maneuvres stage under it, and twin lifter stages on each side: not pretty but cheap and effective.

The real problem is generally aero forces at about the 8-12km phase, so I often have to fly steeper to start with and cut thrust to stop velocity increasing much above 200m/s before getting into thinner air. The dv hit to orbit is significant but, since it happens quite low down along the flighpath, can be cheaply compensated by adding a couple of cheap SRB+fuel drop tank combos.

[Lunar Sea]

Ok, I got it after a few tries - like y'all said pretty much just have to shoot straight up and avoid turning until a much higher altitude. No big deal. 

[Freds]

You can try this mod: Throttle Controlled Avionics. 

 

[Foxster]

On 26/08/2016 at 11:15 PM, Lunar Sea said:

Ok, I got it after a few tries - like y'all said pretty much just have to shoot straight up and avoid turning until a much higher altitude. No big deal. 

Ah, well done.

Was going to suggest trying a lifter with Vector engines. Their enormous gimbal helps with off-centre craft like shuttles. 

[GoSlash27]

 For asymmetric rockets, the most important thing is to know where your center of mass is and where it moves to as the fuel drains. The engines need to be aligned so that the thrust runs through the Com and the tanks need to drain in an order that keeps the CoM in line with the thrust. If you can do that, you can make wildly crooked lifters that still fly more-or-less normally.
 The one thing to watch out for is gimbaling; vectoring the engines in yaw produces a roll.

Spoiler

 

Best,
-Slashy

[Palaceviking]

I vaguely remember a spacebar only to orbit challenge,  whereby you only used the staging to make orbit which  required an asymmetrical design. 

Now if I've got sticky-out bits on my rockets I just make sure they're facing east