Several Questions: roll, launch data, rocket mass, autopilot, subassemblies

[Comcain]

(I looked around for answers to these, and I struck out, so I'll ask here.)

1. My spacecraft has a slow, but annoying, roll, both on takeoff and in space. I can null the roll out with "q" and "e", but it just slowly comes back. I don't see anything that would be applying force. I keep thinking "roundoff errors" but that seems unlikely. (Is this a "barbecue roll"? A Gemini VIII stuck thruster? *grin*)

2. Is there a mod to gather launch data? For example, something that tells me each second, from launch, how many seconds from liftoff, total mass at that time, speed at that time, fuel left at that time? BONUS: Is there a mod that writes these numbers to disk? I see one, but this would be my first mod install, and I'm not sure I understand how to add a mod!

3. Is there an easy way to find out a rocket's mass? Sure, I can add up the mass numbers from the table of parts-masses, but is there a quick way? (I'm imagining something like CTRL-A to Select All, then select "Mass". You get the idea).

4. The "autopilot" isn't able to keep my rocket pointed straight up during launch. I have to manually correct it. I have to catch it fairly quickly or the rocket will "spin out". I have 8 KR-2L engines symmetrically around the center axis at the bottom, a stack of four S3-1440 (biggest) fuel tanks (two to feed first stage), then a single KR-2L as 2nd stage, then two more to feed 2nd stage, and then electricity/reactant/stabilizer, then the pod. Is this just the limit to what it'll handle?

5) I'm having a fair amount of trouble with subassemblies. I'm trying for a "stage zeroth" at the very bottom of the rocket. However, the central fuel tank I want to attach to doesn't have a "green bubble" to say it's attachable, and won't attach. Other things can attach to the center tank, but it is not interested in the central fuel tank for the stage zeroth.

I haven't locked the stages, I'm not in docking mode, I have a command pod, mouse isn't hovering over staging/editor, I'm not in time warp. I have plenty of electricity and reaction propellant.

I've tried deleting, re-downloading, and installing.

Many thanks! This is a lot of questions.

Thanks,

Dave

p.s. I'm unfamiliar with this forum software, and how to add a picture, or I would have; so far, no luck.

[Red Iron Crown]

1. My spacecraft has a slow, but annoying, roll, both on takeoff and in space. I can null the roll out with "q" and "e", but it just slowly comes back. I don't see anything that would be applying force. I keep thinking "roundoff errors" but that seems unlikely. (Is this a "barbecue roll"? A Gemini VIII stuck thruster? *grin*)

Asymmetric struts would be my guess, Necrobones did a great video describing the effect here.

2. Is there a mod to gather launch data? For example, something that tells me each second, from launch, how many seconds from liftoff, total mass at that time, speed at that time, fuel left at that time? BONUS: Is there a mod that writes these numbers to disk? I see one, but this would be my first mod install, and I'm not sure I understand how to add a mod!

MechJeb logs a lot of data during flight, Telemachus does so externally where it can be analyzed with external tools.

3. Is there an easy way to find out a rocket's mass? Sure, I can add up the mass numbers from the table of parts-masses, but is there a quick way? (I'm imagining something like CTRL-A to Select All, then select "Mass". You get the idea).

In stock you have to go to the launchpad, go to map mode, then open the info tab on the right. Mods such as the aforementioned MechJeb or Kerbal Engineer will calculate it in the VAB/SPH and in flight.

4. The "autopilot" isn't able to keep my rocket pointed straight up during launch. I have to manually correct it. I have to catch it fairly quickly or the rocket will "spin out". I have 8 KR-2L engines symmetrically around the center axis at the bottom, a stack of four S3-1440 (biggest) fuel tanks (two to feed first stage), then a single KR-2L as 2nd stage, then two more to feed 2nd stage, and then electricity/reactant/stabilizer, then the pod. Is this just the limit to what it'll handle?

You might not have enough control authority to control the rocket, more reaction wheels, and RCS system, or control surfaces (in atmosphere) would likely help.

5) I'm having a fair amount of trouble with subassemblies. I'm trying for a "stage zeroth" at the very bottom of the rocket. However, the central fuel tank I want to attach to doesn't have a "green bubble" to say it's attachable, and won't attach. Other things can attach to the center tank, but it is not interested in the central fuel tank for the stage zeroth.

The subassembly can only be attached by its root part. If you built the subassembly upwards from a command pod, it may not attach properly underneath something. You can either rebuild the subassembly or use something like the SelectRoot mod to change the root part (I found subassemblies frustrating before discovering this mod, now I use them all the time).

[capi3101]

p.s. I'm unfamiliar with this forum software, and how to add a picture, or I would have; so far, no luck.

The forums have been jacked up for quite some time now - the only way to post images is to use another site to host the image (if you don't have one of your own, an image-hosting site such as Imgur or Flickr works well; I use Imgur myself) and link to it with img tags ([ IMG ] put URL here [ / URL ], but take the spaces out of the brackets). Full Imgur albums have their own special tag ([ imgur ]) that you can just set the albums identifier between.

Red Iron Crown's pretty well answered your other issues, so I thought I'd take the easy one.

[StrandedonEarth]

What R.I.C. said, but also...

The VOID mod is also good for showing mass and part count in the VAB, along with other useful data. I especially like the Situation/Biome part of the VOID display.

To post pics you need to upload them somewhere else like imgur or other hosting sites and then paste the link into your post here. The nice thing about imgur is that it'll give you the code to paste into your post

To install a mod you simply need to unzip and then drop the contents in the GameData folder of your KSP install. Some mods have the GameData folder as part of the folder structure inside the .zip, make sure you only copy the stuff inside the GameData folder of the .zip

[Laie]

2. Is there a mod to gather launch data? For example, something that tells me each second, from launch, how many seconds from liftoff, total mass at that time, speed at that time, fuel left at that time? BONUS: Is there a mod that writes these numbers to disk?

IMO, the best flight data recorder is one you've written yourself in kerboscript; this requires the kOS Autopilot.

A simple flight data recorder script might look like this:

until altitude > 70000 {
  log missiontime +";"+ airspeed +";"+ altitude to mylog.
  copy mylog to archive.
  wait 1.
}

The good part is that kOS lets you collect any kind of data in whatever format you want; the bad part is that it might take hours of digging through the docs to get anything done at all.

Installing mods usually is nothing more than unpacking a zip file and dropping the contents into your gamedata folder. Each and every mod has a folder to itself, you needn't worry about accidentally overwriting important files.

[Pecan]

This is a huge rocket, bigger than anything I've launched for sure. If you aren't comfortable with the construction and controls you should really practice with something a lot smaller.

[Comcain]

Thank you all for your help! I really appreciate it... I'm off to look over the links you gave me...

Thanks again,

Dave

[Daveroski]

(I looked around for answers to these, and I struck out, so I'll ask here.)

1. My spacecraft has a slow, but annoying, roll, both on takeoff and in space. I can null the roll out with "q" and "e", but it just slowly comes back. I don't see anything that would be applying force. I keep thinking "roundoff errors" but that seems unlikely. (Is this a "barbecue roll"? A Gemini VIII stuck thruster? *grin*)

The most probable reason for this is the position of your SAS 'autopilot'

In General, it should be located as close to the pointy end as possible. Leading a bull by the nose is more affective than leading him by his shoulders.

In space, once orbit is achieved, I oft get a strange waywardness about the ship. It will roll or tumble, seemingly of it's own volition. I find that a second under warp often cancels this aberrant behaviour. I press the full-stop key once and then the comma key right after. Then all is calm again.

2. Is there a mod to gather launch data? For example, something that tells me each second, from launch, how many seconds from liftoff, total mass at that time, speed at that time, fuel left at that time? BONUS: Is there a mod that writes these numbers to disk? I see one, but this would be my first mod install, and I'm not sure I understand how to add a mod!

I suggest Mechjeb. You can use as much of it or as little as you wish. "It's only 'cheating' if you use it!"

I use it. Although I can perform every action that mechjeb can automate I have tried to play without it aboard and found that I miss the information screens too much. Customised and giving me all the information I want. Mundane and repetitive tasks which keep me in map view for too long such as circulising or changing the ap or pe.

When I want a challenge from a mission, I will fly the whole thing from the command pod and not use Mechjeb But I insist on a good window.

3. Is there an easy way to find out a rocket's mass? Sure, I can add up the mass numbers from the table of parts-masses, but is there a quick way? (I'm imagining something like CTRL-A to Select All, then select "Mass". You get the idea).

With Mechjeb, it's right there as you build along with as much data as you want such as Delta V

Otherwise you have to wait until you get to the launchpad and get the info for your ship from the little tab on the right of the screen.

4. The "autopilot" isn't able to keep my rocket pointed straight up during launch. I have to manually correct it. I have to catch it fairly quickly or the rocket will "spin out". I have 8 KR-2L engines symmetrically around the center axis at the bottom, a stack of four S3-1440 (biggest) fuel tanks (two to feed first stage), then a single KR-2L as 2nd stage, then two more to feed 2nd stage, and then electricity/reactant/stabilizer, then the pod. Is this just the limit to what it'll handle?

See my answer to your first question regaring the position of your SAS device.

5) I'm having a fair amount of trouble with subassemblies. I'm trying for a "stage zeroth" at the very bottom of the rocket. However, the central fuel tank I want to attach to doesn't have a "green bubble" to say it's attachable, and won't attach. Other things can attach to the center tank, but it is not interested in the central fuel tank for the stage zeroth.

I haven't locked the stages, I'm not in docking mode, I have a command pod, mouse isn't hovering over staging/editor, I'm not in time warp. I have plenty of electricity and reaction propellant.

I've tried deleting, re-downloading, and installing.

A simple tip with building sub-assemblies. Make the first item in your build, not a command pod but instead use a docking port and build as though this new vehicle was going to dock with another. You can grab the docking port and save the whole vehicle as a sub-assembly. When you wish to attach it to another vessel, do so using the docking port first. If you have no need of the port, place the addition onto your vessel anywhere it will attach and then remove the addition by grasping the part with which you mean to attach it. This parts node will become visible and attachment may proceed. You can then discard the unwanted docking port.

May only enough of your vessels explode to keep it interesting. ;o)